全文获取类型
收费全文 | 2062篇 |
免费 | 35篇 |
国内免费 | 7篇 |
专业分类
化学 | 1169篇 |
晶体学 | 33篇 |
力学 | 53篇 |
数学 | 241篇 |
物理学 | 608篇 |
出版年
2022年 | 34篇 |
2020年 | 34篇 |
2019年 | 40篇 |
2018年 | 32篇 |
2017年 | 28篇 |
2016年 | 54篇 |
2015年 | 33篇 |
2014年 | 37篇 |
2013年 | 135篇 |
2012年 | 88篇 |
2011年 | 113篇 |
2010年 | 64篇 |
2009年 | 55篇 |
2008年 | 65篇 |
2007年 | 78篇 |
2006年 | 68篇 |
2005年 | 51篇 |
2004年 | 54篇 |
2003年 | 45篇 |
2002年 | 37篇 |
2001年 | 45篇 |
2000年 | 39篇 |
1999年 | 22篇 |
1998年 | 23篇 |
1997年 | 18篇 |
1996年 | 23篇 |
1995年 | 19篇 |
1994年 | 44篇 |
1993年 | 30篇 |
1992年 | 46篇 |
1991年 | 28篇 |
1990年 | 39篇 |
1989年 | 28篇 |
1988年 | 26篇 |
1987年 | 23篇 |
1986年 | 27篇 |
1985年 | 26篇 |
1984年 | 35篇 |
1983年 | 27篇 |
1982年 | 30篇 |
1981年 | 25篇 |
1980年 | 20篇 |
1979年 | 36篇 |
1978年 | 36篇 |
1977年 | 27篇 |
1976年 | 19篇 |
1975年 | 21篇 |
1974年 | 18篇 |
1973年 | 23篇 |
1970年 | 14篇 |
排序方式: 共有2104条查询结果,搜索用时 0 毫秒
91.
Reactions of [ZnAl2(OPri)8] [A] with acetoxime in different molar ratios in refluxing anhydrous benzene, yield complexes of the type [ZnAl2(OPri)8?n{(CH3)2CNO}n] {where, n = 1–4}. All the complexes are transparent viscous/foamy solids. They were characterized by elemental analyses, FT-IR and NMR (1H, 13C {1H}) spectral studies. 27Al NMR spectrum of [ZnAl2(OPri)4{(CH3)2CNO}4] [4] in CDCl3 suggests presence of four coordination around both the aluminum atoms. IR spectra suggest that the oximato ligands bind the aluminum atoms in a side on manner in all the complexes. The ESI-mass spectrum of the representative derivative [4] suggests its monomeric nature while the thermo-gravimetric curve shows its low thermal stability. Sol–gel transformations of the precursors (A), (1), and (4) yielded nano-sized ZnAl2O4 samples (a), (b) and (c) at ~500 °C, respectively. The XRD patterns of (a), (b) and (c) indicate formation of cubic phase nano-sized zinc aluminate in all the samples. Surface morphologies of these samples were investigated by SEM images. IR spectra as well as EDX analyses indicate formation of pure zinc aluminate in all the cases. TEM image of sample (c) shows spherical (~5–8 nm) morphology. 相似文献
92.
Evan Walter Clark Spotte-Smith Peiyuan Yu Samuel M. Blau Ravi S. Prasher Anubhav Jain 《Journal of computational chemistry》2020,41(24):2137-2150
Thermal storage and transfer fluids have important applications in industrial, transportation, and domestic settings. Current thermal fluids have relatively low specific heats, often significantly below that of water. However, by introducing a thermochemical reaction to a base fluid, it is possible to enhance the fluid's thermal properties. In this work, density functional theory (DFT) is used to screen Diels–Alder reactions for use in aqueous thermal fluids. From an initial set of 52 reactions, four are identified with moderate aqueous solubility and predicted turning temperature near the liquid region of water. These reactions are selectively modified through 60 total functional group substitutions to produce novel reactions with improved solubility and thermal properties. Among the reactions generated by functional group substitution, seven have promising predicted thermal properties, significantly improving specific heat (by as much as 30.5%) and energy storage density (by as much as 4.9%) compared to pure water. 相似文献
93.
Laxmi Banjare Sant Kumar Verma Akhlesh Kumar Jain Suresh Thareja 《Journal of heterocyclic chemistry》2020,57(9):3483-3492
Aromatase is a crucial enzyme for the catalysis of aromatization reaction at the last and rate-limiting step involved in the conversion of androgenic substrates to an estrogenic substrate. A hormone-dependent breast cancer in postmenopausal woman can be cured by inhibition of estrogen biosynthesis by the help of aromatase inhibitors (AIs). The mode of interactions of flavonones with the active site of aromatase has been studied in search of potent and selective AIs as a substitute of the natural steroidal ligand. Structure-based computational approach namely, molecular docking simulations were performed to investigate the structural features of the docked complex of aromatase and flavonoid ligands. A nonsteroidal flavonoid pharmacophore showing electrostatic and steric features for selective binding within the main pocket of the catalytic active site of aromatase has been identified as an outcome of the study. The binding affinity of quercetin and isoflavone were predicted within aromatase. Isoflavone was used as a negative control to compare its binding affinities with the selected dataset. The predicted binding affinity of negative control isoflavone was in accordance with its in vitro AI efficacy. Isoflavone showed poor binding affinity and ranked last in terms of MolDock score (−86.309 kcal/molÅ) compared to dataset molecules. The generated pharmacophoric information will be helpful for the synthetic chemist to design and synthesize selective AIs with comparable binding affinity to the natural steroidal ligand. 相似文献
94.
Realizing spatiotemporal patterns out of a chemical reaction diffusion system remains an experimental challenge owing to the difficulty in overcoming the stringent condition of diffusion driven instability. Herein, by considering the spatially extended Gray-Scott model system, we have investigated how the cross diffusivities of the reactants involved influence the nature and dynamics of spatiotemporal patterns. Our study unravels that in absence of diffusion driven instability, spatially inhomogeneous patterns can be obtained for the Gray-Scott model system, and unstable time dependent patterns can be stabilized just by adjusting cross diffusivities of the reactants. Interestingly, the effect of cross diffusion in presence of the diffusion driven instability can differentially alter the speed of pattern formation, and potentially modify the nature of the spatiotemporal patterns obtained under different parametric conditions. Experimental verification of our findings may allow us to observe spatiotemporal patterns beyond the regime of classical Turing instability. 相似文献
95.
Physics of the Solid State - Temporal instability of acoustic wave is investigated in an infinite semiconductor plasma using classical hydrodynamic approach. We consider a homogeneous semiconductor... 相似文献
96.
Nonlinear Dynamics - Based on a non-classical plate theory, a nonlinear analytical model is proposed to analyze transverse vibration of thin partially cracked and submerged orthotropic plate in the... 相似文献
97.
Determination of isotopic composition of boron 总被引:4,自引:0,他引:4
K. L. Ramakumar A. R. Parab P. S. Khodade A. I. Almaula S. A. Chitambar H. C. Jain 《Journal of Radioanalytical and Nuclear Chemistry》1985,94(1):53-61
Investigations were carried out on the determination of isotopic composition of boron using Cs2BO
2
+
ion and thermal ionisation mass spectrometry. The results show distinct advantage over the normally used Na2BO
2
+
ion. 相似文献
98.
99.
R. K. Sinha A. Dhal P. Agarwal S. Kumar Monika B. B. Singh R. Kumar P. Bringel A. Neusser R. Kumar K. S. Golda R. P. Singh S. Muralithar N. Madhavan J. J. Das K. S. Thind A. K. Sinha I. M. Govil R. K. Bhowmik J. B. Gupta P. K. Joshi A. K. Jain S. C. Pancholi L. Chaturvedi 《The European Physical Journal A - Hadrons and Nuclei》2006,28(3):277-281
High-spin states in 79Rb were populated in the reaction
at E(beam) = 60 MeV. The lifetimes of the excited states of the
positive-parity yrast band and of the
negative-parity band in 79Rb were measured by the Doppler Shift Attenuation Method. The deduced transition quadrupole moments Qt are found to have a decreasing trend with rotational frequency for both the bands, consistent with those found experimentally
in neighbouring nuclei.
An erratum to this article is available at . 相似文献
100.
The low-energy physics of the fractional Hall liquid is described in terms of quasiparticles that are qualitatively distinct from electrons. We show, however, that a long-lived electronlike quasiparticle also exists in the excitation spectrum: the state obtained by the application of an electron creation operator to a fractional quantum Hall ground state has a nonzero overlap with a complex, high energy bound state containing an odd number of composite-fermion quasiparticles. The electron annihilation operator similarly couples to a bound complex of composite-fermion holes. We predict that these bound states can be observed through a conductance resonance in experiments involving a tunneling of an external electron into the fractional quantum Hall liquid. A comment is made on the origin of the breakdown of the Fermi liquid paradigm in the fractional Hall liquid. 相似文献