全文获取类型
收费全文 | 9087篇 |
免费 | 257篇 |
国内免费 | 1篇 |
专业分类
管理学 | 1276篇 |
民族学 | 55篇 |
人口学 | 772篇 |
丛书文集 | 29篇 |
理论方法论 | 853篇 |
综合类 | 85篇 |
社会学 | 4030篇 |
统计学 | 2245篇 |
出版年
2023年 | 53篇 |
2022年 | 34篇 |
2021年 | 66篇 |
2020年 | 164篇 |
2019年 | 244篇 |
2018年 | 267篇 |
2017年 | 357篇 |
2016年 | 254篇 |
2015年 | 168篇 |
2014年 | 275篇 |
2013年 | 1716篇 |
2012年 | 282篇 |
2011年 | 285篇 |
2010年 | 231篇 |
2009年 | 219篇 |
2008年 | 237篇 |
2007年 | 227篇 |
2006年 | 243篇 |
2005年 | 222篇 |
2004年 | 193篇 |
2003年 | 167篇 |
2002年 | 205篇 |
2001年 | 235篇 |
2000年 | 222篇 |
1999年 | 215篇 |
1998年 | 155篇 |
1997年 | 150篇 |
1996年 | 121篇 |
1995年 | 107篇 |
1994年 | 151篇 |
1993年 | 113篇 |
1992年 | 133篇 |
1991年 | 139篇 |
1990年 | 124篇 |
1989年 | 116篇 |
1988年 | 96篇 |
1987年 | 97篇 |
1986年 | 95篇 |
1985年 | 96篇 |
1984年 | 99篇 |
1983年 | 75篇 |
1982年 | 73篇 |
1981年 | 56篇 |
1980年 | 68篇 |
1979年 | 66篇 |
1978年 | 55篇 |
1977年 | 53篇 |
1976年 | 44篇 |
1975年 | 50篇 |
1974年 | 42篇 |
排序方式: 共有9345条查询结果,搜索用时 15 毫秒
181.
Andrew C. Kitchener 《The Senses and Society》2017,12(3):333-343
As one of a suite of natural science galleries in the National Museum of Scotland, Animal Senses presents a comprehensive overview of how animals have evolved senses as they have adapted to different ecological niches in order to find food or avoid predation. Using different sensory channels, they also have evolved means of communication to attract mates, deter rivals, and remain hidden from predators and prey. Some of the most extraordinary examples of evolution are those which mimic the appearance of another unrelated species or some feature of the environment such as a thorn on a bush or a piece of coral. New taxidermy and models, engaging text presented hierarchically, and fun interactives were developed specifically for this gallery in order to present an up-to-date review of senses and communication. However, its real strength is the wide array of real specimens and life-size models which allow visitors to see what these animals really look like and how big they are, experiences which cannot be emulated by books or electronic media. By taking a thematic approach, we have created an unrivalled opportunity to compare animals from different taxonomic groups to see how they have solved the problems of life by evolving similar structures or completely different ones in order to find food, avoid being eaten, navigate, find mates and deceive rivals and predators. 相似文献
182.
In this paper the relationships between a disruption in parental co-habitation and various categories of adolescent outcomes over multiple time horizons are explored. Using data from the National Longitudinal Study of Adolescent Health (Add Health), we estimated the effects of a change from living with both parents to just one, on academic and employment outcomes, the likelihood to indulge in risky behaviors, mental health outcomes and body mass index measures, from less than 1 year to over 14 years after the change. Propensity score matching methods were used to control for individual characteristics and pre-existing differences in the family environment that may increase the chances of separation, and the results are compared to those obtained using ordinary least squares or probit methods. Results showed evidence of adverse effects of living with one parent in the short term, medium term and long term. Adolescents living with one parent had lower academic achievement in all term lengths, poor mental health in the short to medium term, and were more likely to engage in risky behaviors in the medium to long term. 相似文献
183.
The depths, which have been used to detect outliers or to extract a representative subset, can be applied to classification. We propose a resampling-based classification method based on the fact that resampling techniques yield a consistent estimator of the distribution of a statistic. The performance of this method was evaluated with eight contaminated models in terms of Correct Classification Rates (CCRs), and the results were compared with other known methods. The proposed method consistently showed higher average CCRs and 4% higher CCR at the maximum compared to other methods. In addition, this method was applied to Berkeley data. The average CCRs were between 0.79 and 0.85. 相似文献
184.
185.
Toxicologists and pharmacologists often describe toxicity of a chemical using parameters of a nonlinear regression model. Thus estimation of parameters of a nonlinear regression model is an important problem. The estimates of the parameters and their uncertainty estimates depend upon the underlying error variance structure in the model. Typically, a priori the researcher would not know if the error variances are homoscedastic (i.e., constant across dose) or if they are heteroscedastic (i.e., the variance is a function of dose). Motivated by this concern, in this paper we introduce an estimation procedure based on preliminary test which selects an appropriate estimation procedure accounting for the underlying error variance structure. Since outliers and influential observations are common in toxicological data, the proposed methodology uses M-estimators. The asymptotic properties of the preliminary test estimator are investigated; in particular its asymptotic covariance matrix is derived. The performance of the proposed estimator is compared with several standard estimators using simulation studies. The proposed methodology is also illustrated using a data set obtained from the National Toxicology Program. 相似文献
186.
187.
Quantifying the Establishment Likelihood of Invasive Alien Species Introductions Through Ports with Application to Honeybees in Australia
下载免费PDF全文
![点击此处可从《Risk analysis》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The cost of an uncontrolled incursion of invasive alien species (IAS) arising from undetected entry through ports can be substantial, and knowledge of port‐specific risks is needed to help allocate limited surveillance resources. Quantifying the establishment likelihood of such an incursion requires quantifying the ability of a species to enter, establish, and spread. Estimation of the approach rate of IAS into ports provides a measure of likelihood of entry. Data on the approach rate of IAS are typically sparse, and the combinations of risk factors relating to country of origin and port of arrival diverse. This presents challenges to making formal statistical inference on establishment likelihood. Here we demonstrate how these challenges can be overcome with judicious use of mixed‐effects models when estimating the incursion likelihood into Australia of the European (Apis mellifera) and Asian (A. cerana) honeybees, along with the invasive parasites of biosecurity concern they host (e.g., Varroa destructor). Our results demonstrate how skewed the establishment likelihood is, with one‐tenth of the ports accounting for 80% or more of the likelihood for both species. These results have been utilized by biosecurity agencies in the allocation of resources to the surveillance of maritime ports. 相似文献
188.
Caroline K. Pemberton Roben Anneliese J. Bass Ginger A. Moore Laura Murray‐Kolb Patricia Z. Tan Rick O. Gilmore Kristin A. Buss Pamela M. Cole Laureen O. Teti 《Infancy》2012,17(5):558-577
Infants’ emerging ability to move independently by crawling is associated with changes in multiple domains, including an increase in expressions of anger in situations that block infants’ goals, but it is unknown whether increased anger is specifically because of experience with being able to move autonomously or simply related to age. To examine the influence of locomotion on developmental change in anger, infants’ (N = 20) anger expressions during an arm restraint procedure were observed longitudinally at a precrawling baseline assessment and 2 and 6 weeks after the onset of crawling. Infant age at each crawling stage was unrelated to the frequency of anger expressed in response to arm restraint. At 6 weeks postcrawling onset, infants whose mothers rated them as temperamentally higher in distress to limitations, compared with those rated lower, showed a greater increase in the frequency of anger expressed during the arm restraint relative to earlier assessments and took longer to reduce the frequency of anger expressed when no longer restrained. Findings suggest that experience with autonomous crawling has an effect on anger expression, independent of age, and that a temperamental tendency to become distressed by limitations may exacerbate the effect of crawling on anger expression. 相似文献
189.
Heather T. Rowan‐Kenyon Amy K. Swan Marie F. Creager 《The Career development quarterly》2012,60(1):2-15
The authors examined the central hypothesis that students’ early perceptions of support and sense of engagement in math classes and math activities strongly influence the broadening or narrowing of their math interest. The focus was on the first wave of qualitative data collected from 5th‐, 7th‐, and 9th‐grade students during the 2007–2008 academic year as part of a longitudinal study. Findings indicate the importance of using group work and extrinsic motivation in middle school math classes to broaden interest; peer classroom behavior was often a detractor of math interest. 相似文献
190.