全文获取类型
收费全文 | 25464篇 |
免费 | 1178篇 |
专业分类
各国政治 | 912篇 |
工人农民 | 1833篇 |
世界政治 | 1325篇 |
外交国际关系 | 827篇 |
法律 | 16722篇 |
中国共产党 | 2篇 |
中国政治 | 106篇 |
政治理论 | 4826篇 |
综合类 | 89篇 |
出版年
2021年 | 86篇 |
2020年 | 432篇 |
2019年 | 460篇 |
2018年 | 1762篇 |
2017年 | 1717篇 |
2016年 | 1619篇 |
2015年 | 580篇 |
2014年 | 558篇 |
2013年 | 1884篇 |
2012年 | 659篇 |
2011年 | 1369篇 |
2010年 | 1482篇 |
2009年 | 1098篇 |
2008年 | 1204篇 |
2007年 | 1152篇 |
2006年 | 534篇 |
2005年 | 506篇 |
2004年 | 614篇 |
2003年 | 503篇 |
2002年 | 435篇 |
2001年 | 679篇 |
2000年 | 616篇 |
1999年 | 492篇 |
1998年 | 252篇 |
1997年 | 193篇 |
1996年 | 212篇 |
1995年 | 226篇 |
1994年 | 197篇 |
1993年 | 184篇 |
1992年 | 308篇 |
1991年 | 312篇 |
1990年 | 297篇 |
1989年 | 275篇 |
1988年 | 314篇 |
1987年 | 264篇 |
1986年 | 324篇 |
1985年 | 318篇 |
1984年 | 255篇 |
1983年 | 236篇 |
1982年 | 186篇 |
1981年 | 157篇 |
1980年 | 144篇 |
1979年 | 228篇 |
1978年 | 127篇 |
1977年 | 100篇 |
1976年 | 78篇 |
1975年 | 96篇 |
1974年 | 124篇 |
1973年 | 79篇 |
1972年 | 78篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
891.
Steven W. Hemelt Nathaniel L. Schwartz Susan M. Dynarski 《Journal of policy analysis and management》2020,39(3):686-719
Dual-credit courses expose high school students to college-level content and provide the opportunity to earn college credits, in part to smooth the transition to college. With the Tennessee Department of Education, we conduct the first randomized controlled trial of the effects of dual-credit math coursework on a range of high school and college outcomes. We find that the dual-credit advanced algebra course alters students’ subsequent high school math course-taking, reducing enrollment in remedial math and boosting enrollment in precalculus and Advanced Placement math courses. We fail to detect an effect of the dual-credit math course on overall rates of college enrollment. However, the course induces some students to choose four-year universities instead of two-year colleges, particularly for those in the middle of the math achievement distribution and those first exposed to the opportunity to take the course in eleventh rather than twelfth grade. We see limited evidence of improvements in early math performance during college. 相似文献
892.
Drew M. Anderson Katharine M. Broton Sara Goldrick-Rab Robert Kelchen 《Journal of policy analysis and management》2020,39(3):720-739
We conduct the first long-term experimental evaluation of a need-based financial aid program, the privately funded Wisconsin Scholars Grant. Over multiple cohorts, the program failed to increase degree completion and graduate school enrollment up to 10 years after matriculation. The program did reduce time-to-degree for some students and modestly increased the number of STEM degrees earned. The lack of robust effects raises important questions about the conditions necessary for financial aid to benefit students. 相似文献
893.
Patrick Megan E. Rhew Isaac C. Duckworth Jennifer C. Lewis Melissa A. Abdallah Devon Alisa Lee Christine M. 《Journal of youth and adolescence》2020,49(4):869-880
Journal of Youth and Adolescence - Young adults experience social role transitions across multiple life domains, and a deeper understanding of the ways in which these simultaneous transition... 相似文献
894.
Both China and India are adopting information and communication technologies to facilitate openness and transparency in their governments, and hence reduce corruption. Distinctive from their traditional anticorruption approaches, is the innovative e-government approach an effective solution to corruption in these two large developing countries? This paper addresses the question through comparative in-depth interviews with 44 mid- or senior-level officials in the public sector in these two countries. The first study of its kind, our research shows that civil servants in both countries overall think positively about transparency and technology in reducing corruption. However, to what extent these innovative measures will be effective is conditional on various factors, such as political willingness, income inequality, and infrastructure readiness. What is worth noting is that the Chinese respondents were more positive regarding the role of transparency, whereas the Indian respondents were more positive about the role of technology, which may reflect the different facilitators of corruption and the constraints of anticorruption in China and India. 相似文献
895.
Amidst calls for more scrutiny of the failure of infrastructure public–private partnerships (PPPs), uncertainty about how we can measure failure remains, and little systematic evidence illuminates its likelihood. Our mixed‐methods design explores the notion of failure and identifies the conditions under which it happens. The first phase of our research employs documentary analysis and semistructured expert interviews, and identifies project cancellation as capturing the most severe occurrences of failure. A second phase statistically analyzes a unique World Bank data set capturing the provisions of over 4,000 infrastructure PPPs launched between 1990 and 2015 in 89 countries. We find robust evidence supporting the theoretical claim that PPPs are less likely to be canceled in countries with more veto points among their political institutions to restrain politicians from intervening in policy implementation. Cancellation is a rare, but valid indicator of failure, and the importance of veto players clarifies how political risk operates in this context. 相似文献
896.
Developing nations demand a different scholarly approach in the field of public administration. We advance an agenda for research that stands on four pillars. First, in the absence of easily accessible data scholars of developing world public administration must assemble it for themselves. Second, building and testing theory plays a paramount role because researchers face limited information. Third, in developing countries, multi‐national and non‐governmental organizations are often crucial and must be considered in studying public administration. Fourth, given the novelties and ambiguities researchers face, qualitative information must be integrated throughout the research process. Our article—and the articles in this volume—constitute a call for developing country research to contribute to the study of public administration writ large, informing our understanding of both developing and developed states. 相似文献
897.
Youngmin Kim M.S. Won-sil Choi Ph.D. Byoungjun Jeon B.S. Tae Hyun Choi M.D. Ph.D. 《Journal of forensic sciences》2020,65(2):458-464
Cholesterol and squalene are fatty materials of latent fingermarks that can be utilized for dating methodologies and visualization techniques. Previous studies have suggested these compounds undergo degradation in fingermarks as a function of time (days) and light at ambient temperature. However, studies assessing how their composition changes at low and high temperatures over short periods of time (hours) have not been published previously. Here, we performed quantitative analysis of cholesterol and squalene in natural fingermark residue using PVDF membrane, after exposure to a range of temperatures (−20 to 100°C) for 4 and 8 h. We found that levels of both fatty materials remained constant at −20 to 60°C, but both showed significant reduction at 100°C, over short exposure times. These results indicate that cholesterol and squalene are detectable at −20 to 60°C, whereas at 100°C or higher, both are lost due to rapid thermal degradation. 相似文献
898.
Sierra F. Kaszubinski B.Sc. Jennifer L. Pechal Ph.D. Carl J. Schmidt M.D. Heather R. Jordan Ph.D. Mark E. Benbow Ph.D. Mariah H. Meek Ph.D. 《Journal of forensic sciences》2020,65(2):513-525
Microbial communities have potential evidential utility for forensic applications. However, bioinformatic analysis of high-throughput sequencing data varies widely among laboratories. These differences can potentially affect microbial community composition and downstream analyses. To illustrate the importance of standardizing methodology, we compared analyses of postmortem microbiome samples using several bioinformatic pipelines, varying minimum library size or minimum number of sequences per sample, and sample size. Using the same input sequence data, we found that three open-source bioinformatic pipelines, MG-RAST, mothur, and QIIME2, had significant differences in relative abundance, alpha-diversity, and beta-diversity, despite the same input data. Increasing minimum library size and sample size increased the number of low-abundant and infrequent taxa detected. Our results show that bioinformatic pipeline and parameter choice affect results in important ways. Given the growing potential application of forensic microbiology to the criminal justice system, continued research on standardizing computational methodology will be important for downstream applications. 相似文献
899.
Sabrina Zorbo M.S. Patrick P. J. M. H. Jeuniaux Ph.D. 《Journal of forensic sciences》2020,65(2):641-648
In the case of suspicious deaths, the technique of 1:1 taping is often used in Belgium. It consists of affixing a large number of adhesive tapes to the body of the victim. It is conventionally aimed at obtaining microtraces (e.g., fibers, hair) and is usually not used for DNA analysis. However, in some cases, DNA analysis of certain areas of interest identified on the 1:1 taping material can offer a last resort solution. The four-step method that is described in this article involves the selection of areas of interest on the body (Step 1), the selection of the corresponding tapes (Step 2), the decontamination of the tapes (Step 3), the selection of areas of interest on the tapes, for DNA sampling (Step 4). The method is illustrated by its successful application in four murder cases. In each case, DNA profiles of good quality could be identified, including profiles of persons different from the victim. 相似文献
900.
Wu-ting Tsai Ph.D. Chia-I Hu M.S. Chia-Yun Chang L.L.M. 《Journal of forensic sciences》2020,65(1):255-258
The horizontal displacement of the human body resulting from fatal fall from a height is an important variable commonly used to inversely determine the cause or identify other forensic aspects of the fall. When examining the horizontal displacement, the wind effect is generally ignored. This technical note reports analytical modeling of the falling process, utilizing previous measurements of wind force acting on the human body, for determining the functional relationship between the wind speed and the horizontal displacement in the falling process. The result reveals that it does not take extremely rare wind conditions to cause a considerable shift of the human body, highlighting the importance to consider wind as a factor in investigations of fatal falls. 相似文献