全文获取类型
收费全文 | 5086篇 |
免费 | 171篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 65篇 |
综合类 | 2篇 |
化学工业 | 1262篇 |
金属工艺 | 78篇 |
机械仪表 | 113篇 |
建筑科学 | 231篇 |
矿业工程 | 7篇 |
能源动力 | 176篇 |
轻工业 | 371篇 |
水利工程 | 28篇 |
石油天然气 | 11篇 |
无线电 | 578篇 |
一般工业技术 | 892篇 |
冶金工业 | 567篇 |
原子能技术 | 61篇 |
自动化技术 | 821篇 |
出版年
2022年 | 55篇 |
2021年 | 82篇 |
2020年 | 47篇 |
2019年 | 61篇 |
2018年 | 85篇 |
2017年 | 102篇 |
2016年 | 130篇 |
2015年 | 88篇 |
2014年 | 120篇 |
2013年 | 262篇 |
2012年 | 218篇 |
2011年 | 260篇 |
2010年 | 215篇 |
2009年 | 223篇 |
2008年 | 220篇 |
2007年 | 220篇 |
2006年 | 226篇 |
2005年 | 162篇 |
2004年 | 178篇 |
2003年 | 143篇 |
2002年 | 148篇 |
2001年 | 112篇 |
2000年 | 104篇 |
1999年 | 83篇 |
1998年 | 167篇 |
1997年 | 140篇 |
1996年 | 116篇 |
1995年 | 106篇 |
1994年 | 98篇 |
1993年 | 88篇 |
1992年 | 55篇 |
1991年 | 40篇 |
1990年 | 51篇 |
1989年 | 43篇 |
1988年 | 46篇 |
1987年 | 47篇 |
1986年 | 26篇 |
1985年 | 79篇 |
1984年 | 59篇 |
1983年 | 54篇 |
1982年 | 47篇 |
1981年 | 80篇 |
1980年 | 46篇 |
1979年 | 50篇 |
1978年 | 19篇 |
1977年 | 37篇 |
1976年 | 46篇 |
1975年 | 41篇 |
1974年 | 30篇 |
1973年 | 26篇 |
排序方式: 共有5263条查询结果,搜索用时 15 毫秒
81.
Optical field concentration in low-index waveguides 总被引:1,自引:0,他引:1
We present a highly efficient optical field concentrator that is capable of confining optical field in nanometer-thin low-index media with very high optical confinement factor. The structure is made of multiple-layered low-index nanolayers embedded in high-index silicon waveguides. By creating multiple high-index-contrast interfaces, the normal field in the low-index nanolayer regions is significantly enhanced. It subsequently results in a very high optical confinement and power density in these regions. With the help of numerical simulation tools, the guiding and propagating characteristics of the new structure are studied and presented. The optimal structures have demonstrated confinement factors and normalized power densities in the range of 30%-60% and 20-160 /spl mu/m/sup -2/ for the 5-20-nm thin low-index multiple nanolayers. 相似文献
82.
Methodology for the reliability evaluation of a passive system and its integration into a Probabilistic Safety Assessment 总被引:2,自引:0,他引:2
Michel Marqus J.F. Pignatel P. Saignes F. DAuria L. Burgazzi C. Müller R. Bolado-Lavin C. Kirchsteiger V. La Lumia I. Ivanov 《Nuclear Engineering and Design》2005,235(24):1864-2631
A methodology has been developed to evaluate the reliability of passive systems characterised by a moving fluid and whose operation is based on thermal–hydraulic (T-H) principles. The methodology includes:
- • identification and quantification of the sources of uncertainties and determination of the important variables;
- • propagation of the uncertainties through T-H models and assessment of T-H passive system unreliability;
- • introduction of passive system unreliability in the accident sequence analysis.
83.
We consider the parallelization of two standard 2D reconstruction algorithms, filtered backprojection and direct Fourier reconstruction, using the data-parallel programming style. The algorithms are implemented on a Connection Machine CM-5 with 16 processors and a peak performance of 2 Gflop/s. 相似文献
84.
The study objective was to describe the perceptions of airplane assemblers on job demand for the back and how back pain modulated these perceptions. One hundred and seventy-six workers answered two questionnaires concerning back pain and the perception of work related difficulties (work activities, work contexts, tools, work positions, efforts). Results show that positions and work contexts are perceived as greater sources of difficulty than efforts or dynamic activities. The duration of a given position is more important than its frequency. Back pain has a significant but complex impact on the perception of difficulty. Assemblers appear to integrate several factors when evaluating their difficulties as opposed to individual aspects, as it is often measured in ergonomic studies. The results have important implications for the measurement of ergonomic factors in the genesis of back pain and illustrates the potential for misclassification and biases in current epidemiologic studies. 相似文献
85.
This paper addresses the issue of improving the performance of memory management for real-time Java applications, building upon the real-time specification for Java (RTSJ) from the Real-Time Java Expert Group. In a first step, a collecting dynamic memory solution including both a real-time garbage collector and region-based memory management, is proposed. A thorough analysis of the parameters influencing the performance of write barriers in memory management, together with ways of improvement are then presented. Finally, the implementation of a memory management solution compliant with the RTSJ and integrating the proposed improvements is sketched. 相似文献
86.
This book is the result of months of work by a small group interested in ethical debates surrounding diverse professional practices. The different chapters examine the relationships among ethics, morality, and psychology. Of special interest are ethical questions relating to the conduct of research; the use and interpretation of standardized tests, given issues of validity and reliability; and the problems of developing and transmitting expertise in psychological practice. The values of respect, liberty, and justice are seen as relevant and applicable to psychological practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
87.
Negro Catherine Del; Kreutzer Michel; Gahr Manfred 《Canadian Metallurgical Quarterly》2000,114(3):526
During the breeding season under long-day conditions, male canaries sing sexually attractive songs and females respond behaviorally to such songs. This study assessed whether auditory response properties of neurons in nucleus HVc of female and male canaries are tuned to sexually salient song features: special song phrases and canary song segmentation. In sexually receptive female canaries, neurons responded to special song phrases with a decreased spike rate and were sensitive to canary song segmentation. The nonreceptive females showed no clear response to special song phrases. In females on short days, neurons responded to song phrases with an increase in activity. In males on long days, they exhibited phasic responses after the phrase onset, whatever the song phrase and song segmentation. This study demonstrates both a plasticity in relation to females' sexual responsiveness and a sexual dimorphism in the auditory processing performed in the HVc. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
88.
Verena Moosbrugger-Martinz Corinne Leprince Marie-Claire Mchin Michel Simon Stefan Blunder Robert Gruber Sandrine Dubrac 《International journal of molecular sciences》2022,23(10)
The discovery in 2006 that loss-of-function mutations in the filaggrin gene (FLG) cause ichthyosis vulgaris and can predispose to atopic dermatitis (AD) galvanized the dermatology research community and shed new light on a skin protein that was first identified in 1981. However, although outstanding work has uncovered several key functions of filaggrin in epidermal homeostasis, a comprehensive understanding of how filaggrin deficiency contributes to AD is still incomplete, including details of the upstream factors that lead to the reduced amounts of filaggrin, regardless of genotype. In this review, we re-evaluate data focusing on the roles of filaggrin in the epidermis, as well as in AD. Filaggrin is important for alignment of keratin intermediate filaments, control of keratinocyte shape, and maintenance of epidermal texture via production of water-retaining molecules. Moreover, filaggrin deficiency leads to cellular abnormalities in keratinocytes and induces subtle epidermal barrier impairment that is sufficient enough to facilitate the ingress of certain exogenous molecules into the epidermis. However, although FLG null mutations regulate skin moisture in non-lesional AD skin, filaggrin deficiency per se does not lead to the neutralization of skin surface pH or to excessive transepidermal water loss in atopic skin. Separating facts from chaff regarding the functions of filaggrin in the epidermis is necessary for the design efficacious therapies to treat dry and atopic skin. 相似文献
89.
Joachim Pistorius & Michel Minoux 《International Transactions in Operational Research》2003,10(1):1-11
Algorithms described so far to solve the maximum flow problem on hypergraphs first necessitate the transformation of these hypergraphs into directed graphs. The resulting maximum flow problem is then solved by standard algorithms. This paper describes a new method that solves the maximum flow problem directly on hypergraphs, leading to both reduced run time and lower memory requirements. We compare our approach with a state–of–the–art algorithm that uses a transformation of the hypergraph into a directed graph and an augmenting path algorithm to compute the maximum flow on this directed graph: the run–time complexity as well as the memory space complexity are reduced by a constant factor. Experimental results on large hypergraphs from VLSI applications show that the run time is reduced, on average, by a factor approximately 2, while memory occupation is reduced, on average, by a factor of 10. This improvement is particularly interesting for very large instances, to be solved in practical applications. 相似文献
90.
Michel Cosnard Luigi Liquori Raphael Chand 《Electronic Notes in Theoretical Computer Science》2007,171(3):55
Arigatoni is a lightweight overlay network that deploys the Global Computing Paradigm over the Internet. Communication for over the behavioral units of the overlay is performed by a simple resource discovery protocol (RDP). Basic Global Computers Units (GC) can communicate by first registering to a brokering service and then by mutually asking and offering services.Colonies and communities are the main entities in the model. A colony is a simple virtual organization composed by exactly one leader and some set (possibly empty) of individuals. A community is a raw set of colonies and global computers (think it as a soup of colonies and global computer without a leader).We present an operational semantics via a labeled transition system, that describes the main operations necessary in the Arigatoni model to perform leader negotiation, joining/leaving a colony, linking two colonies and moving one GC from one colony to another. Our formalization results to be adequate w.r.t. the algorithm performing peer logging/delogging and colony aggregation. 相似文献