全文获取类型
收费全文 | 14911篇 |
免费 | 2075篇 |
国内免费 | 1625篇 |
专业分类
电工技术 | 580篇 |
技术理论 | 5篇 |
综合类 | 2228篇 |
化学工业 | 322篇 |
金属工艺 | 304篇 |
机械仪表 | 1298篇 |
建筑科学 | 986篇 |
矿业工程 | 278篇 |
能源动力 | 128篇 |
轻工业 | 396篇 |
水利工程 | 218篇 |
石油天然气 | 196篇 |
武器工业 | 106篇 |
无线电 | 1367篇 |
一般工业技术 | 1217篇 |
冶金工业 | 654篇 |
原子能技术 | 47篇 |
自动化技术 | 8281篇 |
出版年
2024年 | 122篇 |
2023年 | 297篇 |
2022年 | 522篇 |
2021年 | 516篇 |
2020年 | 513篇 |
2019年 | 371篇 |
2018年 | 359篇 |
2017年 | 368篇 |
2016年 | 472篇 |
2015年 | 543篇 |
2014年 | 779篇 |
2013年 | 920篇 |
2012年 | 908篇 |
2011年 | 995篇 |
2010年 | 913篇 |
2009年 | 921篇 |
2008年 | 1011篇 |
2007年 | 1112篇 |
2006年 | 997篇 |
2005年 | 856篇 |
2004年 | 798篇 |
2003年 | 724篇 |
2002年 | 558篇 |
2001年 | 491篇 |
2000年 | 450篇 |
1999年 | 384篇 |
1998年 | 264篇 |
1997年 | 191篇 |
1996年 | 217篇 |
1995年 | 202篇 |
1994年 | 162篇 |
1993年 | 124篇 |
1992年 | 115篇 |
1991年 | 80篇 |
1990年 | 69篇 |
1989年 | 77篇 |
1988年 | 52篇 |
1987年 | 31篇 |
1986年 | 23篇 |
1985年 | 27篇 |
1984年 | 7篇 |
1983年 | 11篇 |
1982年 | 4篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1965年 | 3篇 |
1963年 | 4篇 |
1962年 | 3篇 |
1960年 | 3篇 |
1958年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
71.
J. Clausen L. Damkilde L. Andersen 《International journal for numerical methods in engineering》2006,66(6):1036-1059
A new return method for implicit integration of linear isotropic yield criteria is presented. The basic idea is to perform all the manipulations in the principal stress space and thereby achieve very simple formulae for calculating the plastic corrector stresses, based on the constant gradient of such criteria. The return formulae are in closed form and no iteration is required. The method accounts for three types of stress return: return to a single yield plane, to a discontinuity line at the intersection of two yield planes and to a discontinuity point at the intersection between three or more yield planes. The infinitesimal and the consistent elastoplastic constitutive matrix are calculated for each type of stress return, as are the conditions to ascertain which type of return is required. The method is exemplified with the Mohr–Coulomb yield criterion. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
72.
E.I.P. Volcke M. Loccufier P.A. Vanrolleghem E.J.L. Noldus 《Journal of Process Control》2006,16(10):1003-1012
This paper addresses the dynamics of a SHARON reactor, a promising technology for ammonium removal from concentrated wastewater streams. The contraction mapping theorem is used to determine which operating conditions of a SHARON reactor with pH-control result in a unique equilibrium state. However, this approach only identifies the case of very large dilution rates, in practice corresponding with complete biomass wash-out, i.e. with complete loss of biological activity. Practical operation of a SHARON reactor aims at reaching ammonium conversion to nitrite. To identify such interesting operating points, the equilibrium points are subsequently calculated directly in terms of input variables for a simplified SHARON reactor model. The stability of the obtained equilibrium points is assessed and the corresponding phase portraits are analyzed. The influence of slightly varying parameter and input values is investigated as well. 相似文献
73.
An application of expert hierarchical control is described in this paper. The control is implemented in a two-level configuration, where the lower layer performs direct regulation control and the upper layer performs supervisory functions. In the regulation layer, a rule-based controller performs the regulation task, where the controller is constructed upon causal relations between subsystems. The control action is inferred from the measurement of both controlled and noncontrolled variables. In the supervisory layer, the main function is a fault diagnosis system which diagnoses faults on-line. The diagnosis is based upon reasoning from the structure of the system and the functions of its components, and efficient diagnosis is achieved by dividing the system into several subsystems. The overall technique has been successfully implemented on a pilot scale mixing process under on-line computer control. 相似文献
74.
T. Bag 《Information Sciences》2006,176(19):2910-2931
In this paper, definitions of strongly fuzzy convergent sequence, l-fuzzy weakly convergent sequence and l-fuzzy weakly compact set are given in a fuzzy normed linear space. The concepts of fuzzy normal structure, fuzzy non-expansive mapping, uniformly convex fuzzy normed linear space are introduced and fixed point theorems for fuzzy non-expansive mappings are proved. 相似文献
75.
An efficient return algorithm for non-associated plasticity with linear yield criteria in principal stress space 总被引:1,自引:0,他引:1
An efficient return algorithm for stress update in numerical plasticity computations is presented. The yield criterion must be linear in principal stress space and can be composed of any number of yield planes. Each of these yield planes may have an associated or non-associated flow rule. The stress return and the formation of the constitutive matrix is carried out in principal stress space. Here the manipulations simplify and rely on geometrical arguments. The singularities arising at the intersection of yield planes are dealt with in a straightforward way also based on geometrical considerations. The method is exemplified on non-associated Mohr–Coulomb plasticity throughout the paper. 相似文献
76.
77.
Ten areas of health knowledge were investigated in 2 studies, 1 of college students (N=169) and 1 of adults from the community (ages 19-70; N=176). Measures assessed knowledge of aging, orthopedic/ dermatological concerns, common illnesses, childhood/early life, serious illnesses, mental health, nutrition, reproduction, safety, and treatment of illness/disease. Significant gender differences favoring women were found for most areas of health knowledge, especially reproduction and early life. Results showed that cognitive ability accounted for the most variance in health knowledge with nonability (personality and interest traits) and demographic variables accounting for smaller but significant amounts of variance across most knowledge domains. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
78.
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
79.
王校艳 《河南机电高等专科学校学报》2004,12(2):11-12
知识经济对领导方法提出了新的要求,也使传统的领导方法面临严峻挑战,知识经济时代所需要的领导方法具有开拓创新性。 相似文献
80.
Colin Fyfe 《Data mining and knowledge discovery》2007,14(2):207-224
We review a new form of self-organizing map which is based on a nonlinear projection of latent points into data space, identical
to that performed in the Generative Topographic Mapping (GTM) [Bishop et al. (1997) Neurl Comput 10(1): 215–234]. But whereas
the GTM is an extension of a mixture of experts, our new model is an extension of a product of experts [Hinton (2000) Technical
report GCNU TR 2000-004, Gatsby Computational Neuroscience Unit, University College, London]. We show visualisation results
on some real data sets and compare with the GTM. We then introduce a second mapping based on harmonic averages and show that
it too creates a topographic mapping of the data. We compare these mappings on real and artificial data sets.
Responsible editor: Soumen Chakrabarti. 相似文献