全文获取类型
收费全文 | 2347篇 |
免费 | 24篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 22篇 |
化学工业 | 149篇 |
金属工艺 | 14篇 |
机械仪表 | 19篇 |
建筑科学 | 53篇 |
矿业工程 | 2篇 |
能源动力 | 15篇 |
轻工业 | 92篇 |
水利工程 | 4篇 |
无线电 | 197篇 |
一般工业技术 | 205篇 |
冶金工业 | 1456篇 |
原子能技术 | 16篇 |
自动化技术 | 129篇 |
出版年
2021年 | 12篇 |
2020年 | 12篇 |
2019年 | 8篇 |
2018年 | 14篇 |
2017年 | 9篇 |
2016年 | 11篇 |
2015年 | 8篇 |
2014年 | 27篇 |
2013年 | 36篇 |
2012年 | 27篇 |
2011年 | 38篇 |
2010年 | 37篇 |
2009年 | 47篇 |
2008年 | 38篇 |
2007年 | 40篇 |
2006年 | 40篇 |
2005年 | 25篇 |
2004年 | 28篇 |
2003年 | 35篇 |
2002年 | 27篇 |
2001年 | 28篇 |
2000年 | 21篇 |
1999年 | 70篇 |
1998年 | 431篇 |
1997年 | 228篇 |
1996年 | 144篇 |
1995年 | 94篇 |
1994年 | 85篇 |
1993年 | 99篇 |
1992年 | 27篇 |
1991年 | 29篇 |
1990年 | 29篇 |
1989年 | 40篇 |
1988年 | 29篇 |
1987年 | 37篇 |
1986年 | 35篇 |
1985年 | 47篇 |
1984年 | 22篇 |
1983年 | 19篇 |
1982年 | 20篇 |
1981年 | 28篇 |
1980年 | 17篇 |
1979年 | 20篇 |
1978年 | 11篇 |
1977年 | 38篇 |
1976年 | 99篇 |
1975年 | 16篇 |
1974年 | 12篇 |
1973年 | 10篇 |
1971年 | 11篇 |
排序方式: 共有2373条查询结果,搜索用时 15 毫秒
81.
Richard L. Schwartz 《Computer Languages, Systems and Structures》1978,3(2):75-94
A design for a separate compilation facility for the SIMULA 67 programming language is presented. The paper explores the problems with existing separate compilation schemes, and proposes a new scheme that allows top-down, bottom-up, or even parallel development and integration of program modules. An evaluation of the proposal and a discussion of its applicability to other languages are then given. 相似文献
82.
83.
84.
In their recent review of instrumental conditioning of autonomic functions, E. S. Katkin and E. N. Murray (see 42: criticized most of the existing studies on the human level as artifactual on 1 or more grounds. The criteria they employed for rejecting these demonstrations are themselves open to criticism, however. Specifically, it is argued that (1) peripheral or cognitive mediation hypotheses are unlikely alternative explanations of the obtained results; (2) an increase in response frequency over a preconditioning operant level is not a necessary condition for demonstrating an increase in response probability with contingent reinforcement; and (3) yoked-control designs, frequently used in this research, do not automatically invalidate experiments in which they are employed. It is concluded that the strongest hypothesis to account for the existing data remains the direct instrumental strengthening of autonomic activity. (35 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
85.
86.
A computational method of temperature distribution calculation for building elements in two- and three-dimensional time-dependent heat flow problems is developed with a general approximate solution using, as a numerical approach, the finite difference method. An analytical evaluation method of the accuracy of calculations is developed. The method described was compared with experimental values and good correspondence was obtained. The time-dependent study which is presented includes thermal resistance and inertia (heat capacity) of the components' materials and different geometric compositions. 相似文献
87.
D. P. Saccuzzo and D. L. Schubert (see record 1981-28173-001) proposed that schizophrenic individuals have deficient posticonic processes. The deficiency accounts for the observed general slowness in visual information processing. It is argued that a major methodological mistake in the choice of target durations in a backward masking task invalidates Saccuzzo and Schubert's conclusions. (1 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
88.
The purpose of this study was to evaluate sustained drug release after melt granulation and heat treatment. Theophylline (anhydrous) and phenylpropanolamine hydrochloride (PPA) were used as model drugs. Compritol® 888 ATO (Glyceryl Behenate NF) was incorporated as the wax matrix material. Formulations with drug:wax in 3:1 and 1:1 ratios were evaluated. Tablets were made by dry blending or melt granulation; some of the tablets were heat treated at 80°C for 30 min. Tablets with or without heat treatment were tested for drug release using in vitro drug dissolution. The results showed that melt granulation gave slower drug release than dry blending. Heat treatment further retarded drug release for both dry blending and melt granulation. The drug release rates for theophylline were slower than for PPA at the same wax level and processing method. The drug release profiles were linear using a square root of time scale. In conclusion, melt granulation and heat treatment slowed drug release for the wax matrix-controlled release tablets. Heat treatment of the tablets made by melt granulation further retarded drug release. Heat treatment redistributed the wax, forming a new matrix system with higher tortuosity. The application of melt granulation or heat treatment can successfully retard drug release. 相似文献
89.
ED Kouvelas CE Savakis ET Tzebelikos G Bonatsos S Mitrossilis 《Canadian Metallurgical Quarterly》1976,32(9):1136-1138
The specific activity of histamine methyltransferase of rat brain increases rapidly from the 16th until the 25th day of gestation (7 days after birth). The specific activity of phenylethanolamine-N-methyl-transferase shows a rapid increase during the 1st and the 2nd week after birth, the adult values being obtained by the end of the 2nd week. 相似文献
90.
Viviane Schwartz Hong Xie Harry M. Meyer III Steven H. Overbury Chengdu Liang 《Carbon》2011,(2):659-668
Graphitic mesoporous carbon was modified with phosphorous heteroatoms in order to tune the catalytic selectivity and to investigate the roles of different oxygen species for the oxidative dehydrogenation reaction of isobutane to isobutene. Small changes in the isobutane apparent activation energy are consistent with the notion that the phosphorous groups do not change the nature of the active sites but they interfere with the availability of the sites. Our results show that the improvement on selectivity is not proportional to the amount of phosphorous added. Small phosphorous content improved the selectivity by suppressing the combustion of isobutane. However, a higher amount of phosphorous groups lead to coverage of selective quinone sites and/or creation of active sites favorable to total oxidation. 相似文献