全文获取类型
收费全文 | 193597篇 |
免费 | 2953篇 |
国内免费 | 395篇 |
专业分类
化学 | 106738篇 |
晶体学 | 2231篇 |
力学 | 7328篇 |
综合类 | 8篇 |
数学 | 23607篇 |
物理学 | 57033篇 |
出版年
2021年 | 1403篇 |
2020年 | 1716篇 |
2019年 | 1736篇 |
2018年 | 2351篇 |
2017年 | 2253篇 |
2016年 | 3971篇 |
2015年 | 2827篇 |
2014年 | 3634篇 |
2013年 | 9031篇 |
2012年 | 7489篇 |
2011年 | 8608篇 |
2010年 | 5889篇 |
2009年 | 5642篇 |
2008年 | 7791篇 |
2007年 | 7654篇 |
2006年 | 7068篇 |
2005年 | 6721篇 |
2004年 | 5905篇 |
2003年 | 5117篇 |
2002年 | 4970篇 |
2001年 | 5131篇 |
2000年 | 4138篇 |
1999年 | 3136篇 |
1998年 | 2697篇 |
1997年 | 2573篇 |
1996年 | 2498篇 |
1995年 | 2276篇 |
1994年 | 2310篇 |
1993年 | 2126篇 |
1992年 | 2412篇 |
1991年 | 2456篇 |
1990年 | 2306篇 |
1989年 | 2242篇 |
1988年 | 2170篇 |
1987年 | 2049篇 |
1986年 | 1988篇 |
1985年 | 2582篇 |
1984年 | 2674篇 |
1983年 | 2177篇 |
1982年 | 2357篇 |
1981年 | 2273篇 |
1980年 | 2126篇 |
1979年 | 2264篇 |
1978年 | 2425篇 |
1977年 | 2311篇 |
1976年 | 2350篇 |
1975年 | 2230篇 |
1974年 | 2298篇 |
1973年 | 2295篇 |
1972年 | 1487篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
Attila Kovács 《International journal of quantum chemistry》2020,120(1):e26051
Lanthanide dinitrogen complexes, Ln(N2) x (x = 1-8), were investigated by Density Functional Theory computations using the B3LYP exchange-correlation functional in conjunction with quasirelativistic pseudopotentials for Ln. After a recent study on the lanthanum complexes (A. Kovács, Structural Chemistry 2018 , 29, 1825), the present study aimed to probe the changes upon variously filled 4f subshells of Ln on the structures, stabilities, and bonding properties in related complexes of Nd, Ho, and Lu. The bonding properties were assessed on the basis of natural atomic charges, Ln valence orbital populations, and analysis of bonding molecular orbitals. 相似文献
22.
ABSTRACTThe Coupled-Cluster (CC) theory is one of the most successful high precision methods used to solve the stationary Schrödinger equation. In this article, we address the mathematical foundation of this theory with focus on the advances made in the past decade. Rather than solely relying on spectral gap assumptions (non-degeneracy of the ground state), we highlight the importance of coercivity assumptions – Gårding type inequalities – for the local uniqueness of the CC solution. Based on local strong monotonicity, different sufficient conditions for a local unique solution are suggested. One of the criteria assumes the relative smallness of the total cluster amplitudes (after possibly removing the single amplitudes) compared to the Gårding constants. In the extended CC theory the Lagrange multipliers are wave function parameters and, by means of the bivariational principle, we here derive a connection between the exact cluster amplitudes and the Lagrange multipliers. This relation might prove useful when determining the quality of a CC solution. Furthermore, the use of an Aubin–Nitsche duality type method in different CC approaches is discussed and contrasted with the bivariational principle. 相似文献
23.
Kazakova E. F. Dmitrieva N. E. Zvereva N. L. 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2020,94(2):341-344
Russian Journal of Physical Chemistry A - Rapidly quenched alloys of aluminum with cobalt and zirconium are investigated using a combination of means of physicochemical analysis to study the... 相似文献
24.
25.
26.
27.
28.
29.
Biodistribution study of free and microencapsulated 6‐methylcoumarin in Wistar rats by HPLC
下载免费PDF全文
![点击此处可从《Biomedical chromatography : BMC》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Aura Rocío Hernández Luis Fernando Ospina Diana Marcela Aragón 《Biomedical chromatography : BMC》2015,29(2):176-181
A sensitive, specific and reproducible HPLC method has been developed and validated for the quantitative determination of 6‐methylcoumarin (6MC) in plasma and other tissues in Wistar rats. A C18 column was used with UV detection at 321 nm and a gradient system consisting of methanol‐deionized water was used as mobile phase. The retention time for 6MC was 14.921 min and no interfering peaks were observed for any of the matrices. Linear relationships (r2 > 0.997) were obtained between the peak height ratios and the corresponding biological sample concentrations over the range 0.4–12.8 µg/mL. Precision and accuracy were evaluated; the coefficient of variation and the relative error for all of the organs were <2 and 7%, respectively. The limit of quantitation was 0.20 µg/mL for the heart and 0.30 µg/mL for the other tissues evaluated. This HPLC method was successfully used in the determination of 6MC in the biodistribution study after administration of 200 mg/kg of both 6MC‐free and 6MC‐loaded polymeric microparticles. In this study, extensive 6MC was found, in both free and microencapsulated forms, in all the organs tested. The 6MC‐free showed a range of between 1.7 and 11.5 µg/g, while the microencapsulated 6MC showed concentrations of between 6.35 and 17.7 µg/g, suggesting that 6MC improved absorption rate. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
30.