全文获取类型
收费全文 | 4664篇 |
免费 | 92篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 41篇 |
综合类 | 5篇 |
化学工业 | 546篇 |
金属工艺 | 58篇 |
机械仪表 | 55篇 |
建筑科学 | 137篇 |
矿业工程 | 22篇 |
能源动力 | 62篇 |
轻工业 | 327篇 |
水利工程 | 26篇 |
石油天然气 | 7篇 |
无线电 | 233篇 |
一般工业技术 | 603篇 |
冶金工业 | 2287篇 |
原子能技术 | 34篇 |
自动化技术 | 314篇 |
出版年
2022年 | 20篇 |
2021年 | 43篇 |
2020年 | 24篇 |
2019年 | 23篇 |
2018年 | 50篇 |
2017年 | 32篇 |
2016年 | 53篇 |
2015年 | 41篇 |
2014年 | 51篇 |
2013年 | 194篇 |
2012年 | 98篇 |
2011年 | 140篇 |
2010年 | 104篇 |
2009年 | 110篇 |
2008年 | 146篇 |
2007年 | 148篇 |
2006年 | 109篇 |
2005年 | 107篇 |
2004年 | 78篇 |
2003年 | 98篇 |
2002年 | 83篇 |
2001年 | 71篇 |
2000年 | 83篇 |
1999年 | 112篇 |
1998年 | 562篇 |
1997年 | 347篇 |
1996年 | 247篇 |
1995年 | 120篇 |
1994年 | 137篇 |
1993年 | 145篇 |
1992年 | 44篇 |
1991年 | 48篇 |
1990年 | 61篇 |
1989年 | 66篇 |
1988年 | 57篇 |
1987年 | 64篇 |
1986年 | 61篇 |
1985年 | 65篇 |
1984年 | 56篇 |
1983年 | 41篇 |
1982年 | 35篇 |
1981年 | 38篇 |
1980年 | 46篇 |
1979年 | 25篇 |
1978年 | 42篇 |
1977年 | 89篇 |
1976年 | 125篇 |
1975年 | 31篇 |
1974年 | 23篇 |
1969年 | 19篇 |
排序方式: 共有4757条查询结果,搜索用时 15 毫秒
1.
2.
3.
JM Rumsey BC Donohue DR Brady K Nace JN Giedd P Andreason 《Canadian Metallurgical Quarterly》1997,54(12):1481-1489
The influence of ionic strength and composition on the binding and inhibition of human leukocyte elastase by glycosaminoglycans with variable degree and position of sulfation was investigated. The kinetic mechanism of inhibition had a hyperbolic, mixed-type character with a competitive component that was promoted by low ionic strength, reduced by phosphate ions, and which also depended on the substrate and glycosaminoglycan structure. Enzyme binding was a cooperative phenomenon that varied with ionic strength and composition. The inhibition patterns correlated with the cationic character of elastase and with the distribution of arginines on its molecular surface, most notably with residues located in the vicinity of the substrate binding region. The order of affinity for elastase binding was chondroitin 4-sulfate < chondroitin 6-sulfate < dermatan sulfate, iduronate-containing derivatives being superior with respect to the glucuronate-containing counterparts. Additional sulfation at both the 4- and 6- positions or at the N- and 4-positions of the N-acetylgalactosamine moiety decidedly improved the inhibitory efficiency. The results highlight a fundamental physiological role of enzyme-glycosaminoglycan interactions. In the azurophil granule of the human polymorphonuclear neutrophil, elastase and other enzymes are bound to a matrix of chondroitin 4-sulfate because this is the only glycosaminoglycan that simultaneously offers good binding for enzyme compartmentalization together with prompt release from the bound state at the onset of phagocytosis. 相似文献
4.
5.
6.
7.
A program called GELYMAC takes data on the distances migrated by DNA fragments in a one-dimensional electrophoretic gel and, using a cubic-spline best-fit of marker fragment distance migrated versus molecular size, calculates the molecular sizes of the fragments. Written in the Rascal (Real-time Pascal) programming language, the program runs on the Macintosh family of microcomputers. Rapid entry of marker and experimental fragment migration data is afforded using a scroll bar system adjacent to a graphic representation of a gel. Output includes tabular listing of the data, graphic cartoons of the gel, and the fragment locations and molecular sizes for individual gel lanes, and the calibration curve used in data computations. 相似文献
8.
9.
It is well recognized that performance changes over time. However, the effect of these changes on overall assessments of performance is largely unknown. In a laboratory experiment, we examined the influence of salient Gestalt characteristics of a dynamic performance profile on supervisory ratings. We manipulated performance trend (flat, linear-improving, linear-deteriorating, U-shaped, and ∩-shaped), performance variation (small, large), and performance mean (negative, zero, positive) within subjects and display format (graphic, tabular) between subjects. Participants received and evaluated information about the weekly performance of different employees over a simulated 26-week period. Results showed strong main effects on performance ratings of both performance mean and performance trend, as well as interactions with display format. Theoretical and practical implications of the results are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.
In developing an intelligent mobile construction robot, a navigation system that can provide an effective and efficient path-planning algorithm is a very important element. The purpose of a path-planning method for a mobile construction robot is to find a continuous collision-free path from the initial position of the construction robot to its target position. This paper presents an improved Bug-based algorithm, called SensBug, which can produce an effective path in an unknown environment with both stationary and movable obstacles. The contributions, which make it possible to generate an effective and short path, are an improved method to select local directions, a reverse mode, and a simple leaving condition. Some emerging technologies that can be used for implementing an intelligent construction robot are introduced in this paper. 相似文献