全文获取类型
收费全文 | 2523篇 |
免费 | 65篇 |
国内免费 | 8篇 |
专业分类
化学 | 1722篇 |
晶体学 | 8篇 |
力学 | 32篇 |
数学 | 565篇 |
物理学 | 269篇 |
出版年
2020年 | 45篇 |
2019年 | 29篇 |
2018年 | 17篇 |
2017年 | 25篇 |
2016年 | 42篇 |
2015年 | 68篇 |
2014年 | 52篇 |
2013年 | 92篇 |
2012年 | 93篇 |
2011年 | 99篇 |
2010年 | 75篇 |
2009年 | 58篇 |
2008年 | 119篇 |
2007年 | 110篇 |
2006年 | 95篇 |
2005年 | 102篇 |
2004年 | 79篇 |
2003年 | 63篇 |
2002年 | 50篇 |
2001年 | 22篇 |
2000年 | 32篇 |
1999年 | 25篇 |
1998年 | 30篇 |
1997年 | 22篇 |
1996年 | 22篇 |
1995年 | 26篇 |
1994年 | 27篇 |
1993年 | 35篇 |
1992年 | 28篇 |
1991年 | 18篇 |
1989年 | 25篇 |
1988年 | 30篇 |
1987年 | 30篇 |
1985年 | 33篇 |
1984年 | 46篇 |
1983年 | 23篇 |
1982年 | 19篇 |
1981年 | 31篇 |
1980年 | 36篇 |
1979年 | 22篇 |
1978年 | 21篇 |
1977年 | 22篇 |
1976年 | 22篇 |
1975年 | 23篇 |
1974年 | 25篇 |
1967年 | 16篇 |
1966年 | 16篇 |
1965年 | 16篇 |
1964年 | 16篇 |
1956年 | 24篇 |
排序方式: 共有2596条查询结果,搜索用时 250 毫秒
111.
112.
Ondřej Zvěřina Pavel Coufalík Josef Komárek Petr Gadas Jiřina Sysalová 《Chemical Papers》2014,68(2):197-202
An analysis of suspended particulate matter, with an emphasis on the Hg chemical forms, is presented. Dust samples originating from an area highly affected by traffic pollution in the city of Prague (Czech Republic) were sampled over a period of three years from air-conditioner filters and fractioned by size. The samples were morphologically characterised by scanning electron microscopy. The main method used for the analysis of constituent mercury compounds was sequential extraction by leaching solutions in combination with thermal desorption. The total mercury content ranged from 0.37 mg kg?1 to 0.82 mg kg?1. It emerged that the mercury was distributed in a wide spectrum of forms, and various trends in the distribution of these forms among the different size classes were observed. The fraction leached by nitric acid (consisting of elemental and complex-bound mercury) was the main constituent of total mercury. The highest content of this fraction was observed in the finest particle size class. The heterogeneity of morphology of the material increased with the size fraction. 相似文献
113.
114.
ABSTRACT: BACKGROUND: Archerfish show very short behavioural latencies in response to falling prey. This raises the question, which response parameters of retinal ganglion cells to moving stimuli are best suited for fast coding of stimulus speed and direction. RESULTS: We compared stimulus reconstruction quality based on the ganglion cell response parameters latency, first interspike interval, and rate. For stimulus reconstruction of moving stimuli using latency was superior to using the other stimulus parameters. This was true for absolute latency, with respect to stimulus onset, as well as for relative latency, with respect to population response onset. Iteratively increasing the number of cells used for reconstruction decreased the calculated error close to zero. CONCLUSIONS: Latency is the fastest response parameter available to the brain. Therefore, latency coding is best suited for high speed coding of moving objects. The quantitative data of this study are in good accordance with previously published behavioural response latencies. 相似文献
115.
116.
117.
118.
Josef Schurz Gayyur Erk Walter Schempp Volker Ribitsch 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(13-14):1673-1692
Polymers with electrically charged groups exhibit a zeta potential when in contact with electrolyte solutions in water. This can be measured with solid polymers as fibers, foils, or granulates. The method of streaming potential/streaming current allows the determination of the carboxyl content of cellulose grafted with poly-(acrylic acid). Since zeta-potential measurements concern the surface of the sample, the method yields information on the type of grafting; i.e., whether it takes place mainly on the surface or throughout the bulk. By measuring the pH dependence of the zeta potential it is possible to obtain the pK value of the charged groups. The significance of zeta potential as an analytical tool is emphasized. 相似文献
119.
Martin Kleparnik Marie Tomandlova Zdenek Glatz Josef Tomandl 《Journal of separation science》2013,36(23):3696-3701
A new HPLC method was developed and validated for the determination of asymmetric and symmetric dimethylarginines and l ‐arginine in human plasma. After SPE and evaporation of the eluate, the samples were derivatised with an o‐phthaldialdehyde reagent containing 3‐mercaptopropionic acid. The derivatives formed were analysed by isocratic RP‐HPLC with electrochemical detection at +320 mV. The mobile phase consisted of 50 mM phosphate buffer (pH 6.1) containing 10% v/v acetonitrile, the flow rate was 1 mL/min. The retention times of all compounds including monomethylarginine (internal standard) were <24 min. The LODs (S/N 3:1) were 0.012 μM for both dimethylarginines and 0.013 μM for l ‐arginine; the linearity of the method was from 0.1 to 20 μM for both dimethylarginines and from 1 to 200 μM for l ‐arginine. Absolute extraction recoveries measured for all analytes ranged from 85 to 88%. 相似文献
120.