全文获取类型
收费全文 | 2412篇 |
免费 | 71篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 23篇 |
综合类 | 5篇 |
化学工业 | 961篇 |
金属工艺 | 50篇 |
机械仪表 | 42篇 |
建筑科学 | 197篇 |
矿业工程 | 6篇 |
能源动力 | 66篇 |
轻工业 | 192篇 |
水利工程 | 26篇 |
石油天然气 | 2篇 |
武器工业 | 4篇 |
无线电 | 125篇 |
一般工业技术 | 313篇 |
冶金工业 | 137篇 |
原子能技术 | 32篇 |
自动化技术 | 304篇 |
出版年
2023年 | 18篇 |
2022年 | 22篇 |
2021年 | 53篇 |
2020年 | 29篇 |
2019年 | 29篇 |
2018年 | 35篇 |
2017年 | 26篇 |
2016年 | 65篇 |
2015年 | 58篇 |
2014年 | 55篇 |
2013年 | 104篇 |
2012年 | 91篇 |
2011年 | 130篇 |
2010年 | 104篇 |
2009年 | 106篇 |
2008年 | 99篇 |
2007年 | 84篇 |
2006年 | 91篇 |
2005年 | 82篇 |
2004年 | 64篇 |
2003年 | 45篇 |
2002年 | 52篇 |
2001年 | 46篇 |
2000年 | 51篇 |
1999年 | 63篇 |
1998年 | 56篇 |
1997年 | 61篇 |
1996年 | 53篇 |
1995年 | 54篇 |
1994年 | 44篇 |
1993年 | 29篇 |
1992年 | 41篇 |
1991年 | 40篇 |
1990年 | 31篇 |
1989年 | 40篇 |
1988年 | 26篇 |
1987年 | 31篇 |
1986年 | 29篇 |
1985年 | 23篇 |
1984年 | 30篇 |
1983年 | 27篇 |
1981年 | 29篇 |
1980年 | 24篇 |
1979年 | 19篇 |
1978年 | 20篇 |
1977年 | 22篇 |
1976年 | 18篇 |
1975年 | 18篇 |
1974年 | 21篇 |
1973年 | 19篇 |
排序方式: 共有2485条查询结果,搜索用时 4 毫秒
11.
改进的DMT/PTA工艺技术是由苏尔寿化工有限公司和H&G Hegmanns公司联合开发的。该技术对Witten-Katzschmann工艺进行了大量改进,并结合了苏尔寿公司的环境友好熔融结晶技术。改进的工艺包括:氧化反应部分(有效回收了副产品和能量);粗酯和副产品蒸馏;采用熔融结晶技术精制DMT。 相似文献
12.
Andreas Krell Paul Blank Hongwei Ma Thomas Hutzler Manfred Nebelung 《Journal of the American Ceramic Society》2003,86(4):546-53
Sintered corundum components with submicrometer grain sizes exhibit properties which enable numerous new applications. Wet powder processing is developed to associate minimum grain sizes at highest densities with the lowest population of macrodefects. A closest ratio of powder particle size and sintered grain size is important for obtaining most fine-grained microstructures. This target was approached best by using powders with particle sizes in the range of 100–200 nm rather than with smaller nanoparticles. 相似文献
13.
14.
Manfred Hampe 《化学,工程师,技术》1978,50(9):647-655
Liquid/liquid extraction: Applications and choice of solvent . The significance of liquid/liquid extraction has been steadily increasing in recent years as more and more stringent demands are made on the purity, availability, and environmental safety of chemical products. The use and success of this separation process are critically dependent upon the choice of the right extraction agent. Whereas solvent choice was previously mainly empirical, it is now possible to establish the suitability of a given solvent with the aid of molecular-thermodynamic data. This is demonstrated for the extraction of aromatic compounds. The article closes with an account of the formation and stability of emulsions. 相似文献
15.
High-purity monosilane for the electronics industry – Synthesis, purification, characterization. Monosilane is used in the electronics industry in the production of integrated circuits and in the manufacture of amorphous silicon devices such as solar cells, photocopier drums, and flat TV screens. The first German production unit for high purity monosilane gas which came on stream in 1987 is presented. The gas produced in a molten salt process is purified to highest quality and analyzed. 相似文献
16.
Dieter Braun Manfred Rtzsch Peter Fiedler Günter Weber Heinz Hofmann Bernd Gutschalk 《大分子材料与工程》1991,187(1):101-121
Based on the example of PE-LD grades and on model substances obtained by preparative fractionation (fractions in the molecular weight range M?w = 1.2 ? 390·104 g/mol), comprehensive investigations regarding the problems of structure/properties have been carried out. The correlations of M?w with 15 physical and application technological perameters have been investigated taking into account the reaction mechanism during the manufacturing of PE-LD in the tubular and agitated autoclave reactor, resulting in the formation of so-called primary structure perameters M?n, M?w, molar mass distribution, short chain branching and long chain branching. For the interpretation of the results, among other factors, also the morphological conditions have been taken into consideration, which in connection with the molecular parameters reveal — for specific M?w-ranges — strong changes and saturation ranges, resp., for the physical and application technological properties. 相似文献
17.
Meeting future energy demands with more efficient, lower emission, and safe energy technologies has top priority in the medium term. Consumer-friendly energy concepts, integrated into regional and supraregional energy supply structures, represent further elements. These will make important contributions to resource-conserving and environmentally compatible power supplies utilizing local energy sources including renewable resources. Supplying energy to large areas involves additional tasks, from compensation of large amounts of fluctuating energy to the transport of fluctuating energy to the transport of renewable energy over long distances. Solar dish, parabolic section, and tower power generating plant have considerable economic and CO2-reduction potential in sunny countries, such as in the Mediterranean region, However, the costs of solar-thermal electricity generation have to be reduced by a factor of 1.5 to 2. Fuel cell systems can attain particular significance as efficient low-emission energy conversion systems in power plant and automative engineering once their technical and economic potential can be realized. 相似文献
18.
19.
Matthias Berger Manfred P. Schnelder 《Journal of the American Oil Chemists' Society》1992,69(10):961-965
Regioisomerically pure 1(3)-rac-monoacylglycerols are conveniently prepared in high yields (>75%) and in multigram quantities by enzymatic esterification
of glycerol in the presence of various lipases(Chromobacterium viscosum, Rhizopus delemar, Rhizomucor miehei) with a variety of different acyl donors, such as free fatty acids, fatty acid alkyl esters, vinyl esters and triacylglycerols,
as well as natural fats and oils. All reactions are carried out in aprotic organic solvents with low water content, namelyn-hexane, diethyl ether, tBuOMe or mixtures of these solvents. Essential for the success of these transformations were the
following two factors. First, the creation of an artificial interphase between the solvent-immiscible hydrophilic glycerol
and the hydrophobic reaction medium by its adsorption onto a solid support. Second, a facile system for the separation of
the desired monoacylglycerol from the reaction mixture, coupled with the continuous recycling of acyl donor and undesirable
by-products. 相似文献
20.
Matthias Berger Kurt Laumen Manfred P. Schneider 《Journal of the American Oil Chemists' Society》1992,69(10):955-960
Regioisomerically pure 1,3-sn-diacylglycerols are conveniently prepared in high yields (>80%) and in large quantities by enzymatic esterification of glycerol
in the presence of various 1,3-selective lipases(Chromobacterium viscosum, Rhizopus delemar, Rhizomucor miehei) and a variety of different acyl donors like free fatty acids, fatty acid alkyl esters and vinyl esters. All reactions are
carried out in aprotic organic solvents of low water content, namelyn-hexane, diethyl ether or tBuOMe. The creation of an artificial interphase between the solvent-immiscible hydrophilic glycerol
and the hydrophobic reaction media by the adsorption of glycerol onto a solid support prior to use was essential for the success
of these transformations. The effects of reaction conditions and the regioselectivities of the lipases on the product yields
are described in detail. 相似文献