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   17188篇
  免费   2157篇
  国内免费   4篇
电工技术   1359篇
综合类   403篇
化学工业   8625篇
金属工艺   246篇
机械仪表   390篇
建筑科学   654篇
矿业工程   167篇
能源动力   104篇
轻工业   1728篇
水利工程   117篇
石油天然气   68篇
无线电   339篇
一般工业技术   2855篇
冶金工业   182篇
原子能技术   24篇
自动化技术   2088篇
  2023年   628篇
  2022年   354篇
  2021年   691篇
  2020年   671篇
  2019年   570篇
  2018年   557篇
  2017年   391篇
  2016年   617篇
  2015年   790篇
  2014年   824篇
  2013年   1397篇
  2012年   532篇
  2011年   407篇
  2010年   764篇
  2009年   924篇
  2008年   409篇
  2007年   379篇
  2006年   277篇
  2005年   273篇
  2004年   223篇
  2003年   210篇
  1998年   177篇
  1997年   133篇
  1996年   197篇
  1995年   187篇
  1994年   159篇
  1993年   222篇
  1992年   155篇
  1991年   122篇
  1990年   151篇
  1989年   173篇
  1988年   138篇
  1987年   163篇
  1986年   183篇
  1985年   165篇
  1984年   167篇
  1983年   175篇
  1982年   156篇
  1981年   202篇
  1980年   166篇
  1979年   170篇
  1977年   147篇
  1976年   149篇
  1975年   202篇
  1974年   188篇
  1973年   365篇
  1972年   212篇
  1971年   150篇
  1970年   144篇
  1968年   153篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
92.
93.
The crosslink reaction is in fact from a commercial perspective the most reward ing reacting there is.It is used to adjust viscosity or rheology parameter in a large number of applications like p.e.the food or adhesives and textile printing.  相似文献   
94.
Failure analysis of hollow glasses The failure analysis is very important to clarify damages of hollow glasses. Damages of glass bottle through over pressure are very often linked with damages to persons. This is the reason why the causal research is from particular importance. Different surface characteristics of glass fragments as well as the fracture pattern give hints to the direction of the crack, the stress just before breakage and the reason of stress. A reconstruction of the bottle is a further helpful instrument for cause studies. The difference of the various characteristics of the surface will be explained. Further on there will be discussed different reasons and mechanism of fracture.  相似文献   
95.
96.
97.
There are two aspects to cell formation in flexible manufacturing systems, cell sizing or deciding on the optimum number of machines to be allocated to each cell, and then allocation of specific machines to each cell. Although the latter problem has been investigated extensively there is a paucity of published work on the former. This paper discusses the effects of cell sizing on operational flexibility.Operational flexibility is that aspect of flexibility that enables manufacturing systems to respond with speed and efficiency to changes in the manufacturing environment while maintaining an effective level of control.  相似文献   
98.
Metabolic Effects of ω-3 Fatty Acids Biological effects of ω-3 fatty acids are related to their properties as structural components of cell membranes, their role as precursors of eicosanoids and their effects on lipoprotein metabolism. This is the basis for a great variety of metabolic effects, many of which of increasing medical interest. Particularly in the cardiovascular field, ω-3 fatty acids have been shown to have a wide spectrum of potentially antiatherogenic effects. Among these are the inhibition of platelet aggregation, reduction of blood viscosity, lowering of blood pressure and suppression of inflammatory reactions in the arteriosclerotic plaque. The principal actions in lipid metabolism are a reduction in triglycerides and a small increase in HDL2. The effect on LDL-cholesterol is complex and an adverse LDL-increase may occur in particular hyperlipoproteinemias.  相似文献   
99.
Übersicht Die folgende Arbeit verfolgt u. a. auch didaktische Absichten. Das Biot-Savartsche Gesetz wird oft falsch oder mindestens sehr mißverständlich dargestellt und auch auf unzulässige Weise benutzt. Ausgangspunkt der Mißverständnisse ist die auch in vielen Lehrbüchern anzutreffende unkorrekte Aussage, man könne einem von StromI durchflossenen Linienelement ds ein magnetostatisches Feld dB [entsprechend der Gleichung (32) des folgenden Beitrags] zuordnen. Im folgenden werden derartige Aussagen untersucht und in modifizierter Form korrekt dargestellt.
Remarks concerning the Law of Biot-Savart
Contents The following paper is at least partly of a didactic nature. The Biot-Savart law of magnetostatics is often interpreted in an illegitimate manner and consequently applied incorrectly. The source of these misunderstandings and errors is the incorrect statement that a magnetic field dB [as given by equation (32) of this paper] is caused by an electric currentI flowing along a line element ds, a statement very popular also in many textbooks. Questions related to this problem are investigated and widespread misleading statements are replaced by correct ones.
  相似文献   
100.
We consider an extension of the functional programming language Standard ML with a modular structure based upon concepts in category theory such as categories, functors, natural transformations and adjunctions. In essence, we are following the categorical imperative of considering arrows as well as objects. This is intended to enforce a certain mathematical rigour on the programmer, so that the only programs that can be expressed are those with a categorical significance. The essentially algebraic nature of category theory means that we may generate equational correctness conditions for the modular structure of programs, thus separating the correctness of individual functions from that of modules. We describe this programming language, give examples of its use, and explain how it is implemented in a type system.  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