全文获取类型
收费全文 | 67686篇 |
免费 | 10249篇 |
国内免费 | 6346篇 |
专业分类
电工技术 | 8180篇 |
技术理论 | 2篇 |
综合类 | 7114篇 |
化学工业 | 5091篇 |
金属工艺 | 2225篇 |
机械仪表 | 6516篇 |
建筑科学 | 2927篇 |
矿业工程 | 2146篇 |
能源动力 | 3078篇 |
轻工业 | 3752篇 |
水利工程 | 1665篇 |
石油天然气 | 2660篇 |
武器工业 | 906篇 |
无线电 | 5946篇 |
一般工业技术 | 5612篇 |
冶金工业 | 2278篇 |
原子能技术 | 316篇 |
自动化技术 | 23867篇 |
出版年
2024年 | 663篇 |
2023年 | 1752篇 |
2022年 | 2952篇 |
2021年 | 3055篇 |
2020年 | 3281篇 |
2019年 | 2777篇 |
2018年 | 2449篇 |
2017年 | 2998篇 |
2016年 | 3271篇 |
2015年 | 3616篇 |
2014年 | 5058篇 |
2013年 | 4855篇 |
2012年 | 5549篇 |
2011年 | 5660篇 |
2010年 | 3973篇 |
2009年 | 4168篇 |
2008年 | 3822篇 |
2007年 | 4341篇 |
2006年 | 3623篇 |
2005年 | 2970篇 |
2004年 | 2439篇 |
2003年 | 2014篇 |
2002年 | 1775篇 |
2001年 | 1451篇 |
2000年 | 1228篇 |
1999年 | 821篇 |
1998年 | 740篇 |
1997年 | 612篇 |
1996年 | 470篇 |
1995年 | 392篇 |
1994年 | 337篇 |
1993年 | 242篇 |
1992年 | 195篇 |
1991年 | 164篇 |
1990年 | 138篇 |
1989年 | 112篇 |
1988年 | 75篇 |
1987年 | 32篇 |
1986年 | 32篇 |
1985年 | 23篇 |
1984年 | 27篇 |
1983年 | 19篇 |
1982年 | 20篇 |
1981年 | 9篇 |
1980年 | 15篇 |
1979年 | 14篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1959年 | 4篇 |
1951年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
ADS Expert is an integrated system that (a) provides suggestions about suitable optimization algorithms for a particular structural optimization problem, (b) it offers explanations and guide lines, in the form of hypertext, that refer to the optimization strategy, optimizer and one dimensional search method, (c) it produces the required gradients for the objective function and the constraints using symbolic differentiation, (d) establishes a direct linking with ADS routines and (e) it monitors the evolution of the optimization process. The system can be used as an educational tool for structural optimization and as an efficient integrated system for small to medium size optimization problems for which the objective function and the constraints are given in the form of explicit functions of the design variables. The system is a Windows application and runs quite satisfactorily on PCs. 相似文献
22.
变结构变参数设计方法及其在机械CAD中的应用 总被引:4,自引:0,他引:4
提出了一种新颖的机械结构设计思想-变结构变参数设计方法,并结合实例,阐述了变结构变参数设计的概念、原则、实施措施和意义。由此对I-deas软件包进行了二次开发,编制了发动机曲轴专用CAD软件程序,并用某型号发动机曲轴进行了验证。 相似文献
23.
N. N. Radaev A. D. Daragan A. M. Agapov S. P. Voronov D. V. Klopov 《Measurement Techniques》2005,48(3):211-214
Neuronets are considered for processing data on the state of a potentially hazardous object after an emergency. An example is given of processing the data on the state of a potentially hazardous object in increments.Translated from Izmeritel’naya Tekhnika, No. 3, pp. 6–8, March, 2005. 相似文献
24.
This paper attempts to shed light on the determinants of energy demand in Turkey. Energy demand model is first proposed using the ant colony optimization (ACO) approach. It is multi-agent systems in which the behavior of each ant is inspired by the foraging behavior of real ants to solve optimization problem. ACO energy demand estimation (ACOEDE) model is developed using population, gross domestic product (GDP), import and export. All equations proposed here are linear and quadratic. Quadratic_ACOEDE provided better-fit solution due to fluctuations of the economic indicators. The ACOEDE model plans the energy demand of Turkey until 2025 according to three scenarios. The relative estimation errors of the ACOEDE model are the lowest when they are compared with the Ministry of Energy and Natural Resources (MENR) projection. 相似文献
25.
郑文新 《水科学与工程技术》2007,(4):25-27
黑河水利枢纽右岸溢洪洞为缩短引渠左导墙的长度,减少施工开挖量,降低施工难度,减少工程投资,进行优化试验.通过对7种不同的方案对比分析,选择了合适的体型,满足了工程要求. 相似文献
26.
模糊规划在炼油厂生产计划优化中的应用 总被引:7,自引:1,他引:6
生产计划的编制是炼油化工企业生产经营管理中的一个关键环节,然而由于市场变化的不确定性,使得企业的长远规划制定受到限制,笔者将模糊数学应用于炼厂生产计划的编制,通过模糊规划对炼油企业生产计划进行优化,使编得的生产计划在一定程度上反映市场的变化并使企业的生产效益最优,为企业管理决策者进行长期规划给予指导,给出了实例来说明该方法的可行性。 相似文献
27.
Many real-world problems are multi-objective optimization problems and evolutionary algorithms are quite successful on such problems. Since the task is to compute or approximate the Pareto front, multi-objective optimization problems are considered as more difficult than single-objective problems. One should not forget that the fitness vector with respect to more than one objective contains more information that in principle can direct the search of evolutionary algorithms. Therefore, it is possible that a single-objective problem can be solved more efficiently via a generalized multi-objective model of the problem. That this is indeed the case is proved by investigating the computation of minimum spanning trees.This work was supported by the Deutsche Forschungsgemeinschaft (DFG) as part of the Collaborative Research Center Computational Intelligence (SFB 531) and by the German-Israeli Foundation (GIF) in the project Robustness Aspects of Algorithms. 相似文献
28.
Optimal synthesis of tunable elastic wave-guides 总被引:1,自引:0,他引:1
Anton Evgrafov Cory J. Rupp 《Computer Methods in Applied Mechanics and Engineering》2008,198(2):292-301
Topology optimization, or control in the coefficients of partial differential equations, has been successfully utilized for designing wave-guides with precisely tailored functionalities. For many applications it would be desirable to have the possibility of drastically altering the wave-guiding properties of a device “on the fly,” in a controllable manner as an influence of some external input. This would enable wave-guides with highly non-linear input-output mappings, such as for example controllable wave switches.In this paper, we propose using finite elastic pre-straining for the purpose of tuning a wave-guide. In order to systematically formulate and solve the wave-guide synthesis problems we utilize mathematical programming methods in conjunction with topology optimization for parametrizing the design space. The resulting extremal problem is, from a practical point, equivalent to finding an optimal subdivision of a given control volume into two disjoint subsets occupied by two different materials, normally resulting in a highly heterogeneous elastic body with desired wave-guiding functionalities in the original and finitely deformed configurations.The proposed methodology is illustrated with numerical examples. 相似文献
29.
This study examined how 1 symbol is selected to control the allocation of attention when several symbols appear in the visual field. In Experiments 1-3, the critical target feature was color, and it was found that uninformative central arrows that matched the color of the target were selected and produced unintentional shifts of attention (i.e., involuntary, initiated slowly, producing long-lasting facilitatory effects). Experiment 4 tested whether such selection is the result of an attentional filter or of a competition bias due to a match of incoming information against integrated object representations stored in working memory. Here, the critical feature was shape and color was irrelevant, but matching color arrows were still selected. Thus, features of objects in working memory will bias the selection of symbols in the visual field, and such selected symbols are capable of producing unintentional shifts of attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
30.
I. Aidos N. Kreb M. Boonman J.B. Luten R.M. Boom A. Van Der Padt 《Journal of food science》2003,68(2):581-586
ABSTRACT: A pilot plant used for upgrading herring byproducts into fish oil was analyzed on its operational efficiency and product quality. The temperature of the heat exchanger and the speeds of the pump and the 3-phase decanter were varied according to a 23 fractional factorial design. The initial amount of oxidation products present in the crude oil, its storage stability, and the yields from the different obtained products were determined. Multivariate data analysis of the advanced screening stage showed that T had neither influence on the quality nor on the yield in contrast to D and MP (P < 0.05). Process optimization results showed that the quality of the oil was influenced by an interaction effect between the speed of the MP and the D. Oils processed with the highest MP speed were the most stable during storage. 相似文献