全文获取类型
收费全文 | 131200篇 |
免费 | 10542篇 |
国内免费 | 5743篇 |
专业分类
电工技术 | 7714篇 |
技术理论 | 10篇 |
综合类 | 8667篇 |
化学工业 | 22012篇 |
金属工艺 | 7206篇 |
机械仪表 | 8605篇 |
建筑科学 | 9644篇 |
矿业工程 | 3677篇 |
能源动力 | 3868篇 |
轻工业 | 8940篇 |
水利工程 | 2175篇 |
石油天然气 | 7785篇 |
武器工业 | 938篇 |
无线电 | 15027篇 |
一般工业技术 | 16786篇 |
冶金工业 | 6256篇 |
原子能技术 | 1478篇 |
自动化技术 | 16697篇 |
出版年
2024年 | 527篇 |
2023年 | 2093篇 |
2022年 | 3684篇 |
2021年 | 5145篇 |
2020年 | 3822篇 |
2019年 | 3408篇 |
2018年 | 3814篇 |
2017年 | 4213篇 |
2016年 | 3808篇 |
2015年 | 5077篇 |
2014年 | 6278篇 |
2013年 | 7675篇 |
2012年 | 8090篇 |
2011年 | 9013篇 |
2010年 | 7937篇 |
2009年 | 7386篇 |
2008年 | 7319篇 |
2007年 | 6920篇 |
2006年 | 6963篇 |
2005年 | 6195篇 |
2004年 | 4321篇 |
2003年 | 4032篇 |
2002年 | 4099篇 |
2001年 | 3505篇 |
2000年 | 3292篇 |
1999年 | 3326篇 |
1998年 | 2793篇 |
1997年 | 2273篇 |
1996年 | 2178篇 |
1995年 | 1866篇 |
1994年 | 1537篇 |
1993年 | 1150篇 |
1992年 | 866篇 |
1991年 | 684篇 |
1990年 | 511篇 |
1989年 | 403篇 |
1988年 | 353篇 |
1987年 | 212篇 |
1986年 | 177篇 |
1985年 | 134篇 |
1984年 | 95篇 |
1983年 | 56篇 |
1982年 | 63篇 |
1981年 | 51篇 |
1980年 | 41篇 |
1979年 | 21篇 |
1977年 | 7篇 |
1976年 | 16篇 |
1975年 | 11篇 |
1970年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
32.
如果我们这个企业能生产长生不老的药品,那么,全世界的钱都会集中到我们的企业来。所以,我们现在需要什么?我们需要新项目,我们需要新产品,这些都要依靠科技进步。 相似文献
33.
广东省大型工程建设中天然放射性核素引起的环境问题 总被引:2,自引:0,他引:2
本文介绍了广东省境内几个大型基本建设工程项目中天然放射性核素引起的环境问题及有关治理对策,并就今后类似建设项目的辐射环境保护工作提出了建议。 相似文献
34.
Min-Seok Park Vladislav P. Vislovskiy Jong-San Chang Yong-Gun Shul Jin S. Yoo Sang-Eon Park 《Catalysis Today》2003,87(1-4):205-212
Alumina-supported vanadium oxide, VOx/Al2O3, and binary vanadium–antimony oxides, VSbOx/Al2O3, have been tested in the ethylbenzene dehydrogenation with carbon dioxide and characterized by SBET, X-ray diffraction, X-ray photoelectron spectroscopy, hydrogen temperature-programmed reduction and CO2 pulse methods. VSbOx/Al2O3 exhibited enhanced catalytic activity and especially on-stream stability compared to VOx/Al2O3 catalyst. Incorporation of antimony into VOx/Al2O3 increased dispersion of active VOx species, enhanced redox properties of the systems and formed a new mixed vanadium–antimony oxide phase in the most catalytically efficient V0.43Sb0.57Ox/Al2O3 system. 相似文献
35.
Summary Sedimentation experiments and X-ray photoelectron spectroscopy (XPS or ESCA) analyses have been used to study the effect of poly(methylmethacrylate) (PMMA) tacticity on aluminum oxide powder dispersion stability in a common solvent medium. The relative trends from sedimentation densities, and from surface analyses after solvent washing show that (PMMA) adsorption is greatest with isotactic polymer, where isotactic>atactic>syndiotactic adsorption. These results suggest that surface adsorption and hence dispersion stability can be influenced by polymer chain configuration as well as by chain conformation. 相似文献
36.
火电厂实施废水零排放的可行性探讨 总被引:1,自引:0,他引:1
对合肥发电厂的用排水现状进行了介绍,并提出了实施废水零排放的可行性方案。 相似文献
37.
The method of reverberation ray matrix is applied to analyze the dynamic behavior of structural members in trusses with pinned joints subjected to suddenly applied force. The results are compared with those in planar trusses with rigid joints. Detailed calculations are made with two types of trusses, a small laboratory model made of slender aluminum bars, and a hypothetical real size Pratt truss made of structural steel. It is found that the maximum dynamic bending strains in the members of both types of trusses are very large, comparable with the dynamic axial strains in the same member. The magnitudes of bending strains in the pinned truss differs little from those in the truss with rigid joints for both types of trusses. Such a large dynamic bending strain in a structure member, which is contradictory to the static behavior of the same truss, could be caused by the inertial force of the mass in structural members of the truss. 相似文献
38.
Z. M. Sun Z. G. Wang H. Hdl B. Weiss R. Sticker 《Materialwissenschaft und Werkstofftechnik》1995,26(9):483-487
The deformation behavior of pure recrystallized molybdenum under cyclic and static loads was investigated in the temperature range between 30°C and 10O°C, for stress amplitudes between 100 MPa and 250 MPa and for static loads up to 200 MPa. The results show that in spite of the low test temperatures and stress levels the Mo material exhibits considerable plastic strains which depend sensitively on frequenez and small changes in temperature.The activation energy deduced for the static and dynamic deformation is less than 0.98 eV which indicates thermally activated processes, to be explained by a dislocation kink model as described in the literature. The low-temperature fatigue behavior appears strongly influenced by creep-fatigue interaction phenomena. 相似文献
39.
A tennis novice watching a match for the first time might be surprised that the crowd erupts with cheers when a player wins one point, then barely applauds when he wins the next. The crowd is not necessarily fickle; some points are genuinely more important than others because a tennis match is hierarchically structured. One match consists of several sets. One set consists of several games. One game consists of several points. The match-winning point is the most important one. How can we make that importance visible? Our goal is to let a fan, a player, or a coach examine tennis data visually, extract the interesting parts, and jump from one item to another quickly and easily. The visualization tool should help parse the elements of a match. We developed an interactive system called TennisViewer to visualize the dynamic, tree-structured data representing a tennis match. It provides an interface for users to quickly explore tennis match information. The visualization tool reveals the overall structure of the match as well as the fine details in a single screen. It uses a 2D display of translucent layers, a design that contains elements of Tree-Maps and of the Visual Scheduler system, which was designed to help faculty and students identify mutually available (transparent) time slots when arranging group meetings. TennisViewer provides MagicLens filters to explore specialized views of the information and a time-varying display to animate all or part of a match 相似文献
40.
By using scanning polarization force microscopy,the deliquescence process and the atomic steps on the cleavage surface of CaCO3 in air were studied in situ.Under an exposure to medium umidity(-57%),the sloiw step movement has been observed. 相似文献