全文获取类型
收费全文 | 96222篇 |
免费 | 1863篇 |
国内免费 | 513篇 |
专业分类
电工技术 | 963篇 |
综合类 | 2375篇 |
化学工业 | 14735篇 |
金属工艺 | 5086篇 |
机械仪表 | 3466篇 |
建筑科学 | 2655篇 |
矿业工程 | 580篇 |
能源动力 | 2038篇 |
轻工业 | 4791篇 |
水利工程 | 1410篇 |
石油天然气 | 560篇 |
武器工业 | 4篇 |
无线电 | 10498篇 |
一般工业技术 | 18614篇 |
冶金工业 | 3102篇 |
原子能技术 | 343篇 |
自动化技术 | 27378篇 |
出版年
2024年 | 71篇 |
2023年 | 274篇 |
2022年 | 591篇 |
2021年 | 903篇 |
2020年 | 759篇 |
2019年 | 826篇 |
2018年 | 15099篇 |
2017年 | 13953篇 |
2016年 | 10624篇 |
2015年 | 1074篇 |
2014年 | 972篇 |
2013年 | 1565篇 |
2012年 | 3981篇 |
2011年 | 10251篇 |
2010年 | 8842篇 |
2009年 | 6098篇 |
2008年 | 7149篇 |
2007年 | 8083篇 |
2006年 | 410篇 |
2005年 | 1393篇 |
2004年 | 1294篇 |
2003年 | 1322篇 |
2002年 | 655篇 |
2001年 | 188篇 |
2000年 | 266篇 |
1999年 | 136篇 |
1998年 | 189篇 |
1997年 | 144篇 |
1996年 | 141篇 |
1995年 | 77篇 |
1994年 | 63篇 |
1993年 | 67篇 |
1992年 | 57篇 |
1991年 | 62篇 |
1990年 | 40篇 |
1989年 | 32篇 |
1988年 | 35篇 |
1986年 | 34篇 |
1968年 | 45篇 |
1967年 | 34篇 |
1966年 | 42篇 |
1965年 | 44篇 |
1963年 | 28篇 |
1960年 | 30篇 |
1959年 | 35篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1956年 | 34篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
221.
The low melting point metallic tin powder or alloy of tin and lead was blended with polypropy-lene. A kind of in situ composite has been prepared. The variations of torque were studied when the composites were mixed in Haake torque rheogeniometer. By way of capillary extrusion, effects upon rheology of the in situ com-posites of the low melting point metals (LMPM) and coupling agent for their different variety and content, were investigated. From flow curves, the results indicate that in situ composites mixed with the LMPM are a kind of pseudoplastic fluid. If the LMPM were melted, the higher the content of the LMPM , the lower apparent viscosity of composites. Meanwhile, when the coupling agent is added into composites, the viscosity of composite will go up first and drop then. This shows that the LMPM have a promoter flow action on the polypropylene. 相似文献
222.
We present some sufficient and necessary conditions for convergent splitting of a non-Hermitian indefinite matrix. Some sufficient
conditions to determinate a matrix with a (strongly) dominant symmetric part for a class of boundary value problem are also
obtained. These results are applicable to identify the convergence of iterative methods for solving large sparse systems of
linear equations. 相似文献
223.
Sheen D.M. Ali S.M. Oates D.E. Withers R.S. Kong J.A. 《Applied Superconductivity, IEEE Transactions on》1991,1(2):108-115
A method for the calculation of the current distribution, resistance, and inductance matrices for a system of coupled superconducting transmission lines having finite rectangular cross-section is presented. These calculations allow accurate characterization of both high-T c and low-T c superconducting strip transmission lines. For a single stripline geometry with finite ground planes, the current distribution, resistance, inductance, and kinetic inductance are calculated as functions of the penetration depth for various film thicknesses. These calculations are then used to determine the penetration depth for Nb, NbN, and YBa2Cu3O7-x superconducting thin films from the measured temperature dependence of the resonant frequency of a stripline resonator. The calculations are also used to convert measured temperature dependence of the quality factor to the intrinsic surface resistance as a function of temperature for an Nb stripline resonator 相似文献
224.
An analysis using maximum power-density criteria has been carried out for an endoreversible Carnot heat engine. The results have been compared with known results on maximum power analysis. The design parameters at maximum power density lead to smaller and more efficient endoreversible Carnot heat engines than those working at maximum power output. 相似文献
225.
226.
Keng Siau 《Requirements Engineering》2007,12(4):199-201
227.
228.
Phase-change read-and-write memory (PRAM) is a promising memory that can solve the problems of conventional memory—scalability, read/write speed, and reliability. We will review the opportunities and technical challenges of PRAM. The most important challenge of PRAM is the reduction of the writing current. Various approaches to reduce the writing current will be reviewed and the prospects of PRAM are discussed. 相似文献
229.
230.
Feature-based classifiers for design optimization 总被引:1,自引:0,他引:1
We present a design optimization method for systems with high-dimensional parameter spaces using inductive decision trees.
The essential idea is to map designs into a relatively low-dimensional feature space, and to derive a classifier to search
for high-performing design alternatives within this space. Unlike learning classifier systems that were pioneered by Holland
and Goldberg, classifiers defined by inductive decision trees were not originally developed for design optimization. In this
paper, we explore modifications to such classifiers to make them more effective in the optimization problem. We expand the
notions of feature space, generalize the tree construction heuristic beyond the original information-theoretic definitions,
increase the reliance on domain expertise, and facilitate the transfer of design knowledge between related systems. There
is a relatively small but rapidly growing body of work in the use of inductive trees for engineering design; the method presented
herein is complementary to this research effort. 相似文献