全文获取类型
收费全文 | 2371篇 |
免费 | 521篇 |
国内免费 | 791篇 |
专业分类
化学 | 1609篇 |
晶体学 | 83篇 |
力学 | 210篇 |
综合类 | 119篇 |
数学 | 428篇 |
物理学 | 1234篇 |
出版年
2024年 | 3篇 |
2023年 | 30篇 |
2022年 | 91篇 |
2021年 | 86篇 |
2020年 | 85篇 |
2019年 | 71篇 |
2018年 | 82篇 |
2017年 | 126篇 |
2016年 | 79篇 |
2015年 | 114篇 |
2014年 | 150篇 |
2013年 | 197篇 |
2012年 | 170篇 |
2011年 | 192篇 |
2010年 | 224篇 |
2009年 | 231篇 |
2008年 | 231篇 |
2007年 | 210篇 |
2006年 | 223篇 |
2005年 | 193篇 |
2004年 | 132篇 |
2003年 | 91篇 |
2002年 | 87篇 |
2001年 | 138篇 |
2000年 | 102篇 |
1999年 | 57篇 |
1998年 | 26篇 |
1997年 | 26篇 |
1996年 | 37篇 |
1995年 | 28篇 |
1994年 | 23篇 |
1993年 | 13篇 |
1992年 | 22篇 |
1991年 | 16篇 |
1990年 | 17篇 |
1989年 | 18篇 |
1988年 | 13篇 |
1987年 | 12篇 |
1986年 | 9篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1973年 | 1篇 |
1971年 | 2篇 |
1964年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有3683条查询结果,搜索用时 156 毫秒
101.
Studies on the Molecular Chain Conformation Stability of Aminated Konjac Glucomannan 总被引:2,自引:0,他引:2
Konjac glucomannan (KGM) was aminated by 2-chloroethyl-amine (CEA) as reagent so as to study the influence of concentration of CEA (based on the amount of KGM), concentration of NaOH, reaction time and temperature on the extent of amination. And the molecular simulation technology was adopted to analyze the conformation stability of aminate (AKGM). The results indicate that when the amount of CEA is higher, the extent of amination is higher. The optimum concentration of NaOH, reaction time and temperature are 10% NaOH, 70 ℃ and 45 rain, respectively. IR shows KGM is successfully aminated. The conformation of AKGM is in a random clew-like shape. 相似文献
102.
103.
The Bayesian model are established for the VaR and related risk measurements. The relationship between VaR and other risk measurements including expect shortfall, tail condition expectation and conditional value at risk are discussed. Furthermore, the Bayesian estimates and Bayesian predictors of these risk measurement are derived. Thirdly, the consistency and asymptotic normality in the exponential risk model are proved. Finally, the numerical simulation method is used to verify the convergence rate under different sample sizes. 相似文献
104.
105.
采用Z扫描方法系统的研究了KDP晶体在不同激光波长条件下的非线性光学性质.当λ=355 nm,功率密度为57.92 GW/cm2和λ=532 nm,功率密度为105.94 GW/cm2时,KDP晶体均呈现强烈的反饱和吸收和自聚焦效应,其非线性吸收系数和非线性折射率分别为6.50×10 -2cm/GW,1.17×10 -2cm/GW和8.02×10 -7cm2/GW,6. 14×10 -7cm2/GW;而在1064 nm波长,功率密度为347.95 GW/cm2时KDP晶体并未表现出明显的非线性性质.结果表明,在短波长的激光作用下,KDP晶体更容易产生非线性效应,双光子吸收是KDP晶体非线性吸收的主要机制. 相似文献
106.
107.
108.
109.
本文结合具有共轭性的一种特殊多分裂与系数矩阵的稀疏性,提出求解系数矩阵为正定矩阵的线性方程组的并行多分裂迭代法.我们的新迭代法与标准迭代法不同点有两个方面:一是在我们的多分裂方法中只要求其中之一是收敛的分裂;二是权矩阵不必预先给出.这在并行计算中是很有效的算法.最后以数值实验验证新方法的有效性和可行性. 相似文献
110.
Hongli Li Brad Bendiak William F. Siems David R. Gang Herbert H. Hill Jr. 《International Journal for Ion Mobility Spectrometry》2013,16(2):105-115
A high-throughput ion mobility mass spectrometer (IMMS) was used to rapidly separate and analyze peptides and glycopeptides derived from glycoproteins. Two glycoproteins, human α-1-acid glycoprotein and antithrombin III were digested with trypsin and subjected to electro-spray traveling wave IMMS analysis. No deglycosylation steps were performed; samples were complex mixtures of peptides and glycopeptides. Peptides and glycosylated peptides with different charge states (up to 4 charges) were observed and fell on distinguishable trend lines in 2-D IMMS spectra in both positive and negative modes. The trend line separation patterns matched between both modes. Peptide sequence was identified based on the corresponding extracted mass spectra and collision induced dissociation (CID) experiments were performed for selected compounds to prove class identification. The signal-to-noise ratio of the glycopeptides was increased dramatically with ion mobility trend line separation compared to non-trend line separation, primarily due to selection of precursor ion subsets within specific mobility windows. In addition, isomeric mobility peaks were detected for specific glycopeptides. IMMS demonstrated unique capabilities and advantages for investigating and separating glycoprotein digests in this study and suggests a novel strategy for rapid glycoproteomics studies in the future. 相似文献