全文获取类型
收费全文 | 6831篇 |
免费 | 300篇 |
国内免费 | 223篇 |
专业分类
电工技术 | 226篇 |
技术理论 | 1篇 |
综合类 | 476篇 |
化学工业 | 801篇 |
金属工艺 | 68篇 |
机械仪表 | 121篇 |
建筑科学 | 1320篇 |
矿业工程 | 362篇 |
能源动力 | 397篇 |
轻工业 | 385篇 |
水利工程 | 718篇 |
石油天然气 | 107篇 |
武器工业 | 11篇 |
无线电 | 190篇 |
一般工业技术 | 260篇 |
冶金工业 | 818篇 |
原子能技术 | 12篇 |
自动化技术 | 1081篇 |
出版年
2024年 | 12篇 |
2023年 | 55篇 |
2022年 | 99篇 |
2021年 | 140篇 |
2020年 | 174篇 |
2019年 | 130篇 |
2018年 | 121篇 |
2017年 | 156篇 |
2016年 | 231篇 |
2015年 | 224篇 |
2014年 | 362篇 |
2013年 | 401篇 |
2012年 | 413篇 |
2011年 | 554篇 |
2010年 | 433篇 |
2009年 | 446篇 |
2008年 | 423篇 |
2007年 | 492篇 |
2006年 | 422篇 |
2005年 | 344篇 |
2004年 | 321篇 |
2003年 | 281篇 |
2002年 | 235篇 |
2001年 | 183篇 |
2000年 | 124篇 |
1999年 | 106篇 |
1998年 | 74篇 |
1997年 | 62篇 |
1996年 | 53篇 |
1995年 | 43篇 |
1994年 | 38篇 |
1993年 | 24篇 |
1992年 | 28篇 |
1991年 | 17篇 |
1990年 | 27篇 |
1989年 | 12篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 10篇 |
1985年 | 13篇 |
1984年 | 7篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1964年 | 3篇 |
1961年 | 2篇 |
排序方式: 共有7354条查询结果,搜索用时 0 毫秒
1.
Martins Silvia S.; Mazzotti Guido; Chilcoat Howard D. 《Canadian Metallurgical Quarterly》2006,14(3):275
Background: Despite increases in ecstasy (MDMA) use in the United States, little is known about characteristics linked with recent-onset ecstasy use, especially psychiatric symptoms and deviant behaviors. Aims: To test whether individuals with high levels of other drug use are more likely to be recent-onset ecstasy users; to test whether psychiatric symptoms in adults are associated with recent-onset ecstasy use; to explore the association between recent-onset ecstasy use and concomitant deviant behaviors in adolescents and adults. Methods: Data from the 2001 National Survey on Drug Use and Health. Findings: Recent-onset ecstasy use was significantly more likely to occur among adolescents and adults (18-34 years old) who engaged in deviant behaviors during the past year as compared with those who did not engage in deviant behaviors during the past year. Higher levels of deviancy indicated a higher likelihood of being a recent-onset ecstasy user, and associations were strongest with nonviolent deviant behaviors such as selling illegal drugs and stealing. Associations between deviant behaviors and recent-onset ecstasy use were similar in strength to associations between deviant behaviors and recent-onset cocaine and marijuana use, respectively. Adults who had past-year psychiatric symptoms (both depressive and panic symptoms) were twice as likely to be recent-onset ecstasy users as compared with those without past-year psychiatric symptoms. Greater levels of drug involvement increased the odds of being a recent-onset ecstasy user. Conclusion: Recent-onset ecstasy use seems to be associated with a range of other behavioral problems and may reflect one aspect of a larger problem behavior syndrome. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
2.
乡镇供水作为水利开发建设中的一个新领域,设计工作是龙头,有许多技术问题需要研究和探索,阐述了乡镇供水工程设计应注意的若干问题,并对设计中存在的一些具体问题进行了分析和探讨。 相似文献
3.
几种重要的有机氯系阻燃剂 总被引:2,自引:0,他引:2
介绍了氯化石蜡、氯化聚乙烯、四氯邻苯二甲酸酐、四氯双酚A、六氯环戊二烯 及由六氯环戊二烯衍生的几种氯系阻燃剂的生产过程和用途。 相似文献
4.
美国21世纪前期的军事战略重点将是争夺外空优势,夺取制天权和制信息权。分析了美国夺取外空优势的原因,及其为夺取外空优势在国家政策、航天发展和技术准备等方面采取的措施。 相似文献
5.
6.
关于化粪池几个问题的探讨 总被引:1,自引:0,他引:1
探讨化粪池在设计布置及使用管理中应注意的几个问题,以充分发挥化粪池在保护环境,减轻污染方面的作用。 相似文献
7.
8.
Kahler Christopher W.; Read Jennifer P.; Wood Mark D.; Palfai Tibor P. 《Canadian Metallurgical Quarterly》2003,17(3):226
Structural equation modeling was used to test the mediational role of social environmental selection on alcohol use in cross-sectional samples of 447 students from a rural state university and 421 students from an urban private university. Results showed that male gender, White ethnicity, and sensation seeking were uniquely associated with greater alcohol use. Mediational analyses indicated that socioenvironmental factors (i.e., Greek involvement, friends' approval of drinking/getting drunk) were positively associated with alcohol use and significantly accounted for parts of the effects of ethnicity and sensation seeking, but not gender, on alcohol use. Results suggest that White students and those high on sensation seeking may drink more heavily in college, in part because they select social environments in which alcohol use is encouraged. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
9.
Lash Steven J.; Stephens Robert S.; Burden Jennifer L.; Grambow Steven C.; DeMarce Josephine M.; Jones Mark E.; Lozano Brian E.; Jeffreys Amy S.; Fearer Stephanie A.; Horner Ronnie D. 《Canadian Metallurgical Quarterly》2007,21(3):387
Although continuing care is strongly related to positive treatment outcomes for substance use disorder (SUD), participation rates are low and few effective interventions are available. In a randomized clinical trial with 150 participants (97% men), 75 graduates of a residential Veterans Affairs Medical Center SUD program who received an aftercare contract, attendance prompts, and reinforcers (CPR) were compared to 75 graduates who received standard treatment (STX). Among CPR participants, 55% completed at least 3 months of aftercare, compared to 36% in STX. Similarly, CPR participants remained in treatment longer than those in STX (5.5 vs. 4.4 months). Additionally, CPR participants were more likely to be abstinent compared to STX (57% vs. 37%) after 1 year. The CPR intervention offers a practical means to improve adherence among individuals in SUD treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.
In this article, linear programming and fuzzy optimization models are developed for planning and management of available land-water-crop system of Mahanadi-Kathajodi delta in eastern India. The models are used to optimize the economic return, production and labour utilization, and to search the related cropping patterns and intensities with specified land, water, fertilizer and labour availability, and water use pattern constraints. Due to extreme backwardness of the study area, it has been decided to keep all the three objectives of the linear programming models at the same priority level to obtain the compromised solution in a fuzzy environment that incorporates the imprecision in fuzzy goals and fuzzy constraints. These non-structural models facilitate the conjunctive use of available surface water and groundwater resources. A comparative evaluation along with the benefit-cost ratios of the existing and proposed farming systems is also presented. 相似文献