全文获取类型
收费全文 | 5610篇 |
免费 | 1187篇 |
国内免费 | 892篇 |
专业分类
电工技术 | 74篇 |
综合类 | 712篇 |
化学工业 | 792篇 |
金属工艺 | 36篇 |
机械仪表 | 190篇 |
建筑科学 | 177篇 |
矿业工程 | 37篇 |
能源动力 | 19篇 |
轻工业 | 66篇 |
水利工程 | 35篇 |
石油天然气 | 27篇 |
武器工业 | 10篇 |
无线电 | 396篇 |
一般工业技术 | 298篇 |
冶金工业 | 827篇 |
原子能技术 | 9篇 |
自动化技术 | 3984篇 |
出版年
2024年 | 62篇 |
2023年 | 153篇 |
2022年 | 273篇 |
2021年 | 270篇 |
2020年 | 241篇 |
2019年 | 185篇 |
2018年 | 160篇 |
2017年 | 189篇 |
2016年 | 264篇 |
2015年 | 293篇 |
2014年 | 354篇 |
2013年 | 379篇 |
2012年 | 402篇 |
2011年 | 466篇 |
2010年 | 443篇 |
2009年 | 465篇 |
2008年 | 494篇 |
2007年 | 468篇 |
2006年 | 389篇 |
2005年 | 357篇 |
2004年 | 279篇 |
2003年 | 209篇 |
2002年 | 139篇 |
2001年 | 138篇 |
2000年 | 79篇 |
1999年 | 47篇 |
1998年 | 48篇 |
1997年 | 42篇 |
1996年 | 41篇 |
1995年 | 34篇 |
1994年 | 31篇 |
1993年 | 32篇 |
1992年 | 22篇 |
1991年 | 24篇 |
1990年 | 15篇 |
1989年 | 15篇 |
1988年 | 13篇 |
1987年 | 14篇 |
1986年 | 25篇 |
1985年 | 18篇 |
1984年 | 13篇 |
1982年 | 6篇 |
1964年 | 8篇 |
1962年 | 7篇 |
1960年 | 7篇 |
1959年 | 9篇 |
1958年 | 8篇 |
1957年 | 9篇 |
1956年 | 7篇 |
1954年 | 5篇 |
排序方式: 共有7689条查询结果,搜索用时 0 毫秒
11.
With video compression standards such as MPEG‐4, a transmission error happens in a video‐packet basis, rather than in a macroblock basis. In this context, we propose a semantic error prioritization method that determines the size of a video packet based on the importance of its contents. A video packet length is made to be short for an important area such as a facial area in order to reduce the possibility of error accumulation. To facilitate the semantic error prioritization, an efficient hardware algorithm for face tracking is proposed. The increase of hardware complexity is minimal because a motion estimation engine is efficiently re‐used for face tracking. Experimental results demonstrate that the facial area is well protected with the proposed scheme. 相似文献
12.
In this response to Jeffrey Stern's (2004) (see record 2004-21113-016) commentary on my article, "Giving the Devil His Due: Spite and the Struggle for Individual Dignity" (P. Shabad, 2000) (see record 2000-00917-004), I suggest that in emphasizing the conscious vindictiveness of explicit spite, Stern minimizes the perverse aspects of "cutting off one's nose to spite one's face" as a means of avenging oneself against powerful others. The underlying impetus of perverse spite is to break free from the prison of subtle developmental contingencies and unconscious seductions surrounding maternal possessiveness. When the child's self-assertive strivings are blocked because of the shame and fear of premature separateness, the inward obsessional churning of resentment becomes a fertile ground for perverse spite. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
13.
A nonlinear stress-strain relationship of soil reinforced with flexible geofibers under static loading is derived based on a nonlinear elastic stress-strain relationship of soil and a linear elastic stress-strain relationship of geofibers in the paper. This investigation includes the following aspects: First, the homogenization technique is introduced to find the volume average stress tensor and volume average strain tensor and further an elastic incremental stress-strain relation is introduced to describe deviatoric shear stress-axial strain relationship of equivalent homogeneous geofiber-reinforced soil. Second, the relation of geofiber numbers, content, mechanical behavior, distribution, and geometrical features to shear modulus of geofiber-reinforced soil is expressed and assessed by employing an elastic energy method. Third, the deviatoric shear stress and axial strain curves of geofiber-reinforced soil are calibrated by laboratory testing data of geofiber reinforced soil samples. Finally, the theoretical computational curves of geofiber reinforced soil are compared with the curves calibrated by testing data of geofiber reinforced soil. The model prediction has a good agreement with experimental results. 相似文献
14.
Yongxian Zhao Baochen Huang Wei Yao Hailin Cong Huafeng Shao Aihua Du 《应用聚合物科学杂志》2008,107(5):2986-2993
A new organic‐solvent‐free water‐phase suspension method was used to synthesize partially epoxidized high trans‐1,4‐polyisoprene (TPI) to improve its properties, including oil resistance and wet‐skid resistance. The epoxidation was conducted in an aqueous peracetic acid solution and on the TPI granules prepared by a bulk precipitation method with supported titanium catalyst. The effects of the synthesis conditions, including reaction temperature, reaction time, and pH value, on the epoxy content were investigated. Epoxidized trans‐1,4‐polyisoprene (ETPI) with epoxy contents between 10 and 80% were obtained within 4 h. Both the amorphous and crystalline regions of TPI were epoxidized. The crystallization properties decreased with increasing epoxy content. ETPIs possessed lower mechanical properties than TPI but could be enhanced by vulcanization. The oil resistance and wet‐skid resistance were significantly improved after epoxidation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
15.
The aim of this study was to bring to the surface the strategic use of imitative processes in the context of a 2-route model: (a) direct imitation, used in reproducing new, meaningless actions, and (b) imitation based on stored semantic knowledge of familiar meaningful actions. Three experiments were carried out with healthy participants who reproduced meaningful and meaningless actions within an established time limit. The study investigated 3 factors that could potentially affect the selection of processes used for imitation: (a) the composition of the experimental list (blocked or mixed presentation), (b) the presence-absence of instructions (Experiments 1 and 2), and (c) the relative proportions of the stimuli (Experiment 3). Overall, the results suggest that each of these factors influences the selection of imitative strategies in healthy individuals with temporarily reduced capacities, as happens in the case of brain-damaged patients. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
16.
Paulussen-Hoogeboom Marja C.; Stams Geert Jan J. M.; Hermanns Jo M. A.; Peetsma Thea T. D. 《Canadian Metallurgical Quarterly》2007,43(2):438
This meta-analytic review (k = 62 studies; N = 7,613 mother-child dyads) shows that effect sizes for the association between child negative emotionality and parenting were generally small and were moderated by sample and measurement characteristics. The association between more child negative emotionality and less supportive parenting was relatively strong in lower socioeconomic status families, reversed in higher socioeconomic status families, and limited to studies with relatively high percentages of participants from ethnic minorities and studies using parent report to assess negative emotionality. Higher levels of child negative emotionality were associated with more restrictive control in samples with less than 75% 1st-born children, as well as in infants and preschoolers, and in studies using parent report or composite measures to assess both negative emotionality and restrictive parenting. Finally, more child negative emotionality was associated with less inductive control. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
17.
By DTA and x-ray diffraction the phase relations in the pseudobinary system In-CuInS2 have been investigated. CuInS2 hs a melting point of 1090° C and within this system there is a broad region of liquid immiscibility. A four phase
invariant reaction exists at 633° C which is of the form: L2 = L1+ CuInS2 + InS. 相似文献
18.
A genetic algorithm for the optimisation of assembly sequences 总被引:6,自引:0,他引:6
This paper describes a Genetic Algorithm (GA) designed to optimise the Assembly Sequence Planning Problem (ASPP), an extremely diverse, large scale and highly constrained combinatorial problem. The modelling of the ASPP problem, which has to be able to encode any industrial-size product with realistic constraints, and the GA have been designed to accommodate any type of assembly plan and component. A number of specific modelling issues necessary for understanding the manner in which the algorithm works and how it relates to real-life problems, are succinctly presented, as they have to be taken into account/adapted/solved prior to Solving and Optimising (S/O) the problem. The GA has a classical structure but modified genetic operators, to avoid the combinatorial explosion. It works only with feasible assembly sequences and has the ability to search the entire solution space of full-scale, unabridged problems of industrial size. A case study illustrates the application of the proposed GA for a 25-components product. 相似文献
19.
20.
社会网络是通过朋友关系、工作关系和信息交换等一组社会机制,将人、组织和其他社会团结联系在一起形成的网络,Web就是一种社会网络.在社会网络中要求有一种自然的机制对网络的真实性进行判断和评价,信任模型就是比较好的一种机制.基于社会网络,本文构建了一种网络信任模型,用来估算信任者和被信任者之间的信任等级,能够用于语义网的信任管理系统和社会网络的信任评价中.实验结果表明,该模型具有很好的效率和效果. 相似文献