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   24121篇
  免费   155篇
  国内免费   626篇
电工技术   343篇
综合类   135篇
化学工业   2272篇
金属工艺   669篇
机械仪表   1293篇
建筑科学   1246篇
矿业工程   540篇
能源动力   150篇
轻工业   5994篇
水利工程   333篇
石油天然气   370篇
武器工业   69篇
无线电   1493篇
一般工业技术   7941篇
冶金工业   536篇
原子能技术   287篇
自动化技术   1231篇
  2023年   30篇
  2022年   47篇
  2021年   65篇
  2020年   49篇
  2019年   32篇
  2018年   37篇
  2016年   62篇
  2015年   70篇
  2014年   132篇
  2013年   149篇
  2012年   2278篇
  2011年   2933篇
  2010年   643篇
  2009年   292篇
  2008年   1973篇
  2007年   1959篇
  2006年   1595篇
  2005年   1556篇
  2004年   1334篇
  2003年   1193篇
  2002年   1039篇
  2001年   955篇
  2000年   857篇
  1999年   607篇
  1998年   328篇
  1997年   280篇
  1996年   283篇
  1995年   278篇
  1994年   277篇
  1993年   219篇
  1992年   292篇
  1991年   260篇
  1990年   278篇
  1989年   283篇
  1988年   184篇
  1987年   193篇
  1986年   231篇
  1985年   238篇
  1984年   230篇
  1983年   207篇
  1982年   188篇
  1981年   153篇
  1980年   127篇
  1979年   91篇
  1978年   62篇
  1977年   28篇
  1976年   33篇
  1975年   29篇
  1974年   27篇
  1973年   26篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
103.
104.
105.
The meat quality of M. longissimus muscle was evaluated in 851 pigs by using the Fibre Optic Probe (FOP) at three sites in the muscle and in both halves of the carcass. A systematic difference between sites was found, with the lowest light scattering (indicating the best meat quality) in the mid-part of the muscle and higher light scattering in the anterior and posterior parts. A non-systematic variation was also observed, with the opposite pattern in some animals, even though it was not frequent. A negative influence of the shackling was found, yielding higher FOP values in the shackled half.

Drip loss measurements in the Longissimus muscle, taken from another 100 pig carcasses, were evaluated using three methods. Drip loss, too, showed a considerable variation along the Longissimus muscle, with minimum losses around the last rib. Repeatability estimates, calculated from two non-consecutive pieces of the Longissimus dorsi muscle from each carcass, varied from 0·4 when keeping samples vacuum packed for 2 days, to 0·5 when the samples were either kept in plain plastic bags for 2 days or in a meat container with a squared inset for 1 or 2 days.  相似文献   

106.
107.
A two-step procedure for restoring scintigraphic images is described. The first step uses a local-statistics algorithm for improvement in signal-to-noise ratio by smoothing the Poisson noise. The second step aims at improvement in spatial resolution by removing the linear blur using the iterative restoration algorithm. We present some results of computer simulations and restoration of scintigraphic images that demonstrate the effectiveness of the proposed procedure.  相似文献   
108.
Issues in the quadratic discriminant functions (QDF) are discussed and two types of modified quadratic disriminant functions (MQDF1, MQDF2) which are less sensitive to the estimation error of the covariance matrices are proposed. The MQDF1 is a function which employs a kind of a (pseudo) Bayesian estimate of the covariance matrix instead of the maximum likelihood estimate ordinarily used in the QDF. The MQDF2 is a variation of the MQDF1 to save the required computation time and storage. Two discriminant functions were applied to Chinese character recognition to evaluate their effectiveness, and remarkable improvement was observed in their performance.  相似文献   
109.
The crystal plasticity was implemented in the finite element method(FEM) software ABAQUS through the user subroutine UMAT. By means of discretizing the space at the grain level with the Voronoi diagram method, a polycrystal model was built and used in the FEM analysis. The initial orientation of each grain was generated based on the orientation distribution function(ODF). The developed model was successfully applied in simulation of polycrystalline aluminium samples deformed by the tensile tests. The theoretical strain--stress relation was in good agreement with the experimental result. The simulation results show that the grain size has significant effect on the deformation behavior. The initial plastic deformation usually occurs at grain boundaries, and multiple slip often results in an enhanced local hardening at grain boundaries.  相似文献   
110.
铸造过程中熔融金属内的固体渣粒的运动轨迹是非常重要的。文中给出了粒子传输轨迹的数学模型,该数学模型采用显示法来确定粒子的位置。模拟研究结果与用其它数学模型的模拟结果比较,吻合良好。该模型可用于固体粒子位置的确定,并应用到SUTCAST软件中。  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