全文获取类型
收费全文 | 4046篇 |
免费 | 136篇 |
国内免费 | 2篇 |
学科分类
工业技术 | 4184篇 |
出版年
2022年 | 19篇 |
2021年 | 63篇 |
2020年 | 60篇 |
2019年 | 54篇 |
2018年 | 68篇 |
2017年 | 52篇 |
2016年 | 78篇 |
2015年 | 64篇 |
2014年 | 97篇 |
2013年 | 115篇 |
2012年 | 133篇 |
2011年 | 169篇 |
2010年 | 130篇 |
2009年 | 130篇 |
2008年 | 134篇 |
2007年 | 131篇 |
2006年 | 115篇 |
2005年 | 137篇 |
2004年 | 87篇 |
2003年 | 92篇 |
2002年 | 87篇 |
2001年 | 92篇 |
2000年 | 89篇 |
1999年 | 86篇 |
1998年 | 308篇 |
1997年 | 181篇 |
1996年 | 134篇 |
1995年 | 119篇 |
1994年 | 89篇 |
1993年 | 95篇 |
1992年 | 61篇 |
1991年 | 56篇 |
1990年 | 56篇 |
1989年 | 49篇 |
1988年 | 42篇 |
1987年 | 35篇 |
1986年 | 36篇 |
1985年 | 46篇 |
1984年 | 29篇 |
1983年 | 31篇 |
1982年 | 39篇 |
1981年 | 38篇 |
1980年 | 29篇 |
1979年 | 51篇 |
1978年 | 21篇 |
1977年 | 47篇 |
1976年 | 92篇 |
1975年 | 22篇 |
1974年 | 16篇 |
1972年 | 18篇 |
排序方式: 共有4184条查询结果,搜索用时 26 毫秒
11.
Ravi Joshi Jörg Engstler P. Kesavan Nair Prathap Haridoss Jörg J. Schneider 《Diamond and Related Materials》2008,17(6):913-919
Carbon nanotubes (CNTs) have been synthesized using the arc discharge method with a rotating graphite disc as the cathode. Arcing was carried out in open air and without the use of catalysts. The current density was maintained constant through out the experiment, while, the rate of rotation of the cathode and atmosphere under which arcing was carried out were changed during experimentation. Characterization of the samples produced indicates that rotation of the cathode has a significant impact on the quality and yield of the process. It is proposed that rotation of the cathode drags plasma formed between two electrodes away from high temperature region. This results in a sudden quenching of the reactive plasma. The time available for nucleation and growth phenomena is significantly reduced and thus leads to the formation of highly graphitic multi walled CNTs (yield 60%) and traces of double walled CNTs. 相似文献
12.
With new methods for enforcing security policies comes the opportunity to formulate application-specific policies. But leveraging that flexibility might prove a difficult problem, not only in practice, but also in theory. 相似文献
13.
Delevoye-Turrell Yvonne; Giersch Anne; Wing Alan M.; Danion Jean-Marie 《Canadian Metallurgical Quarterly》2007,116(1):56
Many everyday activities depend on the capacity to organize and smoothly execute motor sequences. The authors tested the hypothesis that a sequencing deficit is associated with schizophrenia. They used a new method to distinguish between lower and higher order mechanisms for the impairment. The 1st task involved triggered sequences in which sensory information from 1 movement was the cue for initiation of the following movement. Results showed that the motor sequences were performed as fluently in patients as in controls. The 2nd and 3rd tasks involved sequences in which the entire movement sequence could be preplanned. Patients executed the sequences less fluently than controls but only under the condition where action sequences were required. Furthermore, the patients' fluency deficit increased with sequence complexity. The high discrimination power of Task 3 gave the authors a means to control for a potential psychometric confound involving differential discriminating power and to argue in favor of a specific higher order motor fluency deficit in patients with schizophrenia. It is suggested that basic lower order mechanisms that integrate sensory information with outgoing motor commands are preserved in schizophrenia, whereas higher order integrative mechanisms that are required for the smooth coordination of motor sequences are impaired. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
14.
15.
IEEE Security & Privacy's associate editor in chief discusses technology's role in identity fraud and identity theft. 相似文献
16.
17.
Heart transplant patients take several medications that could affect their periodontal health. Gingival overgrowth associated with cyclosporin (immunosuppressant agent) and nifedipine (calcium channel blocker) is well documented. Candidal infections often develop because of immune suppression. This report describes the clinical and histopathological changes in the gingival tissues of a heart transplant patient and their management. The gingival tissues exhibited pronounced enlargement. The gingivae were lobulated, and the surface of the lobulations was pebbly and granular. Biopsies showed lobules of fibrous connective tissue covered by stratified squamous epithelium. The outer surfaces were dotted with numerous smaller papillations. Candidal hyphae were present in the superficial layers of the epithelium. The extensive papillary lesions appear to be related to candidiasis and constitute a condition which is best designated as papillary stomatitis. Hyperplastic gingival tissues were excised, and the patient was placed on periodic maintenance. One-year postoperative follow-up showed minor gingival growth. 相似文献
18.
Characterization of the epidermal growth factor receptor in pig oviduct and endometrium 总被引:1,自引:0,他引:1
K Wollenhaupt U Tiemann R Einspanier F Schneider W Kanitz KP Brüssow 《Canadian Metallurgical Quarterly》1997,111(2):173-181
Two different plaque variants of Japanese encephalitis virus were selected from a wild-type Taiwanese isolate using Vero cells. One variant was found to exhibit small plaque morphology with retarded virus replication kinetics in Vero cells, and was demonstrated to be resistant to monoclonal antibody (mAb) E3.3 neutralization. The other variant showed large plaque morphology, was sensitive to mAb E3.3 neutralization, and manifested reduced virulence in mice on both intracranial and intraperitoneal inoculations. These two variants propagated in Vero cells retained high levels of infectivity but had relatively low HA titers as compared with the parent strain. The envelope sequences of these two variants showed four amino acid differences at residues E-85 (Glu/Arg), E-306 (Glu/Gly), E-331 (Ser/Arg), and E-387 (Met/Arg). Our results indicated the neutralizing epitope of Japanese encephalitis virus did not overlap with virus virulence determinant. 相似文献
19.
Summary The laminar flow near an infinite plane wall perpendicular to a line sink of constant strength is investigated in the limit of large Reynolds numbers. Self-similarity requires that fluid is issuing from the boundary layer. The inviscid flow outside the boundary layer is governed by the Euler equations. A one-parametric set of solutions to the Euler equations with appropriate boundary conditions is given. Uniqueness of the inviscid flow solution is obtained from matching with the boundary layer expansion. The solution of the boundary-layer equations is given both in closed form and numerically. It is found that at the edge of the boundary layer the vorticity decays algebraically.Dedicated to Prof. Dr. Dr. h. c. Franz Ziegler on the occasion of his 60th birthday 相似文献
20.