全文获取类型
收费全文 | 538篇 |
免费 | 21篇 |
国内免费 | 8篇 |
专业分类
化学 | 329篇 |
晶体学 | 4篇 |
力学 | 25篇 |
数学 | 91篇 |
物理学 | 118篇 |
出版年
2024年 | 2篇 |
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 19篇 |
2020年 | 19篇 |
2019年 | 14篇 |
2018年 | 26篇 |
2017年 | 17篇 |
2016年 | 34篇 |
2015年 | 18篇 |
2014年 | 36篇 |
2013年 | 62篇 |
2012年 | 44篇 |
2011年 | 34篇 |
2010年 | 25篇 |
2009年 | 34篇 |
2008年 | 23篇 |
2007年 | 16篇 |
2006年 | 8篇 |
2005年 | 11篇 |
2004年 | 12篇 |
2003年 | 7篇 |
2002年 | 17篇 |
2001年 | 9篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1976年 | 3篇 |
1963年 | 1篇 |
1959年 | 1篇 |
1956年 | 2篇 |
排序方式: 共有567条查询结果,搜索用时 125 毫秒
1.
2.
3.
4.
A. Sanusi M. Z. A. Yahya S. Navaratnam W. J. Basirun Y. Alias N. S. Mohamed A. K. Arof 《Ionics》2003,9(3-4):253-257
In this study, lead sulphide (PbS) was prepared by the chemical bath deposition technique. The sample was characterized by
X-ray diffraction (XRD), Energy Dispersive Analysis of X-rays (EDAX) and cyclic voltammetry. EDAX spectrum shows peaks attributable
to lead and sulphur. The EDAX analysis also shows that the prepared sample is stoichiometric. Cyclic voltammetry experiments
were recorded at 100 mV·s−1 and 400 mV·s−1 scan rates. Results show that the rate controlling electrochemical reaction is electron transfer. The presence of redox waves
shows that the lithium intercalation and deintercalation can occur as a result of lattice expansion in PbS. There were no
differences in the PbS XRD data before and after the cyclic voltammetry experiments indicating that the PbS structure is not
modified upon lithium ion intercalation and deintercalation in PbS. The discharge characteristics for 35 cycles of the cell
using the LiCoO2/PbS couple is presented indicating the possible development of such materials as anode in lithium ion cells. 相似文献
5.
Ultraviolet and blue-green photoluminescence (PL) was investigated on multicrystalline silicon (mc-Si) samples chemically etched by Secco and Yang solutions. The samples were characterized by dislocation density (105-106 cm−2). The form of etched pits is triangular with Yang etch and like a honeycomb with Secco etch as observed with a scanning electron microscope (SEM). These textures of mc-Si wafers give a PL activity similar to that obtained with nanostructures of porous silicon (PS) as reported in the literature. The ultraviolet PL spectra observed with Yang etch shift to the blue-green spectrum range when applying Secco etch. In our experiments we have observed 3-5 μm diameter macro pores separated by a high density of nanowalls. These observations suggest that the origin of the PL activity are quantum dots resulting from the silicon nanocrystallites obtained after few minutes of chemical etching. 相似文献
6.
7.
8.
An isocratic ion-pair reversed-phase liquid chromatographic method has been developed for the determination of thirteen nucleotides including cyclic AMP and cyclic GMP. The resolution capability of this method was evaluated successfully using homogenates of octopus retina, the aim being to elucidate the role of nucleotides (particularly ADP and ATP) in the control of oxidative metabolism. To overcome the inherent lack of specificity of ultraviolet detection we used the coupling of liquid chromatography with mass spectrometry, via a thermospray interface, to confirm the identity of the nucleotides of interest in the biological samples. 相似文献
9.
Fathi M. A. M. Aqra 《Transition Metal Chemistry》2004,29(8):921-924
Novel seven-coordinate complexes formulated as [CuL(BH4)2], [CuL(BH4)(NO2)] and [CuL(NO2)2] (L = 1,4,7-triazacyclononane) have been prepared and structurally characterized by elemental analyses, spectroscopic data (u.v., i.r. and e.p.r.), magnetic susceptibility and conductivity measurements. The results reveal that the complexes are non-electrolytic. The coordination geometry around the copper(II) ion is a seven coordinated square pyramidal structure with three nitrogen atoms of the 1,4,7-triazacyclononane and either four hydrogen atoms of two bidentate tetrahydroborate groups or two hydrogen atoms of the bidentate tetrahydroborate group and two oxygen atoms of the bidentate nitrite group or four oxygen atoms of two bidentate nitrito groups. A cyclic voltammetric study on the complexes indicates an irreversible redox couple (CuII/CuI) in DMF, giving a voltage of ca. −0.37 V versus s.c.e. 相似文献
10.
A new complex formulated as [Cu(Pn)2(N3)(BH4)](Pn = 1,3-propanediamine) has been prepared and characterized. The results indicate that the tetrahydroborate and azide ions complete the coordination. The complex is octahedral and non-electrolytic. A cyclic voltammetric study shows that the complex exhibits a single one-electron redox couple (Cu2+/Cu+). 相似文献