全文获取类型
收费全文 | 657篇 |
免费 | 26篇 |
国内免费 | 4篇 |
专业分类
化学 | 412篇 |
晶体学 | 1篇 |
力学 | 10篇 |
数学 | 115篇 |
物理学 | 149篇 |
出版年
2023年 | 9篇 |
2022年 | 7篇 |
2021年 | 7篇 |
2020年 | 15篇 |
2019年 | 14篇 |
2018年 | 12篇 |
2017年 | 11篇 |
2016年 | 25篇 |
2015年 | 15篇 |
2014年 | 20篇 |
2013年 | 45篇 |
2012年 | 39篇 |
2011年 | 51篇 |
2010年 | 28篇 |
2009年 | 32篇 |
2008年 | 38篇 |
2007年 | 38篇 |
2006年 | 37篇 |
2005年 | 36篇 |
2004年 | 36篇 |
2003年 | 18篇 |
2002年 | 21篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1999年 | 14篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1996年 | 8篇 |
1995年 | 10篇 |
1994年 | 12篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1988年 | 4篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1973年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有687条查询结果,搜索用时 15 毫秒
101.
Dr. Jason C. Crack Prof. Nick E. Le Brun 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(14):3675-3684
Nitric oxide (NO) can function as both a cytotoxin and a signalling molecule. In both cases, reaction with iron–sulfur (Fe–S) cluster proteins plays an important role because Fe–S clusters are reactive towards NO and so are a primary site of general NO-induced damage (toxicity). This sensitivity to nitrosylation is harnessed in the growing group of regulatory proteins that function in sensing of NO via an Fe–S cluster. Although information about the products of cluster nitrosylation is now emerging, detection and identification of intermediates remains a major challenge, due to their transient nature and the difficulty in distinguishing spectroscopically similar iron-NO species. Here we report studies of the NO-sensing Fe–S cluster regulators NsrR and WhiD using non-denaturing mass spectrometry, in which non-covalent interactions between the protein and Fe/S/NO species are preserved. The data provide remarkable insight into the nitrosylation reactions, permitting identification, for the first time, of protein-bound mono-, di- and tetranitrosyl [4Fe–4S] cluster complexes ([4Fe–4S](NO), [4Fe–4S])(NO)2 and [4Fe–4S](NO)4) as intermediates along pathways to formation of product Roussin's red ester (RRE) and Roussin's black salt (RBS)-like species. The data allow the nitrosylation mechanisms of NsrR and WhiD to be elucidated and clearly distinguished. 相似文献
102.
103.
Kimberley L. Anderson Wigen Nazarov Christopher S. A. Musgrave Nick Bazin Douglas Faith 《Journal of Radioanalytical and Nuclear Chemistry》2014,299(2):969-975
PolyHIPE foams with densities of 0.05–0.1 g cm?3 have been prepared by the polymerisation of the continuous phase of high internal phase emulsions (HIPEs). The internal aqueous phase in HIPE occupies more than 74 % of the total volume, which leads to highly porous and open-cell morphologies. In this paper a method of preparing polyHIPE foams by using reversible addition-fragmentation chain transfer (RAFT) polymerisation has been investigated. Polystyrene-co-polymethyl methacrylate (PS-co-PMMA) has been studied and by using a variety of characterisation methods, it was possible to compare the polyHIPEs prepared by the conventional free radical polymerisation (FRP) to those by RAFT polymerisation. Scanning electron microscopy images have confirmed the presence of a cellular polyHIPE structure. PS-co-PMMA polyHIPEs made by RAFT have significantly narrower molecular weight distribution with values for the polydispersity index (PDI) for PS-co-PMMA between 1.46 and 2.08 compared to 4.68 observed by FRP. The effects of different concentrations of the RAFT agent on structure, glass transition temperature (T g) and PDI of PS-co-PMMA polyHIPE foams are presented. 相似文献
104.
Let T be a bounded linear operator in a complex Banach space.Our main result gives various characterizations of the condition:T is power-bounded and an estimate ||(I – T)Tn || cn–1/2 holds for all positive integers n. In particular, this conditionholds if and only if T = β S + (1 – β)I, forsome β (0, 1) and some power-bounded operator S; or ifand only if T is power-bounded and the discrete semigroup (Tn)is dominated by the continuous semigroup (e– t(I –T))t 0 in a natural sense. As a consequence of our main results,for 1/2 < 1 we characterize the condition that T is power-boundedand ||(I – T)Tn || c n– for all n, in terms ofestimates on the semigroup e–t(I – T). 相似文献
105.
Don Coppersmith Nick Howgrave-Graham S. V. Nagaraj. 《Mathematics of Computation》2008,77(261):531-545
Let be integers satisfying , , , and let . Lenstra showed that the number of integer divisors of equivalent to is upper bounded by . We re-examine this problem, showing how to explicitly construct all such divisors, and incidentally improve this bound to .
106.
Di Censo D Fantacci S De Angelis F Klein C Evans N Kalyanasundaram K Bolink HJ Grätzel M Nazeeruddin MK 《Inorganic chemistry》2008,47(3):980-989
Highly phosphorescent blue-light-emitting anionic iridium complexes (C4H9)4N[Ir(2-phenylpyridine)2(CN)2] (1), (C4H9)4N[Ir(2-phenyl-4-dimethylaminopyridine)2(CN)2] (2), (C4H9)4N[Ir(2-(2,4-difluorophenyl)-pyridine)2(CN)2] (3), (C4H9)4N[Ir(2-(2,4-difluorophenyl)-4-dimethylaminopyridine)2(CN)2] (4), and (C4H9)4N[Ir(2-(3,5-difluorophenyl)-4-dimethylaminopyridine)2(CN)2] (5) were synthesized and characterized using NMR, UV-vis absorption, and emission spectroscopy and electrochemical methods. In these complexes color and quantum yield tuning aspects are demonstrated by modulating the ligands with substituting donor and acceptor groups on both the pyridine and phenyl moieties of 2-phenylpyridine. Complexes 1-5 display intense photoluminescence maxima in the blue region of the visible spectrum and exhibit very high phosphorescence quantum yields, in the range of 50-80%, with excited-state lifetimes of 1-4 micros in acetonitrile solution at 298 K. DFT and time dependent-DFT calculations were performed on the ground and excited states of the investigated complexes to provide insight into the structural, electronic, and optical properties of these systems. 相似文献
107.
Efficient Blue‐Colored Solid‐State Dye‐Sensitized Solar Cells: Enhanced Charge Collection by Using an in Situ Photoelectrochemically Generated Conducting Polymer Hole Conductor 下载免费PDF全文
Jinbao Zhang Dr. Nick Vlachopoulos Dr. Yan Hao Dr. Thomas W. Holcombe Prof. Gerrit Boschloo Dr. Erik M. J. Johansson Prof. Michael Grätzel Prof. Anders Hagfeldt 《Chemphyschem》2016,17(10):1441-1445
A high power conversion efficiency (PCE) of 5.5 % was achieved by efficiently incorporating a diketopyrrolopyrrole‐based dye with a conducting polymer poly(3,4‐ethylenediothiophene) (PEDOT) hole‐transporting material (HTM) that was formed in situ, compared with a PCE of 2.9 % for small molecular spiro‐OMeTAD‐based solid‐state dye solar cells (sDSCs). The high PCE for PEDOT‐based sDSCs is mainly attributed to the significantly enhanced charge‐collection efficiency, as a result of the three‐order‐of‐magnitude higher hole conductivity (0.53 S cm?1) compared with that of the widely used low molecular weight HTM spiro‐OMeTAD (3.5×10?4 S cm?1). 相似文献
108.
Nitrosylation of Nitric‐Oxide‐Sensing Regulatory Proteins Containing [4Fe‐4S] Clusters Gives Rise to Multiple Iron–Nitrosyl Complexes 下载免费PDF全文
Pauline N. Serrano Dr. Hongxin Wang Dr. Jason C. Crack Christopher Prior Prof. Matthew I. Hutchings Prof. Andrew J. Thomson Dr. Saeed Kamali Dr. Yoshitaka Yoda Dr. Jiyong Zhao Dr. Michael Y. Hu Dr. Ercan E. Alp Dr. Vasily S. Oganesyan Prof. Nick E. Le Brun Prof. Stephen P. Cramer 《Angewandte Chemie (International ed. in English)》2016,55(47):14575-14579
The reaction of protein‐bound iron–sulfur (Fe‐S) clusters with nitric oxide (NO) plays key roles in NO‐mediated toxicity and signaling. Elucidation of the mechanism of the reaction of NO with DNA regulatory proteins that contain Fe‐S clusters has been hampered by a lack of information about the nature of the iron‐nitrosyl products formed. Herein, we report nuclear resonance vibrational spectroscopy (NRVS) and density functional theory (DFT) calculations that identify NO reaction products in WhiD and NsrR, regulatory proteins that use a [4Fe‐4S] cluster to sense NO. This work reveals that nitrosylation yields multiple products structurally related to Roussin's Red Ester (RRE, [Fe2(NO)4(Cys)2]) and Roussin's Black Salt (RBS, [Fe4(NO)7S3]. In the latter case, the absence of 32S/34S shifts in the Fe?S region of the NRVS spectra suggest that a new species, Roussin's Black Ester (RBE), may be formed, in which one or more of the sulfide ligands is replaced by Cys thiolates. 相似文献
109.
Rodgers SL Davis AM Tomkinson NP van de Waterbeemd H 《Journal of chemical information and modeling》2007,47(6):2401-2407
It is assumed that compounds occupying the same region of model space will be subject to similar errors in prediction, and hence, where these errors are known, they can be applied to predictions. Thus, any available measured data can be used to refine predictions of query compounds. This study describes the application of a correction library to a human plasma protein binding model. Compounds that have been measured since the model was built are entered into the library to improve predictions of current compounds. Time-series simulations were conducted to measure the time dependence of the correction library. This study demonstrates significant improvements in predictions where a library is applied, compared with both a static model and an updating model that includes recently measured data. 相似文献
110.
Nick Dungey 《Probability Theory and Related Fields》2007,137(3-4):429-442
Let G be a compactly generated, locally compact group, and let T be the operator of convolution with a probability measure μ on G. Our main results give sufficient conditions on μ for the operator T to be analytic in L
p
(G), 1 < p < ∞, where analyticity means that one has an estimate of form for all n = 1, 2, ... in L
p
operator norm. Counterexamples show that analyticity may not hold if some of the conditions are not satisfied. 相似文献