全文获取类型
收费全文 | 151900篇 |
免费 | 1887篇 |
国内免费 | 656篇 |
专业分类
电工技术 | 3115篇 |
综合类 | 187篇 |
化学工业 | 24078篇 |
金属工艺 | 5781篇 |
机械仪表 | 4943篇 |
建筑科学 | 4418篇 |
矿业工程 | 377篇 |
能源动力 | 3929篇 |
轻工业 | 17309篇 |
水利工程 | 1140篇 |
石油天然气 | 618篇 |
武器工业 | 5篇 |
无线电 | 20511篇 |
一般工业技术 | 28852篇 |
冶金工业 | 23755篇 |
原子能技术 | 2341篇 |
自动化技术 | 13084篇 |
出版年
2019年 | 838篇 |
2018年 | 1081篇 |
2017年 | 1132篇 |
2016年 | 1271篇 |
2015年 | 1063篇 |
2014年 | 1796篇 |
2013年 | 6576篇 |
2012年 | 3194篇 |
2011年 | 4609篇 |
2010年 | 3595篇 |
2009年 | 4152篇 |
2008年 | 4650篇 |
2007年 | 4915篇 |
2006年 | 4350篇 |
2005年 | 4109篇 |
2004年 | 4002篇 |
2003年 | 3899篇 |
2002年 | 3930篇 |
2001年 | 3981篇 |
2000年 | 3742篇 |
1999年 | 3691篇 |
1998年 | 6634篇 |
1997年 | 5229篇 |
1996年 | 4461篇 |
1995年 | 3709篇 |
1994年 | 3358篇 |
1993年 | 3186篇 |
1992年 | 2784篇 |
1991年 | 2690篇 |
1990年 | 2628篇 |
1989年 | 2614篇 |
1988年 | 2460篇 |
1987年 | 2166篇 |
1986年 | 2116篇 |
1985年 | 2557篇 |
1984年 | 2316篇 |
1983年 | 2195篇 |
1982年 | 2069篇 |
1981年 | 1991篇 |
1980年 | 1860篇 |
1979年 | 1874篇 |
1978年 | 1770篇 |
1977年 | 2085篇 |
1976年 | 2562篇 |
1975年 | 1583篇 |
1974年 | 1430篇 |
1973年 | 1453篇 |
1972年 | 1196篇 |
1971年 | 1115篇 |
1970年 | 948篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
In this paper, we analyze in some detail the manifold-mapping optimization technique introduced recently [Echeverría and Hemker in space mapping and defect correction. Comput Methods Appl Math 5(2): 107—136, 2005]. Manifold mapping aims at accelerating optimal design procedures that otherwise require many evaluations of time-expensive cost functions. We give a proof of convergence for the manifold-mapping iteration. By means of two simple optimization problems we illustrate the convergence results derived. Finally, the performances of several variants of the method are compared for some design problems from electromagnetics. 相似文献
72.
73.
74.
W. L. Siew F. C. H. Oh A. S. H. Ong 《Journal of the American Oil Chemists' Society》1985,62(6):1036-1039
Some of the factors affecting cloud point determination of palm oleins are described. These are the type of container used, method of stirring, rate of stirring and bath temperature. The repeatability and reproducibility standard deviations of the method are determined from collaborative trials. Recommendations for the test are made to reduce the large variations among laboratories. 相似文献
75.
The main purpose of this study was to evaluate the performance of the electrochemical oxidation process as a post-treatment for the effluents of a bench-scale UASB reactor treating simulated wastewater from an unbleached pulp plant. The oxidation process was performed using a single compartment cell with two plates as electrodes. The anode was made of Ti/Ru0.3Ti0.7O2 and the cathode of stainless steel. The following variables were evaluated: current density (75, 150 and 225 mA cm(-2)) and recirculation flow rate in the electrochemical cell (0.22, 0.45 and 0.90 L h(-1)). The increase in current density from 75 to 225 mA cm(-2) did not increased the color removal efficiency for the tested flow rates, 0.22, 0.45 and 0.90 L h(-1), however the energy consumption increased significantly. The results indicated the technical feasibility of the electrochemical treatment as post-treatment for UASB reactors treating wastewaters from pulp and paper plants. 相似文献
76.
The US Centers for Disease Control and Prevention (CDC) created the Public Health Information Network to advance fully capable, interoperable information systems in public health organizations. PHIN prioritizes public health information systems' functional requirements, capabilities, performance measures, and operational characteristics while letting the architects of those systems choose enabling approaches, methods, and concepts to meet the requirements. PHIN also provides a certification process for public health administrators to evaluate their information infrastructure's quality. The certification process is important because affected organizations often depend on certification for continued funding. 相似文献
77.
78.
The IBM RISC System/6000, a superscalar microprocessor, is presented. The architecture of this processor has its instruction set specifically designed for a superscalar machine containing three independent units-branch, fixed-point, and floating-point. The design also emphasizes high-performance floating-point operations. The design principles are to offer maximum overlap of the three functional units, avoid dead cycles, and define instructions that can (for the most part) be completed at a rate of one per cycle. The branch cycle, fixed- and floating-point units, cache management, and performance are described. Benchmark results are given 相似文献
79.
A Rate-Control vaginal device was developed which overcomes the low bioavailability and unpredictable Q - t1/2 type release and absorption rate profiles of flurogestone acetate delivered by the currently marketed Syncro-Mate pessary.
The in vitro release and vaginal absorption profiles from the Rate-Control vaginal device were run simultaneously, a linear Q - t relationship was obtained with a significant improvement in bioavailability. A mathematical model was developed to correlate the in vitro drug release and the vaginal absorption profiles of flurogestone acetate from the vaginal devices.
The design, development and the simultaneous release and absorption profiles of flurogestone acetate from this new vaginal device were outlined and discussed. 相似文献
The in vitro release and vaginal absorption profiles from the Rate-Control vaginal device were run simultaneously, a linear Q - t relationship was obtained with a significant improvement in bioavailability. A mathematical model was developed to correlate the in vitro drug release and the vaginal absorption profiles of flurogestone acetate from the vaginal devices.
The design, development and the simultaneous release and absorption profiles of flurogestone acetate from this new vaginal device were outlined and discussed. 相似文献
80.
Ion-beam sputter-deposited alloy films of Co/sub 74/Fe/sub 6/B/sub 15/Si/sub 5/ and Fe/sub 75/Ni/sub 5/B/sub 15/Si/sub 5/ were examined for their magnetic and structural properties. Films were characterized by ferromagnetic resonance, vibrating sample magnetometry, and extended X-ray absorption fine structure (EXAFS) analysis. Using atomic parameters deduced from EXAFS modeling and fitting procedures, magnetic properties were calculated with no adjustable parameters. Correlation between perpendicular FMR measurements and EXAFS first-shell modeling suggests a low-temperature formation of cobalt-borides in the Co/sub 74/Fe/sub 6/B/sub 15/Si/sub 5/ alloy. Annealed Fe/sub 75/Ni/sub 5/B/sub 15/Si/sub 5/ samples did not display evidence of structural and/or magnetic instabilities until the onset of long-range crystallization near T/sub ann/=400 degrees C.<> 相似文献