全文获取类型
收费全文 | 1043篇 |
免费 | 45篇 |
国内免费 | 17篇 |
专业分类
化学 | 701篇 |
力学 | 52篇 |
数学 | 168篇 |
物理学 | 184篇 |
出版年
2023年 | 12篇 |
2022年 | 10篇 |
2021年 | 14篇 |
2020年 | 13篇 |
2019年 | 25篇 |
2018年 | 16篇 |
2017年 | 11篇 |
2016年 | 35篇 |
2015年 | 37篇 |
2014年 | 18篇 |
2013年 | 47篇 |
2012年 | 58篇 |
2011年 | 67篇 |
2010年 | 31篇 |
2009年 | 38篇 |
2008年 | 45篇 |
2007年 | 72篇 |
2006年 | 47篇 |
2005年 | 47篇 |
2004年 | 49篇 |
2003年 | 40篇 |
2002年 | 43篇 |
2001年 | 11篇 |
2000年 | 15篇 |
1999年 | 18篇 |
1998年 | 8篇 |
1996年 | 19篇 |
1995年 | 18篇 |
1994年 | 16篇 |
1993年 | 10篇 |
1992年 | 12篇 |
1991年 | 21篇 |
1989年 | 13篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 16篇 |
1983年 | 9篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1978年 | 8篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1974年 | 6篇 |
1973年 | 10篇 |
1972年 | 6篇 |
1969年 | 5篇 |
1966年 | 4篇 |
1964年 | 4篇 |
1962年 | 4篇 |
排序方式: 共有1105条查询结果,搜索用时 359 毫秒
41.
Energetics of nanoscale graphitic tubules 总被引:1,自引:0,他引:1
42.
Ann M. Schmiedekamp Anthony Ginnetti Brian Piccione Kevin Cannon M. Dominic Ryan 《International journal of quantum chemistry》2007,107(6):1415-1429
Octahedral, six‐coordinate Co2+ can exist in two spin states: S = 3/2 and S = 1/2. The difference in energy between high spin (S = 3/2) and low spin (S = 1/2) is dependent on both the ligand mix and coordination stereochemistry. B3LYP calculations on combinations of neutral imidazole, NH3, and H2O ligands show that low‐spin isomers are stabilized by axial H2O ligands and in structures that also include trans pairs of equatorial NH3 and protonated imidazole ligands, spin crossover structures are predicted from spin state energy differences. Occupied Co d orbitals from the DFT calculations provide a means of estimating effective ligand strength for homoleptic and mixed ligand combinations. These calculations suggest that in a labile biological system, a spin crossover environment can be created. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
43.
Wall DB Berger SJ Finch JW Cohen SA Richardson K Chapman R Drabble D Brown J Gostick D 《Electrophoresis》2002,23(18):3193-3204
Peptide mass fingerprinting by matrix-assisted laser desorption/ionization (MALDI)-mass spectrometry (MS) is one of the standard high-throughput methods for protein identification today. Traditionally this method has been based on spotting peptide mixtures onto MALDI targets. While this method works well for more abundant proteins, low-abundance proteins mixed with high-abundance proteins tend to go undetected due to ion suppression effects, instrumental dynamic range limitations and chemical noise interference. We present an alternative approach where liquid chromatography (LC) effluent is continuously collected as linear tracks on a MALDI target. In this manner the chromatographic separation is spatially preserved on the target, which enables generation of off-line LC-MS and LC-MS/MS data by MALDI. LC-MALDI sample collection provides improved sensitivity and dynamic range, spatial resolution of peptides along the sample track, and permits peptide mass mapping of low-abundance proteins in mixtures containing high-abundance proteins. In this work, standard and ribosomal protein digests are resolved and captured using LC-MALDI sample collection and analyzed by MALDI-TOF-MS. 相似文献
44.
45.
Jessica E. Waters Georg Berger Dr. Andrew J. Peel Dr. Raúl García-Rodríguez Dr. Andrew D. Bond Prof. Dominic S. Wright 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(47):12036-12040
Supramolecular main group chemistry is a developing field which parallels the conventional domain of metallo-organic chemistry. Little explored building blocks in this area are main group metal-based ligands which have the appropriate donor symmetry to build desired molecular or extended arrangements. Tris(pyridyl) main group ligands (E(py)3, E=main group metal) are potentially highly versatile building blocks since shifting the N-donor arms from the 2- to the 3-positions and 4-positions provides a very simple way of changing the ligand character from mononuclear/chelating to multidentate/metal-bridging. Here, the coordination behaviour of the first main group metal tris(4-pyridyl) ligands, E(4-py)3 (E=Sb, Bi, Ph−Sn) is explored, as well as their ability to build metal-organic frameworks (MOFs). The complicated topology of these MOFs shows a marked influence on the counter anion and on the ability of the E(4-py)3 ligands to switch coordination mode, depending on the steric and donor character of the bridgehead. This structure-directing influence of the bridgehead provides a potential building strategy for future molecular and MOF design in this area. 相似文献
46.
Weishi Du Yaokang Lv Hongliang Lu Zaihua Chen Dominic S. Wright Cheng Zhang 《中国化学快报》2017,28(12):2285-2289
An efficient and cost-effective strategy to modificate the surface of active carbon (AC), form a 3D-conductive network, and therefore improve the electrochemical performance of AC based supercapacitor was developed. 相似文献
47.
48.
Charles Brenner 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):745-748
Fhit is a tumor suppressor protein encoded at the most fragile site in the human genome that is inactivated by genetic deletions early in the development of many cancers. A member of the Histidine Triad (HIT) superfamily of nucleotide-binding proteins, Fhit binds diadenosine triphosphate (ApppA) and cleaves it to produce AMP + ADP. The His96Asn mutation of Fhit, which reduces kcat by more than a million-fold, does not reduce tumor suppressor activity in a nude mouse assay. Thus, genetic and biochemical evidence suggest that ApppA binding but not cleavage is required for tumor suppression. Crystal structures of Fhit bound to a nonhydrolyzable ApppA analog revealed that Fhit binds two substrates per dimer, presenting all of the phosphates and two of the adenosines on the surface of the protein in place of a deep, positively charged groove in the empty Fhit protein dimer. It is proposed that signaling by Fhit is mediated by presentation of nucleotide substrates to cytosolic effectors. 相似文献
49.
Dominic Thibeault Jean Legault Charles Gauthier Serge Lavoie Jimmy Bouchard 《合成通讯》2013,43(2):213-221
22(17 → 28)abeo-Lupene derivatives 5a and 6a were obtained after the acid-catalyzed E-ring expansion of 3-acetylbetulin (1a). Glycosylation of these dehydrated triterpenoids using Schmidt's trichloroacetimidate sugar donors in the presence of trimethylsilyl trifluoromethanesulfonate (TMSOTf) provided the new anhydrobetulin saponins 7b–7e in which the terminal olefin C-20(29) isomerizes to form a C-19 tetrasubstituted alkene. The preliminary cytotoxic evaluation revealed that saponins 7b–7d exhibited a moderate cytotoxic activity against A549, DLD-1, and WS1 human cell lines with IC50 ranging from 22 to 49 μM. 相似文献
50.
A. Dominic Fortes Ian G. Wood Matthias J. Gutmann 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(4):324-329
Hexaaquamagnesium(II) sulfate pentahydrate, [Mg(H2O)6]SO4·5H2O, and hexaaquamagnesium(II) chromate(II) pentahydrate, [Mg(H2O)6][CrO4]·5H2O, are isomorphous, being composed of hexaaquamagnesium(II) octahedra, [Mg(H2O)6]2+, and sulfate (chromate) tetrahedral oxyanions, SO42− (CrO42−), linked by hydrogen bonds. There are two symmetry‐inequivalent centrosymmetric octahedra: M1 at (0, 0, 0) donates hydrogen bonds directly to the tetrahedral oxyanion, T1, at (0.405, 0.320, 0.201), whereas the M2 octahedron at (0, 0, ) is linked to the oxyanion via five interstitial water molecules. Substitution of CrVI for SVI leads to a substantial expansion of T1, since the Cr—O bond is approximately 12% longer than the S—O bond. This expansion is propagated through the hydrogen‐bonded framework to produce a 3.3% increase in unit‐cell volume; the greatest part of this chemically induced strain is manifested along the b* direction. The hydrogen bonds in the chromate compound mitigate ∼20% of the expected strain due to the larger oxyanion, becoming shorter (i.e. stronger) and more linear than in the sulfate analogue. The bifurcated hydrogen bond donated by one of the interstitial water molecules is significantly more symmetrical in the chromate analogue. 相似文献