全文获取类型
收费全文 | 217424篇 |
免费 | 17637篇 |
国内免费 | 9205篇 |
专业分类
电工技术 | 12694篇 |
技术理论 | 13篇 |
综合类 | 14017篇 |
化学工业 | 36532篇 |
金属工艺 | 12606篇 |
机械仪表 | 14234篇 |
建筑科学 | 17763篇 |
矿业工程 | 6834篇 |
能源动力 | 6379篇 |
轻工业 | 14162篇 |
水利工程 | 3806篇 |
石油天然气 | 14509篇 |
武器工业 | 1719篇 |
无线电 | 23996篇 |
一般工业技术 | 25421篇 |
冶金工业 | 10445篇 |
原子能技术 | 2271篇 |
自动化技术 | 26865篇 |
出版年
2024年 | 973篇 |
2023年 | 3684篇 |
2022年 | 6492篇 |
2021年 | 8973篇 |
2020年 | 6892篇 |
2019年 | 5647篇 |
2018年 | 6185篇 |
2017年 | 7093篇 |
2016年 | 6245篇 |
2015年 | 8680篇 |
2014年 | 10575篇 |
2013年 | 12541篇 |
2012年 | 13666篇 |
2011年 | 14739篇 |
2010年 | 12775篇 |
2009年 | 12130篇 |
2008年 | 11800篇 |
2007年 | 11187篇 |
2006年 | 11722篇 |
2005年 | 10253篇 |
2004年 | 6823篇 |
2003年 | 6213篇 |
2002年 | 5861篇 |
2001年 | 5332篇 |
2000年 | 5361篇 |
1999年 | 5843篇 |
1998年 | 4813篇 |
1997年 | 4051篇 |
1996年 | 3825篇 |
1995年 | 3255篇 |
1994年 | 2665篇 |
1993年 | 1817篇 |
1992年 | 1512篇 |
1991年 | 1124篇 |
1990年 | 845篇 |
1989年 | 739篇 |
1988年 | 594篇 |
1987年 | 395篇 |
1986年 | 284篇 |
1985年 | 167篇 |
1984年 | 117篇 |
1983年 | 97篇 |
1982年 | 102篇 |
1981年 | 71篇 |
1980年 | 60篇 |
1979年 | 27篇 |
1978年 | 4篇 |
1976年 | 5篇 |
1965年 | 3篇 |
1959年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
A novel series of temperature‐sensitive poly[(N‐isopropylacrylamide)‐co‐(ethyl methacrylate)] (p(NIPAM‐co‐EMA)) microgels was prepared by the surfactant‐free radical polymerization of N‐isopropylacrylamide (NIPAM) with ethyl methacrylate (EMA). The shape, size dispersity and volume‐phase transition behavior of the microgels were investigated by transmission electron microscopy (TEM), ultraviolet–visible (UV–Vis) spectroscopy, dynamic light scattering (DLS) and differential scanning calorimetry (DSC). The transmission electron micrographs and DLS results showed that microgels with narrow distributions were prepared. It was shown from UV–Vis, DLS and DSC measurements that the volume‐phase transition temperature (VPTT) of the p(NIPAM‐co‐EMA) microgels decreased with increasing incorporation of EMA, but the temperature‐sensitivity was impaired when more EMA was incorporated, causing the volume‐phase transition of the microgels to become more continuous. It is noteworthy that incorporation of moderate amounts of EMA could not only lower the VPTT but also enhance the temperature‐sensitivity of the microgels. The reason for this phenomenon could be attributed to changes in the complicated interactions between the various molecules. Copyright © 2004 Society of Chemical Industry 相似文献
62.
Shaofeng Wang Jianwei Xu Yuejin Tong Lin Wang Chaobin He 《Polymer International》2005,54(9):1268-1274
A novel cholesterol‐imprinted polymer (CMIP‐H) was prepared by a hybrid method of covalent imprinting and non‐covalent imprinting. This approach involves the copolymerization of a template‐containing monomer, cholesteryl 2‐hydroxyethyl methacrylate carbonate, and a cross‐linker, followed by hydrolysis to afford a flexible guest‐binding site accompanied with the easy and efficient removal of a ‘sacrificial spacer’. The effect of solvent on the binding capacity of CMIP‐H towards cholesterol was studied, indicating that a good binding capacity towards cholesterol could be achieved in a less‐polar solvent. The binding experiments of CMIP‐H towards a series of structural analogues of cholesterol, including cholesterol acetate, progesterone and stigmasterol, were carried out in hexane. The results showed that CMIP‐H almost did not bind cholesterol acetate at all because the hydrogen‐bonding site is blocked. It exhibited a similar binding towards both cholesterol and stigmasterol, but much higher binding towards progesterone. Copyright © 2005 Society of Chemical Industry 相似文献
63.
彩色地震剖面显示是地震剖面显示技术中较为先进的一种显示方式.它具有常规黑白显示剖面所无法比拟的优点.尤其是在一些特殊处理显示的剖面(诸如三瞬剖面、虚速度测井剖面以及烃类显示剖面)中,这些剖面给人以清晰直观和一目了然的感觉.但是,目前彩色剖面在国内尚未得到普遍地应用,其原因之一是由于彩色显示处理要求计算机具有大的内存容量和高速运算等方面的性能,所以一般都是在大中型计算机上处理.而小型计算机由于内存容量和运算速度等面存在着不足,所以难以运行象现今国内所使用的UNIRAS这样庞大的系统.笔者在研究了UNIRAS系统的实现原理后,另辟蹊径,在只有32k内存容量又无虚拟存贮管理系统的TEMPUSⅡ小型计算机上,采用光栅处理技术,实现了地震剖面彩色显示,并取得了令人满意的结果. 相似文献
64.
65.
在第一部分综合讨论的基础上对甘三酯立体专一分析方法作了初步探讨。以液体油(菜油)及固体脂(猪脂)为基质,系统地研究了这一分析方法,取得了经验并补充了一些具体验证方法。分析液体油的结果与文献数据相一致,分析猪脂的结果欠佳,还存在一些问题需待进一步研究。 相似文献
66.
67.
68.
69.
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
70.
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