全文获取类型
收费全文 | 98796篇 |
免费 | 15683篇 |
国内免费 | 11871篇 |
专业分类
化学 | 68504篇 |
晶体学 | 1177篇 |
力学 | 6626篇 |
综合类 | 904篇 |
数学 | 12244篇 |
物理学 | 36895篇 |
出版年
2024年 | 198篇 |
2023年 | 1827篇 |
2022年 | 2255篇 |
2021年 | 3167篇 |
2020年 | 3629篇 |
2019年 | 3580篇 |
2018年 | 3199篇 |
2017年 | 3027篇 |
2016年 | 4307篇 |
2015年 | 4544篇 |
2014年 | 5481篇 |
2013年 | 7241篇 |
2012年 | 8694篇 |
2011年 | 9076篇 |
2010年 | 6319篇 |
2009年 | 6389篇 |
2008年 | 6788篇 |
2007年 | 5953篇 |
2006年 | 5558篇 |
2005年 | 4699篇 |
2004年 | 3685篇 |
2003年 | 2915篇 |
2002年 | 2733篇 |
2001年 | 2383篇 |
2000年 | 2122篇 |
1999年 | 2117篇 |
1998年 | 1739篇 |
1997年 | 1529篇 |
1996年 | 1554篇 |
1995年 | 1322篇 |
1994年 | 1261篇 |
1993年 | 1068篇 |
1992年 | 930篇 |
1991年 | 793篇 |
1990年 | 679篇 |
1989年 | 564篇 |
1988年 | 437篇 |
1987年 | 405篇 |
1986年 | 360篇 |
1985年 | 343篇 |
1984年 | 220篇 |
1983年 | 202篇 |
1982年 | 157篇 |
1981年 | 124篇 |
1980年 | 89篇 |
1979年 | 66篇 |
1978年 | 63篇 |
1977年 | 63篇 |
1975年 | 62篇 |
1973年 | 62篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Stable, reproducible nanorecording on rotaxane thin films 总被引:3,自引:0,他引:3
Feng M Guo X Lin X He X Ji W Du S Zhang D Zhu D Gao H 《Journal of the American Chemical Society》2005,127(44):15338-15339
Stable, reversible conductance transitions and memory effects were observed in solid-state rotaxane-based Langmuir-Blodgett (LB) thin films. Taking advantage of the switching property, we have achieved reproducible nanometer-scale recording dots on rotaxane LB films via voltage application using a scanning tunneling microscope probe. The stable and easily controlled conductance switching makes the rotaxanes a hopeful candidate for nanorecording. 相似文献
992.
合成了一系列磷酸和二元羧酸酯化交联改性的聚乙烯醇(PVA)膜,研究了它们用于水-乙醇混合液的渗透气化分离规律。磷酸改性的PVA膜具有较大的通量,当料液浓度为50%时,通量可达1200g/m~2·hr.,分离系数α_(H_2O/EtOH)=10。丙二酸改性PVA膜在料液浓度为50%时,通量可达800g/m~2·hr.,且α_(H_2O/EtOH)=18。并作了这两种膜的通量和分离系数随料液浓度的变化曲线。草酸交联的PVA膜具有较高的分离系数,但通量很小。求出了水、乙醇及总的表现渗透活化能。 相似文献
993.
A new fluorescent compound based on calix[4] arene skeleton was synthesized.Its complexation ability with transition metal ions,such as Fe^3 ,Co^2 ,Ni^2 ,Cu^2 ,Zn^2 and Ag^ ,Was investigated by UV-vis and fluorescent spectra. 相似文献
994.
An ordinary plating solution for indium hexacyanoferrate (InHCF) thin film deposition, mainly composed of equal concentrations
of In3+ and [Fe(CN)6]3–, usually forms precipitates rapidly when either concentration is higher than few millimolar. This contributes to the plating
solution's instability. Moreover, electrodeposited capacities are limited accordingly. In this work, the plating solution's
stability and the electrodeposition of InHCF were greatly enhanced by adding a large amount of K+ and/or H+. It was found that a 10-mM plating solution added with 1 M HCl and 1 M KCl could be stored as fresh over a one-week period,
whereas an unmodified plating solution became useless within a couple of minutes. Also, such cationic additions, especially
adding H+, increased the electrodeposited capacity ca. 18 times at least, as compared with that obtained from the unmodified plating
solution. Furthermore, related enhancing mechanisms were proposed and verified. To sum up, this study offers a means for better
InHCF electrodeposition and should promote the applications of InHCF films.
Electronic Publication 相似文献
995.
996.
综述了1β-Methyl Carbapenem中间体的合成方法,重点强调了如何构筑1位β构型的甲基。参考文献37篇。 相似文献
997.
Comprehensive two-dimensional liquid chromatographic separation by means of a combination of ion-exchange chromatography (IEC)
and reversed-phase liquid chromatography (RPLC) has been realized and applied to the analysis of components of a traditional
Chinese medicine Flos Lonicera. In the first dimension the components of a Flos Lonicera extract is separated on strong anion-exchange (SAX) column according to the charge-exchange properties of the components.
In the second dimension the components are further fractionated by reversed-phase liquid chromatography (on ODS) on the basis
of their hydrophobicity. The RPLC effluent is desalted and split and the components are identified on-line by use of both
diode-array detection and mass spectrometry with atmospheric pressure chemical ionization (APCI–MS). In this way, the extract
of Flos Lonicera can be rapidly separated, desalted, and analyzed, with determination of molecular weight. More than 58 components of an extract
of Flos Lonicera were well resolved and six were tentatively identified from their UV and mass spectra. 相似文献
998.
999.
报告了143例沈阳市健康人血清中Mg、Zn、Cu、Se、Cr含量及Cu/Zn值,并指出健康人血清中Mg与Cu量正相关,Mg与Cr呈负相关,Mg与Cu/Zn值呈正相关.Zn与Cr呈正相关.Zn与Cu/Zn呈负相关.Cu与Cr呈负相关。Cu与Cu/Zn值呈负相关.Cr与Cu/Zn值呈负相关. 相似文献
1000.
薯蓣皂甙元的分光光度法测定 总被引:41,自引:0,他引:41
本文以黄姜为主要对象研究了薯蓣皂甙元的定量测定方法,以香荚兰醛-高氯酸为显色剂,冰醋酸为溶剂,使皂甙元显色,用分光光度法在波长为530nm处测定薯蓣皂甙元的含量。从植物中提取的皂甙元不需分离可直接测定。在1.00~20.00mg/L范围内呈良好的线性关系。 相似文献