全文获取类型
收费全文 | 2249篇 |
免费 | 78篇 |
国内免费 | 16篇 |
专业分类
化学 | 1578篇 |
晶体学 | 9篇 |
力学 | 57篇 |
数学 | 409篇 |
物理学 | 290篇 |
出版年
2023年 | 20篇 |
2022年 | 29篇 |
2021年 | 37篇 |
2020年 | 57篇 |
2019年 | 50篇 |
2018年 | 15篇 |
2017年 | 26篇 |
2016年 | 72篇 |
2015年 | 68篇 |
2014年 | 77篇 |
2013年 | 105篇 |
2012年 | 126篇 |
2011年 | 169篇 |
2010年 | 87篇 |
2009年 | 111篇 |
2008年 | 157篇 |
2007年 | 133篇 |
2006年 | 137篇 |
2005年 | 103篇 |
2004年 | 112篇 |
2003年 | 75篇 |
2002年 | 79篇 |
2001年 | 32篇 |
2000年 | 32篇 |
1999年 | 27篇 |
1998年 | 26篇 |
1997年 | 20篇 |
1996年 | 19篇 |
1995年 | 16篇 |
1994年 | 9篇 |
1993年 | 11篇 |
1992年 | 12篇 |
1991年 | 11篇 |
1990年 | 10篇 |
1989年 | 8篇 |
1988年 | 10篇 |
1987年 | 21篇 |
1985年 | 11篇 |
1984年 | 18篇 |
1983年 | 20篇 |
1982年 | 11篇 |
1981年 | 17篇 |
1980年 | 18篇 |
1979年 | 12篇 |
1977年 | 10篇 |
1975年 | 7篇 |
1974年 | 8篇 |
1973年 | 8篇 |
1972年 | 9篇 |
1964年 | 7篇 |
排序方式: 共有2343条查询结果,搜索用时 46 毫秒
81.
82.
83.
Lars Carlsena Klaus Bechgaardb Claus S. Jacobsen Ib Johansen 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2)
Abstract Tetrathiafulvalene S-oxide (TTF-ox) was first detected by mass spectrometry in samples of Tetrathiafulvalene (TTF) which had been exposed to oxygen. Pure TTF-ox was prepared by peracid oxidation of TTF and isolated as a relativly stable solid. Physical data will be presented. 相似文献
84.
Ove Alexander Høgmoen Åstrand Lars Peter Engeset Austdal Ragnhild E. Paulsen Trond Vidar Hansen Pål Rongved 《Tetrahedron》2013
Herein the synthesis and characterization of new, lipophilic highly Zn2+-selective fluorescent probes are reported. High affinity for zinc (Kd 1.1–8.0 nM) over other biologically relevant metals and mixtures of metals was observed. Excitation at 360 nm afforded an emission spectrum with maximum at 530 nm for the zinc bound complex. The linear relationship between fluorescence intensity and zinc concentration indicates that FZnA-probes can be used for quantification. The probes have been synthesized in 28–45% overall yield and the feasibility for further functionalization with biologically relevant side chains has been demonstrated. In vitro studies using PC12 cells and 10 μM of one of the novel probes (FZnA-Ada) visualized endogenous labile Zn2+ after 45 min incubation time. 相似文献
85.
Elisabeth Siebert Marius Horch Yvonne Rippers Johannes Fritsch Stefan Frielingsdorf Oliver Lenz Francisco VelazquezEscobar Friedrich Siebert Lars Paasche Uwe Kuhlmann Friedhelm Lendzian Maria‐Andrea Mroginski Ingo Zebger Peter Hildebrandt 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2013,125(19):5267-5270
86.
Cédric Lesaint Heléne Vrålstad Øyvind Spets Sébastien Simon Andreas Hannisdal Lars Lundgaard 《Journal of Dispersion Science and Technology》2013,34(6):874-880
The dielectric properties and the composition of fourteen light to heavy crude oils have been analyzed. Frequency domain spectroscopy (FDS) has been used in order to determine their dielectric response in the frequency range 0.01 to 1000 Hz. For all the crude oils, over the whole frequency range under study, dielectric loss, ?″, shows a linear dependence of frequency indicating a pure direct current (DC) conductivity. As temperature is gradually increased, the dielectric loss, ?″, increases as well, showing a strong temperature dependence. The storage modulus, ?′, shows an explicit behaviour at low frequency that could be due to adsorption of oil components onto the electrodes. We tried to correlate some physical and chemical properties (density, viscosity, SARA, TAN, water content) of the studied crude oils with their conductivity measured at various temperatures. No correlation was found and different hypothesis are suggested by the authors to explain this phenomenon. 相似文献
87.
Ellman's dihydropyran resin was used for selective protection of monosaccharide thioglycosides and glycosides. Following on‐resin acylation and subsequent cleavage of the polymer‐bound intermediates, product components having selectively unblocked hydroxyl functions could be obtained. 相似文献
88.
89.
Lars Kröger 《Journal of carbohydrate chemistry》2013,32(7):717-722
Natural O‐glycoproteins such as the Thomsen‐Friedenreich antigen or gangliosides contain the motif Galβ1‐3GalNAc as an important disaccharide with significant biologic activity. The arrangement of spatial functionalities in this structure are of particular interest with regard to the development of potential leads en route to pharmaceuticals. Therefore, it was desired to obtain access to a range of modified derivatives of the aforementioned motif paying particular attention to introducing specific deoxy functions instead of hydroxyl groups. 相似文献
90.
Marcus Malo Ronnie Persson Peder Svensson Kristina Luthman Lars Brive 《Journal of computer-aided molecular design》2013,27(3):277-291
Prediction of 3D structures of membrane proteins, and of G-protein coupled receptors (GPCRs) in particular, is motivated by their importance in biological systems and the difficulties associated with experimental structure determination. In the present study, a novel method for the prediction of 3D structures of the membrane-embedded region of helical membrane proteins is presented. A large pool of candidate models are produced by repacking of the helices of a homology model using Monte Carlo sampling in torsion space, followed by ranking based on their geometric and ligand-binding properties. The trajectory is directed by weak initial restraints to orient helices towards the original model to improve computation efficiency, and by a ligand to guide the receptor towards a chosen conformational state. The method was validated by construction of the β1 adrenergic receptor model in complex with (S)-cyanopindolol using bovine rhodopsin as template. In addition, models of the dopamine D2 receptor were produced with the selective and rigid agonist (R)-N-propylapomorphine ((R)-NPA) present. A second quality assessment was implemented by evaluating the results from docking of a library of 29 ligands with known activity, which further discriminated between receptor models. Agonist binding and recognition by the dopamine D2 receptor is interpreted using the 3D structure model resulting from the approach. This method has a potential for modeling of all types of helical transmembrane proteins for which a structural template with sequence homology sufficient for homology modeling is not available or is in an incorrect conformational state, but for which sufficient empirical information is accessible. 相似文献