全文获取类型
收费全文 | 21243篇 |
免费 | 557篇 |
国内免费 | 25篇 |
专业分类
电工技术 | 222篇 |
综合类 | 19篇 |
化学工业 | 4467篇 |
金属工艺 | 495篇 |
机械仪表 | 376篇 |
建筑科学 | 939篇 |
矿业工程 | 91篇 |
能源动力 | 551篇 |
轻工业 | 1417篇 |
水利工程 | 273篇 |
石油天然气 | 207篇 |
武器工业 | 1篇 |
无线电 | 1482篇 |
一般工业技术 | 3421篇 |
冶金工业 | 4546篇 |
原子能技术 | 169篇 |
自动化技术 | 3149篇 |
出版年
2022年 | 148篇 |
2021年 | 247篇 |
2020年 | 199篇 |
2019年 | 269篇 |
2018年 | 303篇 |
2017年 | 307篇 |
2016年 | 375篇 |
2015年 | 293篇 |
2014年 | 462篇 |
2013年 | 1258篇 |
2012年 | 768篇 |
2011年 | 969篇 |
2010年 | 775篇 |
2009年 | 792篇 |
2008年 | 916篇 |
2007年 | 976篇 |
2006年 | 809篇 |
2005年 | 763篇 |
2004年 | 659篇 |
2003年 | 622篇 |
2002年 | 592篇 |
2001年 | 370篇 |
2000年 | 380篇 |
1999年 | 367篇 |
1998年 | 440篇 |
1997年 | 387篇 |
1996年 | 377篇 |
1995年 | 365篇 |
1994年 | 310篇 |
1993年 | 364篇 |
1992年 | 314篇 |
1991年 | 228篇 |
1990年 | 275篇 |
1989年 | 285篇 |
1988年 | 265篇 |
1987年 | 256篇 |
1986年 | 283篇 |
1985年 | 302篇 |
1984年 | 298篇 |
1983年 | 294篇 |
1982年 | 233篇 |
1981年 | 260篇 |
1980年 | 253篇 |
1979年 | 251篇 |
1978年 | 227篇 |
1977年 | 230篇 |
1976年 | 205篇 |
1975年 | 195篇 |
1974年 | 174篇 |
1973年 | 180篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Matthew R. James 《国际强度与非线性控制杂志
》1994,4(6):791-806
》1994,4(6):791-806
In this paper we present a numerical method for estimating the current state of a nonlinear control system. We use finite differences to discretize a modified version of the finite-time observer equations in James. The discretized equations are simple and easily programmed. The convergence and accuracy of the scheme is proved, and the scheme enjoys a number of important properties: availability of rate of convergence estimates, good robustness characteristics, and the ability to handle certain types of discontinuities in the observations. The major disadvantage is that the number of grid points required increases exponentially with the number of state dimensions. 相似文献
2.
James W. Conard 《Information Systems Management》1987,4(1):8-17
The concept of the integrated services digital network (ISDN) could revolutionize information management. The purpose of the ISDN is to provide a worldwide network that offers end-to-end digital connectivity supporting a wide variety of communications services. ISDN subscribers will have direct access to a high-speed digital pipeline capable of supporting simultaneous voice, data, facsimile, and various other services and calling features. 相似文献
3.
Action calculi, which generalise process calculi such as Petri nets, π-calculusand ambient calculus, have been presented
in terms of action graphs. We here offer linear action graphs as a primitive basis for action calculi. This paper presents the category of embeddings of undirected linear
action graphs without nesting, using a novel form of graphical reasoning which simplifies some otherwise complex manipulations
in regular algebra. The results are adapted in a few lines to directed graphs. This work is part of a long-term search for
a uniform behavioural theory for process calculi.
Received October 2000 / Accepted in revised form April 2001 相似文献
4.
Serum total cholesterol, high density lipoprotein (HDL) cholesterol, and triglyceride levels were studied in healthy male
and female subjects consuming for one-week periods a diet of conventional food (CF) providing 42% of energy as fat, principally
butter fat, and then in random order nutritionally complete, defined formula diets of moderate (32%) to very low (1%) fat
content. Compared to CF, the formula with 32% of energy as corn oil lowered serum cholesterol by 25% and the ratio of total
to HDL-cholesterol by 13%. Low (9%) and very low (1–3%) fat formulas reduced HDL-cholesterol by as much as 40%, raised the
total: HDL-cholesterol ratio by about 20% and raised serum triglyceride levels by as much as 100%. When low and very low fat
formulas were ingested for three weeks, these effects persisted although maximal responses occurred during the first week.
These results demonstrated that a moderate fat formula diet with a high P/S ratio had a more favorable effect on serum lipid
levels than various low fat formulas. Low fat conventional food diets should be studied in long-term controlled metabolic
experiments before such diets are recommended to the general population for coronary heart disease or cancer prevention. 相似文献
5.
6.
In this article, we describe a new approach to applying distributed artificial intelligence techniques to manufacturing processes. The construction of intelligent systems is one of the most important techniques among artificial intelligence research. Our goal is to develop an integrated intelligent system for real time manufacturing processes. An integrated intelligent system is a large knowledge integration environment that consists of several symbolic reasoning systems (expert systems) and numerical computation packages. These software programs are controlled by a meta-system which manages the selection, operation and communication of these programs. A meta-system can be implemented in different language environments and applied to many disciplines. This new architecture can serve as a universal configuration to develop high performance intelligent systems for many complicated industrial applications in real world domains.To whom all correspondence should be addressed. 相似文献
7.
Graduates of clinical training programs were surveyed to determine the degree to which they have found various graduate school experiences useful in their professional work. Samples of academic clinical psychologists and practicing clinical psychologists reported time allocation and preference for various professional activities, perceived usefulness of various theoretical orientations, and the influence on their current professional work of 19 different graduate training topics. Results suggest that where differences exist, academic clinical psychologists are generally more satisfied with Boulder-model-inspired scientific training than are clinical practitioners. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
8.
9.
Digant Gupta Christopher G Lis Sadie L Dahlk Jessica King Pankaj G Vashi James F Grutsch Carolyn A Lammersfeld 《Nutrition journal》2008,7(1):19
Background
Bioelectrical Impedance (BIA) derived phase angle is increasingly being used as an objective indicator of nutritional status in advanced cancer. Subjective Global Assessment (SGA) is a subjective method of nutritional status. The objective of this study was to investigate the association between BIA derived phase angle and SGA in advanced colorectal cancer. 相似文献10.