全文获取类型
收费全文 | 2965篇 |
免费 | 95篇 |
国内免费 | 15篇 |
专业分类
化学 | 1907篇 |
晶体学 | 15篇 |
力学 | 90篇 |
数学 | 571篇 |
物理学 | 492篇 |
出版年
2023年 | 17篇 |
2022年 | 36篇 |
2021年 | 44篇 |
2020年 | 56篇 |
2019年 | 52篇 |
2018年 | 35篇 |
2017年 | 42篇 |
2016年 | 79篇 |
2015年 | 57篇 |
2014年 | 96篇 |
2013年 | 136篇 |
2012年 | 176篇 |
2011年 | 231篇 |
2010年 | 148篇 |
2009年 | 117篇 |
2008年 | 181篇 |
2007年 | 210篇 |
2006年 | 177篇 |
2005年 | 137篇 |
2004年 | 122篇 |
2003年 | 104篇 |
2002年 | 95篇 |
2001年 | 40篇 |
2000年 | 35篇 |
1999年 | 36篇 |
1998年 | 39篇 |
1997年 | 40篇 |
1996年 | 39篇 |
1995年 | 30篇 |
1994年 | 20篇 |
1993年 | 28篇 |
1992年 | 30篇 |
1991年 | 14篇 |
1990年 | 18篇 |
1989年 | 22篇 |
1988年 | 10篇 |
1987年 | 12篇 |
1986年 | 15篇 |
1985年 | 13篇 |
1984年 | 16篇 |
1983年 | 12篇 |
1982年 | 17篇 |
1981年 | 22篇 |
1980年 | 20篇 |
1978年 | 21篇 |
1977年 | 17篇 |
1976年 | 17篇 |
1975年 | 13篇 |
1974年 | 12篇 |
1971年 | 12篇 |
排序方式: 共有3075条查询结果,搜索用时 0 毫秒
111.
We implement time propagation of the nonequilibrium Green function for atoms and molecules by solving the Kadanoff-Baym equations within a conserving self-energy approximation. We here demonstrate the usefulness of time propagation for calculating spectral functions and for describing the correlated electron dynamics in a nonperturbative electric field. We also demonstrate the use of time propagation as a method for calculating charge-neutral excitation energies, equivalent to highly advanced solutions of the Bethe-Salpeter equation. 相似文献
112.
Karlsson Erik Neuhausen Jörg Eichler Robert Danilov Ivan I. Vögele Alexander Türler Andreas 《Journal of Radioanalytical and Nuclear Chemistry》2021,328(2):707-715
Journal of Radioanalytical and Nuclear Chemistry - The usage of silver as a filtering material for removal of iodine from the gas phase of a lead–bismuth eutectic based nuclear reactor was... 相似文献
113.
Determination of conditional stability constants for some divalent transition metal ion‐EDTA complexes by electrospray ionization mass spectrometry 下载免费PDF全文
Susanne Boija Ann Almesåker Erik Hedenström Dan Bylund Håkan Edlund Magnus Norgren 《Journal of mass spectrometry : JMS》2014,49(7):550-556
Conditional stability constants of coordination complexes comprising divalent transition metals, Cu2+, Ni2+, Zn2+, Co2+, and ethylenediaminetetraacetic acid (EDTA) were determined utilizing electrospray ionization mass spectrometry. The deviation of signal response of a reference complex was monitored at addition of a second metal ion. The conditional stability constant for the competing metal was then determined through solution equilibria equations. The method showed to be applicable to a system where Co2+ and Zn2+ competed for EDTA at pH 5. When Cu2+ and Ni2+ competed for EDTA, the equilibrium changed over time. This change was shown to be affected in rate and size by the type of organic solvent added. In this work, 30% of either methanol or acetonitrile was used. It was found that if calibration curves are prepared for both metal complexes in solution and the measurements are repeated with sufficient time space, any change in equilibrium of sample solutions will be discovered. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
114.
Andrew Marais Mikael S. Magnusson Thomas Joffre Erik L. G. Wernersson Lars Wågberg 《Cellulose (London, England)》2014,21(6):3941-3950
Polyelectrolytes have been used extensively in the papermaking industry for various purposes. Although recent studies have shown that polyamines can be efficient dry-strength additives, the mechanism governing the strength enhancement of paper materials following the adsorption of polyamines onto pulp fibres is still not well understood. In this study, the effect of the adsorption of polyallylamine hydrochloride (PAH) onto the surface of unbleached kraft pulp fibres was investigated on both the fibre and the network scale. Isolated fibre crosses were mechanically tested to evaluate the impact of the chemical additive on the interfibre joint strength on the microscopic scale and the effect was compared with that previously observed on the paper sheet scale. X-ray microtomography was used to understand structural changes in the fibrous network following the adsorption of a polyamine such as PAH. Using image analysis methods, it was possible to determine the number of interfibre contacts (or joints) per unit length of fibre as well as the average interfibre joint contact area. The results showed that the median interfibre joint strength increased by 18 % upon adsorption of PAH. This can be achieved both by a larger molecular contact area in the contact zones and by a stronger molecular adhesion. The addition of the polymer also increased the number of efficient interfibre contacts per sheet volume. This combination of effects is the reason why polyamines such as PAH can increase the dry tensile strength of paper materials. 相似文献
115.
A Bioorthogonal Small‐Molecule‐Switch System for Controlling Protein Function in Live Cells 下载免费PDF全文
Dr. Peng Liu Abram Calderon Dr. Georgios Konstantinidis Dr. Jian Hou Dipl. Stephanie Voss Dr. Xi Chen Fu Li Soumya Banerjee Dr. Jan‐Erik Hoffmann Christiane Theiss Dr. Leif Dehmelt Dr. Yao‐Wen Wu 《Angewandte Chemie (International ed. in English)》2014,53(38):10049-10055
Chemically induced dimerization (CID) has proven to be a powerful tool for modulating protein interactions. However, the traditional dimerizer rapamycin has limitations in certain in vivo applications because of its slow reversibility and its affinity for endogenous proteins. Described herein is a bioorthogonal system for rapidly reversible CID. A novel dimerizer with synthetic ligand of FKBP′ (SLF′) linked to trimethoprim (TMP). The SLF′ moiety binds to the F36V mutant of FK506‐binding protein (FKBP) and the TMP moiety binds to E. coli dihydrofolate reductase (eDHFR). SLF′‐TMP‐induced heterodimerization of FKBP(F36V) and eDHFR with a dissociation constant of 0.12 μM . Addition of TMP alone was sufficient to rapidly disrupt this heterodimerization. Two examples are presented to demonstrate that this system is an invaluable tool, which can be widely used to rapidly and reversibly control protein function in vivo. 相似文献
116.
117.
Felix Burkhardt Carl G. Schirmeister Christian Wesemann Massimo Nutini Stefano Pieralli Erik H. Licht Marc Metzger Frederik Wenz Rolf Mülhaupt Benedikt C. Spies 《Molecules (Basel, Switzerland)》2020,25(24)
A polyolefin with certified biocompatibility according to USP class VI was used by our group as feedstock for filament-based 3D printing to meet the highest medical standards in order to print personal protective equipment for our university hospital during the ongoing pandemic. Besides the chemical resistance and durability, as well as the ability to withstand steam sterilization, this polypropylene (PP) copolymer is characterized by its high purity, as achieved by highly efficient and selective catalytic polymerization. As the PP copolymer is suited to be printed with all common printers in fused filament fabrication (FFF), it offers an eco-friendly cost–benefit ratio, even for large-scale production. In addition, a digital workflow was established focusing on common desktop FFF printers in the medical sector. It comprises the simulation-based optimization of personalized print objects, considering the inherent material properties such as warping tendency, through to validation of the process chain by 3D scanning, sterilization, and biocompatibility analysis of the printed part. This combination of digital data processing and 3D printing with a sustainable and medically certified material showed great promise in establishing decentralized additive manufacturing in everyday hospital life to meet peaks in demand, supply bottlenecks, and enhanced personalized patient treatment. 相似文献
118.
Marco Deiana Karam Chand Jan Jamroskovic Ikenna Obi Erik Chorell Nasim Sabouri 《Angewandte Chemie (International ed. in English)》2020,59(2):896-902
The design of turn‐on dyes with optical signals sensitive to the formation of supramolecular structures provides fascinating and underexplored opportunities for G‐quadruplex (G4) DNA detection and characterization. Here, we show a new switching mechanism that relies on the recognition‐driven disaggregation (on‐signal) of an ultrabright coumarin‐quinazoline conjugate. The synthesized probe selectively lights‐up parallel G4 DNA structures via the disassembly of its supramolecular state, demonstrating outputs that are easily integrable into a label‐free molecular logic system. Finally, our molecule preferentially stains the G4‐rich nucleoli of cancer cells. 相似文献
119.
Erik Barwa Tobias F. Pascher Milan On
k Christian van der Linde Martin K. Beyer 《Angewandte Chemie (International ed. in English)》2020,59(19):7467-7471
We investigate activation of carbon dioxide by singly charged hydrated magnesium cations Mg .+(H2O)n, through infrared multiple photon dissociation (IRMPD) spectroscopy combined with quantum chemical calculations. The spectra of [MgCO2(H2O)n].+ in the 1250–4000 cm?1 region show a sharp transition from n=2 to n=3 for the position of the CO2 antisymmetric stretching mode. This is evidence for the activation of CO2 via charge transfer from Mg .+ to CO2 for n≥3, while smaller clusters feature linear CO2 coordinated end‐on to the metal center. Starting with n=5, we see a further conformational change, with CO2.? coordination to Mg2+ gradually shifting from bidentate to monodentate, consistent with preferential hexa‐coordination of Mg2+. Our results reveal in detail how hydration promotes CO2 activation by charge transfer at metal centers. 相似文献
120.
The elution order of the hop α- and β-acids has been studied under different modes of electrokinetic separation. A model is advanced to explain the shorter migration times of the more hydrophobic β-acids compared to the α-acids in micellar electrokinetic chromatography (MEKC). For quality control of the bitter principles in hops, the ruggedness of electrokinetic separation could be improved by replacing MEKC by microemulsion electrokinetic chromatography (MEEKC). 相似文献