全文获取类型
收费全文 | 1903篇 |
免费 | 49篇 |
国内免费 | 11篇 |
专业分类
化学 | 1475篇 |
晶体学 | 13篇 |
力学 | 28篇 |
数学 | 118篇 |
物理学 | 329篇 |
出版年
2021年 | 21篇 |
2020年 | 25篇 |
2019年 | 30篇 |
2018年 | 17篇 |
2017年 | 12篇 |
2016年 | 40篇 |
2015年 | 25篇 |
2014年 | 33篇 |
2013年 | 101篇 |
2012年 | 98篇 |
2011年 | 108篇 |
2010年 | 62篇 |
2009年 | 53篇 |
2008年 | 112篇 |
2007年 | 96篇 |
2006年 | 98篇 |
2005年 | 104篇 |
2004年 | 81篇 |
2003年 | 91篇 |
2002年 | 65篇 |
2001年 | 45篇 |
2000年 | 40篇 |
1999年 | 27篇 |
1998年 | 13篇 |
1997年 | 21篇 |
1996年 | 11篇 |
1995年 | 13篇 |
1994年 | 24篇 |
1993年 | 17篇 |
1992年 | 29篇 |
1991年 | 25篇 |
1990年 | 35篇 |
1989年 | 23篇 |
1988年 | 17篇 |
1987年 | 22篇 |
1986年 | 24篇 |
1985年 | 38篇 |
1984年 | 23篇 |
1983年 | 17篇 |
1982年 | 25篇 |
1981年 | 18篇 |
1980年 | 19篇 |
1979年 | 20篇 |
1978年 | 16篇 |
1977年 | 18篇 |
1976年 | 11篇 |
1975年 | 16篇 |
1974年 | 12篇 |
1973年 | 13篇 |
1968年 | 7篇 |
排序方式: 共有1963条查询结果,搜索用时 15 毫秒
121.
122.
The transition temperatures between high- and low-spin states of the assembled spin-crossover complexes, Fe(NCX)2(bpa)2(guest) (X = S, Se, BH3; bpa = 1,2-bis(4-pyridyl)ethane; guest = biphenyl, 2-nitrobiphenyl, diphenylmethane, or 1,4-dichlorobenzene), were compared with the Mössbauer parameters. The transition temperature increases when the QS value of FeII high-spin state becomes small. The transition temperature also increases by changing the anion from NCS to NCSe and then to NCBH3. 相似文献
123.
124.
We discuss how the spectral changes of quarkonia at T
c can reflect the ‘critical’ behaviour of QCD phase transition. Starting from the temperature dependencies of the energy density
and pressure from lattice QCD calculation, we extract the temperature dependencies of the scalar and spin-2 gluon condensates
near T
c. We also parametrize these changes into the electric and magnetic condensate near T
c. While the magnetic condensate hardly changes across T
c, we find that the electric condensate increases abruptly above T
c. Similar abrupt change is also seen in the scalar condensate. Using the QCD second-order Stark effect and QCD sum rules,
we show that these sudden changes induce equally abrupt changes in the mass and width of J/ψ, both of which are larger than 100 MeV at slightly above T
c.
相似文献
125.
Toriya S Tamura Y Takei T Fuji M Watanabe T Chikazawa M 《Journal of colloid and interface science》2002,255(1):171-176
The silica-pillared derivatives from kanemite (NaHSi(2)O(5).3H(2)O) were prepared by intercalation of dialkyldimethylammonium (DADMA) ion and pillaring with tetraethylorthosilicate. The formation of silica pillars between the silicate sheets was demonstrated by X-ray diffraction, (29)Si CP/MAS NMR, and TEM observation. The basal spacing depended on the chain length of DADMA. Nitrogen adsorption study showed that the specific surface area was enlarged over 1000 m(2) g(-1) by the pillaring and that the pore size was in the micropore region. Water and benzene adsorption isotherms revealed that the surface properties of the pillared derivatives show hydrophobic character. 相似文献
126.
Application of a modified Polonovski reaction for serratinine (1) resulted in generation of serratezomine A (2) with a novel seco-serratinine-type skeleton recently isolated from the club moss Lycopodium serratum var. serratum. This biomimetic transformation supports a biogenetic pathway proposed for serratezomine A (2). The absolute stereochemistry of serratezomine A (2) was established by an induced exciton chirality and modified Mosher methods. 相似文献
127.
Selective shielding of one side of the pyridinium face by way of intramolecular cation-pi complex formation enabled nucleophiles to attack only from the non-shielded side, and consequently, chiral 1,4-dihydropyridines were produced stereoselectively with up to 99% de. The structure of the cation-pi complex was elucidated by 1H NMR studies and X-ray analysis. 相似文献
128.
The relationship among the Wigner crystal, charge ordering, and the Mott insulator is studied by the path-integral renormalization group method in two-dimensional systems with long-range Coulomb interaction. In contrast to the insensitivity of the Hartree-Fock results, the stability of the solid drastically decreases with the decrease in the lattice commensurability. The transition to liquid occurs at the electron gas parameter r(s) approximately 2 for the filling n=1/2, showing a large reduction from r(s) approximately 35 in the continuum limit. A correct account of quantum fluctuations is crucial to understanding the charge-order stability generally observed only at simple fractional fillings and the nature of quantum liquids away from them. 相似文献
129.
A system of q-Painlevé type equations with multi-time variables t
1,...,t
M
is obtained as a similarity reduction of the N-reduced q-KP hierarchy. This system has affine Weyl group symmetry of type
. Its rational solutions are constructed in terms of q-Schur functions. 相似文献
130.
Hashi K Shimizu T Goto A Kiyoshi T Matsumoto S Wada H Fujito T Hasegawa K Yoshikawa M Miki T Ito S Hamada M Hayashi S 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2002,156(2):318-321
We have developed a 920-MHz NMR system and performed the proton NMR measurement of H(2)O and ethylbenzene using the superconducting magnet operating at 21.6 T (920 MHz for proton), which is the highest field produced by a superconducting NMR magnet in the persistent mode. From the NMR measurements, it is verified that both homogeneity and stability of the magnet have a specification sufficient for a high resolution NMR. 相似文献