全文获取类型
收费全文 | 1888篇 |
免费 | 121篇 |
专业分类
电工技术 | 23篇 |
化学工业 | 497篇 |
金属工艺 | 36篇 |
机械仪表 | 40篇 |
建筑科学 | 52篇 |
矿业工程 | 2篇 |
能源动力 | 92篇 |
轻工业 | 292篇 |
水利工程 | 16篇 |
石油天然气 | 12篇 |
无线电 | 122篇 |
一般工业技术 | 312篇 |
冶金工业 | 121篇 |
原子能技术 | 27篇 |
自动化技术 | 365篇 |
出版年
2024年 | 5篇 |
2023年 | 29篇 |
2022年 | 72篇 |
2021年 | 110篇 |
2020年 | 68篇 |
2019年 | 79篇 |
2018年 | 69篇 |
2017年 | 70篇 |
2016年 | 78篇 |
2015年 | 53篇 |
2014年 | 112篇 |
2013年 | 154篇 |
2012年 | 158篇 |
2011年 | 142篇 |
2010年 | 97篇 |
2009年 | 101篇 |
2008年 | 84篇 |
2007年 | 82篇 |
2006年 | 59篇 |
2005年 | 45篇 |
2004年 | 40篇 |
2003年 | 49篇 |
2002年 | 32篇 |
2001年 | 17篇 |
2000年 | 22篇 |
1999年 | 16篇 |
1998年 | 29篇 |
1997年 | 30篇 |
1996年 | 16篇 |
1995年 | 11篇 |
1994年 | 9篇 |
1993年 | 20篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 9篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1972年 | 1篇 |
1971年 | 2篇 |
排序方式: 共有2009条查询结果,搜索用时 31 毫秒
1.
Lissy Z. F. Gross Mariana Sacerdoti Prof. Albrecht Piiper Prof. Stefan Zeuzem Dr. Alejandro E. Leroux Dr. Ricardo M. Biondi 《ChemMedChem》2020,15(18):1682-1690
Angiotensin converting enzyme 2 (ACE2) is the human receptor that interacts with the spike protein of coronaviruses, including the one that produced the 2020 coronavirus pandemic (COVID-19). Thus, ACE2 is a potential target for drugs that disrupt the interaction of human cells with SARS-CoV-2 to abolish infection. There is also interest in drugs that inhibit or activate ACE2, that is, for cardiovascular disorders or colitis. Compounds binding at alternative sites could allosterically affect the interaction with the spike protein. Herein, we review biochemical, chemical biology, and structural information on ACE2, including the recent cryoEM structures of full-length ACE2. We conclude that ACE2 is very dynamic and that allosteric drugs could be developed to target ACE2. At the time of the 2020 pandemic, we suggest that available ACE2 inhibitors or activators in advanced development should be tested for their ability to allosterically displace the interaction between ACE2 and the spike protein. 相似文献
2.
3.
Rossato Janine I.; Bonini Juliana S.; Coitinho Adriana S.; Vianna Monica R. M.; Medina Jorge H.; Cammarota Martín; Izquierdo Iván 《Canadian Metallurgical Quarterly》2004,118(3):563
The gamma aminobutyric acid-A (GABAA) agonist, muscimol, the glutamate N-methyl-D-aspartate (NMDA) receptor antagonist, D-2-amino-5-phosphonopentanoic acid (AP5), and the inhibitor of the extracellularly regulated kinases (ERKs), UO 126, cause retrograde amnesia when administered to the hippocampus. In the present study, the authors found that they all cause retrograde amnesia for 1-trial inhibitory avoidance, not only when infused into the dorsal CA1 region of the hippocampus, but also when infused into the basolateral amygdala or the entorhinal, parietal, and posterior cingulate cortices. The posttraining time course of the effect of each drug was, however, quite different across brain structures. Thus, in all of them, NMDA receptors and the ERK pathway are indispensable for memory consolidation, and GABAA receptor activation inhibits memory consolidation: but in each case, their influence is interwoven differently. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
4.
Christian P. Romero Jonathan I. Avila Edgardo Cisternas Guerau B. Cabrera Alejandro L. Cabrera Kristiaan Temst Margriet J. Van Bael 《Journal of Materials Science》2007,42(18):7667-7672
Hydrogen desorption curves were obtained from a sample composed of a square arrangement of Co dots with average diameter of
4.4 μm, separated by a distance of 11.6 μm. A macroscopic sample of Co dots grown on a 2.5 × 2.5 cm Si substrate was made
by standard lithographic techniques and used in these experiments. Thermal programmed desorption (TPD) was performed under
ultra-high vacuum conditions. Hydrogen TPD curves were obtained from a 1 × 1 cm Co dots samples displaying a maximum of intensity
at 425 K. Hydrogen TPD curve was also obtained from 1 cm× 1 cm samples of Co films and Co foils for comparison. The hydrogen
TPD curves have decreasing intensity from the Co foils to the Co dots and finally to the Co films. This indicates that there
are more sites for hydrogen adsorption on the Co dots than in the Co films. This is a surprising result because there is approximately
8.7 times less Co atoms exposed in the Co dots that in the Co film sample. A desorption energy of 27 kcal/mol was obtained
for the Co dots suggesting that hydrogen is adsorbed on an hcp hollow site of the Co dot crystalline structure. 相似文献
5.
This paper shows a few possibilities for the application of Community OR in a Third World country based on experience in Venezuela. These possibilities are discussed in a framework of the relationship between the state and community organizations. Emphasis lies in showing that Community OR in Venezuela requires a deep critical commitment to emancipation in order to help community organizations develop in a rather hostile environment. Lastly, results in dealing with community organizations in Venezuela using the Interpretive Systemology approach are presented. 相似文献
6.
N Schr?der A de Mattos-Dutra M Sampaio de Freitas CS Foga?a Lisboa AC Zilles R Pessoa-Pureur I Izquierdo 《Canadian Metallurgical Quarterly》1997,749(2):275-282
In the homodimeric hemoglobin from Scapharca, HbI, functional communication between the two heme groups is based on their direct structural linkage across the subunit interface through the heme propionates. The heme-protein interactions have been altered in deutero- and meso-HbI by substituting the vinyl groups at positions 2 and 4 of protoheme with hydrogen and ethyl groups, respectively. In meso-HbI the introduction of the ethyl groups in the heme pocket induces significant alterations in the conformation of the heme peripheral substituents, including the propionates, and in the structure of bound CO, as revealed by the resonance Raman spectra. The functional counterpart of these structural changes is the loss of cooperativity in carbon monoxide binding and in the rate of oxygen dissociation. Oxygen pulse and flash photolysis experiments indicate that meso-HbI is locked in the liganded conformation. It is postulated that the ethyl groups, which occupy a larger volume than vinyl ones, impair the ligand-linked movement of the heme relative to its pocket and in turn the expression of cooperativity. In deutero-HbI structural alterations have not been monitored. Functionally, cooperativity in the CO binding kinetics is increased as if hydrogen atoms at positions 2 and 4 permitted more marked movements of the heme than in the native protein. 相似文献
7.
In this article, we analyze a co-operative multi-thread search-based optimization strategy, where each solver thread represents a different optimization algorithm (or the same one with different settings), and they are all controlled by a centralized co-ordinator. We also propose the use of memory to keep track of both the state of the individual threads and the obtained solutions. Based on this memory, a very simple fuzzy rule base is used to control the system behavior.We also present the results of three computational experiments. The first of these checks the strategy by comparing it with an independent search strategy and a sequential algorithm, and the superiority of the co-operative scheme is confirmed. The second analyzes how definition of the threads affects the quality of the results, and the importance of there being a balanced set between intensification and diversification is corroborated. The third explores the use of memory with two different fuzzy rules, and the results indicate that the best combination is to use memory together with two rules (solver dependent and solver independent ones) (although this combination should not be activated at the beginning of the search in order to avoid premature convergence). 相似文献
8.
9.
The Grid shows itself as a globally distributed computing environment, in which hardware and software resources are virtualized to transparently provide applications with vast capabilities. Just like the electrical power grid, the Grid aims at offering a powerful yet easy‐to‐use computing infrastructure to which applications can be easily ‘plugged’ and efficiently executed. Unfortunately, it is still very difficult to Grid‐enable applications, since current tools force users to take into account many details when adapting applications to run on the Grid. In this paper, we survey some of the recent efforts in providing tools for easy gridification of applications and propose several taxonomies to identify approaches followed in the materialization of such tools. We conclude this paper by describing common features among the proposed approaches, and by pointing out open issues and future directions in the research and development of gridification methods. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
10.
Thermodynamic principles, involving mainly: (1) minimum reversible work of separation and (2) second-law analysis that accounts for irreversibility, are used to synthesize separation trains. These principles lead to a development and classification into two groups of many of the heuristics appearing in the literature. An efficient algorithm based on reversible thermodynamics leads to optimal structures for simple acyclic trains. Complex structures are efficiently synthesized by algorithms using reversible thermodynamics and second-law analysis. The procedures presented are depth-first algorithms. The optimal structures developed are shown to be strongly influenced by feed and product compositions. 相似文献