全文获取类型
收费全文 | 159237篇 |
免费 | 15623篇 |
国内免费 | 9235篇 |
专业分类
电工技术 | 15438篇 |
技术理论 | 17篇 |
综合类 | 14509篇 |
化学工业 | 20852篇 |
金属工艺 | 8808篇 |
机械仪表 | 8162篇 |
建筑科学 | 28101篇 |
矿业工程 | 5408篇 |
能源动力 | 14733篇 |
轻工业 | 6970篇 |
水利工程 | 3668篇 |
石油天然气 | 6397篇 |
武器工业 | 1461篇 |
无线电 | 10454篇 |
一般工业技术 | 17088篇 |
冶金工业 | 7136篇 |
原子能技术 | 1757篇 |
自动化技术 | 13136篇 |
出版年
2024年 | 845篇 |
2023年 | 2911篇 |
2022年 | 5016篇 |
2021年 | 5521篇 |
2020年 | 5680篇 |
2019年 | 4835篇 |
2018年 | 4317篇 |
2017年 | 5286篇 |
2016年 | 5735篇 |
2015年 | 5860篇 |
2014年 | 10341篇 |
2013年 | 9235篇 |
2012年 | 11150篇 |
2011年 | 12475篇 |
2010年 | 9644篇 |
2009年 | 10143篇 |
2008年 | 9162篇 |
2007年 | 10508篇 |
2006年 | 9038篇 |
2005年 | 7514篇 |
2004年 | 6227篇 |
2003年 | 5498篇 |
2002年 | 4749篇 |
2001年 | 3993篇 |
2000年 | 3425篇 |
1999年 | 2805篇 |
1998年 | 2212篇 |
1997年 | 1830篇 |
1996年 | 1484篇 |
1995年 | 1205篇 |
1994年 | 1124篇 |
1993年 | 786篇 |
1992年 | 679篇 |
1991年 | 571篇 |
1990年 | 469篇 |
1989年 | 346篇 |
1988年 | 274篇 |
1987年 | 174篇 |
1986年 | 126篇 |
1985年 | 164篇 |
1984年 | 133篇 |
1983年 | 102篇 |
1982年 | 133篇 |
1981年 | 53篇 |
1980年 | 100篇 |
1979年 | 39篇 |
1978年 | 23篇 |
1977年 | 16篇 |
1959年 | 15篇 |
1951年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
M. J. O'sullivan 《国际能源研究杂志》1985,9(3):319-332
This paper is intended to be a state of the art review of geothermal reservoir simulation. Its recent application to the modelling of real geothermal reservoirs is described and put in the context of an emerging general approach to reservoir modelling. The use of computer simulation for geothermal well test analysis is described. One of the main recent uses of reservoir simulators has been for conducting numerical experiments aimed at improving the understanding of geothermal reservoir physics. Such studies on fractured reservoirs, the thermal structure of reservoirs and the effects of non-condensable gases and dissolved salts are outlined. 相似文献
92.
V. G. Khoruzhaya K. E. Kornienko P. S. Martsenyuk T. Ya. Velikanova 《Powder Metallurgy and Metal Ceramics》2006,45(5-6):251-258
Methods of differential thermal analysis, x-ray diffraction, microstructural analysis and electron probe microanalysis are
used to study alloys of the Al-Rh system over the whole concentration range. It is established that the phase of equiatomic
composition AlRh melts congruently at 2060°C and it has an extended range of homogeneity (45.1–54.2 at.% Rh). The solubility
of aluminum in rhodium reaches 9 at.%, decreasing to 6 at.% at 850°C. Coordinates are determined for the eutectic point l
⇆ AlRh + 〈Rh〉 as 70 at.% Rh and 1715°C. The existence of intermediate phases, their crystal structure, and also the method
of forming phases in the field of composition rich in aluminum given in publications are confirmed.
__________
Translated from Poroshkovaya Metallurgiya, Nos. 5–6(449), pp. 48–56, May–June, 2006. 相似文献
93.
94.
Colin Hines 《Energy Policy》1985,13(2):188-189
This communication illustrates the work of the London Energy and Employment Network. LEEN has the twin aims of promoting a rational energy policy for London and, in the process, generating much needed employment. In cooperation with Hackney, one of Britain's poorest boroughs, LEEN organized Hackney's Cold War — a series of initiatives showing the practical measures, informational back-up and funding sources necessary for a local energy policy. LEEN intends to repeat this project in other London Boroughs, with the eventual aim of helping to persuade central government to adopt a more comprehensive approach to energy conservation nationally. 相似文献
95.
侯向升 《河北工程技术高等专科学校学报》2007,(2):14-16
医院建筑能耗高,如在设计阶段对建筑、供暖与通风、给排水、电器照明等各环节进行节能设计,可以起到事半功倍的效果.文中结合工程实践,提出了各种具体节能措施. 相似文献
96.
Wei Hui 《Frontiers of Computer Science in China》2007,1(3):361-372
Almost all applications of Artificial Neural Networks (ANNs) depend mainly on their memory ability. The characteristics of
typical ANN models are fixed connections, with evolved weights, globalized representations, and globalized optimizations,
all based on a mathematical approach. This makes those models to be deficient in robustness, efficiency of learning, capacity,
anti-jamming between training sets, and correlativity of samples, etc. In this paper, we attempt to address these problems
by adopting the characteristics of biological neurons in morphology and signal processing. A hierarchical neural network was
designed and realized to implement structure learning and representations based on connected structures. The basic characteristics
of this model are localized and random connections, field limitations of neuron fan-in and fan-out, dynamic behavior of neurons,
and samples represented through different sub-circuits of neurons specialized into different response patterns. At the end
of this paper, some important aspects of error correction, capacity, learning efficiency, and soundness of structural representation
are analyzed theoretically. This paper has demonstrated the feasibility and advantages of structure learning and representation.
This model can serve as a fundamental element of cognitive systems such as perception and associative memory. 相似文献
97.
98.
A compact dipole antenna for the terrestrial digital multimedia broadcasting (TDMB) application is presented. The length of the antenna is about 0.06λ at the TDMB resonance frequency of 190 MHz. Miniaturization of the antenna is achieved by using meander structures and lumped elements. The proposed antenna has two resonance frequencies and covers the TDMB band from 174 MHz to 216 MHz in Korea. The antenna has good impedance bandwidth and radiation characteristics for the TDMB. The experimental results of the designed dipole antenna are presented and analyzed. 相似文献
99.
An optimal control problem with nonsmooth performance criterion described by a system of ordinary differential equations is considered. Necessary first-order optimality conditions are obtained. 相似文献
100.
Gregory S. Ho Chen Huang Emily A. Carter 《Current Opinion in Solid State & Materials Science》2007,11(5-6):57-61
Orbital-free density functional theory (OF-DFT) can be made to scale linearly with sample size, allowing thousands of atoms to be treated explicitly with quantum mechanics. State-of-the-art kinetic energy density functionals and ion–electron pseudopotentials are used to obtain accurate structural property predictions for nanoparticles, nanowires, extended surfaces, and nanoindentation of simple metals. 相似文献