全文获取类型
收费全文 | 4980篇 |
免费 | 696篇 |
国内免费 | 281篇 |
专业分类
化学 | 3648篇 |
晶体学 | 30篇 |
力学 | 38篇 |
综合类 | 25篇 |
数学 | 128篇 |
物理学 | 2088篇 |
出版年
2024年 | 12篇 |
2023年 | 34篇 |
2022年 | 92篇 |
2021年 | 105篇 |
2020年 | 117篇 |
2019年 | 119篇 |
2018年 | 132篇 |
2017年 | 152篇 |
2016年 | 153篇 |
2015年 | 159篇 |
2014年 | 162篇 |
2013年 | 414篇 |
2012年 | 352篇 |
2011年 | 254篇 |
2010年 | 201篇 |
2009年 | 258篇 |
2008年 | 276篇 |
2007年 | 367篇 |
2006年 | 308篇 |
2005年 | 296篇 |
2004年 | 267篇 |
2003年 | 240篇 |
2002年 | 203篇 |
2001年 | 193篇 |
2000年 | 180篇 |
1999年 | 172篇 |
1998年 | 132篇 |
1997年 | 104篇 |
1996年 | 101篇 |
1995年 | 78篇 |
1994年 | 64篇 |
1993年 | 68篇 |
1992年 | 49篇 |
1991年 | 40篇 |
1990年 | 25篇 |
1989年 | 21篇 |
1988年 | 12篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1977年 | 3篇 |
1974年 | 5篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有5957条查询结果,搜索用时 31 毫秒
131.
Kim WS Park M Lee DW Moon MH Lim H Lee S 《Analytical and bioanalytical chemistry》2004,378(3):746-752
Fly ash has been regarded as hazardous because of its high adsorption of toxic organic and/or inorganic pollutants. Fly ash is also known to have broad distributions of different chemical and physical properties, such as size and density. In this study, fly ash emitted from a solid waste incinerator was pre-fractionated into six sub-populations by use of gravitational SPLITT fractionation (GSF). The GSF fractions were then analyzed by sedimentation field-flow fractionation (SdFFF) and ICP–AES. SdFFF analysis showed the fly ash has a broad size distribution ranging from a few nanometers up to about 50 µm. SdFFF results were confirmed by electron microscopy. Inductively coupled plasma–atomic emission spectroscopy (ICP–AES) analysis of the GSF fractions showed the fly-ash particles contain a variety of inorganic elements including Ca, Si, Mg, Fe, and Pb. The most abundant in fly ash was Ca, followed by Si then Mg. No correlations were found between trace element concentration and particle size. 相似文献
132.
133.
L. N. Ignatieva V. G. Kuryavyi T. A. Kaidalova V. M. Bouznik A. I. Korchagin 《Journal of Structural Chemistry》2005,46(5):848-855
Electron radiation effects (40 mrad, 70 mrad, and 100 mrad) on the molecular and supramolecular structure and morphology of ultradisperse polytetrafluoroethylene obtained by the thermogas dynamic (TGD) method were studied by IR and EPR spectroscopy, X-ray phase analysis, and atomic force microscopy. Irradiation of ultradisperse powder in air leads to oxidized polymer forms due to the terminal carbonyl groups and stable peroxide radicals that appear in the structure. Fast electron radiation in doses of up to 100 mrad did not change the polymer crystallinity and particle entity, while thin films on the surface of ultradisperse polytetrafluoroethylene powder decomposed. 相似文献
134.
135.
On vicinal Si(001) surfaces, dependence of growth morphology on the applied strain direction and formation of vacancy lines from Ag-induced missing dimer vacancies are studied. Both phenomena are intimately related to the anisotropic nature of the strain field which originates from the surface dimerization. Strain relief mechanism, reflecting on the surface morphology, is shown to be different in two orthogonal directions. Normal to the steps, step-pair bunching and waving lead to formation of hillocks and pits. Along the step direction, bending of step pairs forms a cusp which later develops into a deep groove. Toward the atomic scale, the formation of the vacancy lines is driven by the short-range attractive interaction between the vacancies in adjacent dimer rows and the long-range repulsive interaction between them in the same dimer row. A full form and magnitudes of the interactions are derived from the thermally-excited wandering of the vacancy lines formed by a nominal amount of Ag depositing onto the surface. 相似文献
136.
原子吸收、原子荧光和火焰光谱分析 总被引:10,自引:0,他引:10
本文主要根据1991~1993年第一季度国内重要分析刊物所发表的文章以及在此期间重要全国性会议的主要论文,对我国原子吸收光谱法,原子荧光光谱法以及火焰发射光谱分析法的进展作一综述。文中共收集文献692篇。 相似文献
137.
138.
薛光荣 《分析测试技术与仪器》2004,10(3):176-179
运用了N2O—C2H2火焰原子吸收光谱法进行羰基镍粉钼含量的测定。介绍了钼最佳测定条件及呈良好线性范围的浓度,同时对样品消化处理条件及在测定中样品的干扰因素进行了综合考虑.该方法的相对标准偏差均小于1.0%(n=6),回收率均在97.0%~102.0%(n=6)之间.达到了实验室分析质量控制的要求. 相似文献
139.
痤疮患者血清中微量元素含量的变化 总被引:2,自引:0,他引:2
测定了52例痤疮患者血清Ca,Mg,Zn,Cu,Fe五种元素的含量。结果表明,痤疮患者血清Zn水平显著低于正常人(P<0.001),血清Ca,Mg,Cu,Fe水平则与正常人无差别(P>0.05)。部分病人口服补充锌剂后痤疮症状有所好转。提示痤疮患者应重视体内微量元素含量的变化,并做适当的补充。 相似文献
140.