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   23180篇
  免费   332篇
  国内免费   122篇
电工技术   497篇
综合类   64篇
化学工业   3165篇
金属工艺   939篇
机械仪表   657篇
建筑科学   545篇
矿业工程   67篇
能源动力   599篇
轻工业   1832篇
水利工程   212篇
石油天然气   179篇
武器工业   1篇
无线电   2586篇
一般工业技术   4067篇
冶金工业   6129篇
原子能技术   419篇
自动化技术   1676篇
  2021年   149篇
  2020年   114篇
  2019年   157篇
  2018年   229篇
  2017年   229篇
  2016年   255篇
  2015年   177篇
  2014年   296篇
  2013年   819篇
  2012年   507篇
  2011年   774篇
  2010年   558篇
  2009年   621篇
  2008年   715篇
  2007年   745篇
  2006年   629篇
  2005年   718篇
  2004年   587篇
  2003年   634篇
  2002年   675篇
  2001年   670篇
  2000年   599篇
  1999年   614篇
  1998年   2158篇
  1997年   1402篇
  1996年   1043篇
  1995年   718篇
  1994年   618篇
  1993年   640篇
  1992年   358篇
  1991年   344篇
  1990年   341篇
  1989年   343篇
  1988年   292篇
  1987年   267篇
  1986年   245篇
  1985年   275篇
  1984年   215篇
  1983年   200篇
  1982年   185篇
  1981年   217篇
  1980年   202篇
  1979年   164篇
  1978年   152篇
  1977年   277篇
  1976年   385篇
  1975年   127篇
  1974年   109篇
  1973年   117篇
  1972年   90篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
A decision aid for scheduling production in glass fiber manufacturing industry is described. The methodology combines a linear programming (LP) optimization model with a heuristic model. The LP model determines production goals; the heuristic model then uses the LP output to incorporate system-specific constraints in developing processing sequences.  相似文献   
92.
U Werneke 《Canadian Metallurgical Quarterly》1996,276(18):1470; author reply 1470-1470; author reply 1471
  相似文献   
93.
In a statistical analysis of accident data before and after a speed limit reduction, the time of the countermeasure is, of course, well known. Our understanding of the accident process may, however, be increased if we assume in a thought experiment that this time is unknown. We ask if the data themselves can tell us something about such a possible time. By means of time series of traffic accidents in Zurich before and after a speed limit reduction, different exploratory methods are presented to identify the "unknown" time of this measure. For most of the investigated series, the most likely time was found to lie in the three months before the true introduction. A possible explanation of this result may be that the media already informed the public before the countermeasure was actually introduced. This finding leads to an improved parsimonious intervention model which distinguishes between a possible "preintervention effect" and the usual "intervention effect."  相似文献   
94.
Conclusions Despite the accumulated evidence, many of the investigators as of quite recently have failed to understand that behavioral strategy or decision rules can be inherited and evolve and that they are subject to certain constraints that cannot be surmounted other than by natural selection. For example, in [9, p. 422] we read: The evolutionary pressure cannot act upon the relative contents of social interactions favoring certain individuals over others. The present study shows that the following scheme of conflict, which favors those individuals that conform to it with a better accuracy, can be evolutionary stable. On the basis of the information they receive, the partners estimate the role situation and the equilibrium pair of elementary strategies and use their strategies. If the role situations of the partners are coordinated, the partners cooperate in reducing the conflict and define its result according to AIS. If AIS are not coordinated, they cooperate in reducing the conflict if its expected loss for each is greater than the expected payoff; they escalate the against those that have a lesser set of elementary strategies but also against those that have a less accurate mechanism of AIS recognition. A poor accuracy of recognition mechanism would replace a strictly equilibrium ESS with a mixed strategy.From the point of view of behavioral control, the multilevel conflict model shows that generally for controlling the choices at a certain level actions of an equally high level are necessary. It is impossible, for example, to accomplish certain economic choices by using only informational actions.Translated from Kibernetika, No. 1, pp. 90–98, January–February, 1988.  相似文献   
95.
The dynamics of aging encompass the topics "aging of society" and "coping with chronic illness". Both are discussed using data from a qualitative study on return to work after coronary artery bypass surgery. Data from the retrospective substudy reveal four forms of aging as biographical development toward early retirement, old-age retirement, or related stages. It emerges that the manner of aging is less influenced by medical rehabilitation or medical history, and more by the patient's occupation and socio-economic status. Case reports are used to show that social class is a facilitation context, but not a determining force, regarding the choice between postoperative retirement or return to work. The final section briefly discusses whether the findings concerning the dynamics of aging of the cohort operated on in the late 1970s apply also to that of the cohort operated on in the late 1980s; this is addressed using some data from the prospective sub-study.  相似文献   
96.
97.
W. Hahn  K. Mohr  U. Schauer 《Computing》1985,34(4):375-379
Methods are described for solving a system of linear equations with error bounds. Rectangular and spherical intervals ofR n are used combined. The objective is to get guaranteed accuracy with a minimal effort of computing time.  相似文献   
98.
Metallurgical and Materials Transactions A - The Bauschinger effect in austenitic–ferritic duplex stainless steel 1.4462 was investigated using tension–compression tests combined with...  相似文献   
99.
The addition of ammonium chloride, cobalt sulphate, cesium sulphate and ethylene diamine to a Mattsson solution and the addition of ammonium sulphate to the Pugh solution have been found to produce an inhibitive effect on the stress corrosion cracking of alpha-brass in these solutions. Ammonium chloride and ammonium sulphate additions affect the tarnish formation on the specimen as well as the cracking pattern. Electrochemical polarization studies have also been carried out with these two additives. The observations have been explained in the light of adsorption of these ionic species at selected sites on the metal surface and their possible interference with the cathodic reactions.  相似文献   
100.
The vibrational amplitude is generally large in the case of a boring bar due to its slenderness. A dynamic cutting force model has been presented to take this large amplitude into account. The boring bar is then modelled as a cantilever with this dynamic force acting at the free end and a generalized continuous system model is obtained. This model is solved for the specific case of boring with a zero side cutting edge angle for which published results are available. A reasonably close agreement is found between the proposed model and the experimental results.  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