全文获取类型
收费全文 | 101825篇 |
免费 | 1792篇 |
国内免费 | 548篇 |
专业分类
电工技术 | 1080篇 |
综合类 | 2347篇 |
化学工业 | 15613篇 |
金属工艺 | 5311篇 |
机械仪表 | 3622篇 |
建筑科学 | 2522篇 |
矿业工程 | 598篇 |
能源动力 | 2508篇 |
轻工业 | 4755篇 |
水利工程 | 1387篇 |
石油天然气 | 429篇 |
武器工业 | 1篇 |
无线电 | 11430篇 |
一般工业技术 | 20305篇 |
冶金工业 | 3988篇 |
原子能技术 | 423篇 |
自动化技术 | 27846篇 |
出版年
2024年 | 105篇 |
2023年 | 454篇 |
2022年 | 1036篇 |
2021年 | 1210篇 |
2020年 | 941篇 |
2019年 | 983篇 |
2018年 | 15296篇 |
2017年 | 14054篇 |
2016年 | 10727篇 |
2015年 | 1211篇 |
2014年 | 1084篇 |
2013年 | 1742篇 |
2012年 | 4017篇 |
2011年 | 10344篇 |
2010年 | 9017篇 |
2009年 | 6294篇 |
2008年 | 7433篇 |
2007年 | 8276篇 |
2006年 | 585篇 |
2005年 | 1555篇 |
2004年 | 1393篇 |
2003年 | 1399篇 |
2002年 | 726篇 |
2001年 | 281篇 |
2000年 | 354篇 |
1999年 | 227篇 |
1998年 | 355篇 |
1997年 | 278篇 |
1996年 | 271篇 |
1995年 | 183篇 |
1994年 | 172篇 |
1993年 | 168篇 |
1992年 | 119篇 |
1991年 | 154篇 |
1990年 | 104篇 |
1989年 | 101篇 |
1988年 | 96篇 |
1987年 | 90篇 |
1986年 | 81篇 |
1985年 | 95篇 |
1984年 | 78篇 |
1983年 | 77篇 |
1982年 | 64篇 |
1981年 | 76篇 |
1980年 | 52篇 |
1968年 | 47篇 |
1966年 | 43篇 |
1965年 | 46篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
G. Murali Dhar B. N. Srinivas M. S. Rana Manoj Kumar S. K. Maity 《Catalysis Today》2003,86(1-4):45-60
Support effects form important aspect of hydrodesulfurization (HDS) studies and mixed oxide supports received maximum attention in the last two decades. This review will focus attention on studies on mixed oxide supported Mo and W catalysts. For convenience of discussion, these are divided into Al2O3 containing mixed oxide supports, TiO2 containing mixed oxide supports, ZrO2 containing mixed oxide supports and other mixed oxide supports containing all the rest. TiO2 containing mixed oxides received maximum attention, especially TiO2–Al2O3 supported catalysts. A brief discussion about their prospects for application to ultradeep desulfurization is also included. An overview of the available literature with emphasis on research carried out in our laboratory form the contents of this publication. 相似文献
3.
The purpose of this paper is to evaluate two methods of assessing the productivity and quality impact of Computer Aided Software Engineering (CASE) and Fourth Generation Language (4GL) technologies: (1) by the retrospective method; and (2) the cross-sectional method. Both methods involve the use of questionnaire surveys. Developers' perceptions depend on the context in which they are expressed and this includes expectations about the effectiveness of a given software product. Consequently, it is generally not reliable to base inferences about the relative merits of CASE and 4GLs on a cross-sectional comparison of two separate samples of users. The retrospective method that requires each respondent to directly compare different products is shown to be more reliable. However, there may be scope to employ cross-sectional comparisons of the findings from different samples where both sets of respondents use the same reference point for their judgements, and where numerical rather than verbal rating scales are used to measure perceptions. 相似文献
4.
Jan van Eijck 《Formal Aspects of Computing》1994,6(1):766-787
Presuppositions of utterances are the pieces of information you convey with an utterance no matter whether your utterance is true or not. We first study presupposition in a very simple framework of updating propositional information, with examples of how presuppositions of complex propositional updates can be calculated. Next we move on to presuppositions and quantification, in the context of a dynamic version of predicate logic, suitably modified to allow for presupposition failure. In both the propositional and the quantificational case, presupposition failure can be viewed as error abortion of procedures. Thus, a dynamic assertion logic which describes the preconditions for error abortion is the suitable tool for analysing presupposition. 相似文献
5.
6.
We present new methods for load balancing of unstructured tree computations on large-scale SIMD machines, and analyze the scalability of these and other existing schemes. An efficient formulation of tree search on an SIMD machine consists of two major components: a triggering mechanism, which determines when the search space redistribution must occur to balance the search space over processors, and a scheme to redistribute the search space. We have devised a new redistribution mechanism and a new triggering mechanism. Either of these can be used in conjunction with triggering and redistribution mechanisms developed by other researchers. We analyze the scalability of these mechanisms and verify the results experimentally. The analysis and experiments show that our new load-balancing methods are highly scalable on SIMD architectures. Their scalability is shown to he no worse than that of the best load-balancing schemes on MIMD architectures. We verify our theoretical results by implementing the 15-puzzle problem on a CM-2 SIMD parallel computer 相似文献
7.
8.
9.
J-M Choe 《欧洲信息系统杂志》2002,11(2):142-158
This study empirically examined the organisational learning effects of the nonfinancial performance information provided by management accounting information systems (MAISs) under advanced manufacturing technology (AMT). In this study, a target costing system and the frequent and quick reporting of information were considered the facilitators of learning. First, we examined the relationships between AMT level and the amount of nonfinancial performance information produced by MAISs. The empirical results showed that there are significant positive relationships between the level of AMT and nonfinancial performance information. With a systems approach, we also proved the impact of the relationships among AMT levels, nonfinancial performance information and learning facilitators on the organisational performance of a firm. The results of our research suggest that under a high level of AMT, for the provision of information to result in an increase of performance through organisational learning, a target costing system must be introduced and a large amount of information should be provided frequently and quickly. The results of this study also showed that although AMT level may be low, fairly well-arranged facilitators and a moderately large amount of information may be necessary for the improvement of performance. In conclusion, effective organisational learning depends on the provision of relevant information as well as efficient learning support mechanisms. 相似文献
10.