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   1716320篇
  免费   46267篇
  国内免费   17424篇
电工技术   48883篇
技术理论   31篇
综合类   23341篇
化学工业   314603篇
金属工艺   78565篇
机械仪表   58289篇
建筑科学   67340篇
矿业工程   20699篇
能源动力   57306篇
轻工业   121820篇
水利工程   19142篇
石油天然气   56020篇
武器工业   2359篇
无线电   222695篇
一般工业技术   304546篇
冶金工业   147859篇
原子能技术   36333篇
自动化技术   200180篇
  2022年   17758篇
  2021年   26360篇
  2020年   19743篇
  2019年   21214篇
  2018年   21668篇
  2017年   21940篇
  2016年   27760篇
  2015年   27737篇
  2014年   41570篇
  2013年   102509篇
  2012年   50671篇
  2011年   63198篇
  2010年   56604篇
  2009年   64385篇
  2008年   57031篇
  2007年   53509篇
  2006年   58517篇
  2005年   51150篇
  2004年   48500篇
  2003年   47511篇
  2002年   46211篇
  2001年   42075篇
  2000年   41362篇
  1999年   41209篇
  1998年   41179篇
  1997年   38562篇
  1996年   36654篇
  1995年   32831篇
  1994年   30612篇
  1993年   29205篇
  1992年   27677篇
  1991年   24230篇
  1990年   24259篇
  1989年   23063篇
  1988年   21454篇
  1987年   19576篇
  1986年   18792篇
  1985年   22046篇
  1984年   22332篇
  1983年   20220篇
  1982年   19238篇
  1981年   19236篇
  1980年   17813篇
  1979年   18458篇
  1978年   17656篇
  1977年   17046篇
  1976年   17538篇
  1975年   15914篇
  1974年   15475篇
  1973年   15543篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
83.
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   
84.
85.
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   
86.
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   
87.
88.
89.
90.
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