全文获取类型
收费全文 | 67552篇 |
免费 | 5788篇 |
国内免费 | 3093篇 |
专业分类
电工技术 | 3999篇 |
技术理论 | 4篇 |
综合类 | 4331篇 |
化学工业 | 11479篇 |
金属工艺 | 3657篇 |
机械仪表 | 4344篇 |
建筑科学 | 4677篇 |
矿业工程 | 1313篇 |
能源动力 | 2040篇 |
轻工业 | 4929篇 |
水利工程 | 1212篇 |
石油天然气 | 2653篇 |
武器工业 | 484篇 |
无线电 | 9173篇 |
一般工业技术 | 9302篇 |
冶金工业 | 2940篇 |
原子能技术 | 864篇 |
自动化技术 | 9032篇 |
出版年
2024年 | 246篇 |
2023年 | 955篇 |
2022年 | 1789篇 |
2021年 | 2538篇 |
2020年 | 1827篇 |
2019年 | 1656篇 |
2018年 | 1809篇 |
2017年 | 2021篇 |
2016年 | 2086篇 |
2015年 | 2670篇 |
2014年 | 3273篇 |
2013年 | 4140篇 |
2012年 | 4345篇 |
2011年 | 4892篇 |
2010年 | 4289篇 |
2009年 | 4032篇 |
2008年 | 3979篇 |
2007年 | 3649篇 |
2006年 | 3574篇 |
2005年 | 3125篇 |
2004年 | 2307篇 |
2003年 | 2240篇 |
2002年 | 2483篇 |
2001年 | 2049篇 |
2000年 | 1684篇 |
1999年 | 1465篇 |
1998年 | 1336篇 |
1997年 | 1036篇 |
1996年 | 956篇 |
1995年 | 832篇 |
1994年 | 685篇 |
1993年 | 549篇 |
1992年 | 395篇 |
1991年 | 328篇 |
1990年 | 246篇 |
1989年 | 207篇 |
1988年 | 167篇 |
1987年 | 116篇 |
1986年 | 83篇 |
1985年 | 65篇 |
1984年 | 57篇 |
1983年 | 36篇 |
1982年 | 47篇 |
1981年 | 34篇 |
1980年 | 33篇 |
1979年 | 14篇 |
1978年 | 7篇 |
1977年 | 9篇 |
1976年 | 22篇 |
1975年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
大庆油田公司确立的油气勘探“五五”工程的核心是立足油气勘探长远发展、统筹老区与新领域勘探,兼顾工程实施与地质研究、系统配套相关技术理论,内容是调整工程和投资结构、完善油气勘探地质理论、发展各项适用技术,目的是促进油气勘探寻求大发现、获得大突破。通过实施“五五”工程,勘探工作运行平稳,勘探成果殷实丰硕,勘探领域层次分明,对油气勘探工作的发展产生了巨大的推动力,确保了大庆探区油气勘探实施的效果。通过对油气勘探“五五”工程实践过程的深入剖析,认为在油气勘探中“思路决定出路、前置加载量是基础、新技术应用是关键”。 相似文献
83.
质量成本是指企业为保证产品质量而支出的一切费用,以及产品质量未达到规定的标准而造成的一切损失的总和。开展质量成本研究工作是企业深化质量管理和成本管理的一条有效途径。 相似文献
84.
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
85.
孙进 《石油化工管理干部学院学报》2003,(3):40-42
引入劳动力市场价位是企业薪酬制度改革的必然趋势。系统研究和分析了劳动力市场价位的基本特征;提出企业在引入劳动力市场价位过程中应该遵循的基本原则。 相似文献
86.
Li-Ching Hong Sheng-Jye Hwang 《Components and Packaging Technologies, IEEE Transactions on》2004,27(2):291-295
There were many studies about the prediction of warpage due to thermal mismatch , . However, cure induced warpage is usually ignored and the results can be inaccurate. To minimize this problem, a thorough understanding of epoxy molding compound (EMC) with pressure-volume-temperature-cure (P-V-T-C) relation is necessary. This paper used the P-V-T-C relation of an encapsulation material to formulate the stress-strain relationship. With the help of finite element method (FEM) and mold flow analysis, warpage predictions combined with P-V-T-C relation were performed and the results show that this approach is practical. For a given P-V-T-C relation, the shrinkage direction is pointing toward the gate and maximum warpage usually occurs at the boundary of an integrated circuit (IC) package. Variation of specific volume difference along the flow direction is larger than that perpendicular to the flow direction. When temperature difference is small in thickness direction, specific volume difference in thickness direction varies only slightly. 相似文献
87.
Plastic deformation in a multifunctional Ti-Nb-Ta-Zr-O alloy 总被引:7,自引:0,他引:7
S. Kuramoto T. Furuta J. H. Hwang K. Nishino T. Saito 《Metallurgical and Materials Transactions A》2006,37(3):657-662
Mechanisms for plastic deformation in the newly developed Ti-24 at. pct (Ta + Nb + V)-(Zr,Hf)-O alloys (Gum Metal) were investigated
in relation to their unique properties. Transmission electron microscopy revealed that the microstructure after deformation
was characterized by highly distorted crystal images, which are accompanied by numerous “giant faults.” Such plastic behavior
implies that a large amount of elastic stain energy was stored discretely and hierarchically during cold working. Calculated
elastic constants of the Ti-X (Nb,Ta,Mo,V) binary systems predicted that Young’s modulus in 〈001〉 and shear moduli along some
directions including slip systems in a bcc crystal were extraordinary small. The low modulus not only well explains the highly
distorted microstructure observed in the cold-worked specimens, but also signifies that ideal shear strength of the developed
alloys is a very small value, which is close to the practical strength required for plastic deformation in the alloy. This
implies that the giant faults observed in the deformed specimen were formed without the aid of dislocation glide. 相似文献
88.
Due to interference, path loss, multipath fading, background noise, and many other factors, wireless communication normally
cannot provide a wireless link with both a high data rate and a long transmission range. To address this problem, striping
network traffic in parallel over multiple lower-data-rate but longer-transmission-range wireless channels may be used. In
this paper, we propose a new striping method and evaluate its performances over multiple IEEE 802.11(b) channels under various
conditions. Our extensive simulation results show that this method is quite effective for such an application.
S.Y. Wang is an Associate Professor of the Department of Computer Science and Information Engineering at National Chiao Tung University,
Taiwan. He received his Master and Ph.D. degree in computer science from Harvard University in 1997 and 1999, respectively.
His research interests include wireless networks, Internet technologies, network simulations, and operating systems. He is
the author of the NCTUns 2.0 network simulator and emulator, which is being widely used by network and communication researchers.
More information about the tool is available at http://NSL.csie.nctu.edu.tw/nctuns.html.
C.H. Hwang received his master degree in computer science from NCTU in 2002 and currently is working for a network company.
C.L. Chou currently is a third-year Ph.D. student at the Department of Computer Science and Information Engineering, National Chiao
TungUniversity (NCTU), Taiwan. He received his master degree in computer science from NCTU in 2002. 相似文献
89.
90.
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