全文获取类型
收费全文 | 9601篇 |
免费 | 507篇 |
国内免费 | 234篇 |
专业分类
电工技术 | 503篇 |
技术理论 | 2篇 |
综合类 | 728篇 |
化学工业 | 647篇 |
金属工艺 | 260篇 |
机械仪表 | 190篇 |
建筑科学 | 2443篇 |
矿业工程 | 1442篇 |
能源动力 | 256篇 |
轻工业 | 424篇 |
水利工程 | 888篇 |
石油天然气 | 725篇 |
武器工业 | 14篇 |
无线电 | 203篇 |
一般工业技术 | 345篇 |
冶金工业 | 694篇 |
原子能技术 | 30篇 |
自动化技术 | 548篇 |
出版年
2024年 | 20篇 |
2023年 | 77篇 |
2022年 | 228篇 |
2021年 | 275篇 |
2020年 | 288篇 |
2019年 | 139篇 |
2018年 | 106篇 |
2017年 | 155篇 |
2016年 | 170篇 |
2015年 | 215篇 |
2014年 | 696篇 |
2013年 | 433篇 |
2012年 | 755篇 |
2011年 | 803篇 |
2010年 | 648篇 |
2009年 | 743篇 |
2008年 | 595篇 |
2007年 | 676篇 |
2006年 | 632篇 |
2005年 | 482篇 |
2004年 | 414篇 |
2003年 | 410篇 |
2002年 | 354篇 |
2001年 | 244篇 |
2000年 | 174篇 |
1999年 | 164篇 |
1998年 | 91篇 |
1997年 | 90篇 |
1996年 | 70篇 |
1995年 | 47篇 |
1994年 | 27篇 |
1993年 | 31篇 |
1992年 | 14篇 |
1991年 | 17篇 |
1990年 | 11篇 |
1989年 | 9篇 |
1988年 | 8篇 |
1987年 | 5篇 |
1986年 | 8篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1975年 | 1篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1970年 | 1篇 |
1954年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
含硫化氢气井钻井过程中的腐蚀因素与防护研究 总被引:1,自引:0,他引:1
在含硫气井的钻井过程中对于HRC大于22的钻具钢材除了腐蚀疲劳之外,在pH值小于9的环境中会发生硫化物应力腐蚀破裂,这种破坏比腐蚀疲劳更突然、更快,使钻杆大量损坏。含硫气井在钻井过程中,由于湿硫化氢的出现,常常会出现油管、套管、钻井设备、钻井仪器以及对支持保护管柱的水泥环柱等腐蚀和损坏问题,为此,阐述了湿硫化氢的腐蚀特点、机理,归纳总结了影响腐蚀的因素,综述了如何在这些方面防止其腐蚀,使损失减小,为指导油管、套管防腐工程实践提供了依据。建议在钻井过程中采用碱性钻井液,其pH值可到9或更高(至pH值12),以减缓或防止钻井过程中电化学从硫化物应力腐蚀破裂;含硫气井用的钻杆应该间歇使用。钻杆停用堆置时间可使其放氢,使钻杆恢复韧性,防止硫化物应力腐蚀断裂。 相似文献
2.
3.
4.
本文通过分析筼筜湖的自然概况、防汛排涝系统设施及实际运行等资料,提出进一步提高筼筜湖防汛排涝能力的对策。 相似文献
5.
Hung‐Yee Shu 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(3):273-280
Liquid–liquid two‐phase epoxidation from cyclohexene and cyclooctene in aqueous potassium peroxymonosulfate (commercially available as Oxone®) solution was studied as an application in pollution prevention. To avoid potential emissions of volatile organic compounds an aqueous solution was employed to replace the usual chlorinated solvents used in epoxide production. A droplet column reactor and stirred tank reactor were used to investigate two‐phase synthesis of epoxide. An aqueous Oxone® solution was used to oxidize a dispersion of alkene droplets and form epoxide. The study of aqueous epoxidation in both reactors showed that the epoxidation of alkenes can be represented as a first order reaction with respect to alkene. The salting out effect of Oxone® concentration was studied in both reactors and found to be very similar at optimal conditions. In comparing the two reactors, it was found that the droplet column reactor produces larger quantities of product per unit reactor volume for the same reaction time. The objective of this study is to provide an alternative reactor design and synthesis route that can meet pollution prevention goals. Copyright © 2004 Society of Chemical Industry 相似文献
6.
Lussier Isabelle; Derevensky Jeffrey L.; Gupta Rina; Bergevin Tanya; Ellenbogen Stephen 《Canadian Metallurgical Quarterly》2007,21(2):165
The study of resilient children has overturned many deficit-focused models concerning the ontogenesis of children raised in adversity. This study explored the relationship between risk and protective factors, resilience, and youth gambling behavior. More specifically, this study examined the relative contribution of various risk and protective domains in relation to problem gambling behavior and examined whether youth identified as resilient (high risk exposure- high internalized protection) were as likely as those identified as vulnerable (high risk exposure-low internalized protection) to engage in excessive gambling behavior. The sample consisted of 1,273 students ages 12 to 19. The findings demonstrated that risk and protective factors each provide a unique contribution to the prediction model of gambling problems. Resilient and vulnerable youth differed significantly in their self-reported gambling severity. As well, resilient youth were not statistically distinguishable from low-risk exposure groups in terms of their gambling severity. Findings are interpreted with respect to resilience and prevention research. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
7.
Treatment of the addictions is changing. Psychosocial treatment programs and research projects have changed the way helping professionals view, treat, and prevent drug abuse. This article reviews the contributions included in this special series; they encompass several general issues facing psychologists who conduct treatment, research, and teaching in the field of addictive behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
8.
9.
This article discusses the phenomenon of youth violence from a psychology of gender perspective. Although other factors are discussed--including gun availability, violence-related media influence, family and caretaker factors, and effects of teasing and bullying--the intention is to highlight new thinking on the potential relationship between boys' traditional masculine socialization experiences and violence. In this new perspective, traditional masculine socialization estranges and isolates many boys from their genuine inner lives and vital connections to others, which is theorized to heighten their risk of engaging in acts of violence. The authors identify school and community programs that may be helpful in counteracting damaging socialization experiences and supporting boys' healthier emotional and psychological development. Finally, the article discusses approaches that psychologists and other mental health professionals can use to help address this vital issue. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.
暖通空调工程设计常见问题 总被引:1,自引:0,他引:1
通过对施工图审查工作进行总结,指出了暖通空调和防火防排烟设计中存在的问题及防火规范本身的一些不足。 相似文献