全文获取类型
收费全文 | 2729篇 |
免费 | 399篇 |
国内免费 | 315篇 |
专业分类
化学 | 1848篇 |
晶体学 | 104篇 |
力学 | 160篇 |
综合类 | 27篇 |
数学 | 13篇 |
物理学 | 1291篇 |
出版年
2024年 | 3篇 |
2023年 | 15篇 |
2022年 | 51篇 |
2021年 | 62篇 |
2020年 | 85篇 |
2019年 | 91篇 |
2018年 | 86篇 |
2017年 | 74篇 |
2016年 | 113篇 |
2015年 | 118篇 |
2014年 | 113篇 |
2013年 | 369篇 |
2012年 | 178篇 |
2011年 | 181篇 |
2010年 | 137篇 |
2009年 | 147篇 |
2008年 | 168篇 |
2007年 | 164篇 |
2006年 | 196篇 |
2005年 | 117篇 |
2004年 | 112篇 |
2003年 | 118篇 |
2002年 | 131篇 |
2001年 | 89篇 |
2000年 | 80篇 |
1999年 | 68篇 |
1998年 | 52篇 |
1997年 | 38篇 |
1996年 | 40篇 |
1995年 | 37篇 |
1994年 | 29篇 |
1993年 | 21篇 |
1992年 | 34篇 |
1991年 | 20篇 |
1990年 | 9篇 |
1989年 | 8篇 |
1988年 | 10篇 |
1987年 | 12篇 |
1986年 | 13篇 |
1985年 | 11篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1973年 | 3篇 |
1972年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有3443条查询结果,搜索用时 31 毫秒
191.
《Arabian Journal of Chemistry》2020,13(7):6044-6055
The corrosion of AZ91D magnesium alloy has received extensive attention due to the continuous expansion of its application field in recent years. However, the corrosion of AZ91D magnesium alloy in distilled water is relatively few. In this paper, the corrosion behavior of AZ91D magnesium alloy was studied in distilled water by electrochemical tests in combination with weight loss and surface analysis methods. The results indicated that the corrosion rate of AZ91D magnesium alloy increased with the increase of temperature and immersion time. The increase of the corrosion rate of AZ91D magnesium alloy with the increase of immersion time might be attributed to the damage of the structure of corrosion product film by hydrogen evolution, significantly accelerating the anodic process of AZ91D magnesium alloy. It was interesting that, in distilled water, the EIS of AZ91D magnesium alloy excluded an inductive arc in the low frequency region, which indicated that there was no the adsorption and desorption of aggressive ions or the damage and repair of film. The corrosion product film of AZ91D magnesium alloy in distilled water was composed of a compact inner corrosion product film and a loose outer corrosion product film. 相似文献
192.
Dwight W. Chasar 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4):149-154
Abstract The reaction of 2,6-di-t-butyl-4-methylphenylphosphorodichloridite with α-diketones in the presence of magnesium metal affords modest yields of 1,3,2-dioxaphospholenes. This may be the first evidence for the existence of the monocoordinate aryloxyphosphinidene intermediate, ROP. 相似文献
193.
A new method for the spectrofluorimetric determination of indium by formation of a fluorescent 1:1 complex with 1,2,4-trihydroxyanthraquinone is proposed. The complex is formed in a mixed, 60:40 v/v acetone-water medium at pH 3.8 provided by an acetic acid-sodium acetate buffer. The calibration graph is linear between 10 and 600 ng/ml. The effect of potential interferents on the determination was assessed and the proposed method was applied to the determination of indium in synthetic samples. 相似文献
194.
195.
Po‐Sheng Chen Yi‐Chang Liu Chia‐Her Lin Bao‐Tsan Ko 《Journal of polymer science. Part A, Polymer chemistry》2010,48(16):3564-3572
Two novel sulfonate phenol ligands—3,3′‐di‐tert‐butyl‐2′‐hydroxy‐5,5′,6,6′‐tetramethyl‐biphenyl‐2‐yl 4‐X‐benzenesulfonate (X?CF3, LCF3 ‐H, and X?OCH3, LOMe ‐H)—were prepared through the sulfonylation of 3,3′‐di‐tert‐butyl‐5,5′,6,6′‐tetramethylbiphenyl‐2,2′‐diol with the corresponding 4‐substituted benzenesulfonyl chloride (1 equiv.) in the presence of excess triethylamine. Magnesium (Mg) complexes supported by sulfonate phenoxide ligands were synthesized and characterized structurally. The reaction of MgnBu2 with L‐H (2 equiv.) produces the four‐coordinated monomeric complexes ( LCF3 )2Mg ( 1 ) and ( LOMe )2Mg ( 2 ). Complexes 1 and 2 are efficient catalysts for the ring‐opening polymerization of ε‐caprolactone (ε‐CL) and trimethylene carbonate (TMC) in the presence of 9‐anthracenemethanol; complex 1 catalyzes the polymerization of ε‐CL and TMC in a controlled manner, yielding polymers with the expected molecular weights and narrow polydispersity indices (PDIs). In ε‐CL polymerization, the activity of complex 1 is greater than that of complex 2 , likely because of the greater Lewis acidity of Mg2+ metal caused by the electron‐withdrawing substitute trifluoromethyl (? CF3) at the 4‐position of the benzenesulfonate group. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3564–3572, 2010 相似文献
196.
197.
P. T. Jochym K. Parlinski A. M. Oleś 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(2):173-179
The magnetization distribution, its energetic characterization by the
interlayer coupling constants and lattice dynamics of (001)-oriented
Fe/Pt multilayers are investigated using density functional theory
combined with the direct method to determine phonon frequencies.
It is found that ferromagnetic order between consecutive Fe layers is
favoured, with the enhanced magnetic moments at the
interface. The bilinear and biquadratic coupling coefficients between Fe
layers are shown to saturate fast with increasing thickness of
nonmagnetic Pt layers which separate them. The phonon calculations
demonstrate a rather strong dependence of partial iron phonon
densities of states on the actual position of Fe monolayer
in the multilayer structure. 相似文献
198.
Pd80+x
Si20−x
(x = 0, 1, and 2) binary metallic glasses with the diameter ranging from 7 to 8 mm were prepared by a combination of fluxing
and water quenching or air cooling. Thermal analysis results show that with increasing Si content, the glass transition temperature
T
g, the initial crystallization temperature T
x and the onset crystallization temperature T
p of Pd-Si binary glassy alloys increase. Moreover, the supercooled liquid region reaches 61 K. It indicates that Pd-Si binary
alloys possess large glass forming ability, which can be greatly improved by fluxing treatment.
Supported by the National Basic Research Program of China (Grant No. 2007CB613905) and the National Natural Science Foundation
of China (Grant Nos. 50671050 and 50431030) 相似文献
199.
The thermodynamics structural relaxation of Fe73Cu1.5Nd3Si13.5B9 amorphous alloy from room temperature to 400°C has been investigated by measuring the structure factor with in situ X-ray diffraction. The structural information of the atomic configuration such as radial distribution function (RDF) and
neighbor atomic distance was gained by Fourier transformation. The research result shows that the amorphous structure remains
stable in the temperature range of 30 to 400°C but exhibits distinct changes in local atomic configuration with the increase
of temperature. The quantitative determination of the neighbor atomic distance suggests that the degree of short-range order
changes by the temperature altering the second nearest neighbor local atomic configuration of the amorphous when structural
relaxation occurs.
Supported by the Natural Science Foundation of Hebei Province of China (Grant No. A2007000296), the National Natural Science
Foundation of China (Grant No. 50731005), SKPBRC (Grant Nos. 2007CB616915 and 2006CB605201), and PCSIRT (Grant No. IRT0650) 相似文献
200.