全文获取类型
收费全文 | 1063篇 |
免费 | 36篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 13篇 |
综合类 | 11篇 |
化学工业 | 344篇 |
金属工艺 | 12篇 |
机械仪表 | 18篇 |
建筑科学 | 83篇 |
矿业工程 | 4篇 |
能源动力 | 17篇 |
轻工业 | 110篇 |
水利工程 | 5篇 |
石油天然气 | 1篇 |
无线电 | 50篇 |
一般工业技术 | 179篇 |
冶金工业 | 130篇 |
原子能技术 | 10篇 |
自动化技术 | 114篇 |
出版年
2022年 | 15篇 |
2021年 | 22篇 |
2020年 | 10篇 |
2019年 | 14篇 |
2018年 | 7篇 |
2017年 | 14篇 |
2016年 | 18篇 |
2015年 | 25篇 |
2014年 | 38篇 |
2013年 | 58篇 |
2012年 | 47篇 |
2011年 | 62篇 |
2010年 | 40篇 |
2009年 | 39篇 |
2008年 | 41篇 |
2007年 | 36篇 |
2006年 | 36篇 |
2005年 | 31篇 |
2004年 | 31篇 |
2003年 | 23篇 |
2002年 | 30篇 |
2001年 | 22篇 |
2000年 | 22篇 |
1999年 | 27篇 |
1998年 | 42篇 |
1997年 | 33篇 |
1996年 | 23篇 |
1995年 | 16篇 |
1994年 | 17篇 |
1993年 | 22篇 |
1992年 | 19篇 |
1991年 | 16篇 |
1990年 | 6篇 |
1989年 | 19篇 |
1988年 | 7篇 |
1987年 | 17篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 5篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 18篇 |
1980年 | 9篇 |
1979年 | 15篇 |
1978年 | 9篇 |
1977年 | 8篇 |
1976年 | 9篇 |
1975年 | 11篇 |
1974年 | 10篇 |
1973年 | 5篇 |
排序方式: 共有1101条查询结果,搜索用时 0 毫秒
1.
Dr. Tomasz Ratajczyk Prof. Dr. Gerd Buntkowsky Dr. Torsten Gutmann Dr. Bartłomiej Fedorczyk Dr. Adam Mames Dr. Mariusz Pietrzak Zuzanna Puzio Piotr Grzegorz Szkudlarek 《Chembiochem : a European journal of chemical biology》2021,22(5):855-860
The biorelevant PyFALGEA oligopeptide ligand, which is selective towards the epidermal growth factor receptor (EGFR), has been successfully employed as a substrate in magnetic resonance signal amplification by reversible exchange (SABRE) experiments. It is demonstrated that PyFALGEA and the iridium catalyst IMes form a PyFALGEA:IMes molecular complex. The interaction between PyFALGEA:IMes and H2 results in a ternary SABRE complex. Selective 1D EXSY experiments reveal that this complex is labile, which is an essential condition for successful hyperpolarization by SABRE. Polarization transfer from parahydrogen to PyFALGEA is observed leading to significant enhancement of the 1H NMR signals of PyFALGEA. Different iridium catalysts and peptides are inspected to discuss the influence of their molecular structures on the efficiency of hyperpolarization. It is observed that PyFALGEA oligopeptide hyperpolarization is more efficient when an iridium catalyst with a sterically less demanding NHC ligand system such as IMesBn is employed. Experiments with shorter analogues of PyFALGEA, that is, PyLGEA and PyEA, show that the bulky phenylalanine from the PyFALGEA oligopeptide causes steric hindrance in the SABRE complex, which hampers hyperpolarization with IMes. Finally, a single-scan 1H NMR SABRE experiment of PyFALGEA with IMesBn revealed a unique pattern of NMR lines in the hydride region, which can be treated as a fingerprint of this important oligopeptide. 相似文献
2.
3.
L Fr?yland DK Asiedu H Vaagenes A Garras O Lie GK Totland RK Berge 《Canadian Metallurgical Quarterly》1995,36(12):2529-2540
The mechanism behind the hypolipidemic effect of tetradecylthioacetic acid (CMTTD, a non-beta-oxidizable 3-thia fatty acid) was studied in hamsters fed a high cholesterol diet (2%), which resulted in hyperlipidemia. Treating hyperlipidemic hamsters with CMTTD resulted in a progressive hypocholesterolemic and hypotriacylglycerolemic effect. Decreased plasma cholesterol was followed by a 39% and 30% reduction in VLDL-cholesterol and LDL-cholesterol, respectively. In contrast, the HDL-cholesterol content was not affected, thus decreasing the VLDL-cholesterol/HDL-cholesterol and LDL-cholesterol/HDL-cholesterol ratios. 3-Hydroxy-3-methylglutaryl- (HMG) CoA reductase activity and its mRNA level were unchanged after CMTTD administration. Also, the LDL receptor and LDL receptor-related protein (LRP-4) mRNAs were unchanged. The decrease in plasma triacylglycerol was accompanied by a 45% and 56% reduction in VLDL-triacylglycerol and LDL-triacylglycerol, respectively. The hypolipidemic effect of CMTTD was followed by a 1.4-fold increase in mitochondrial fatty acid oxidation and a 2.3-fold increase in peroxisomal fatty acid oxidation. CMTTD treatment led to an accumulation of dihomo-gamma-linolenic acid (20:3n-6) in liver, plasma, very low density lipoprotein, and heart. Noteworthy, CMTTD accumulated more in the heart, plasma, and VLDL particles compared to the liver, and in the VLDL particle alpha-linolenic acid (18:3n-3) decreased whereas eicosatetraenoic acid (20:4n-3) increased. In addition, linoleic acid (18:2n-6) and the total amount of polyunsaturated fatty acids decreased, the latter mainly due to a decrease in n-6 fatty acids. The present data show that CMTTD was detected in plasma and incorporated into VLDL, liver, and heart. The relative incorporation (mol%) of CMTTD was heart > VLDL > liver. In conclusion, CMTTD causes both a hypocholesterolemic and hypotriacylglycerolemic effect in hyperlipidemic hamsters. 相似文献
4.
Semantic Web Mining: State of the art and future directions 总被引:2,自引:0,他引:2
Semantic Web Mining aims at combining the two fast-developing research areas Semantic Web and Web Mining. This survey analyzes the convergence of trends from both areas: More and more researchers are working on improving the results of Web Mining by exploiting semantic structures in the Web, and they make use of Web Mining techniques for building the Semantic Web. Last but not least, these techniques can be used for mining the Semantic Web itself.The Semantic Web is the second-generation WWW, enriched by machine-processable information which supports the user in his tasks. Given the enormous size even of today’s Web, it is impossible to manually enrich all of these resources. Therefore, automated schemes for learning the relevant information are increasingly being used. Web Mining aims at discovering insights about the meaning of Web resources and their usage. Given the primarily syntactical nature of the data being mined, the discovery of meaning is impossible based on these data only. Therefore, formalizations of the semantics of Web sites and navigation behavior are becoming more and more common. Furthermore, mining the Semantic Web itself is another upcoming application. We argue that the two areas Web Mining and Semantic Web need each other to fulfill their goals, but that the full potential of this convergence is not yet realized. This paper gives an overview of where the two areas meet today, and sketches ways of how a closer integration could be profitable. 相似文献
5.
Gerd Breitbach 《Nuclear Engineering and Design》1989,114(1)
At very high temperatures loaded metallic structures undergo creep deformations. The generated creep strains are connected with stress relaxations, stress redistributions and/or progressive deformations.In mainly load controlled situations the behaviour of the material can be described by a nonlinear viscous flow law (Norton power law).A stress-deformation analysis of complex structures can be carried out by finite element codes in which the mentioned constitutive equation is implemented. The code PERMAS-VISCOUS was used to analyse the stress state of a notched tension bar and the deformation behaviour of a tube under external pressure undergoing a creep collapse. The relation to experimental findings is also given. 相似文献
6.
7.
Palmitoyl-CoA hydrolase [EC 3.1.2.2.] activity in rat liver was found to be enhanced by high fat diets. Partially hydrogenated
marine oil and high-erucic acid rapeseed oil diets produced a greater increase than a diet containing soybean oil.
With diets containing from 5 to 30% (w/w) of partially hydrogenated marine oil the increase in palmitoyl-CoA hydrolase activity
was similar to the increase observed in peroxisomal β-oxidation activity (correlation coefficient r=0.94). A positive correlation
(r=0.86) also was observed between the activity of palmitoyl-CoA hydrolase and previously determined levels of long-chain
acyl-CoA.
The results presented may suggest a common “induction” mechanism for palmitoyl-CoA hydrolase and peroxisomal β-oxidation enzymes,
possibly exerted through an increased cellular level of long-chain acyl-CoA. 相似文献
8.
The kinetics of the chlorine evolution on carbon from a silver chloride melt have been studied at several temperatures using the steady state method and galvanostatic methods. Measurements with the double pulse method show that the charge transfer reaction is fast. The Tafel curves indicate that two parallel desorption reactions have about the same rate. The apparent heat of activation have been determined for the various reaction steps. 相似文献
9.
A commercial lithium aluminosilicate glass-ceramic material is investigated by high-resolution transmission electron microscopy after different heat treatments. Evidence is presented that epitaxy of β-quartz crystals on ZrTiO4 -type crystallites is the critical step initiating silicate crystallization. 相似文献
10.