全文获取类型
收费全文 | 280028篇 |
免费 | 6058篇 |
国内免费 | 2786篇 |
专业分类
电工技术 | 6620篇 |
技术理论 | 8篇 |
综合类 | 2480篇 |
化学工业 | 44886篇 |
金属工艺 | 12053篇 |
机械仪表 | 8999篇 |
建筑科学 | 8139篇 |
矿业工程 | 2133篇 |
能源动力 | 6108篇 |
轻工业 | 27110篇 |
水利工程 | 3204篇 |
石油天然气 | 6879篇 |
武器工业 | 414篇 |
无线电 | 30510篇 |
一般工业技术 | 51545篇 |
冶金工业 | 48115篇 |
原子能技术 | 5810篇 |
自动化技术 | 23859篇 |
出版年
2022年 | 2126篇 |
2021年 | 3382篇 |
2020年 | 2328篇 |
2019年 | 2632篇 |
2018年 | 3912篇 |
2017年 | 3922篇 |
2016年 | 4244篇 |
2015年 | 3560篇 |
2014年 | 5504篇 |
2013年 | 12450篇 |
2012年 | 8778篇 |
2011年 | 11297篇 |
2010年 | 9180篇 |
2009年 | 9672篇 |
2008年 | 10546篇 |
2007年 | 10583篇 |
2006年 | 9403篇 |
2005年 | 8277篇 |
2004年 | 7399篇 |
2003年 | 6768篇 |
2002年 | 6803篇 |
2001年 | 6812篇 |
2000年 | 6383篇 |
1999年 | 6337篇 |
1998年 | 13227篇 |
1997年 | 9882篇 |
1996年 | 7611篇 |
1995年 | 5807篇 |
1994年 | 5322篇 |
1993年 | 5183篇 |
1992年 | 4123篇 |
1991年 | 3885篇 |
1990年 | 3988篇 |
1989年 | 3891篇 |
1988年 | 3625篇 |
1987年 | 3061篇 |
1986年 | 3091篇 |
1985年 | 3434篇 |
1984年 | 3346篇 |
1983年 | 3102篇 |
1982年 | 2719篇 |
1981年 | 2913篇 |
1980年 | 2661篇 |
1979年 | 2847篇 |
1978年 | 2746篇 |
1977年 | 2857篇 |
1976年 | 3701篇 |
1975年 | 2463篇 |
1974年 | 2298篇 |
1973年 | 2332篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Sarto M.S. Voti R.L. Sarto F. Larciprete M.C. 《Electromagnetic Compatibility, IEEE Transactions on》2005,47(3):602-611
New nanolayered coatings are designed and deposited on flexible plastic substrate having the thickness of 100 /spl mu/m, in order to realize lightweight ultrathin transparent shielding foils. The structure of the coating is optimized considering three figures of merit: the average transmittance in the visible range for normal incidence, the normalized average transmittance for oblique incidence at 550 nm, and the transmittance quality factor. The nanotechnology exploited for the deposition of the transparent metals is the dual ion beam sputtering. Tests of durability, optical transmission, and shielding effectiveness demonstrate that the film has a high adhesion under mechanical solicitation, high resistance against aging, peak transmittance in the visible range higher than 70%, omnidirectional properties in the range 0/spl deg/-60/spl deg/, and shielding effectiveness of 40 dB up to 6 GHz. 相似文献
62.
63.
R. Morena P. E. Lockwood L. Evans C. W. Fairhurst 《Journal of the American Ceramic Society》1986,69(4):75-C-
The effect on mechanical behavior of ZrO2 additions to a dental porcelain was investigated. The ZrO2 was introduced into the glassy matrix phase of the porcelain by refritting the all-glass porcelain constituent. X-ray diffraction indicated that a sizeable fraction of the ZrO2 was retained in the tetragonal form after the porcelain was fired. Zirconia additions to the porcelain produced substantial improvements in fracture toughness, strength, and thermal shock resistance. 相似文献
64.
Indoor body-area channel model for narrowband communications 总被引:1,自引:0,他引:1
Fort A. Desset C. Wambacq P. Biesen L.V. 《Microwaves, Antennas & Propagation, IET》2007,1(6):1197-1203
Using wireless sensors placed on a person to continuously monitor health information is a promising new application. At the same time, new low-power wireless standards such as Bluetooth and Zigbee have been proposed for short range, low data-rate communication matching the requirements of these bio-medical applications. However, there are currently few measurements or models describing propagation around the body. To address this problem, electromagnetic waves near the torso are measured and a statistical model is derived for communication in the 915 MHz and 2.45 GHz industrial, scientific and medical bands associated with Zigbee and Bluetooth. Measurement setup and statistical analysis are described. 相似文献
65.
R. Oliva A. L. Gemal A. W. N brega A. C. P. Araú jo 《Food Additives & Contaminants》2003,20(8):758-763
The structure of the recently introduced Brazilian government programme for monitoring pesticide residues in six major agricultural products is described. Residues found from the analysis of samples of tomatoes and strawberries are discussed in detail. The much greater frequency of detection of pesticide residues, many of which are not approved for use in Brazil, in produce being sold on the domestic market, as opposed to that produced for export, is of major concern. It is perceived that this new monitoring programme will become permanent and be used to underpin enforcement actions that will need to be taken to reduce the numbers of incidents of illegal residues occurring, particularly in fresh fruits and vegetables. 相似文献
66.
67.
68.
S. V. Yakubovskaya L. V. Kul'bitskaya N. L. Budeiko A. A. Korbit 《Inorganic Materials》2004,40(3):221-226
The effect of the composition of sensitizing–activating solutions on the activation efficiency and the chemical coppering of diamond powders is studied. The results demonstrate that stabilizing additives improve the stability of the solutions, influence the average coppering rate, and play a key role in determining the morphology and quality of the resultant coatings. The most effective stabilizing additive is synthamid-10, which ensures the deposition of high-quality copper coatings. 相似文献
69.
O Bernard B Chachuat A Hélias B Le Dantec B Sialve J-P Steyer L Lardon P Neveu S Lambert J Gallop M Dixon P Ratini A Quintabà S Frattesi J M Lema E Roca G Ruiz J Rodriguez A Franco P Vanrolleghem U Zaher D J W De Pauw K De Neve K Lievens D Dochaine O Schoefs H Fibrianto R Farina V Alcaraz Gonzalez V Gonzalez Alvarez P Lemaire J A Martinez F Esandi O Duclaud J F Lavigne 《Water science and technology》2005,52(1-2):457-464
The TELEMAC project brings new methodologies from the Information and Science Technologies field to the world of water treatment. TELEMAC offers an advanced remote management system which adapts to most of the anaerobic wastewater treatment plants that do not benefit from a local expert in wastewater treatment. The TELEMAC system takes advantage of new sensors to better monitor the process dynamics and to run automatic controllers that stabilise the treatment plant, meet the depollution requirements and provide a biogas quality suitable for cogeneration. If the automatic system detects a failure which cannot be solved automatically or locally by a technician, then an expert from the TELEMAC Control Centre is contacted via the internet and manages the problem. 相似文献
70.
Polystyrene packaging material taint was sensorily evaluated in cocoa powder for drinks and chocolate flakes using short-cut signal detection measures on differences between control and test samples and on recognition of styrene. No differences were observed in cocoa powder for drinks and plain chocolate flakes treated with 0.5 dm2 polystyrene of 1 mm thickness. However, differences were detected in milk chocolate flakes and plain chocolate flakes, which were in contact with a larger area or thicker polystyrene packaging material. The latter results were confirmed by the styrene recognition test, so polystyrene is a potential source of off-flavour for chocolate products. The amount of residual styrene in the polystyrene used was about 320 ppm, while the amounts of styrene ranged from 7 to 132 ppb in cocoa drinks and from 414 to 1447 ppb in chocolate flakes. 相似文献