全文获取类型
收费全文 | 6652篇 |
免费 | 599篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 75篇 |
综合类 | 13篇 |
化学工业 | 1865篇 |
金属工艺 | 120篇 |
机械仪表 | 140篇 |
建筑科学 | 280篇 |
矿业工程 | 14篇 |
能源动力 | 188篇 |
轻工业 | 752篇 |
水利工程 | 39篇 |
石油天然气 | 14篇 |
无线电 | 730篇 |
一般工业技术 | 1245篇 |
冶金工业 | 652篇 |
原子能技术 | 83篇 |
自动化技术 | 1058篇 |
出版年
2023年 | 34篇 |
2022年 | 76篇 |
2021年 | 123篇 |
2020年 | 121篇 |
2019年 | 153篇 |
2018年 | 183篇 |
2017年 | 201篇 |
2016年 | 231篇 |
2015年 | 208篇 |
2014年 | 299篇 |
2013年 | 464篇 |
2012年 | 358篇 |
2011年 | 471篇 |
2010年 | 373篇 |
2009年 | 352篇 |
2008年 | 362篇 |
2007年 | 274篇 |
2006年 | 277篇 |
2005年 | 228篇 |
2004年 | 209篇 |
2003年 | 199篇 |
2002年 | 178篇 |
2001年 | 126篇 |
2000年 | 128篇 |
1999年 | 103篇 |
1998年 | 118篇 |
1997年 | 96篇 |
1996年 | 114篇 |
1995年 | 77篇 |
1994年 | 98篇 |
1993年 | 79篇 |
1992年 | 61篇 |
1991年 | 47篇 |
1990年 | 62篇 |
1989年 | 52篇 |
1988年 | 36篇 |
1987年 | 40篇 |
1986年 | 41篇 |
1985年 | 48篇 |
1984年 | 51篇 |
1983年 | 43篇 |
1982年 | 41篇 |
1981年 | 37篇 |
1980年 | 35篇 |
1979年 | 47篇 |
1977年 | 44篇 |
1976年 | 31篇 |
1975年 | 24篇 |
1974年 | 24篇 |
1973年 | 24篇 |
排序方式: 共有7268条查询结果,搜索用时 15 毫秒
41.
François Treussart Nicolas Dubreuil Jongthan Cave Knight Vahid Sandoghdar Jean Hare Valçrie Lefçvre-Seguin Jean-Michel Raimond Serge Haroche 《电信纪事》1997,52(11-12):557-568
Light can be confined efficiently in the high-Q, small-volume whispering-gallery-modes observed in silica microspheres. By coupling these microspheres to eroded optical fibers and fiber tips, direct mapping of the whispering-gallery modes has been achieved and the mode numbers have been assessed. The properties of these modes have allowed us to obtain laser action with very low thresholds in Nd-doped silica microspheres. Further projects in the field of non-linear optics and cavity quantum electrodynamics are described. 相似文献
42.
Jrme Bachmann Jean marc Linares Jean Michel Sprauel Pierre Bourdet 《Precision Engineering》2004,28(1):342-88
The authorities of the standards organization International Organization of Standardization (ISO) advocate mastering any uncertainties in all parts of the industrialization process. In the three-dimensional (3D) measurement process, uncertainty is usually obtained at the end of a battery of tests. It is defined as a whole because it includes several types of errors, known systematic components, unknown systematic components and random components. Automated calculations of uncertainty can be made based on statistics. This method is based on statistical concepts, which are in accordance with “The Guide to the expression of the uncertainty in measurement” (GUM). It also enables us to generate uncertainties on the verification of ISO specifications (or specs in the ISO directives). In the course of this article, a usage will be presented that takes the knowledge of uncertainties into account: this usage will help the operator to take a decision on the conformance of a mechanical part in reference to its conformance to geometric tolerance. 相似文献
43.
Bourque Paul; Blanchard Louis; Saulnier Jo?l; Vézina Jean 《Canadian Metallurgical Quarterly》1992,24(1):118
Studied the relationship among age, physical health status, and psychic and somatic symptoms of depression among elderly adults. Human Ss: 318 male and female Canadian older adults (aged 65–102 yrs). Information on sociodemographic factors and health status was obtained using the Older American Research Scale, French version, by R. Lefran?ois et al (1988). A French version by P. Bourque and D. Beaudette (1982) of the Beck Depression Inventory was also used. The results were evaluated according to each S's sex, age, institutionalized residence status, and health status. Statistical tests were used. (English abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
44.
Forster Jean L.; Jeffery Robert W.; Schmid Thomas L.; Kramer F. Matthew 《Canadian Metallurgical Quarterly》1988,7(6):515
Evaluated the feasibility and effectiveness of a program for weight gain prevention (WGP) in normal adults. 219 Ss were randomized to either WGP treatment or no treatment for 12 mo. The treatment group received monthly newsletters relating to weight management, participated in a financial incentive system, and were offered an optional 4-session education course in the 6th mo of the program. Results demonstrate high interest in WGP among Ss who were not objectively overweight. Participation, as measured by return of postcards sent with each newsletter, was approximately 75%. Results after 1 yr show a net weight loss of 1.8 lb in the group receiving the program compared with controls. 82% of participants maintained or lost weight, compared with 56% of controls. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
45.
Auguste Commeyras Hlne Collet Laurent Boiteau Jacques Taillades Odile Vandenabeele‐Trambouze Herv Cottet Jean‐Philippe Biron Raphaël Plasson Louis Mion Olivier Lagrille Herv Martin Franck Selsis Michel Dobrijevic 《Polymer International》2002,51(7):661-665
Addressing the still open question of the prebiotic origin of sequential macromolecules (peptides, nucleic acids) on the primitive Earth, we describe a molecular engine (the primary pump), which works at ambient temperature and continuously generates, elongates and complexifies sequential peptides. This new scenario is based on a cyclic reaction sequence, whose keystep is the activation of amino acids into their N‐carboxyanhydrides (NCA) through nitrosation by NOx. This process could have taken place on tidal beaches; it requires a buffered ocean, emerged land and a nitrosating atmosphere. With the help of geochemical studies and computer simulations of atmosphere photochemistry, we show that the primitive Earth during the Hadean may have satisfied all these requirements. © 2001 Society of Chemical Industry. 相似文献
46.
André Girard Pierre Dominique Lansard Bernard Liau Anne Marie Mongeon Jean Luc Thibault 《电信纪事》1991,46(5-6):335-350
Classical hierarchical routing in telephone networks is extended to a wider class called out-of-chain routing in such a way that some useful properties of hierarchical routing are retained. This new routing pattern offers more potential paths than the fixed hierarchical one and can be introduced as a dynamic routing where the fixed alternate sequences change at some predetermined instants during the day. The effect of this new routing pattern on the network performances is examined. The main topic of this paper is to present heuristic methods used to optimise such routings in large networks. We show on artificial networks that the throughput of a given network can be significantly improved by suitable routing choices. We demonstrate that the integration of routing changes within a multihour dimensioning process is possible but the lack of realistic data does not permit at this time to quantify the value of routing optimization on real networks. 相似文献
47.
To disperse nano-sized γ-alumina powders in non-polar solvents, the surface of γ-alumina has to be modified with unsaturated oleic acid, which forms aluminum-oleate on the surface. This changes the surface characteristics of γ-alumina powders from hydrophilic to hydrophobic in nature. A colloidally stable γ-alumina non-polar suspension is obtained when a critical amount of aluminum-oleate compound is formed on the surface. This is also evidenced by the results of adsorption and theoretical calculation of potential energies, which confirm the colloidal stability of organic γ-alumina suspension caused by the steric repulsion mechanism. 相似文献
48.
Christophe Lombard Stephane Le Doze Eric Marencak Paul-Marie Marquaire David Le Noc Grégory Bertrand François Lapicque 《International Journal of Hydrogen Energy》2006
The paper reports the results of on-site regeneration catalytic bed of the natural gas reformer in a 5 kW PEM fuel cell system. The Ni catalyst previously poisoned by sulphur from the available natural gas, could be re-activated by injection of pure water steam, following the method developed for industrial reformers using the same metal catalyst: this method was shown to be perfectly efficient, provided no natural gas was fed during the operation. Results of the tests conducted are presented and discussed in relation to published data on S-sorption on Ni surfaces. 相似文献
49.
50.
High accuracy path tracking for vehicles in presence of sliding: Application to farm vehicle automatic guidance for agricultural tasks 总被引:1,自引:0,他引:1
Roland Lenain Benoit Thuilot Christophe Cariou Philippe Martinet 《Autonomous Robots》2006,21(1):79-97
When designing an accurate automated guidance system for vehicles, a major problem is sliding and pseudo-sliding effects. This is especially the case in agricultural applications, where five-centimetre accuracy with respect to the desired trajectory is required, although the vehicles are moving on slippery ground. It has been established that RTK GPS was a very suitable sensor to achieve automated guidance with such high precision: several control laws have been designed for vehicles equipped with this sensor, and provide the expected guidance accuracy as long as the vehicles do not slide. In previous work, further control developments have been proposed to take sliding into account: guidance accuracy in slippery environments has been shown to be preserved, except transiently at the beginning/end of curves. In this paper, the design of this control law is first recalled and discussed. A Model Predictive Control method is then applied in order to preserve accuracy of guidance even during these curvature transitions. Finally, the overall control scheme is implemented, and improvements with respect to previous guidance laws are demonstrated through full-scale experiments. 相似文献