全文获取类型
收费全文 | 10896篇 |
免费 | 267篇 |
国内免费 | 36篇 |
专业分类
化学 | 7541篇 |
晶体学 | 70篇 |
力学 | 136篇 |
数学 | 1559篇 |
物理学 | 1893篇 |
出版年
2020年 | 124篇 |
2019年 | 101篇 |
2016年 | 208篇 |
2015年 | 193篇 |
2014年 | 176篇 |
2013年 | 378篇 |
2012年 | 362篇 |
2011年 | 456篇 |
2010年 | 256篇 |
2009年 | 271篇 |
2008年 | 382篇 |
2007年 | 416篇 |
2006年 | 369篇 |
2005年 | 406篇 |
2004年 | 369篇 |
2003年 | 306篇 |
2002年 | 272篇 |
2001年 | 168篇 |
2000年 | 170篇 |
1999年 | 172篇 |
1998年 | 147篇 |
1997年 | 161篇 |
1996年 | 176篇 |
1995年 | 177篇 |
1994年 | 167篇 |
1993年 | 184篇 |
1992年 | 186篇 |
1991年 | 167篇 |
1990年 | 133篇 |
1989年 | 153篇 |
1988年 | 156篇 |
1987年 | 151篇 |
1986年 | 152篇 |
1985年 | 198篇 |
1984年 | 158篇 |
1983年 | 167篇 |
1982年 | 167篇 |
1981年 | 148篇 |
1980年 | 157篇 |
1979年 | 147篇 |
1978年 | 131篇 |
1977年 | 134篇 |
1976年 | 122篇 |
1974年 | 143篇 |
1973年 | 137篇 |
1971年 | 96篇 |
1961年 | 149篇 |
1960年 | 200篇 |
1959年 | 108篇 |
1958年 | 119篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
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
3.
4.
Let R be a discrete nonsingular equivalence relation on a standard probability space , and let V be an ergodic strongly asymptotically central automorphism of R. We prove that every V-invariant cocycle with values in a Polish group G takes values in an abelian subgroup of G.
The hypotheses of this result are satisfied, for example, if A is a finite set, a closed, shift-invariant subset, V is the shift, μ a shift-invariant and ergodic probability measure on X, the two-sided tail-equivalence relation on X, a shift-invariant subrelation which is μ-nonsingular, and a shift-invariant cocycle. 相似文献
5.
Michel Weber 《Transactions of the American Mathematical Society》2006,358(2):911-936
We apply a majorizing measure theorem of Talagrand to obtain uniform bounds for sums of random variables satisfying increment conditions of the type considered in Gál-Koksma Theorems. We give some applications.
6.
O. Kortner M.P. Locher V.E. Markushin P. Weber O. Wigger 《The European Physical Journal C - Particles and Fields》2002,25(3):353-360
We study correlations in the exclusive reaction at rest with complete reconstruction of the kinematics for each event. The inclusive distribution is fairly flat at small
invariant mass of the pion pair while a small enhancement in the double differential distribution is observed for small invariant
masses of both pion pairs. Dynamical models with resonances in the final state are shown to be consistent with the data while
the stochastic HBT mechanism is not supported by the present findings.
Received: 26 February 2002 / Revised version: 22 July 2002 / Published online: 30 August 2002 相似文献
7.
8.
9.
Michel Weber 《Results in Mathematics》2005,47(3-4):340-354
Under a very moderate assumption on the Fourier coefficients of a periodic function, we show the convergence almost everywhere of the sequence of averages of its associated Riemann sums. The structure of the set of averages is analyzed by proving a spectral regularization type inequality, which allows to control the corresponding Littlewood-Paley square function. 相似文献
10.