全文获取类型
收费全文 | 1950篇 |
免费 | 39篇 |
国内免费 | 5篇 |
专业分类
化学 | 1241篇 |
晶体学 | 32篇 |
力学 | 52篇 |
数学 | 165篇 |
物理学 | 504篇 |
出版年
2024年 | 17篇 |
2023年 | 18篇 |
2022年 | 50篇 |
2021年 | 45篇 |
2020年 | 42篇 |
2019年 | 36篇 |
2018年 | 36篇 |
2017年 | 46篇 |
2016年 | 67篇 |
2015年 | 45篇 |
2014年 | 62篇 |
2013年 | 168篇 |
2012年 | 121篇 |
2011年 | 128篇 |
2010年 | 85篇 |
2009年 | 83篇 |
2008年 | 99篇 |
2007年 | 69篇 |
2006年 | 54篇 |
2005年 | 62篇 |
2004年 | 48篇 |
2003年 | 35篇 |
2002年 | 45篇 |
2001年 | 30篇 |
2000年 | 30篇 |
1999年 | 21篇 |
1998年 | 13篇 |
1997年 | 17篇 |
1996年 | 25篇 |
1995年 | 27篇 |
1994年 | 22篇 |
1993年 | 28篇 |
1992年 | 10篇 |
1991年 | 18篇 |
1990年 | 17篇 |
1989年 | 19篇 |
1988年 | 17篇 |
1987年 | 15篇 |
1986年 | 14篇 |
1985年 | 17篇 |
1984年 | 20篇 |
1983年 | 18篇 |
1982年 | 11篇 |
1981年 | 14篇 |
1980年 | 16篇 |
1979年 | 18篇 |
1978年 | 20篇 |
1977年 | 21篇 |
1974年 | 7篇 |
1973年 | 10篇 |
排序方式: 共有1994条查询结果,搜索用时 15 毫秒
901.
Kumar Manoj Shaikh Samina Gandhi Shyamala Pandey Usha Kumar Sanjukta Dash Ashutosh 《Journal of Radioanalytical and Nuclear Chemistry》2020,324(2):879-885
Journal of Radioanalytical and Nuclear Chemistry - This study describes the fabrication of 57Co point sources utilizing the metal sorption properties of amidoxime functionalized PAN-PVDF beads.... 相似文献
902.
The quenching of toluene fluorescence by cis-6-phenyl-2-hexene has been studied to determine the rate of singlet “energy hopping” in dilute solutions of alkylbenzenes. The singlet lifetime date have been analyzed by the Stern-Volmer method to give the quasi-isoenergetic rate, kq, as 1.2 × 1010 M?1?1. The result is consistent with an excimer formation dissociation mechanism for alkylaromatic singlet energy transfer in dilute solution. 相似文献
903.
Satyendra Kumar Pandey 《Tetrahedron letters》2005,46(23):4091-4093
An efficient synthesis of (+)-α-conhydrine 1 and (−)-β-conhydrine 2 has been achieved by diastereoselective alkylation of an amino aldehyde derivative 7 with ethylmagnesium bromide or diethylzinc. 相似文献
904.
An extensive program to analyze critical systems using an improved Monte Carlo renormalization group method (IMCRG),(1) being undertaken at LANL and Cornell, is described. Here we first briefly rview the method and then list some of the topics
being investigated. 相似文献
905.
Using the recently developed route through di-t-butyl b-bilene-1,19-dicarboxylates, new syntheses of biliverdin-IXα dimethyl ester (1) and two related mono-vinyl-mono-ethyl isomers (2) and (3), are described. The two dihydro-derivatives of (1) are important in connection with biosynthetic studies of the origin of algal biliproteins. 相似文献
906.
Semiconducting materials are employed in the fabrication of a number of semiconductor devices and opto-electronic detectors
etc depending on their properties, state of purity and perfection and energy band gap values. In the present study, a latest
and novel photoacoustic spectroscopic technique has been employed for the determination of energy band gap of some semiconductors
namely CdS, CdSe, CdTe, ZnS, ZnO, Se and Si in the powder form. Values obtained have been compared with those reported by
conventional methods. 相似文献
907.
Kinetic gelation is simulated in a binary sol of different monomers in three dimensions. Copolymerization is studied with and without the help of radicals and its consequences on the sol-gel phase diagram are discussed along with the influence of functionality. 相似文献
908.
Ambrish Kumar Srivastava Neeraj Misra Sarvesh Kumar Pandey 《Journal of Cluster Science》2018,29(1):57-65
In this work, the results of DFT-based calculations on the structures, stabilities, vibrational, electronic, and hydrogen storage behavior of (CaO) n rings are presented and discussed systematically. The equilibrium ring structures of Ca–O clusters for n = 2–5 are found to be stable. Vibrational frequencies and IR intensities further support the enhanced stability with an increase in the size of Ca–O clusters. The HOMO–LUMO surfaces and their derived parameters are used to explain the electronic properties of the titled systems. For efficient hydrogen storage, metals especially, the transition metals with large cohesive energy (CE) suffer from the problem of cohesion as it is expected that the adsorption energies of metal decorated absorbents should be larger than the CEs of metal. In order to avoid this, hydrogen adsorbed directly on the absorbents is preferred. Due to relatively smaller CEs of the s-block metals, hydrogen adsorbs directly on the cluster which indeed solves the problem of cohesion. The hydrogen storage capacity of (CaO) n clusters, considering hydrogen adsorption on (CaO)4 and (CaO)5 rings is studied. The outcomes appear to give meaningful and satisfactory results. Thus the present work is expected to lead further the applications of small clusters for easy, efficient, and eco-friendly hydrogen storage. 相似文献
909.
910.
A reinvestigation of the X-ray crystal structure of malonic acid (C3H4O4) has been made in the light of some observations arising from solid-state13C NMR studies on this compound. The unit cell parameters are:a=5.156(1),b=5.341(1),c=8.407(1) Å, =71.48o (2), =76.12o (2), =85.09o (2), space group
,Z=2. The structure was solved by direct methods and refined by full-matrix least-squares refinement to a finalR value of 0.038 for 711 unique reflections withl>3. The packing of the molecules involves dimeric hydrogen bonded association of each carboxyl group with a centrosymmetrically related neighbor. The angles O–C–O (123.3o and 124.8o, respectively) for the two carboxyl groups agree qualitatively with the values predicted from a linear relationship relating the observed 22 component of the Carbon-13 NMR chemical shielding tensor for the carboxyl carbon atom to the bond angle O–C–O at the carbon atom.Contribution No. 825. 相似文献