全文获取类型
收费全文 | 18253篇 |
免费 | 2908篇 |
国内免费 | 1977篇 |
专业分类
电工技术 | 2020篇 |
技术理论 | 1篇 |
综合类 | 2540篇 |
化学工业 | 1787篇 |
金属工艺 | 359篇 |
机械仪表 | 1626篇 |
建筑科学 | 687篇 |
矿业工程 | 326篇 |
能源动力 | 485篇 |
轻工业 | 1142篇 |
水利工程 | 443篇 |
石油天然气 | 513篇 |
武器工业 | 323篇 |
无线电 | 1576篇 |
一般工业技术 | 1440篇 |
冶金工业 | 909篇 |
原子能技术 | 76篇 |
自动化技术 | 6885篇 |
出版年
2024年 | 75篇 |
2023年 | 223篇 |
2022年 | 534篇 |
2021年 | 565篇 |
2020年 | 541篇 |
2019年 | 498篇 |
2018年 | 477篇 |
2017年 | 555篇 |
2016年 | 734篇 |
2015年 | 856篇 |
2014年 | 1066篇 |
2013年 | 1275篇 |
2012年 | 1315篇 |
2011年 | 1471篇 |
2010年 | 1237篇 |
2009年 | 1326篇 |
2008年 | 1455篇 |
2007年 | 1637篇 |
2006年 | 1487篇 |
2005年 | 1218篇 |
2004年 | 1064篇 |
2003年 | 820篇 |
2002年 | 661篇 |
2001年 | 518篇 |
2000年 | 442篇 |
1999年 | 260篇 |
1998年 | 201篇 |
1997年 | 142篇 |
1996年 | 101篇 |
1995年 | 67篇 |
1994年 | 34篇 |
1993年 | 34篇 |
1992年 | 28篇 |
1991年 | 28篇 |
1990年 | 20篇 |
1989年 | 15篇 |
1988年 | 23篇 |
1987年 | 15篇 |
1986年 | 14篇 |
1985年 | 9篇 |
1984年 | 13篇 |
1962年 | 5篇 |
1961年 | 3篇 |
1960年 | 3篇 |
1959年 | 11篇 |
1958年 | 6篇 |
1957年 | 10篇 |
1956年 | 8篇 |
1955年 | 4篇 |
1954年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Yurak Son Takuya Kamano Takashi Yasuno Takayuki Suzuki Hironobu Harada 《Electrical Engineering in Japan》2006,155(1):35-43
This paper describes the generation of adaptive gait patterns using new Central Pattern Generators (CPGs) including motor dynamic models for a quadruped robot under various environments. The CPGs act as the flexible oscillators of the joints and adjust joint angles to required values. The CPGs are interconnected with each other and sets of their coupling parameters are adjusted by a genetic algorithm so that the quadruped robot can realize stable and adequate gait patterns. Generation of gait patterns results in the formation of the CPG networks suitable for the formation of not only a straight walking pattern but also of rotating gait patterns. Experimental results demonstrate that the proposed CPG networks are effective for the automatic adjustment of the adaptive gait patterns for the tested quadruped robot under various environments. Furthermore, the target tracking control based on image processing is achieved by combining the general gait patterns. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(1): 35–43, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20225 相似文献
22.
David Arditi 《Canadian Metallurgical Quarterly》1985,111(1):1-14
Construction productivity has been on the decline in the last decade. The results are presented on a survey of the Engineering News‐Record 400 largest contractors to obtain their views on where productivity improvements would most help and to compare the trends with a similar survey carried out in 1979. Data were collected on the general company characteristics of the responding contractors, and on the contractors' opinions on potential areas for productivity improvement in the office and in the field. Findings indicate that immediate research should concentrate on improving marketing practices, planning and scheduling, labor‐management relations, site supervision, industrialized building systems, equipment policy and engineering design; and that governmental regulations have lost the immediate urgency attached to them in 1979.It is also recommended that similar surveys be conducted every 3 to 4 years to identify new trends and to steer research in the appropriate direction. 相似文献
23.
Free radical emulsion polymerization of methyl methacrylate (MMA) and 2‐ethylhexyl acrylate (EHA) results in the synthesis of pressure‐sensitive adhesives (PSAs) with good tack properties. Management of both the copolymer composition and the polymerization process allows one to control the behavior of the PSA. Semicontinuous (SC) processes create polymer particles whose instantaneous composition is close to that of the feed particle The SC Mixture process (continuous feeding with comonomer blends) affords nearly homogeneous latex particles and PSA films. The SC Gradient process (separate feedings at inversely varying rates) affords heterogeneous particles and films. The Batch process leads to somewhat heterogeneous films, but the hard (MMA‐rich) microdomains are made compatible with their soft (EHA‐rich) matrix because of the assumed formation of tapered‐type copolymers. Tack measurements indicate the importance of the particle and film structures. Too much hardness or softness leads to unacceptable lacks of adhesion and cohesion, respectively. Homogeneous structures prove adequate, but their tack properties collapse with rising temperature. Heterogeneous structures, with extensive phase segregation, prove unsatisfactory because they lack adhesion and cohesion. Finally, the association of well‐balanced composition and compatible heterogeneity is the criterion for suitable PSA behavior. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2749–2756, 2003 相似文献
24.
25.
26.
基于混合遗传算法的树状注水管网拓扑优化 总被引:4,自引:1,他引:3
以投资最小为目标函数,以井间隶属关系的惟一性、连接注水井数量等限制为约束条件,建立了树状注水管网拓扑优化数学模型.根据模型特点,将优化问题分为分配层和几何层,分别采用遗传算法和非线性优化方法进行求解.并对遗传算法的操作过程进行了改进,调整了适应函数,采用随机多父辈适应函数值加权交叉和多种变异操作,结合了模拟退火算法,并给出了初温的确定方法,改进了选择复制操作,从而形成了混合遗传算法.该算法能够有效地提高收敛速度,避免早熟收敛.利用算例说明了该方法的有效性. 相似文献
27.
A stochastic model is proposed for a basic mechanism in the formation of uncertainties in physical quantity measurements.
__________
Translated from Izmeritel'naya Tekhnika, No. 1, pp. 12–17, January, 2006. 相似文献
28.
Design optimization of 3D steel structures: Genetic algorithms vs. classical techniques 总被引:1,自引:0,他引:1
María Belén Prendes Gero Antonio Bello García 《Journal of Constructional Steel Research》2006,62(12):1303-1309
In this paper an elitist genetic algorithm (GA) developed by the authors is compared with common commercial solutions for complex structural optimization. After its prior validation on two-dimensional (2D) structures, the GA was tuned and improved in order to obtain structural elements with minimum weights that satisfy the ultimate limit states of the applicable building code. Subsequently, the same spatial structures were optimized using a commercial structural analysis program. Finally, the cost and weight improvements obtained using the GA, although at a higher computational cost, are discussed. 相似文献
29.
供需链设计优化问题由于其自身的复杂性而成为一个极具挑战性的研究课题。本文把Petri网与遗传算法结合起来,用于研究供需链设计优化,构建一个供需链原型测试系统,并对小汽车制造供需链系统进行了实例分析。 相似文献
30.
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