全文获取类型
收费全文 | 942篇 |
免费 | 22篇 |
国内免费 | 2篇 |
专业分类
化学 | 615篇 |
晶体学 | 4篇 |
力学 | 28篇 |
数学 | 96篇 |
物理学 | 223篇 |
出版年
2021年 | 8篇 |
2020年 | 7篇 |
2017年 | 7篇 |
2016年 | 16篇 |
2015年 | 11篇 |
2014年 | 18篇 |
2013年 | 34篇 |
2012年 | 40篇 |
2011年 | 47篇 |
2010年 | 28篇 |
2009年 | 31篇 |
2008年 | 43篇 |
2007年 | 40篇 |
2006年 | 48篇 |
2005年 | 48篇 |
2004年 | 37篇 |
2003年 | 28篇 |
2002年 | 35篇 |
2001年 | 34篇 |
2000年 | 18篇 |
1998年 | 7篇 |
1997年 | 8篇 |
1996年 | 10篇 |
1995年 | 7篇 |
1994年 | 12篇 |
1993年 | 12篇 |
1992年 | 7篇 |
1990年 | 11篇 |
1989年 | 12篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 11篇 |
1984年 | 8篇 |
1983年 | 13篇 |
1982年 | 10篇 |
1981年 | 7篇 |
1980年 | 16篇 |
1979年 | 13篇 |
1978年 | 12篇 |
1977年 | 15篇 |
1976年 | 22篇 |
1975年 | 13篇 |
1974年 | 9篇 |
1973年 | 18篇 |
1972年 | 7篇 |
1970年 | 7篇 |
1969年 | 15篇 |
1967年 | 8篇 |
1966年 | 7篇 |
排序方式: 共有966条查询结果,搜索用时 31 毫秒
61.
To study the interaction of the fac-[M(CO)(3)](+) moiety (M = (99m)Tc, (188)Re) with DNA bases, we reacted [M(OH(2))(3)(CO)(3)](+) with 9-methylguanine (9-MeG), guanosine (G), and 2-deoxyguanosine (2dG). Two bases bind to the metal center via the N7 atoms. X-ray structure analysis of [(99)Tc(CH(3)OH)(9-MeG)(2)(CO)(3)](+) (4) (monoclinic, I2/a, a = 28.7533(14) A, b = 8.0631(4) A, c = 32.3600(15) A, beta = 91.543(6) degrees, V = 7499.6(6) A(3), Z = 8) and [Re(OH(2))(9-MeG)(2)(CO)(3)](+) (7) (monoclinic, P2(1)/n, a = 12.2873(11) A, b = 16.0707(13) A, c = 14.1809(16) A, beta = 103.361(12) degrees, V = 2724.4(5) A(3), Z = 4) reveals that the two bases are in a head-to-tail (HT) orientation. Kinetic studies show that the rates of substitution of the purine bases are comparable to that of one of the active forms of cisplatin. The bis-substituted complexes are generally less stable than the platinum adducts, and metalation of the bases is reversible. 相似文献
62.
Singh J Kronenthal DR Schwinden M Godfrey JD Fox R Vawter EJ Zhang B Kissick TP Patel B Mneimne O Humora M Papaioannou CG Szymanski W Wong MK Chen CK Heikes JE DiMarco JD Qiu J Deshpande RP Gougoutas JZ Mueller RH 《Organic letters》2003,5(17):3155-3158
[reaction: see text] An efficient asymmetric synthesis of the vasopeptidase inhibitor BMS-189921 was accomplished. Two short enantioselective syntheses of the common key intermediate (S)-alpha-aminoazepinone 6b were developed. Olefin 3 was converted to 6b via asymmetric hydrogenation. Alternatively, enyne 12 was converted to racemic alpha-aminoazepinone 15b, which was transformed to 6b by a practical dynamic resolution. 相似文献
63.
64.
[see reaction]. A protocol for the catalytic asymmetric vinylation of ketone enolates has been developed. Key to the success of this process was the development of new electron-rich chiral monodentate ligands. 相似文献
65.
The cd-index is a
polynomial which encodes the flag f-vector of a convex polytope. For
polytopes U and
V, we determine explicit
recurrences for computing the cd-index of the free join
and the cd-index of the
Cartesian product U x
V. As an application of these
recurrences, we prove the inequality
involving the
cd-indices of three
polytopes. 相似文献
66.
67.
Aitala EM Amato S Anjos JC Appel JA Ashery D Banerjee S Bediaga I Blaylock G Bracker SB Burchat PR Burnstein RA Carter T Carvalho HS Copty NK Cremaldi LM Darling C Denisenko K Devmal S Fernandez A Fox GF Gagnon P Gobel C Gounder K Halling AM Herrera G Hurvits G James C Kasper PA Kwan S Langs DC Leslie J Lundberg B Magnin J Massafferri A MayTal-Beck S Meadows B de Mello Neto JR Mihalcea D Milburn RH de Miranda JM Napier A Nguyen A d'Oliveira AB O'Shaughnessy K Peng KC Perera LP Purohit MV 《Physical review letters》2001,86(5):770-774
From a sample of 1172 +/- 61 D(+)-->pi(-)pi(+)pi(+) decays, we find gamma(D(+)-->pi(-)pi(+)pi(+))/gamma(D(+)-->K-pi(+)pi(+)) = 0.0311 +/- 0.0018(+0.0016)(-0.0026). Using a coherent amplitude analysis to fit the Dalitz plot of these decays, we find strong evidence that a scalar resonance of mass 478(+24)(-23) +/- 17 MeV/c(2) and width 324(+42)(-40) +/- 21 MeV/c(2) accounts for approximately half of all decays. 相似文献
68.
This paper discusses the role played by perturbed Dolbeault operators in relating the coherent sheaf and elliptic operator perspectives on the homology of projective varieties. Among the consequences are index formulas for perturbed Dolbeault operators.
69.
We present two types of Molecular Dynamics (MD) simulation for calculating the desorption rate of molecules from a surface. In the first, the molecules move freely between two surfaces, and the desorption rate is obtained either by counting the number of desorption events in a given time, or by looking at the average density of the molecules as a function of distance from the surface and then applying transition state theory (TST). In the second, the potential of mean force (PMF) for a molecule is determined as a function of distance from the surface and the desorption rate is obtained by means of TST. The methods are applied to water on the MgO(0 0 1) surface at low coverage. Classical potentials are used so that long simulations can be performed, to minimise statistical errors. The two sets of MD simulations agree well at high temperatures. The PMF method reproduces the 0 K adsorption energy of the molecule to within 5 meV, and finds that the well depth of the PMF is not linear with temperature. This implies the prefactor frequency f in the Polanyi-Wigner equation is a function of temperature, increasing at lower temperatures due to the reduction of the available configuration space associated with an adsorbed molecule compared with a free molecule. 相似文献
70.