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   527805篇
  免费   7240篇
  国内免费   1475篇
电工技术   9594篇
综合类   526篇
化学工业   79240篇
金属工艺   19998篇
机械仪表   15256篇
建筑科学   12772篇
矿业工程   2274篇
能源动力   14609篇
轻工业   47494篇
水利工程   5241篇
石油天然气   9349篇
武器工业   37篇
无线电   60052篇
一般工业技术   102089篇
冶金工业   103586篇
原子能技术   10566篇
自动化技术   43837篇
  2022年   3254篇
  2021年   5002篇
  2020年   3571篇
  2019年   4650篇
  2018年   7913篇
  2017年   7692篇
  2016年   8047篇
  2015年   5643篇
  2014年   9350篇
  2013年   24294篇
  2012年   14807篇
  2011年   20341篇
  2010年   15955篇
  2009年   17833篇
  2008年   18223篇
  2007年   17895篇
  2006年   15598篇
  2005年   14277篇
  2004年   13656篇
  2003年   13450篇
  2002年   12686篇
  2001年   12854篇
  2000年   11891篇
  1999年   12617篇
  1998年   32833篇
  1997年   22910篇
  1996年   17466篇
  1995年   13049篇
  1994年   11289篇
  1993年   10987篇
  1992年   7919篇
  1991年   7424篇
  1990年   7266篇
  1989年   7018篇
  1988年   6470篇
  1987年   5768篇
  1986年   5657篇
  1985年   6269篇
  1984年   5902篇
  1983年   5174篇
  1982年   4902篇
  1981年   4971篇
  1980年   4706篇
  1979年   4610篇
  1978年   4409篇
  1977年   5339篇
  1976年   6972篇
  1975年   3796篇
  1974年   3552篇
  1973年   3670篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
151.
In 50 patients auditory threshold and brain stem evoked potential studies were carried out before and after myelography. Due to the analysis of amplitudes and latencies of auditory brain stem measurements, significant functional disorders of the hearing organ and the auditory pathway could be demonstrated. In most of the patients these functional disorders were found to be subclinical, whereas 12 patients showed alterations extending from a subjectively slight hearing loss to an audiometrically objectified acute hearing loss depending on its intensity in each case. The reasons of these functional disorders could not be clarified. An open cochlear aqueduct through which perilymph enters the subarachnoidal space leading to a secondary endolymphatic hydrops can be considered as the cause in cases where manifest symptoms develop. The changes in brain stem audiometry can be additionally explained by changes in osmolality of the inner ear fluids which may lead to the development of an endolymphatic hydrops.  相似文献   
152.
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   
153.
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   
154.
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   
155.
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   
156.
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   
157.
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   
158.
Carstensen and Rhodes1 have suggested that when, in stability programs, assays cannot be performed immediately after the protocol-designated storage time, then freezing them until such a time when assays can be performed would be a reasonable manner to retain the protocol schedule. They caution, however, that such a procedure may not be valid for dissolution data. The article to follow deals with real-time data showing that such a process is feasible for Nalidixic Acid tablets (and presumably for other tablets as well), and that, furthermore, the dissolution pattern would seem to be “frozen” as well.  相似文献   
159.
160.
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