全文获取类型
收费全文 | 12820篇 |
免费 | 393篇 |
国内免费 | 58篇 |
专业分类
电工技术 | 260篇 |
综合类 | 16篇 |
化学工业 | 2274篇 |
金属工艺 | 369篇 |
机械仪表 | 361篇 |
建筑科学 | 219篇 |
矿业工程 | 73篇 |
能源动力 | 704篇 |
轻工业 | 1171篇 |
水利工程 | 190篇 |
石油天然气 | 84篇 |
无线电 | 1623篇 |
一般工业技术 | 2778篇 |
冶金工业 | 1545篇 |
原子能技术 | 198篇 |
自动化技术 | 1406篇 |
出版年
2024年 | 39篇 |
2023年 | 177篇 |
2022年 | 505篇 |
2021年 | 504篇 |
2020年 | 409篇 |
2019年 | 409篇 |
2018年 | 553篇 |
2017年 | 512篇 |
2016年 | 483篇 |
2015年 | 280篇 |
2014年 | 447篇 |
2013年 | 887篇 |
2012年 | 519篇 |
2011年 | 678篇 |
2010年 | 541篇 |
2009年 | 531篇 |
2008年 | 477篇 |
2007年 | 389篇 |
2006年 | 332篇 |
2005年 | 263篇 |
2004年 | 244篇 |
2003年 | 219篇 |
2002年 | 180篇 |
2001年 | 143篇 |
2000年 | 147篇 |
1999年 | 156篇 |
1998年 | 355篇 |
1997年 | 233篇 |
1996年 | 252篇 |
1995年 | 219篇 |
1994年 | 182篇 |
1993年 | 171篇 |
1992年 | 143篇 |
1991年 | 151篇 |
1990年 | 114篇 |
1989年 | 108篇 |
1988年 | 130篇 |
1987年 | 109篇 |
1986年 | 89篇 |
1985年 | 115篇 |
1984年 | 94篇 |
1983年 | 107篇 |
1982年 | 99篇 |
1981年 | 88篇 |
1980年 | 78篇 |
1979年 | 54篇 |
1978年 | 46篇 |
1977年 | 56篇 |
1976年 | 76篇 |
1975年 | 32篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
A new seismic support device and its application in piping systems is described. The device, E-BAR (patented), can be cost effectively used for snubber replacement programs, mitigation of hydraulic transients, pipe whip and as a thermal stop. The device has pre-set gaps to allow free thermal movement. During a seismic or other dynamic load event, if the pipe movement exceeds the gap dimension, the device acts as an elastic or elastic-plastic restraint. The device also has a unique design feature for not exceeding the restraint force beyond a specified limit design value. To analyze piping systems with gap supports having elastic-plastic characteristics, modal analysis procedures for both response spectrum and time history methods are developed. The comparison of responses obtained from the procedures with nonlinear time history analysis and test results available in the literature shows excellent correlation. A pilot program conducted for snubber replacement with E-BARs demonstrates that the limit force feature of E-BAR makes them very attractive for snubber replacement. This is because a particular E-BAR with a specified limit design force can be selected, such that, the E-BAR replacing the snubber does not require any modifications be made to the existing support steel and hardware. 相似文献
12.
Xie K. Zhao J.H. Flemish J.R. Burke T. Buchwald W.R. Lorenzo G. Singh H. 《Electron Device Letters, IEEE》1996,17(3):142-144
A 6H-SiC thyristor has been fabricated and characterized. A forward breakover voltage close to 100 V and a pulse switched current density of 5200 A/cm2 have been demonstrated. The thyristor is shown to operate under pulse gate triggering for turn-on and turn-off, with a rise time of 43 ns and a fall time of less than 100 ns. The forward breakover voltage is found to decrease by only 4% when the operating temperature is increased from room temperature to 300°C. It is found that anode ohmic contact resistance dominates the device forward drop at high current densities 相似文献
13.
RJ Wilkinson K Hasl?v R Rappuoli F Giovannoni PR Narayanan CR Desai HM Vordermeier J Paulsen G Pasvol J Ivanyi M Singh 《Canadian Metallurgical Quarterly》1997,35(3):553-557
The diagnosis of infection caused by Mycobacterium tuberculosis is of increased public health concern following increases in the number of cases in developed countries and major increases in developing countries associated with the spread of human immunodeficiency virus (HIV) infection. The specificity of purified protein derivative skin testing for the detection of infection is compromised by exposure to environmental mycobacteria. Examination of sputum detects the most infectious patients, but not those with extrapulmonary disease. The 38-kDa antigen of M. tuberculosis contains two M. tuberculosis-specific B-cell epitopes. We overexpressed the gene for this antigen in Escherichia coli and evaluated the recombinant product in in vitro assays of T-cell function and as a target for the antibody response in humans. The sensitivity and specificity of the antigen as a skin test reagent were also assessed in outbred guinea pigs. We found that 69% of healthy sensitized humans recognize the antigen in vitro, as manifested by both cell proliferation and the production of gamma interferon. Untreated patients initially have a lower frequency of response (38%); this recovers to 72% during therapy. A total of 292 patients (20 with HIV coinfection) and 58 controls were examined for production of antibody to the 38-kDa antigen by using a commercially available kit. The sensitivity of the test in comparison with that of culture was 72.6%, and the specificity was 94.9%. The antigen was also tested for its ability to induce skin reactions in outbred guinea pigs sensitized by various mycobacterial species. The antigen provoked significant skin reactions in M. tuberculosis-, M. bovis BCG-, and M. intracellulare-sensitized animals. The significance of these findings and the usefulness of this antigen in immunodiagnosis are discussed. 相似文献
14.
15.
16.
A simple and easily programmable technique is proposed for the second-order analysis of frames. This technique involves the iterative process with modification of the stiffness matrix as well as the load vector in each iteration. Both curvature and sway effects are included. A numerical example is included to illustrate the results. 相似文献
17.
18.
19.
20.