全文获取类型
收费全文 | 9776篇 |
免费 | 1530篇 |
国内免费 | 1181篇 |
专业分类
电工技术 | 602篇 |
综合类 | 1560篇 |
化学工业 | 628篇 |
金属工艺 | 127篇 |
机械仪表 | 617篇 |
建筑科学 | 578篇 |
矿业工程 | 136篇 |
能源动力 | 134篇 |
轻工业 | 309篇 |
水利工程 | 292篇 |
石油天然气 | 255篇 |
武器工业 | 170篇 |
无线电 | 1534篇 |
一般工业技术 | 1531篇 |
冶金工业 | 318篇 |
原子能技术 | 86篇 |
自动化技术 | 3610篇 |
出版年
2024年 | 64篇 |
2023年 | 178篇 |
2022年 | 342篇 |
2021年 | 388篇 |
2020年 | 464篇 |
2019年 | 403篇 |
2018年 | 414篇 |
2017年 | 426篇 |
2016年 | 487篇 |
2015年 | 447篇 |
2014年 | 610篇 |
2013年 | 707篇 |
2012年 | 698篇 |
2011年 | 691篇 |
2010年 | 540篇 |
2009年 | 562篇 |
2008年 | 588篇 |
2007年 | 604篇 |
2006年 | 551篇 |
2005年 | 456篇 |
2004年 | 400篇 |
2003年 | 335篇 |
2002年 | 288篇 |
2001年 | 250篇 |
2000年 | 228篇 |
1999年 | 180篇 |
1998年 | 131篇 |
1997年 | 133篇 |
1996年 | 95篇 |
1995年 | 131篇 |
1994年 | 95篇 |
1993年 | 67篇 |
1992年 | 70篇 |
1991年 | 54篇 |
1990年 | 65篇 |
1989年 | 59篇 |
1988年 | 56篇 |
1987年 | 26篇 |
1986年 | 30篇 |
1985年 | 18篇 |
1984年 | 12篇 |
1983年 | 11篇 |
1982年 | 16篇 |
1981年 | 10篇 |
1980年 | 8篇 |
1977年 | 10篇 |
1965年 | 7篇 |
1964年 | 8篇 |
1961年 | 12篇 |
1959年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Greg A. Breed Paul M. Severns Andrew M. Edwards 《Journal of the Royal Society Interface》2015,12(103)
Lévy flights have gained prominence for analysis of animal movement. In a Lévy flight, step-lengths are drawn from a heavy-tailed distribution such as a power law (PL), and a large number of empirical demonstrations have been published. Others, however, have suggested that animal movement is ill fit by PL distributions or contend a state-switching process better explains apparent Lévy flight movement patterns. We used a mix of direct behavioural observations and GPS tracking to understand step-length patterns in females of two related butterflies. We initially found movement in one species (Euphydryas editha taylori) was best fit by a bounded PL, evidence of a Lévy flight, while the other (Euphydryas phaeton) was best fit by an exponential distribution. Subsequent analyses introduced additional candidate models and used behavioural observations to sort steps based on intraspecific interactions (interactions were rare in E. phaeton but common in E. e. taylori). These analyses showed a mixed-exponential is favoured over the bounded PL for E. e. taylori and that when step-lengths were sorted into states based on the influence of harassing conspecific males, both states were best fit by simple exponential distributions. The direct behavioural observations allowed us to infer the underlying behavioural mechanism is a state-switching process driven by intraspecific interactions rather than a Lévy flight. 相似文献
2.
3.
随机激光器的最新进展 总被引:5,自引:2,他引:3
综述了近年来随机激光器的最新研究结果,包括随机激光产生的机制,随机增益介质的制备方法,随机激光器的激励与发光特性和随机激光理论。最后,介绍了随机激光器的应用前景。 相似文献
4.
A review of the literature on the impact of sexual contacts between adults and boys reveals the existence of two principal outcomes: 1) some participants develop various disorders once in adulthood, such as behavioural problems, sexual disorders, or personality problems; 2) some participants do not present with any major disorders in the long run. These different outcomes may be associated with several moderating variables related to the sexual contacts, such as the level of coercion at the time of these contacts, the bond between the child and the adult, or the context of the sexual relation. However, the conclusions relating to the relations between early sexual contacts with adults and subsequent problems of adaptation in adulthood are difficult to determine. This is because of various methodological problems associated with relevant studies (i.e., definition of these contacts, nature of the sample, method evaluation, statistical analyses). In this article, we propose certain avenues of research that may help clarify this problem. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
5.
6.
This article proposes a model of the ways in which dyadic interactions between employees who occupy 1 of 4 archetypal social roles in organizations can lead to either episodic or institutionalized patterns of victimization. The model shows how the occurrence of victimization involving these 4 role types is influenced by organizational variables such as power differences, culture, and access to social capital. The model integrates behavioral and social structural antecedents of victimization to develop a relational perspective on the dynamics of harmful behavior in the workplace. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
7.
Jost John T.; Glaser Jack; Kruglanski Arie W.; Sulloway Frank J. 《Canadian Metallurgical Quarterly》2003,129(3):383
A meta-analysis by J. T. Jost, J. Glaser, A. W. Kruglanski, and F. J. Sulloway (2003) concluded that political conservatism is partially motivated by the management of uncertainty and threat. In this reply to J. Greenberg and E. Jonas (2003), conceptual issues are clarified, numerous political anomalies are explained, and alleged counterexamples are incorporated with a dynamic model that takes into account differences between "young" and "old" movements. Studies directly pitting the rigidity-of-the-right hypothesis against the ideological extremity hypothesis demonstrate strong support for the former. Medium to large effect sizes describe relations between political conservatism and dogmatism and intolerance of ambiguity; lack of openness to experience; uncertainty avoidance; personal needs for order, structure, and closure; fear of death; and system threat. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
8.
In many legal proceedings, fact finders scrutinize the demeanor of a defendant or witness, particularly his or her nonverbal behavior, for indicators of deception. This meta-analysis investigated directly observable nonverbal correlates of deception as a function of different moderator variables. Although lay people and professionals alike assume that many nonverbal behaviors are displayed more frequently while lying, of 11 different behaviors observable in the head and body area, only 3 were reliably associated with deception. Nodding, foot and leg movements, and hand movements were negatively related to deception in the overall analyses weighted by sample size. Most people assume that nonverbal behaviors increase while lying; however, these behaviors decreased, whereas others showed no change. There was no evidence that people avoid eye contact while lying, although around the world, gaze aversion is deemed the most important signal of deception. Most effect sizes were found to be heterogeneous. Analyses of moderator variables revealed that many of the observed relationships varied as a function of content, motivation, preparation, sanctioning of the lie, experimental design, and operationalization. Existing theories cannot readily account for the heterogeneity in findings. Thus, practitioners are cautioned against using these indicators in assessing the truthfulness of oral reports. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
9.
Scale selection using three different representations for images 总被引:1,自引:0,他引:1
J. Martinez-Baena J. A. García J. Fdez-Valdivia Rosa Rodriguez-Sanchez 《Pattern recognition letters》1997,18(14):1453-1467
10.
利用随机振动复模态分析,提出了一种求解时变线性系统,在确定性激励与随机激励共同作用下非平稳随机响应的计算方法,并以舰载火箭武器系统为研究对象,用该法探讨了海浪对舰面火箭发射初始扰动和系统振动特性的影响。 相似文献