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   11443篇
  免费   49篇
  国内免费   1篇
电工技术   134篇
综合类   1篇
化学工业   515篇
金属工艺   371篇
机械仪表   104篇
建筑科学   124篇
矿业工程   10篇
能源动力   74篇
轻工业   170篇
水利工程   19篇
石油天然气   7篇
无线电   414篇
一般工业技术   413篇
冶金工业   941篇
原子能技术   96篇
自动化技术   8100篇
  2021年   14篇
  2020年   11篇
  2019年   10篇
  2018年   25篇
  2017年   20篇
  2016年   29篇
  2015年   25篇
  2014年   231篇
  2013年   253篇
  2012年   818篇
  2011年   2344篇
  2010年   1153篇
  2009年   987篇
  2008年   724篇
  2007年   648篇
  2006年   516篇
  2005年   620篇
  2004年   576篇
  2003年   636篇
  2002年   343篇
  2001年   45篇
  2000年   48篇
  1999年   68篇
  1998年   219篇
  1997年   135篇
  1996年   98篇
  1995年   65篇
  1994年   64篇
  1993年   78篇
  1992年   29篇
  1991年   21篇
  1990年   36篇
  1989年   30篇
  1988年   35篇
  1987年   35篇
  1986年   30篇
  1985年   30篇
  1984年   37篇
  1983年   35篇
  1982年   32篇
  1981年   32篇
  1980年   17篇
  1979年   21篇
  1978年   27篇
  1977年   26篇
  1976年   46篇
  1975年   23篇
  1974年   17篇
  1973年   20篇
  1972年   19篇
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
81.
In this introduction to a special issue of Computers and Composition, the authors critically review current literature on computer-assisted writing pedagogies that grapple with issues of sexuality. Although this body of work is small, it points to provocative ways to develop our students’ critical and rhetorical sensibilities about the constructions of sexuality in our culture. Further, such work innovatively addresses the place of networked communication technologies in the interrogation of such constructions. The authors conclude with both an introduction of the work in this special issue that addresses the intersection of sexuality studies and computer-assisted writing studies and with a call for additional work in this field.  相似文献   
82.
The aim of this paper is to analyze the feasibility of ultrathin packages through the electrical qualification of the technological process used, i.e. mechanical lapping. It considers polysilicon bipolar transistors which thickness can reach values lower than 10 μm. Forward mode and reverse mode characterizations show no significant degradation of pertinent characteristics, thus allowing to find applications in new compact packaging concept.  相似文献   
83.
84.
Parametric interpolation has many advantages over linear interpolation in machining curves. Real time parametric interpolation research so far has addressed achieving a uniform feed rate, confined chord errors and jerk limited trajectory planning. However, simultaneous consideration of confined chord errors that respect the acceleration and deceleration capabilities of the machine has not been attempted. In this paper, the offline detection of feed rate sensitive corners is proposed. The velocity profile in these zones is planned so that chord errors are satisfied while simultaneously accommodating the machine's acceleration and deceleration limits. Outside the zone of the feed rate sensitive corners, the feed rate is planned using the Taylor approximation. Simulation results indicate that the offline detection of feed rate sensitive corners improves parametric interpolation. For real time interpolation, the parametric curve information can be augmented with the detected feed rate sensitive corners that are stored in 2×2 matrices.  相似文献   
85.
The increasing use of virtual reality (VR) simulators in surgical training makes it imperative that definitive studies be performed to assess their training effectiveness. Indeed in this paper we report the meta-analysis of the efficacy of virtual reality simulators in (1) the transference of skills from the simulator training environment to the operating room and (2) their ability to discriminate between the experience levels of its users. The task completion time and the error score were the two study outcomes collated and analyzed in this meta-analysis. Sixteen studies were identified from a computer-based literature search (1996-2004). The meta-analysis of the random-effects model (because of the heterogeneity of the data) revealed that training on virtual reality simulators did lessen the time taken to complete a given surgical task as also clearly differentiate between the experienced and the novice trainees. Meta-analytic studies such as the one reported here would be very helpful in the planning and setting up of surgical training programs and for the establishment of reference ‘learning curves’ for a specific simulator and surgical task. If any such programs already exist they can then indicate the improvements to be made in the simulator used such as providing for more variety in their case scenarios based on the state and/or rate of learning of the trainee.  相似文献   
86.
Given a nonlinear system and a performance index to be minimized, we present a general approach to expressing the finite time optimal feedback control law applicable to different types of boundary conditions. Starting from the necessary conditions for optimality represented by a Hamiltonian system, we solve the Hamilton-Jacobi equation for a generating function for a specific canonical transformation. This enables us to obtain the optimal feedback control for fundamentally different sets of boundary conditions only using a series of algebraic manipulations and partial differentiations. Furthermore, the proposed approach reveals an insight that the optimal cost functions for a given dynamical system can be decomposed into a single generating function that is only a function of the dynamics plus a term representing the boundary conditions. This result is formalized as a theorem. The whole procedure provides an advantage over methods rooted in dynamic programming, which require one to solve the Hamilton-Jacobi-Bellman equation repetitively for each type of boundary condition. The cost of this favorable versatility is doubling the dimension of the partial differential equation to be solved.  相似文献   
87.
88.
89.
Poly(ethylene oxide) (PEO) oligomers are employed extensively in pharmaceutical and biomedical arenas mainly due to their excellent physical and biological properties, including solubility in water and organic solvents, lack of toxicity, and absence of immunogenicity. PEO can be chemically modified and reacted with, or adsorbed onto, other molecules and surfaces. Sophisticated applications for PEO have increased the demand for PEO oligomers with tailored functionalities, and heterobifunctional PEOs are often needed. This review discusses the synthesis and applications of heterobifunctional PEO oligomers possessing amine, carboxylate, thiol, and maleimide functional groups.  相似文献   
90.
It may be a truism to say that round powders pack better, but spheroidisation of powder particles is one of the successful commercial applications of induction plasma technology and can play a key role in substantial improvement of powder quality and fluidity…  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