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   8210篇
  免费   295篇
各国政治   325篇
工人农民   307篇
世界政治   641篇
外交国际关系   293篇
法律   5465篇
中国政治   47篇
政治理论   1389篇
综合类   38篇
  2021年   57篇
  2020年   133篇
  2019年   163篇
  2018年   201篇
  2017年   224篇
  2016年   220篇
  2015年   153篇
  2014年   216篇
  2013年   824篇
  2012年   219篇
  2011年   229篇
  2010年   186篇
  2009年   182篇
  2008年   221篇
  2007年   242篇
  2006年   252篇
  2005年   208篇
  2004年   217篇
  2003年   233篇
  2002年   182篇
  2001年   330篇
  2000年   319篇
  1999年   228篇
  1998年   93篇
  1997年   73篇
  1996年   79篇
  1995年   74篇
  1994年   86篇
  1993年   68篇
  1992年   148篇
  1991年   160篇
  1990年   141篇
  1989年   157篇
  1988年   140篇
  1987年   155篇
  1986年   136篇
  1985年   154篇
  1984年   120篇
  1983年   142篇
  1982年   97篇
  1981年   93篇
  1980年   73篇
  1979年   104篇
  1978年   79篇
  1977年   67篇
  1976年   57篇
  1975年   47篇
  1974年   57篇
  1973年   66篇
  1971年   58篇
排序方式: 共有8505条查询结果,搜索用时 15 毫秒
991.
The economic well-being of both working and retired persons has improved significantly since the Social Security Act was passed in 1935. More people are employed now than at any time since then, despite declining employment among the aged and more years of school attendance among the young. The ratio of non-workers to workers--a broad measure of dependency--is lower now than at any time since the 1930's. Social security has grown and matured to become a strong foundation of retirement income, and other work-related employee benefits have grown in tandem with social security. Employer contributions for social insurance and related employee benefits have grown from being about a 1-percent supplement to aggregate wages and salaries in 1929 to nearly 20 percent today. Social security and Medicare account for just over a fourth of employer contributions, while other public and private retirement systems represent just over another fourth. The balance of benefits for active workers includes group health and life insurance, unemployment insurance, workers' compensation, temporary disability insurance, and related benefits. Pay for holidays, vacations, and sick leave is estimated to have increased from less than 1 percent of aggregate pay in 1929 to about 10 percent today. The improved economic status of the aged has been documented by a series of surveys beginning in 1941-42 and carried out from time to time until 1972 and biennially since 1976. The earlier surveys were supplemented with estimates from record data and tables from the Bureau of the Census. The income of the aged as a whole has grown by about 75 percent over the past 2 decades after taking inflation into account. The income of the aged as a whole grew faster than that of the nonaged in the 1970's and early 1980's when real social security benefits increased faster than inflation and wages lagged behind it. New beneficiaries in 1982 were in better health and were more likely to retire because they wanted to than was true of their counterparts in the early 1940's. Not only have benefits continued to be the main component of income of the aged as total incomes have grown, but also benefits have become much larger in relation to average earnings than used to be the case. Retired workers are much more likely now than in the early 1940's to have other pensions or income from assets to supplement benefits.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   
992.
This paper explores the linkages between development, “appropriate” administrative technology and the training of development managers. In so doing, it traces the intimate relationships between development administration, conceptual paradigms and administrative know-how as a scientific and technological system. Orthodoxy, neo-orthodoxy and critical paradigms are discussed and a number of elements to reformulate a development administration paradigm are considered. Based upon this discussion the paper concludes with a tentative outline identifying training needs for development managers and a number of observations about such training: its “appropriatness”, professionalisation and the issue of international cooperation.  相似文献   
993.
The pelves of 100 white skeletons were measured on both sides for the following: (1) length from the superiormost aspect of the pubic symphysis to the nearest rim of the acetabulum (PS-A), (2) length from the highest point of the pubic tubercle to the nearest rim of the acetabulum (PT-A), (3) acetabular diameter (AD), (4) the vertical distance from the anterior aspect of the ischial tuberosity to the farthest rim of the acetabulum (IT-A), and (5) greatest femur head diameter. From these, three indices were derived: AD/PS-A (acetabulum/pubis index), AD/PT-A (acetabular diameter/pubic tubercle-acetabular rim index), and IT-A/PS-A (ischium-acetabulum height/pubic symphysis-acetabular rim index). The left AD/PS-A ratio and left IT-A height proved statistically to be of greatest discriminating value. Using these two variables, a discriminant function was derived which correctly separated 98% of our sample. The acetabulum/pubis ratio alone correctly assigned 95%. With either the discriminant function analysis of two variables or the acetabulum/pubis index as a single predictor, 97% of our sample of known sex was correctly identified if all specimens that fell within a doubtful or overlapping range of values were sorted by femur head diameter.  相似文献   
994.
Determinations of blood cyanide and carboxyhemoglobin concentrations were performed in 18 victims found dead in buildings after fires during a 2-year period. The results indicated that 50% of the victims had been exposed to toxic levels of hydrogen cyanide and 90% to toxic levels of carbon monoxide. Lethal concentrations of carbon monoxide were found in 83% of the victims. In one case a lethal blood cyanide but a non-toxic blood carboxyhemoglobin value was found. It is concluded that carbon monoxide appears to be more important than hydrogen cyanide as a toxic agent in the fire atmosphere, but cyanide poisoning without carbon monoxide poisoning may, under certain circumstances, be the cause of death in fire victims.  相似文献   
995.
996.
997.
Arrow wounds represent an unusual class of wounds rarely seen by most death investigators. Although the edged, broadhead-tipped arrow produces a wound usually characteristic of archery/crossbow weapons, the plain, field-tipped arrow wound can be confused with gunshot injuries in those cases in which powder residue or firearm projectiles or fragments or both are not recovered. We present a case of a deer carcass with a wound of uncertain firearm or archery origin which initiated a comparison of firearm wounds and archery wounds on fresh road-killed deer. We found the following features to be valuable in the differentiation of gunshot wounds and field-tipped archery wounds: First, the majority of the gunshot wounds (but none of the arrow wounds) had identifiable, macroscopic, wipe-off material and chemically identifiable wipe-off residue by spot test. Second, the archery wound defects had very inconspicuous abrasion rings as compared to the often prominent abrasion rings of gunshot wounds. Third, the actual central defect in the archery wounds was more likely to be oblong or slit-like compared to the gunshot wound defects, which were more likely to be round.  相似文献   
998.
999.
Seminal fluid was studied biochemically for sperm identification in stains. The qualitative and quantitative distribution of amino acids in samples of fresh sperm has been alayzed. These findings were compared to the results of a similar study of fresh samples and stains of urine, saliva, vaginal fluor, and sweat. The results obtained show a specific and relatively constant level of amino acids in each of five biological liquids. There was no significant variation in results between fresh samples and stains.  相似文献   
1000.
Frozen tissues were studied histologically to determine what changes were produced by freezing. Samples of brain, lung, liver, small intestine, and kidney from 20 stray dogs were treated in 3 ways: formalin fixation (control), frozen for 2 days plus formalin fixation, or frozen for 7 days plus formalin fixation. Major histological changes caused by freezing were loss of staining, extracellular fluid accumulation, cell shrinkage, fractures, hemolysis, and hematin formation. Lesser changes included loss of bronchial cilia, prominence of collagen in alveolar septa and meninges, and intracellular vacuolization of epithelial cells. Although these changes were annoying, adequate visualization of the tissues was usually possible.  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