全文获取类型
收费全文 | 994篇 |
免费 | 29篇 |
国内免费 | 8篇 |
专业分类
化学 | 665篇 |
晶体学 | 82篇 |
力学 | 36篇 |
数学 | 145篇 |
物理学 | 103篇 |
出版年
2020年 | 11篇 |
2019年 | 11篇 |
2017年 | 5篇 |
2016年 | 20篇 |
2015年 | 27篇 |
2014年 | 8篇 |
2013年 | 46篇 |
2012年 | 44篇 |
2011年 | 52篇 |
2010年 | 34篇 |
2009年 | 32篇 |
2008年 | 42篇 |
2007年 | 54篇 |
2006年 | 45篇 |
2005年 | 56篇 |
2004年 | 43篇 |
2003年 | 25篇 |
2002年 | 40篇 |
2001年 | 8篇 |
2000年 | 10篇 |
1999年 | 16篇 |
1998年 | 10篇 |
1997年 | 13篇 |
1996年 | 12篇 |
1995年 | 10篇 |
1994年 | 8篇 |
1993年 | 12篇 |
1992年 | 13篇 |
1991年 | 19篇 |
1990年 | 21篇 |
1989年 | 11篇 |
1988年 | 9篇 |
1987年 | 12篇 |
1986年 | 11篇 |
1985年 | 16篇 |
1984年 | 22篇 |
1983年 | 17篇 |
1982年 | 16篇 |
1981年 | 18篇 |
1980年 | 11篇 |
1979年 | 12篇 |
1978年 | 14篇 |
1977年 | 11篇 |
1976年 | 16篇 |
1975年 | 15篇 |
1974年 | 10篇 |
1973年 | 11篇 |
1972年 | 12篇 |
1971年 | 7篇 |
1970年 | 9篇 |
排序方式: 共有1031条查询结果,搜索用时 15 毫秒
101.
Chan J Burke BJ Baucom K Hansen K Bio MM DiVirgilio E Faul M Murry J 《The Journal of organic chemistry》2011,76(6):1767-1774
Two new, reliable syntheses of a pyrido[2,3-d]-pyrimidine inhibitor of the CXCR3 receptor are described. A nine-step synthesis of the CXCR3 inhibitor (1) from 2-aminonicotinic acid was demonstrated on a multikilogram scale and incorporates a classic resolution to deliver the enantioenriched active pharmaceutical ingredient (API). A second synthesis of the CXCR3 inhibitor starts from (+)-(D)-Boc alanine and 2-chloronicotinic acid and utilizes a Goldberg coupling. This second synthesis, performed on a gram scale, intersects the former route at a common intermediate thereby completing a formal synthesis of the enantioenriched API in higher overall yield without the need for a resolution. 相似文献
102.
Kumari H Kline SR Schuster NJ Atwood JL 《Chemical communications (Cambridge, England)》2011,47(45):12298-12300
The stability of copper-seamed C-alkylpyrogallol[4]arene hexamers with varying chain lengths in solution has been studied using small-angle neutron scattering (SANS). The progression in diameter of spherical capsules with increasing alkyl chain lengths of copper-seamed hexamers in solution suggests both robustness as well as a close correlation between the solid phase and solution phase structures. 相似文献
103.
Tian J Ma S Thallapally PK Fowler D McGrail BP Atwood JL 《Chemical communications (Cambridge, England)》2011,47(27):7626-7628
Cucurbit[7]uril (CB[7]), in its amorphous solid state, shows one of the highest CO(2) sorption capacities among known organic porous materials at 298 K and 0.1 and 1 bar. In addition to the highest CO(2) capacity, CB[7] also shows remarkable selectivity of CO(2) over N(2) and CH(4). These properties, along with the existence of readily available precursors, indicate amorphous CB[7] might find applications in recycling CO(2) particularly considering the easy synthesis and potentially low manufacturing costs. 相似文献
104.
Tian J Thallapally P Liu J Exarhos GJ Atwood JL 《Chemical communications (Cambridge, England)》2011,47(2):701-703
A well-known organic host, tris-o-phenylenedioxycyclotriphosphazene, exists in two polymorphic guest-free forms: the thermodynamic nonporous high-density phase and the kinetic nanoporous low-density phase. Simple pressurization of the high density phase with CO(2) brings a solid-state transformation to the low density phase, resulting in significant expansion of the crystal volume by 23%. 相似文献
105.
Martin AD Boulos RA Iyer KS Sobolev AN Bond CS Atwood JL Dalgarno SJ Raston CL 《Chemical communications (Cambridge, England)》2011,47(35):9882-9884
Hirshfeld surface analysis of the 'ordered' inner phase of the molecular capsule complex, [(chloroform)(6)@C-n-butylpyrogallol[4]arene)(6)], provides insight into the intermolecular contacts and orientation of the solvent molecules. Molecular simulations show that adding two or three hydrogen molecules to the six solvent molecules is energetically favoured, and this correlates with NMR studies. 相似文献
106.
Keld Lars Bak Jerry Boatz Jack Simons 《International journal of quantum chemistry》1991,40(3):361-378
The first-order geometrical response equations for a state-averaged multiconfigurational self-consistent field (SA -MCSCF ) calculation are derived. This derivation is carried through from first principles to final working equations suited for computer implementation. The final equations are expressed such that the energies and wave functions must be known only for the internal SA -MCSCF states. In the derivation, the special but important case where two or more internal states have equal weighting factors is treated in a manner fully consistent with all other cases. Except for introducing extra equations that are straightforward to solve, the case where two or more internal states have equal weighting factors introduces no new complications. 相似文献
107.
108.
Jerry S. Kelly Wulf Gaertner Prasanta J. Pattanaik Maurice Salles 《Journal of Elasticity》1989,21(1):v-v
Editorial announcement 相似文献
109.
Hongming Zhang C. Mitchell Means N. Carlene Means Jerry L. Atwood 《Journal of chemical crystallography》1985,15(5):445-452
The title compound was prepared by the addition of A1Me3 to a suspension of 18-crown-6 inp-xylene. The large, colorless, air-sensitive crystals belong to the monoclinic space group P21/n witha=14.822(6),b=7.894(4),c=18.805(6) Å,=105.40(4)°, andD
calc=1.03 g cm–3 forZ=2. The finalR value based on 1758 observed reflections is 0.043. The molecule lies on a crystallographic inversion center and exhibits four strong Al-O bonds. The two independent Al-O distances are 1.978(3) and 2.000(3) Å. The oxygen atoms deviate from the mean plane of the crown, alternating above and below, by 0.13, 0.15, and 0.20 Å, respectively. Thep-xylene molecule is also positioned about a center of inversion. 相似文献
110.
Robin D. Rogers Jerry L. Atwood Marvin D. Rausch David W. Macomber William P. Hart 《Journal of organometallic chemistry》1982,238(1):79-85
Acetylcyclopentadienylsodium has been isolated in crystalline form as a THF adduct from a reaction between cyclopentadienylsodium and methyl acetate in THF solution. The product has been characterized by means of a single-crystal X-ray diffraction study. {[C5H4CMeO]Na·THF}n crystallizes in the monoclinic space group P21/c with unit cell parameters a 6.698(3), b 16.095(4), c 10.661(3) Å, β 92.93(3)° and Dc 1.17 g cm?3 for Z = 4. Least-squares refinement led to a final R value of 0.080 based on 661 independent observed reflections. The coordination sphere around each sodium atom consists of the oxygen atoms from two C5H4CMeO ligands, the oxygen atom of the THF molecule, and an ion contact pair between the sodium and the five ring carbon atoms of the C5H4CMeO ligand. 相似文献