全文获取类型
收费全文 | 240704篇 |
免费 | 15224篇 |
国内免费 | 7639篇 |
专业分类
电工技术 | 11020篇 |
技术理论 | 9篇 |
综合类 | 13124篇 |
化学工业 | 37730篇 |
金属工艺 | 13481篇 |
机械仪表 | 12864篇 |
建筑科学 | 15101篇 |
矿业工程 | 5213篇 |
能源动力 | 5699篇 |
轻工业 | 14778篇 |
水利工程 | 4165篇 |
石油天然气 | 9755篇 |
武器工业 | 1352篇 |
无线电 | 27283篇 |
一般工业技术 | 34216篇 |
冶金工业 | 9803篇 |
原子能技术 | 2326篇 |
自动化技术 | 45648篇 |
出版年
2024年 | 797篇 |
2023年 | 2802篇 |
2022年 | 5163篇 |
2021年 | 6986篇 |
2020年 | 5371篇 |
2019年 | 4443篇 |
2018年 | 18599篇 |
2017年 | 18257篇 |
2016年 | 14201篇 |
2015年 | 7062篇 |
2014年 | 8197篇 |
2013年 | 9452篇 |
2012年 | 13265篇 |
2011年 | 20025篇 |
2010年 | 17653篇 |
2009年 | 14557篇 |
2008年 | 15584篇 |
2007年 | 16044篇 |
2006年 | 8767篇 |
2005年 | 8672篇 |
2004年 | 6206篇 |
2003年 | 5706篇 |
2002年 | 4982篇 |
2001年 | 4130篇 |
2000年 | 4072篇 |
1999年 | 3995篇 |
1998年 | 3190篇 |
1997年 | 2758篇 |
1996年 | 2571篇 |
1995年 | 2118篇 |
1994年 | 1752篇 |
1993年 | 1267篇 |
1992年 | 1062篇 |
1991年 | 805篇 |
1990年 | 571篇 |
1989年 | 515篇 |
1988年 | 421篇 |
1987年 | 287篇 |
1986年 | 193篇 |
1985年 | 113篇 |
1984年 | 83篇 |
1983年 | 65篇 |
1982年 | 76篇 |
1981年 | 49篇 |
1980年 | 47篇 |
1968年 | 43篇 |
1965年 | 47篇 |
1959年 | 45篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Hideo Sawada Hiroshi Kakehi Masashi Koizumi Yoshihiro Katoh Masashi Miura 《Journal of Materials Science》2007,42(17):7147-7153
Fluoroalkyl end-capped N-(1,1-dimethyl-3-oxobutyl)acrylamide oligomer [RF-(DOBAA)
n
-RF] reacted with tetraethoxysilane (TEOS) and silica nanoparticles in the presence of low-molecular weight biocides such as
hibitane, hinokitiol, and hinokioil under alkaline conditions to afford RF-(DOBAA)
n
-RF/silica nanocomposites-encapsulated these biocides in excellent to moderate isolated yields. Fluoroalkyl end-capped N,N-dimethylacrylamide oligomer [RF-(DMAA)
n
-RF] and acrylic acid oligomer [RF-(ACA)
n
-RF]/silica nanocomposites-encapsulated hibitane were obtained under similar conditions. Dynamic light scattering measurements
showed that the size of these fluorinated nanocomposites-encapsulated biocides thus obtained is nanometer size-controlled.
Additionally, these fluorinated nanocomposites were shown to have a good dispersibility and stability in methanol and water.
Of particular interest, these fluorinated nanocomposites-encapsulated biocides were found to have a good antibacterial activity
against Staphylococcus aureus, and these nanocomposites were applied to the surface modification of traditional organic polymers such as poly(methyl methacrylate). 相似文献
142.
143.
144.
Mamiko Hori Cécile Pagnoux Jean-François Baumard Masayuki Nogami 《Journal of Materials Science》2007,42(1):80-86
A new method is proposed to produce gold nanoparticles (GNP) by in situ reduction of a gold salt dissolved in water. The reducing
agent used is Tiron instead of the citrate anion most often mentioned in literature. The influence of various parameters has
been investigated, such as the content of Tiron with respect to that of the precursor of gold HAuCl4, or the initial pH of the solution after mixing of reactants. It is shown that Tiron also exerts a positive influence as
a dispersant, which impedes agglomeration of gold nanoparticles. The typical average size of GNP synthesized in the present
work is close to 7 nm. 相似文献
145.
146.
147.
2-环戊基环戊酮香料的制备与应用 总被引:2,自引:0,他引:2
以尼龙酸副产物2-亚环戊基环戊酮为原料,液体镍为催化剂,催化加氢制得了2-环戊基环戊酮。经元素分析、GCMS、IR、^1HNMR、^13C NMR检测,认为结构正确,色谱纯度大于99.9%。大鼠口服LD50雄性5381.5mg/kg,雌性5087.5mg/kg。具有留兰香样的香气,可用作食用和日用香料。 相似文献
148.
Visual evaluation experiments of color discrimination threshold and suprathreshold color‐difference comparison were carried out using CRT colors based on the psychophysical methods of interleaved staircase and constant stimuli, respectively. A large set of experimental data was generated ranged from threshold to large suprathreshold color difference at the five CIE color centers. The visual data were analyzed in detail for every observer at each visual scale to show the effect of color‐difference magnitude on the observer precision. The chromaticity ellipses from this study were compared with four previous published data, of CRT colors by Cui and Luo, and of surface colors by RIT‐DuPont, Cheung and Rigg, and Guan and Luo, to report the reproducibility of this kind of experiment using CRT colors and the variations between CRT and surface data, respectively. The present threshold data were also compared against the different suprathreshold data to show the effect of color‐difference scales. The visual results were further used to test the three advance color‐difference formulae, CMC, CIE94, and CIEDE2000, together with the basic CIELAB equation. In their original forms or with optimized KL values, the CIEDE2000 outperformed others, followed by CMC, and with the CIELAB and CIE94 the poorest for predicting the combined dataset of all color centers in the present study. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 198–208, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20106 相似文献
149.
CuMgAl类水滑石的制备和表征 总被引:5,自引:0,他引:5
用盐-碱制备法合成了CuMgAl三元类水滑石化合物。探讨了原料配比、合成方式、水热处理温度和时间对合成过程的影响,筛选出合成HTLcs的适宜条件,并对HTLcs结构的热稳定性进行初步研究。结果表明,制备HTLcs主要取决于pH值,同时由于Cu2+的姜-太勒效应,合成结构单一的CuMgAl类水滑石要求原料配比中n(Cu)∶n(Mg)不得超过1.0,CuMgAl-HTLcs热稳定性较差,300℃焙烧2h结构破坏,600℃开始烧结,在300~500℃之间,随焙烧温度提高所得复合氧化物比表面积增大,最高可达200 m2/g。 相似文献
150.