全文获取类型
收费全文 | 574162篇 |
免费 | 3526篇 |
国内免费 | 785篇 |
专业分类
电工技术 | 10608篇 |
综合类 | 510篇 |
化学工业 | 90829篇 |
金属工艺 | 23373篇 |
机械仪表 | 18558篇 |
建筑科学 | 12635篇 |
矿业工程 | 4317篇 |
能源动力 | 14618篇 |
轻工业 | 46662篇 |
水利工程 | 7166篇 |
石油天然气 | 15016篇 |
武器工业 | 39篇 |
无线电 | 60893篇 |
一般工业技术 | 116969篇 |
冶金工业 | 95645篇 |
原子能技术 | 14711篇 |
自动化技术 | 45924篇 |
出版年
2021年 | 5758篇 |
2020年 | 4487篇 |
2019年 | 5813篇 |
2018年 | 9251篇 |
2017年 | 9456篇 |
2016年 | 10064篇 |
2015年 | 6132篇 |
2014年 | 10347篇 |
2013年 | 26220篇 |
2012年 | 15875篇 |
2011年 | 21195篇 |
2010年 | 17059篇 |
2009年 | 18914篇 |
2008年 | 19162篇 |
2007年 | 18849篇 |
2006年 | 16368篇 |
2005年 | 14834篇 |
2004年 | 14062篇 |
2003年 | 13743篇 |
2002年 | 13300篇 |
2001年 | 12885篇 |
2000年 | 12357篇 |
1999年 | 12052篇 |
1998年 | 27683篇 |
1997年 | 20073篇 |
1996年 | 15668篇 |
1995年 | 12037篇 |
1994年 | 10889篇 |
1993年 | 10643篇 |
1992年 | 8355篇 |
1991年 | 8122篇 |
1990年 | 8015篇 |
1989年 | 7780篇 |
1988年 | 7493篇 |
1987年 | 6754篇 |
1986年 | 6537篇 |
1985年 | 7399篇 |
1984年 | 6703篇 |
1983年 | 6446篇 |
1982年 | 5780篇 |
1981年 | 5896篇 |
1980年 | 5637篇 |
1979年 | 5736篇 |
1978年 | 5666篇 |
1977年 | 6181篇 |
1976年 | 7688篇 |
1975年 | 5108篇 |
1974年 | 4903篇 |
1973年 | 4980篇 |
1972年 | 4279篇 |
排序方式: 共有10000条查询结果,搜索用时 29 毫秒
121.
This paper presents a valve-regulated lead acid (VRLA) battery reserve life estimation scheme. The scheme is adaptive in both type and frequency of involvement. The scheme is based on capacity trending with the support of a number of state-of-health (SOH) indicators. These SOH indicators include accumulated thermal stress, float voltage, and indicators acquired from the start-of-discharge (coup de fouet) region. An implementation test case is given, indicating that the scheme is capable of providing an accurate estimation of reserve life long before the end of life. Furthermore, the estimation accuracy improves as the end of battery life approaches. 相似文献
122.
123.
The photoelectric parameters of silicon solar cells degraded under the action of 60Co gamma-radiation can be partly restored using an ultrasonic treatment (UST). The growth of the maximum output power of solar cells after the UST is related to a redistribution of the radiation defects and an increase in the homogeneity of a semiconductor crystal structure. 相似文献
124.
Tomer A. Goldin L. Kuflik T. Kimchi E. Schach S.R. 《IEEE transactions on pattern analysis and machine intelligence》2004,30(9):601-612
We propose a model that enables software developers to systematically evaluate and compare all possible alternative reuse scenarios. The model supports the clear identification of the basic operations involved and associates a cost component with each basic operation in a focused and precise way. The model is a practical tool that assists developers to weigh and evaluate different reuse scenarios, based on accumulated organizational data, and then to decide which option to select in a given situation. The model is currently being used at six different companies for cost-benefit analysis of alternative reuse scenarios; we give a case study that illustrates how it has been used in practice. 相似文献
125.
We consider probability-theoretic and statistical models and methods for computing the characteristics of dictionary structures. Results of a statistical analysis of several commonly used dictionaries are presented in order to test the adequacy of the computing methods proposed. 相似文献
126.
S. M. Obraztsov G. A. Birzhevoi Yu. V. Konobeev V. A. Solov'ev O. S. Silkina 《Atomic Energy》2004,96(2):111-116
The results of a computational experiment with a neural-net model simulating the effect of the chemical composition on the plastic properties of ÉP-450 steel are presented. It is shown that computer-aided development of reactor steel with prescribed properties is, in principle, possible. 相似文献
127.
Electrophoretic deposition of electrolyte materials for solid oxide fuel cells, including La0.8Sr0.2Ga0.875Mg0.125O3–x
, yttria stabilized zirconia and (Ce0.8Gd0.2)O1.9, was studied under various experimental conditions. The use of phosphate ester as a dispersant and poly (vinyl butyral) as a binder enabled high deposition rate and formation of crack-free, adherent deposits. Electrodeposition rates were quantified in experiments performed at constant current and constant voltage modes from suspensions in ethanol, isopropanol and mixed ethanol—isopropanol solvents. The microstructure of as prepared and sintered deposits was studied by electron microscopy. The bath composition was optimized to enable formation of dense deposits. 相似文献
128.
We present here the results of a study of the separation process in the extraction matrix of a novel high-intensity magnetic separator (HIMS). The matrix uses an ordered array of grooved plates (replacing conventional collectors, which are generally made of wires). Only experimental results are available for grooved plates in the literature, but here we propose a new theoretical approach. We report on the particles' behavior, the existence of a percolation phenomenon, and the filtration efficiency, in order to analyze and compare the performance of matrix structures (Lenoir's and Jones'). We discuss the causes of the percolation phenomenon and its effect on filtration efficiency. Correspondence between the theory and the experiments is good. We suggest appropriate uses of each matrix structure according to the property of the processed particles. 相似文献
129.
Thermal Transformations of an Aluminoborophosphate Binder 总被引:1,自引:0,他引:1
Thermal transformations of a commercial aluminoborophosphate binder are studied in a broad temperature range by optical microscopy, x-ray diffraction, IR spectroscopy, and thermal analysis. The introduction of B2O3 reduces the temperature of phosphate polycondensation, enhances the stability of cyclometaphosphates in a broad temperature range (180–1100°C), and reduces the stability of hydrogen phosphates. 相似文献
130.
The dielectric and pyroelectric properties of Ge-doped (0.1 mol %) TlInS2 crystals are studied. The results demonstrate that TlInS2 is a ferroelectric relaxor. The experimental data are used to evaluate, using the Vogel–Fulcher relation, the activation energy (0.045 eV), preexponential factor (f
0 = 2 × 1013 Hz), and the dipole-freezing temperature (T
F = 142 K) and to determine the temperature range of the stable relaxor (nanodomain) state and the temperature of the transition to the ferroelectric (macrodomain) state, accompanied by an anomaly in the temperature-dependent pyroelectric coefficient. 相似文献