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   577175篇
  免费   7468篇
  国内免费   1046篇
电工技术   10623篇
综合类   486篇
化学工业   91997篇
金属工艺   23546篇
机械仪表   18700篇
建筑科学   13293篇
矿业工程   4362篇
能源动力   14747篇
轻工业   46540篇
水利工程   7063篇
石油天然气   15017篇
武器工业   40篇
无线电   61159篇
一般工业技术   118028篇
冶金工业   97878篇
原子能技术   14730篇
自动化技术   47480篇
  2021年   5660篇
  2020年   4135篇
  2019年   5423篇
  2018年   9418篇
  2017年   9586篇
  2016年   10097篇
  2015年   6220篇
  2014年   10581篇
  2013年   26836篇
  2012年   16304篇
  2011年   21792篇
  2010年   17511篇
  2009年   19354篇
  2008年   19665篇
  2007年   19360篇
  2006年   16772篇
  2005年   15198篇
  2004年   14409篇
  2003年   13997篇
  2002年   13602篇
  2001年   13100篇
  2000年   12576篇
  1999年   12229篇
  1998年   27965篇
  1997年   20285篇
  1996年   15828篇
  1995年   12227篇
  1994年   11033篇
  1993年   10805篇
  1992年   8487篇
  1991年   8170篇
  1990年   8119篇
  1989年   7866篇
  1988年   7568篇
  1987年   6860篇
  1986年   6607篇
  1985年   7524篇
  1984年   6808篇
  1983年   6507篇
  1982年   5837篇
  1981年   5956篇
  1980年   5675篇
  1979年   5779篇
  1978年   5704篇
  1977年   6216篇
  1976年   7742篇
  1975年   5132篇
  1974年   4937篇
  1973年   5006篇
  1972年   4296篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
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   
102.
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   
103.
104.
105.
106.
107.
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   
108.
The viability and β‐galactosidase activity of four Lactobacillus strains in milk drink containing gums during 28 days of refrigerated storage at 4 °C were assessed. The population of Lactobacillus rhamnosus GGB101 and Lactobacillus rhamnosus GGB103 were maintained, whereas the population of Lactobacillus reuteri DSM20016 and Lactobacillus reuteri SD2112 significantly decreased. The recommended level of 6 log CFU g?1 was exceeded for all tested trains throughout storage. The highest viable number of Lactobacillus rhamnosus GGB103 (8.76 ± 0.03 log CFU mL?1) was obtained in the product containing carrageenan–maltodextrin. The addition of guar–locust bean–carrageenan led to 20‐fold increase in the level of β‐galactosidase activity for L. rhamnosus GGB101 (1208 ± 2.12 Miller units mL?1) compared to the control (61 ± 2.83 Miller units mL?1). Our results suggested that gums could be added to milk to improve viability and enhance β‐galactosidase activity of Lactobacillus.  相似文献   
109.
110.
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