全文获取类型
收费全文 | 3297篇 |
免费 | 90篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 60篇 |
综合类 | 4篇 |
化学工业 | 1045篇 |
金属工艺 | 61篇 |
机械仪表 | 38篇 |
建筑科学 | 202篇 |
矿业工程 | 31篇 |
能源动力 | 52篇 |
轻工业 | 418篇 |
水利工程 | 15篇 |
石油天然气 | 2篇 |
无线电 | 164篇 |
一般工业技术 | 465篇 |
冶金工业 | 360篇 |
原子能技术 | 34篇 |
自动化技术 | 437篇 |
出版年
2022年 | 35篇 |
2021年 | 43篇 |
2020年 | 36篇 |
2019年 | 35篇 |
2018年 | 52篇 |
2017年 | 51篇 |
2016年 | 71篇 |
2015年 | 89篇 |
2014年 | 88篇 |
2013年 | 135篇 |
2012年 | 134篇 |
2011年 | 172篇 |
2010年 | 120篇 |
2009年 | 120篇 |
2008年 | 126篇 |
2007年 | 141篇 |
2006年 | 119篇 |
2005年 | 110篇 |
2004年 | 107篇 |
2003年 | 75篇 |
2002年 | 74篇 |
2001年 | 56篇 |
2000年 | 55篇 |
1999年 | 56篇 |
1998年 | 114篇 |
1997年 | 85篇 |
1996年 | 72篇 |
1995年 | 65篇 |
1994年 | 76篇 |
1993年 | 38篇 |
1992年 | 43篇 |
1991年 | 45篇 |
1990年 | 34篇 |
1989年 | 44篇 |
1988年 | 26篇 |
1987年 | 34篇 |
1986年 | 32篇 |
1985年 | 47篇 |
1984年 | 40篇 |
1983年 | 34篇 |
1982年 | 35篇 |
1981年 | 28篇 |
1980年 | 29篇 |
1978年 | 25篇 |
1977年 | 33篇 |
1976年 | 32篇 |
1975年 | 38篇 |
1974年 | 21篇 |
1973年 | 23篇 |
1970年 | 30篇 |
排序方式: 共有3388条查询结果,搜索用时 0 毫秒
1.
2.
Gerhard Mathé 《NTM》1994,2(1):13-26
This paper on the occasion of the 500th birthday of the great Saxon humanistic scholar Georgius Agricola deals with his contributions
to geology in the narrow sense. These, contrary to his voluminous works on mining, metallurgy and mineralogy (De re metallica and De natura fossilium, resp.) are parts of the booksDe ortu et causis subterraneorum andDe natura eorum, quae effluunt ex terra. In those we find statements on the causes of earthquakes, on volcanos and the subterranean fire as well as the effects of
the running water in mountain-building. Agricola's ideas on geological time and his statements on dynamics of the Earth's
crust are remarkable. 相似文献
3.
Dipl.-Ing. Gerhard Sauer 《Forschung im Ingenieurwesen》1995,61(5):134-140
Zusammenfassung Eine einfache Formel zur n?herungsweisen Berechnung der Axialspannungen eines Rohres infolge der von einer Temperaturschichtung
im Rohrinnern hervorgerufenen Temperaturfelder wird vorgestellt. Die Formel basiert auf der konventionellen Balkentheorie.
Durch Vergleiche der von der N?herungsformel gelieferten Axialspannungen mit den Axialspannungen, die mit Hilfe von Finite-Elemente-Rechnungen
erhalten werden, wird gezeigt, da? die N?herungsformel die maximalen Axialspannungen ausreichend genau wiedergibt. 相似文献
4.
5.
6.
7.
Studies of the microstructure of porous solids by physisorption measurements . The principal experimental methods for studying the microstructure of porous solids are based on physisorption measurements. The resulting sorption isotherms can yield data such as surface area and pore radius distribution, which are of great importance for development and characterization of porous catalysts. After a brief presentation of available measuring equipment, the main concern of this survey is the evaluation of sorption isotherms. In particular, methods for determining the micropore contribution to the total pore volume and the pore radius distribution in the micropore range are examined critically with regard to their reliability. 相似文献
8.
The applications of membrane separation within the bioconversion of lignocellulosic materials to ethanol are studied, and this paper reports on cellulolytic enzyme recovery, and reduction of the product inhibition. The conversion of cellulose and hemicellulose to hexoses and pentoses is carried out in a laboratory scale UF-membrane reactor, and the sugars, which have an inhibiting effect on the enzymes, are continuously removed with the permeate. By optimizing the space velocity, the enzyme inhibition is minimized and the rate of hydrolysis is significantly increased.The recovery of the enzymes has also been investigated with regard to their mechanical stability and adsorption on the substrate. Prior to enzymatic hydrolysis, the raw material is subjected to a pretreatment to make the cellulose more accessible to the enzymes, and the effect of the pretreatment can easily be evaluated in the UF-membrane reactor.As a result of the continuous removal of products formed in the hydrolysis, the permeate has a low content of fermentable sugars, and to give the optimal conditions for the fermentation a concentration step is needed. Different RO-membranes are tested in a laboratory scale batch cell to be able to choose a membrane material, fit for filtration in larger modules. 相似文献
9.
10.
Cholesterol 5α,6α-epoxide (α-epoxide) and cholesterol 5β,6β-epoxide (β-epoxide) were individually suspended in simulated gastric
juice (pH 1.2) at 37 C, and their reaction was followed by gradient high performance liquid chromatography (HPLC) with flame
ionization (FID) detection. Both epoxides reacted rapidly in the aqueous acid medium. The α-epoxide formed 6β-chlorocholestane-3β,5α-diol
(α-chlorohydrin) and 5α-cholestane-3β,5,6β-triol (triol), while the β-epoxide formed 5α-chlorocholestane-3β,6β-diol (β-chlorohydrin)
and triol. The isomeric chlorohydrins reacted further to form the triol. In mildly alkaline aqueous medium, each chlorohydrin
reverted to the epoxide from which it was formed. The data suggest that both epoxides, which have been reported to have adverse
health effects in animals, would be largely hydrolyzed in the stomach and to the triol, which also has been reported to have
biological activity. The data furher suggest that residual chlorohydrins surviving stomach residence can be expected to revert
to epoxide in the more alkaline intestinal environment. 相似文献