全文获取类型
收费全文 | 7226篇 |
免费 | 524篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 92篇 |
综合类 | 7篇 |
化学工业 | 2089篇 |
金属工艺 | 122篇 |
机械仪表 | 142篇 |
建筑科学 | 310篇 |
矿业工程 | 16篇 |
能源动力 | 195篇 |
轻工业 | 720篇 |
水利工程 | 50篇 |
石油天然气 | 19篇 |
无线电 | 783篇 |
一般工业技术 | 1274篇 |
冶金工业 | 932篇 |
原子能技术 | 66篇 |
自动化技术 | 944篇 |
出版年
2022年 | 76篇 |
2021年 | 106篇 |
2020年 | 78篇 |
2019年 | 127篇 |
2018年 | 159篇 |
2017年 | 172篇 |
2016年 | 209篇 |
2015年 | 161篇 |
2014年 | 264篇 |
2013年 | 438篇 |
2012年 | 312篇 |
2011年 | 378篇 |
2010年 | 313篇 |
2009年 | 334篇 |
2008年 | 359篇 |
2007年 | 292篇 |
2006年 | 284篇 |
2005年 | 232篇 |
2004年 | 222篇 |
2003年 | 203篇 |
2002年 | 215篇 |
2001年 | 152篇 |
2000年 | 156篇 |
1999年 | 127篇 |
1998年 | 199篇 |
1997年 | 166篇 |
1996年 | 157篇 |
1995年 | 119篇 |
1994年 | 115篇 |
1993年 | 106篇 |
1992年 | 83篇 |
1991年 | 82篇 |
1990年 | 92篇 |
1989年 | 85篇 |
1988年 | 62篇 |
1987年 | 71篇 |
1986年 | 60篇 |
1985年 | 87篇 |
1984年 | 83篇 |
1983年 | 61篇 |
1982年 | 68篇 |
1981年 | 57篇 |
1980年 | 54篇 |
1979年 | 74篇 |
1978年 | 44篇 |
1977年 | 67篇 |
1976年 | 57篇 |
1975年 | 48篇 |
1974年 | 37篇 |
1973年 | 45篇 |
排序方式: 共有7761条查询结果,搜索用时 218 毫秒
71.
72.
Steven S Fu Miles McFall Andrew J Saxon Jean C Beckham Timothy P Carmody Dewleen G Baker Anne M Joseph 《Nicotine & tobacco research》2007,9(11):1071-1084
We conducted a systematic review of what is known about the relationship between post-traumatic stress disorder (PTSD) and smoking to guide research on underlying mechanisms and to facilitate the development of evidence-based tobacco treatments for this population of smokers. We searched Medline, PsychINFO, and the Cochrane Central Register of Controlled Trials and identified 45 studies for review that presented primary data on PTSD and smoking. Smoking rates were high among clinical samples with PTSD (40%-86%) as well as nonclinical populations with PTSD (34%-61%). Most studies showed a positive relationship between PTSD and smoking and nicotine dependence, with odds ratios ranging between 2.04 and 4.52. Findings also suggest that PTSD, rather than trauma exposure itself, is more influential for increasing risk of smoking. A small but growing literature has examined psychological factors related to smoking initiation and maintenance and the overlapping neurobiology of PTSD and nicotine dependence. Observational studies indicate that smokers with PTSD have lower quit rates than do smokers without PTSD. Yet a few tobacco cessation treatment trials in smokers with PTSD have achieved quit rates comparable with controlled trials of smokers without mental disorders. In conclusion, the evidence points to a causal relationship between PTSD and smoking that may be bidirectional. Specific PTSD symptoms may contribute to smoking and disrupt cessation attempts. Intervention studies that test behavioral and pharmacological interventions designed specifically for use in patients with PTSD are needed to reduce morbidity and mortality in this population. 相似文献
73.
74.
Merahi Ali Ahmed B. Mohammed F. Jean M. 《AEUE-International Journal of Electronics and Communications》2005,59(6):359-361
A refined study of multi-carrier code division multiple access transmission over a Nakagami fading channel is proposed. The channel power is modeled with an exponential power profile rather than the uniform profile prevalent in other papers. An expression for the bit error rate (BER) is then derived. Numerical results show that MC-CDMA performances depend on the power dispersion of interferers around the desired user power. 相似文献
75.
76.
77.
Allen John J.; Chapman Loren J.; Chapman Jean P.; Vuchetich John P.; Frost Laurie A. 《Canadian Metallurgical Quarterly》1987,96(2):83
Correlates of psychotic and psychoticlike symptoms were examined in 60 college students who scored deviantly high on the Perceptual Aberration Scale. High scorers on this scale who also scored high on both the Impulsive Nonconformity Scale and the Depression subscale of the General Behavior Inventory (GBI) showed the most deviant psychotic and psychoticlike symptoms. Moreover, performance on a task of referential communication, the Password Task, was significantly related to such symptoms. The Perceptual Aberration Scale, the Impulsive Nonconformity Scale, and the GBI Depression subscale are recommended for concurrent use in mass screening to select individuals likely to exhibit psychotic or psychoticlike symptoms. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
78.
Castagna Claudia; Absil Philippe; Foidart Agnès; Balthazart Jacques 《Canadian Metallurgical Quarterly》1998,112(1):233
The authors investigated the behavioral actions of vasotocin (VT) in castrated testosterone-treated male Japanese quail. The appetitive and consummatory components of sexual behavior as well as the occurrence frequency of crows were inhibited, in a dose-dependent manner, by injections of VT. The authors observed opposite effects after injection of the V1 receptor antagonist, dPTyr(Me)AVP. Lower doses of VT were more active after central than after systemic injection, and effects of systemic injections of VT were blocked by a central injection of dPTyr(Me)AVP. The behavioral inhibition was associated with a modified diuresis after systemic but not central injection. These results provide direct evidence that VT affects male sexual behavior in quail by a direct action on the brain independent of its peripheral action on diuresis. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
79.
Edwards Jean M.; Rudisill John R.; Champney Tim F.; Hershberger Paul J.; Polaine Vanessa H.; Archambault Denise L. 《Canadian Metallurgical Quarterly》1998,50(3):173
Outplacement firms developed in response to corporate downsizings to assist former upper-level employees in seeking reemployment. An important question for practitioners who assist clients in outplacement is how the personal characteristics that clients bring to the situation influence their success in finding a new job. The present archival study examined demographic variables, previous job history, and personality characteristics as predictors of outplacement outcomes. Outplacement duration was predicted by previous income, and new earnings were predicted by previous earnings, sex, and years with previous employer. The need for prospective, longitudinal research that examines the coping process in outplacement is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
80.
Kenia Sousa Jean Vanderdonckt Brian Henderson-Sellers Cesar Gonzalez-Perez 《Journal of Visual Languages and Computing》2012,23(4):195-212
This work aims at evaluating a graphical notation for modelling software (and other kinds of) development methodologies, thus demonstrating how useful the graphical aspects can be for sharing knowledge between the people responsible for documenting information and those responsible for understanding and putting it into practice. We acknowledge the importance of having a common set of symbols that can be used to create, use and disseminate information for a larger audience than is possible today with a variety of alternatives and lack of a common ground. Using a cognitive dimensions framework, we make a standard evaluation of the elements and diagrams of the notation proposed to support the ISO/IEC 24744 methodology metamodel standard, considering the trade-offs between different dimensions. We suggest improvements to this existing notation based on this analysis, in the context of improving communication between creators and users of methodologies. 相似文献