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   669417篇
  免费   8058篇
  国内免费   1390篇
电工技术   11702篇
综合类   2771篇
化学工业   102059篇
金属工艺   30977篇
机械仪表   23607篇
建筑科学   15063篇
矿业工程   5111篇
能源动力   15783篇
轻工业   49212篇
水利工程   8389篇
石油天然气   15703篇
武器工业   39篇
无线电   71224篇
一般工业技术   138439篇
冶金工业   100064篇
原子能技术   15167篇
自动化技术   73555篇
  2021年   5517篇
  2020年   4039篇
  2019年   5303篇
  2018年   25101篇
  2017年   24435篇
  2016年   20475篇
  2015年   6760篇
  2014年   10524篇
  2013年   26372篇
  2012年   19498篇
  2011年   32645篇
  2010年   27399篇
  2009年   26603篇
  2008年   27859篇
  2007年   29364篇
  2006年   16456篇
  2005年   17476篇
  2004年   15976篇
  2003年   15629篇
  2002年   14110篇
  2001年   12989篇
  2000年   12572篇
  1999年   12082篇
  1998年   27705篇
  1997年   20069篇
  1996年   15677篇
  1995年   12029篇
  1994年   10892篇
  1993年   10647篇
  1992年   8356篇
  1991年   8143篇
  1990年   7991篇
  1989年   7765篇
  1988年   7490篇
  1987年   6749篇
  1986年   6534篇
  1985年   7394篇
  1984年   6707篇
  1983年   6442篇
  1982年   5782篇
  1981年   5907篇
  1980年   5631篇
  1979年   5737篇
  1978年   5666篇
  1977年   6181篇
  1976年   7691篇
  1975年   5110篇
  1974年   4905篇
  1973年   4982篇
  1972年   4256篇
排序方式: 共有10000条查询结果,搜索用时 140 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