全文获取类型
收费全文 | 12780篇 |
免费 | 213篇 |
专业分类
管理学 | 1647篇 |
民族学 | 51篇 |
人才学 | 1篇 |
人口学 | 1099篇 |
丛书文集 | 79篇 |
教育普及 | 2篇 |
理论方法论 | 1183篇 |
综合类 | 339篇 |
社会学 | 6374篇 |
统计学 | 2218篇 |
出版年
2021年 | 67篇 |
2020年 | 189篇 |
2019年 | 220篇 |
2018年 | 244篇 |
2017年 | 365篇 |
2016年 | 282篇 |
2015年 | 228篇 |
2014年 | 254篇 |
2013年 | 2051篇 |
2012年 | 394篇 |
2011年 | 321篇 |
2010年 | 212篇 |
2009年 | 234篇 |
2008年 | 262篇 |
2007年 | 278篇 |
2006年 | 216篇 |
2005年 | 350篇 |
2004年 | 296篇 |
2003年 | 257篇 |
2002年 | 268篇 |
2001年 | 314篇 |
2000年 | 298篇 |
1999年 | 310篇 |
1998年 | 210篇 |
1997年 | 205篇 |
1996年 | 216篇 |
1995年 | 189篇 |
1994年 | 206篇 |
1993年 | 178篇 |
1992年 | 239篇 |
1991年 | 234篇 |
1990年 | 213篇 |
1989年 | 221篇 |
1988年 | 196篇 |
1987年 | 186篇 |
1986年 | 189篇 |
1985年 | 177篇 |
1984年 | 210篇 |
1983年 | 200篇 |
1982年 | 168篇 |
1981年 | 138篇 |
1980年 | 139篇 |
1979年 | 168篇 |
1978年 | 137篇 |
1977年 | 120篇 |
1976年 | 102篇 |
1975年 | 104篇 |
1974年 | 95篇 |
1973年 | 94篇 |
1971年 | 64篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
281.
We conducted a field study to investigate positive intergroup attitudes (i.e., allophilia) and equality values as potential antecedents of social policy support for multiracial individuals. Participants (N = 97) reported their social policy support for multiracial individuals in two ways—support for the recognition of "multiracial" as a distinct racial category (recognition) and support for multiracial individuals' access to programs and policies (assistance). Results revealed that allophilia motivated those who held equality beliefs to support social policies for multiracial individuals. Implications of these findings for theories of positive intergroup relations, as well as the processes that may underlie progress for multiracial individuals, are discussed. 相似文献
282.
Economists have long conceptualized and modeled the inherent interdependent relationships among different sectors of the economy. This concept paved the way for input-output modeling, a methodology that accounts for sector interdependencies governing the magnitude and extent of ripple effects due to changes in the economic structure of a region or nation. Recent extensions to input-output modeling have enhanced the model's capabilities to account for the impact of an economic perturbation; two such examples are the inoperability input-output model( 1 , 2 ) and the dynamic inoperability input-output model (DIIM).( 3 ) These models introduced sector inoperability, or the inability to satisfy as-planned production levels, into input-output modeling. While these models provide insights for understanding the impacts of inoperability, there are several aspects of the current formulation that do not account for complexities associated with certain disasters, such as a pandemic. This article proposes further enhancements to the DIIM to account for economic productivity losses resulting primarily from workforce disruptions. A pandemic is a unique disaster because the majority of its direct impacts are workforce related. The article develops a modeling framework to account for workforce inoperability and recovery factors. The proposed workforce-explicit enhancements to the DIIM are demonstrated in a case study to simulate a pandemic scenario in the Commonwealth of Virginia. 相似文献
283.
Nolan A. Wages Alexia Iasonos John O'Quigley Mark R. Conaway 《Pharmaceutical statistics》2020,19(2):137-144
This paper studies the notion of coherence in interval‐based dose‐finding methods. An incoherent decision is either (a) a recommendation to escalate the dose following an observed dose‐limiting toxicity or (b) a recommendation to deescalate the dose following a non–dose‐limiting toxicity. In a simulated example, we illustrate that the Bayesian optimal interval method and the Keyboard method are not coherent. We generated dose‐limiting toxicity outcomes under an assumed set of true probabilities for a trial of n=36 patients in cohorts of size 1, and we counted the number of incoherent dosing decisions that were made throughout this simulated trial. Each of the methods studied resulted in 13/36 (36%) incoherent decisions in the simulated trial. Additionally, for two different target dose‐limiting toxicity rates, 20% and 30%, and a sample size of n=30 patients, we randomly generated 100 dose‐toxicity curves and tabulated the number of incoherent decisions made by each method in 1000 simulated trials under each curve. For each method studied, the probability of incurring at least one incoherent decision during the conduct of a single trial is greater than 75%. Coherency is an important principle in the conduct of dose‐finding trials. Interval‐based methods violate this principle for cohorts of size 1 and require additional modifications to overcome this shortcoming. Researchers need to take a closer look at the dose assignment behavior of interval‐based methods when using them to plan dose‐finding studies. 相似文献
284.
Tree algorithms are a well-known class of random access algorithms with a provable maximum stable throughput under the infinite population model (as opposed to ALOHA or the binary exponential backoff algorithm). In this article, we propose a tree algorithm for opportunistic spectrum usage in cognitive radio networks. A channel in such a network is shared among so-called primary and secondary users, where the secondary users are allowed to use the channel only if there is no primary user activity. The tree algorithm designed in this article can be used by the secondary users to share the channel capacity left by the primary users.
We analyze the maximum stable throughput and mean packet delay of the secondary users by developing a tree structured Quasi-Birth Death Markov chain under the assumption that the primary user activity can be modeled by means of a finite state Markov chain and that packets lengths follow a discrete phase-type distribution.
Numerical experiments provide insight on the effect of various system parameters and indicate that the proposed algorithm is able to make good use of the bandwidth left by the primary users. 相似文献
285.
Shaun R. Seaman Daniel Farewell Ian R. White 《Scandinavian Journal of Statistics》2016,43(4):996-1018
Linear increments (LI) are used to analyse repeated outcome data with missing values. Previously, two LI methods have been proposed, one allowing non‐monotone missingness but not independent measurement error and one allowing independent measurement error but only monotone missingness. In both, it was suggested that the expected increment could depend on current outcome. We show that LI can allow non‐monotone missingness and either independent measurement error of unknown variance or dependence of expected increment on current outcome but not both. A popular alternative to LI is a multivariate normal model ignoring the missingness pattern. This gives consistent estimation when data are normally distributed and missing at random (MAR). We clarify the relation between MAR and the assumptions of LI and show that for continuous outcomes multivariate normal estimators are also consistent under (non‐MAR and non‐normal) assumptions not much stronger than those of LI. Moreover, when missingness is non‐monotone, they are typically more efficient. 相似文献
286.
This article investigates the choice of working covariance structures in the analysis of spatially correlated observations motivated by cardiac imaging data. Through Monte Carlo simulations, we found that the choice of covariance structure affects the efficiency of the estimator and power of the test. Choosing the popular unstructured working covariance structure results in an over-inflated Type I error possibly due to a sample size not large enough relative to the number of parameters being estimated. With regard to model fit indices, Bayesian Information Criterion outperforms Akaike Information Criterion in choosing the correct covariance structure used to generate data. 相似文献
287.
288.
Rapid changes in China over the past two decades have led to significant problems associated with population migration and changing social attitudes, including a growing sex industry and concurrent increases in STIs and HIV. This article reports results of an exploratory study of microbicide acceptability and readiness and current HIV prevention efforts among female sex workers in two rural and one urban town in Hainan and Guangxi Provinces in southern China. The study focused on these women's knowledge and cultural understandings of options for protecting themselves from exposure to STIs and HIV, and the potential viability and acceptability of woman-initiated prevention methods. We report on ethnographic elicitation interviews conducted with women working within informal sex-work establishments (hotels, massage and beauty parlors, roadside restaurants, boarding houses). We discuss implications of these findings for further promotion of woman-initiated prevention methods such as microbicides and female condoms among female sex workers in China. 相似文献
289.
Three studies explored gender differences in explicit and implicit components of sexual arousal following brief exposure to a sexual stimulus. Whereas Study 1 assessed reports of sexual arousal following subliminal exposure to a sexual or a neutral picture, Studies 2 and 3 examined the effects of the same priming procedure on accessibility of sex-related thoughts assessed with a pictorial judgment task and a lexical decision task. The subliminal sexual prime did not have an effect on men's reports of sexual arousal, but caused women to report lower levels of sexual arousal. In contrast, the same subliminal sexual prime led to higher accessibility of sex-related thoughts in both men and women. It is therefore suggested that the subliminal sexual prime causes women to activate sex-related mental contents but to experience the result as somewhat aversive. 相似文献
290.
There has been no research linking implementation of a public smoking ban and reduced incidence of acute myocardial infarction (AMI) among nonsmoking patients. An ex post facto matched control group study was conducted to determine whether there was a change in hospital admissions for AMI among nonsmoking patients after a public smoking ban was implemented in Monroe County compared with Delaware County, Indiana without such a ban. Poisson analysis was conducted for 44 months of hospital admissions. A significant drop occurred in the number of admissions among nonsmoking patients in Monroe County after the ban whereas a nonsignificant decrease in the number of admissions occurred in Delaware County. The changes in the number of smoking-patient admissions before and after the ban were not significant. 相似文献