全文获取类型
收费全文 | 18217篇 |
免费 | 1371篇 |
国内免费 | 404篇 |
专业分类
电工技术 | 701篇 |
综合类 | 486篇 |
化学工业 | 3181篇 |
金属工艺 | 591篇 |
机械仪表 | 667篇 |
建筑科学 | 900篇 |
矿业工程 | 166篇 |
能源动力 | 472篇 |
轻工业 | 1783篇 |
水利工程 | 246篇 |
石油天然气 | 268篇 |
武器工业 | 75篇 |
无线电 | 2087篇 |
一般工业技术 | 2646篇 |
冶金工业 | 3048篇 |
原子能技术 | 188篇 |
自动化技术 | 2487篇 |
出版年
2024年 | 72篇 |
2023年 | 251篇 |
2022年 | 483篇 |
2021年 | 746篇 |
2020年 | 555篇 |
2019年 | 480篇 |
2018年 | 619篇 |
2017年 | 591篇 |
2016年 | 608篇 |
2015年 | 639篇 |
2014年 | 779篇 |
2013年 | 1122篇 |
2012年 | 1080篇 |
2011年 | 1183篇 |
2010年 | 887篇 |
2009年 | 801篇 |
2008年 | 864篇 |
2007年 | 730篇 |
2006年 | 616篇 |
2005年 | 491篇 |
2004年 | 419篇 |
2003年 | 370篇 |
2002年 | 380篇 |
2001年 | 305篇 |
2000年 | 285篇 |
1999年 | 288篇 |
1998年 | 1033篇 |
1997年 | 620篇 |
1996年 | 436篇 |
1995年 | 251篇 |
1994年 | 250篇 |
1993年 | 240篇 |
1992年 | 102篇 |
1991年 | 116篇 |
1990年 | 89篇 |
1989年 | 112篇 |
1988年 | 74篇 |
1987年 | 68篇 |
1986年 | 62篇 |
1985年 | 82篇 |
1984年 | 63篇 |
1983年 | 63篇 |
1982年 | 75篇 |
1981年 | 66篇 |
1980年 | 49篇 |
1979年 | 42篇 |
1978年 | 42篇 |
1977年 | 85篇 |
1976年 | 108篇 |
1975年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
91.
92.
F Gaymard G Pilot B Lacombe D Bouchez D Bruneau J Boucherez N Michaux-Ferrière JB Thibaud H Sentenac 《Canadian Metallurgical Quarterly》1998,94(5):647-655
SKOR, a K+ channel identified in Arabidopsis, displays the typical hydrophobic core of the Shaker channel superfamily, a cyclic nucleotide-binding domain, and an ankyrin domain. Expression in Xenopus oocytes identified SKOR as the first member of the Shaker family in plants to be endowed with outwardly rectifying properties. SKOR expression is localized in root stelar tissues. A knockout mutant shows both lower shoot K+ content and lower xylem sap K+ concentration, indicating that SKOR is involved in K+ release into the xylem sap toward the shoots. SKOR expression is strongly inhibited by the stress phytohormone abscisic acid, supporting the hypothesis that control of K+ translocation toward the shoots is part of the plant response to water stress. 相似文献
93.
94.
95.
96.
This paper describes the application of an expert system for the evaluation of the short-term thermal rating and temperature rise of overhead conductors. The expert system has been developed using a database and Leonardo expert system shell which is gaining popularity among commercial tools for developing expert system applications. The expert system has been found to compare well when evaluated against site tests. A practical application is given to demonstrate the usefulness of the expert system developed 相似文献
97.
B Amy de la Bretèque 《Canadian Metallurgical Quarterly》1995,116(4):271-272
The adolescent's breaking of the voice is the result of the substitution of the chest voice (or heavy mechanism) for the head voice (or light mechanism). In cases of late breaking, the voice is abnormally high-pitched and feeble, often with a distorted timbre, while the larynx is normal and pubescent. Such people are generally not fully aware of their voices' real nature. Therapy classically resorts to laryngeal manipulations, of which a new technique is put forward. Another therapeutic approach is based, on the one hand, on critical listening compared with a control male voice, thus enabling the subject to become aware of his own voice, and, on the other hand, on high intensity work which helps passing from head to chest voice. 相似文献
98.
This second article deals with using the Comsis software for a particular application. Simulation is used to determine the maximum channel density in presence of crosstalk. In a first part, the modelling of the system is described. The simulation parameters of different optical elements are given. The results show that in the case of channels modulated at 500 Mbitls using fsk modulation format, and a direct detection operation at 1,5 μm, a minimum spacing of 6 GHz can be obtained with a 2 dB penalty. Thus if only the bandwidth of the erbium doped fibre amplifier is taken into account, the maximum number of channels which can be used is 250. However if the fsr (free spectral range) of optical filter is taken into account, the maximun number of channels is limited to 30. 相似文献
99.
Activation of macrophages by T cells is considered an initiating event in glomerular crescent formation. Since interferon-gamma (INF gamma) is a key mediator in T-cell-mediated activation of macrophages, we decided to test its role in a model of crescentic glomerulonephritis. An anti-glomerular basement membrane (GBM) serum was injected intravenously in presensitized wild-type or IFN gamma receptor deficient (IFN gamma(R)-/-) mice. Glomerulonephritis with glomerular crescents and tubulointerstitial inflammation developed in both strains, even though most evaluated morphological parameters and proteinuria indicated a less severe pathology in the mutant mice compared to the wild type. Thus, IFN gamma is not essential either for glomerular crescent formation or for tubulointerstitial involvement in anti-GBM glomerulonephritis in mice. In conclusion, the role of macrophages in this model might have been overestimated, or other cytokines may compensate for deficient IFN gamma signaling in the activation of macrophages. 相似文献
100.