全文获取类型
收费全文 | 8045篇 |
免费 | 204篇 |
专业分类
各国政治 | 421篇 |
工人农民 | 230篇 |
世界政治 | 515篇 |
外交国际关系 | 315篇 |
法律 | 4969篇 |
中国共产党 | 1篇 |
中国政治 | 22篇 |
政治理论 | 1678篇 |
综合类 | 98篇 |
出版年
2020年 | 75篇 |
2019年 | 94篇 |
2018年 | 141篇 |
2017年 | 156篇 |
2016年 | 181篇 |
2015年 | 125篇 |
2014年 | 156篇 |
2013年 | 888篇 |
2012年 | 229篇 |
2011年 | 216篇 |
2010年 | 170篇 |
2009年 | 185篇 |
2008年 | 219篇 |
2007年 | 210篇 |
2006年 | 202篇 |
2005年 | 160篇 |
2004年 | 176篇 |
2003年 | 180篇 |
2002年 | 182篇 |
2001年 | 314篇 |
2000年 | 298篇 |
1999年 | 233篇 |
1998年 | 90篇 |
1997年 | 112篇 |
1996年 | 87篇 |
1995年 | 91篇 |
1994年 | 98篇 |
1993年 | 91篇 |
1992年 | 169篇 |
1991年 | 187篇 |
1990年 | 172篇 |
1989年 | 177篇 |
1988年 | 162篇 |
1987年 | 152篇 |
1986年 | 176篇 |
1985年 | 141篇 |
1984年 | 133篇 |
1983年 | 146篇 |
1982年 | 84篇 |
1981年 | 80篇 |
1980年 | 64篇 |
1979年 | 117篇 |
1978年 | 72篇 |
1977年 | 65篇 |
1976年 | 61篇 |
1975年 | 71篇 |
1974年 | 83篇 |
1973年 | 79篇 |
1972年 | 67篇 |
1971年 | 60篇 |
排序方式: 共有8249条查询结果,搜索用时 31 毫秒
21.
22.
The effect of various stain carriers on the quality and quantity of DNA extracted from dried bloodstains 总被引:1,自引:0,他引:1
Bloodstains were made with 200 microliters blood on each of 11 different common substrates to examine the effect of the stain carrier on the amount and quality of DNA recoverable. High-molecular-weight DNA was extracted from all samples after 2 days. The yield of DNA from each sample varied considerably, not only between the different stain carriers but also within a given category. With a DNA yield of up to 10 micrograms, paper, glass, nylon, wood, smooth leather and wool gave the best results, followed by blue denim and wallpaper (up to 6 micrograms), cotton fabric and carpeting (up to 4 micrograms) and suede (up to 2 micrograms). For several stain carriers the DNA-containing solution was contaminated by chemical substances, which in the case of the blue denim, suede, and carpet samples inhibited the digestion of the DNA with restriction enzymes and prevented DNA typing. The different textures of the stain carriers tested and (as for varying yields on the same carrier) the differing degree of loss of DNA during extraction and the physiological variation in the number of leukocytes in human blood are discussed as possible reasons for the wide range of variation in the amounts of DNA it was possible to extract. 相似文献
23.
Rebecca Emerson Stephen G. Hall Anna Zalewska-Mitura 《Economic Change and Restructuring》1997,30(2-3):75-90
With new technically advanced methods and computers at our disposal, the efficient market hypothesis is once again being debated. At the same time, we are witnessing an unprecedented growth in both existing and new financial markets. These new markets are often in economies which have just recently embraced free market economics; we term these stock markets infant markets. Such stock markets are obviously not efficient in allocating the supply of savings to productive capital. We do not test whether or not these infant markets are informationally efficient, but instead examine whether and how they are becoming more efficient. We propose modelling the excess returns of individual securities using a multi-factor model with time-varying coefficients and generalised auto-regressive conditional heteroskedastic (GARCH) errors. If the markets are becoming more informationally efficient or the agents are learning, we would expect this to manifest itself as the time-varying coefficients becoming more stable as time increases. We test our model using data on four Bulgarian shares. First, we estimate an AR(2) model and a GARCH-M(1,1) model for the shares. Then, we estimated our AR(2) model with time varying coefficients and GARCH type errors. We find varying levels of efficiency and varying speeds of movement towards efficiency within our sample of four shares. 相似文献
24.
25.
26.
The Tax Reform Act of 1986 rewrote the federal income tax code, bringing it closer to policy professionals' vision of what constitutes an equitable and efficient income tax. Research on tax compliance suggests the law might have affected taxpayer compliance in three ways: by reducing opportunities to overstate deductions, by changing perceptions of fairness, and by altering tax liabilities. Changes in taxpayer perceptions, attitudes, and noncompliance intentions were examined in three bodies of survey data, each containing pre-and post-reform data from independent samples of the same population. The results show an improved normative climate for taxpayer compliance and point to both the feasibility and the importance of examining the effects of substantive tax policies on taxpayer perceptions, attitudes, and behavioral intentions. 相似文献
27.
Many abused women use professional and community services and begin to talk to professionals about the abuse they have endured. This article presents and discusses results of a study of 270 abused women who used the services of professionals and service agencies. The article presents information on the frequency of contact and the perceived helpfulness of different professions. Also presented are the types of responses which were considered to be useful and ineffective. This study revealed that the most frequently contacted professions were not necessarily perceived to be the most helpful. Further, certain responses of the service providers were more frequently reported to have value. 相似文献
28.
The formation of adequate mental health systems within prisons has accelerated as a result of successful class action lawsuits. Our recent national survey questioned all state correctional departments about the existence of standards in each system, compliance with such standards, prevalence of class action lawsuits involving the issue of providing adequate mental health services for inmates, issues related to consent decrees, available mental health resources within the correctional system, and the administrative structure of the mental health system. Our purpose was to identify those factors correlated with certified class action lawsuits involving issues related to mental health services. Twenty-one states were involved in such litigation. Only the presence of psychiatric hospitals operated by the department of corrections correlated with the presence of certified class action lawsuits involving mental health services. Prison systems larger than 15,000 inmates were at higher risk for such litigation. Smaller systems having psychiatric hospitals run by the state mental health agency appeared to be at less risk for such litigation. 相似文献
29.
W D Haglund D G Reichert D T Reay 《The American journal of forensic medicine and pathology》1990,11(1):35-43
The Green River Murder Investigation in King County, Washington, is currently the longest active serial murder investigation in U.S. history. During its course, over 26 separate scenes with from one to five victims each have been processed. The experience of the authors is presented in order to acquaint other agencies with techniques of outdoor scene processing that have evolved during recovery of remains from Green River and other skeletal cases. 相似文献
30.
Jill S. Cannon Alison Jacknowitz Gary Painter 《Journal of policy analysis and management》2006,25(2):299-321
Kindergarten policy varies widely both across and within states. Over the past decade, a number of states have instituted a full‐day kindergarten requirement and others are considering it as a way to increase educational achievement. Many parents also support full‐day kindergarten as a source of child care. This paper uses the Early Child Longitudinal Study–Kindergarten Class of 1998–1999 to evaluate the efficacy of this policy. In ordinary least squares, probit, county fixed effects, and instrumental variables models, we find that there are initial benefits for students and the mothers of students who attend full‐day kindergarten, but that these differences largely evaporate by third grade. Contrary to claims by some advocates, attending full‐day kindergarten is found to have no additional benefit for students in families with income below the poverty threshold. © 2006 by the Association for Public Policy Analysis and Management 相似文献