全文获取类型
收费全文 | 17277篇 |
免费 | 687篇 |
国内免费 | 31篇 |
专业分类
电工技术 | 213篇 |
综合类 | 22篇 |
化学工业 | 3546篇 |
金属工艺 | 332篇 |
机械仪表 | 434篇 |
建筑科学 | 599篇 |
矿业工程 | 91篇 |
能源动力 | 387篇 |
轻工业 | 1090篇 |
水利工程 | 137篇 |
石油天然气 | 47篇 |
武器工业 | 1篇 |
无线电 | 1500篇 |
一般工业技术 | 3607篇 |
冶金工业 | 3487篇 |
原子能技术 | 159篇 |
自动化技术 | 2343篇 |
出版年
2023年 | 167篇 |
2022年 | 420篇 |
2021年 | 470篇 |
2020年 | 323篇 |
2019年 | 301篇 |
2018年 | 376篇 |
2017年 | 324篇 |
2016年 | 432篇 |
2015年 | 372篇 |
2014年 | 535篇 |
2013年 | 902篇 |
2012年 | 738篇 |
2011年 | 872篇 |
2010年 | 675篇 |
2009年 | 645篇 |
2008年 | 685篇 |
2007年 | 665篇 |
2006年 | 535篇 |
2005年 | 488篇 |
2004年 | 397篇 |
2003年 | 391篇 |
2002年 | 379篇 |
2001年 | 280篇 |
2000年 | 284篇 |
1999年 | 268篇 |
1998年 | 862篇 |
1997年 | 644篇 |
1996年 | 451篇 |
1995年 | 362篇 |
1994年 | 311篇 |
1993年 | 335篇 |
1992年 | 164篇 |
1991年 | 151篇 |
1990年 | 164篇 |
1989年 | 159篇 |
1988年 | 158篇 |
1987年 | 125篇 |
1986年 | 111篇 |
1985年 | 147篇 |
1984年 | 149篇 |
1983年 | 117篇 |
1982年 | 99篇 |
1981年 | 97篇 |
1980年 | 104篇 |
1979年 | 98篇 |
1978年 | 116篇 |
1977年 | 147篇 |
1976年 | 267篇 |
1975年 | 87篇 |
1974年 | 78篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Jonathan P. Belnoue Giang D. Nguyen Alexander M. Korsunsky 《International Journal of Fracture》2007,144(1):53-60
This paper presents a new 1-D non-local damage-plasticity deformation model for ductile materials. It uses the thermodynamic
framework described in Houlsby and Puzrin (2000) and holds, nevertheless, some similarities with Lemaitre’s (1971) approach.
A 1D finite element (FE) model of a bar fixed at one end and loaded in tension at the other end is introduced. This simple
model demonstrates how the approach can be implemented within the finite element framework, and that it is capable of capturing
both the pre-peak hardening and post-peak softening (generally responsible for models instability) due to damage-induced stiffness
and strength reduction characteristic of ductile materials. It is also shown that the approach has further advantages of achieving
some degree of mesh independence, and of being able to capture deformation size effects. Finally, it is illustrated how the
model permits the calculation of essential work of rupture (EWR), i.e. the specific energy per unit cross-sectional area that
is needed to cause tensile failure of a specimen. 相似文献
12.
Alexander E. Meyerovich 《Journal of Low Temperature Physics》2004,134(1-2):163-168
Similarities between alkali gases in optical lattices with non-integer occupation of the lattice sites and quantum crystals are explored. The analogy with the vacancy liquid provides an agternative explanation to the Mott transition for the recent experiment on the phase transition in the lattice. The vacancy liquid can undergo BEC with T c within experimental reach. Direct and vacancy-assisted mechanisms of the band motion for hyperfine impurities are discussed. The presence of vacancies can resugt in the spatial decomposition of the system into pure hyperfine components. Below BEC for the vacancies, the impurity component resembles 3He in 3He-Hell mixtures. 相似文献
13.
Yanqing Ji Hao Ying John Yen Shizhuo Zhu Daniel C. Barth‐Jones Richard E. Miller R. Michael Massanari 《国际智能系统杂志》2007,22(8):827-845
Discovering unknown adverse drug reactions (ADRs) in postmarketing surveillance as early as possible is highly desirable. Nevertheless, current postmarketing surveillance methods largely rely on spontaneous reports that suffer from serious underreporting, latency, and inconsistent reporting. Thus these methods are not ideal for rapidly identifying rare ADRs. The multiagent systems paradigm is an emerging and effective approach to tackling distributed problems, especially when data sources and knowledge are geographically located in different places and coordination and collaboration are necessary for decision making. In this article, we propose an active, multiagent framework for early detection of ADRs by utilizing electronic patient data distributed across many different sources and locations. In this framework, intelligent agents assist a team of experts based on the well‐known human decision‐making model called Recognition‐Primed Decision (RPD). We generalize the RPD model to a fuzzy RPD model and utilize fuzzy logic technology to not only represent, interpret, and compute imprecise and subjective cues that are commonly encountered in the ADR problem but also to retrieve prior experiences by evaluating the extent of matching between the current situation and a past experience. We describe our preliminary multiagent system design and illustrate its potential benefits for assisting expert teams in early detection of previously unknown ADRs. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 827–845, 2007. 相似文献
14.
Game AI is Dead. Long Live Game AI! 总被引:1,自引:0,他引:1
Alexander Nareyek 《Intelligent Systems, IEEE》2007,22(1):9-11
This paper discusses how the recent advances in game AI technology can help benefit industry and the academia. Some of these advances include large-scale automated art and content generation, automated storytelling, goal-driven virtual actors, and the ability to adapt to the player's preferences and mental state 相似文献
15.
C. Janke R. Jones S. Öberg P. R. Briddon 《Journal of Materials Science: Materials in Electronics》2007,18(7):775-780
Boron is observed to diffuse very slowly in germanium, as opposed to its behaviour in silicon where it exhibits Transient
Enhanced Diffusion effects in implanted samples. As a result of this slow diffusion, boron is a very stable dopant, allowing
devices to be created with very well-defined doping regions. To understand this superior performance, calculations were performed
on a variety of boron diffusion paths, within vacancy and interstitial mediated methods. It was found that the vacancy mediated
diffusion which is associated with the fast diffusion of many other species in germanium exhibits a total barrier of 5.8 eV.
Interstitial-mediated diffusion had a total barrier for migration of 3.4 eV in the neutral and singly negative charge states,
3.2 eV for the positive charge state, but a formation barrier of 4.1 eV. Thus the barrier for interstitial-mediated diffusion
is dominated by the formation energy of the self-interstitial. 相似文献
16.
A study of the trace elements emission (As, Se, Cd, Co, Cr, Cu, Zn, Hg, Tl, Pb, Ni, Sn, Sb, V, Mn and Fe) from pulverized coal combustion has been made at six heating and power stations situated in the Czech Republic. The amount of chlorine in coal has considerable influence on volatilization of some elements such as Zn, Cu, Pb, Hg and Tl, which is explained by the formation of thermodynamically stable compounds of these elements with chlorine. Generally, the affinities for Cl follows the order Tl > Cu > Zn > Pb > Co > Mn > Sn > Hg. The experimental data indicates enrichment of some of the trace toxic elements in the emissions (Cu, Zn, As, Se, Cd, Sn, Sb, Hg and Pb) and good agreement was obtained by thermodynamic equilibrium calculations with a few exceptions. In the case of Fe, Mn, Co, Cr and Sn calculated values are overestimated in the bottom ash and there are zero predicted amounts of these elements in the fly ash. In comparison, the results from experiments show up to 80% of these elements retained in fly ash. This implies that there exist additional steps leading to the enrichment by Fe, Mn, Co, Cr and Sn of small particles. Such mechanisms could include the ejection during devolatilization of small inorganic particles from the coal of bottom ash particles, or disintegration of the char containing these metals to small particles of fly ash. On the other hand, there are slightly overestimated or similar values of relative enrichment factors for As, V, Cu, Cd, Sb, Tl and Pb in the fly ashes and zero predicted values for bottom ashes. Our experimental results show about 5% or less of these elements are retained in bottom ashes, so they probably remain in the bottom ash inside unburned parts of coal. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
17.
The anisotropic nature of fibre reinforced composites leads to large stress concentrations around pin-loaded holes through standard weave cloths. Proper understanding of how this anisotropic nature affects the load distribution around holes can be utilised to reduce these concentrations if sufficient thought is given to the internal fibre geometry near to the hole. Such local reinforcements need not be highly complex and can be readily produced without excessive effort, producing significant improvements in performance. 相似文献
18.
Jones Kevin M.; Wickstrom Katherine F.; Friman Patrick C. 《Canadian Metallurgical Quarterly》1997,12(4):316
Evaluated the effects of performance feedback on levels of treatment integrity in school-based behavioral consultation. Three teachers employed in a residential treatment community were responsible for treatment implementation. Treatment integrity was defined as the percentage of 2-min intervals during which contingent teacher reinforcement for student on-task behavior was directly observed. Teacher and child behavior were monitored across baseline, traditional consultation, and consultation with performance feedback conditions in a multiple baseline design. Following a Problem Identification Interview and Problem Analysis Interview (J. R. Bergan, 1977), mean levels of treatment integrity for the 3 teachers ranged from 9% to 37%. The addition of a performance feedback package increased treatment integrity for all 3 teachers to levels ranging from 60% to 83%. The findings contribute to a growing literature supporting the need for direct assessment of treatment integrity in school-based consultation research and practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
19.
20.