全文获取类型
收费全文 | 4572篇 |
免费 | 420篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 47篇 |
综合类 | 6篇 |
化学工业 | 1357篇 |
金属工艺 | 71篇 |
机械仪表 | 104篇 |
建筑科学 | 200篇 |
矿业工程 | 14篇 |
能源动力 | 115篇 |
轻工业 | 517篇 |
水利工程 | 33篇 |
石油天然气 | 12篇 |
无线电 | 490篇 |
一般工业技术 | 796篇 |
冶金工业 | 572篇 |
原子能技术 | 47篇 |
自动化技术 | 621篇 |
出版年
2022年 | 43篇 |
2021年 | 49篇 |
2020年 | 63篇 |
2019年 | 103篇 |
2018年 | 121篇 |
2017年 | 130篇 |
2016年 | 161篇 |
2015年 | 140篇 |
2014年 | 201篇 |
2013年 | 311篇 |
2012年 | 220篇 |
2011年 | 248篇 |
2010年 | 223篇 |
2009年 | 216篇 |
2008年 | 232篇 |
2007年 | 177篇 |
2006年 | 187篇 |
2005年 | 152篇 |
2004年 | 145篇 |
2003年 | 133篇 |
2002年 | 126篇 |
2001年 | 95篇 |
2000年 | 106篇 |
1999年 | 73篇 |
1998年 | 91篇 |
1997年 | 73篇 |
1996年 | 83篇 |
1995年 | 63篇 |
1994年 | 75篇 |
1993年 | 61篇 |
1992年 | 52篇 |
1991年 | 35篇 |
1990年 | 55篇 |
1989年 | 50篇 |
1988年 | 31篇 |
1987年 | 36篇 |
1986年 | 33篇 |
1985年 | 44篇 |
1984年 | 48篇 |
1983年 | 41篇 |
1982年 | 39篇 |
1981年 | 37篇 |
1980年 | 34篇 |
1979年 | 45篇 |
1978年 | 17篇 |
1977年 | 42篇 |
1976年 | 30篇 |
1975年 | 23篇 |
1974年 | 23篇 |
1973年 | 24篇 |
排序方式: 共有5002条查询结果,搜索用时 15 毫秒
11.
12.
In the first half of the 21st century, a redistribution of the energy data should occur, where nuclear will play a more important role, particularly as coal will become more and more costly to extract.On a worldwide basis, the unability of oil to be replaced in some areas like transportation, and the difficulty of developing countries to find substitutes for this energy source, could also lead developed countries to keep the energy resources for a better utilization, and give the countries which have no access to other resources, a possibility to develop.Thus, France has extensively enhanced nuclear energy for its electricity production, and, consequently, makes the necessary efforts for the knowledge of the whole fuel cycle. 相似文献
13.
Ockene Judith K.; Kristeller Jean; Pbert Lori; Hebert James R.; Luippold Rose; Goldberg Robert J.; Landon Joan; Kalan Kathryn 《Canadian Metallurgical Quarterly》1994,13(3):278
Patterns of smoking cessation using 6- and 12-mo follow-up data are reported for 1,261 primary care patients randomized to 3 physician-delivered smoking interventions: advice only (AO), counseling (CI), and counseling plus availability of nicotine-containing gum (CI?+?NCG). One-week point-prevalence cessation rates at 12 mo did not differ among the interventions: AO (15.2%), CI (12.9%) and CI?+?NCG (16.7%). However, maintained cessation rates (abstinent at both 6 and 12 mo) increased with intervention intensity: AO (6.0%), CI (7.8%), and CI?+?NCG (10.0%): Test of trend χ–2?=?5.06, p?=?.02. CI?+?NCG was significantly higher than AO (p?=?.02). The findings support the following conclusions: Brief physician delivered intervention with availability of nicotine-containing gum can have a beneficial long-term effect on smoking cessation, and cohort data as well as point-prevalence rates are important when assessing the long-term impact of lifestyle interventions. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
14.
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
15.
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
16.
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
17.
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
18.
19.
20.
Sarrazin Jean-Christophe; Giraudo Marie-Dominique; Pailhous Jean; Bootsma Reinoud J. 《Canadian Metallurgical Quarterly》2004,30(3):411
In 3 experiments, the authors studied the organization of spatiotemporal information in memory. Stimuli consisted of configurations of dots, presented sequentially. The stimuli were either proportional, with interdot distances corresponding to interdot durations, or not proportional, with interdol distances not corresponding to interdot durations. After a learning phase, participants reproduced the spatial (Experiment 1), temporal (Experiment 2), or spatial and temporal (Experiment 3) characteristics of the target 60 times in succession. In the nonproportional conditions, effects of variable interdot durations or distances on the reproduction of, respectively, constant distances (tau effect) or durations (kappa effect) were observed, whereas no such effects were observed when variable distances or durations were to be produced. Tau and kappa effects influenced the accuracy but not the variability of responses. The results are discussed in light of the distinction between properties of the stabilized mental image and the process of stabilization. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献