全文获取类型
收费全文 | 1277篇 |
免费 | 57篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 17篇 |
综合类 | 5篇 |
化学工业 | 275篇 |
金属工艺 | 19篇 |
机械仪表 | 35篇 |
建筑科学 | 42篇 |
矿业工程 | 4篇 |
能源动力 | 69篇 |
轻工业 | 56篇 |
水利工程 | 13篇 |
石油天然气 | 2篇 |
无线电 | 214篇 |
一般工业技术 | 202篇 |
冶金工业 | 148篇 |
自动化技术 | 240篇 |
出版年
2024年 | 3篇 |
2023年 | 6篇 |
2022年 | 14篇 |
2021年 | 28篇 |
2020年 | 23篇 |
2019年 | 29篇 |
2018年 | 23篇 |
2017年 | 36篇 |
2016年 | 38篇 |
2015年 | 46篇 |
2014年 | 48篇 |
2013年 | 102篇 |
2012年 | 64篇 |
2011年 | 82篇 |
2010年 | 59篇 |
2009年 | 62篇 |
2008年 | 54篇 |
2007年 | 61篇 |
2006年 | 35篇 |
2005年 | 46篇 |
2004年 | 36篇 |
2003年 | 38篇 |
2002年 | 33篇 |
2001年 | 28篇 |
2000年 | 21篇 |
1999年 | 21篇 |
1998年 | 46篇 |
1997年 | 34篇 |
1996年 | 19篇 |
1995年 | 22篇 |
1994年 | 14篇 |
1993年 | 14篇 |
1992年 | 10篇 |
1991年 | 10篇 |
1990年 | 11篇 |
1989年 | 11篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 16篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1972年 | 5篇 |
排序方式: 共有1341条查询结果,搜索用时 15 毫秒
71.
J. Flicstein S. Pata J. M. Le Solliec L. S. How Kee Chun J. F. Palmier J. L. Courant 《Computational Materials Science》1998,10(1-4):116-126
Microstructural changes of surfaces and bulk of a SiN: H were investigated at the atomic level by a simulator. The simulator is based on a solid-on-solid type model for ultraviolet localized-chemical vapor deposition. The calculations consider the well-defined photolysis products adsorbed at atomic sites. Incorporation of main species is enabled by a Monte Carlo-Metropolis simulation technique. Photodeposition rates are obtained using bond dissociation energies. In this manner, the dependence of root-mean-square deviation of surface roughness and bulk porosity on operating conditions can be predicted. Photonucleation and photodeposition with a UV low pressure mercury lamp at low pressure and temperature were simulated onto indium phosphide substrate. 相似文献
72.
A human study of the effects of topical nystatin (Mycostatin) therapy of oral candidiasis showed that effects of treatment were limited to the time in which the drug was used. Two weeks of therapy resulted in significant reduction in number of organisms and marked improvement in signs and symptoms of candidiasis. The condition recurred rapidly following cessation of treatment. No change in specific anticandida antibody in saliva or in adherence of Candida albicans to mucosal epithelium (in vitro) was seen with treatment. 相似文献
73.
74.
A two-grid polarization rapid scan interferometer for the measurement of Electron Cyclotron Emission from the LT-4 Tokamak is described. The instrument incorporates two scanning mirrors, and a back e.m.f. derived mirror position monitor 相似文献
75.
Elliott MR Arbogast KB Menon R Durbin DR Winston FK 《Accident; analysis and prevention》2003,35(6):833-840
Estimated traveling speed and speed limit have typically been used in population-based surveillance data to estimate crash severity. The accuracy of these measures in predicting crash severity is unknown. The Partners for Child Passenger Safety (PCPS) surveillance system offers a unique opportunity to compare these measures, as well as a novel measure of crash severity, “self-report” delta-V, to the accepted measure of delta-V estimated during detailed crash-investigations in 118 crashes. This “self-report” delta-V was computed from the estimated traveling speeds and direction of impact obtained from telephone interviews with drivers. These “self-reported” delta-V estimates are modestly associated with crash-investigation delta-V estimates, with the degree of association a function of the direction of impact: when the respondent was struck from the rear, the degree of association is strong; frontal, side, and single-vehicle crashes yield weaker associations. This “self-reported” delta-V measure, however, is a substantial improvement over use of estimated traveling speed or speed limit only. 相似文献
76.
Tensile Strength Characteristics of Unsaturated Sands 总被引:5,自引:0,他引:5
Tensile strength characteristics of unsaturated sands are examined through a combined theoretical and experimental study. The characteristics of tensile strength in all three water retention regimes of pendular, funicular, and capillary are examined. A simple direct tensile strength apparatus is employed to determine tensile strength for sands with a broad range of particle sizes from silty sand to fine sand and medium sand over a full range of degree of saturation. Tensile strength characteristic curves (TSCC) are established experimentally for these sands and are used to validate the existing theories for tensile strength in the pendular regime. The TSCC for sand characteristically exhibits two zeros at 0 and near 100% saturation, and two peak values occurring in the pendular and capillary regimes, respectively. A minimum tensile strength is observed in the dense fine sand, indicating that either water bridges or pore pressure contributes exclusively to the tensile strength in the funicular regime of this sand. The maximum tensile strength for the silty sand is 1,448?Pa, the fine sand is 1,416?Pa, and the medium sand is 890?Pa. Comparison between the soil–water characteristic curves obtained for these sands indicates that the peak tensile strength in the capillary regime is highly correlated to the air-entry pressure. Photographs of the failure surfaces clearly delineate distinct geometric characteristics for different water retention regimes. Analysis of the patterns of failure surfaces in different water retention regimes indicates that the effective stress principle is valid for tensile stress failure in unsaturated sands. 相似文献
77.
In this paper, based on the Darwinian and Lamarckian evolution theories, three hybrid genetic programming (GP) algorithms integrated with different local search operators (LSOs) are implemented to improve the search efficiency of the standard GP. These three LSOs are the genetic algorithm, the linear bisection search, and the Hooke and Jeeves method. A simple encoding method is presented to encode the GP individuals into the expressions that can be recognized by the different LSOs. The implemented hybrid GP algorithms are applied to identify the excitation force acting on the structures from the measured structural response, which is an important type of inverse problem in structural dynamics. Illustrative examples of a frame structure and a multistory building structure demonstrate that, compared with the standard GP, the hybrid GP algorithms have higher search efficiency which can be used as alternate global search and optimization tools for other engineering problem solving. 相似文献
78.
79.
80.
This paper presents a robust actuator fault reconstruction scheme for linear uncertain systems using sliding mode observers. In existing work, fault reconstruction via sliding mode observers is limited to either linear certain systems subject to unknown inputs, relative degree one systems or a specific class of relative degree two systems. This paper presents a new method that is applicable to a wider class of systems with relative degree higher than one, and can also be used for systems with more unknown inputs than outputs. The method uses two sliding mode observers in cascade. Signals from the first observer are processed and used to drive the second observer. Overall, this results in actuator fault reconstruction being feasible for a wider class of systems than using existing methods. A simulation example verifies the claims made in this paper. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献