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   29065篇
  免费   1387篇
  国内免费   129篇
电工技术   474篇
综合类   234篇
化学工业   4903篇
金属工艺   774篇
机械仪表   653篇
建筑科学   780篇
矿业工程   145篇
能源动力   471篇
轻工业   4079篇
水利工程   212篇
石油天然气   134篇
武器工业   10篇
无线电   1522篇
一般工业技术   5304篇
冶金工业   7316篇
原子能技术   175篇
自动化技术   3395篇
  2023年   305篇
  2022年   266篇
  2021年   615篇
  2020年   499篇
  2019年   428篇
  2018年   882篇
  2017年   794篇
  2016年   880篇
  2015年   774篇
  2014年   908篇
  2013年   1721篇
  2012年   1311篇
  2011年   1316篇
  2010年   1122篇
  2009年   1067篇
  2008年   1210篇
  2007年   1141篇
  2006年   814篇
  2005年   661篇
  2004年   485篇
  2003年   460篇
  2002年   418篇
  2001年   343篇
  2000年   320篇
  1999年   450篇
  1998年   2284篇
  1997年   1386篇
  1996年   965篇
  1995年   585篇
  1994年   479篇
  1993年   435篇
  1992年   179篇
  1991年   189篇
  1990年   160篇
  1989年   161篇
  1988年   147篇
  1987年   165篇
  1986年   142篇
  1985年   225篇
  1984年   187篇
  1983年   168篇
  1982年   131篇
  1981年   175篇
  1980年   179篇
  1979年   125篇
  1978年   111篇
  1977年   224篇
  1976年   477篇
  1975年   90篇
  1973年   115篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 6, pp. 8–9, June, 1991.  相似文献   
62.
Two hundred twenty-eight patients with successful coronary stent implantation were randomized either to protamine administration and femoral sheath removal (group I, n = 117) or no heparin neutralization and delayed sheath removal (group II, n = 111). The hospital stay after treatment was shorter in patients receiving protamine; therefore, protamine use for neutralizing circulating heparin may be safely administered immediately after stent implantation.  相似文献   
63.
The case is described of a 58 year old man with systemic Whipple's disease with pericardial and pleural effusions and severe pulmonary hypertension. After three months of antibiotic treatment there was a complete resolution, not only of the symptoms known to be associated with Whipple's disease (diarrhoea, arthralgia, pericardial and pleural effusions), but also of pulmonary hypertension.  相似文献   
64.
This contribution describes the preparation, based upon a chemically amplified novolak resist (CAR), electron beam lithography, and ECR plasma etching, of structures with a high aspect ratio (10∶1) and lateral dimensions in the sub-micrometer range (150nm–300nm) which may serve as collector surfaces for sub-μm dust particles in a space experiment.  相似文献   
65.
66.
67.
68.
Reorganisation and evolution of class hierarchies is important for object-oriented system development and has received considerable attention in the literature. The contributions of this paper are: (1) a formal study of a set of extension relations and transformations on class hierarchies; (2) a presentation of a small set of primitive transformations which form a minimal and complete basis for the extension relations; and (3) an analysis of the impact of these transformations at the object level.The study leads to a better understanding of evolution and reuse of object-oriented software and class hierarchies. It also provides a terminology and a means of classification for design reuse. The theory presented in this paper is based on the Demeter data model, which gives a concise mathematical foundation for classes and their inheritance and part-of relationships. Parts of the theory have been implemented in the Demeter System TM C++, a CASE tool for object-oriented design and programming.  相似文献   
69.
Cell suspensions of Escherichia coli as a model for bacterial populations in wastewaters were treated with ozone as a disinfectant in a continuously operated pilot plant with a plug flow reactor. Suspensions with an initial number of CFU (colony forming units) of 108 mL?1 were ozonized with ozone concentrations up to 12 mg/L. Metabolic activities and membrane functions break down with increasing ozone concentrations. The fluorochromization using 3′,6′-diacetylfluorescein (FDA) proved to be a suitable method for the detection of an alteration in permeability of the cell membranes and an inactivation of metabolic activity. By fluorescence microscopic and photometric investigations it could be clearly demonstrated that, in the case of disinfection with ozone, inactivation of the cells includes first of all a damage of the cell membranes. In contrast to the determination of the number of CFU, fluorochromization allows the detection of alteration in metabolic activities.  相似文献   
70.
The relationship between endometriosis and infertility is observed frequently. Patients with both conditions require a conservative approach to their management. Since hormonal therapy is one of those approaches, we sought to compare the efficacy of Danazol and Gestrinone in 80 infertile patients (48 and 32, respectively). Therapy lasted 6 months in both treatment groups, and all patients studied had laboratory tests performed and were clinically evaluated and classified through laparoscopy before and after therapy. The improvement of symptoms and favorable follow-up were similar with both treatments. The reestablishment of menstrual patterns and fertility were also nearly alike in both groups. However, Gestrinone was associated with fewer secondary effects and is easier to administer than Danazol. We conclude that Gestrinone is a useful medication in the management of the infertile patient with endometriosis.  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