全文获取类型
收费全文 | 30227篇 |
免费 | 3171篇 |
国内免费 | 1832篇 |
专业分类
电工技术 | 1697篇 |
技术理论 | 1篇 |
综合类 | 2181篇 |
化学工业 | 4670篇 |
金属工艺 | 1569篇 |
机械仪表 | 1728篇 |
建筑科学 | 2269篇 |
矿业工程 | 736篇 |
能源动力 | 901篇 |
轻工业 | 2793篇 |
水利工程 | 730篇 |
石油天然气 | 1168篇 |
武器工业 | 269篇 |
无线电 | 4062篇 |
一般工业技术 | 3711篇 |
冶金工业 | 1504篇 |
原子能技术 | 395篇 |
自动化技术 | 4846篇 |
出版年
2024年 | 147篇 |
2023年 | 432篇 |
2022年 | 892篇 |
2021年 | 1217篇 |
2020年 | 959篇 |
2019年 | 800篇 |
2018年 | 948篇 |
2017年 | 1008篇 |
2016年 | 968篇 |
2015年 | 1207篇 |
2014年 | 1504篇 |
2013年 | 2027篇 |
2012年 | 2125篇 |
2011年 | 2147篇 |
2010年 | 2056篇 |
2009年 | 2030篇 |
2008年 | 1957篇 |
2007年 | 1954篇 |
2006年 | 1725篇 |
2005年 | 1374篇 |
2004年 | 1128篇 |
2003年 | 1082篇 |
2002年 | 1175篇 |
2001年 | 1042篇 |
2000年 | 632篇 |
1999年 | 465篇 |
1998年 | 425篇 |
1997年 | 350篇 |
1996年 | 277篇 |
1995年 | 212篇 |
1994年 | 173篇 |
1993年 | 123篇 |
1992年 | 100篇 |
1991年 | 75篇 |
1990年 | 59篇 |
1989年 | 81篇 |
1988年 | 44篇 |
1987年 | 44篇 |
1986年 | 49篇 |
1985年 | 39篇 |
1984年 | 29篇 |
1983年 | 20篇 |
1982年 | 14篇 |
1981年 | 15篇 |
1980年 | 13篇 |
1979年 | 10篇 |
1978年 | 9篇 |
1977年 | 15篇 |
1976年 | 12篇 |
1959年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Jeong Ho Moon Hak Soo Han Yong Gun Shul Do Hoon Jang Muyng Do Ro Du Suk Yun 《Progress in Organic Coatings》2007
This study relates to the development of coatings for optical discs in high-density digital versatile disc systems (HD-DVD or blue lay disk) that use a high numerical aperture of 0.85 at 405 nm wavelength and have a protective top layer over a primer layer for protection against damage and dust. Ultraviolet-curable raw materials of two acrylic monofunctional monomers ( isobornylacrylate, IBA and tetrahydrofurfurylacrylate, THFA) and two kinds of urethaneacrylate oligomers (OUMD and OUME) have been easily mixed with photoinitiators. Curing rate of these materials was characterized by FT-IR. In case of top coats, VTES (vinyltriethoxysilane) and acrylic acid were added to enhance the abrasion resistance. These two kinds of UV-curable resinous materials having no solvent were synthesized and investigated as means for making a blue ray disk having good optical and mechanical properties. In addition, dynamic characteristics including reflectivity, fluctuation of RF signal and noise level were also investigated. 相似文献
52.
Yiping Wang Na Chen Binfeng Yun Yiping Cui 《Photonics Technology Letters, IEEE》2007,19(16):1242-1244
A measurement method has been developed to determine the full-field deformation of a simply supported plane plate under transverse load. The method utilizes strain information provided by a set of four fiber Bragg grating sensors mounted on the plate in a way that all sensors measure strains along one certain direction. The sensors were interrogated using a wavelength swept fiber laser. Utilizing the strain information and the first four terms of Navier solution of simply supported rectangular plate, the necessary parameters for determining the deflection could be computed. By substituting the values of x- and -y- coordinates of each position on the rectangle plate, the full-field deformation information can be obtained. Single-point loading tests were experimentally performed to verify the accuracy of the method. 相似文献
53.
国内主要参展商
1.益阳橡机
益阳橡胶塑料机械集团有限公司在本次展会上,推出了一款GE-5实验室用密炼机,容积5升,啮合型转子,用于橡胶制品、白炭黑、特种胶的混炼. 相似文献
54.
55.
不同粒度松散煤体的氧扩散特性实验研究 总被引:1,自引:0,他引:1
以自行研制的煤对氧扩散特性测试装置为实验手段,在常温环境条件下测试了不同粒度松散煤体对氧的自由扩散特性.实验结果表明:煤样粒度的变化对取气腔氧浓度流出曲线的影响表现出2个极限值,煤样粒度在20~100目之间时,取气腔氧气浓度梯度随煤样粒度的增大而增大;当煤样粒度<20目或>100目时,煤样粒度的再变化对氧浓度流出曲线的影响则微乎其微;取气腔氧浓度曲线流形基本符合指数曲线的变化规律. 相似文献
56.
57.
ABSTRACT: Grain of the soft white wheat cultivar Harus was harvested weekly from anthesis to maturity and fructooligosaccharides (FOS) contents were determined by reversed-phase high-performance liquid chromatography. Tests were carried out to determine the effect of adding immature wheat meal to a base flour of cultivar Russ (hard red spring) on the quality characteristics of bread. FOS content was also analyzed in baked bread, and the effect of transglutaminase in improving bread quality was examined. Marked decreases in FOS contents, such as 1-kestose and nystose, were observed with grain maturation. The overall quality of bread appeared to be acceptable, and the added FOS were retained after baking. 相似文献
58.
Academically selective schools are intended to affect academic self-concept positively, but theoretical and empirical research demonstrates that the effects are negative. The big-fish--little-pond effect (BFLPE), an application of social comparison theory to educational settings, posits that a student will have a lower academic self-concept in an academically selective school than in a nonselective school. This study, the largest cross-cultural study of the BFLPE ever undertaken, tested theoretical predictions for nationally representative samples of approximately 4,000 15-year-olds from each of 26 countries (N=103,558) who completed the same self-concept instrument and achievement tests. Consistent with the BFLPE, the effects of school-average achievement were negative in all 26 countries (M beta=-.20, SD=.08), demonstrating the BFLPE's cross-cultural generalizability. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
59.
Si-Woong Lee Jae Gark Choi Byoung-Ju Yun 《Electronics letters》2003,39(9):712-714
An adaptive contour smoothing algorithm designed as a preprocessor for shape coders is presented. In the method, the degree of the adaptive smoothing is controlled based on the significance of each contour point, which is quantified according to inter-region contrast in an intensity image. The actual smoothing consists of an expansion operator and a thinning algorithm. 相似文献
60.
M Eberstadt B Huang Z Chen RP Meadows SC Ng L Zheng MJ Lenardo SW Fesik 《Canadian Metallurgical Quarterly》1998,392(6679):941-945
When activated, membrane-bound receptors for Fas and tumour-necrosis factor initiate programmed cell death by recruiting the death domain of the adaptor protein FADD to the membrane. FADD then activates caspase 8 (also known as FLICE or MACH) through an interaction between the death-effector domains of FADD and caspase 8. This ultimately leads to the apoptotic response. Death-effector domains and homologous protein modules known as caspase-recruitment domains have been found in several proteins and are important regulators of caspase (FLICE) activity and of apoptosis. Here we describe the solution structure of a soluble, biologically active mutant of the FADD death-effector domain. The structure consists of six antiparallel, amphipathic alpha-helices and resembles the overall fold of the death domains of Fas and p75. Despite this structural similarity, mutations that inhibit protein-protein interactions involving the Fas death domain have no effect when introduced into the FADD death-effector domain. Instead, a hydrophobic region of the FADD death-effector domain that is not present in the death domains is vital for binding to FLICE and for apoptotic activity. 相似文献