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   110632篇
  免费   1837篇
  国内免费   506篇
电工技术   1586篇
综合类   2408篇
化学工业   16232篇
金属工艺   6146篇
机械仪表   4792篇
建筑科学   2777篇
矿业工程   896篇
能源动力   1428篇
轻工业   4318篇
水利工程   1699篇
石油天然气   1212篇
武器工业   11篇
无线电   11886篇
一般工业技术   23238篇
冶金工业   5563篇
原子能技术   737篇
自动化技术   28046篇
  2023年   176篇
  2022年   531篇
  2021年   863篇
  2020年   643篇
  2019年   765篇
  2018年   15647篇
  2017年   14574篇
  2016年   11481篇
  2015年   1626篇
  2014年   1730篇
  2013年   2131篇
  2012年   4899篇
  2011年   11042篇
  2010年   9727篇
  2009年   7200篇
  2008年   8320篇
  2007年   9242篇
  2006年   1352篇
  2005年   1978篇
  2004年   1637篇
  2003年   1486篇
  2002年   861篇
  2001年   346篇
  2000年   737篇
  1999年   512篇
  1998年   570篇
  1997年   518篇
  1996年   192篇
  1995年   104篇
  1994年   99篇
  1993年   109篇
  1992年   78篇
  1991年   83篇
  1990年   72篇
  1988年   60篇
  1985年   60篇
  1984年   53篇
  1983年   45篇
  1978年   49篇
  1976年   81篇
  1969年   50篇
  1968年   65篇
  1967年   50篇
  1966年   57篇
  1965年   51篇
  1959年   45篇
  1958年   50篇
  1956年   43篇
  1955年   71篇
  1954年   73篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
Atomic Energy - The results of calculations and experimental determination of the neutronics characteristics of the IRT-T research reactor are presented. The IRT-T reactor is a pool reactor with...  相似文献   
32.
Multimedia Tools and Applications - Text-to-picture systems attempt to facilitate high-level, user-friendly communication between humans and computers while promoting understanding of natural...  相似文献   
33.
The paper concerns an analysis of an equilibrium problem for 2D elastic body with two semirigid inclusions. It is assumed that inclusions have a joint point, and we investigate a junction problem for these inclusions. The existence of solutions is proved, and different equivalent formulations of the problem are proposed. We investigate a convergence to infinity of a rigidity parameter of the semirigid inclusion. It is proved that in the limit, we obtain an equilibrium problem for the elastic body with a rigid inclusion and a semirigid one. A parameter identification problem is investigated. In particular, the existence of a solution to a suitable optimal control problem is proved.  相似文献   
34.
Strength of Materials - The paper addresses the investigation of high-strain rate compressive behavior of Al foams subjected to impact at the intermediate striking velocity ranged from 40 to...  相似文献   
35.
The object of study is nonlinear stationary controlled system of ordinary differential equations with constant disturbance in the right part. The problem of constructing the synthesising control function providing the transfer of this system from the initial state to the origin is considered. The sufficiently simple for numerical implementation algorithm of solution of the above-mentioned problem is obtained. It is shown that for local null controllability of the considered system, it is sufficient that the conditions of the Kalman's type were satisfied. In addition, the estimates restricting the choice of initial conditions and external disturbances under which the transfer is guaranteed are obtained. The main idea of the method of construction of the desired control function consists in reducing the original problem to stabilisation of a special kind linear non-stationary system and solving the Cauchy problem for an auxiliary system of ordinary differential equations closed by stabilising control. The simplicity of the realisation of this algorithm is determined by the construction of the auxiliary system and its stabilisation that could be obtained by analytical methods. The effectiveness of the method is illustrated by solving the problem of crane control and its numerical simulation.  相似文献   
36.
Mobile software applications have to cope with a particular environment that involves small size, limited resources, high autonomy requirements, competitive business models and many other challenges. To provide development guidelines that respond to these needs, several practices have been introduced; however, it is not clear how these guidelines may contribute to solve the issues present in the mobile domain. Furthermore, the rapid evolution of the mobile ecosystem challenges many of the premises upon which the proposed practices were designed. In this paper, we present a survey of the literature on software assurance practices for mobile applications, with the objective of describing them and assessing their contribution and success. We identified, organized and reviewed a body of research that spans in three levels: software development processes, software product assurance practices, and software implementation practices. By carrying out this literature survey, we reviewed the different approaches that researchers on Software Engineering have provided to address the needs that raise in the mobile software development arena. Moreover, we review the evolution of these practices, identifying how the constant changes and modernization of the mobile execution environment has impacted the methods proposed in the literature. Finally, we introduced discussion on the application of these practices in a real productive setting, opening an area for further research that may determine if practitioners have followed the proposed assurance paradigms.  相似文献   
37.
The authors have developed a procedure and a test bench for studying evolution of various nature physical fields in modeling geomedium fracture by fluids. The test bench performs synchronous recording of macro- and micro-deformation, heat and acoustic emission induced in physical models of geomedium under loading to discontinuity. The experimental procedure has been trialed. The analysis of the synchronized test data allows a conclusion on the existence of time–space relationship between different nature physical fields induced during failure of solids.  相似文献   
38.
39.
This paper presents an integrated passive damping approach in hybrid metal-CFRP parts for structural applications. In this concept a viscoelastic material is embedded in the joint zone of the hybrid component. To examine the connection strength single-lap-joint specimens were produced and tested and the influence of the used material combinations, different surface structures, and different process parameters i.e. the moment of cross-linking were evaluated. Afterwards, the metal-CFRP hybrids were tested in quasi-static tests to assess their connection strength and failure behaviour. Dynamic cyclic tensile tests with step-wise increased loading conditions were performed to determine the specimens damping behaviour and to estimate their fatigue performance. Finally, these results are compared to a state of the art metal-CFRP hybrid with rivets connecting both materials.  相似文献   
40.
In this paper, we consider the classical finite mixture model, which is an effective tool for modeling lifetime distributions for random samples from heterogeneous populations. We discuss new results on stochastic comparison for two finite mixtures when each of them is drawn from one of the following semiparametric families, i.e., proportional hazards, accelerated lifetime and proportional reversed hazards.  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