全文获取类型
收费全文 | 6421篇 |
免费 | 925篇 |
国内免费 | 509篇 |
专业分类
化学 | 2638篇 |
晶体学 | 1152篇 |
力学 | 468篇 |
综合类 | 102篇 |
数学 | 1367篇 |
物理学 | 2128篇 |
出版年
2024年 | 6篇 |
2023年 | 65篇 |
2022年 | 134篇 |
2021年 | 179篇 |
2020年 | 195篇 |
2019年 | 151篇 |
2018年 | 119篇 |
2017年 | 178篇 |
2016年 | 282篇 |
2015年 | 217篇 |
2014年 | 348篇 |
2013年 | 462篇 |
2012年 | 363篇 |
2011年 | 486篇 |
2010年 | 442篇 |
2009年 | 437篇 |
2008年 | 469篇 |
2007年 | 474篇 |
2006年 | 446篇 |
2005年 | 360篇 |
2004年 | 336篇 |
2003年 | 273篇 |
2002年 | 190篇 |
2001年 | 159篇 |
2000年 | 179篇 |
1999年 | 138篇 |
1998年 | 129篇 |
1997年 | 128篇 |
1996年 | 73篇 |
1995年 | 62篇 |
1994年 | 62篇 |
1993年 | 47篇 |
1992年 | 42篇 |
1991年 | 48篇 |
1990年 | 35篇 |
1989年 | 26篇 |
1988年 | 26篇 |
1987年 | 16篇 |
1986年 | 13篇 |
1985年 | 16篇 |
1984年 | 11篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1973年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有7855条查询结果,搜索用时 15 毫秒
991.
Akdemir ZS Akçakaya H Kahraman MV Ceyhan T Kayaman-Apohan N Güngör A 《Macromolecular bioscience》2008,8(9):852-862
In this study, photopolymerized hydrogels of fumarated poly(ethylene glycol) diglycidyl-co- poly(ethylene glycol) diacrylate have been synthesized and modified with cell adhesion peptide, Arg-Gly-Asp (RGD). The structural and mechanical properties of the hydrogels are found to be poly(ethylene glycol) diacrylate (PEGDA) dependent. The percentage of gelation is increased from 72 to 89 wt.-% when the amount of the crosslinker co-monomer (PEGDA) in the hydrogel formulation is increased from 20 to 40 wt.-%. In the present case, the equilibrium mass swelling is decreased from 216 to 93%. The viscosities of the uncured formulations have also been measured and likewise, the results were influenced by the increasing amount of PEGDA that reduced the value from 83 to 36 cP. The compressive modulus of the prepared hydrogels was improved with the addition of the PEGDA. Cell growth experiments have been performed by comparing the properties of the hydrogels with and without RGD units. The results show that RGD units enhance the adhesion of cells to the surface of the hydrogels. SEM-EDS studies reveal that nitrogen and calcium are produced on the osteoblast-seeded surface of the scaffold within the culture time period. [Figure: see text]. 相似文献
992.
The ZnO films with two-dimensional ordered macroporous structure were successfully fabricated through hydrothermal crystal
growth of ZnO on the ZnO substrate covered with a monolayer of polystyrene (PS) spheres as template. The precursor solution
of hydrothermal crystal growth of ZnO were prepared by equimolar solution of Zn(NO3)2·6H2O and hexamethylenetramine (HMT). The confinement effect of the PS spheres template on the growth of ZnO nanorods and the
influence of sodium citrate on the crystal growth of ZnO had been studied. The film surface morphology and the preferential
growth of ZnO crystal were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. Also,
the photoluminescence spectrum of ZnO films had been measured, and the corresponding mechanism was discussed.
__________
Translated from Chemistry, 2007, 70 (8): 587–592 [译自: 化学通报] 相似文献
993.
Luisa Fattorusso 《Czechoslovak Mathematical Journal》2008,58(1):113-129
Let Ω be a bounded open subset of ℝ
n
, n > 2. In Ω we deduce the global differentiability result
for the solutions u ∈ H
1 (Ω, ℝ
n
) of the Dirichlet problem
with controlled growth and nonlinearity q = 2.
The result was obtained by first extending the interior differentiability result near the boundary and then proving the global
differentiability result making use of a covering procedure. 相似文献
994.
Michela Eleuteri 《Journal of Mathematical Analysis and Applications》2008,344(2):1120-1142
We prove regularity results for minimizers of functionals in the class , where is a fixed function and f is quasiconvex and fulfills a growth condition of the type
L−1|z|p(x)?f(x,ξ,z)?L(1+|z|p(x)), 相似文献
995.
Given a finitely generated restricted Lie algebra L over the finite field \(\mathbb{F}_q \), and n ≥ 0, denote by a n (L) the number of restricted subalgebras H ? L with \(\dim _{\mathbb{F} _q} \) L/H = n. Denote by ã n (L) the number of the subalgebras satisfying the maximality condition as well. Considering the free restricted Lie algebra L = F d of rank d ≥ 2, we find the asymptotics of ã n (F d ) and show that it coincides with the asymptotics of a n (F d ) which was found previously by the first author. Our approach is based on studying the actions of restricted algebras by derivations on the truncated polynomial rings. We establish that the maximal subalgebras correspond to the so-called primitive actions. This means that “almost all” restricted subalgebras H ? F d of finite codimension are maximal, which is analogous to the corresponding results for free groups and free associative algebras. 相似文献
996.
G. Madhurambal P. Ramasamy P. AnbuSrinivasan M. Suganthi G. Vasudevan S. C. Mojumdar 《Journal of Thermal Analysis and Calorimetry》2008,94(1):45-51
Good quality benzophenone (BP) crystals were grown by solution technique using CHCl3 as solvent by adopting slow evaporation method at room temperature. The grown crystals were subjected to various characterization
studies to analyze its purity and applications. The condensation product 2,4-dinitro phenyl hydrazone of benzophenone (DNPBP)
was prepared by adopting standard procedure. Then mixed crystal of BP and DNPBP was also grown by solution growth. Both the
condensation product and mixed crystals were characterized by UV, FTIR, 1H NMR spectra. Thermal (TG and DTA) studies have proved to be very useful techniques not only to study the thermal properties
of BP, DNPBP and mixed crystal but also to study their purity. Second harmonic generation (SHG) efficiency of the grown crystals
was determined. 相似文献
997.
Mary SS Kirupavathy SS Mythili P Srinivasan P Kanagasekaran T Gopalakrishnan R 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,71(1):10-16
The bulk single crystals of nonlinear optical material potassium pentaborate (KB5) have been grown by slow evaporation solution growth technique using water as solvent. The grown crystal was confirmed by single crystal X-ray diffraction studies. The structural perfection of the grown crystals has been analyzed by high resolution X-ray diffraction (HRXRD) studies by recording rocking curve. The photoluminescence (PL), UV-vis spectral studies were performed and the optical bandgap of the material was calculated. FTIR and FT-Raman measurements enumerate the functional groups present in the compound. The factor group analysis on KB5 reveals that there are 117 vibrational optical modes. The dielectric behavior of KB5 was investigated with different frequencies and temperatures. 相似文献
998.
An analytical relationship “the current peak height—the potential sweep rate” is derived for the three-dimensional film formation
under ohmic resistance control. The model takes into account both the changing of the coverage degree and the thickening of
the surface film. It is shown that a criterion for definition of the growth type (2D or 3D) of the surface film can be offered.
An offered model is tested for anodic oxidation of silver in sulfuric acid solution. 相似文献
999.
1000.