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   249篇
  免费   0篇
电工技术   2篇
化学工业   9篇
机械仪表   2篇
建筑科学   3篇
能源动力   9篇
轻工业   9篇
石油天然气   4篇
无线电   8篇
一般工业技术   53篇
冶金工业   138篇
自动化技术   12篇
  2017年   1篇
  2016年   1篇
  2015年   3篇
  2013年   6篇
  2012年   1篇
  2011年   2篇
  2010年   3篇
  2009年   4篇
  2008年   3篇
  2007年   6篇
  2006年   1篇
  2004年   1篇
  2003年   5篇
  2002年   1篇
  2001年   3篇
  2000年   3篇
  1999年   4篇
  1998年   28篇
  1997年   19篇
  1996年   11篇
  1995年   9篇
  1994年   13篇
  1993年   12篇
  1992年   12篇
  1991年   8篇
  1990年   5篇
  1989年   6篇
  1988年   4篇
  1987年   3篇
  1986年   4篇
  1985年   7篇
  1984年   4篇
  1983年   3篇
  1982年   12篇
  1981年   8篇
  1980年   4篇
  1979年   3篇
  1978年   1篇
  1977年   6篇
  1976年   7篇
  1975年   1篇
  1974年   2篇
  1973年   1篇
  1972年   1篇
  1971年   2篇
  1970年   1篇
  1969年   1篇
  1961年   1篇
  1957年   1篇
  1931年   1篇
排序方式: 共有249条查询结果,搜索用时 15 毫秒
31.
Various kinetic issues that are important for modeling the performance of large-scale-size krypton fluoride lasers have been investigated. These kinetic issues include: electron quenching, photoionization from excited rare gas atoms, fuel burn-up, and the accessibility of higher lying levels of KrF* to be effectively stimulated by the laser cavity flux. The results of these studies have been incorporated into a laser kinetics code. Absorption and gain measurements have been carried out over a broad range of conditions to provide a data base to test the code's accuracy and to make subsequent refinements. The code projections for short-pulse operating conditions important for laser-fusion applications are presented.  相似文献   
32.
The nonlinear impact of a vehicle against a deformable barrier and its subsequent rebound from that barrier are simulated. A one-dimensional elastoplastic model represents the vehicle as a series of rod finite elements and the barrier as a single mass, nonlinear spring. The solution procedure utilizes variable time step integration, contains an error control and eliminates numerical instabilities. A limited study assesses the influence of system parameters on both structure and occupants. The chief objective, however, is to establish the feasibility of the proposed treatment of this class of problems. Some results obtained appear, at first, to contradict intuition. It is observed that modelling a deformable barrier as rigid can lead to unconservative results with respect to structural response of the vehicle.  相似文献   
33.
Using latent growth curve methodology and combining information from 4 different overlapping age cohorts, each measured at 1-yr intervals over a 3-yr period, a single developmental trajectory for adolescent alcohol use was formed spanning 12–17 years of age (n?=?461). At the same time, data collected from the same study sample on a single cohort (n?=?81) over 6 annual assessments (ages 12–17) was examined to determine whether the accelerated design adequately approximated the developmental trend within a true longitudinal design observed over 6 yrs of data collection. Comparison of separate models and a combined multisample model revealed no significant differences between the 2 designs in their representation of initial status and growth, as well as similar effects for the covariates of gender, deviance, and parent alcohol use on initial status and growth. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
34.
35.
Investigated the effects of behavioral couple therapy, cognitive–behavioral therapy, and their combination on female depression 6 and 12 mo after therapy ended. It was predicted that couples receiving a behavioral couple treatment would be less likely to relapse than those receiving a cognitive–behavioral treatment for the depressed spouse alone. Relapse rates, however, did not discriminate between treatments at any follow-up point. Reductions in husband and wife dysphoria and increases in wife facilitative behavior during therapy predicted recovery. Moreover, high rates of husbands' facilitative behavior at posttest were associated with wife recovery and predicted low levels of depression at the 1-yr follow-up. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
36.
If carefully planned for and managed, turnkey graphics can boost the productivity of design and drafting departments.  相似文献   
37.
Aqueous, colloidal dispersions of the enteric polymers, cellulose acetate phthalate (CAP), hydroxypropyl methylcellulose phthalate (HP-551, and polyvinyl acetate phthalate (PVAP) have been developed; and their application in tablet film coating demonstrated. The formation of free phthalic acid as a result of phthalate ester hydrolysis was monitored during storage of the dispersions. Increased free phthalic acid concentrations were found to adversely affect physical stability in dispersions of the cellulose polymers. Storage temperature and pH effects on phthalate ester stability were also considered  相似文献   
38.
Cellular distribution of the Glut1 glucose transporter in normal primate brains was analyzed by immunogold electron microscopy. Two configurations of endothelial Glut1 glucose transporter (high and low density capillaries) have been found in resections of traumatically injured and epileptogenic human brain; the objective of the present study was to ascertain whether these same 2 capillary populations, expressing high and low glucose transporter densities, were the common configuration in normal brain. The relative numbers of Glut1 glucose transporter-associated gold particles on luminal and abluminal endothelial cell membranes were determined within the cerebral cortex of several normal, nonhuman primates. Low Glut1 densities were seen in brain endothelia of both the rhesus and squirrel monkey cortex, with slightly greater quantities of Glut1 in vervet monkey cortices. The Glut1 transporter was most highly expressed in the baboon cortex, approaching the concentrations seen in human brains. In the rhesus, squirrel, and vervet monkeys, Glut1 concentrations were greater on the abluminal than luminal capillary membranes. In contrast, mean luminal membrane Glut1 concentrations were greater in baboons, resembling the distribution seen in the human brain. Brain regional differences in transporter concentration were seen in comparing membrane densities in the baboon cortex (approximately 15 Glut1-gold particles per micrometer), hippocampus (approximately 12 Glut1 gold particles per micrometer), cerebellum (approximately 6 Glut1-gold particles per micrometer), and retinal microvasculature (approximately 20 Glut1-gold particles per micrometer). We conclude that a single, uniform Glut1 distribution characterizes brain capillaries of normal nonhuman primates, and hypothesize that the presence of high and low density glucose transporter endothelial cells (seen in human traumatic injury and seizure resections) represents a pathologic response to brain insult.  相似文献   
39.
40.
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