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   3777篇
  免费   133篇
各国政治   130篇
工人农民   123篇
世界政治   232篇
外交国际关系   121篇
法律   2656篇
中国政治   35篇
政治理论   600篇
综合类   13篇
  2021年   27篇
  2020年   49篇
  2019年   52篇
  2018年   75篇
  2017年   90篇
  2016年   81篇
  2015年   67篇
  2014年   76篇
  2013年   278篇
  2012年   87篇
  2011年   111篇
  2010年   80篇
  2009年   87篇
  2008年   109篇
  2007年   86篇
  2006年   105篇
  2005年   88篇
  2004年   98篇
  2003年   97篇
  2002年   91篇
  2001年   186篇
  2000年   133篇
  1999年   104篇
  1998年   38篇
  1997年   48篇
  1996年   35篇
  1995年   49篇
  1994年   44篇
  1993年   54篇
  1992年   81篇
  1991年   86篇
  1990年   77篇
  1989年   63篇
  1988年   84篇
  1987年   81篇
  1986年   98篇
  1985年   108篇
  1984年   86篇
  1983年   80篇
  1982年   38篇
  1981年   36篇
  1979年   34篇
  1978年   32篇
  1975年   31篇
  1974年   45篇
  1973年   24篇
  1972年   27篇
  1971年   31篇
  1970年   30篇
  1968年   32篇
排序方式: 共有3910条查询结果,搜索用时 15 毫秒
921.
ABSTRACT

Drawing on the education production function literature, we examine the short-run impact of comprehensive education reforms in Barbados on primary school student outcomes. Using a variety of specifications to test the robustness of our results, we find modest and mixed changes in student test scores. Our findings are discussed in the context of management challenges that resulted from the need to coordinate a multi-faceted project in a rapidly developing nation; alignment of goals and schedules of two multi-national development banks, the Ministry of Education, Youth Affairs and Sports (MES), and the Government of Barbados; and, a very rapidly changing information technology environment that led, in part, to changes in planned capital improvements in schools, equipment needs, and had implications for teacher training.  相似文献   
922.
923.
924.
Mandible is the hardest and most durable bone of the skull exhibiting a high degree of sexual dimorphism. Especially ramus of mandible is subjected to greater stress than any other bone of the skull because of the process of mastication. This study has been performed to establish the osteometric standards for practical use in forensic context over Indian population using mandibular ramus. The sample consists of 116 mandibles of Northern Indian population (M:F; 92:24, mean age 37.4 years), collected from the Department of Forensic Medicine, IMS, BHU, Varanasi. Osteometric informations about five metric parameters (coronoid height, projective height, condylar height, and maximum breadth and minimum breadth of ramus) were taken with sliding calipers. These parameters were subjected to different discriminant function analysis using SPSS 16.0. All parameters showed significant sexual dimorphism (p < 0.001 in all cases) with an overall accuracy of 80.2%, and coronoid height was the single best parameter providing an accuracy of 74.1%.  相似文献   
925.
The authors have developed a method for molecular-genetic analysis of DNA from isolated cells for the purpose of forensic medical diagnostics. The method is based on the use of the laser capture microdissection (LCM) technology in combination with typing of mitochondrial DNA. Optimization of the conditions for amplification of polymorphic mtDNA loci in preparations containing minimal amounts of the genetic material was accomplished at the initial stage of the work. To this effect, the two-round polymerase chain reaction was employed that allowed the amplified material to be accumulated in the amount sufficient for sequenation. At the next stages, the system thus obtained was tested on the cell model (using isolated cells of human buccal epithelium). It was shown that the proposed method is suitable for the analysis of specific mtDNA characteristics in a single human cell.  相似文献   
926.
The objective of the present work was to study the distribution of tetramethylthiuram disulfide (TMTD) in the body of warm-blooded animals as exemplified by white rats. TMTD was administered intragastrically and detected in the unaltered form in other internal organs. It was found to accumulate in the largest amounts in the gastric contents, kidneys, and urine.  相似文献   
927.
An original test-system for the preliminary quantitative and qualitative evaluation of isolated DNA is proposed by the polymerase chain reaction in real time (PCR-RT) based on the TaqMan technology. This test-system permits to simultaneously measure the amount of DNA in the sample, identify the genetic gender, and detect PCR inhibitors. The method has been approbated in the practical work of forensic medical experts.  相似文献   
928.
This study investigated the value of antemortem (AM) and postmortem (PM) radiographs of the claviculae and C3-T4 vertebrae to identify skeletons of missing U.S. soldiers from past military operations. In total, 12 field-recovered skeletons and AM chest radiographs of 1460 individuals were used. For each skeleton, examiners analyzed an array of AM chest radiographs (up to 1000 individuals) and attempted to identify the correct PM/AM radiographic match. When examiners were able to compare all images within a single test, only true-positive identifications were made. When AM radiographs were presented one-at-a-time, in sequential order, and without examiners having knowledge of array size, erroneous identifications resulted but they were almost exclusively made by untrained examiners (accuracy = 35% vs. 90% for trained examiners). This study demonstrates the value of chest radiographs for the identification of disarticulated and even eroded skeletons, but only when methods are wielded by trained examiners.  相似文献   
929.
The successful identification of human skeletal remains relies on proven diagnostic techniques for sex determination. This research utilized 608 individuals from South Africa (420 men, 188 women) to conduct a blind nonmetric determination of sex from three features of the distal humerus: olecranon fossa shape, angle of the medial epicondyle, and trochlear extension. A scoring system between males and females was implemented, and the aggregate score of the three features determined the estimated sex of the skeletal element in question. With all features combined, black and white South Africans were categorized successfully as either male or female 75.5% (77% accuracy rate for females, 74% accuracy rate for males). This classification rate is lower than what was found in previous studies, but suggests that characteristics of the distal humerus are still quite valuable when estimating skeletal sex. More research is needed to assess reasons for the differential expression of these traits in different populations and to determine whether the method is nonpopulation specific.  相似文献   
930.
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