全文获取类型
收费全文 | 11628篇 |
免费 | 311篇 |
国内免费 | 322篇 |
专业分类
化学 | 1965篇 |
晶体学 | 98篇 |
力学 | 76篇 |
综合类 | 29篇 |
数学 | 8822篇 |
物理学 | 1271篇 |
出版年
2023年 | 43篇 |
2022年 | 116篇 |
2021年 | 81篇 |
2020年 | 98篇 |
2019年 | 291篇 |
2018年 | 287篇 |
2017年 | 178篇 |
2016年 | 144篇 |
2015年 | 161篇 |
2014年 | 340篇 |
2013年 | 769篇 |
2012年 | 335篇 |
2011年 | 816篇 |
2010年 | 583篇 |
2009年 | 752篇 |
2008年 | 862篇 |
2007年 | 875篇 |
2006年 | 680篇 |
2005年 | 519篇 |
2004年 | 425篇 |
2003年 | 398篇 |
2002年 | 312篇 |
2001年 | 257篇 |
2000年 | 266篇 |
1999年 | 290篇 |
1998年 | 267篇 |
1997年 | 192篇 |
1996年 | 251篇 |
1995年 | 254篇 |
1994年 | 223篇 |
1993年 | 192篇 |
1992年 | 152篇 |
1991年 | 88篇 |
1990年 | 102篇 |
1989年 | 70篇 |
1988年 | 55篇 |
1987年 | 63篇 |
1986年 | 34篇 |
1985年 | 70篇 |
1984年 | 55篇 |
1983年 | 45篇 |
1982年 | 60篇 |
1981年 | 51篇 |
1980年 | 34篇 |
1979年 | 15篇 |
1978年 | 26篇 |
1977年 | 27篇 |
1976年 | 22篇 |
1975年 | 11篇 |
1973年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
Tomasz Przebinda 《Journal of Functional Analysis》2018,274(5):1284-1305
We relate the distribution characters and the wave front sets of unitary representation for real reductive dual pairs of type I in the stable range. 相似文献
4.
5.
Pu Duan Bo Zhi Luke Coburn Christy L. Haynes Klaus Schmidt-Rohr 《Magnetic resonance in chemistry : MRC》2020,58(11):1130-1138
The composition of fluorescent polymer nanoparticles, commonly referred to as carbon dots, synthesized by microwave-assisted reaction of citric acid and ethylenediamine was investigated by 13C, 13C{1H}, 1H─13C, 13C{14N}, and 15N solid-state nuclear magnetic resonance (NMR) experiments. 13C NMR with spectral editing provided no evidence for significant condensed aromatic or diamondoid carbon phases. 15N NMR showed that the nanoparticle matrix has been polymerized by amide and some imide formation. Five small, resolved 13C NMR peaks, including an unusual ═CH signal at 84 ppm (1H chemical shift of 5.8 ppm) and ═CN2 at 155 ppm, and two distinctive 15N NMR resonances near 80 and 160 ppm proved the presence of 5-oxo-1,2,3,5-tetrahydroimidazo[1,2-a]pyridine-7-carboxylic acid (IPCA) or its derivatives. This molecular fluorophore with conjugated double bonds, formed by a double cyclization reaction of citric acid and ethylenediamine as first shown by Y. Song, B. Yang, and coworkers in 2015, accounts for the fluorescence of the carbon dots. Cross-peaks in a 1H─13C HETCOR spectrum with brief 1H spin diffusion proved that IPCA is finely dispersed in the polyamide matrix. From quantitative 13C and 15N NMR spectra, a high concentration (18 ± 2 wt%) of IPCA in the carbon dots was determined. A pronounced gradient in 13C chemical-shift perturbations and peak widths, with the broadest lines near the COO group of IPCA, indicated at least partial transformation of the carboxylic acid of IPCA by amide or ester formation. 相似文献
6.
Roberto Aravire Ahmed Laghribi Manuel ORyan 《Journal of Pure and Applied Algebra》2019,223(1):439-457
Let F be a field of characteristic 2. In this paper we give a complete computation of the kernel of the homomorphism induced by scalar extension, where is a purely inseparable extension (of any degree), is the cokernel of the Artin–Schreier operator given by: , where is the space of absolute m-differential forms over F and d is the differential operator. Other related results are included. 相似文献
7.
Sameerah Jamal 《Journal of Differential Equations》2019,266(7):4018-4026
A manifold that contains small perturbations will induce a perturbed partial differential equation. The partial differential equation that we select is the Poisson equation – in order to explore the interplay between the geometry of the manifold and the perturbations. Specifically, we show how the problem of symmetry determination, for higher-order perturbations, can be elegantly expressed via geometric conditions. 相似文献
8.
Alessandro Morando Paola Trebeschi Tao Wang 《Journal of Differential Equations》2019,266(9):5397-5430
We show the short-time existence and nonlinear stability of vortex sheets for the nonisentropic compressible Euler equations in two spatial dimensions, based on the weakly linear stability result of Morando and Trebeschi (2008) [20]. The missing normal derivatives are compensated through the equations of the linearized vorticity and entropy when deriving higher-order energy estimates. The proof of the resolution for this nonlinear problem follows from certain a priori tame estimates on the effective linear problem in the usual Sobolev spaces and a suitable Nash–Moser iteration scheme. 相似文献
9.
Cemil Ibis Sibel Sahinler Ayla Elvira Babayeva 《Phosphorus, sulfur, and silicon and the related elements》2020,195(6):474-480
AbstractIn the present study, the reactions of 2,3-dichloro-1,4-naphthoquinone (DCNQ) with amino-1,2-propanediol and some thiols were investigated. Novel N-, N,S-, and S,O- substituted derivatives were obtained and the structures of all compounds were characterized by spectroscopic methods (FT-IR, 1H NMR, 13C NMR, Mass spectroscopy) and microanalysis. The absorption behaviors of novel compounds were also investigated with UV-Vis spectroscopy in different solvents, such as ethanol, tetrahydrofuran and chloroform. 相似文献
10.