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   2911篇
  免费   13篇
各国政治   26篇
工人农民   35篇
世界政治   512篇
外交国际关系   87篇
法律   1988篇
中国共产党   22篇
中国政治   57篇
政治理论   180篇
综合类   17篇
  2020年   3篇
  2018年   3篇
  2016年   3篇
  2015年   3篇
  2014年   14篇
  2013年   6篇
  2012年   234篇
  2011年   228篇
  2010年   44篇
  2009年   30篇
  2008年   198篇
  2007年   211篇
  2006年   181篇
  2005年   193篇
  2004年   187篇
  2003年   194篇
  2002年   207篇
  2001年   145篇
  2000年   172篇
  1999年   61篇
  1998年   46篇
  1997年   31篇
  1996年   20篇
  1995年   37篇
  1994年   47篇
  1993年   48篇
  1992年   32篇
  1991年   31篇
  1990年   22篇
  1989年   15篇
  1988年   40篇
  1987年   16篇
  1986年   20篇
  1985年   24篇
  1984年   13篇
  1983年   19篇
  1982年   12篇
  1981年   23篇
  1980年   18篇
  1979年   13篇
  1978年   13篇
  1977年   13篇
  1976年   6篇
  1975年   6篇
  1974年   5篇
  1973年   6篇
  1964年   4篇
  1962年   3篇
  1961年   6篇
  1959年   3篇
排序方式: 共有2924条查询结果,搜索用时 0 毫秒
11.
12.
13.
Danger: implants     
The superheated debate over breast implants awakened a sleeping giant of an issue clouding "medical devices"--the government's clumsy nomenclature for any medical product that is not a drug, from breast implants and artificial hips to X-ray machines and surgical thread. Some 130 categories of high-risk devices are in use with little or no proof of safety, reliability or effectiveness. All appeared before 1976, the year that the Food and Drug Administration got the authority to regulate such products. Under activist chief David Kessler and with added clout from a 1990 law, the FDA plans to scrutinize the entire 130-item list. Five will get special attention starting early next year: saline-filled breast implants, inflatable penile implants, testicular implants, heart-bypass pumps and cranial stimulators. U.S. News has looked at all five devices, using FDA data obtained through the Freedom of Information Act. In-depth computer analysis suggested that penile implants deserve closer examination. Why is clear from the following report.  相似文献   
14.
"In this essay, certain aspects related to rural-urban mortality differentials in Mexico are analyzed....[These include] the availability, advantages, and limitations of different sources of information and the disparity of levels and tendencies according to particular indicators of acceptable reliability, especially those deriving from recent demographic surveys conducted in Mexico. The findings confirm an inverse ratio between size of settlement and mortality, and reveal a widening of the differentials over time." (SUMMARY IN ENG)  相似文献   
15.
16.
17.
18.
19.
A series of related studies (Freedman and Berelson, 1976; Mauldin and Berelson, 1978; and Tsui and Bogue, 1978) have presented empirical findings based on multiple regression analysis which indicated that family planning program effort (FP), as measured by an index developed by Lapham and Mauldin (1972), was the single most important predictor of (or influence on) fertility reduction in less-developed countries (LDCs). The basic results have been confirmed repeatedly. A more extensive data set was used to extend the analysis to a comparison of results of corss-sectional models circa 1970 and 1980. The study builds upon the results of past studies yet differs from them in several ways. All the variables in the present study were measured at 2 points in time: circa 1970 and circa 1980, allowing a comparison between cross-sectional models for 1970 and 1980. Among the cases included in this multivariate analysis was China, a country usually excluded for lack of data. The analysis was extend to 85 countries. Cases were weighted by population, having the effect of increasing the impact of larger countries such as India and China on the outcome of the analysis. Total fertility rate (TFR) was used as an indicator of fertility. For 1970, family planning program effort had the strongest direct influence on fertility (a result consistent with previous studies). Life expectancy at birth was the other direct influence. The direct influence of life expectancy at birth was less than that of family planning, but the total influence was greater. After life expectancy and family planning, school enrollment and relative educational status of women had the strongest indirect and total influences. The other variables all had a positive influence on fertility. When the total variance attributable was considered, directly and indirectly to each of the independent variables, urbanization, carlorie supply, and per capita gross national product all accounted for less than 5% of the variance in fertility, all of it indirect. Life expectancy, family planning, and school enrollment each explained (directly plus indirectly) more than 10% of the variance in fertility. The pattern differed somewhat for 1980. Calorie supply, per capita gross national product, and relative educational status of women had no influence, direct or indirect on fertility. Also for 1980, life expectancy had a stronger direct influence on fertility than family planning. Overall, life expectancy at birth, family planning program effort, and total school enrollment emerged as the principal influences on fertility.  相似文献   
20.
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