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   2666篇
  免费   94篇
  国内免费   3篇
电工技术   24篇
化学工业   155篇
金属工艺   8篇
机械仪表   22篇
建筑科学   31篇
矿业工程   2篇
能源动力   20篇
轻工业   301篇
水利工程   3篇
石油天然气   3篇
无线电   134篇
一般工业技术   187篇
冶金工业   1734篇
原子能技术   16篇
自动化技术   123篇
  2022年   10篇
  2019年   17篇
  2018年   15篇
  2017年   11篇
  2016年   24篇
  2015年   10篇
  2014年   13篇
  2013年   52篇
  2012年   36篇
  2011年   45篇
  2010年   21篇
  2009年   29篇
  2008年   49篇
  2007年   54篇
  2006年   54篇
  2005年   55篇
  2004年   59篇
  2003年   49篇
  2002年   51篇
  2001年   33篇
  2000年   25篇
  1999年   63篇
  1998年   472篇
  1997年   300篇
  1996年   225篇
  1995年   138篇
  1994年   109篇
  1993年   129篇
  1992年   19篇
  1991年   47篇
  1990年   27篇
  1989年   32篇
  1988年   19篇
  1987年   19篇
  1986年   19篇
  1985年   20篇
  1984年   14篇
  1983年   20篇
  1982年   15篇
  1981年   24篇
  1980年   30篇
  1979年   14篇
  1978年   15篇
  1977年   66篇
  1976年   124篇
  1975年   8篇
  1974年   12篇
  1973年   8篇
  1971年   8篇
  1970年   10篇
排序方式: 共有2763条查询结果,搜索用时 15 毫秒
61.
Describes the Drug Abuse Reporting Program, the 1st national evaluation study of community-based treatment programs, implemented in the early 1970s. It evolved into a 20-yr longitudinal research program that included during-treatment assessments of client performance, evaluations of treatment effectiveness based on outcomes in the years immediately following treatment, and long-term studies of addiction careers. The Treatment Outcome Prospective Study began in the early 1980s and is now being followed by the Drug Abuse Treatment Outcome Study in the 1990s. These multisite and multimodality studies have helped establish broad-based evidence for treatment efficacy and directions for new studies in the US. The AIDS crisis has had the effect of sharply increasing federal research funds, including grants allocated to enhance and evaluate psychosocial intervention programs for drug users. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
62.
63.
Twenty mothers of preterm babies who had survived to 1 year old, were matched for age and parity of the mother and time of birth of the baby, with 20 mothers delivering fullterm. Bone mineral, body composition and anthropometric measurements were obtained for each mother and analysed using paired t-tests. The only significant difference (P < 0.01) between the groups was a lower fat-free mass in the preterm mothers calculated from skinfold thickness measurements.  相似文献   
64.
65.
66.
Selective antagonists to the Type 3 serotonin receptor (5HT3) in combination with corticosteroids are now considered the standard of care for the prevention of emesis from moderately to highly emetogenic chemotherapy. Here we address issues of optimal dose, schedule and route of administration of four currently available selectable 5HT3 antagonists. This paper utilizes an evidence based medicine approach to the literature regarding this class of drugs, emphasizing the results large, randomized, controlled trials to make formal recommendations concerning optimal use of this important new class of anti-emetic agents. We conclude that for each drug there is a plateau in therapeutic efficacy at a definable dose level above which further dose escalation does not improve outcome. Furthermore, a single dose is as effective as multiple doses or continuous infusion, and finally, emerging data demonstrate that the oral route is equally efficacious as the intravenous route of administration, even with highly emetogenic chemotherapy.  相似文献   
67.
68.
69.
70.
Trifluoroethanol (TFE) is often used to increase the helicity of peptides to make them usable as models of helices in proteins. We have measured helix propensities for all 20 amino acids in water and two concentrations of trifluoroethanol, 15 and 40% (v/v) using, as a model system, a peptide derived from the sequence of the alpha-helix of ribonuclease T1. There are three main conclusions from our studies. (1) TFE alters electrostatic interactions in the ribonuclease T1 helical peptide such that the dependence of the helical content on pH is lost in 40% TFE. (2) Helix propensities measured in 15% TFE correlate well with propensities measured in water, however, the correlation with propensities measured in 40% TFE is significantly worse. (3) Propensities measured in alanine-based peptides and the ribonuclease T1 peptide in TFE show very poor agreement, revealing that TFE greatly increases the effect of sequence context.  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