全文获取类型
收费全文 | 19310篇 |
免费 | 2141篇 |
国内免费 | 524篇 |
专业分类
电工技术 | 107篇 |
综合类 | 669篇 |
化学工业 | 5637篇 |
金属工艺 | 136篇 |
机械仪表 | 413篇 |
建筑科学 | 120篇 |
矿业工程 | 15篇 |
能源动力 | 61篇 |
轻工业 | 11883篇 |
水利工程 | 34篇 |
石油天然气 | 743篇 |
武器工业 | 5篇 |
无线电 | 530篇 |
一般工业技术 | 903篇 |
冶金工业 | 95篇 |
原子能技术 | 90篇 |
自动化技术 | 534篇 |
出版年
2024年 | 154篇 |
2023年 | 429篇 |
2022年 | 1073篇 |
2021年 | 1454篇 |
2020年 | 734篇 |
2019年 | 842篇 |
2018年 | 672篇 |
2017年 | 761篇 |
2016年 | 663篇 |
2015年 | 789篇 |
2014年 | 929篇 |
2013年 | 1102篇 |
2012年 | 1291篇 |
2011年 | 1313篇 |
2010年 | 973篇 |
2009年 | 864篇 |
2008年 | 806篇 |
2007年 | 1044篇 |
2006年 | 962篇 |
2005年 | 802篇 |
2004年 | 693篇 |
2003年 | 525篇 |
2002年 | 448篇 |
2001年 | 330篇 |
2000年 | 270篇 |
1999年 | 290篇 |
1998年 | 192篇 |
1997年 | 140篇 |
1996年 | 199篇 |
1995年 | 191篇 |
1994年 | 193篇 |
1993年 | 154篇 |
1992年 | 149篇 |
1991年 | 95篇 |
1990年 | 81篇 |
1989年 | 84篇 |
1988年 | 54篇 |
1987年 | 53篇 |
1986年 | 36篇 |
1985年 | 39篇 |
1984年 | 30篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1980年 | 32篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1976年 | 3篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
A series of experiments have been conducted using a recombinant baculovirus/insect cell expression system (Bm5/Bm5.NPV.CAT) to establish the optimum temperature for both cell growth and virus infection. Bm5 cell growth was found to be limited at temperatures below 22°C and ceased completely at temperatures above 34°C. In the range between 24 and 28°C, final cell densities always reached 96% of the highest achievable viable cell density. The shortest population doubling time was obtained at 28°C. Overall, a consistent increase in metabolism with increasing temperatures was observed. During the infection/viral replication phase, an increase in the temperature from 25 to 31°C resulted in a faster decrease in viable cell density and an earlier production of chloramphenicol acetyltransferase (CAT). Furthermore, protein yield at temperatures above 28°C was significantly reduced. Overall, the best temperature for the infection phase for the Bm5/Bm5.NPV expression system was found to be 25°C when the cells are cultured in serum free media. 相似文献
92.
Predictive modelling of the 3-D structure of interleukin-13 总被引:1,自引:0,他引:1
Bamborough Paul; Duncan David; Richards W.Graham 《Protein engineering, design & selection : PEDS》1994,7(9):1077-1082
Several atomic structures are now available for the family ofhelical cytokines, which includes growth hormone as well asmany of the interleukins. Using structural information fromfive members of this family, two alternative models of interleukin(IL)-13 are proposed. IL-13 has biological properties similarto those of IL-4 and, like the other interleukins, is a potentiallyimportant pharmaceutical target. The model of IL-13 is discussedand compared with the known interleukin structures. 相似文献
93.
磺化竹红菌素对蛋白质荧光猝灭机理的研究 总被引:1,自引:0,他引:1
本文详细研究了磺化竹红菌素对多种蛋白质在溶液状态下的荧光猝灭过程。结果表明,磺化竹红菌素对多种蛋白质荧光猝灭服从Sten-Volmer曲线。实验观察了温度、粘度、pH值和盐酸胍对荧光猝灭过程的影响。由于磺化竹红菌素是一两性分子,对于不同蛋白具有不同猝灭过程;磺化竹红菌素对蛋白质的荧光猝灭常数Kq在10^13mol/L.s^-1左右,这说明,磺化竹红菌素是一种比其它蛋白质荧光猝灭剂更加有效的荧光猝灭 相似文献
94.
大豆蛋白分离工艺研究 总被引:2,自引:0,他引:2
阐述了大豆蛋白质的分离原理,分析了运用“碱提酸沉”分离法提取大豆蛋白质过程中,豆粕的粉碎方式、浸提温度、浸提时间、浸提液的pH值以及离心工艺对提取效果的影响,为大豆蛋白/聚丙烯腈纤维的工业化生产提供了依据。 相似文献
95.
96.
Altschuh Daniele; Tessier Daniel C.; Vernet Thierry 《Protein engineering, design & selection : PEDS》1994,7(6):769-776
The two main catalytic residues Cys25 and Hisl59 of the monomericcysteine protease papain are located on different walls of acleft formed by two domains. This topology suggests a possiblerelationship between relative domain organization and catalyticmechanism. The effect on enzymatic parameters of structuralmodifications at various locations of the twodomain interfaceof papain was examined by individual or double replacementsby Ala of pairs of interacting residues. Most modificationshad no effect on enzyme activity. However, the enzyme's substrateturnover (kcat) decreased following simultaneous alterationof the two most conserved residues, forming an apolar contactlocated 15 Å away from the active site. The pH activityprofile of the double mutant was unchanged, indicating a conservedionization state of the active site thiolate-imidazolium ionpair. This state is strongly dependent on the distance separatingthe two residues, thus suggesting that the active site geometryhas not been significantly altered. Efficient enzymatic activityin papain requires more than a correct active site geometryand is influenced by domain packing properties in a region remotefrom the active site. 相似文献
97.
蛋白质分子链的超声速孤立子 总被引:3,自引:0,他引:3
在Davydov简谐蛋白质分子链模型的基础上,进行合理的连续近似处理,得到了超声速和亚声速孤立子解,并求得孤立子能量. 相似文献
98.
Whey is an undurable product. treated very often as a waste which pollutes the natural environment. Whey which is a valuable source of protein, lactose, vitamins and mineral salts should be utilized completely. The present paper is a proposal of whey drying on porous carriers. It is proved experimentally that the proposed drying method guarantees good product quality. 相似文献
99.
Responses of onion flies,Delia antiqua, to known attractants were measured in the laboratory with a novel tube-trap bioassay. The relative numbers of flies caught in tube traps baited with enzymatic yeast hydrolysate, brewer's yeast, andn-dipropyl disulfide were similar to those obtained previously with cone traps in the field. Changing the shape of the bioassay cage from a cuboid to a cylinder decreased the experimental error obtained from analysis of variance, as did rotating the floor of the circular cage. This bioassay should be useful in evaluating attractants for other insects that orient along the substrate.Diptera: Anthomyiidae.Paper No. 11327 of the Michigan State University Agricultural Experiment Station. Received for publication June 8, 1984. 相似文献
100.