全文获取类型
收费全文 | 573418篇 |
免费 | 5740篇 |
国内免费 | 1599篇 |
专业分类
化学 | 302679篇 |
晶体学 | 8656篇 |
力学 | 26802篇 |
综合类 | 22篇 |
数学 | 68091篇 |
物理学 | 174507篇 |
出版年
2021年 | 5043篇 |
2020年 | 5425篇 |
2019年 | 6149篇 |
2018年 | 8191篇 |
2017年 | 8089篇 |
2016年 | 11892篇 |
2015年 | 7134篇 |
2014年 | 11373篇 |
2013年 | 26081篇 |
2012年 | 20170篇 |
2011年 | 24476篇 |
2010年 | 17864篇 |
2009年 | 17840篇 |
2008年 | 22742篇 |
2007年 | 22572篇 |
2006年 | 20674篇 |
2005年 | 18502篇 |
2004年 | 17202篇 |
2003年 | 15257篇 |
2002年 | 15210篇 |
2001年 | 16928篇 |
2000年 | 12818篇 |
1999年 | 10023篇 |
1998年 | 8301篇 |
1997年 | 8152篇 |
1996年 | 7810篇 |
1995年 | 7029篇 |
1994年 | 7000篇 |
1993年 | 6747篇 |
1992年 | 7565篇 |
1991年 | 7732篇 |
1990年 | 7372篇 |
1989年 | 7248篇 |
1988年 | 7210篇 |
1987年 | 7076篇 |
1986年 | 6695篇 |
1985年 | 8661篇 |
1984年 | 8868篇 |
1983年 | 7132篇 |
1982年 | 7223篇 |
1981年 | 7148篇 |
1980年 | 6624篇 |
1979年 | 7272篇 |
1978年 | 7403篇 |
1977年 | 7447篇 |
1976年 | 7391篇 |
1975年 | 6820篇 |
1974年 | 6726篇 |
1973年 | 6869篇 |
1972年 | 4972篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
1.
2.
3.
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
4.
5.
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
6.
7.
8.
MUHAMMAD Naeem Ahmed KHAWAJA Ansar Yasin MUHAMMAD Nawaz Tahir IFZAN Arshad MURTAZA Madni 《结构化学》2015,34(1):26-32
Two new 1,4-disubstituted 1,2,3-triazoles-4-carboxylates were synthesized via click reaction. Compound 1a was synthesized by the interaction of 6-nitro-tetrazolo[1.5-a]-pyridine with ethyl propynoate at room temperature in the presence of Cu(OAc)2 as a catalyst and THF as solvent. Compound 1b was also synthesized by the same manner except that tert-butyl propionate, instead of ethyl propynoate, was used. The compounds were characterized by IR, 1H-NMR, 13C-NMR and single-crystal X-ray diffraction analysis. Compound 1a(C10H9N5O4) crystallizes in the triclinic system, space group P1 with a = 5.0894(9), b = 8.9834(13), c = 13.089(2) ?, α= 83.041(7), β= 80.256(7), γ=87.296(8)°, V = 585.24(16)?3, Z = 2, Mr = 263.22, crystal size(mm) = 0.37 × 0.20 ×0.18,(I 2σ(I)) = 8557, 2493, 1229, Rint = 0.057. Compound 1b(C12H13N5O4) crystallizes in the monoclinic system, space group P21/c with a = 6.8854(5), b = 21.783(2), c = 9.3986(8) ?,β = 93.239(4)°, V = 1407.4(2)?3, Z = 4, Mr = 291.27, crystal size(mm) = 0.38 × 0.22 × 0.20,(I 2σ(I)) = 11842, 3172, 1866, Rint = 0.047. Antimicrobial assay results showed that the title compounds display excellent activities to different bacterial and fungal strains. 相似文献
9.
Nano palladium supported on high‐surface‐area metal–organic framework MIL‐101: an efficient catalyst for Sonogashira coupling of aryl and heteroaryl bromides with alkynes 下载免费PDF全文
Manne Annapurna T. Parsharamulu P. Vishnuvardhan Reddy M. Suresh Pravin R. Likhar Mannepalli Lakshmi Kantam 《应用有机金属化学》2015,29(4):234-239
Palladium nanoparticle‐incorporated metal–organic framework MIL‐101 (Pd/MIL‐101) was successfully synthesized and characterized using X‐ray diffraction, nitrogen physisorption, X‐ray photoelectron, UV–visible and infrared spectroscopies, and transmission electron microscopy. The characterization techniques confirmed high porosity and high surface area of MIL‐101 and high stability of nano‐size palladium particles. Pd/MIL‐101 nanocomposite was investigated for the Sonogashira cross‐coupling reaction of aryl and heteroaryl bromides with various alkynes under copper‐free conditions. The reusability of the catalyst was tested for up to four cycles without any significant loss in catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
10.
We study the full counting statistics of transport electrons through a semiconductor two-level quantum dot with Rashba spin–orbit (SO) coupling, which acts as a nonabelian gauge field and thus induces the electron transition between two levels along with the spin flip. By means of the quantum master equation approach, shot noise and skewness are obtained at finite temperature with two-body Coulomb interaction. We particularly demonstrate the crucial effect of SO coupling on the super-Poissonian fluctuation of transport electrons, in terms of which the SO coupling can be probed by the zero-frequency cumulants. While the charge currents are not sensitive to the SO coupling. 相似文献