全文获取类型
收费全文 | 9155篇 |
免费 | 552篇 |
国内免费 | 42篇 |
专业分类
化学 | 6735篇 |
晶体学 | 32篇 |
力学 | 157篇 |
数学 | 1478篇 |
物理学 | 1347篇 |
出版年
2023年 | 75篇 |
2022年 | 63篇 |
2021年 | 145篇 |
2020年 | 229篇 |
2019年 | 199篇 |
2018年 | 146篇 |
2017年 | 120篇 |
2016年 | 415篇 |
2015年 | 378篇 |
2014年 | 401篇 |
2013年 | 476篇 |
2012年 | 661篇 |
2011年 | 704篇 |
2010年 | 503篇 |
2009年 | 410篇 |
2008年 | 652篇 |
2007年 | 576篇 |
2006年 | 541篇 |
2005年 | 554篇 |
2004年 | 459篇 |
2003年 | 301篇 |
2002年 | 218篇 |
2001年 | 77篇 |
2000年 | 56篇 |
1999年 | 63篇 |
1998年 | 55篇 |
1997年 | 136篇 |
1996年 | 82篇 |
1995年 | 103篇 |
1994年 | 97篇 |
1993年 | 85篇 |
1992年 | 80篇 |
1991年 | 56篇 |
1990年 | 37篇 |
1989年 | 68篇 |
1988年 | 51篇 |
1987年 | 31篇 |
1986年 | 31篇 |
1985年 | 45篇 |
1984年 | 36篇 |
1983年 | 22篇 |
1982年 | 45篇 |
1981年 | 30篇 |
1980年 | 25篇 |
1979年 | 23篇 |
1978年 | 20篇 |
1977年 | 18篇 |
1975年 | 21篇 |
1973年 | 15篇 |
1968年 | 14篇 |
排序方式: 共有9749条查询结果,搜索用时 18 毫秒
81.
In Situ FTIR Spectroscopy Study of the Photodegradation of Acetaldehyde and azo Dye Photobleaching on Bismuth‐Modified TiO2 下载免费PDF全文
Jiří Henych Václav Štengl Andreas Mattsson Lars Österlund 《Photochemistry and photobiology》2015,91(1):48-58
The photocatalytic properties of bismuth‐modified titania were studied by photobleaching of two aqueous azo dyes solutions (Reactive Black 5 and Acid Orange 7), and by photoinduced decomposition (PID) of acetaldehyde using in situ FTIR spectroscopy. Low bismuth doping concentrations up to 3 at.% is shown to lead to an increased photobleaching rate of both azo dyes solutions. Too high Bi dopant concentrations lead to less developed crystallite nanoparticles and exhibit weaker adsorption capacity. Bismuth doping altered the adsorption kinetics of acetaldehyde resulting in different surface products, and a modified photocatalytic reaction pathway was inferred. 相似文献
82.
A pair of pentacenes that are functionalized in the 6-position with either a 3- or 4-pyridyl group via a triazole linker have been used to form complexes with a tetra(aryl)ruthenium(II) porphyrin through axial coordination. The pentacene–porphyrin dyads 5 and 6 have been structurally characterized through a combination of spectroscopic techniques. UV–vis spectroscopy shows that the absorption profiles of the two chromophores, the porphyrin and the pentacene, are complementary, providing absorptions throughout the UV and visible regions. While the dyads are reasonably stable in the solid state under ambient conditions they are, unfortunately, only stable in solution for hours when exposed to light and air. 相似文献
83.
84.
Dmitry Sharapa Prof. Andreas Hirsch Prof. Bernd Meyer Prof. Timothy Clark 《Chemphyschem》2015,16(10):2165-2171
Ab initio and DFT calculations are used to investigate the structure, electronic properties, spectra and reactivity of cubic C8, which is predicted to be aromatic according to Hirsch′s rule. Although highly strained and with a small amount of diradical character, the carbon cube represents a surprisingly deep minimum and should therefore be observable as an isolated molecule. It is, however, predicted to be very reactive, both with itself and triplet oxygen. Calculated IR, Raman, and UV/Vis spectra are provided to aid identification of cubic C8 should it be synthesized. 相似文献
85.
Acceleration of Long‐Range Photoinduced Electron Transfer through DNA by Hydroxyquinolines as Artificial Base Pairs 下载免费PDF全文
Dr. Effi Bätzner Dr. Yu Liang Caroline Schweigert Dr. Andreas‐Neil Unterreiner Prof. Dr. Hans‐Achim Wagenknecht 《Chemphyschem》2015,16(8):1607-1612
The C‐nucleoside based on the hydroxyquinoline ligand (Hq) is complementary to itself and forms stable Hq–Hq pairs in double‐stranded DNA. These artificial Hq–Hq pairs may serve as artificial electron carriers for long‐range photoinduced electron transfer in DNA, as elucidated by a combination of gel electrophoretic analysis of irradiated samples and time‐resolved transient absorption spectroscopy. For this study, the Hq–Hq pair was combined with a DNA‐based donor–acceptor system consisting of 6‐N,N‐dimethylaminopyrene conjugated to 2′‐deoxyuridine as photoinducible electron donor, and methyl viologen attached to the 2′‐position of uridine as electron acceptor. The Hq radical anion was identified in the time‐resolved measurements and strand cleavage products support its role as an intermediate charge carrier. Hence, the Hq–Hq pair significantly enhances the electron hopping capability of DNA compared to natural DNA bases over long distances while keeping the self‐assembly properties as the most attractive feature of DNA as a supramolecular architecture. 相似文献
86.
Thermal Stability and Molecular Ordering of Organic Semiconductor Monolayers: Effect of an Anchor Group 下载免费PDF全文
Dr. Andrew O. F. Jones Philipp Knauer Prof. Roland Resel Dr. Andreas Ringk Prof. Peter Strohriegl Dr. Oliver Werzer Prof. Michele Sferrazza 《Chemphyschem》2015,16(8):1712-1718
The thermal stability and molecular order in monolayers of two organic semiconductors, PBI‐PA and PBI‐alkyl, based on perylene derivatives with an identical molecular structure except for an anchor group for attachment to the substrate in PBI‐PA, are reported. In situ X‐ray reflectivity measurements are used to follow the stability of these monolayers in terms of order and thickness as temperature is increased. Films have thicknesses corresponding approximately to the length of one molecule; molecules stand upright on the substrate with a defined structure. PBI‐PA monolayers have a high degree of order at room temperature and a stable film exists up to 250 °C, but decomposes rapidly above 300 °C. In contrast, stable physisorbed PBI‐alkyl monolayers only exist up to 100 °C. Above the bulk melting point at 200 °C no more order exists. The results encourage using anchor groups in monolayers for various applications as it allows enhanced stability at the interface with the substrate. 相似文献
87.
88.
Konstantin Dirian Susanne Backes Claudia Backes Volker Strauss Fabian Rodler Frank Hauke Andreas Hirsch Dirk M. Guldi 《Chemical science》2015,6(12):6886-6895
A water soluble naphthalenebisimide derivative (NBI) was synthesized and probed to individualize, suspend, and stabilize single wall carbon nanotubes (SWCNTs). Besides a comprehensive photophysical and electrochemical characterization of NBI, stable suspensions of SWCNTs were realized in buffered D2O. Overall, the dispersion efficiency of the NBI surfactant was determined by comparison with naphthalene based references. Successful individualization of SWCNTs was corroborated in several microscopic assays. In addition, emission spectroscopy points to the strong quenching of SWCNT centered band gap emission, when NBIs are immobilized onto SWCNTs. The origin of the quenching was found to be strong electronic communication, which leads to charge separation between NBIs and photoexcited SWCNTs, and, which yields reduced NBIs as well oxidized SWCNTs. Notably, electrochemical considerations revealed that the energy content of these charge separated states is one of the highest reported for SWCNT based electron donor–acceptor hybrids so far. 相似文献
89.
Christina Schjoeth-Eskesen Paul Robert Hansen Andreas Kjaer Nic Gillings 《ChemistryOpen》2015,4(1):65-71
Aziridines can undergo a range of ring-opening reactions with nucleophiles. The regio- and stereochemistry of the products depend on the substituents on the aziridine. Aziridine ring-opening reactions have rarely been used in radiosynthesis. Herein we report the ring opening of activated aziridine-2-carboxylates with [18F]fluoride. The aziridine was activated for nucleophilic attack by substitution of various groups on the aziridine nitrogen atom. Fluorine-18 radiolabelling was followed by ester hydrolysis and removal of the activation group. Totally regioselective ring opening and subsequent deprotection was achieved with tert-butyloxycarbonyl- and carboxybenzyl-activated aziridines to give α-[18F]fluoro-β-alanine in good radiochemical yield. 相似文献