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   9006篇
  免费   984篇
  国内免费   10篇
电工技术   69篇
综合类   5篇
化学工业   2396篇
金属工艺   101篇
机械仪表   289篇
建筑科学   439篇
矿业工程   20篇
能源动力   215篇
轻工业   1980篇
水利工程   72篇
石油天然气   18篇
无线电   682篇
一般工业技术   1744篇
冶金工业   389篇
原子能技术   23篇
自动化技术   1558篇
  2024年   35篇
  2023年   140篇
  2022年   113篇
  2021年   325篇
  2020年   270篇
  2019年   270篇
  2018年   347篇
  2017年   354篇
  2016年   464篇
  2015年   419篇
  2014年   545篇
  2013年   994篇
  2012年   859篇
  2011年   647篇
  2010年   472篇
  2009年   465篇
  2008年   491篇
  2007年   424篇
  2006年   393篇
  2005年   248篇
  2004年   228篇
  2003年   195篇
  2002年   192篇
  2001年   121篇
  2000年   120篇
  1999年   87篇
  1998年   69篇
  1997年   68篇
  1996年   62篇
  1995年   59篇
  1994年   59篇
  1993年   50篇
  1992年   34篇
  1991年   29篇
  1990年   18篇
  1989年   19篇
  1988年   21篇
  1987年   10篇
  1986年   16篇
  1985年   22篇
  1984年   22篇
  1983年   15篇
  1982年   17篇
  1981年   18篇
  1980年   17篇
  1979年   24篇
  1978年   12篇
  1974年   10篇
  1973年   11篇
  1947年   9篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
Quantification of different effects (nonlinearity, heating, thixotropy, and fatigue) occurring during fatigue tests on bituminous mixtures is presented in this paper. A focus is given on the nonlinearity phenomenon. Continuous fatigue tests and a test with specific protocol (called fatigue tests to estimate biasing effects) were performed in tension/compression mode on cylindrical samples of the same material. The analysis of results reveals that reversible effects (nonlinearity, heating, and thixotropy) are important (more than 90% decrease at 100,000 cycles for a strain amplitude of 100 μm/m at 10 Hz) and cannot be ignored when interpreting classical fatigue tests. The nonlinearity effects respect the time‐temperature superposition principle, and they are more pronounced at “high” temperature (at the same frequency). Direction of nonlinearity curve in the Cole‐Cole axes is shown to be independent of temperature and frequency for the considered range.  相似文献   
152.
153.
The equations that govern Kirchhoff–Love plate theory are solved using quadratic Powell–Sabin B‐splines and unstructured standard T‐splines. Bézier extraction is exploited to make the formulation computationally efficient. Because quadratic Powell–Sabin B‐splines result in ‐continuous shape functions, they are of sufficiently high continuity to capture Kirchhoff–Love plate theory when cast in a weak form. Unlike non‐uniform rational B‐splines (NURBS), which are commonly used in isogeometric analysis, Powell–Sabin B‐splines do not necessarily capture the geometry exactly. However, the fact that they are defined on triangles instead of on quadrilaterals increases their flexibility in meshing and can make them competitive with respect to NURBS, as no bending strip method for joined NURBS patches is needed. This paper further illustrates how unstructured T‐splines can be modified such that they are ‐continuous around extraordinary points, and that the blending functions fulfil the partition of unity property. The performance of quadratic NURBS, unstructured T‐splines, Powell–Sabin B‐splines and NURBS‐to‐NURPS (non‐uniform rational Powell–Sabin B‐splines, which are obtained by a transformation from a NURBS patch) is compared in a study of a circular plate. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
154.
The aqueous-core enclosed in lipid nanoballoons integrating multiple emulsions of the type water-in-oil-in-water mimic, at least in theory, the environment within viable cells, thus being suitable for housing hydrophilic protein entities such as bioactive proteins, peptides and bacteriophage particles. This study reports a complete physicochemical characterization of optimized biomimetic aqueous-core lipid nanoballoons housing hydrophilic (BSA) protein entities, evolved from a statistical 23×31 factorial design study (three variables at two levels and one variable at three levels) that was the subject of the first paper of a series of three, aiming at complete stabilization of the three-dimensional structure of protein entities attempted via housing the said molecular entities within biomimetic aqueous-core lipid nanoballoons integrating a multiple (W/O/W) emulsion. The statistical factorial design followed led to the production of an optimum W/O/W multiple emulsion possessing quite homogeneous particles with an average hydrodynamic size of (186.2?±?2.6) nm and average Zeta potential of (?36.5?±?0.9) mV, and exhibiting a polydispersity index of 0.206?±?0.014. Additionally, the results obtained for the diffusion coefficient of the lipid nanoballoons integrating the optimized W/O/W multiple emulsion were comparable and of the same order of magnitude (10?12 m2 s?1) as those published by other authors since, typically, diffusion coefficients for molecules range from 10?10 to 10?7 m2 s?1, but diffusion coefficients for nanoparticles are typically of the order of magnitude of 10?12 m2 s?1.  相似文献   
155.
Although new technologies allow for less effort in prototyping, physical testing still remains an important step in the product development cycle. Well‐planned experiments are useful to guide the decision‐making process. During the design of an experiment, one of the challenges is to balance limited resources and system constraints to obtain useful information. It is common that prototypes are composed of several parts, with some parts more difficult to assemble than others. And, usually, there is only one piece available of each part type and a large number of different setups. Under these conditions, designs with randomization restrictions become attractive approaches. Considering this scenario, a new and additional criterion, minimum setup, to construct split‐plot type designs is presented. Designs with the minimum number of setups of the more difficult parts, which are especially useful for screening purposes in physical prototype testing, are discussed. The use of the proposed criterion combined with minimum aberration for selecting a regular design is shown through a real application in testing car prototypes. As a tool to practitioners, catalogs of selected 32‐run minimum setup minimum aberration split‐split‐plot and split‐split‐split‐plot designs are presented. More complete catalogs are available as Supporting information. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
156.
157.
158.
159.
160.
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