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   659068篇
  免费   9755篇
  国内免费   1959篇
电工技术   12250篇
综合类   624篇
化学工业   97872篇
金属工艺   25072篇
机械仪表   18900篇
建筑科学   15695篇
矿业工程   2839篇
能源动力   17884篇
轻工业   55914篇
水利工程   6362篇
石油天然气   11166篇
武器工业   43篇
无线电   77934篇
一般工业技术   127124篇
冶金工业   133482篇
原子能技术   12816篇
自动化技术   54805篇
  2021年   5841篇
  2020年   4235篇
  2019年   5506篇
  2018年   9222篇
  2017年   9008篇
  2016年   9414篇
  2015年   6598篇
  2014年   11057篇
  2013年   29872篇
  2012年   17571篇
  2011年   24226篇
  2010年   19152篇
  2009年   21559篇
  2008年   22145篇
  2007年   21827篇
  2006年   19202篇
  2005年   17680篇
  2004年   17096篇
  2003年   16751篇
  2002年   15937篇
  2001年   16165篇
  2000年   15109篇
  1999年   16199篇
  1998年   42381篇
  1997年   29416篇
  1996年   22637篇
  1995年   16912篇
  1994年   14677篇
  1993年   14400篇
  1992年   10235篇
  1991年   9718篇
  1990年   9508篇
  1989年   9161篇
  1988年   8471篇
  1987年   7374篇
  1986年   7280篇
  1985年   8218篇
  1984年   7578篇
  1983年   6707篇
  1982年   6275篇
  1981年   6482篇
  1980年   6048篇
  1979年   5858篇
  1978年   5632篇
  1977年   6838篇
  1976年   9017篇
  1975年   4887篇
  1974年   4606篇
  1973年   4658篇
  1972年   3847篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
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   
993.
Growth hormone (GH) has recently been shown to affect polymorphonuclear neutrophil granulocyte (PMN) function and to be secreted by mononuclear cells, indicating that the hormone may be active in an immunophysiologic network, acting as an endo- or paracrine priming agent. The purpose of the present study was to evaluate the chemotactic responsiveness of canine peripheral PMN in a dog with acromegaly, caused by spontaneous, progesterone-induced hypersecretion of GH and, secondary to this, a seven-fold increase in insulin-like growth factor I (IGF-I). The chemotactic responsiveness towards zymosan-activated serum (ZAS) and leukotriene B4 (LTB4) was evaluated at a time when the dog suffered from acromegaly and again 57 days after corrective surgery (ovariohysterectomy). The experiments showed that PMN from the patient exhibited enhanced chemotactic migration that appeared to be associated with the hypersomatotropic condition as judged from the reversibility of the phenomenon. The glucose intolerance and elevated serum alkaline phosphatase that were observed in the acromegalic dog were also shown to be reversible following surgery.  相似文献   
994.
995.
996.
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   
997.
We show here that the internucleosomal DNA fragmentation, which is a biochemical hallmark of apoptosis, was induced in a cell density-dependent manner in primary culture of adult rat hepatocytes. This DNA fragmentation could be suppressed by a gene expression inhibitor, indicating the active nature of this process. Moreover, the viability changes in high and low cell density cultures showed a tendency corresponding with the incidence of the DNA fragmentation in them. These results suggest that in hepatocytes there may be a cell density-dependent apoptosis mechanism. In this report, we also show that heparin could suppress this DNA fragmentation with high specificity, and the cell death to some extent.  相似文献   
998.
A multilayer theory has been developed for unidirectional/cross-ply unbalanced laminates subjected to surface shear tractions, using the assumption of plane strain. The analytical solution for the stress field in the laminate is obtained and it is shown that the stresses in each layer are in good agreement with the results of a three-dimensional finite element analysis. Approximate formulae for the analytical stresses are also derived for a laminate subjected to an offset distributed force at one end. The accuracy of this solution is shown by comparison with a three-dimensional finite element analysis.  相似文献   
999.
Numerical investigations are carried out to verify the new super element model developed in Reference 1 for non-linear analysis of stiffened box structures. The results presented here are obtained from a variety of examples which are chosen to illustrate the accuracy and convergence of the model in various applications. Good agreement is obtained for most of the problems considered and the present formulation is found to be accurate and economical for preliminary engineering design.  相似文献   
1000.
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   
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