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   308782篇
  免费   4717篇
  国内免费   934篇
电工技术   5430篇
综合类   390篇
化学工业   49228篇
金属工艺   12512篇
机械仪表   9099篇
建筑科学   7461篇
矿业工程   1944篇
能源动力   7086篇
轻工业   28723篇
水利工程   3346篇
石油天然气   7201篇
武器工业   26篇
无线电   32628篇
一般工业技术   60827篇
冶金工业   56643篇
原子能技术   7649篇
自动化技术   24240篇
  2021年   2587篇
  2019年   2285篇
  2018年   4357篇
  2017年   4211篇
  2016年   4561篇
  2015年   3082篇
  2014年   4936篇
  2013年   13291篇
  2012年   7835篇
  2011年   10238篇
  2010年   8427篇
  2009年   9482篇
  2008年   9870篇
  2007年   9699篇
  2006年   8488篇
  2005年   7819篇
  2004年   7180篇
  2003年   6889篇
  2002年   6932篇
  2001年   6759篇
  2000年   6413篇
  1999年   6566篇
  1998年   16369篇
  1997年   12028篇
  1996年   9242篇
  1995年   6952篇
  1994年   6267篇
  1993年   6112篇
  1992年   4608篇
  1991年   4563篇
  1990年   4391篇
  1989年   4421篇
  1988年   4361篇
  1987年   3716篇
  1986年   3705篇
  1985年   4325篇
  1984年   4119篇
  1983年   3748篇
  1982年   3530篇
  1981年   3697篇
  1980年   3563篇
  1979年   3472篇
  1978年   3537篇
  1977年   4106篇
  1976年   5399篇
  1975年   3229篇
  1974年   3082篇
  1973年   3112篇
  1972年   2689篇
  1971年   2509篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
42.
Wu  Li  Li  Jing  Fu  Caixia  Kühn  Bernd  Wang  Xiaolin 《Magma (New York, N.Y.)》2019,32(4):501-509
Magnetic Resonance Materials in Physics, Biology and Medicine - To investigate the value of using diffusion-weighted imaging (DWI) and intravoxel incoherent motion DWI (IVIM-DWI) to assess the...  相似文献   
43.
Powder Metallurgy and Metal Ceramics - The infiltration of aluminum melts into porous metal skeletons produced by powder metallurgy methods, including 3D printing, under a pressure gradient was...  相似文献   
44.
45.
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   
46.
Metallurgical and Materials Transactions B - The quality requirements of aluminum products are steadily increasing, and the presence of non-metallic inclusions have a large impact on the quality of...  相似文献   
47.
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   
48.
49.
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   
50.
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