全文获取类型
收费全文 | 29542篇 |
免费 | 4869篇 |
国内免费 | 4507篇 |
专业分类
化学 | 22924篇 |
晶体学 | 456篇 |
力学 | 1454篇 |
综合类 | 336篇 |
数学 | 3388篇 |
物理学 | 10360篇 |
出版年
2024年 | 70篇 |
2023年 | 520篇 |
2022年 | 778篇 |
2021年 | 1002篇 |
2020年 | 1182篇 |
2019年 | 1238篇 |
2018年 | 1036篇 |
2017年 | 1065篇 |
2016年 | 1391篇 |
2015年 | 1423篇 |
2014年 | 1771篇 |
2013年 | 2250篇 |
2012年 | 2702篇 |
2011年 | 2855篇 |
2010年 | 2153篇 |
2009年 | 2024篇 |
2008年 | 2200篇 |
2007年 | 1974篇 |
2006年 | 1856篇 |
2005年 | 1510篇 |
2004年 | 1131篇 |
2003年 | 922篇 |
2002年 | 910篇 |
2001年 | 795篇 |
2000年 | 672篇 |
1999年 | 566篇 |
1998年 | 418篇 |
1997年 | 356篇 |
1996年 | 354篇 |
1995年 | 318篇 |
1994年 | 279篇 |
1993年 | 196篇 |
1992年 | 174篇 |
1991年 | 162篇 |
1990年 | 149篇 |
1989年 | 105篇 |
1988年 | 87篇 |
1987年 | 68篇 |
1986年 | 69篇 |
1985年 | 64篇 |
1984年 | 21篇 |
1983年 | 23篇 |
1982年 | 23篇 |
1981年 | 11篇 |
1980年 | 9篇 |
1979年 | 10篇 |
1973年 | 2篇 |
1971年 | 4篇 |
1957年 | 5篇 |
1936年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
11.
Yuwei Wang Jia-Jun Yan Shengnan Hu Prof. David James Young Prof. Hong-Xi Li Prof. Zhi-Gang Ren 《化学:亚洲杂志》2021,16(18):2681-2686
A photoluminescent bimetallic cluster [Ag10Cu6(bdppthi)2(C≡CPh)12(MeOH)2(H2O)](ClO4)4 ( 1 , bdppthi=N,N’-bis(diphenylphosphanylmethyl)-tetrahydroimidazole} was synthesized from the PNNP type ligand bdppthi generated in-situ. Upon excitation at 365 nm, 1 exhibited strong phosphorescent emission at 630 nm, which was selectively quenched by NH3 in air or water. The sensing of NH3 was rapid and recoverable, with detection limits of 53 ppm (v/v) in N2 and 21 μmol/L (0.36 ppm, w/w) for NH3 ⋅ H2O in water. Cluster 1 could potentially serve as a bifunctional chemical sensor for the efficient detection of ammonia in waste-gas and waste-water. 相似文献
12.
We investigate terahertz radiation(T-rays) from a pentacene organic diode at room temperature. The quantum chemistry calculation for frequency-related Huang–Rhys factor of pentacene is also carried out. The results demonstrate that the T-rays can come from a bending vibration of pentacene skeleton after the energy of pentacene exciton transferring to the vibrational excited state via electron–phonon coupling. Frequency and natural bond orbital analytics of pentacene and its derivatives are performed in order to explain the result and develop new materials to get higher emission. This work provides a new way to produce T-rays with a simple device at room temperature. 相似文献
13.
Synthesis and Photophysical Properties of a Sc3N@C80‐Corrole Electron Donor–Acceptor Conjugate 下载免费PDF全文
Bin Liu Hongyun Fang Prof. Xiaofang Li Wenting Cai Lipiao Bao Marc Rudolf Fabian Plass Prof. Louzhen Fan Prof. Xing Lu Prof. Dirk M. Guldi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(2):746-752
Embedding endohdedral metallofullerenes (EMFs) into electron donor–acceptor systems is still a challenging task owing to their limited quantities and their still largely unexplored chemical properties. In this study, we have performed a 1,3‐dipolar cycloaddition reaction of a corrole‐based precursor with Sc3N@C80 to regioselectively form a [5,6]‐adduct ( 1 ). The successful attachment of the corrole moiety was confirmed by mass spectrometry. In the electronic ground state, absorption spectra suggest sizeable electronic communications between the electron acceptor and the electron donor. Moreover, the addition pattern occurring at a [5,6]‐bond junction is firmly proven by NMR spectroscopy and electrochemical investigations performed with 1 . In the electronically excited state, which is probed in photophysical assays with 1 , a fast electron‐transfer yields the radical ion pair state consisting of the one‐electron‐reduced Sc3N@C80 and of the one‐electron‐oxidized corrole upon its exclusive photoexcitation. As such, our results shed new light on the practical work utilizing EMFs as building blocks in photovoltaics. 相似文献
14.
15.
Sulfur hexafluoride (SF6) is considered as a potent greenhouse gas, whose effective degradation is challenging. Here we report a computational study on the nucleophilic activation of sulfur hexafluoride by N-heterocyclic carbenes and N-heterocyclic olefins. The result shows that the activation of SF6 is both thermodynamically and kinetically favorable at mild condition using NHOs with fluoro-substituted azolium and sulfur pentafluoride anion being formed. The Gibbs free energy barrier during the activation of SF6 has a linear relationship with the energy of HOMO of substrates, which could be a guideline for applying those compounds that feature higher energy in HOMO to activate SF6 in high efficiency. 相似文献
16.
Guo Yan Li Zhuang Wei Yuxi Zhang Xinxu Shi Kexin 《Journal of Solid State Electrochemistry》2022,26(4):1051-1065
Journal of Solid State Electrochemistry - Polyvinylpyrrolidone (PVP) and graphene (G)-modified iron oxides (Fe2O3-PVP-G) are prepared by a simple hydrothermal reaction. Their morphology and... 相似文献
17.
Bao Nguyen Xuan Duy Khanh Phan Quoc Tung Nguyen Minh 《Set-Valued and Variational Analysis》2022,30(2):465-486
Set-Valued and Variational Analysis - We aim to establish Karush-Kuhn-Tucker multiplier rules involving higher-order complementarity slackness under Hölder metric subregularity. These rules... 相似文献
18.
Peng-Yan Gui Xiao-Hui Yan Wen-Juan Yuan Yuan-Liang Ma Xiao Ding Shuai Liu 《Natural product research》2019,33(19):2830-2836
A new A, D-seco limonoid, named 12-acetyloxyperforatin (1), along with three known ones, were isolated from the leaves of Harrisonia perforata. Their structures were elucidated on the basis of spectroscopic analysis, including extensive NMR techniques and computational modelling. These compounds showed no inhibitory activity against the 11β-HSD1 enzyme. 相似文献
20.
In this paper,we investigate the non-autonomous Hamilton-Jacobi equation ■ where H is 1-periodic with respect to t and M is a compact Riemannian manifold without boundary.We obtain the viscosity solution denoted by T_(t_0)~tφ(x) and show T_(t_0)~tφ(x) converges uniformly to a time-periodic viscosity solution u~*(x,t) of ?_tu+H(t,x,?_xu,u)=0. 相似文献