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   2951篇
  免费   21篇
  国内免费   1篇
电工技术   5篇
综合类   6篇
化学工业   46篇
金属工艺   4篇
机械仪表   7篇
建筑科学   6篇
能源动力   18篇
轻工业   43篇
水利工程   1篇
无线电   23篇
一般工业技术   72篇
冶金工业   2714篇
原子能技术   3篇
自动化技术   25篇
  2023年   7篇
  2022年   6篇
  2021年   15篇
  2020年   9篇
  2019年   8篇
  2018年   13篇
  2017年   8篇
  2016年   7篇
  2015年   6篇
  2014年   11篇
  2013年   18篇
  2012年   10篇
  2011年   8篇
  2010年   10篇
  2009年   11篇
  2008年   10篇
  2007年   12篇
  2006年   12篇
  2005年   5篇
  2004年   12篇
  2003年   15篇
  2002年   4篇
  2001年   2篇
  2000年   3篇
  1999年   107篇
  1998年   890篇
  1997年   504篇
  1996年   336篇
  1995年   169篇
  1994年   140篇
  1993年   184篇
  1992年   12篇
  1991年   22篇
  1990年   28篇
  1989年   32篇
  1988年   22篇
  1987年   23篇
  1986年   21篇
  1985年   29篇
  1983年   4篇
  1982年   16篇
  1981年   10篇
  1980年   31篇
  1978年   5篇
  1977年   49篇
  1976年   100篇
  1975年   2篇
  1973年   2篇
  1969年   2篇
  1967年   2篇
排序方式: 共有2973条查询结果,搜索用时 125 毫秒
31.
32.
Pulmonary surfactant is a complex mixture of lipids and proteins that functions to keep alveoli from collapsing at the end of expiration. Dipalmitoylphosphatidylcholine has been identified as the most important component for lowering surface tension at the air-liquid interface. Hydrophobic surfactant apoproteins, SP-B and SP-C, play essential roles in the biophysical functions of the surfactant phospholipids. Hydrophilic surfactant apoproteins (SP-A and SP-D) that are members of C-type lectin superfamily, interact with phospholipids and glycolipids and modulate host defense functions in the lung. SP-A also plays an important role in regulating phospholipid homeostasis in the alveolar spaces. Recent advances in genetics and molecular biology have clarified the structure-function relationship of surfactant apoproteins.  相似文献   
33.
34.
35.
36.
37.
The activity of rifabutin (LM 427) against Mycobacterium leprae was evaluated in armadillos inoculated earlier with human-derived M. leprae. Rifabutin was administered daily at a dose of 6 mg/kg body weight/day. The effect of rifabutin on M. leprae harvested from armadillos was determined by measuring the intracellular levels of ATP (an indicator of metabolic activity) of M. leprae and also their ability to multiply in the mouse footpads and in vitro in DH medium. Within 2 weeks of initiating the treatment, ATP levels declined to 21% of the original (pre-treatment level) and these M. leprae failed to multiply in the footpads of mice as well as in the in vitro culture system. This suggests that rifabutin was able to kill all M. leprae within 2 weeks. After 8 weeks the treatment was terminated and results showed that M. leprae from the treated armadillos remained non-viable in the mouse footpad system as well as in the in vitro system, indicating bactericidal action of rifabutin. The results suggest that rifabutin can be a substitute for rifampin in the leprosy multi-drug therapy regimen.  相似文献   
38.
Volatile anaesthetics have historically been considered to act in a nonspecific manner on the central nervous system. More recent studies, however, have revealed that the receptors for inhibitory neurotransmitters such as gamma-aminobutyric acid (GABA) and glycine are sensitive to clinically relevant concentrations of inhaled anaesthetics. The function of GABA(A) and glycine receptors is enhanced by a number of anaesthetics and alcohols, whereas activity of the related GABA rho1 receptor is reduced. We have used this difference in pharmacology to investigate the molecular basis for modulation of these receptors by anaesthetics and alcohols. By using chimaeric receptor constructs, we have identified a region of 45 amino-acid residues that is both necessary and sufficient for the enhancement of receptor function. Within this region, two specific amino-acid residues in transmembrane domains 2 and 3 are critical for allosteric modulation of both GABA(A) and glycine receptors by alcohols and two volatile anaesthetics. These observations support the idea that anaesthetics exert a specific effect on these ion-channel proteins, and allow for the future testing of specific hypotheses of the action of anaesthetics.  相似文献   
39.
Abstract. An Information Systems Methodology is usually presented as a sequential set of tasks — planning, analysis, design and construction — resulting in a new business application. This classical 'forward-engineering' approach must be adapted to changing business needs — business process redesign, quality management, process and systems templates, advanced technologies, application packages, the reuse of existing information systems resources, and rapid delivery cycles. Using the most general concept of a Business Programme, this paper describes a methodological approach incorporating these modern themes that is qualitatively and quantitatively different from the classical model. It provides a framework for the integration of otherwise independent methodologies, and shows how an entire programme can be formulated, planned and executed. An example is provided, and the approach is justified.  相似文献   
40.
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