全文获取类型
收费全文 | 6496篇 |
免费 | 323篇 |
国内免费 | 135篇 |
专业分类
电工技术 | 117篇 |
综合类 | 724篇 |
化学工业 | 919篇 |
金属工艺 | 312篇 |
机械仪表 | 574篇 |
建筑科学 | 286篇 |
矿业工程 | 81篇 |
能源动力 | 147篇 |
轻工业 | 267篇 |
水利工程 | 57篇 |
石油天然气 | 159篇 |
武器工业 | 19篇 |
无线电 | 282篇 |
一般工业技术 | 773篇 |
冶金工业 | 1752篇 |
原子能技术 | 17篇 |
自动化技术 | 468篇 |
出版年
2025年 | 63篇 |
2024年 | 195篇 |
2023年 | 199篇 |
2022年 | 162篇 |
2021年 | 189篇 |
2020年 | 171篇 |
2019年 | 179篇 |
2018年 | 126篇 |
2017年 | 132篇 |
2016年 | 179篇 |
2015年 | 153篇 |
2014年 | 239篇 |
2013年 | 303篇 |
2012年 | 247篇 |
2011年 | 351篇 |
2010年 | 309篇 |
2009年 | 309篇 |
2008年 | 269篇 |
2007年 | 370篇 |
2006年 | 349篇 |
2005年 | 320篇 |
2004年 | 296篇 |
2003年 | 275篇 |
2002年 | 240篇 |
2001年 | 195篇 |
2000年 | 104篇 |
1999年 | 69篇 |
1998年 | 70篇 |
1997年 | 54篇 |
1996年 | 58篇 |
1995年 | 53篇 |
1994年 | 52篇 |
1993年 | 28篇 |
1992年 | 25篇 |
1991年 | 27篇 |
1990年 | 24篇 |
1989年 | 25篇 |
1988年 | 23篇 |
1987年 | 26篇 |
1986年 | 25篇 |
1984年 | 22篇 |
1965年 | 51篇 |
1964年 | 29篇 |
1962年 | 23篇 |
1961年 | 21篇 |
1959年 | 24篇 |
1957年 | 23篇 |
1956年 | 18篇 |
1955年 | 26篇 |
1954年 | 24篇 |
排序方式: 共有6954条查询结果,搜索用时 15 毫秒
1.
The compaction properties of an investigational drug are studied by the use of a compaction simulator. The effects of punch velocity over the range of 30-640 mm-1 on the compaction properties of the pure drug and a variety of formulas incorporating a high dose of the active compound have been investigated. The data were analyzed by applying the Heckel equation. The pure drug was found to have a high yield pressure at a relatively low punch velocity of 31 mm-1. As the punch velocity was increased there was a decrease in crushing strength, primarily as a result of increasing yield pressure. These findings indicate that the pure drug predominantly consolidated by fragmentation and elastic deformation, with a slow plastically deforming component. The information obtained on the consolidation mechanism of the pure drug and, subsequently, on model formulas were instrumental in the design and selection of a robust formula and granulation process. The advantages of conducting dosage form design and characterization studies during the early phase of tablet formulation using means such as a compaction simulator are emphasized in this investigation. 相似文献
2.
Concrete structures in main coal cleaning plants have been rebuilt and reinforced in the coal mines of the Shanghai Da-tun Energy Sources Co. Ltd., the first colliery of the Pingdingshan Coal Co. Ltd. and the Sanhejian mine of the Xuzhou Mining Group Co. Ltd. In these projects, the operating environment and reliability of concrete structures in the main plants of the three companies were investigated and the safety of the structures inspected. Qualitative and quantitative analyses were made on the spe-cial natural, technological and mechanical environments around the structures. On the basis of these analyses, we discuss the long-term, combined actions of the harsh natural (corrosive gases, liquids and solids) and mechanical environments on concrete structures and further investigated the damage and deteriorating mechanisms and curing techniques of concrete structures in the main coal cleaning plants. Our study can provide a theoretical basis for ensuring the reliability of concrete structures in main coal cleaning plants. 相似文献
3.
The origin of work-function changes induced in polymer/metal structures (polyacrylic acid (PAA), ammonium and sodium polyacrylate) upon ammonia exposure is studied. To understand and explain the mechanism systematic measurements of uncoated and polymer coated metals are performed in Kelvin Probe (KP) setups. Additional data have been acquired through gravimetric and electrochemical experiments (cyclic voltammetry (CV)). The results obtained confirm that the field effect sensitive processes are taking place at the metal/polymer interface and allow their modelling. The intrinsic sensitivity of metallic samples upon ammonia exposure is influenced by the presence of coating polymers, by their ability to sorb water and to keep the metal surface wet or dry. 相似文献
4.
The relationship between treatment outcome and the extent to which participants completed homework assignments was evaluated among 60 cocaine-dependent individuals assigned to cognitive-behavioral therapy (CBT). Homework was assigned in 72% of all sessions and initiated by participants in 48% of the sessions in which it was assigned. Completion of homework was unrelated to participants' baseline characteristics and several indicators of treatment compliance. Participants who completed more homework assignments demonstrated significantly greater increases in the quantity and quality of their coping skills and used significantly less cocaine during treatment and through a 1-year follow-up. These data suggest that the extent to which participants are willing to complete extrasession assignments may be an important mediator of response to CBT. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
5.
Burle Borís; Allain Sonia; Vidal Franck; Hasbroucq Thierry 《Canadian Metallurgical Quarterly》2005,31(4):831
Although it is widely accepted that control mechanisms are necessary for human behavior to be adapted, very little is known about how such mechanisms are recruited. A suggestion to fill the gap was put forward by M. M. Botvinick, T. S. Braver, C. S. Carter, D. M. Barch, and J. D. Cohen (2001), who proposed the conflict-loop theory. This theory has been successful in accounting for the reduction of compatibility effects after an incompatible trial: The level of conflict being, on average, higher during an incompatible trial, more control occurs after such a trial. The authors have tested this prediction by sorting the trials on the basis of amount of conflict (quantified by the electromyographic activity) they presented. A reduction of the compatibility effect was observed after incompatible trials, but it was independent of the level of conflict on previous trials, suggesting that the conflict does not trigger changes in executive control. Consequences for the conflict monitoring model are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
6.
Carles Sierra 《Autonomous Agents and Multi-Agent Systems》2004,9(3):285-301
Electronic commerce has been one of the traditional arenas for agent technology. The complexity of these applications has been a challenge for researchers that have developed methodologies, products, and systems, having in mind the specificities of trade, the interaction particularities of commerce, the strict notion of commitment and contract, and the clearly shaped conventions and norms that structure the field. In this paper I survey some key areas for agent technology which, although general, are of special importance in electronic commerce, namely, solid development methodologies, negotiation technologies and trust-building mechanisms. I give examples of systems in which I have directly participated, although I also try to refer to the work of other AgentLink Special Interest Group members over the last few years. 相似文献
7.
D.A. Rigney 《Tribology International》1997,30(5):361-367
The author reviews selected experimental results which have contributed to improved understanding of sliding wear processes. The emphasis is on the chemical and structural changes which occur at and near the surface of metallic materials during sliding in different environments. The importance of plastic deformation, fracture, transfer, mechanical mixing, phase transformations and oxidation is discussed. Examples of transitions are described, and interesting correlations noted. In selecting the content of this paper, the author includes controversial results and conclusions and raises questions about the development of wear equations, interpretations of the wear coefficient, the importance of adhesion, the roles of hardness, the causes of transitions and the location of debris-producing cracks. 相似文献
8.
Kraut Robert; Olson Judith; Banaji Mahzarin; Bruckman Amy; Cohen Jeffrey; Couper Mick 《Canadian Metallurgical Quarterly》2004,59(2):105
As the Internet has changed communication, commerce, and the distribution of information, so too it is changing psychological research. Psychologists can observe new or rare phenomena online and can do research on traditional psychological topics more efficiently, enabling them to expand the scale and scope of their research. Yet these opportunities entail risk both to research quality and to human subjects. Internet research is inherently no more risky than traditional observational, survey, or experimental methods. Yet the risks and safeguards against them will differ from those characterizing traditional research and will themselves change over time. This article describes some benefits and challenges of conducting psychological research via the Internet and offers recommendations to both researchers and institutional review boards for dealing with them. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
9.
Reviews the book, Evolution, culture and the human mind edited by M. Schaller, et al. (see record 2009-20004-000). This current volume, Evolution, culture and the human mind, follows the lead of Wundt where an attempt is made to provide a synthesis of theory and data across psychological subfields into a holistic framework. Norenzayan, Schaller, and Heine begin the volume with an overview of the scope and themes that arose from their 2004 conference at the University of British Columbia on “Mind, Culture and Evolution.” Explicit throughout this volume is an effort to bridge the “yawning chasm” between perspectives of evolutionary determinism and cultural constructionism. In doing so, there is interest in providing a rigorous multidisciplinary scientific effort to solve this foundational problem for psychology. As such this volume provides an interesting and insightful examination of the evolution of consciousness, cognition, decision-making, actions, and cultural norms in terms of collective consequences and genetic mechanisms. The volume is divided into three sections where several dialectical themes (theory/data, top-down/bottom-up, ecological/social, diversification/integration) are woven throughout. Overall the volume offers nice flow from one collection of essays to the next as themes are picked up and let go, only to return later on. This volume shows a dominance of natural science (cross-cultural) inclinations where some readers may call for more voice given to phenomenological and hermeneutical (cultural) human science contributions. Other critics may challenge the reliance upon correlational, comparative, and post hoc data to bolster claims of causality in support of various theoretical suppositions. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.