全文获取类型
收费全文 | 35104篇 |
免费 | 6097篇 |
国内免费 | 5844篇 |
专业分类
化学 | 27599篇 |
晶体学 | 575篇 |
力学 | 1795篇 |
综合类 | 448篇 |
数学 | 4070篇 |
物理学 | 12558篇 |
出版年
2024年 | 26篇 |
2023年 | 571篇 |
2022年 | 774篇 |
2021年 | 1055篇 |
2020年 | 1364篇 |
2019年 | 1445篇 |
2018年 | 1201篇 |
2017年 | 1224篇 |
2016年 | 1733篇 |
2015年 | 1762篇 |
2014年 | 2214篇 |
2013年 | 2741篇 |
2012年 | 3229篇 |
2011年 | 3416篇 |
2010年 | 2638篇 |
2009年 | 2563篇 |
2008年 | 2779篇 |
2007年 | 2515篇 |
2006年 | 2325篇 |
2005年 | 1879篇 |
2004年 | 1468篇 |
2003年 | 1160篇 |
2002年 | 1199篇 |
2001年 | 1028篇 |
2000年 | 867篇 |
1999年 | 674篇 |
1998年 | 481篇 |
1997年 | 396篇 |
1996年 | 358篇 |
1995年 | 334篇 |
1994年 | 307篇 |
1993年 | 248篇 |
1992年 | 185篇 |
1991年 | 176篇 |
1990年 | 145篇 |
1989年 | 108篇 |
1988年 | 93篇 |
1987年 | 70篇 |
1986年 | 73篇 |
1985年 | 63篇 |
1984年 | 27篇 |
1983年 | 29篇 |
1982年 | 21篇 |
1981年 | 14篇 |
1980年 | 9篇 |
1979年 | 17篇 |
1978年 | 8篇 |
1971年 | 4篇 |
1957年 | 4篇 |
1936年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
71.
采用密度泛函理论B3LYP方法,研究了锡苯和铅苯的[2+2],[4+2]及[4+4]二聚反应的微观机理和势能剖面,考察了Sn(Pb)原子上的2,4,6-三甲基苯基(Mes)取代基对反应势能剖面的影响.研究结果表明,所有反应均为协同过程,且大多数情况下,2个C—Sn(Pb)键同步形成.[2+2]和[4+2]反应在热力学和动力学上均比相应的[4+4]反应容易进行,而[4+2]反应在动力学上比相应的[2+2]反应有利.Sn(Pb)原子上的Mes取代基在热力学和动力学上均不利于反应的进行.铅苯的动力学稳定性与锡苯相当,但其热力学稳定性高于锡苯. 相似文献
72.
Shang‐Xiong Huang‐Fu Jin‐Ni Shen Prof. Hua Lin Prof. Ling Chen Prof. Li‐Ming Wu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(27):9809-9815
A novel type of supertetrahedral connectivity is exhibited by the 72‐atom discrete supercubooctahedron in (Cs6Cl)2Cs5[Ga15Ge9Se48] ( 1 ), which undergoes both cation and anion exchange, as revealed by unambiguous single‐crystal X‐ray diffraction data. Electronic‐structure studies helped to understand the Ge/Ga distribution. 相似文献
73.
74.
75.
76.
77.
Junshan Jing Yunfei Wu Jun Tao Huizheng Che Xiangao Xia Xiaochun Zhang Peng Yan Deming Zhao Leiming Zhang 《中国颗粒学报》2015,(1):144-154
Year-round measurements of the mass concentration and optical properties of fine aerosols(PM2.5) from June 2009 to May 2010 at an urban site in Beijing were analyzed.The annual mean values of the PM2.5 mass concentration,absorption coefficient(Ab),scattering coefficient(Sc) and single scattering albedo(SSA)at 525 nm were 67±66μg/m3,64 ±62 Mm-1,360 ±405 Mm-1 and 0.82 ±0.09,respectively.The bulk mass absorption efficiency and scattering efficiency of the PM2.5 at 525 nm were 0.78 m2/g and 5.55 m2/g,respectively.The Ab and Sc showed a similar diurnal variation with a maximum at night and a minimum in the afternoon,whereas SSA displayed an opposite diurnal pattern.Significant increases in the Ab and Sc were observed in pollution episodes caused by the accumulation of pollutants from both local and regional sources under unfavorable weather conditions.Aerosol loadings in dust events increased by several times in the spring,which had limited effects on the Ab and Sc due to the low absorption and scattering efficiency of dust particles.The frequency of haze days was the highest in autumn because of the high aerosol absorption and scattering under unfavorable weather conditions.The daily PM2.5concentration should be controlled to a level lower than 64 μg/m3 to prevent the occurrence of haze days according to its exponentially decreased relationship with visibility. 相似文献
78.
79.
80.
Dual‐signal amplification strategy for ultrasensitive chemiluminescence detection of PDGF–BB in capillary electrophoresis 下载免费PDF全文
Jun‐Tao Cao Hui Wang Shu‐Wei Ren Yong‐Hong Chen Yan‐Ming Liu 《Biomedical chromatography : BMC》2015,29(12):1866-1870
Many efforts have been made toward the achievement of high sensitivity in capillary electrophoresis coupled with chemiluminescence detection (CE‐CL). This work describes a novel dual‐signal amplification strategy for highly specific and ultrasensitive CL detection of human platelet‐derived growth factor–BB (PDGF–BB) using both aptamer and horseradish peroxidase (HRP) modified gold nanoparticles (HRP–AuNPs–aptamer) as nanoprobes in CE. Both AuNPs and HRP in the nanoprobes could amplify the CL signals in the luminol–H2O2 CL system, owing to the excellent catalytic behavior of AuNPs and HRP in the CL system. Meanwhile, the high affinity of aptamer modified on the AuNPs allows detection with high specificity. As proof‐of‐concept, the proposed method was employed to quantify the concentration of PDGF–BB from 0.50 to 250 fm with a detection limit of 0.21 fm. The applicability of the assay was further demonstrated in the analysis of PDGF–BB in human serum samples with acceptable accuracy and reliability. The result of this study exhibits distinct advantages, such as high sensitivity, good specificity, simplicity, and very small sample consumption. The good performances of the proposed strategy provide a powerful avenue for ultrasensitive detection of rare proteins in biological sample, showing great promise in biochemical analysis. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献