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   669573篇
  免费   8021篇
  国内免费   1392篇
电工技术   11696篇
综合类   2772篇
化学工业   102165篇
金属工艺   30962篇
机械仪表   23588篇
建筑科学   15085篇
矿业工程   5109篇
能源动力   15765篇
轻工业   49260篇
水利工程   8382篇
石油天然气   15701篇
武器工业   39篇
无线电   71189篇
一般工业技术   138398篇
冶金工业   100335篇
原子能技术   15168篇
自动化技术   73372篇
  2021年   5480篇
  2019年   5289篇
  2018年   25081篇
  2017年   24424篇
  2016年   20453篇
  2015年   6752篇
  2014年   10499篇
  2013年   26327篇
  2012年   19465篇
  2011年   32612篇
  2010年   27364篇
  2009年   26572篇
  2008年   27835篇
  2007年   29351篇
  2006年   16441篇
  2005年   17459篇
  2004年   15961篇
  2003年   15625篇
  2002年   14119篇
  2001年   12990篇
  2000年   12575篇
  1999年   12087篇
  1998年   27729篇
  1997年   20084篇
  1996年   15686篇
  1995年   12048篇
  1994年   10912篇
  1993年   10651篇
  1992年   8363篇
  1991年   8146篇
  1990年   8006篇
  1989年   7780篇
  1988年   7499篇
  1987年   6757篇
  1986年   6544篇
  1985年   7396篇
  1984年   6715篇
  1983年   6445篇
  1982年   5780篇
  1981年   5907篇
  1980年   5634篇
  1979年   5737篇
  1978年   5675篇
  1977年   6181篇
  1976年   7699篇
  1975年   5115篇
  1974年   4905篇
  1973年   4985篇
  1972年   4280篇
  1971年   4040篇
排序方式: 共有10000条查询结果,搜索用时 296 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