全文获取类型
收费全文 | 8533篇 |
免费 | 91篇 |
专业分类
管理学 | 1470篇 |
民族学 | 55篇 |
人口学 | 793篇 |
丛书文集 | 29篇 |
理论方法论 | 615篇 |
综合类 | 110篇 |
社会学 | 3521篇 |
统计学 | 2031篇 |
出版年
2021年 | 45篇 |
2020年 | 135篇 |
2019年 | 171篇 |
2018年 | 227篇 |
2017年 | 280篇 |
2016年 | 203篇 |
2015年 | 140篇 |
2014年 | 220篇 |
2013年 | 1358篇 |
2012年 | 284篇 |
2011年 | 290篇 |
2010年 | 196篇 |
2009年 | 181篇 |
2008年 | 180篇 |
2007年 | 202篇 |
2006年 | 186篇 |
2005年 | 164篇 |
2004年 | 208篇 |
2003年 | 147篇 |
2002年 | 173篇 |
2001年 | 202篇 |
2000年 | 191篇 |
1999年 | 177篇 |
1998年 | 136篇 |
1997年 | 128篇 |
1996年 | 130篇 |
1995年 | 107篇 |
1994年 | 107篇 |
1993年 | 100篇 |
1992年 | 145篇 |
1991年 | 125篇 |
1990年 | 118篇 |
1989年 | 113篇 |
1988年 | 97篇 |
1987年 | 91篇 |
1986年 | 97篇 |
1985年 | 111篇 |
1984年 | 115篇 |
1983年 | 127篇 |
1982年 | 99篇 |
1981年 | 89篇 |
1980年 | 85篇 |
1979年 | 94篇 |
1978年 | 92篇 |
1977年 | 81篇 |
1976年 | 70篇 |
1975年 | 68篇 |
1974年 | 59篇 |
1973年 | 62篇 |
1971年 | 50篇 |
排序方式: 共有8624条查询结果,搜索用时 31 毫秒
941.
942.
The concept of exposure is central to chemical risk assessment and plays an important role in communicating to the public about the potential health risks of chemicals. Research on chemical risk perception has found some indication that the model lay people use to judge chemical exposure differs from that of toxicologists, thereby leading to different conclusions about chemical safety. This paper presents the results of a series of studies directed toward developing a model for understanding how lay people interpret the concept of chemical exposure. The results indicate that people's beliefs about chemical exposure (and its risks) are based on two broad categories of inferences. One category of inferences relates to the nature in which contact with a chemical has taken place, including the amount of a chemical involved and its potential health consequences. A second category of inferences about chemical exposure relates to the pragmatics of language interpretation, leading to beliefs about the motives and purposes behind chemical risk communication. Risk communicators are encouraged to consider how alternative models of exposure and language interpretation can lead to conflicting conclusions on the part of the public about chemical safety. 相似文献
943.
G Hirsch 《Physician executive》1999,25(2):30-35
Burnout is a state of physical, emotional, and mental exhaustion caused by long-term involvement in situations that are emotionally demanding. It is not stress, per se, that causes burnout, as many thrive in stressful, demanding careers. Rather, burnout results when stress continuously outweighs the sense of effectiveness, accomplishment, and reward. And, this fate is sealed when one feels helpless to effect significant change in the conditions that fuel the stress. Establishing an organizational environment that reduces the risk of physician burnout requires a new commitment of resources, one that can be challenging to justify to decision-makers with a strictly short-term, bottom line orientation. The key issues to consider in shaping a physician career management program include: (1) entry of new physician employees into the organization; (2) productivity measures; (3) responsiveness to safety concerns; (4) administrative and policy issues; and (5) variety and growth opportunities. 相似文献
944.
Ned Calonge Paul G. Shekelle Douglas K. Owens Steven Teutsch Autumn Downey Lisa Brown Jane Noyes 《Research Synthesis Methods》2023,14(1):36-51
Despite research investment and a growing body of diverse evidence there has been no comprehensive review and grading of evidence for public health emergency preparedness and response practices comparable to those in medicine and other public health fields. The National Academies of Sciences, Engineering, and Medicine convened an ad hoc committee to develop and use methods for grading and synthesizing diverse types of evidence to create a single certainty of intervention-related evidence to support recommendations for Public Health Emergency Preparedness and Response Research. A 13-step consensus building method was used. Experts were first canvassed in public meetings, and a comprehensive review of existing methods was undertaken. Although aspects of existing review methodologies and evidence grading systems were relevant, none adequately covered all requirements for this specific context. Starting with a desire to synthesize diverse sources of evidence not usually included in systematic reviews and using GRADE for assessing certainty and confidence in quantitative and qualitative evidence as the foundation, we developed a mixed-methods synthesis review and grading methodology that drew on (and in some cases adapted) those elements of existing frameworks and methods that were most applicable. Four topics were selected as test cases. The process was operationalized with a suite of method-specific reviews of diverse evidence types for each topic. Further consensus building was undertaken through stakeholder engagement and feedback The NASEM committee's GRADE adaption for mixed-methods reviews will further evolve over time and has yet to be endorsed by the GRADE working group. 相似文献
945.
Lucas G. Gago Galvagno Stephanie E. Miller Carolina De Grandis Angel M. Elgier 《Infancy》2021,26(6):962-979
Recent work within early executive function (EF) seems to suggest that toddlers show distinct patterns of development, involving poorly correlated performance across EF tasks and significant improvements over relatively short periods of time. The present study sought to extend these findings by investigating evidence for these patterns in toddlers and the existence of more traditional patterns of EF (e.g., correlations between tasks, links to language) when using the same tasks in a novel Latin American sample. Eighty toddlers (18–24 months) and sixty young preschoolers (30–36) months completed a battery of EF tasks, early social communication, and receptive and expressive language measures. Results indicated that toddlers showed similar distinct patterns of development (i.e., few relations between tasks and links to responding to joint attention), but by early preschool a more cohesive EF and links to language were present. Further, work demonstrated significant age (older children outperformed younger children), gender (girls outperformed boys), and socioeconomic differences (satisfied basic needs outperformed unsatisfied basic needs, but only on the snack delay). This work provides evidence for patterns of emerging EF development within this novel cultural sample (and evidence for group differences) that may be supported by communicative and representational development. 相似文献
946.
Extreme learning machine (ELM) has attracted attentions in pattern classification problems due to its preferences in low computations and high generalization. To overcome its drawbacks, caused by the randomness of input weights and biases, the ensemble of ELMs was proposed. The diversity of ELMs forming the ensemble was studied broadly in the literature, via using different activation functions and/or different number of hidden neurons. However, less attention was paid to aggregation mechanism in ensemble of ELMs. To speed up this aggregation process, we propose an ensemble framework for ELMs, called extreme ensemble of ELMs (EEoELMs) because of its extreme speed in ensemble process. In this framework, the input weights of each ELM are randomly pre-assigned as usual. The ELMs make use of the same/distinct activation functions to increase the diversity of classifiers and so the generalization of ensemble. The output weights of each ELM are set using Moore–Penrose inverse method. However, the aggregation mechanism in EEoELM is novel. Instead of using majority/weighted voting on the prediction results of ELMs, their output neurons are combined in a new decision/ensemble layer. The output of this layer determines the ensemble output. As the weights of this decision layer are also computed using Moore–Penrose inverse method, the ensemble is extremely fast. Experimental results on synthetic and real-world datasets indicate the acceptable classification performance of EEoELM in much less computational efforts. 相似文献
947.
Yağmur Uysal;Zeynep Görkem Doğaroğlu;Zehranur Çaylali;Delil Sefkan Karakulak; 《Global Challenges》2024,8(11):2400120
In this study, the impact of zinc oxide nanoparticles (ZnO-NPs) generated using rosemary extract, synthesized using environmentally friendly processes and integrated into a cross-linked polymer matrix, on growth performance of wheat is evaluated. Rosemary extract used as coating, stabilizing, and reducing agents in this green synthesis method. Fourier transform infrared spectroscopy analyses demonstrated the presence of phytochemical constituents of the plant extract that served as capping agents during the synthesis process. The nanoparticles are sprayed to the plant leaves. The effects of nanoparticles within the hydrogel on plant development are compared with the effects of nanoparticles in suspension. The percentage of seed germination is unaffected by either rosemary- or raw-ZnO-NPs; however, the root and shoot elongation are considerably impacted by the nanoparticle treatments. The threshold concentrations are determined as 3000 mg L−1 for rosemary-ZnO-NPs and 2000 mg L−1 for raw-ZnO-NPs. Additionally, antibacterial test results showed that the activity level on Escherichia coli is higher for rosemary-ZnO-NPs compared to raw-ZnO-NPs. The results of this research may provide guidance on how green synthesis methods and the use of nanoparticle-hydrogel composites in plant breeding can be used in future agricultural applications. This can be considered an important step in terms of agricultural innovations and sustainability. 相似文献
948.
L. E. Heeger;N. A. M. Houben;C. Caram-Deelder;S. F. Fustolo-Gunnink;J. G. van der Bom;E. Lopriore; 《Alcoholism & Drug Abuse Weekly》2024,64(8):1421-1427
Evidence supports a restrictive platelet transfusion threshold in preterm neonates. We aimed to describe the effect of implementing this threshold on transfusion rates. 相似文献
949.
Michael D. Orr;Brian G. Casleton;Olivia R. Garcia; 《Alcoholism & Drug Abuse Weekly》2024,64(10):1993-2000
The popularity of Low-Titer O Whole Blood (LTOWB) for treating trauma patients requires that donor centers and transfusion services make decisions on what titer testing capabilities to institute and an appropriate titer level threshold. This study compared the titer results determined by four methods to find a rate of agreement. 相似文献
950.
Jarron M. Saint Onge Richard G. Rogers Patrick M. Krueger 《Social science quarterly》2008,89(3):817-830
Objective. We examine the importance of anthropometric and performance measures, and age, period, and cohort effects in explaining life expectancies among major league baseball (MLB) players over the past century. Methods. We use discrete time hazard models to calculate life tables with covariates with data from Total Baseball, a rich source of information on all players who played in the major league. Results. Compared to 20‐year‐old U.S. males, MLB players can expect almost five additional years of life. Height, weight, handedness, and player ratings are unassociated with the risk of death in this population of highly active and successful adults. Career length is inversely associated with the risk of death, likely because those who play longer gain additional incomes, physical fitness, and training. Conclusions. Our results indicate improvements in life expectancies with time for all age groups and indicate possible improvements in longevity in the general U.S. population. 相似文献