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   423155篇
  免费   3628篇
  国内免费   882篇
电工技术   7754篇
综合类   210篇
化学工业   62412篇
金属工艺   21100篇
机械仪表   14758篇
建筑科学   7888篇
矿业工程   4233篇
能源动力   8197篇
轻工业   22962篇
水利工程   5539篇
石油天然气   14421篇
武器工业   35篇
无线电   45201篇
一般工业技术   94594篇
冶金工业   74441篇
原子能技术   13802篇
自动化技术   30118篇
  2021年   3765篇
  2019年   3745篇
  2018年   7032篇
  2017年   7284篇
  2016年   7673篇
  2015年   4285篇
  2014年   7442篇
  2013年   17091篇
  2012年   11024篇
  2011年   14159篇
  2010年   11505篇
  2009年   13060篇
  2008年   13542篇
  2007年   13225篇
  2006年   11325篇
  2005年   10286篇
  2004年   10178篇
  2003年   9841篇
  2002年   9554篇
  2001年   9721篇
  2000年   9362篇
  1999年   9244篇
  1998年   22150篇
  1997年   15569篇
  1996年   11910篇
  1995年   9086篇
  1994年   8120篇
  1993年   8271篇
  1992年   6271篇
  1991年   6225篇
  1990年   6325篇
  1989年   6041篇
  1988年   5679篇
  1987年   5157篇
  1986年   5128篇
  1985年   5570篇
  1984年   5227篇
  1983年   4882篇
  1982年   4599篇
  1981年   4781篇
  1980年   4561篇
  1979年   4657篇
  1978年   4845篇
  1977年   5157篇
  1976年   6329篇
  1975年   4346篇
  1974年   4379篇
  1973年   4384篇
  1972年   3849篇
  1971年   3481篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
61.
Variations in lipid profile and incidence of vascular events were evaluated. Group 1 had a 29.3% reduction of total and a 38.3% reduction of LDL cholesterol as against reductions of 9% and 9.6% respectively in group 2. No significant difference was observed between the two groups as far as the vascular events considered were concerned. Pravastatin is an effective and safe drug. The lack of influence on the evolution of vascular disease would appear to be correlated to the small number of subjects studied and the short follow-up.  相似文献   
62.
63.
The electrochemical and corrosion behaviour of a nickel base super alloy (C-263) has been investigated in the deaerated binary and ternary solution mixture of concentrated phosphoric acid, acetic acid, sulphuric acid, nitric acid or water using potentiostatic technique at 35°C. The possibilities of electropolishing of this alloy in these solution mixtures have been also explored. The alloy showed distinct active, passive and transpassive behaviour in the experimental solutions. The alloy remained active and turned passive in the negative potential region. Transpassive dissolution of the alloy is observed and electropolishing is achieved in this region. The best electropolishing is obtained in 50% H3PO4 + 40% CH3COOH + 10% H2SO4. Higher content of water in the electrolytic solution is not useful for electropolishing of the alloy The experimental results also suggest that a current plateau in the transpassive potential region is not a sufficient condition to achieve electropolishing.  相似文献   
64.
Several in vivo and in vitro methods for monitoring immunological properties of two allergoids obtained by formaldehyde treatment of ovalbumin (OA) were developed. The calculated molecular weight of allergoids was 80 kD (OA-F1) and 165 kD (OA-F2), respectively. The allergenic activity in vitro of allergoids in mast-cell histamine release assay was 1000 times lower than of OA. Both allergoids showed reduced ability to induce passive cutaneous anaphylaxis in the Sprague-Dawley rats or systemic anaphylaxis in Dunkin-Harley guinea-pigs. The ability of OA and allergoids to bind to the OA-specific IgE antibodies was measured in vivo by the inhibition of passive cutaneous anaphylaxis (PCA-inhibition). Allergoid binding to IgE was 51-66% lower than the native allergen. Moreover, the avidity of OA-specific IgG antibodies, measured by ELISA-inhibition, for allergoids and allergen was of the same order. Allergoids induced a different pattern of humoral immune response from that, induced by the native allergen. Thus, after immunization of BALB/c mouse, both allergoids induced a higher production of IgG and a lower production of IgE than OA, only OA-F2 induced a lower production of IgG1. The differences in the IgA response to the immunogens was not significant. Delayed hypersensitivity studies in the BALB/c mouse showed that allergoids were 5- to 12-times less effective in inducing a cell-mediated immune response than OA. The present study provides a battery of immunological methods for preclinical testing of modified allergens.  相似文献   
65.
The effectiveness of the hybrid system sonication followed by wet oxidation (SONIWO) to treat otherwise refractory waste has been demonstrated. In such a hybrid system homogeneous CuSO4 catalyst was found to be very efficient.  相似文献   
66.
The technological process of cold forging applied for the first time in the production of the casing of the internal joint with races is described. The process operations of cold forging and the annealing and carburizing regimes for this part me described.  相似文献   
67.
A method is considered for increasing the immunity from interference of broadband systems for measuring and transmitting information. It is based on utilizing nonlinear methods to process spread-spectrum signals. The possibility is investigated of using a quasioptimal receiving device which can be implemented in practice. It is shown that the proposed method makes it possible to solve the rejection problem at the physical level. Translated from Izmeritel'naya Tekhnika, No. 11, pp. 13–15, November, 1996.  相似文献   
68.
69.
70.
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