全文获取类型
收费全文 | 3791篇 |
免费 | 79篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 39篇 |
化学工业 | 511篇 |
金属工艺 | 104篇 |
机械仪表 | 93篇 |
建筑科学 | 129篇 |
矿业工程 | 5篇 |
能源动力 | 62篇 |
轻工业 | 352篇 |
水利工程 | 31篇 |
石油天然气 | 7篇 |
无线电 | 416篇 |
一般工业技术 | 452篇 |
冶金工业 | 1292篇 |
原子能技术 | 30篇 |
自动化技术 | 349篇 |
出版年
2021年 | 42篇 |
2020年 | 31篇 |
2019年 | 40篇 |
2018年 | 40篇 |
2017年 | 55篇 |
2016年 | 51篇 |
2015年 | 56篇 |
2014年 | 68篇 |
2013年 | 168篇 |
2012年 | 118篇 |
2011年 | 153篇 |
2010年 | 121篇 |
2009年 | 118篇 |
2008年 | 131篇 |
2007年 | 128篇 |
2006年 | 126篇 |
2005年 | 113篇 |
2004年 | 88篇 |
2003年 | 91篇 |
2002年 | 85篇 |
2001年 | 80篇 |
2000年 | 58篇 |
1999年 | 87篇 |
1998年 | 245篇 |
1997年 | 176篇 |
1996年 | 123篇 |
1995年 | 96篇 |
1994年 | 97篇 |
1993年 | 78篇 |
1992年 | 67篇 |
1991年 | 54篇 |
1990年 | 59篇 |
1989年 | 65篇 |
1988年 | 56篇 |
1987年 | 42篇 |
1986年 | 52篇 |
1985年 | 45篇 |
1984年 | 46篇 |
1983年 | 49篇 |
1982年 | 37篇 |
1981年 | 36篇 |
1980年 | 32篇 |
1979年 | 29篇 |
1978年 | 23篇 |
1977年 | 47篇 |
1976年 | 60篇 |
1974年 | 16篇 |
1972年 | 21篇 |
1971年 | 17篇 |
1970年 | 20篇 |
排序方式: 共有3872条查询结果,搜索用时 31 毫秒
1.
Felipe A. Perdomo Siti H. Khalit Claire S. Adjiman Amparo Galindo George Jackson 《American Institute of Chemical Engineers》2021,67(3):e17194
The SAFT-γ Mie group-contribution equation of state is used to represent the fluid-phase behavior of aqueous solutions of a variety of linear, branched, and cyclic amines. New group interactions are developed in order to model the mixtures of interest, including the like and unlike interactions between alkyl primary, secondary, and tertiary amine groups (NH2, NH, N), cyclic secondary and tertiary amine groups (cNH, cN), and cyclic methine-amine groups (cCHNH, cCHN) with water (H2O). The group-interaction parameters are estimated from appropriate experimental thermodynamic data for pure amines and selected mixtures. By taking advantage of the group-contribution nature of the method, one can describe the fluid-phase behavior of mixtures of molecules comprising those groups over broad ranges of temperature, pressure, and composition. A number of aqueous solutions of amines are studied including linear, branched aliphatic, and cyclic amines. Liquid–liquid equilibria (LLE) bounded by lower critical solution temperatures (LCSTs) have been reported experimentally and are reproduced here with the SAFT-γ Mie approach. The main feature of the approach is the ability not only to represent accurately the experimental data employed in the parameter estimation, but also to predict the vapor–liquid, liquid–liquid, and vapor–liquid–liquid equilibria, and LCSTs with the same set of parameters. Pure compound and binary phase diagrams of diverse types of amines and their aqueous solutions are assessed in order to demonstrate the main features of the thermodynamic and fluid-phase behavior. 相似文献
2.
Kathryn C. Sole John Parker Peter M. Cole Michael B. Mooiman 《Mineral Processing and Extractive Metallurgy Review》2019,40(3):194-206
The price of cobalt has increased by some 450% in the past two years, mainly due to increasing demand for lithium–ion batteries. With an official 2017 production of 64 kt, the Democratic Republic of Congo produces more than half of the world’s cobalt. African Copperbelt operations have traditionally focused on copper production; however, it has now become imperative to also consider cobalt recovery from these ores. A plethora of processing routes is possible. Most hydrometallurgical flowsheets recover cobalt from the raffinate of the low-grade copper solvent-extraction circuit. Downstream purification processes include sequential precipitation with a variety of reagents, solvent extraction, and ion exchange. Product choices include hydroxide, carbonate, sulfate, and metal cathode. This study assesses technical and economic advantages and limitations of various approaches to the hydrometallurgical processing of cobalt in an African context. 相似文献
3.
Dr. Emilianne M. Limbrick Audrey E. Yñigez-Gutierrez Callie C. Dulin Dagmara K. Derewacz Dr. Jeffrey M. Spraggins Dr. Kathryn M. McCulloch Prof. T. M. Iverson Prof. Brian O. Bachmann 《Chembiochem : a European journal of chemical biology》2020,21(23):3349-3358
Everninomicins are orthoester oligosaccharide antibiotics with potent activity against multidrug-resistant bacterial pathogens. Everninomicins act by disrupting ribosomal assembly in a distinct region in comparison to clinically prescribed drugs. We employed microporous intergeneric conjugation with Escherichia coli to manipulate Micromonospora for targeted gene-replacement studies of multiple putative methyltransferases across the octasaccharide scaffold of everninomicin effecting the A1, C, F, and H rings. Analyses of gene-replacement and genetic complementation mutants established the mutability of the everninomicin scaffold through the generation of 12 previously unreported analogues and, together with previous results, permitted assignment of the ten methyltransferases required for everninomicin biosynthesis. The in vitro activity of A1- and H-ring-modifying methyltransferases demonstrated the ability to catalyze late-stage modification of the scaffold on an A1-ring phenol and H-ring C-4’ hydroxy moiety. Together these results establish the potential of the everninomicin scaffold for modification through mutagenesis and in vitro modification of advanced biosynthetic intermediates. 相似文献
4.
5.
6.
van Dick Rolf; Wagner Ulrich; Pettigrew Thomas F.; Christ Oliver; Wolf Carina; Petzel Thomas; Castro Vanessa Smith; Jackson James S. 《Canadian Metallurgical Quarterly》2004,87(2):211
Furthering G. W. Allport's (1954) contentions for optimal contact, the authors introduce a new construct: the perceived importance of contact. They propose that perceived importance is the best proximal predictor of contact's reduction of prejudice. If individuals have opportunities for contact at work or in the neighborhood, their chances to have intergroup acquaintances and friends increase. Intergroup contact among acquaintances and friends can be perceived as more or less important, which in turn determines intergroup evaluations. A 1st study shows that the new measure of perceived importance is indeed distinct from established quantity and quality indicators. The results are cross-validated in a 2nd study that also sheds light on the meaning of importance. In 3rd and 4th studies, structural equation analyses and a meta-analysis support the hypotheses. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
7.
8.
9.
The product from the hydrogenation of an iron-tin treated Morwell, Victorian coal was separated into a number of fractions by solvent separation. Each of these fractions (tetrahydrofuran-insoluble materials, asphaltols, asphaltenes and oils) was reacted separately with hydrogen in tetralin both with and without added catalysts. The effect of added catalyst and of temperature, pressure, time and solvent on the hydrocracking and repolymerization reactions is discussed. The interconvertibility of the brown coal-derived products is clearly established, reinforcing the importance of incorporating reversibility of reactions in mechanistic models developed to describe coal hydroliquefaction. 相似文献
10.
We consider the dynamics of a dark soliton in an elongated harmonically trapped Bose-Einstein condensate. A central question
concerns the behavior at finite temperatures, where dissipation arises due to the presence of a thermal cloud. We study this
problem using coupled Gross-Pitaevskii and N-body simulations, which include the mean field coupling between the condensate and thermal cloud. We find that the soliton
decays relatively quickly even at very low temperatures, with the decay rate increasing with rising temperature. 相似文献