全文获取类型
收费全文 | 37933篇 |
免费 | 1001篇 |
国内免费 | 67篇 |
专业分类
电工技术 | 431篇 |
综合类 | 38篇 |
化学工业 | 7544篇 |
金属工艺 | 946篇 |
机械仪表 | 698篇 |
建筑科学 | 1976篇 |
矿业工程 | 280篇 |
能源动力 | 1084篇 |
轻工业 | 3215篇 |
水利工程 | 360篇 |
石油天然气 | 219篇 |
武器工业 | 2篇 |
无线电 | 2750篇 |
一般工业技术 | 5820篇 |
冶金工业 | 8111篇 |
原子能技术 | 363篇 |
自动化技术 | 5164篇 |
出版年
2022年 | 228篇 |
2021年 | 435篇 |
2020年 | 367篇 |
2019年 | 424篇 |
2018年 | 541篇 |
2017年 | 549篇 |
2016年 | 558篇 |
2015年 | 503篇 |
2014年 | 802篇 |
2013年 | 2383篇 |
2012年 | 1352篇 |
2011年 | 1758篇 |
2010年 | 1281篇 |
2009年 | 1406篇 |
2008年 | 1588篇 |
2007年 | 1647篇 |
2006年 | 1412篇 |
2005年 | 1294篇 |
2004年 | 1170篇 |
2003年 | 1169篇 |
2002年 | 1141篇 |
2001年 | 735篇 |
2000年 | 699篇 |
1999年 | 691篇 |
1998年 | 926篇 |
1997年 | 733篇 |
1996年 | 764篇 |
1995年 | 685篇 |
1994年 | 649篇 |
1993年 | 659篇 |
1992年 | 561篇 |
1991年 | 390篇 |
1990年 | 510篇 |
1989年 | 489篇 |
1988年 | 452篇 |
1987年 | 463篇 |
1986年 | 430篇 |
1985年 | 564篇 |
1984年 | 555篇 |
1983年 | 506篇 |
1982年 | 529篇 |
1981年 | 515篇 |
1980年 | 415篇 |
1979年 | 416篇 |
1978年 | 373篇 |
1977年 | 372篇 |
1976年 | 334篇 |
1975年 | 364篇 |
1974年 | 269篇 |
1973年 | 312篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
5.
6.
7.
John Bensted 《Cement and Concrete Composites》2003,25(8):873-877
Two main formation routes for thaumasite exist below 15 °C. One is the direct route from C–S–H reacting with appropriate carbonate, sulfate, Ca2+ ions and excess water. The other route is the woodfordite route from ettringite reacting with C–S–H, carbonate, Ca2+ ions and excess water, in which thaumasite arises through the intermediate formation of the solid solution woodfordite. The woodfordite route for thaumasite formation appears to be relatively quicker (although still slow) than the direct route, presumably because with the former the ettringite already has the octahedral [M(OH)6] units that can facilitate the critical change from [Al(OH)6]3− to [Si(OH)6]2− groupings. Both routes are mutually dependent on each other. The presence of magnesium salts can modify the path to thaumasite formation. High pressure might be able to stabilise [Si(OH)6]2− groupings and allow thaumasite to become formed above 15 °C. This possibility is discussed. 相似文献
8.
At some point in their careers, clinicians who work or consult in forensic and correctional settings will almost certainly encounter individuals who exhibit psychopathic personality features. Because of the widespread use of this disorder to inform legal and clinical decision making, psychologists should be exceedingly familiar with the relevant research literature on this topic before venturing into these settings. This article reviews the empirical bases of several clinically relevant claims and assertions regarding psychopathy and concludes that many areas of research are decidedly more equivocal in their findings than is commonly perceived. Although there is much to be gained by assessing psychopathy in various contexts, clinicians need to be cautious about drawing overzealous and empirically questionable conclusions about an important disorder that also has great potential for abuse. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
9.
Three-dimensional models, or pharmacophores, describing Euclidean constraints on the location on small molecules of functional
groups (like hydrophobic groups, hydrogen acceptors and donors, etc.), are often used in drug design to describe the medicinal
activity of potential drugs (or ‘ligands’). This medicinal activity is produced by interaction of the functional groups on
the ligand with a binding site on a target protein. In identifying structure-activity relations of this kind there are three
principal issues: (1) It is often difficult to “align” the ligands in order to identify common structural properties that
may be responsible for activity; (2) Ligands in solution can adopt different shapes (or `conformations’) arising from torsional
rotations about bonds. The 3-D molecular substructure is typically sought on one or more low-energy conformers; and (3) Pharmacophore
models must, ideally, predict medicinal activity on some quantitative scale. It has been shown that the logical representation
adopted by Inductive Logic Programming (ILP) naturally resolves many of the difficulties associated with the alignment and
multi-conformation issues. However, the predictions of models constructed by ILP have hitherto only been nominal, predicting
medicinal activity to be present or absent. In this paper, we investigate the construction of two kinds of quantitative pharmacophoric
models with ILP: (a) Models that predict the probability that a ligand is “active”; and (b) Models that predict the actual
medicinal activity of a ligand. Quantitative predictions are obtained by the utilising the following statistical procedures
as background knowledge: logistic regression and naive Bayes, for probability prediction; linear and kernel regression, for
activity prediction. The multi-conformation issue and, more generally, the relational representation used by ILP results in
some special difficulties in the use of any statistical procedure. We present the principal issues and some solutions. Specifically,
using data on the inhibition of the protease Thermolysin, we demonstrate that it is possible for an ILP program to construct
good quantitative structure-activity models. We also comment on the relationship of this work to other recent developments
in statistical relational learning.
Editors: Tamás Horváth and Akihiro Yamamoto 相似文献
10.
Using an integrated process of data and modeling in HRA 总被引:1,自引:0,他引:1
John Wreathall Dennis Bley Emilie Roth Jordan Multer Thomas Raslear 《Reliability Engineering & System Safety》2004,83(2):221
The paper describes an approach taken to estimate the probabilities of failure associated with various railroad tasks to prevent accidents (principally collisions and derailments). These probabilities were estimated using an expert elicitation process that used partially relevant data available from a variety of databases and that were filtered and scaled to make them more directly relevant to the analyses being performed. Extensive qualitative studies were performed prior to the elicitation process to identify relevant contexts under which the tasks can be performed. 相似文献