全文获取类型
收费全文 | 2964篇 |
免费 | 65篇 |
国内免费 | 21篇 |
专业分类
化学 | 1734篇 |
晶体学 | 29篇 |
力学 | 76篇 |
数学 | 463篇 |
物理学 | 748篇 |
出版年
2021年 | 20篇 |
2020年 | 38篇 |
2019年 | 28篇 |
2018年 | 22篇 |
2017年 | 23篇 |
2016年 | 49篇 |
2015年 | 34篇 |
2014年 | 45篇 |
2013年 | 135篇 |
2012年 | 151篇 |
2011年 | 179篇 |
2010年 | 72篇 |
2009年 | 61篇 |
2008年 | 150篇 |
2007年 | 145篇 |
2006年 | 114篇 |
2005年 | 125篇 |
2004年 | 114篇 |
2003年 | 91篇 |
2002年 | 79篇 |
2001年 | 49篇 |
2000年 | 45篇 |
1999年 | 25篇 |
1998年 | 26篇 |
1997年 | 27篇 |
1996年 | 44篇 |
1995年 | 41篇 |
1994年 | 35篇 |
1993年 | 39篇 |
1992年 | 46篇 |
1991年 | 25篇 |
1990年 | 36篇 |
1989年 | 32篇 |
1988年 | 40篇 |
1987年 | 33篇 |
1986年 | 18篇 |
1985年 | 55篇 |
1984年 | 54篇 |
1983年 | 33篇 |
1982年 | 51篇 |
1981年 | 40篇 |
1980年 | 41篇 |
1979年 | 42篇 |
1978年 | 54篇 |
1977年 | 39篇 |
1976年 | 40篇 |
1975年 | 38篇 |
1974年 | 41篇 |
1973年 | 39篇 |
1970年 | 17篇 |
排序方式: 共有3050条查询结果,搜索用时 15 毫秒
1.
Ke Xu Evan T. Vickers Longshi Rao Dr. Sarah A. Lindley A'Lester C. Allen Prof. Binbin Luo Prof. Xueming Li Prof. Jin Zhong Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(19):5014-5021
CH3NH3PbBr3 perovskite quantum dots (PQDs) are synthesized by using four different linear alkyl phosphonic acids (PAs) in conjunction with (3-aminopropyl)triethoxysilane (APTES) as capping ligands. The resultant PQDs are characterized by means of XRD, TEM, Raman spectroscopy, FTIR spectroscopy, UV/Vis, photoluminescence (PL), time-resolved PL, and X-ray photoelectron spectroscopy (XPS). PA chain length is shown to control the PQD size (ca. 2.9–4.2 nm) and excitonic absorption band positions (λ=488–525 nm), with shorter chain lengths corresponding to smaller sizes and bluer absorptions. All samples show a high PL quantum yield (ca. 46–83 %) and high PL stability; this is indicative of a low density of band gap trap states and effective surface passivation. Stability is higher for smaller PQDs; this is attributed to better passivation due to better solubility and less steric hindrance of the shorter PA ligands. Based on the FTIR, Raman, and XPS results, it is proposed that Pb2+ and CH3NH3+ surface defects are passivated by R−PO32− or R−PO2(OH)−, whereas Br− surface defects are passivated by R−NH3+ moieties. This study establishes the combination of PA and APTES ligands as a highly effective dual passivation system for the synergistic passivation of multiple surface defects of PQDs through primarily ionic bonding. 相似文献
2.
3.
Dr. Jan H. Blank Dr. Salvador Moncho Allen M. Lunsford Prof. Edward N. Brothers Prof. Marcetta Y. Darensbourg Prof. Ashfaq A. Bengali 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(36):12752-12760
The mechanism and energetics of CO, 1‐hexene, and 1‐hexyne substitution from the complexes (SBenz)2[Fe2(CO)6] (SBenz=SCH2Ph) ( 1 ‐CO), (SBenz)2[Fe2(CO)5(η2‐1‐hexene)] ( 1 ‐(η2‐1‐hexene)), and (SBenz)2[Fe2(CO)5(η2‐1‐hexyne)] ( 1 ‐(η2‐1‐hexyne)) were studied by using time‐resolved infrared spectroscopy. Exchange of both CO and 1‐hexyne by P(OEt)3 and pyridine, respectively, proceeds by a bimolecular mechanism. As similar activation enthalpies are obtained for both reactions, the rate‐determining step in both cases is assumed to be the rotation of the Fe(CO)2L (L=CO or 1‐hexyne) unit to accommodate the incoming ligand. The kinetic profile for the displacement of 1‐hexene is quite different than that for the alkyne and, in this case, both reaction channels, that is, dissociative (SN1) and associative (SN2), were found to be competitive. Because DFT calculations predict similar binding enthalpies of alkene and alkyne to the iron center, the results indicate that the bimolecular pathway in the case of the alkyne is lower in free energy than that of the alkene. In complexes of this type, subtle changes in the departing ligand characteristics and the nature of the mercapto bridge can influence the exchange mechanism, such that more than one reaction pathway is available for ligand substitution. The difference between this and the analogous study of (μ‐pdt)[Fe(CO)3]2 (pdt=S(CH2)3S) underscores the unique characteristics of a three‐atom S?S linker in the active site of diiron hydrogenases. 相似文献
4.
Theodore Flack Thibaut Constantin Sylvain Penasse Dr. Jérôme Dejeu Béatrice Gennaro Dr. Muriel Jourdan Aurélien Laguerre Marc Pirrotta Dr. David Monchaud Dr. Nicolas Spinelli Prof. Eric Defrancq 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(5):1760-1767
A water‐soluble template‐assembled synthetic G‐quartet (TASQ) based on the use of a macrocyclodecapeptide scaffold was designed to display stable intramolecular folds alone in solution. The preformation of the guanine quartet, demonstrated by NMR and CD investigations, results in enhanced peroxidase‐type biocatalytic activities and improved quadruplex‐interacting properties. Comparison of its DNAzyme‐boosting properties with the ones of previously published TASQ revealed that, nowadays, it is the best DNAzyme‐boosting agent. 相似文献
5.
6.
Potential Analysis - We study in this article a stochastic version of a 2D Ericksen-Leslie systems. The system model the dynamic of nematic liquid crystals under the influence of stochastic... 相似文献
7.
8.
9.
Stereochemical Studies of the Karlotoxin Class Using NMR Spectroscopy and DP4 Chemical‐Shift Analysis: Insights into their Mechanism of Action 下载免费PDF全文
Dr. Amanda L. Waters Dr. Joonseok Oh Prof. Allen R. Place Prof. Mark T. Hamann 《Angewandte Chemie (International ed. in English)》2015,54(52):15705-15710
After publication of karlotoxin 2 (KmTx2; 1 ), the harmful algal bloom dinoflagellate Karlodinium sp. was collected and scrutinized to identify additional biologically active complex polyketides. The structure of 1 was validated and revised at C49 using computational NMR tools including J‐based configurational analysis and chemical‐shift calculations. The characterization of two new compounds [KmTx8 ( 2 ) and KmTx9 ( 3 )] was achieved through overlaid 2D HSQC NMR techniques, while the relative configurations were determined by comparison to 1 and computational chemical‐shift calculations. The detailed evaluation of 2 using the NCI‐60 cell lines, NMR binding studies, and an assessment of the literature supports a mode of action (MoA) for targeting cancer‐cell membranes, especially of cytostatic tumors. This MoA is uniquely different from that of current agents employed in the control of cancers for which 2 shows sensitivity. 相似文献
10.
Increased Water Reduction Efficiency of Polyelectrolyte‐Bound Trimetallic [Ru,Rh,Ru] Photocatalysts in Air‐Saturated Aqueous Solutions 下载免费PDF全文
Theodore R. Canterbury Dr. Shamindri M. Arachchige Prof. Robert B. Moore Prof. Karen J. Brewer 《Angewandte Chemie (International ed. in English)》2015,54(43):12819-12822
The groundbreaking use of polyelectrolytes to increase the efficiency of supramolecular photocatalysts in solar H2 production schemes under aqueous aerobic conditions is reported. Supramolecular photocatalysts of the architecture [{(TL)2Ru(BL)}2RhX2]5+ (BL=bridging ligand, TL=terminal ligand, X=halide) demonstrate high efficiencies in deoxygenated organic solvents but do not function in air‐saturated aqueous solution because of the quenching of the metal‐to‐ligand charge‐transfer (MLCT) excited state under these conditions. The new photocatalytic system incorporates poly(4‐styrenesulfonate) (PSS) into aqueous solutions containing [{(bpy)2Ru(dpp)}2RhCl2]5+ (bpy=2,2′‐bipyridine, dpp=2,3‐bis(2‐pyridyl)pyrazine). PSS has a profound impact on the photocatalyst efficiency, increasing H2 production over three times that of deoxygenated aqueous solutions alone. H2 photocatalysis proceeds even under aerobic conditions for PSS‐containing solutions, an exciting consequence for solar hydrogen‐production research. 相似文献