首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   13065篇
  免费   1247篇
各国政治   441篇
工人农民   511篇
世界政治   852篇
外交国际关系   308篇
法律   10093篇
中国共产党   1篇
中国政治   90篇
政治理论   1939篇
综合类   77篇
  2020年   339篇
  2019年   340篇
  2018年   464篇
  2017年   461篇
  2016年   554篇
  2015年   449篇
  2014年   423篇
  2013年   1195篇
  2012年   387篇
  2011年   443篇
  2010年   539篇
  2009年   508篇
  2008年   288篇
  2007年   263篇
  2006年   370篇
  2005年   618篇
  2004年   324篇
  2003年   243篇
  2002年   211篇
  2001年   453篇
  2000年   349篇
  1999年   304篇
  1998年   144篇
  1997年   131篇
  1996年   106篇
  1995年   132篇
  1994年   141篇
  1993年   115篇
  1992年   234篇
  1991年   254篇
  1990年   244篇
  1989年   263篇
  1988年   236篇
  1987年   204篇
  1986年   236篇
  1985年   244篇
  1984年   233篇
  1983年   198篇
  1982年   149篇
  1981年   132篇
  1980年   132篇
  1979年   158篇
  1978年   102篇
  1977年   84篇
  1976年   68篇
  1975年   82篇
  1974年   101篇
  1973年   77篇
  1972年   70篇
  1971年   75篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A longitudinal study of 25 families, with children aged 14 months—5 years, in joint custody, is reported. Varying motivations that lead divorcing parents to undertake and sustain joint custody are discussed, together with the stresses and gratifications of these arrangements for the parents and children. Findings are that where both parents are motivated primarily by interest in the child, where the parenting is sensitive and where the child is shielded from interparental conflict, young children do well. Such families were not the majority in this study. Significant differences emerged in the adjustment of the 1–3 age group as compared with the 3–5 age group which point to greater difficulties for the 3–5 year-olds.  相似文献   
992.
993.
Tests that infer the ancestral origin of a DNA sample have considerable potential in the development of forensic tools that can help to guide crime investigation. We have developed a single-tube 34-plex SNP assay for the assignment of ancestral origin by choosing ancestry-informative markers (AIMs) exhibiting highly contrasting allele frequency distributions between the three major population-groups. To predict ancestral origin from the profiles obtained, a classification algorithm was developed based on maximum likelihood. Sampling of two populations each from African, European and East Asian groups provided training sets for the algorithm and this was tested using the CEPH Human Genome Diversity Panel. We detected negligible theoretical and practical error for assignments to one of the three groups analyzed with consistently high classification probabilities, even when using reduced subsets of SNPs. This study shows that by choosing SNPs exhibiting marked allele frequency differences between population-groups a practical forensic test for assigning the most likely ancestry can be achieved from a single multiplexed assay.  相似文献   
994.
We describe the forensic science application of a method for quantification of human genomic deoxyribonucleic acid (DNA). The two cases cited in this report involve DNA samples extracted from skin tissue and bloodstained clothing recovered from different crime scenes. High-molecular-weight DNA was recovered from both specimens, and the concentrations of these DNAs were estimated to be approximately 0.5 microgram/microL by ethidium bromide/agarose gel electrophoresis. Using the human-specific DNA probe p17H8 (locus D17Z1) to quantify the amount of human genomic DNA in these samples, it is shown that less than 1% of the DNA isolated from the skin tissue is of human origin and that the DNA isolated from the bloodstained clothing is effectively devoid of human DNA sequences. These case examples illustrate the need to quantify not only the total amount of DNA recovered from forensic casework material, but also the proportion of the DNA that is of human origin.  相似文献   
995.
Ethical challenges in public health can have a significant impact on the health of communities if they impede efficiencies and best practices. Competing needs for resources and a plurality of values can challenge public health policymakers and practitioners to make fair and effective decisions for their communities. In this paper, the authors offer an analytic framework designed to assist policymakers and practitioners in managing the ethical tensions they face in daily practice. Their framework is built upon the following set of six considerations: determining population-level utility of the proposed action; demonstrating evidence of need and effectiveness of actions; establishing fairness of goals and proposed implementation strategies; ensuring accountability; and, assessing expected efficiencies and costs associated with the proposed action. Together, these considerations create a structured guide to assist decision-makers in identifying potential ethical challenges and in assessing the moral considerations that underlie public health practice - and possibly even, if the conditions are met, reduce the creation of ethical tension. Although the authors'empirical experiences provide the basis for the framework advanced here, their approach remains to be tested and evaluated by public health practitioners.  相似文献   
996.
997.
998.
We present an accidental autoerotic asphyxiation of a 24-year-old man. Further investigation revealed that 18 years earlier, his brother, then 13, had been found dead, hanging in the family bathroom. Although that death had been ruled a suicide, reevaluation of the death scene indicates that this was also an autoerotic asphyxiation. This is the first reported case of sexual asphyxia involving siblings.  相似文献   
999.
1000.
This review compares the major isoelectric focusing methods that have been published for the separation of group-specific component (Gc) phenotypes since 1978. The various parameters of gel composition, size, electrical and running conditions and sample application points are listed. More current auxiliary methods are also listed. These relate to the extraction of Gc from bloodstains and its identification after isoelectric focusing. Protocols are then recommended for the forensic analysis of Gc phenotypes.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号