全文获取类型
收费全文 | 181520篇 |
免费 | 22215篇 |
国内免费 | 5379篇 |
专业分类
电工技术 | 7996篇 |
技术理论 | 11篇 |
综合类 | 8394篇 |
化学工业 | 40685篇 |
金属工艺 | 7321篇 |
机械仪表 | 8886篇 |
建筑科学 | 12037篇 |
矿业工程 | 3637篇 |
能源动力 | 5027篇 |
轻工业 | 16588篇 |
水利工程 | 2553篇 |
石油天然气 | 6875篇 |
武器工业 | 816篇 |
无线电 | 24119篇 |
一般工业技术 | 28586篇 |
冶金工业 | 10606篇 |
原子能技术 | 1619篇 |
自动化技术 | 23358篇 |
出版年
2024年 | 492篇 |
2023年 | 2011篇 |
2022年 | 3579篇 |
2021年 | 5085篇 |
2020年 | 4880篇 |
2019年 | 6045篇 |
2018年 | 6471篇 |
2017年 | 7203篇 |
2016年 | 7262篇 |
2015年 | 8365篇 |
2014年 | 9648篇 |
2013年 | 12619篇 |
2012年 | 10743篇 |
2011年 | 11237篇 |
2010年 | 10305篇 |
2009年 | 10102篇 |
2008年 | 9668篇 |
2007年 | 9145篇 |
2006年 | 9015篇 |
2005年 | 7897篇 |
2004年 | 6211篇 |
2003年 | 6013篇 |
2002年 | 6161篇 |
2001年 | 5573篇 |
2000年 | 4879篇 |
1999年 | 4602篇 |
1998年 | 4377篇 |
1997年 | 3559篇 |
1996年 | 3028篇 |
1995年 | 2431篇 |
1994年 | 1908篇 |
1993年 | 1622篇 |
1992年 | 1192篇 |
1991年 | 927篇 |
1990年 | 770篇 |
1989年 | 660篇 |
1988年 | 534篇 |
1987年 | 418篇 |
1986年 | 328篇 |
1985年 | 339篇 |
1984年 | 197篇 |
1983年 | 176篇 |
1982年 | 177篇 |
1981年 | 165篇 |
1980年 | 150篇 |
1979年 | 94篇 |
1978年 | 77篇 |
1977年 | 130篇 |
1976年 | 233篇 |
1973年 | 64篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
An experimental study of an optical burst switching network based on wavelength-selective optical switches 总被引:1,自引:0,他引:1
Li Xinwan Chen Jianping Wu Guiling Wang Hui Ye Ailun 《Communications Magazine, IEEE》2005,43(5):S3-10
In this article we report the system structure and test results of an experimental optical burst switching network with three edge router's and one core node. Wavelength-selective switches developed for this system and their characteristics are depicted. The implementation and performance of our new scheme for the just-in-time protocol are described. We also report experimental results of FTP and VOD services on this system. Some parameters, including traffic rate, average burst data length, and assembly time, are studied. 相似文献
102.
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
103.
ZHANG Liqing WU Xiaohua 《武汉理工大学学报(材料科学英文版)》2005,20(3):119-121
1IntroductionWuweizi is a traditional Chinese herb,usually usedto cure cough,asthma,neurasthenic,hepatitisetc.Theactive ingredients in wuweizi are5%-22%lignan,themain components of which include deoxyschizandrin,schizandrin andγ-Schizandrin.Forthe purpos… 相似文献
104.
Methylated-β-cyclodextrin (Me-β-CD) was used to complex the photoinitiator, 2,2-dimethoxy-2-phenyl acetophenone (DMPA), yielding a water-soluble host/guest complex. The comparative studies demonstrated that the Me-β-CD complexed DMPA exhibited a high photoreactivity identical to the uncomplexed DMPA, while the CD complex obviously influenced the products of primary photolysis of DMPA and the photopolymerization kinetics due to the steric effect of CD on the subsequent initiation reactions. The photopolymerization rate of acrylamide can be described by the equation: Rp=K[2a]0.62[M]1.37[I]0.5[Me-β-CD]0. The mechanism of polymerization was also discussed. 相似文献
105.
Gonzalo Martínez‐Barrera Enrique Vigueras‐Santiago Susana Hernndez‐Lpez Gonzalo Martínez‐Barrera Witold Brostow Carmina Menchaca‐Campos 《Polymer Engineering and Science》2005,45(10):1426-1431
Fiber reinforced concrete (FRC) contains fibers physically mixed with gravel, sand, cement, and water. So far, adequate mechanical performance of FRC has been obtained at high cost and using complex technologies; important here is the geometry and surface characteristics of the polymers. We have modified polymeric‐fiber surfaces by using gamma radiation. Irradiated polypropylene (PP) fibers were submitted to 0, 5, 10, 50, and 100 kGy of gamma irradiation dosages. First, tensile strength of PP fibers was evaluated, and then fibers blended at 0, 1.0, 1.5, and 2.0% in volume with Portland cement, gravel, sand, and water. The highest values of compressive strength were obtained with irradiated‐fibers at 10 kGy and 1.5% in volume of fiber. The result is 101 MPa, as compared to 35 MPa for simple concrete without fibers. POLYM. ENG. SCI., 45:1426–1431, 2005. © 2005 Society of Plastics Engineers 相似文献
106.
Magnus Rnning Florian Huber Hilde Meland Hilde Venvik De Chen Anders Holmen 《Catalysis Today》2005,100(3-4):249-254
In order to investigate the effect of cerium oxide on Cu–Zn-based mixed-oxide catalysts four catalyst samples were characterized by means of XRD, in situ XANES and thermogravimetric analysis. The activity of the catalyst samples was tested for the forward water–gas shift reaction. Cerium oxide was found to increase the crystallinity of the ZnO phase indicating a segregation of the Cu and ZnO phases. The TOF of the water–gas shift reaction based on chemisorption data was found to be independent of composition and preparation conditions of the four catalyst samples. In contrast, the catalyst stability depends on composition and preparation conditions. Cerium oxide impregnated before calcination of the hydrotalcite-based Cu–Zn precursors leads to a more stable water–gas shift catalyst. 相似文献
107.
On sorting triangles in a delaunay tessellation 总被引:1,自引:0,他引:1
In a two-dimensional Delaunay-triangulated domain, there exists a partial ordering of the triangles (with respect to a vertex) that is consistent with the two-dimensional visibility of the triangles from that vertex. An equivalent statement is that a polygon that is star-shaped with respect to a given vertex can be extended, one triangle at a time, until it includes the entire domain. Arbitrary planar triangulations do not possess this useful property which allows incremental processing of the triangles.This work was partially supported by the National Science Foundation's US-Italy Collaborative Research Program under Grant INT-8714578 and Information, Robotics, and Intelligent Research Grant IRI-8704781. 相似文献
108.
109.
110.
Xue‐Bing Zhao Lei Wang De‐Hua Liu 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(6):950-956
Previous work has shown that the enzymatic hydrolysis of sugarcane bagasse could be greatly enhanced by peracetic acid (PAA) pretreatment. There are several factors affecting the enzymatic digestibility of the biomass, including lignin and hemicelluloses content, cellulose crystallinity, acetyl group content, accessible surface area and so on. The objective of this work is to analyze the mechanism of the enhancement of enzymatic digestibility caused by PAA pretreatment. Delignification resulted in an increase of the surface area and reduction of the irreversible absorption of cellulase, which helped to increase the enzymatic digestibility. The Fourier transform infrared (FTIR) spectrum showed that the absorption peaks of aromatic skeletal vibrations were weakened or disappeared after PAA pretreatment. However, the infrared crystallization index (N.O'KI) was increased. X‐ray diffraction (XRD) analysis indicated that the crystallinity of PAA‐treated samples was increased owing to the partial removal of amorphous lignin and hemicelluloses and probable physical change of cellulose. The effect of acetyl group content on enzymatic digestibility is negligible compared with the degree of delignification and crystallinity. The results indicate that enhancement of enzymatic digestibility of sugarcane bagasse by PAA pretreatment is achieved mainly by delignification and an increase in the surface area and exposure of cellulose fibers. Copyright © 2008 Society of Chemical Industry 相似文献