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   603478篇
  免费   8137篇
  国内免费   1176篇
电工技术   11031篇
综合类   1093篇
化学工业   94085篇
金属工艺   23976篇
机械仪表   19491篇
建筑科学   13371篇
矿业工程   4694篇
能源动力   14928篇
轻工业   47563篇
水利工程   7433篇
石油天然气   15014篇
武器工业   43篇
无线电   62467篇
一般工业技术   119672篇
冶金工业   112065篇
原子能技术   14850篇
自动化技术   51015篇
  2021年   5668篇
  2020年   4101篇
  2019年   5372篇
  2018年   9732篇
  2017年   10134篇
  2016年   10915篇
  2015年   6846篇
  2014年   10756篇
  2013年   26676篇
  2012年   17813篇
  2011年   23474篇
  2010年   17728篇
  2009年   19660篇
  2008年   19739篇
  2007年   19421篇
  2006年   16909篇
  2005年   17806篇
  2004年   16427篇
  2003年   15649篇
  2002年   14077篇
  2001年   13621篇
  2000年   12648篇
  1999年   12526篇
  1998年   32167篇
  1997年   22872篇
  1996年   17504篇
  1995年   13143篇
  1994年   11701篇
  1993年   11495篇
  1992年   8535篇
  1991年   8352篇
  1990年   8223篇
  1989年   7989篇
  1988年   7709篇
  1987年   6925篇
  1986年   6677篇
  1985年   7528篇
  1984年   6763篇
  1983年   6496篇
  1982年   5899篇
  1981年   6051篇
  1980年   5794篇
  1979年   5790篇
  1978年   5744篇
  1977年   6729篇
  1976年   8833篇
  1975年   5190篇
  1974年   4938篇
  1973年   5017篇
  1972年   4313篇
排序方式: 共有10000条查询结果,搜索用时 32 毫秒
101.
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   
102.
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   
103.
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   
104.
105.
106.
107.
108.
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   
109.
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   
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