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   16478篇
  免费   218篇
  国内免费   234篇
系统科学   292篇
丛书文集   215篇
教育与普及   188篇
理论与方法论   84篇
现状及发展   4337篇
研究方法   530篇
综合类   11015篇
自然研究   269篇
  2015年   133篇
  2014年   191篇
  2013年   202篇
  2012年   323篇
  2011年   690篇
  2010年   229篇
  2009年   279篇
  2008年   404篇
  2007年   435篇
  2006年   395篇
  2005年   426篇
  2004年   395篇
  2003年   347篇
  2002年   351篇
  2001年   457篇
  2000年   500篇
  1999年   512篇
  1998年   272篇
  1997年   326篇
  1996年   283篇
  1995年   245篇
  1994年   233篇
  1993年   215篇
  1992年   340篇
  1991年   273篇
  1990年   285篇
  1989年   276篇
  1988年   267篇
  1987年   248篇
  1986年   202篇
  1985年   261篇
  1984年   180篇
  1983年   140篇
  1980年   137篇
  1979年   331篇
  1978年   256篇
  1977年   241篇
  1976年   224篇
  1975年   238篇
  1974年   306篇
  1973年   278篇
  1972年   236篇
  1971年   337篇
  1970年   474篇
  1969年   327篇
  1968年   312篇
  1967年   319篇
  1966年   349篇
  1965年   223篇
  1958年   209篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
电信产业的快速发展和电信技术的不断创新给电信监管带来了巨大的挑战。为此,本文从分析电信业发展的趋势和由此对电信监管带来的挑战入手,在对国外电信监管模式和技术手段进行充分实证分析的基础上,从政策法律、市场准入、互连互通、资费管制、普遍服务、电信标准等六个方面探讨了我国未来电信监管模式的发展方向和发展趋势。  相似文献   
2.
3.
4.
5.
6.
7.
This paper assesses the information content of two survey indicators for consumption developments in the near future for eight European countries in the period 1985–1998. Empirical work on this topic typically focuses on consumer confidence, the perceptions of buyers of consumption goods. This paper examines whether perceptions of sellers of consumption goods, measured by retail trade surveys, may also improve short‐term monitoring of consumption. We find that both consumer confidence and retailer confidence embody valuable information, when analysed in isolation. For France, Italy and Spain we conclude that adding retail confidence does not improve the indicator model once consumer confidence has been included. For the UK the reverse case is obtained. For the remaining four countries we show that combining consumer sentiment and retail trade confidence into a composite indicator leads to optimal results. Our results suggest that incorporating information from retail trade surveys may offer significant benefits for the analysis of short‐term prospects of consumption. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   
8.
9.
Obese postmenopausal female volunteers were given timed daily oral dosages of bromocriptine, and tested for reduction of body fat stores. This dopamine agonist has been shown to reset circadian rhythms that are altered in obese animals and to reduce body fat levels in several animal models. The participants were instructed not to alter their existing exercise and eating behavior during treatment. Skinfold measurements were taken on 33 subjects as indices of body fat. The measurements (e.g., suprailiac) were reduced after six weeks by about 25%, which represents a reduction of 11.7% of the total body fat. These dramatic decreases in body fat, which are equivalent to that produced by severe caloric restriction, were accompanied by more modest reductions of body weight (2.5%), indicating a possible conservation of protein that is usually lost as a consequence of such caloric restriction. The effects of bromocriptine treatment on body fat and hyperglycemia were also examined in non-insulin dependent diabetics being treated with oral hypoglycemics (7 subjects) or insulin (7 subjects). Total body fat was reduced by 10.7% and 5.1% in diabetics on oral hypoglycemics and insulin, respectively, without any significant reductions in body weight. Hyperglycemia was reduced in most of the 15 diabetic subjects treated leading to euglycemia and even cessation of hypoglycemic drugs in 3 of the 7 subjects during 4-8 weeks of bromocriptine treatment. These findings support the hypothesis that obesity and type II diabetes may be treated effectively with bromocriptine when administered at the proper times and dosages.  相似文献   
10.
根据高新技术产业开发区的特点,提出了一系列有针对性的软、硬件设计。  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