全文获取类型
收费全文 | 15180篇 |
免费 | 2823篇 |
国内免费 | 2134篇 |
专业分类
化学 | 11543篇 |
晶体学 | 252篇 |
力学 | 821篇 |
综合类 | 195篇 |
数学 | 1923篇 |
物理学 | 5403篇 |
出版年
2024年 | 40篇 |
2023年 | 389篇 |
2022年 | 557篇 |
2021年 | 723篇 |
2020年 | 814篇 |
2019年 | 792篇 |
2018年 | 659篇 |
2017年 | 625篇 |
2016年 | 797篇 |
2015年 | 936篇 |
2014年 | 1045篇 |
2013年 | 1334篇 |
2012年 | 1484篇 |
2011年 | 1450篇 |
2010年 | 1042篇 |
2009年 | 1054篇 |
2008年 | 1155篇 |
2007年 | 937篇 |
2006年 | 859篇 |
2005年 | 636篇 |
2004年 | 482篇 |
2003年 | 338篇 |
2002年 | 346篇 |
2001年 | 231篇 |
2000年 | 216篇 |
1999年 | 180篇 |
1998年 | 144篇 |
1997年 | 114篇 |
1996年 | 99篇 |
1995年 | 61篇 |
1994年 | 66篇 |
1993年 | 67篇 |
1992年 | 47篇 |
1991年 | 31篇 |
1990年 | 35篇 |
1989年 | 35篇 |
1988年 | 33篇 |
1987年 | 29篇 |
1986年 | 27篇 |
1985年 | 32篇 |
1984年 | 24篇 |
1983年 | 15篇 |
1982年 | 14篇 |
1981年 | 11篇 |
1980年 | 18篇 |
1979年 | 12篇 |
1978年 | 19篇 |
1977年 | 14篇 |
1976年 | 13篇 |
1975年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
In the inverse scattering transform (IST), the reflectionless Jost solutions are combined by their analytic properties in the complex spectrum parameter plane, and then can be shown to satisfy the two Lax equations indeed by Liouville theorem. So the corresponding soliton solutions certainly satisfy the nonlinear equation by compatibility condition. Especially the multi-soliton solutions of DNLS equation can be demonstrated in this way.
PACS Numbers: 05.45.Yv, 02.30.-f, 11.10.Ef 相似文献
102.
腺嘌呤及其β-环糊精包结物的光谱研究 总被引:4,自引:0,他引:4
通过紫外光谱的摩尔比法确定了腺嘌呤与β-环糊精(β-CD)包结物的包结比为1:1,通过紫外光谱和荧光光谱研究了腺嘌呤在酸性,中性,及碱性条件下的光谱变化及与β-CD包结物的光谱变化,分别求得了它们与β-CD包结的平衡常数。 相似文献
103.
Polyphysa peniculus was grown in artificial seawater in the presence of arsenate, arsenite, monomethylarsonate and dimethylarsinic acid. The separation and identification of some of the arsenic species produced in the cells as well as in the growth medium were achieved by using hydride generation–gas chromatography–atomic absorption spectrometry methodology. Arsenite and dimethylarsinate were detected following incubation with arsenate. When the alga was treated with arsenite, dimethylarsinate was the major metabolite in the cells and in the growth medium; trace amounts of monomethylarsonate were also detected in the cells. With monomethylarsonate as a substrate, the metabolite is dimethylarsinate. Polyphysa peniculus did not metabolize dimethylarsinic acid when it was used as a substrate. Significant amounts of more complex arsenic species, such as arsenosungars, were not observed in the cells or medium on the evidence of flow injection–microwave digestion–hydride generation–atomic absorption spectrometry methodology. Transfer of the exposed cells to fresh medium caused release of most cell–associated arsenicals to the surrounding environment. 相似文献
104.
Previous studies using dideuterium as a solute have demonstrated the importance for orientation of the interaction between the solute molecular quadrupole moment and the average electric field gradient present in liquid crystals. With the aim of learning about additional orientational mechanisms, we have studied the temperature dependence of the 2H-NMR spectra of the liquid crystal 5CB-d19 as the solute in three liquid crystal mixtures: 55 wt % 1132/EBBA, 56·5 wt % 1132/EBBA and 70 wt % 5CB/EBBA. In these mixtures, the contribution from the environment to the average electric field gradient at the 2H nucleus of dideuterium is zero. The spectra of 5CB-d19 in the mixtures 55 wt % 1132/EBBA and 56·5 wt % 1132/EBBA are equivalent, but are different from those in 70 wt % 5CB/EBBA. The spectra of 5CB in 55 wt % 1132/EBBA and 70 wt % 5CB/EBBA are analysed using two different models for the short range potential, and param eters of the models are used to compare the potentials in the different mixtures. For a given spectral splitting of the chain C1 deuteron, the reduced short range potential is the same in all three mixtures studied. The spectral differences observed are a consequence of different nematic-isotropic phase transition temperatures combined with the effect of trans/gauche-isomerization in the hydrocarbon chain. 相似文献
105.
刘浩 《数学物理学报(A辑)》2002,22(2):231-237
该文在有界星形圆型域上建立一些与双全纯星形映照有关的偏微分不等式.作为应用,给出有界星形圆型域上ε星形映照以及近似星形映照的一些充分判别条件. 相似文献
106.
107.
Sz.-Nagy's dilation theorem for a contraction on a Hilbert space has been extended by Mlak to the case of a contraction semigroup whose indices are the positive elements of a totally ordered discrete group. We generalize to this case the intertwining lifting theorem of Sz.-Nagy and Foias. Some previous interpolation results on ordered groups are obtained as consequences. 相似文献
108.
109.
110.
基于cDNA宏阵列的系统聚类分析猪发育阶段的基因表达谱 总被引:3,自引:0,他引:3
取杜洛克猪胚胎第33,45,55,65.75天的背最长肌样本.用cDNA Macroarray分析方法和聚类分析技术分析了327个EST在骨骼肌内不同发育阶段的基因表达谱.结果表明有98条EST在不同发育时期显著差异表达.第33天和第45天两阶段基因表达状态相似.第55天和第65天基因表达状态相似.而第75天的基因表达与第55天和第65天两个阶段的基因表达具有相近的聚类关系.表达状态相近,基因功能相似的基因大都被聚类在一起. 相似文献