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   10181篇
  免费   4篇
  国内免费   6篇
电工技术   124篇
综合类   9篇
化学工业   215篇
金属工艺   283篇
机械仪表   47篇
建筑科学   26篇
矿业工程   2篇
能源动力   25篇
轻工业   10篇
水利工程   2篇
无线电   297篇
一般工业技术   81篇
冶金工业   1135篇
原子能技术   84篇
自动化技术   7851篇
  2021年   1篇
  2015年   1篇
  2014年   208篇
  2013年   168篇
  2012年   759篇
  2011年   2272篇
  2010年   1101篇
  2009年   956篇
  2008年   680篇
  2007年   575篇
  2006年   439篇
  2005年   567篇
  2004年   513篇
  2003年   573篇
  2002年   272篇
  2001年   3篇
  2000年   1篇
  1999年   34篇
  1998年   257篇
  1997年   163篇
  1996年   113篇
  1995年   72篇
  1994年   62篇
  1993年   78篇
  1992年   15篇
  1991年   22篇
  1990年   18篇
  1989年   24篇
  1988年   23篇
  1987年   18篇
  1986年   18篇
  1985年   12篇
  1983年   3篇
  1982年   8篇
  1981年   16篇
  1980年   9篇
  1978年   3篇
  1977年   38篇
  1976年   93篇
  1975年   1篇
  1972年   1篇
  1965年   1篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
The patterning of contact holes by selecting out-of-focus image plane (defocus) using attenuated phase shift masks (APSM) has been studied. Defocus is found to enhance the image modulation at low partial coherence for contact holes with negative local average of mask function. Semi-dense holes up to 130 nm in 8% APSM have been printed by 0.5 μm defocus at a partial coherence of 0.31 using KrF scanner with highest numerical aperture of 0.68. However, these holes were closed with in-focus imaging. Defocus is also found to be beneficial for patterning the pitches that have extensive side lobes with in-focus imaging.  相似文献   
3.
Leukocyte depletion improves early postischemic ventricular performance in neonatal models of global myocardial ischemia. However, the rate of leukocyte reaccumulation after cardiopulmonary bypass and its subsequent impact on myocardial function is not known. This laboratory study examined the effect of leukocyte depletion on myocardial performance during the initial 6-hour period after bypass in an in situ, in vivo porcine model of neonatal cardiac surgery. Fifteen 3- to 5-day-old piglets (eight control and seven leukocyte depleted animals) were instrumented by placement of left ventricular short-axis sonomicrometry crystals and an intraventricular micromanometer catheter. Mechanical leukocyte depletion was achieved with Pall RC100 filters (Pall Biomedical, Inc., Fajardo, Puerto Rico) in the cardiopulmonary bypass circuit. Neonatal hearts were subjected to 90 minutes of hypothermic ischemia after a single dose of cold crystalloid cardioplegia. Two control animals died after the operation and were excluded from data analysis. Leukocyte filtration reduced the granulocyte count during initial myocardial reperfusion to 0.8% of control values. However, circulating granulocyte counts increased in leukocyte depleted animals throughout the postoperative period, reaching 68% of control values by 6 hours. Despite this rapid return of circulating granulocytes, animals subjected to leukocyte depletion had significantly better preservation of left ventricular performance (measured by preload recruitable stroke work, p < or = 0.02), left ventricular systolic function (measured by end-systolic pressure-volume relationship, p < or = 0.05), and ventricular compliance (p < or = 0.04) during the experiment. These changes in ventricular function were associated with a significant increase in left ventricular water content (p < or = 0.02) and tissue myeloperoxidase activity (p < or = 0.005) in control animals compared with leukocyte depleted animals. This study demonstrates that leukocyte depletion during initial reperfusion results in sustained improvement in postischemic left ventricular function despite the rapid return of granulocytes to the circulation.  相似文献   
4.
5.
Assuming that the chemical reactions used to synthesize a combinatorial library member are successful, then knowledge of the specific reaction sequence is equivalent to knowing the member's chemical identity. Because the determination of chemical identity is typically not automatable and requires a substantial amount of material, schemes that encode a member's reaction history onto the reaction platform are of value. The primary benefits of encoding are relational nomenclature (all methods) and automated handling (some methods). Encoding methods evaluated to date are spatial, graphical, chemical, spectrometric, electronic, and physical.  相似文献   
6.
7.
8.
Adaptive motion control using neural network approximations   总被引:1,自引:0,他引:1  
In this paper, we present a new adaptive technique for tracking control of mechanical systems in the presence of friction and periodic disturbances. Radial Basis Functions (RBFs) are used to compensate for the effects of nonlinearly occurring parameters in the friction and periodic disturbance model. Theoretical analysis, such as stability and transient performance, is provided. Furthermore, the performance of the adaptive RBF controller and its non-adaptive counterpart are compared.  相似文献   
9.
Generally, a reduction operation (e.g., thinning and shrinking) on 3D binary images can be represented as a set of reduction templates where every object voxel of the image satisfying any template is turned to a background voxel. Generally, it is rather difficult, error-prone and time-consuming for verifying the topological soundness of a 3D parallel reduction operation. This paper proposes sufficient conditions of time complexity O(n) for verifying the topological soundness of 3D parallel 6-subiteration reduction operations of n templates where such a kind of 3D reduction operations is performed alternatively from the six orthogonal directions to turn object voxels to background voxels. By such sufficient conditions, the topology soundness of a 3D 6-subiteration parallel reduction operation can be verified by checking each and every of its templates.  相似文献   
10.
In this paper, we present a control methodology for a class of discrete time nonlinear systems that depend on a possibly exogenous scheduling variable. This class of systems consists of an interpolation of nonlinear dynamic equations in strict feedback form, and it may represent systems with a time-varying nonlinear structure. Moreover, this class of systems is able to represent some cases of gain scheduling control, Takagi-Sugeno fuzzy systems, as well as input-output realizations of nonlinear systems which are approximated via localized linearizations. We present two control theorems, one using what we call a “global” approach (akin to traditional backstepping), and a “local” approach, our main result, where backstepping is again used but the control law is an interpolation of local control terms. An aircraft wing rock regulation problem with varying angle of attack is used to illustrate and compare the two approaches.  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