全文获取类型
收费全文 | 42230篇 |
免费 | 4901篇 |
国内免费 | 3828篇 |
专业分类
电工技术 | 2870篇 |
技术理论 | 8篇 |
综合类 | 6238篇 |
化学工业 | 2878篇 |
金属工艺 | 986篇 |
机械仪表 | 2774篇 |
建筑科学 | 3518篇 |
矿业工程 | 1418篇 |
能源动力 | 1316篇 |
轻工业 | 573篇 |
水利工程 | 1077篇 |
石油天然气 | 939篇 |
武器工业 | 631篇 |
无线电 | 3959篇 |
一般工业技术 | 4625篇 |
冶金工业 | 2248篇 |
原子能技术 | 337篇 |
自动化技术 | 14564篇 |
出版年
2024年 | 295篇 |
2023年 | 939篇 |
2022年 | 1250篇 |
2021年 | 1410篇 |
2020年 | 1406篇 |
2019年 | 1238篇 |
2018年 | 1287篇 |
2017年 | 1457篇 |
2016年 | 1568篇 |
2015年 | 1640篇 |
2014年 | 2393篇 |
2013年 | 2853篇 |
2012年 | 2728篇 |
2011年 | 3062篇 |
2010年 | 2426篇 |
2009年 | 2573篇 |
2008年 | 2657篇 |
2007年 | 2755篇 |
2006年 | 2574篇 |
2005年 | 2220篇 |
2004年 | 1797篇 |
2003年 | 1508篇 |
2002年 | 1278篇 |
2001年 | 1060篇 |
2000年 | 917篇 |
1999年 | 824篇 |
1998年 | 653篇 |
1997年 | 596篇 |
1996年 | 483篇 |
1995年 | 475篇 |
1994年 | 384篇 |
1993年 | 327篇 |
1992年 | 293篇 |
1991年 | 216篇 |
1990年 | 183篇 |
1989年 | 196篇 |
1988年 | 158篇 |
1987年 | 74篇 |
1986年 | 102篇 |
1985年 | 76篇 |
1984年 | 78篇 |
1983年 | 52篇 |
1982年 | 63篇 |
1981年 | 47篇 |
1980年 | 37篇 |
1979年 | 36篇 |
1978年 | 31篇 |
1977年 | 29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 0 毫秒
41.
B. S. Seplyarskii S. V. Kostin G. B. Brauer 《International Journal of Self-Propagating High-Temperature Synthesis》2008,17(2):121-124
Explored is the filtration combustion in Ti-(Ti + 0.5C) layered powder systems in a coflow of nitrogen gas. The presence/absence
of nitrogen coflow through the layered system was found to drastically affect the character of wave propagation and structure/properties
of product. The obtained data can be regarded as a basis for fabrication of new layered and composite materials in the mode
of dynamic filtration combustion.
相似文献
42.
You-Im Chang Yu-Sheng Chen Wei-You Cheng 《Journal of the Chinese Institute of Chemical Engineers》2008,39(1):85-100
The deposition morphology of Brownian/non-Brownian particles within a constricted tube is investigated by applying the Brownian dynamics simulation method in the present paper. Two different geometric structures, the parabolic constricted tube (PCT) and the sinusoidal constricted tube (SCT), are adopted. The effect of various types of the total interaction energy curves of the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, and of the shadow area cast by those deposited particles, on the particles’ collection efficiencies are also examined. For the PCT structure, under the same interaction energy curve, it is found that the non-Brownian particles always own a higher collection efficiency than that of the Brownian particles. Since the deposition location moves closer to the constriction part of the tube, the collection efficiencies of the Brownian/non-Brownian particles increase with the decrease of flow velocity. The SCT behaves differently, it is found that the collection efficiencies of non-Brownian particles are only slightly higher than those of Brownian particles when SCT is adopted. The steep slope of the tube wall near the constriction part of SCT dominates the whole deposition process of Brownian/non-Brownian particles. In comparison with the available experimental data, it is found that the present method can give a good simulation result. 相似文献
43.
The appraisal process consists of the subjective evaluation that occurs during an individual's encounter with significant events in the environment, determining the nature of the emotional reaction and experience. Placed in the context of appraisal theories of emotion-elicitation and differentiation, the aim of the present research was to test empirically the hypothesis that the intrinsic pleasantness evaluation occurs before the goal conduciveness evaluation. In two studies, intrinsically pleasant and unpleasant images were used to manipulate pleasantness, and a specific event in a Pacman-type videogame was used to manipulate goal conduciveness. Facial EMG was used to measure facial reactions to each evaluation. As predicted, facial reactions to the intrinsic pleasantness manipulation were faster than facial reactions to the goal conduciveness manipulation. These results provide good empirical support for the sequential nature of the appraisal process. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
44.
Lowe Rob; Bennett Paul; Walker Ian; Milne Sarah; Bozionelos George 《Canadian Metallurgical Quarterly》2003,22(5):464
The theory of planned behavior suggests attitudes are a product of salient beliefs. This study examined whether aggregating salient beliefs was plausible within a more biologically centered information-processing environment. A neural network was used to examine associations among beliefs relating to exercise intention. Data on intentions and behavioral, normative, and control beliefs from 114 respondents were used to train (by error backpropagation) a neural network to associate beliefs with intention. The R2 between the network's estimated and self-reported intention was .66. The network's representation comprised 6 belief profiles associated with high, moderate, or low behavioral intention. The neural network accommodated complex relationships among beliefs and belief-intention associations and indicated how high-level constructs such as attitudes may be viewed as the best fit (compromise state) between aroused beliefs. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
45.
46.
In arc welding processes, because of the complexity and nonlinearity of heat transfer phenomena, it is often difficult to design an effective control system based upon an exact mathematical model. In this paper, a self-organizing fuzzy control method is proposed to obtain a uniform weld quality by regulation of the surface temperature at a desired level. The proposed control system is designed to comprise a combined structure of the fuzzy SOC with conventional PD control for improving the system's stability. The control experiments show that the proposed controller guarantees a uniform weld quality for various welding conditions. 相似文献
47.
Summary Recent progress in the modelling of exchanged Cu sites and their interactions with small molecules, based on DFT cluster calculations, is briefly reviewed. 相似文献
48.
We consider an extension of the functional programming language Standard ML with a modular structure based upon concepts in category theory such as categories, functors, natural transformations and adjunctions. In essence, we are following the categorical imperative of considering arrows as well as objects. This is intended to enforce a certain mathematical rigour on the programmer, so that the only programs that can be expressed are those with a categorical significance. The essentially algebraic nature of category theory means that we may generate equational correctness conditions for the modular structure of programs, thus separating the correctness of individual functions from that of modules. We describe this programming language, give examples of its use, and explain how it is implemented in a type system. 相似文献
49.
C. S. Kubrusly 《Systems & Control Letters》1992,19(3)
A discrete system is uniformly mean-square stable if uniform convergence is preserved between input and state correlation sequences, and if nuclearity is preserved between the input and state correlation limits. This paper supplies a contraction-free condition ensuring mean-square stability for infinite-dimensional bilinear systems evolving in a separable Hilbert space. 相似文献
50.
This paper deals with the issues of development and implementation of a real-time NURBS interpolator for a six-axis robot. Using an open-architecture controller system as a testbed, a real-time NURBS curve interpolator was developed, implemented and tested. Sample runs were conducted with the resulting trajectories measured in real-time during robot motion. The resulting trajectories are analyzed, discussed and compared with those from a commonly used point-to-point approximation technique. The real-time NURBS curve interpolator's feasibility, advantages and related issues are also discussed. 相似文献