全文获取类型
收费全文 | 7648篇 |
免费 | 341篇 |
国内免费 | 54篇 |
专业分类
电工技术 | 137篇 |
综合类 | 26篇 |
化学工业 | 1852篇 |
金属工艺 | 126篇 |
机械仪表 | 240篇 |
建筑科学 | 299篇 |
矿业工程 | 7篇 |
能源动力 | 492篇 |
轻工业 | 776篇 |
水利工程 | 80篇 |
石油天然气 | 117篇 |
无线电 | 708篇 |
一般工业技术 | 1223篇 |
冶金工业 | 505篇 |
原子能技术 | 86篇 |
自动化技术 | 1369篇 |
出版年
2024年 | 24篇 |
2023年 | 154篇 |
2022年 | 323篇 |
2021年 | 416篇 |
2020年 | 302篇 |
2019年 | 346篇 |
2018年 | 428篇 |
2017年 | 367篇 |
2016年 | 370篇 |
2015年 | 246篇 |
2014年 | 333篇 |
2013年 | 678篇 |
2012年 | 374篇 |
2011年 | 524篇 |
2010年 | 368篇 |
2009年 | 347篇 |
2008年 | 310篇 |
2007年 | 236篇 |
2006年 | 215篇 |
2005年 | 156篇 |
2004年 | 127篇 |
2003年 | 128篇 |
2002年 | 100篇 |
2001年 | 67篇 |
2000年 | 82篇 |
1999年 | 56篇 |
1998年 | 111篇 |
1997年 | 60篇 |
1996年 | 63篇 |
1995年 | 58篇 |
1994年 | 46篇 |
1993年 | 59篇 |
1992年 | 44篇 |
1991年 | 37篇 |
1990年 | 33篇 |
1989年 | 25篇 |
1988年 | 41篇 |
1987年 | 37篇 |
1986年 | 26篇 |
1985年 | 20篇 |
1984年 | 30篇 |
1983年 | 27篇 |
1982年 | 28篇 |
1981年 | 21篇 |
1980年 | 25篇 |
1979年 | 17篇 |
1978年 | 24篇 |
1977年 | 20篇 |
1976年 | 27篇 |
1975年 | 21篇 |
排序方式: 共有8043条查询结果,搜索用时 0 毫秒
991.
992.
Throughout history, nuts have been a staple food providing energy, protein, essential fatty acids, vitamins, and minerals. Today, nuts are classified as part of the USDA Food Guide Pyramid's Meat/ Meat Alternate Group. Foods in this group contribute protein as well as important vitamins and minerals to the diet. Nuts are also being studied for their potential health benefits. Research suggests that there may be a connection between frequent nut consumption and a reduced incidence of coronary heart disease. Thus, tradition and promising scientific evidence combine to support the role of nuts in healthful eating. 相似文献
993.
Mohamed Chtourou Emna Ammar Moncef Nasri Khaled Medhioub 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2004,79(8):869-878
This study deals with the degradation of phenolic compounds in olive oil mill waste; a highly polluting material in olive oil‐producing countries because of its abundance and the toxicity of its phenolic compound content. This investigation confirms the ability of an isolated yeast, identified as Trichosporon cutaneum, to degrade phenolic compounds extracted from olive mill waste water (OMW). The yeast was adapted to the OMW by an enrichment culture. The results of this biotransformation were a decrease in the phenolic content and hence a reduction in the phytotoxic effects of the effluent after the yeast treatment. The kinetic growth of the isolated yeast on phenol over a range of concentrations (0.3–3.0 g dm?3) was studied. The ability of the strain to assimilate simple monomeric phenols and alkyl phenols, at a concentration of 1 g dm?3, in a synthetic liquid medium used as the sole carbon source was investigated in a batch culture. The aromatic ring cleavage pathway occurred in the yeast through catechol oxidation. Using various concentrations of ethyl acetate extract from OMW as the sole carbon source, the yeast exhibited growth on the substrate up to 7 g dm?3 equivalent of phenols. A significant reduction of COD after the treatment of the OMW extract by the yeast isolate was noticed. The removal of phenol and COD exceeded 80% of the original loading after 8 days of treatment, for extracts containing initial COD in the range 19 to 72 g dm?3. Copyright © 2004 Society of Chemical Industry 相似文献
994.
This paper discusses a process hazard management study of a fuel gas conditioning facility based on stateof-the-art fault tree analysis techniques. This facility lowers the water and hydrocarbon dewpoints of a high pressure fuel gas exposed to frigid temperatures during distribution. Using hazards checklists and guidelines as well as internal reviews, various process hazards were identified for this facility. Computerized fault tree analysis techniques were used to identify the failure sequences which could lead to process hazards, and analysts used these results to evaluate the impact of specific hazards upon process safety. Through recommendations presented in the study, the facility owner gained an increased awareness of potential problems and made modifications to reduce the possibility of a hazardous condition and subsequent catastrophic failure. 相似文献
995.
996.
Mikal Ziane Ph.D. Mohamed Zaït Ph.D. student Projet Rodin Pascale Borla-Salamet Ph.D. 《The VLDB Journal The International Journal on Very Large Data Bases》1993,2(3):277-301
In this article, we describe our approach to the compile-time optimization and parallelization of queries for execution in DBS3 or EDS. DBS3 is a shared-memory parallel database system, while the EDS system has a distributed-memory architecture. Because DBS3 implements a parallel dataflow execution model, this approach applies to both architectures. Using randomized search strategies enables the exploration of a search space large enough to include zigzag trees, which are intermediate between left-deep and right-deep trees. Zigzag trees are shown to provide better response time than right-deep trees in case of limited memory. Performance measurements obtained using the DBS3 prototype show the advantages of zigzag trees under various conditions. 相似文献
997.
Memorializes Edwin B. Newman (1908–1989). Newman served as chair of the Department of Psychology at Harvard University from 1948 to 1964. He researched the interaction of the problems of measurement and equipment. His investigations centered on the analysis of language and speech and on the technical challenges involved in their quantification. In 1929 he and Frederick Howell Lewis formed Psi Chi, the national honor society for psychology. He served the American Psychological Association in various capacities, including membership on the Board of Directors and the Publication Committee. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
998.
The authors have been investigating the adsorption and desorption dynamics of nonionic water soluble polymers on inorganic particles. The influence of the nature of polymers with and without associating hydrophobic end groups, the nature of adsorbents [TiO2, Al2O3 (neutral, acid and basic), and SiO2], polymer concentrations, linear velocity of fluids, and mutual diffusion of polymer molecules on the patterns of adsorption and desorption distribution of polymer concentrations are shown. The model polymer is a nonionic polyurethane polymer based on ethylene oxide. The polymer's structure is R-O-(DI-PEO)6-DI-O-R (R is C16H33, DI is isophorone diisocyanate, and PEO is CARBOWAXTM with a molecular weight of 8200). The phenomenological models of association and dissociation kinetics of associative polymers are suggested. The half-lives of clusters into adsorption and desorption layers are estimated. It is shown that heats of desorption of associative polymers are dependent essentially on heats of dissociation of clusters. 相似文献
999.
Mohamed Baba Soney George Jean Luc Gardette Jacques Lacoste 《Polymer International》2003,52(6):863-868
It was observed that crosslinking reactions resulting both from peroxide decomposition or photoageing at wavelengths longer than 300 nm involve a drastic decrease of the crystallinity of some dienic elastomers, such as polybutadienes (rich in cis 1,4 and 1,2 microstructures) and polycyclo‐octene. By comparing precisely the rate of decomposition of dicumyl peroxide and that of the crystallinity decrease, it was possible to show that the kinetics of crystallinity loss observed upon ageing can be identified with that of the crosslinking of elastomers. The results indicate that the crosslinking process can be followed directly by DSC measurement of the crystallization/melting cycle. © 2003 Society of Chemical Industry 相似文献
1000.
Graph traversals are in the basis of many distributed algorithms. In this paper, we use graph relabelling systems to encode two basic graph traversals which are the broadcast and the convergecast. This encoding allows us to derive formal, modular and simple encoding for many distributed graph algorithms. We illustrate this method by investigating the distributed computation of a breadth-first spanning tree and the distributed computation of a minimum spanning tree. Our formalism allows to focus on the correctness of a distributed algorithm rather than on the implementation and the communication details. 相似文献