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   566484篇
  免费   6744篇
  国内免费   1003篇
电工技术   10508篇
综合类   466篇
化学工业   90086篇
金属工艺   23335篇
机械仪表   18499篇
建筑科学   12547篇
矿业工程   4312篇
能源动力   14434篇
轻工业   45796篇
水利工程   6941篇
石油天然气   14961篇
武器工业   39篇
无线电   60286篇
一般工业技术   116255篇
冶金工业   95632篇
原子能技术   14681篇
自动化技术   45453篇
  2021年   5485篇
  2019年   5275篇
  2018年   9205篇
  2017年   9413篇
  2016年   9834篇
  2015年   6028篇
  2014年   10250篇
  2013年   26111篇
  2012年   15784篇
  2011年   21092篇
  2010年   16977篇
  2009年   18823篇
  2008年   19074篇
  2007年   18772篇
  2006年   16291篇
  2005年   14750篇
  2004年   14022篇
  2003年   13696篇
  2002年   13250篇
  2001年   12856篇
  2000年   12332篇
  1999年   12020篇
  1998年   27671篇
  1997年   20055篇
  1996年   15634篇
  1995年   12012篇
  1994年   10869篇
  1993年   10619篇
  1992年   8333篇
  1991年   8103篇
  1990年   7991篇
  1989年   7763篇
  1988年   7480篇
  1987年   6749篇
  1986年   6534篇
  1985年   7393篇
  1984年   6701篇
  1983年   6439篇
  1982年   5782篇
  1981年   5899篇
  1980年   5633篇
  1979年   5733篇
  1978年   5663篇
  1977年   6182篇
  1976年   7690篇
  1975年   5109篇
  1974年   4904篇
  1973年   4983篇
  1972年   4279篇
  1971年   4038篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Measurement Techniques - A method is proposed for transferring the unit of mean power of laser radiation by means of measuring high-intensity power (kilowatts), with the possibility of constant...  相似文献   
92.
93.
Theoretical Foundations of Chemical Engineering - A set of measures to establish the technology for manufacturing highly active sources of γ radiation with an active part from...  相似文献   
94.
Puzanov  A. S.  Obolenskiy  S. V.  Kozlov  V. A. 《Semiconductors》2020,54(8):946-950
Semiconductors - On the basis of the Monte Carlo algorithm, a method for calculating the energy spectrum of hot nonequilibrium electrons and holes in the track of a primary recoil atom after being...  相似文献   
95.
Upper Barremian – Lower Aptian inner platform “Urgonian” limestones in the Mont de Vaucluse region, SE France, consist of alternating metre-scale microporous and tight intervals. This paper focuses on the influence of structural deformation on the reservoir properties of the Urgonian limestone succession in a study area near the town of Rustrel. Petrographic, petrophysical and structural data were recovered from five fully-cored boreholes, from the walls of a 100 m long underground tunnel, and from a 50 m long transect at a nearby outcrop. The data allowed reservoir property variations in the Urgonian limestones to be studied from core to reservoir scale. Eleven Reservoir Rock Types (RRTs) were identified based on petrographic features (texture, grain size), reservoir properties (porosity, permeability), and the frequency of structural discontinuities such as fractures, faults and stylolites. Tight and microporous reservoir rock types were distinguished. Tight reservoir rock types were characterised by early cementation of intergranular pore spaces and by the presence of frequent structural discontinuities. By contrast microporous reservoir rock types contained preserved intragranular microporosity and matrix permeability, but had very few structural discontinuities. Observed vertical alternations of microporous and tight rock types are interpreted to have been controlled by the early diagenesis of the Urgonian carbonates. Deformation associated with regional-scale tectonic phases, including Albian – Cenomanian “Durancian” uplift (∼105 to 96 Ma) and Pyrenean compression (∼55 to 25 Ma), resulted in the modification of the initial petrophysical properties of the Urgonian limestones. An early diagenetic imprint conditioned both the intensity of structural deformations and the associated circulations of diagenetic and meteoric fluids. Evolution of the Reservoir Rock Types is therefore linked both to the depositional conditions and to subsequent phases of structural deformation.  相似文献   
96.
97.
98.
99.
100.
Pinhão seed is an unconventional source of starch and the pines grow up in native forests of southern Latin America. In this study, pinhão starch was adjusted at 15, 20 and 25% moisture content and heated to 100, 110 and 120 °C for 1 h. A decrease in λ max (starch/iodine complex) was observed as a result of increase in temperature and moisture content of HMT. The ratio of crystalline to amorphous phase in pinhão starch was determined via Fourier transform infra red by taking 1045/1022 band ratio. A decrease in crystallinity occurred as a result of HMT. Polarised light microscopy indicated a loss of birefringence of starch granules under 120 °C at 25% moisture content. Granule size distribution was further confirmed via scanning electron microscopy which showed the HMT effects. These results increased the understanding on molecular and structural properties of HMT pinhão starch and broadened its food and nonfood industrial applications.  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