全文获取类型
收费全文 | 15820篇 |
免费 | 719篇 |
国内免费 | 27篇 |
专业分类
电工技术 | 153篇 |
综合类 | 9篇 |
化学工业 | 3166篇 |
金属工艺 | 273篇 |
机械仪表 | 329篇 |
建筑科学 | 999篇 |
矿业工程 | 34篇 |
能源动力 | 527篇 |
轻工业 | 1486篇 |
水利工程 | 213篇 |
石油天然气 | 71篇 |
无线电 | 1130篇 |
一般工业技术 | 3070篇 |
冶金工业 | 2277篇 |
原子能技术 | 82篇 |
自动化技术 | 2747篇 |
出版年
2023年 | 97篇 |
2022年 | 166篇 |
2021年 | 311篇 |
2020年 | 264篇 |
2019年 | 301篇 |
2018年 | 341篇 |
2017年 | 355篇 |
2016年 | 369篇 |
2015年 | 357篇 |
2014年 | 515篇 |
2013年 | 1064篇 |
2012年 | 880篇 |
2011年 | 1189篇 |
2010年 | 782篇 |
2009年 | 798篇 |
2008年 | 1016篇 |
2007年 | 864篇 |
2006年 | 722篇 |
2005年 | 688篇 |
2004年 | 573篇 |
2003年 | 528篇 |
2002年 | 486篇 |
2001年 | 261篇 |
2000年 | 243篇 |
1999年 | 243篇 |
1998年 | 252篇 |
1997年 | 237篇 |
1996年 | 244篇 |
1995年 | 198篇 |
1994年 | 173篇 |
1993年 | 163篇 |
1992年 | 142篇 |
1991年 | 108篇 |
1990年 | 133篇 |
1989年 | 134篇 |
1988年 | 77篇 |
1987年 | 110篇 |
1986年 | 99篇 |
1985年 | 119篇 |
1984年 | 112篇 |
1983年 | 124篇 |
1982年 | 92篇 |
1981年 | 88篇 |
1980年 | 66篇 |
1979年 | 76篇 |
1978年 | 61篇 |
1977年 | 50篇 |
1976年 | 45篇 |
1975年 | 50篇 |
1974年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 828 毫秒
81.
Marcela Brugnach Andrew Tagg Florian Keil Wim J. de Lange 《Water Resources Management》2007,21(7):1075-1090
The use of computer models offers a general and flexible framework that can help to deal with some of the complexities and
difficulties associated with the development of water management plans as prescribed by the Water Framework Directive. However,
despite the advantages modelling presents, the integration of information derived from models into policy is far away from
being trivial or the norm. Part of the difficulties of this integration is rooted in the lack of confidence policy makers
have on the incorporation of modelling information into policy formulation. In this paper we examine the reasons for this
apparent lack of confidence and explore how some tools, presently in use, address this problem. We conclude that public confidence
in models is highly dependent on the way uncertainties are addressed and suggest possible directions of action to improve
the current situation. Four real case studies illustrate how computer models have been used in The Netherlands for carrying
out management plans at regional and national scale. We suggest that the solution to integrate modelling information into
policy formulation lies on both the modelling and the policy-making communities. 相似文献
82.
Self-help cessation programs for smokeless tobacco users: long-term follow-up of a randomized trial.
Hebert H Severson Judy A Andrews Edward Lichtenstein Brian G Danaher Laura Akers 《Nicotine & tobacco research》2007,9(2):281-289
This paper presents long-term outcomes of the largest clinical trial of smokeless tobacco (SLT) cessation reported to date. SLT users in five northwestern states were recruited to call a toll-free number, and 1,069 users were randomized to one of two self-help conditions: either a manual-only condition or an assisted self-help condition, which included the manual, a targeted video, and two support phone calls. Significant between-group differences were not found for either the 12- or 18-month point-prevalence measure of abstinence from either SLT only or all tobacco products using outcomes based on either the responder or intention-to-treat outcomes. However, using a repeated point-prevalence measure across all three assessment points, we found that significantly more assisted self-help participants reported abstinence, compared with manual-only participants. Compared with manual-only participants, those in the assisted self-help condition were significantly more likely to use recommended cessation techniques. Results demonstrate that low-cost, minimal interventions delivered by mail and phone can help a sizable proportion of individuals quit using SLT. 相似文献
83.
Cara L Booker Jennifer B Unger Stanley P Azen Lourdes Baezconde-Garbanati Brian Lickel C Anderson Johnson 《Nicotine & tobacco research》2007,9(11):1085-1094
The associations between stressful life events and smoking have been established among adolescents in the United States. However, whether these relationships are similar in adolescents from other non-Western cultures is unknown. Understanding these relationships in adolescents may help to provide opportunities to reduce the smoking rates in those cultures by providing positive coping methods that do not include smoking. In this longitudinal study, the associations between nine stressful life events scales and smoking behaviors were examined in a sample of Chinese adolescents. Six of these scales, positive school-related, negative school-related, positive family-related, positive peer-related, negative peer-related, and negative health-related had significantly different means among females and males. Among males, positive school-related stress was a protective factor for smoking susceptibility. Among females, positive school-related stress was a protective factor and negative school-related stress was a risk factor for lifetime smoking, and negative family-related stress was a risk factor for smoking susceptibility. Findings indicate that smoking among male adolescents in China may not be the result of stress; however, in females stress may contribute to the decision to smoke. Future directions are discussed. 相似文献
84.
85.
Rainwater collection as a possible water source in developing countries is introduced. The major parameters in calculating the size of the tank are defined. Six methods that have been used previously to relate demand, storage, reliability and the rainfall pattern are compared to the Ottawa Model over a wide range of demands. 相似文献
86.
An introduction to parallel process interventions is provided by a comprehensive review of the theoretical constructs and empirical studies regarding the use of the parallel process in supervision. Although more direct investigations of the parallel process are needed, we conclude that parallel process interventions within the supervisory relationship can be extremely potent and impactful. Recommendations for the facilitative application of the parallel process in the supervision and training of professional psychologists, as well as case examples, are provided. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
87.
Preliminary Development of a Model and Measure of Computer-Mediated Communication (CMC) Competence 总被引:1,自引:0,他引:1
Brian H. Spitzberg 《Journal of Computer-Mediated Communication》2006,11(2):629-666
The rationale for developing a theoretical model of computer-mediated communication (CMC) competence is established through review of social trends in the use of new media technologies. Special attention is paid to the role new media play in the formation and development of personal relationships. A model of CMC competence is then developed along the lines of motivation, knowledge, skills, context, and outcomes as a metaphorical typology for organizing existing CMC research. This research is reviewed as it informs, and is organized by, the model of CMC competence. A sampling of formal propositions resulting from the model is elaborated, and the results of preliminary pilot studies of the model are reviewed. The model is offered as a first step in examining individual differences in the domain of CMC relationships and media choice. 相似文献
88.
A specific radioimmunoassay for platelet-activating factor (PAF) sensitive in the range 10–1000 pg (0.02–2 pmoles) has been
developed. Detailed quantitative hapten inhibition studies showed specificity for the acetyl group at C-2 of PAF, a requirement
for the ether linkage at C-1 and some tolerance for substituents on the choline nitrogen. No significant cross-reactivity
was found with phosphatidylcholine and lysophosphatidylcholine or with lysoPAF.
Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl
Ether Lipids, Tokyo, Japan, May 1989. 相似文献
89.
90.
The group scanning model of feature integration theory suggests that Ss search visual displays serially by groups, but process items within each group in parallel. Group size is determined by the discriminability of the targets in the background of distractors. When the target is poorly discriminable, the size of the scanned group will be small, and search will be slow. The model predicts that group size will be smallest when targets of an intermediate value on a perceptual dimension are presented in a heterogeneous background of distractors that have higher and lower values on the same dimension. Experiment 1 (30 Ss) demonstrates this effect; Exp 2 (12 Ss) controls for a possible confound of decision complexity in Exp 1. For simple feature targets, the group scanning model provides a good account of the visual search process. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献