全文获取类型
收费全文 | 39018篇 |
免费 | 4339篇 |
国内免费 | 2817篇 |
专业分类
电工技术 | 3001篇 |
技术理论 | 8篇 |
综合类 | 5940篇 |
化学工业 | 2929篇 |
金属工艺 | 1060篇 |
机械仪表 | 2570篇 |
建筑科学 | 3763篇 |
矿业工程 | 1527篇 |
能源动力 | 1397篇 |
轻工业 | 645篇 |
水利工程 | 1277篇 |
石油天然气 | 1051篇 |
武器工业 | 710篇 |
无线电 | 3406篇 |
一般工业技术 | 4558篇 |
冶金工业 | 2277篇 |
原子能技术 | 327篇 |
自动化技术 | 9728篇 |
出版年
2024年 | 166篇 |
2023年 | 659篇 |
2022年 | 885篇 |
2021年 | 1102篇 |
2020年 | 1269篇 |
2019年 | 1141篇 |
2018年 | 1185篇 |
2017年 | 1370篇 |
2016年 | 1467篇 |
2015年 | 1503篇 |
2014年 | 2269篇 |
2013年 | 2725篇 |
2012年 | 2562篇 |
2011年 | 2839篇 |
2010年 | 2244篇 |
2009年 | 2355篇 |
2008年 | 2448篇 |
2007年 | 2605篇 |
2006年 | 2370篇 |
2005年 | 2033篇 |
2004年 | 1619篇 |
2003年 | 1362篇 |
2002年 | 1160篇 |
2001年 | 943篇 |
2000年 | 811篇 |
1999年 | 748篇 |
1998年 | 582篇 |
1997年 | 504篇 |
1996年 | 443篇 |
1995年 | 426篇 |
1994年 | 353篇 |
1993年 | 293篇 |
1992年 | 268篇 |
1991年 | 200篇 |
1990年 | 161篇 |
1989年 | 174篇 |
1988年 | 133篇 |
1987年 | 68篇 |
1986年 | 91篇 |
1985年 | 68篇 |
1984年 | 67篇 |
1983年 | 49篇 |
1982年 | 55篇 |
1981年 | 42篇 |
1980年 | 32篇 |
1979年 | 31篇 |
1978年 | 29篇 |
1977年 | 26篇 |
1964年 | 26篇 |
1955年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
对快速击实试验研究成果进行了总结,并介绍了应用快速击实试验研究成果的经验.不论是重型击实还是轻型击实,也不论击实试验所给定的击实功能多大,应用"一点法"或"快速法"击实试验原理,对土料都有一定要求."一点法"击实试验与快速击实试验所用土体的比重在2.67~2.73之间,当被测土样的比重超越此范围时,在绘制击实曲线时可适当偏离ρdmax计算值的点,但这个误差是很小的,通常ρdmax的影响在±0.01 g/cm3以内,而对ωop的影响在±0.5%以内.结合工程实例,对击实试验成果的简化校正作了详细介绍. 相似文献
62.
Inaki Arrazola Agn s Plainfoss Henri Prade Claudette Testemale 《Information Systems》1989,14(6):487-492
This paper presents different approaches which enable a data base management system to obtain a plausible fuzzy estimate for an attribute value of an item for which the information is not explicitly stored in the data base. This can be made either by a kind of analogical reasoning from information about particular items or by means of expert rules which specify the (fuzzy) sets of possible values of the attribute under consideration, for various classes of items. Another kind of expert rules enables the system to compute an estimate from the attribute value of another item provided that, in other respects, this latter item sufficiently resembles the item, the value of which we are interested in; then these expert rules are used either for controlling the analogical reasoning process or for enlarging the scope of application of the first kind of expert rules. The different approaches are discussed in the framework of possibility theory. 相似文献
63.
Stolorow Robert D.; Atwood George E.; Orange Donna M. 《Canadian Metallurgical Quarterly》2006,23(1):184
In omitting crucial words and sentencees, neglecting relevant citations, and overlooking important distinctions, Jon Mills' (see record 2005-04819-001) critique of relational psychoanalysis significantly misrepresents the authors' viewpoint. This viewpoint seeks to contextualize, but not to nullify, individual worlds of experience and their limiting horizons. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
64.
A lubrication-flow model for a free film in a corner is presented. The model, written in the hyperbolic coordinate system
ξ = x
2 −y
2, η = 2xy, applies to films that are thin in the η-direction. The lubrication approximation yields two coupled evolution equations
for the film thickness and the velocity field which, to lowest order, describes plug flow in the hyperbolic coordinates. A
free film in a corner evolving under surface tension and gravity is investigated. The rate of thinning of a free film is compared
to that of a film evolving over a solid substrate. Viscous shear and normal stresses are both captured in the model and are
computed for the entire flow domain. It is shown that normal stress dominates over shear stress in the far field, while shear
stress dominates close to the corner.
This revised version was published online in October 2005 with corrected page numbers. 相似文献
65.
66.
Molecular dynamics simulations are used to investigate polymer networks made by either end-linking or randomly crosslinking a melt of linear precursor chains. The resulting network structures are very different, since end-linking leads to nearly ideal monodisperse networks, while random crosslinking leads to polydisperse networks, characterized by an exponential strand length distribution. Networks with average strand length 20 and 100 were generated. These networks were used to study the effects of disorder in the network connectivity on observables averaged either over the entire network or selected sub-structures. Heterogeneities in the randomly crosslinked networks cause significant differences in the localization of monomers, however, neither the localization of crosslinks nor the microscopic strain response are significantly affected. Compared to end-linked networks, randomly crosslinked networks have a slightly increased tube diameter, and as a result a slightly decreased shear modulus, but otherwise identical stress-strain behavior. For the investigated systems, we conclude that the microscopic strain response, tube diameter, and stress-strain relation are all insensitive to the heterogeneities due to the linking process by which the network were made. 相似文献
67.
The stress intensity factors for a short crack partially penetrating an inclusion of arbitrary shape
Some approximate solutions for predicting the stress intensity factor of a short crack penetrating an inclusion of arbitrary
shape have been developed under mode I and mode II loading conditions. The derivation of the fundamental formula is based
on the transformation toughening theory. The transformation strains in the inclusion are induced by the crack-tip field and
remotely applied stresses, and approximately evaluated by the Eshelby equivalent inclusion theory. As validated by detailed
finite element (FE) analyses, the developed solutions have good accuracy for different inclusion shape and for a wide range
of modulus ratio between inclusion and matrix material. 相似文献
68.
We propose a general modeling framework to evaluate the performance of cache consistency algorithms. In addition to the usual hit rate, we introduce the hit* rate as a consistency measure, which captures the fraction of non-stale downloads from the cache. We apply these ideas to the analysis of the fixed TTL consistency algorithm in the presence of network delays. The hit and hit* rates are evaluated when requests and updates are modeled by renewal processes. Classical results on the renewal function lead to various bounds. 相似文献
69.
J.C. Helton J.D. Johnson W.L. Oberkampf C.J. Sallaberry 《Reliability Engineering & System Safety》2006,91(10-11):1414-1434
Three applications of sampling-based sensitivity analysis in conjunction with evidence theory representations for epistemic uncertainty in model inputs are described: (i) an initial exploratory analysis to assess model behavior and provide insights for additional analysis; (ii) a stepwise analysis showing the incremental effects of uncertain variables on complementary cumulative belief functions and complementary cumulative plausibility functions; and (iii) a summary analysis showing a spectrum of variance-based sensitivity analysis results that derive from probability spaces that are consistent with the evidence space under consideration. 相似文献
70.
提出了一种考虑分布电容的故障测距新算法。该算法基于微分方程描述的线路数学模型,利用单端信息对高压输电线路进行故障测距,保留了解微分方程算法的简单可靠、现实可行、不必考虑衰减直流分量和谐波及电网频率波动影响的特点,同时考虑过渡电阻和分布电容的影响,克服了传统解微分方程法中在经高阻接地故障时测距误差过大和忽略分布电容引起的故障定位不准确的缺点。为了检验算法的精度,进行了大量的动模实验。结果表明,算法原理正确并具有较高的测距精度。 相似文献