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   871686篇
  免费   11149篇
  国内免费   2231篇
电工技术   16434篇
综合类   1006篇
化学工业   134138篇
金属工艺   37002篇
机械仪表   28664篇
建筑科学   20924篇
矿业工程   5504篇
能源动力   21818篇
轻工业   71814篇
水利工程   9769篇
石油天然气   17550篇
武器工业   102篇
无线电   98136篇
一般工业技术   175084篇
冶金工业   149332篇
原子能技术   19022篇
自动化技术   78767篇
  2021年   7089篇
  2019年   6897篇
  2018年   15589篇
  2017年   15898篇
  2016年   15027篇
  2015年   8359篇
  2014年   13830篇
  2013年   38322篇
  2012年   22820篇
  2011年   33573篇
  2010年   27424篇
  2009年   29670篇
  2008年   30769篇
  2007年   31667篇
  2006年   24138篇
  2005年   23559篇
  2004年   22000篇
  2003年   21523篇
  2002年   20372篇
  2001年   19511篇
  2000年   18721篇
  1999年   18541篇
  1998年   42355篇
  1997年   30849篇
  1996年   24438篇
  1995年   18945篇
  1994年   17097篇
  1993年   16740篇
  1992年   13245篇
  1991年   12604篇
  1990年   12404篇
  1989年   12014篇
  1988年   11486篇
  1987年   10364篇
  1986年   10074篇
  1985年   11626篇
  1984年   10654篇
  1983年   9963篇
  1982年   9213篇
  1981年   9327篇
  1980年   8832篇
  1979年   8814篇
  1978年   8541篇
  1977年   9729篇
  1976年   12237篇
  1975年   7770篇
  1974年   7462篇
  1973年   7630篇
  1972年   6363篇
  1971年   5919篇
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
121.
122.
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   
123.
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   
124.
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   
125.
126.
127.
128.
Here we report some recent biophysical issues on the preparation of solute-filled lipid vesicles and their relevance to the construction of “synthetic cells.” First, we introduce the “semi-synthetic minimal cells” as the liposome-based cell-like systems, which contain a minimal number of biomolecules required to display simple and complex biological functions. Next, we focus on recent aspects related to the construction of synthetic cells. Emphasis is given to the interplay between the methods of synthetic cell preparation and the physics of solute encapsulation. We briefly introduce the notion of structural and compositional “diversity” in synthetic cell populations.  相似文献   
129.
130.
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