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   252912篇
  免费   20192篇
  国内免费   10286篇
电工技术   14254篇
技术理论   26篇
综合类   16052篇
化学工业   42408篇
金属工艺   14318篇
机械仪表   16318篇
建筑科学   20152篇
矿业工程   8139篇
能源动力   7134篇
轻工业   15528篇
水利工程   4065篇
石油天然气   17551篇
武器工业   1869篇
无线电   28152篇
一般工业技术   30001篇
冶金工业   13559篇
原子能技术   2598篇
自动化技术   31266篇
  2024年   876篇
  2023年   4023篇
  2022年   6759篇
  2021年   10095篇
  2020年   7731篇
  2019年   6532篇
  2018年   7300篇
  2017年   8247篇
  2016年   7443篇
  2015年   9788篇
  2014年   12561篇
  2013年   14787篇
  2012年   15978篇
  2011年   17357篇
  2010年   15207篇
  2009年   14380篇
  2008年   13916篇
  2007年   13308篇
  2006年   13765篇
  2005年   11964篇
  2004年   8063篇
  2003年   6996篇
  2002年   6223篇
  2001年   5590篇
  2000年   6060篇
  1999年   7046篇
  1998年   5860篇
  1997年   4853篇
  1996年   4575篇
  1995年   3814篇
  1994年   3072篇
  1993年   2133篇
  1992年   1669篇
  1991年   1309篇
  1990年   997篇
  1989年   800篇
  1988年   590篇
  1987年   365篇
  1986年   285篇
  1985年   209篇
  1984年   140篇
  1983年   107篇
  1982年   129篇
  1981年   105篇
  1980年   77篇
  1979年   46篇
  1978年   27篇
  1976年   35篇
  1962年   42篇
  1961年   40篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
94.
The evaluation of cell's weatherability is of practical interest. To further improve the soluble lead flow battery's weatherability, physiochemical properties of electrolytes containing fluoborate, perchlorate, methanesulfonate and trifluoromethanesulfonate are investigated from ?60 to 50 °C. Activities of CF3SO3H and HClO4 are poor in trifluoromethanesulfonate and perchlorate solutions due to common anion effect. The solubility of lead salt can be improved by increasing temperature, but worsened by increasing acid's content. With the temperature increasing, the conductivity is enhanced, and the viscosity is lowered for four solutions. The same results have been found by increasing acid's content except for CF3SO3H. The high energy efficiency can be achieved for cells over ?40–0 °C using fluoborate and perchlorate solutions, 73.2% at ?40 °C and 78.1% at ?30 °C respectively. Over the temperature range of 20–50 °C, the cells with methanesulfonate and trifluoromethanesulfonate solutions have good performance, 77.4% and 73.7% at 50 °C respectively.  相似文献   
95.
96.
97.
98.
99.
Over the past decades, the number of patients with dry eye disease (DED) has increased dramatically. The incidence of DED is higher in Asia than in Europe and North America, suggesting the involvement of cultural or racial factors in DED etiology. Although many definitions of DED have been used, discrepancies exist between the various definitions of dry eye disease (DED) used across the globe. This article presents a clinical consensus on the definition of DED, as formulated in four meetings with global DED experts. The proposed new definition is as follows: “Dry eye is a multifactorial disease characterized by a persistently unstable and/or deficient tear film (TF) causing discomfort and/or visual impairment, accompanied by variable degrees of ocular surface epitheliopathy, inflammation and neurosensory abnormalities.” The key criteria for the diagnosis of DED are unstable TF, inflammation, ocular discomfort and visual impairment. This definition also recommends the assessment of ocular surface epitheliopathy and neurosensory abnormalities in each patient with suspected DED. It is easily applicable in clinical practice and should help practitioners diagnose DED consistently. This consensus definition of DED should also help to guide research and clinical trials that, to date, have been hampered by the lack of an established surrogate endpoint.  相似文献   
100.
This article focuses on the consensus problem of leader-following fractional-order multi-agent systems (MASs) with general linear and Lipschitz nonlinear dynamics. First, the distributed adaptive protocols for linear and nonlinear fractional-order MASs are constructed, respectively. We allow the control coupling gains to be time varying for each agent. Moreover, the adaptive modification schemes for the control gain are designed, which renders smaller control gains and thus requires smaller amplitude on the control input without sacrificing consensus convergence. Second, based on fractional-order Lyapunov stability theorem and Barbalat's lemma, two novel sufficient conditions in terms of linear matrix inequalities are provided to ensure that the leader-following consensus can be obtained in the case for any undirected connected communication graph. Furthermore, we show that the proposed algorithm also works for consensus of agents with intrinsic Lipschitz nonlinear dynamics. As a result, the proposed framework requires no global information and thus can be implemented in a fully distributed manner. Finally, the numerical simulations are given to demonstrate the effectiveness of obtained the theoretical results.  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