全文获取类型
收费全文 | 1674篇 |
免费 | 78篇 |
国内免费 | 9篇 |
专业分类
化学 | 1169篇 |
晶体学 | 3篇 |
力学 | 28篇 |
数学 | 222篇 |
物理学 | 240篇 |
无线电 | 99篇 |
出版年
2023年 | 11篇 |
2022年 | 8篇 |
2021年 | 23篇 |
2020年 | 35篇 |
2019年 | 35篇 |
2018年 | 12篇 |
2017年 | 15篇 |
2016年 | 70篇 |
2015年 | 59篇 |
2014年 | 71篇 |
2013年 | 82篇 |
2012年 | 125篇 |
2011年 | 107篇 |
2010年 | 76篇 |
2009年 | 65篇 |
2008年 | 104篇 |
2007年 | 86篇 |
2006年 | 102篇 |
2005年 | 80篇 |
2004年 | 98篇 |
2003年 | 74篇 |
2002年 | 53篇 |
2001年 | 48篇 |
2000年 | 25篇 |
1999年 | 18篇 |
1998年 | 19篇 |
1997年 | 15篇 |
1996年 | 26篇 |
1995年 | 20篇 |
1994年 | 26篇 |
1993年 | 9篇 |
1992年 | 12篇 |
1991年 | 11篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 10篇 |
1985年 | 4篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1974年 | 10篇 |
1973年 | 11篇 |
1972年 | 10篇 |
1971年 | 5篇 |
1970年 | 4篇 |
排序方式: 共有1761条查询结果,搜索用时 31 毫秒
101.
A membrane-assisted solvent extraction (MASE) method is presented for the extraction of several non-ionic organophosphorus chemicals from wastewaters samples followed by LC-MS/MS determination. The method was developed for a variety of chlorinated phosphates (trichloroethyl, tichloropropyl) and non-chlorinated phosphates (triphenyl, tributyl) used as flame retardants and for plasticizers such as triethylhexyl and tris-butoxyethyl phosphate. Parameters such as extracting solvent, sample volume and ionic strength, extraction temperature and time were optimized. The final method provides good quantification limits (1-25 ng L(-1)) and linearity (R2>0.9978). Method precision was also good at high concentrations (5% mean RSD at the 500 ng L(-1) level) but decreased at lower concentrations (20% mean RSD at the 20 ng L(-1) level). MASE yields lower matrix effects than SPE in a successive LC-MS/MS analysis of these compounds, avoiding the need for standard addition for quantification. When applied to wastewater samples comparable results were obtained using either MASE with internal standard calibration or SPE with standard addition. 相似文献
102.
103.
Schupp PJ Charlton TS Taylor MW Kjelleberg S Steinberg PD 《Analytical and bioanalytical chemistry》2005,383(1):132-137
A challenge for understanding the role of bacterial cell–cell signalling in the environment is the detection of those signals,
which are often present in low (nmol L−1) concentrations. We describe here a simple purification method, solid-phase extraction (SPE), for increasing the sensitivity
of detection for one such group of signals, acyl homoserine lactones (AHLs), in environmental samples. Spiking of dried marine
sponge tissue (Stylinos sp.) with AHLs resulted in detection down to 0.01 ppm for 3-oxo-hexanoyl homoserine lactone (3-oxo C6-HSL) and 1 ppm for hexanoyl homoserine lactone (C6-HSL). Compared with liquid extraction methods use of SPE resulted in twofold and tenfold improvements in sensitivity, respectively. 相似文献
104.
105.
Malte Elson Johannes Breuer James D. Ivory Thorsten Quandt 《The Journal of communication》2014,64(3):521-542
Recent research has attempted to describe meaningful experiences with entertainment media that go beyond hedonic enjoyment. Most of this research focuses on noninteractive media, such as film and television. When applied to digital games, however, such research needs to account for not only the content of the medium, but also the unique dimensions of digital games that distinguish them from noninteractive media. Experiences with digital games are shaped by the game mechanics that define the users' interaction with game content, as well as by the opportunities for social interaction that many games offer. We argue that the complex interplay of these dimensions (narrative, mechanics, and context) facilitates or inhibits meaningful user experiences in ways that are unique to digital games. 相似文献
106.
107.
Instruments for surgical and dental application based on oscillatory mechanics submit unwanted vibrations to the operator’s hand. Frequently the weight of the instrument’s body is increased to dampen its vibration. Based on recent research regarding the optimization of granular damping we developed a prototype granular damper that attenuates the vibrations of an oscillatory saw twice as efficiently as a comparable solid mass. 相似文献
108.
109.
Samy Chammaa Dr. Bianca Sperl Anke G. Roth Aybike Yektaoglu Steffen Renner Dr. Thorsten Berg Prof. Dr. Christoph Arenz Prof. Dr. Athanassios Giannis Prof. Dr. Tudor I. Oprea Dr. Daniel Rauh Dr. Markus Kaiser Dr. Herbert Waldmann Prof. Dr. 《Angewandte Chemie (International ed. in English)》2010,49(21):3666-3670
110.
Frank Sottile Thorsten Theobald 《Transactions of the American Mathematical Society》2002,354(12):4815-4829
We show that for there are complex common tangent lines to general spheres in and that there is a choice of spheres with all common tangents real.