全文获取类型
收费全文 | 404861篇 |
免费 | 6178篇 |
国内免费 | 3436篇 |
专业分类
化学 | 199321篇 |
晶体学 | 5828篇 |
力学 | 21982篇 |
综合类 | 165篇 |
数学 | 66069篇 |
物理学 | 121110篇 |
出版年
2021年 | 2691篇 |
2020年 | 3070篇 |
2019年 | 3363篇 |
2018年 | 14084篇 |
2017年 | 13854篇 |
2016年 | 11750篇 |
2015年 | 4781篇 |
2014年 | 6324篇 |
2013年 | 14170篇 |
2012年 | 14805篇 |
2011年 | 23499篇 |
2010年 | 15114篇 |
2009年 | 15390篇 |
2008年 | 18717篇 |
2007年 | 20611篇 |
2006年 | 11782篇 |
2005年 | 11627篇 |
2004年 | 10950篇 |
2003年 | 10457篇 |
2002年 | 9363篇 |
2001年 | 10417篇 |
2000年 | 8029篇 |
1999年 | 6117篇 |
1998年 | 5202篇 |
1997年 | 5061篇 |
1996年 | 4716篇 |
1995年 | 4293篇 |
1994年 | 4294篇 |
1993年 | 3967篇 |
1992年 | 4642篇 |
1991年 | 4681篇 |
1990年 | 4487篇 |
1989年 | 4255篇 |
1988年 | 4340篇 |
1987年 | 4258篇 |
1986年 | 3958篇 |
1985年 | 5230篇 |
1984年 | 5429篇 |
1983年 | 4430篇 |
1982年 | 4536篇 |
1981年 | 4446篇 |
1980年 | 4385篇 |
1979年 | 4482篇 |
1978年 | 4817篇 |
1977年 | 4719篇 |
1976年 | 4717篇 |
1975年 | 4293篇 |
1974年 | 4376篇 |
1973年 | 4479篇 |
1972年 | 3077篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
The influence of different referencing methods on the accuracy of δ13C value measurement of ethanol fuel by gas chromatography/combustion/isotope ratio mass spectrometry
下载免费PDF全文
![点击此处可从《Rapid communications in mass spectrometry : RCM》网站下载免费的PDF全文](/ch/ext_images/free.gif)
42.
Dr. Yulia Y. Enakieva Dr. Anna A. Sinelshchikova Prof. Mikhail S. Grigoriev Prof. Vladimir V. Chernyshev Dr. Konstantin A. Kovalenko Prof. Irina A. Stenina Prof. Andrey B. Yaroslavtsev Prof. Yulia G. Gorbunova Prof. Aslan Y. Tsivadze 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(45):10552-10556
The design of new solid-state proton-conducting materials is a great challenge for chemistry and materials science. Herein, a new anionic porphyrinylphosphonate-based MOF ( IPCE-1Ni ), which involves dimethylammonium (DMA) cations for charge compensation, is reported. As a result of its unique structure, IPCE-1Ni exhibits one of the highest value of the proton conductivity among reported proton-conducting MOF materials based on porphyrins (1.55×10−3 S cm−1 at 75 °C and 80 % relative humidity). 相似文献
43.
Mathematical Notes - 相似文献
44.
In the paper, the authors establish several integral representations for the generating functions of the large and little Schröder numbers and for the large and little Schröder numbers. 相似文献
45.
Knyazev A. A. Karyakin M. E. Krupin A. S. Galyametdinov Yu. G. 《Russian Journal of General Chemistry》2015,85(12):2806-2812
Russian Journal of General Chemistry - Hybrid liquid crystal systems with different ratios of the components have been prepared on the basis of 5,5′-di(heptadecyl)-2,2′-bipyridine... 相似文献
46.
47.
We summarize the results of our recent work on Bäcklund transformations (BTs), particularly focusing on the relation between BTs and infinitesimal symmetries. We present a BT for an associated Degasperis–Procesi (aDP) equation and its superposition principle and investigate the solutions generated by applying this BT. Following our general methodology, we use the superposition principle of the BT to generate the infinitesimal symmetries of the aDP equation. 相似文献
48.
G. Peruginelli 《代数通讯》2018,46(11):4724-4738
We classify the maximal subrings of the ring of n×n matrices over a finite field, and show that these subrings may be divided into three types. We also describe all of the maximal subrings of a finite semisimple ring, and categorize them into two classes. As an application of these results, we calculate the covering number of a finite semisimple ring. 相似文献
49.
Mesoscopic modeling at the pore scale offers great promise in exploring the underlying structure transport performance of flow through porous media. The present work studies the fluid flow subjected to capillarity-induced resonance in porous media characterized by different porous structure and wettability. The effects of porosity and wettability on the displacement behavior of the fluid flow through porous media are discussed. The results are presented in the form of temporal evolution of percentage saturation and displacement of the fluid front through porous media. The present study reveals that the vibration in the form of acoustic excitation could be significant in the mobilization of fluid through the porous media. The dependence of displacement of the fluid on physicochemical parameters like wettability of the surface, frequency along with the porosity is analyzed. It was observed that the mean displacement of the fluid is more in the case of invading fluid with wetting phase where the driving force strength is not so dominant. 相似文献
50.