全文获取类型
收费全文 | 12463篇 |
免费 | 1786篇 |
国内免费 | 1938篇 |
专业分类
化学 | 10216篇 |
晶体学 | 257篇 |
力学 | 473篇 |
综合类 | 152篇 |
数学 | 1330篇 |
物理学 | 3759篇 |
出版年
2024年 | 35篇 |
2023年 | 169篇 |
2022年 | 423篇 |
2021年 | 414篇 |
2020年 | 443篇 |
2019年 | 492篇 |
2018年 | 373篇 |
2017年 | 420篇 |
2016年 | 559篇 |
2015年 | 625篇 |
2014年 | 787篇 |
2013年 | 952篇 |
2012年 | 1120篇 |
2011年 | 1167篇 |
2010年 | 894篇 |
2009年 | 855篇 |
2008年 | 1018篇 |
2007年 | 829篇 |
2006年 | 793篇 |
2005年 | 652篇 |
2004年 | 532篇 |
2003年 | 439篇 |
2002年 | 516篇 |
2001年 | 350篇 |
2000年 | 254篇 |
1999年 | 199篇 |
1998年 | 154篇 |
1997年 | 96篇 |
1996年 | 103篇 |
1995年 | 75篇 |
1994年 | 61篇 |
1993年 | 63篇 |
1992年 | 48篇 |
1991年 | 65篇 |
1990年 | 32篇 |
1989年 | 39篇 |
1988年 | 15篇 |
1987年 | 25篇 |
1986年 | 17篇 |
1985年 | 22篇 |
1984年 | 12篇 |
1983年 | 9篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1975年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
A new p-tert-butyl-calix[8]arene-bonded silica gel stationary phase (CABS) was used for the separation of some aromatic carboxylic acids by HPLC. The chromatographic behaviour of the solutes on CABS was studied in comparison with conventional ODS. The results show that the calix[8]arene-bonded phase exhibits a stronger retention and better selectivity than ODS for the aromatic carboxylic acids. The different elution order of the analytes was also observed on both packings, which show the existence of distinct retention mechanisms. According to chromatographic data, it can be concluded that the high selectivity of CABS for aromatic carboxylic acids ascribes to various interactions between CABS and the analytes, such as hydrophobic interaction, hydrogen bonding interaction, π-π interaction and inclusion interaction. 相似文献
994.
995.
[reaction: see text] Photocycloadditions of 9,10-phenanthraquinone (PQ) with oxazoles (1a and 1b) gave [4 + 4] products 2 with the O=C-C=O functionality in PQ and the 2-azadiene moiety in oxazole as 4pi addends. Photoreactions of 1-acetylisatin (IS) with 1a, 1c, and 1d gave [4 + 4] product A, which underwent further [2 + 2] reactions with another (3)IS to furnish 5. These regioselective and diastereoselective [4 + 4] photocycloadditions are rationalized by the intervening of the key conformers for ISC and bond formation of the most stable 1,6-diradical intermediates. 相似文献
996.
Min Ho Lee 《Monatshefte für Mathematik》2004,78(4):187-196
Let
t: D ?D¢\tau: {\cal D} \rightarrow{\cal D}^\prime
be an equivariant holomorphic map of symmetric domains associated to a homomorphism
r: \Bbb G ?\Bbb G¢{\bf\rho}: {\Bbb G} \rightarrow{\Bbb G}^\prime
of semisimple algebraic groups defined over
\Bbb Q{\Bbb Q}
. If
G ì \Bbb G (\Bbb Q)\Gamma\subset {\Bbb G} ({\Bbb Q})
and
G¢ ì \Bbb G¢(\Bbb Q)\Gamma^\prime \subset {\Bbb G}^\prime ({\Bbb Q})
are torsion-free arithmetic subgroups with
r (G) ì G¢{\bf\rho} (\Gamma) \subset \Gamma^\prime
, the map G\D ?G¢\D¢\Gamma\backslash {\cal D} \rightarrow\Gamma^\prime \backslash {\cal D}^\prime
of arithmetic varieties and the rationality of D{\cal D}
and
D¢{\cal D}^\prime
as well as the commensurability groups of
s ? Aut (\Bbb C)\sigma \in {\rm Aut} ({\Bbb C})
determines a conjugate equivariant holomorphic map
ts: Ds ?D¢s\tau^\sigma: {\cal D}^\sigma \rightarrow{\cal D}^{\prime\sigma}
of fs: (G\D)s ?(G¢\D¢)s\phi^\sigma: (\Gamma\backslash {\cal D})^\sigma \rightarrow(\Gamma^\prime \backslash {\cal D}^\prime)^\sigma
of . We prove that is rational if is rational. 相似文献
997.
Young Min?HanEmail author An-Hyun?KimEmail author 《Integral Equations and Operator Theory》2004,49(4):435-444
In this note we show that if either T or T* is totally *-paranormal
then Weyls theorem holds for f(T) for every f
, and also a-Weyls theorem holds for f(T) if T is totally *-paranormal. We prove that if either
T or T* is *-paranormal then the spectral mapping theorem holds for the
Weyl spectrum and for the essential approximate point spectrum. 相似文献
998.
Electronic structures of RTe2 (R=La,Ce) have been investigated by using the local spin density approximation (LSDA) and the LSDA + U (U: on-site Coulomb interaction) band methods. Both LaTe2 and CeTe2 show the very similar Fermi surface nesting features along the [100] direction, which drive the charge-density wave (CDW) instability in the Te(1) sheets. The contribution near E(F) from Ce 4f states is negligible in agreement with the measured ARPES spectra. In the semimetallic CDW-distorted RTe2, both Te vacancy and pressure induce the charge transfer from Te(1) 5p to R 5d states, producing the enhanced density of states at E(F). We suggest that these increased self-doped Te(1) 5p hole carriers are responsible for the pressure-induced superconductivity in nonstoichiometric CeTe1.82. 相似文献
999.
Micro-sized void spheres are successfully generated in a solid polymer by use of a tightly focused femtosecond laser beam from a high-repetition-rate laser oscillator. Confocal reflection images show that the void spheres are longitudinal rotational symmetric ellipsoids with a ratio of long to short axes of approximately 1.5. Layers of void spheres are then stacked to create three-dimensional diamond-lattice photonic crystals. Three gaps are observed in the [100] direction with a suppression rate of the second gap of up to approximately 75% for a 32-layer structure. The observed first- and second-order gaps shift to longer and shorter wavelengths, respectively, as the angle of incidence increases. 相似文献
1000.
A projection-type integral imaging system with an embossed screen is proposed to realize a wide viewing angle for the reconstructed image. The embossed screen is designed for virtual integral imaging in a projection-type system. It can enhance the viewing angle by increasing the effective region for each elemental image. The experimental result that verifies the merit of the proposed method is presented. 相似文献