全文获取类型
收费全文 | 3227篇 |
免费 | 87篇 |
国内免费 | 19篇 |
专业分类
化学 | 2287篇 |
晶体学 | 37篇 |
力学 | 30篇 |
数学 | 133篇 |
物理学 | 846篇 |
出版年
2022年 | 24篇 |
2020年 | 29篇 |
2019年 | 47篇 |
2018年 | 24篇 |
2017年 | 23篇 |
2016年 | 51篇 |
2015年 | 55篇 |
2014年 | 64篇 |
2013年 | 145篇 |
2012年 | 148篇 |
2011年 | 155篇 |
2010年 | 103篇 |
2009年 | 100篇 |
2008年 | 168篇 |
2007年 | 154篇 |
2006年 | 174篇 |
2005年 | 139篇 |
2004年 | 156篇 |
2003年 | 126篇 |
2002年 | 110篇 |
2001年 | 86篇 |
2000年 | 66篇 |
1999年 | 45篇 |
1998年 | 28篇 |
1997年 | 32篇 |
1996年 | 50篇 |
1995年 | 49篇 |
1994年 | 31篇 |
1993年 | 50篇 |
1992年 | 55篇 |
1991年 | 40篇 |
1990年 | 30篇 |
1989年 | 37篇 |
1988年 | 42篇 |
1987年 | 34篇 |
1986年 | 24篇 |
1985年 | 73篇 |
1984年 | 63篇 |
1983年 | 40篇 |
1982年 | 47篇 |
1981年 | 42篇 |
1980年 | 38篇 |
1979年 | 36篇 |
1978年 | 37篇 |
1977年 | 37篇 |
1976年 | 33篇 |
1975年 | 31篇 |
1974年 | 17篇 |
1973年 | 29篇 |
1966年 | 17篇 |
排序方式: 共有3333条查询结果,搜索用时 15 毫秒
71.
Yoichi M.A Yamada 《Tetrahedron》2004,60(18):4097-4105
The efficient heterogeneous Heck reaction was achieved by a new networked and supramolecular catalyst PdAS-V (1b). Employing of PdAS-V in 5.0×10−5 mol equiv. efficiently progressed the heterogeneous Heck reaction of a series of aryl iodides with acrylates, styrenes and acrylic acid. PdAS-V was successfully recycled five times without any decrease in its activity, and showed good stability in toluene and water, and hence the Heck reaction was efficiently performed in both reaction media. The use of 8.0×10−7 mol equiv. of PdAS-V resulted in the coupling product in 92% yield with the turnover number (TON) and the turnover frequency (TOF) of PdAS-V reached up to 1,150,000 and 12,000, respectively. The efficient synthesis of resveratrol was achieved via the PdAS-V-promoted Heck reaction. 相似文献
72.
Yusuke Kaminaga Takahiro Yamada Hisanori Yamane 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(7):i57-i58
A new quaternary oxide, calcium yttrium stannate, Ca0.8Y2.4Sn0.8O6, is isostructural with Mg3TeO6 (trigonal, R). The empirical formula can be expressed as (Ca0.2667Y0.7333)6(Y0.4Sn0.6)SnO12. The Ca/Y site has a distorted coordination octahedron of O atoms, with Ca/Y—O distances ranging from 2.227 (3) to 2.350 (3) Å, while the octahedra of O atoms that coordinate to the Sn and Y/Sn sites are nearly regular, with an Sn—O distance of 2.066 (2) Å and a Y/Sn—O distance of 2.147 (3) Å. 相似文献
73.
Kazutoshi Tanabe 《Journal of inclusion phenomena and macrocyclic chemistry》1984,2(1-2):267-273
Raman spectra of several organic molecules which form hydrate clathrates have been measured in aqueous solution, and the hydration structure around those molecules has been investigated from the analysis of Raman linewidth data. 相似文献
74.
Tomihiro Nishiyama Takahiro Nishikawa Fukiko Yamada 《Journal of heterocyclic chemistry》1989,26(6):1687-1690
The stereochemical properties of two 2-methyl-3-phenyl-1,3-oxazolidines and two of its 5-methyl substituted and four of its 2,5-dimethyl substituted derivatives have been investigated by pmr and cmr methods. The compounds of 2,5-dimethyl-3-phenyl-1,3-oxazolidines exist in isomeric cis and trans forms at the two methyl groups on the heterocyclic ring. 相似文献
75.
Seiji Tsuzuki Kazumasa Honda Tadafumi Uchimaru Masuhiro Mikami Kazutoshi Tanabe 《Journal of the American Chemical Society》2002,124(1):104-112
A model chemistry for the evaluation of intermolecular interaction between aromatic molecules (AIMI Model) has been developed. The CCSD(T) interaction energy at the basis set limit has been estimated from the MP2 interaction energy near the basis set limit and the CCSD(T) correction term obtained by using a medium size basis set. The calculated interaction energies of the parallel, T-shaped,and slipped-parallel benzene dimers are -1.48, -2.46, and -2.48 kcal/mol, respectively. The substantial attractive interaction in benzene dimer, even where the molecules are well separated, shows that the major source of attraction is not short-range interactions such as charge-transfer but long-range interactions such as electrostatic and dispersion. The inclusion of electron correlation increases attraction significantly. The dispersion interaction is found to be the major source of attraction in the benzene dimer. The orientation dependence of the dimer interaction is mainly controlled by long-range interactions. Although electrostatic interaction is considerably weaker than dispersion interaction, it is highly orientation dependent. Dispersion and electrostatic interactions are both important for the directionality of the benzene dimer interaction. 相似文献
76.
K. Okano A. Taniguchi S. Yamada T. Sharshar M. Shibata K. Yamauchi 《Zeitschrift für Physik A Hadrons and Nuclei》1995,352(3):243-244
The -decay of150La, the heaviest isotope of lanthanum, has been identified by observing -rays from mass separated activities obtained at KUR-ISOL. From the decay curves of 97.0 and 208.7 keV -rays in150Ce and of Ce-K X-ray, the half-life of150La has been determined as 0.51(3) s. This value is in agreement with theoretical predictions from microscopic theory. 相似文献
77.
K. Nakajima K. Yamada S. Hosoya Y. Endoh M. Greven R. J. Birgeneau 《Zeitschrift für Physik B Condensed Matter》1995,96(4):479-489
The static and dynamic spin fluctuations in the spinS=1, two-dimensional (2D) square-lattice antiferromagnet La2NiO4 have been studied over a wide temperature range using neutron scattering techniques. The spin correlations in La2NiO4 exhibit a crossover from two- to three-dimensional (3D) behavior as the Néel temperature is approached from above. Critical slowing down of the low-energy spin fluctuations is also observed just aboveT
N
. The correlation length, (T), and the static structure factor,S(0), have been measured and are compared with recent theoretical calculations for the quantum 2D Heisenberg antiferromagnet using microscopic parameters determined from previous spin-wave measurements. Good agreement for (T) is found with the exact low-temperature result of Hasenfratz and Niedermeyer provided that 2
p
s
is renormalized by 20% from the spin-wave value. 相似文献
78.
79.
80.