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   432760篇
  免费   14802篇
  国内免费   7354篇
电工技术   13287篇
技术理论   9篇
综合类   9219篇
化学工业   65584篇
金属工艺   20193篇
机械仪表   17842篇
建筑科学   16082篇
矿业工程   5343篇
能源动力   10547篇
轻工业   31701篇
水利工程   6043篇
石油天然气   14519篇
武器工业   1093篇
无线电   49802篇
一般工业技术   80115篇
冶金工业   60586篇
原子能技术   11246篇
自动化技术   41705篇
  2022年   5868篇
  2021年   8210篇
  2020年   6156篇
  2019年   5909篇
  2018年   8360篇
  2017年   8905篇
  2016年   8654篇
  2015年   7960篇
  2014年   11304篇
  2013年   20373篇
  2012年   16207篇
  2011年   19489篇
  2010年   15891篇
  2009年   16899篇
  2008年   17116篇
  2007年   16596篇
  2006年   14775篇
  2005年   13246篇
  2004年   11708篇
  2003年   11429篇
  2002年   11219篇
  2001年   10951篇
  2000年   9984篇
  1999年   9875篇
  1998年   18750篇
  1997年   13623篇
  1996年   10756篇
  1995年   8477篇
  1994年   7380篇
  1993年   7164篇
  1992年   5472篇
  1991年   5130篇
  1990年   5001篇
  1989年   4900篇
  1988年   4492篇
  1987年   4057篇
  1986年   4010篇
  1985年   4307篇
  1984年   3994篇
  1983年   3716篇
  1982年   3519篇
  1981年   3560篇
  1980年   3531篇
  1979年   3356篇
  1978年   3461篇
  1977年   3688篇
  1976年   4651篇
  1975年   2964篇
  1974年   2901篇
  1973年   2913篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
103.
Published in Kibernetika i Sistemnyi Analiz, No. 3, pp. 128–150, May–June, 1994.  相似文献   
104.
First break picking is a pattern recognition problem in seismic signal processing, one that requires much human effort and is difficult to automate. The authors' goal is to reduce the manual effort in the picking process and accurately perform the picking. Feedforward neural network first break pickers have been developed using backpropagation training algorithms applied either to an encoded version of the raw data or to derived seismic attributes which are extracted from the raw data. The authors summarize a study in which they applied a backpropagation fuzzy logic system (BPFLS) to first break picking. The authors use derived seismic attributes as features, and take lateral variations into account by using the distance to a piecewise linear guiding function as a new feature. Experimental results indicate that the BPFLS achieves about the same picking accuracy as a feedforward neural network that is also trained using a backpropagation algorithm; however, the BPFLS is trained in a much shorter time, because there is a systematic way in which the initial parameters of the BPFLS can be chosen, versus the random way in which the weights of the neural network are chosen  相似文献   
105.
This report details procedures to measure annihilation anxiety, a concept derived from Freud's 1926 formulation of traumatic anxiety. A 25-item pencil-and-paper inventory administered to patient and to nonpatient samples is described, along with a brief summary of earlier findings. The delineation of nine interrelated experiential components of annihilation anxiety provides the background for the construction of Rorschach and TAT measures of the concept. Findings comparing the pencil-and-paper inventory and the projective test measures are presented as well as examples of responses judged to reflect annihilation anxiety from Rorschach and TAT protocols.  相似文献   
106.
Synergism between recombinant human tumour necrosis factor (rHuTNF) and DNA topoisomerase II inhibitor VP16 during the killing of cells has been studied in six human ovarian cancer cell lines (A2774, A2780, SW626, IGROV-1, SKOV3, Pa1) and a cervical carcinoma cell line (Me180). Studies were performed using an assay of colony formation inhibition (drug treatment for 1 h) and a growth inhibition assay (continuous exposure for 20 h). Concomitant treatment of cells with VP16+rHuTNF enhanced cell killing in all the cell lines tested--an effect observed in both short- and long-term cytotoxicity assays. This study suggests that the activity of VP16 in ovarian cancer cell lines might be enhanced by rHuTNF in in vitro models.  相似文献   
107.
Lactobacillus helveticus ITGL1 is able to hydrolyse many amino-acyl and dipeptidyl-p-nitroanilides. Analysis of heat inactivation kinetics, metal ion and protease inhibitor effects, and the subcellular location of aminopeptidase activities in both the parental strain and mutants deficient in lysyl-p-nitroanilide hydrolysis, led to the characterization of two cell-wall-associated aminopeptidases, APII and APIV. APII, which catalysed L-lysine p-nitroanilide hydrolysis, was purified about 28-fold to homogeneity from cell-wall extracts of L. helveticus ITGL1 and characterized. The purified enzyme appeared to be monomeric, with a molecular mass of 97 kDa. Aminopeptidase activity was greatest at pH 6.5 and 50 degrees C. APII was completely inhibited by bestatin, chelating agents such as EDTA or 1,10-phenanthroline and the divalent cations Zn2+ and Cu2+. The activity of the EDTA-treated enzyme was restored by Co2+, Ca2+ or Mn2+. Although APII was able to degrade several dipeptides and tripeptides with hydrophobic N-terminal amino acid (Leu, Ala), it was inactive on peptides containing Pro or Gly, and may thus contribute to the development of cheese flavour by processing bitter peptides.  相似文献   
108.
Co-word analysis applied to patents through WPIL normalized title words appears to give a useful picture of a given field: we obtain both qualitative (themes) and quantitative information (weight of themes). It also gives information about the strategic aspects of the themes. Furthermore, in some cases, it is an indication of the future of certain themes that may help forecasting and management studies. Finally, it provides information about what could be a real technology growth process, in relation to the so-called translation model used in co-word analysis.  相似文献   
109.
110.
The variation of the dynamic elastic modulus in the immediate vicinity of the tip of the running crack was studied through an iterative procedure, based on the theoretical expressions for the stress-field components and the experimental relation between strain rate and elastic modulus. It was found that the elastic modulus varied strongly around the tip of the crack, both in radial and polar sense. Also it was observed that the polar distribution of the elastic modulus presented clear off-axis extrema in directions that were in good agreement with experimentally measured branching angles, thus indicating a possible relation between these two phenomena.  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