全文获取类型
收费全文 | 56736篇 |
免费 | 7440篇 |
国内免费 | 4255篇 |
专业分类
电工技术 | 5161篇 |
技术理论 | 3篇 |
综合类 | 5113篇 |
化学工业 | 7542篇 |
金属工艺 | 3481篇 |
机械仪表 | 4223篇 |
建筑科学 | 4298篇 |
矿业工程 | 2249篇 |
能源动力 | 1590篇 |
轻工业 | 5500篇 |
水利工程 | 1834篇 |
石油天然气 | 2160篇 |
武器工业 | 794篇 |
无线电 | 7014篇 |
一般工业技术 | 5651篇 |
冶金工业 | 2402篇 |
原子能技术 | 841篇 |
自动化技术 | 8575篇 |
出版年
2024年 | 374篇 |
2023年 | 1191篇 |
2022年 | 2641篇 |
2021年 | 3469篇 |
2020年 | 2558篇 |
2019年 | 1863篇 |
2018年 | 2046篇 |
2017年 | 2439篇 |
2016年 | 2094篇 |
2015年 | 3070篇 |
2014年 | 3830篇 |
2013年 | 4251篇 |
2012年 | 4957篇 |
2011年 | 4982篇 |
2010年 | 4353篇 |
2009年 | 4012篇 |
2008年 | 3894篇 |
2007年 | 3600篇 |
2006年 | 2980篇 |
2005年 | 2311篇 |
2004年 | 1614篇 |
2003年 | 1165篇 |
2002年 | 1183篇 |
2001年 | 1005篇 |
2000年 | 714篇 |
1999年 | 355篇 |
1998年 | 232篇 |
1997年 | 212篇 |
1996年 | 179篇 |
1995年 | 143篇 |
1994年 | 125篇 |
1993年 | 100篇 |
1992年 | 84篇 |
1991年 | 56篇 |
1990年 | 44篇 |
1989年 | 55篇 |
1988年 | 35篇 |
1987年 | 22篇 |
1986年 | 24篇 |
1985年 | 19篇 |
1984年 | 12篇 |
1983年 | 15篇 |
1982年 | 13篇 |
1981年 | 19篇 |
1980年 | 25篇 |
1979年 | 14篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1959年 | 6篇 |
1951年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
根据我国专利法的原则,在对我国催化重整和芳烃生产专利检索过程和结果进行分析的基础上,阐述了对目前我国催化重整工艺专利市场的几点看法并提出对策。 相似文献
62.
The Fas receptor is a member of a family of cell death receptors, including tumor necrosis factor receptor I (TNFR I), death receptor 3 and 4 (DR3 and DR4), and cytopathic avian receptor 1 (CAR1). The Fas receptor is composed of several discrete domains, including three cysteine-rich domains (CRDs), a transmembrane domain, and an intracellular domain responsible for transmitting an apoptotic signal. While the mechanism of Fas-mediated cell death has become elucidated, the requirements for Fas ligand binding to the receptor have not been fully defined. Using a series of chimeric Fc-receptor fusion proteins between the human Fas receptor and TNFR I, each cysteine-rich domain of Fas was found to be required for interaction with the Fas ligand. Interestingly, TNFR I CRD1 could partially substitute for the Fas CRD1. The importance of this domain was underscored by the analysis of a Fas extracellular mutation (C66R), which resulted in a complete loss of ligand binding. This mutation was cloned from a human patient suffering from Canale-Smith syndrome, which is characterized by autoimmunity resembling that observed in the lpr and lprcg mice. The localization of essential ligand binding domains in the Fas receptor correlated exactly with the ability of the Fas receptor fusion proteins to prevent cell death mediated by the Fas ligand. 相似文献
63.
Chao C.-J. Wong S.-C. Chen M.-J. Liew B.-K. 《Semiconductor Manufacturing, IEEE Transactions on》1998,11(4):615-623
Interconnect parasitic parameters in integrated circuits have significant impact on circuit speed. An accurate monitoring of these parameters can help to improve interconnect performance during process development, provide information for circuit design, or give useful reference for circuit failure analysis. Existing extraction methods either are destructive (such as SEM measurement) or can determine only partial parasitic parameters (such as large capacitor measurement). In this paper, we present a new method for extracting interconnect parasitic parameters, which can simultaneously determine the interlayer and intralayer capacitances, line resistance, and effective line width. The method is based on two test patterns of the same structure with different dimensions. The structure consumes less wafer area than existing methods. The method shows good agreement with SEM measurement of dielectric thickness in both nonglobal planarized and chemical-mechanical polished processes, and gives accurate prediction of the process spread of a ring oscillator speed over a wafer 相似文献
64.
65.
采用气囊作内模进行浇筑桥面板混凝土 ,加快了预制桥面板施工进度 ,确保工程施工质量 ,并降低了工程施工成本 相似文献
66.
67.
目前国内大多数铝加工厂对铝带材冷轧机机前展平辊的作用缺乏足够的认识,甚至弃而不用。本文主要论述展平辊的作用及展平辊重叠量的计算方法。 相似文献
68.
69.
通过对中温固化环氧树脂DSC、扭辫分析、凝胶时间、粘度、力学性能的测定,固化反应活化能的计算,研究了在贮存树脂的过程中环境湿度对树脂的固化反应和性能的影响。 相似文献
70.
Chao M. Huang Dong Zhu Xu Yuren Waltraud M. Kriven Chao Y. Yuh 《Materials Science and Engineering: A》1996,220(1-2)
A composite of O′SiAlON (Si2-xAlxN2-xO1+x, with x 0.14) reinforced with 20 vol.% SiC monofilaments was fabricated by hot-pressing, at 1600°C, for 2 h under 34 MPa pressure. The mechanical and interfacial properties of the composites, as-fabricated as well as post-oxidized, were, investigated. The composite exhibited a significant improvement in ultimate flexure strength (640 MPa) and work of fracture (42 kJ m−2) compared with that (350 MPa and 1.8 kJ m−2, respectively) of the monolithic material. These mechanical properties were slightly increased after the composite was heat treated for 24 h in air at 1200 and 1300°C. However, the composite exhibited a significant degradation in ultimate strength, while the work of fracture (WOF) remained unchanged after exposure in air at temperatures beyond 1400°C. The as-fabricated composite revealed a low interfacial shear strength (6.2 MPa) and a frictional sliding stress (3.2 MPa). After the composite was oxidized at elevated temperatures, the interfacial bonding and sliding stresses were reduced to noticeable extents, resulting from the degradation of the carbon coating layer of the SiC monofilaments. 相似文献