全文获取类型
收费全文 | 14585篇 |
免费 | 2891篇 |
国内免费 | 2569篇 |
专业分类
化学 | 11121篇 |
晶体学 | 341篇 |
力学 | 777篇 |
综合类 | 172篇 |
数学 | 1358篇 |
物理学 | 6276篇 |
出版年
2024年 | 59篇 |
2023年 | 314篇 |
2022年 | 621篇 |
2021年 | 711篇 |
2020年 | 755篇 |
2019年 | 745篇 |
2018年 | 633篇 |
2017年 | 642篇 |
2016年 | 812篇 |
2015年 | 886篇 |
2014年 | 1067篇 |
2013年 | 1347篇 |
2012年 | 1510篇 |
2011年 | 1508篇 |
2010年 | 1116篇 |
2009年 | 1034篇 |
2008年 | 1153篇 |
2007年 | 923篇 |
2006年 | 823篇 |
2005年 | 625篇 |
2004年 | 507篇 |
2003年 | 362篇 |
2002年 | 294篇 |
2001年 | 248篇 |
2000年 | 234篇 |
1999年 | 200篇 |
1998年 | 138篇 |
1997年 | 97篇 |
1996年 | 114篇 |
1995年 | 77篇 |
1994年 | 79篇 |
1993年 | 72篇 |
1992年 | 69篇 |
1991年 | 58篇 |
1990年 | 33篇 |
1989年 | 39篇 |
1988年 | 25篇 |
1987年 | 17篇 |
1986年 | 34篇 |
1985年 | 20篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1957年 | 5篇 |
1936年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
111.
112.
1 INTRODUCTION The infinite networks constructed from transition metal complexes have attracted considerable current interest in recent years. The motivation behind this activity has been stimulated by their potential appli- cations in selective inclusion of ions, molecular re- cognition, host-guest chemistry, ion exchange, cata- lysis, electrical conductivity, magnetism, optics and so on[1~4]. It is well known that the diversity in structures and topologies of supramolecules is attri- b… 相似文献
113.
Lei JD Tong AJ 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(6):1029-1033
An integrated microchip was presented for selective recognition of Z-L-Phe-OH-NBD, using molecular imprinting technique. Molecularly imprinted polymer (MIP) were prepared by copolymerization in the presence of template molecule Z-L-Phe-OH-NBD, in which methacrylic acid and 4-vinylpyridine were used as functional monomers and ethylene dimethacrylate used as crosslinker. Imprinted polymer particles were introduced into a microchannel fabricated with a new material i.e. poly(methylvinylsiloxane) by simply rapid prototyping method. Imprinted effects were evaluated by laser-induced fluorescence (LIF) detection where the results indicated that good selective recognition for Z-L-Phe-OH-NBD in the imprinted polymer was obtained; the adsorption percentage of Z-L-Phe-OH-NBD was 61%. In contrast to conventional molecular imprinting analysis, integration shortened overall analysis time from 4h to 10 min. 相似文献
114.
115.
116.
117.
用量子化学从头算方法 ,在RHF/STO - 3G水平上 ,对 2_三氰基乙烯基蒽 (2_TCVA)分子进行了理论计算 ,优化得到了它的平衡几何构型 ,并计算了它的谐振动频率 .结果表明 :2_TCVA存在两种旋转异构体 :2_TCVA(1)和 2_TCVA(2 ) ,2_TCVA(2 )的总能量比 2_TCVA(1)的略高 .在PM3/CIS水平上计算了它们的电子光谱 ,得到了由基态到各激发态的垂直跃迁能和相应的振子强度 .研究表明 :2_TCVA(1)和 2_TCVA(2 )的强度最大的吸收波长分别为 2 4 9.72nm和 2 89.4 1nm ,2_TCVA(2 )的强度最大的吸收波长比 2_TCVA(1)的要长 .计算结果与实验结果符合得较好 相似文献
118.
Rong-Min Wang Zong-Fan Duan Yu-Feng He Zi-Qiang Lei 《Journal of molecular catalysis. A, Chemical》2006,260(1-2):280-287
A new kind of Co–Na heterodinuclear polymer complex based on Salen Schiff base and crown ether has been successfully prepared by condensation polymerization. Its catalytic behavior for aerobic oxidation of cyclohexene, alkylbenzenes and linear aliphatic olefins was studied in the absence of any solvents or reducing agents under mild conditions. The oxidation of cyclohexene catalyzed by the above catalyst proved to be a simple and efficient method for obtaining 2-cyclohexen-1-one (CO) and 2-cyclohexen-ol (OH) in a high selectivity. Kinetics of the oxidation was also investigated. The results showed that the aerobic oxidation of cyclohexene catalyzed by Salen-crown ether heterodinuclear polymer complex follows a radical chain aerobic oxidation mechanism. This oxidation system is also efficient in the oxidation of alkylbenzenes and linear aliphatic olefins, which afforded corresponding benzylic oxidation products and epoxides, respectively. 相似文献
119.
120.