全文获取类型
收费全文 | 634篇 |
免费 | 32篇 |
专业分类
化学 | 409篇 |
晶体学 | 6篇 |
力学 | 22篇 |
数学 | 53篇 |
物理学 | 176篇 |
出版年
2024年 | 2篇 |
2023年 | 6篇 |
2022年 | 18篇 |
2021年 | 11篇 |
2020年 | 15篇 |
2019年 | 19篇 |
2018年 | 15篇 |
2017年 | 12篇 |
2016年 | 24篇 |
2015年 | 21篇 |
2014年 | 28篇 |
2013年 | 50篇 |
2012年 | 51篇 |
2011年 | 51篇 |
2010年 | 22篇 |
2009年 | 31篇 |
2008年 | 29篇 |
2007年 | 28篇 |
2006年 | 15篇 |
2005年 | 29篇 |
2004年 | 28篇 |
2003年 | 17篇 |
2002年 | 22篇 |
2001年 | 11篇 |
2000年 | 12篇 |
1999年 | 8篇 |
1998年 | 9篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 6篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1963年 | 1篇 |
1961年 | 2篇 |
排序方式: 共有666条查询结果,搜索用时 218 毫秒
21.
A constructal T-shaped fin with temperature dependent thermal conductivity of fin the material exposed to both convective
and radiative environments is analyzed by Adomian decomposition method. This method provides a closed form of analytical solution
for analyzing the temperature distribution, performance and optimum design. A comparative study has been executed among the
present and published works. Unlike the published work, dependent parameters on the performance and optimization analysis
are highlighted. 相似文献
22.
23.
24.
Brian E. Young Nandini Kundu Prof. Jonathan T. Sczepanski 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(34):7981-7990
As chiral molecules, naturally occurring d -oligonucleotides have enantiomers, l -DNA and l -RNA, which are comprised of l -(deoxy)ribose sugars. These mirror-image oligonucleotides have the same physical and chemical properties as that of their native d -counterparts, yet are highly orthogonal to the stereospecific environment of biology. Consequently, l -oligonucleotides are resistant to nuclease degradation and many of the off-target interactions that plague traditional d -oligonucleotide-based technologies; thus making them ideal for biomedical applications. Despite a flurry of interest during the early 1990s, the inability of d - and l -oligonucleotides to form contiguous Watson–Crick base pairs with each other has ultimately led to the perception that l -oligonucleotides have only limited utility. Recently, however, scientists have begun to uncover novel strategies to harness the bio-orthogonality of l -oligonucleotides, while overcoming (and even exploiting) their inability to Watson–Crick base pair with the natural polymer. Herein, a brief history of l -oligonucleotide research is presented and emerging l -oligonucleotide-based technologies, as well as their applications in research and therapy, are presented. 相似文献
25.
A new exactly solvable ()-dimensional complex nonlinear wave equation exhibiting rich analytic properties has been introduced. A rogue wave (RW), localized in space–time like Peregrine RW solution, though richer due to the presence of free parameters is discovered. This freedom allows to regulate amplitude and width of the RW as needed. The proposed equation allows also an intriguing topology changing accelerated dark soliton solution in spite of constant coefficients in the equation. 相似文献
26.
27.
A number of ortho -cyclohexenyl phenols 2(a–i) have been cyclised by treatment with one equivalent of m-chloroper-oxybenzoic acid in refluxing benzene for 4 h to furnish linearly fused 1-hydroxy-1,2,3,4,4a,9a-hexahydrodibenzofurans 3(a–i) (70–80%) and bicyclic 3-hydroxy-1,3-ethanochromans 4(a–f) (10–20%). Products 3(a–i) were oxidised with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (excess) in refluxing dry xylene for 6 h to give 2,3-dihydrodibenzofuran-1 (2H)-ones 6(a–i) (85–95%). 相似文献
28.
Antimony trichloride is an efficient catalyst for the cyclization of 2-amino chalcones to the corresponding 2-aryl-2,3-dihydroquinolin-4(1H)-ones under mild reaction conditions and in almost quantitative yields. 相似文献
29.
4-Cyclohex-2-enyl-3-hydroxy-1-methylquinolin-2(1H)-one (4) was prepared in 90% yield by the thermal [3,3]sigmatropic rearrangement of 3-cyclohex-2-enyloxy-1-methylquinolin-2(1H)-one (3) in refluxing chloroben-zene for 10 h. Compound (4) was cyclised through a sequence of reactions viz. i) acetylation ii) addition of bromine and iii) treatment of the acetyl dibromo compound (6) with base to give a bicyclic product (7) in 90% yield. Treatment of compound 4 with pyridine hydro-bromide perbromide in dichloromethane at 0–5° C afforded a cyclic product 8 in excellent yield. Compound 4 when treated with cold conc. sulphuric acid at 0–5° C furnished the bicyclic product 12 in 89% yield. 相似文献
30.
Arindam Maity Debanjana ChakrabortyAbhijit Hazra Yogesh P. BharitkarSandip Kundu Prakas R. MaulikNirup B. Mondal 《Tetrahedron letters》2014
An inexpensive one-pot green methodology has been developed for the synthesis of thiazolo[2,3-a]isoquinolin-4-ium derivatives by the reaction of different derivatives of isoquinoline and 2-bromoacetophenone/bromoacetonitrile with benzoyl isothiocyanate in aqueous micellar medium. 相似文献