全文获取类型
收费全文 | 525287篇 |
免费 | 7110篇 |
国内免费 | 1469篇 |
专业分类
电工技术 | 9559篇 |
综合类 | 526篇 |
化学工业 | 78655篇 |
金属工艺 | 19960篇 |
机械仪表 | 15190篇 |
建筑科学 | 12665篇 |
矿业工程 | 2269篇 |
能源动力 | 14516篇 |
轻工业 | 47053篇 |
水利工程 | 5219篇 |
石油天然气 | 9334篇 |
武器工业 | 37篇 |
无线电 | 59910篇 |
一般工业技术 | 101756篇 |
冶金工业 | 103495篇 |
原子能技术 | 10558篇 |
自动化技术 | 43164篇 |
出版年
2022年 | 3159篇 |
2021年 | 4893篇 |
2020年 | 3477篇 |
2019年 | 4553篇 |
2018年 | 7808篇 |
2017年 | 7607篇 |
2016年 | 7932篇 |
2015年 | 5559篇 |
2014年 | 9241篇 |
2013年 | 24065篇 |
2012年 | 14625篇 |
2011年 | 20142篇 |
2010年 | 15797篇 |
2009年 | 17693篇 |
2008年 | 18089篇 |
2007年 | 17775篇 |
2006年 | 15503篇 |
2005年 | 14208篇 |
2004年 | 13599篇 |
2003年 | 13397篇 |
2002年 | 12633篇 |
2001年 | 12830篇 |
2000年 | 11867篇 |
1999年 | 12594篇 |
1998年 | 32811篇 |
1997年 | 22895篇 |
1996年 | 17446篇 |
1995年 | 13033篇 |
1994年 | 11283篇 |
1993年 | 10972篇 |
1992年 | 7913篇 |
1991年 | 7417篇 |
1990年 | 7261篇 |
1989年 | 7013篇 |
1988年 | 6468篇 |
1987年 | 5766篇 |
1986年 | 5655篇 |
1985年 | 6265篇 |
1984年 | 5900篇 |
1983年 | 5170篇 |
1982年 | 4900篇 |
1981年 | 4966篇 |
1980年 | 4705篇 |
1979年 | 4609篇 |
1978年 | 4408篇 |
1977年 | 5334篇 |
1976年 | 6971篇 |
1975年 | 3796篇 |
1974年 | 3550篇 |
1973年 | 3665篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Photonic networks based on the optical path concept and wavelength division multiplexing (WDM) technology require unique operation, administration, and maintenance (OAM) functions. In order to realize the required OAM functions, the optical path network must support an effective management information transfer method. The method that superimposes a pilot tone on the optical signal appears very interesting for optical path overhead transfer. The pilot tone transmission capacity is determined by the carrier to noise ratio which depends on the power spectral density of the optical signal. The pilot tone transmission capacity of an optical path network employing WDM technology is elucidated; 4.5 kb/s transmission can be realized when the pilot tone modulation index is set at 3% 相似文献
82.
83.
84.
F. Cioffi E. M. Cohen Richard Badick 《Drug development and industrial pharmacy》1993,19(14):1741-1746
Carstensen and Rhodes1 have suggested that when, in stability programs, assays cannot be performed immediately after the protocol-designated storage time, then freezing them until such a time when assays can be performed would be a reasonable manner to retain the protocol schedule. They caution, however, that such a procedure may not be valid for dissolution data. The article to follow deals with real-time data showing that such a process is feasible for Nalidixic Acid tablets (and presumably for other tablets as well), and that, furthermore, the dissolution pattern would seem to be “frozen” as well. 相似文献
85.
86.
M. Ronen 《Journal of Computer Assisted Learning》1995,11(3):141-156
Abstract This article presents a study of a large scale incorporation of one data acquisitionsystem into physics teaching in Israel. By 1994 about 30% of the schools throughout the country used the V-scope, a 3-D multibody motion tracing system, in their lab programme. The views and reactions of post-training teachers, experienced teachers and students on various aspects of using the system are described, analysed and compared. 相似文献
87.
N. M. Sanghavi Hema Venkatesh Varsha Tandel 《Drug development and industrial pharmacy》1994,20(7):1275-1283
Gilbenclamide, a widely used potent hypoglycaemic agent was solubllized using β -Cyclodextrin and β -Cyclodextrin derivatives. Complexes were prepared by kneading method in a molar ratio of 1:1 of the drug and the cyclodextrlns respectively. The Glibenclamide β -Cyelocextrin complex was characterized and evaluated by I.R. studies, Differential Scanning Calorimotry 6 X-ray diffractometry. The in-vitro dissolution rates of drug from inclusion complexes of β Cyclodextrins and its derivatives were compared. A significant Improvement In dissolution lor, rates of Gllbenclamide was observed with Inclusion complexes of all the Cyclodextrins. However, the solubilizing effect was more in case of β-Cyclodextrin derivatives. 相似文献
88.
89.
M. D. Korostash 《Drying Technology》1985,3(4):603-611
The paper presents the results of research in the convection drying of unidirectional glass fibre bobbins on the basis of which the relations are suggested required to calculate the process of drying in the design of drying equipment. 相似文献
90.
Field surveys of a series of conjugated diunsaturated straight-chain primary alcohols, acetates, and aldehydes (dienes), including the 3,5-dode-cadienyl, 8,10-dodecadienyl, 3,5-tetradecadienyl, 8,10-tetradecadienyl, 9,11-tetradecadienyl, and 10,12-tetradecadienyl primary alcohols, acetates, and most aldehydes, and the related monounsaturated straight-chain primary alcohols, acetates, and aldehydes (monoenes), including the 3-dodecadienyl alcohol and acetates, attracted the following species from the title families. Diene attractants have been demonstrated for at least onePhyllonorycter sp.,Chionodes lugubrella (Fabr.),Leptostales ferruminaria (Zell.),Drepana bilineata (Pack.),Pyrausta fodinalis (Led.),Notocelia purpurissatana Heinr.,Phaneta alterana Heinr. Monoene attractants were demonstrated forHedya separatana (Kft.),Cydia fletcherana (Kft.),Barbara mappana Free.,Ancylis burgessiana (Zell.),Ancylis nubeculana Clem.,Evippe prunifoliella Cham.,Phlyctaenia coronata tertialis (Gn.), aChionodes sp., a Gelechiidae sp., and an unidentifiedPhyllonorycter sp. Replicated field experiments showed attraction-inhibition relationships for most species. Electroantennagram data are presented forLeptostales ferruminaria andDrepana bilineata. 相似文献