全文获取类型
收费全文 | 5342篇 |
免费 | 228篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 70篇 |
综合类 | 5篇 |
化学工业 | 914篇 |
金属工艺 | 96篇 |
机械仪表 | 95篇 |
建筑科学 | 178篇 |
矿业工程 | 26篇 |
能源动力 | 128篇 |
轻工业 | 678篇 |
水利工程 | 36篇 |
石油天然气 | 19篇 |
无线电 | 408篇 |
一般工业技术 | 862篇 |
冶金工业 | 1504篇 |
原子能技术 | 37篇 |
自动化技术 | 517篇 |
出版年
2022年 | 55篇 |
2021年 | 83篇 |
2020年 | 51篇 |
2019年 | 84篇 |
2018年 | 113篇 |
2017年 | 110篇 |
2016年 | 119篇 |
2015年 | 90篇 |
2014年 | 115篇 |
2013年 | 307篇 |
2012年 | 212篇 |
2011年 | 234篇 |
2010年 | 191篇 |
2009年 | 203篇 |
2008年 | 234篇 |
2007年 | 220篇 |
2006年 | 176篇 |
2005年 | 152篇 |
2004年 | 125篇 |
2003年 | 143篇 |
2002年 | 127篇 |
2001年 | 105篇 |
2000年 | 123篇 |
1999年 | 116篇 |
1998年 | 349篇 |
1997年 | 238篇 |
1996年 | 158篇 |
1995年 | 104篇 |
1994年 | 100篇 |
1993年 | 102篇 |
1992年 | 42篇 |
1991年 | 31篇 |
1990年 | 58篇 |
1989年 | 50篇 |
1988年 | 35篇 |
1987年 | 59篇 |
1986年 | 46篇 |
1985年 | 59篇 |
1984年 | 60篇 |
1983年 | 42篇 |
1982年 | 35篇 |
1981年 | 33篇 |
1980年 | 38篇 |
1979年 | 27篇 |
1978年 | 43篇 |
1977年 | 65篇 |
1976年 | 87篇 |
1975年 | 28篇 |
1974年 | 23篇 |
1969年 | 20篇 |
排序方式: 共有5573条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
5.
KJ Shon M Grilley R Jacobsen GE Cartier C Hopkins WR Gray M Watkins DR Hillyard J Rivier J Torres D Yoshikami BM Olivera 《Canadian Metallurgical Quarterly》1997,36(31):9581-9587
A paralytic peptide, psi-conotoxin Piiie has been purified and characterized from Conus purpurascens venom. Electrophysiological studies indicate that the peptide inhibits the nicotinic acetylcholine receptor (nAChR). However, the peptide does not block the binding of alpha-bungarotoxin, a competitive nAChR antagonist. Thus, psi-conotoxin Piiie appears to inhibit the receptor at a site other than the acetylcholine-binding site. As ascertained by sequence analysis, mass spectrometry, and chemical synthesis, the peptide has the following covalent structure: HOOCCLYGKCRRYOGCSSASCCQR* (O = 4-trans hydroxyproline; * indicates an amidated C-terminus). The disulfide connectivity of the toxin is unrelated to the alpha- or the alphaA-conotoxins, the Conus peptide families that are competitive inhibitors of the nAChR, but shows homology to the mu-conotoxins (which are Na+ channel blockers). 相似文献
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.
In finite-difference micromagnetic simulations, the electric field originated from time variations of magnetic induction is evaluated by means of a discrete version of Faraday's law. The electric field can be then calculated as the convolution of a tensor and the time derivative of the magnetic induction. This paper presents an analytical expression for the tensor. The paper also reports on a quantitative test of the tensor that simulates the electric field of an oscillating magnetic point dipole. 相似文献
10.
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