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   22511篇
  免费   2274篇
  国内免费   903篇
电工技术   1558篇
技术理论   3篇
综合类   3214篇
化学工业   2271篇
金属工艺   727篇
机械仪表   1578篇
建筑科学   1665篇
矿业工程   1557篇
能源动力   668篇
轻工业   814篇
水利工程   686篇
石油天然气   891篇
武器工业   396篇
无线电   1771篇
一般工业技术   2672篇
冶金工业   738篇
原子能技术   177篇
自动化技术   4302篇
  2025年   138篇
  2024年   396篇
  2023年   399篇
  2022年   526篇
  2021年   725篇
  2020年   860篇
  2019年   737篇
  2018年   685篇
  2017年   788篇
  2016年   900篇
  2015年   823篇
  2014年   1235篇
  2013年   1372篇
  2012年   1550篇
  2011年   1515篇
  2010年   1179篇
  2009年   1293篇
  2008年   1180篇
  2007年   1378篇
  2006年   1250篇
  2005年   1047篇
  2004年   879篇
  2003年   801篇
  2002年   663篇
  2001年   563篇
  2000年   508篇
  1999年   365篇
  1998年   295篇
  1997年   302篇
  1996年   216篇
  1995年   189篇
  1994年   165篇
  1993年   124篇
  1992年   132篇
  1991年   87篇
  1990年   89篇
  1989年   53篇
  1988年   52篇
  1987年   25篇
  1986年   24篇
  1985年   16篇
  1984年   17篇
  1983年   10篇
  1982年   16篇
  1981年   20篇
  1980年   10篇
  1978年   9篇
  1966年   9篇
  1964年   14篇
  1963年   9篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
This paper describes an approach, conceptual framework, and software architecture for dynamic reconfiguration of the order picking system. The research and development project was sponsored by the Material Handling Research Center (MHRC), a National Science Foundation sponsored Cooperative Industry/University Research Center. The storage configuration is assumed to be an in-the-aisle order picking system in which stockkeeping units (SKUs) can occupy variable capacity storage locations and stock-splitting is allowed among zones (clusters). The product mix may include multiple product families with different life cycles, correlated demand within families and commonality of demand across families.  相似文献   
2.
A specially designed tube viscometer was used to measure apparent viscosity during flow of Bologna type sausage emulsions moving through a pipe. Emulsions varied in fat content (from 21.8 to 44.3%) and in moisture/protein ratio (from 3.7 to 5.6), and the effects of added sodium chloride, sodium diphosphate, starch and blood plasma were investigated in a 36% fat, 3.7 moisture/protein emulsion.
The shear stresses determined as a function of shear rate were fitted by a power law. Yield stress of the emulsions was negligible relative to the applied stress. However, inspection of the flow profiles indicated that considerable slip of the sausage emulsion occurred at the pipe wall. Both emulsion flow and slip contribute to overall flow behaviour, so a kind of effective viscosity is determined. Intrinsic rheological properties and wall slip will both be affected by the composition of the sausage emulsion.  相似文献   
3.
Recombinant cytochrome b5 was extracted into the reversed micelle phase of an anionic surfactant (AOT) in octane and back-extracted to a final aqueous phase. The extraction of the protein was controlled by an electrostatic mechanism, since it was dependent on the global charge of the protein. This was directly demonstrated by experiments with native and mutant cytochromes obtained by site directed mutagenesis. The back-extraction of cytochrome b5 to a fresh aqueous phase was decreased by factors that reduced the size of the water pool of the organic phase, such as high salt concentrations (1–2 mol dm?3 NaCl) and low temperatures (4°C), probably because of an increase in a favourable interaction of this protein with the surfactant at closer distances.  相似文献   
4.
国外关于Zipf定律的实证研究的区域空间多采用国家层次,而国内关于Zipf定律的实证研究则涉及国家、跨省的经济区及行政省的不同层次,于是这就有可能存在经济区域空间划定是否合理的问题。现以长江三角洲地区为例,通过修正的引力模型计算城市之间的经济联系强度及潜能,以此进行长江三角洲经济区域的空间划定,并在划定的经济区域内进行Zipf定律的实证研究,以验证经济区域空间划定是否合理。研究结果显示了经济区域空间划定的合理性。  相似文献   
5.
视觉检测系统中亮度不均匀背景的一种去除方法   总被引:4,自引:0,他引:4  
刀具形状视觉检测系统中,照明不均匀对测量结果影响很大。针对这种情况,提出了基于二维二阶多项式拟合并去除不均匀背景的方法。遵循最小均方程差原理,给出了二维二阶拟合的矩阵表达式。在编制的程序中,拟合点以人机交互形式由鼠标点击选出,程序自动记录所选点的图象人材与亮度值信息,然后拟合出背景曲面,并以二值图象形式给出去除背景后的目标图象。对一幅光照模型未知的网络图象进行了背景去除,实验结果良好。  相似文献   
6.
In this article, with Ehrenfeucht-Fraïssé games we prove that Δ1Δ0 on BFR, which implies ΔΔ0 on BFR, and thus solve an open problem raised by Albert Atserias in his dissertation (Δ0,Δ1,Δ are fragments of first order logic and BFR is a class of finite sets which in essence is equivalent to a class of finite pure arithmetic structures with built-in BIT predicate).  相似文献   
7.
Inference for Weibull distribution under generalized order statistics   总被引:1,自引:0,他引:1  
Based on generalized order statistics from Weibull distribution the approach of Bayesian and non-Bayesian estimation are discussed. We present a simple and efficient simulational algorithm for generating a generalized order statistics sample from any continuous distribution. Specializations to Bayesian and non-Bayesian estimators, some lifetime parameters and confidence intervals of progressive II censoring and record values are obtained and compared with the existing results. Two examples are given to illustrate the proposed estimators and the simulation algorithm.  相似文献   
8.
9.
For energetic flows there are many advantages of high order schemes over low order schemes. Here we examine a previously unknown advantage. It is commonly thought that the number of points per wavelength in order to obtain a given error in a numerical approximation depends only on runtime and the order of the approximation. Using truncation error arguments and examples we will show that it is not a constant and depends also on the wavenumber. This dependence on the numerical order and wavenumber strongly favors high order schemes for use in flows which have significant energy in the high modes such at Rayleigh–Taylor and Richtmyer–Meshkov instabilities.  相似文献   
10.
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