全文获取类型
收费全文 | 80899篇 |
免费 | 3579篇 |
国内免费 | 230篇 |
专业分类
电工技术 | 1192篇 |
综合类 | 131篇 |
化学工业 | 16399篇 |
金属工艺 | 2441篇 |
机械仪表 | 3537篇 |
建筑科学 | 2531篇 |
矿业工程 | 152篇 |
能源动力 | 2767篇 |
轻工业 | 5927篇 |
水利工程 | 485篇 |
石油天然气 | 280篇 |
武器工业 | 1篇 |
无线电 | 11771篇 |
一般工业技术 | 15638篇 |
冶金工业 | 10294篇 |
原子能技术 | 821篇 |
自动化技术 | 10341篇 |
出版年
2023年 | 743篇 |
2022年 | 1185篇 |
2021年 | 1957篇 |
2020年 | 1320篇 |
2019年 | 1436篇 |
2018年 | 1859篇 |
2017年 | 1773篇 |
2016年 | 2265篇 |
2015年 | 1848篇 |
2014年 | 2768篇 |
2013年 | 4878篇 |
2012年 | 4326篇 |
2011年 | 5381篇 |
2010年 | 4024篇 |
2009年 | 4158篇 |
2008年 | 4046篇 |
2007年 | 3533篇 |
2006年 | 3167篇 |
2005年 | 2687篇 |
2004年 | 2578篇 |
2003年 | 2347篇 |
2002年 | 2200篇 |
2001年 | 1708篇 |
2000年 | 1559篇 |
1999年 | 1582篇 |
1998年 | 2937篇 |
1997年 | 1985篇 |
1996年 | 1641篇 |
1995年 | 1368篇 |
1994年 | 1095篇 |
1993年 | 1043篇 |
1992年 | 758篇 |
1991年 | 687篇 |
1990年 | 681篇 |
1989年 | 662篇 |
1988年 | 534篇 |
1987年 | 497篇 |
1986年 | 480篇 |
1985年 | 496篇 |
1984年 | 419篇 |
1983年 | 374篇 |
1982年 | 357篇 |
1981年 | 324篇 |
1980年 | 295篇 |
1979年 | 293篇 |
1978年 | 257篇 |
1977年 | 307篇 |
1976年 | 389篇 |
1975年 | 239篇 |
1974年 | 196篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
In advancement of Pyrosil®‐technology a new kind of precursor delivery was developed, build and tested on real substrates. A Lab‐demonstrator was build to demonstrate the resources of the technology. 相似文献
42.
The aim of this study was to evaluate the use of total coliforms (TC) and faecal coliforms (FC) using a membrane filtration method for precise monitoring of faecal pollution in Korean surface water. The samples were collected in Korea from both main rivers and their tributaries. Presumptive TC * FC were enumerated. The ratios of presumptive FC to TC were not constant, but varied widely, and TC were difficult to enumerate because of overgrowth by background colonies. For FC this was not the case. Seven hundred and three purified strains of presumptive TC * FC and their background colonies were biotyped using API 20E. Among 272 presumptive TC, non-faecal related species, Aeromonas hydrophila dominated (34.6%) and E. coli accounted for only 5.1%. In contrast, E. coli made up 89% of the 209 presumptive FC. Furthermore, of 164 background colonies on Endo Agar LES, 54.9% was A. hydrophila, while background colonies on m-FC Agar were few (58 strains), and despite their atypical colony appearance, most of them were biotyped as enteric bacteria. These results reveal that the detection of FC rather than TC using m-FC Agar is more appropriate for faecal pollution monitoring in eutrophicated surface water located in a temperate region. 相似文献
43.
Using an integrated process of data and modeling in HRA 总被引:1,自引:0,他引:1
John Wreathall Dennis Bley Emilie Roth Jordan Multer Thomas Raslear 《Reliability Engineering & System Safety》2004,83(2):221
The paper describes an approach taken to estimate the probabilities of failure associated with various railroad tasks to prevent accidents (principally collisions and derailments). These probabilities were estimated using an expert elicitation process that used partially relevant data available from a variety of databases and that were filtered and scaled to make them more directly relevant to the analyses being performed. Extensive qualitative studies were performed prior to the elicitation process to identify relevant contexts under which the tasks can be performed. 相似文献
44.
Soo Jin Kim Wha Young Lee Yeungho Park Wansoo Huh Young Gwan Ko 《Polymer Engineering and Science》2003,43(5):1011-1017
Supported zirconcene catalysts on a new support, MgO, were prepared and tested in ethylene polymerization. Three types of impregnation methods were employed to find an optimum supporting method for MgO. The direct impregnation of Cp2ZrCl2 on MgO showed low metal loading and polymerization activity, while the catalyst had a higher metal loading and polymerization activity when MgO was treated with methylaluminoxane (MAO) before supporting. Treatment of MgO with MAO during the supporting step invoked two types of catalytic sites, which was evidenced by the bimodal molecular weight distribution of the polymer products. MgO is considered to have potential as a support for metallocenes. 相似文献
45.
From its foundation until 2004, ETRI has registered over 1,000 US patents. This letter analyzes the characteristics of these patents and addresses the explanatory factors affecting their citation counts. For explanatory variables, research team related variables, invention specific variables, and geographical domain related variables are suggested. Zero‐altered count data models are used to test the impact of independent variables. A key finding is that technological cumulativeness, the scale of invention, outputs in the electronic field, and the degree of dependence on the US technology domain positively affect the citation counts of ETRI‐invented US patents. The magnitude of international presence appears to negatively affect the citation counts of ETRI‐invented US patents. 相似文献
46.
Evaluation and optimization of package processing and design through solder joint profile prediction 总被引:1,自引:0,他引:1
Solder joints are generated using a variety of methods to provide both mechanical and electrical connection for applications such as flip-chip, wafer level packaging, fine pitch, ball-grid array, and chip scale packages. Solder joint shape prediction has been incorporated as a key tool to aid in process development, wafer level and package level design and development, assembly, and reliability enhancement. This work demonstrates the application of an analytical model and the Surface Evolver software in analyzing a variety of solder processing methods and package types. Bump and joint shape prediction was conducted for the design of wafer level bumping, flip-chip assembly, and wafer level packaging. The results from the prediction methodologies are validated with experimentally measured geometries at each level of design. 相似文献
47.
Jeong-Soo Lee Yang-Kyu Choi Daewon Ha Balasubramanian S. Tsu-Jae King Bokor J. 《Electron Device Letters, IEEE》2003,24(3):186-188
The hydrogen annealing process has been used to improve surface roughness of the Si-fin in CMOS FinFETs for the first time. Hydrogen annealing was performed after Si-fin etch and before gate oxidation. As a result, increased saturation current with a lowered threshold voltage and a decreased low-frequency noise level over the entire range of drain current have been attained. The low-frequency noise characteristics indicate that the oxide trap density is reduced by a factor of 3 due to annealing. These results suggest that hydrogen annealing is very effective for improving device performance and for attaining a high-quality surface of the etched Si-fin. 相似文献
48.
K. N. Subramanian J. G. Lee 《Journal of Materials Science: Materials in Electronics》2004,15(4):235-240
Properties of body centered tetragonal tin are highly anisotropic. As a consequence large stresses can develop at the tin grain boundaries due to coefficient of thermal expansion mismatch during temperature excursions. A modeling approach to evaluate the 3D stress states that develop at grain boundaries during thermomechanical fatigue in tin-based solder is presented. Development of significant amounts of stresses in the plane of the grain boundary can cause grain-boundary sliding and surface-relief effects, while those normal to the grain boundary can cause grain-boundary decohesion and cracking. 相似文献
49.
T. Choi J.‐H. Jang C.K. Ullal M.C. LeMieux V.V. Tsukruk E.L. Thomas 《Advanced functional materials》2006,16(10)
The probing of the micromechanical properties within a two‐dimensional polymer structure with sixfold symmetry fabricated via interference lithography reveals a nonuniform spatial distribution in the elastic modulus “imprinted” with an interference pattern in work reported by Tsukruk, Thomas, and co‐workers on p. 1324. The image prepared by M. Lemieux and T. Gorishnyy shows how the interference pattern is formed by three laser beams and is transferred to the solid polymer structure. The elastic and plastic properties within a two‐dimensional polymer (SU8) structure with sixfold symmetry fabricated via interference lithography are presented. There is a nonuniform spatial distribution in the elastic modulus, with a higher elastic modulus obtained for nodes (brightest regions in the laser interference pattern) and a lower elastic modulus for beams (darkest regions in the laser interference pattern) of the photopatterned films. We suggest that such a nonuniformity and unusual plastic behavior are related to the variable material properties “imprinted” by the interference pattern. 相似文献
50.
Thomas S. Lowry John C. Bright Murray E. Close Christina A. Robb Paul A. White Stewart G. Cameron 《国际水资源开发杂志》2003,19(4):579-592
The primary objective of this project is to identify gaps, whether real or perceived, that hinder effective groundwater management in New Zealand. These gaps show as gaps in information, gaps in implementation, gaps in technological and management tools, and gaps in understanding of fundamental processes. The secondary objective is to propose a management strategy to close the identified gaps. Several methods are used to meet these objectives: surveys distributed to selected staff in each regional council; the review of various written reports; the analysis of land-use databases; and private consultation within each regional council. Results show that groundwater management in New Zealand is generally reactionary with the main gaps being in strategic planning and national guidelines. Most gaps appear to be predominantly information and implementation issues. In some cases there are gaps in the understanding of fundamental processes within an aquifer system, including the long-term effects of land-use on groundwater quality. An adaptive management approach is suggested as a means of closing these gaps. 相似文献