全文获取类型
收费全文 | 402篇 |
免费 | 8篇 |
国内免费 | 3篇 |
专业分类
化学 | 189篇 |
晶体学 | 3篇 |
力学 | 12篇 |
数学 | 25篇 |
物理学 | 184篇 |
出版年
2023年 | 4篇 |
2022年 | 10篇 |
2021年 | 7篇 |
2020年 | 7篇 |
2019年 | 14篇 |
2018年 | 7篇 |
2017年 | 10篇 |
2016年 | 14篇 |
2015年 | 8篇 |
2014年 | 23篇 |
2013年 | 28篇 |
2012年 | 19篇 |
2011年 | 23篇 |
2010年 | 18篇 |
2009年 | 18篇 |
2008年 | 23篇 |
2007年 | 14篇 |
2006年 | 10篇 |
2005年 | 9篇 |
2004年 | 11篇 |
2003年 | 2篇 |
2002年 | 7篇 |
2001年 | 2篇 |
1998年 | 6篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 8篇 |
1992年 | 14篇 |
1991年 | 5篇 |
1990年 | 8篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有413条查询结果,搜索用时 31 毫秒
61.
62.
Manisha Soni Chandra Prakash Rajesh Dabur Vijay Kumar 《Applied biochemistry and biotechnology》2018,186(1):27-39
The present study reports beneficial effect of hydroxytyrosol (HT) against arsenic (As)-induced oxidative stress in the rat brain. Rats were orally administered with sodium arsenite dissolved in distilled water (25 ppm, by oral gavage) for 8 weeks or HT (10 mg/kg b. wt.) in combination with As. Results showed increase in protein oxidation and lipid peroxidation, while catalase and superoxide dismutase (SOD) activities as well as GSH content were decreased after As exposure in rat brain. Fourier transform infrared analysis showed significant alteration in peak area values that also validated the oxidative damage to lipids and proteins. In addition, As exposure caused increase in protein expression of caspase-3 and Bax, while Bcl-2 expression was downregulated resulting in translocation of cytochrome c from mitochondria to cytosol. Treatment of HT with As reversed protein oxidation, lipid peroxidation, and increased GSH content as well as catalase and SOD activities. Administration of HT also prevented translocation of cytochrome c from mitochondria and increased mitochondria/cytosol ratio of cytochrome c. Hence, treatment of HT with As improved antioxidant system and efficiently lowered the generation of oxidative stress in rat brain. 相似文献
63.
A vacuum membrane distillation (VMD) model has been developed and validated with experimental data. The model consists of an extended transport model for the VMD process and is able to predict the effects of concentration and temperature polarization on the overall process performance. To validate the model, first it was tested with few experimental case studies from literature [S. Bandini, G.G. Sarti, Heat and mass transport resistances in vacuum membrane distillation per drop, AIChE J. 45 (7) (1999) 1422–1433; K.W. Lawson, D.R. Lloyd, Membrane distillation. I. Module design and performance evaluation using vacuum membrane distillation, J. Membr. Sci. 120 (1996) 111–121; A.M. Urtiaga, G. Ruiz, I. Ortiz, Kinetic analysis of the vacuum membrane distillation of chloroform from aqueous solutions, J. Membr. Sci. 165 (2000) 99–110]. Then the VMD model has been validated with experimental data collected from the recovery of aroma compounds from black currant [R.B. Jørgensen, A.S. Meyer, C. Varming, G. Jonsson, Recovery of volatile aroma compounds from black currant juice by vacuum membrane distillation, J. Food Eng. 64 (2004) 23–31]. In this work, recovery of 12 characteristic volatile aroma compounds from black currant juice has been studied. The simulated results from the VMD model, in terms of aroma concentration in the permeate have been compared with those obtained from laboratory experiments. The validated model has been used to study the effects of various process and membrane parameters on the concentration factor. The physical properties of various aroma compounds have been predicted using group contribution method as a function of temperature. 相似文献
64.
Swarbhanu Sarkar Yeong Su Ha Nisarg Soni Gwang Il An Woonghee Lee Min Hwan Kim Phuong Tu Huynh Heesu Ahn Nikunj Bhatt Yong Jin Lee Jung Young Kim Kwon Moo Park Isao Ishii Shin‐Geol Kang Jeongsoo Yoo 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(32):9511-9516
Hydrogen sulfide (H2S) has multifunctional roles as a gas signaling molecule in living systems. However, the efficient detection and imaging of H2S in live animals is very challenging. Herein, we report the first radioisotope‐based immobilization technique for the detection, quantification, and in vivo imaging of endogenous H2S. Macrocyclic 64Cu complexes that instantly reacted with gaseous H2S to form insoluble 64CuS in a highly sensitive and selective manner were prepared. The H2S concentration in biological samples was measured by a thin‐layer radiochromatography method. When 64Cu–cyclen was injected into mice, an elevated H2S concentration in the inflamed paw was clearly visualized and quantified by Cerenkov luminescence and positron emission tomography (PET) imaging. PET imaging was also able to pinpoint increased H2S levels in a millimeter‐sized infarcted lesion of the rat heart. 相似文献
65.
Steed JW Goeta AE Lipkowski J Swierczynski D Panteleon V Handa S 《Chemical communications (Cambridge, England)》2007,(8):813-815
Templation of a daughter phase by a parent crystal results from an equilibrating mixture of two very different copper(ii) N,N',N'-trimethyltriazacyclononane complexes. 相似文献
66.
R. K. Bamezai A. Soni Z. Vakhovskaya H. Kresse 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(13):2283-2287
Two binary phase diagrams of the liquid crystals (4-n-pentylphenyl-4-n-hexyloxybenzoate (PPHB) with 4-nitrophenyl-4-n-pentylbenzoate (NPPB) and 4-n-hexyloxyphenyl-4-n-decyloxybenzoate (HPDB) with NPPB) have been studied. PPHB shows only a nematic phase where as for HPDB trimorphism, with
the SmC, SmA and nematic phases, was observed. Substance NPPB which has a strong polar nitro group is non-mesogenic one. Both
the phase diagrams show an induction and stabilization of SmA phase and appearance of the nematic state in the high concentration
range of polar component. The dielectric measurements confirm the phase transition temperatures and show changes in the short
range interaction at the phase transitions. 相似文献
67.
Vijay Singh Jun-Jie Zhu Manoj Tiwari Manish Soni Mahendra Aynayas Seok-Hee Hyun R. Narayanan Manoj Mohapatra V. Natarajan 《Journal of Non》2009,355(50-51):2491-2495
Strong blue-green light emitting Eu doped SrAl2O4 phosphor was synthesized by a low-temperature initiated, self-propagating and gas producing combustion process in a very short time (<5 min). The prepared powder was characterized by X-ray diffraction, Fourier-transform infrared spectrometry and scanning electron microscopy. The excitation spectrum shows a peak at 397 nm. Upon excitation at 397 nm, the emission spectrum exhibits a well defined broad band with maximum at 493 nm corresponding to 4f65d → 4f7 transition. Electron paramagnetic resonance (EPR) measurements at X-band showed low field signals due to Eu2+ ions in SrAl2O4:Eu. 相似文献
68.
Sheetal?Sharma Ajay Singh?VermaEmail author 《The European Physical Journal B - Condensed Matter and Complex Systems》2014,87(7):159
We report first principles calculations of solid state properties of ZnSiAs2 and ZnGeAs2 chalcopyrite semiconductors. The structural properties are calculated using a Full Potential Linearized Augmented Plane Wave method (FP-LAPW) of the Density Functional Theory (DFT). A Generalized Gradient Approximation (GGA) scheme proposed by Wu and Cohen (WC) has been chosen to calculate electronic and optical properties. Optical features such as dielectric functions, refractive indices, extinction coefficient, optical reflectivity, absorption coefficients and optical conductivities were calculated for photon energies up to 30 eV. The elastic constants at equilibrium in tetragonal structure are also determined. Temperature effect on the volume, thermal expansion, heat capacity, Debye temperature, entropy, Grüneisen parameter and bulk modulus were calculated employing the quasi-harmonic Debye model at different temperatures and pressures and the silent results were interpreted. Finally using semi-empirical relation, we determined the hardness of the materials which attributed to different covalent bonding strengths. 相似文献
69.
Simulative analysis of co-existing 2.5 G/10 G asymmetric XG-PON system using RZ and NRZ data formats
In this paper, a fiber optic communication system has been employed using co-existing 10 G/2.5 G asymmetric gigabit passive optical network (XG-PON) architecture. In this system, bidirectional optical fiber has been used for upstream and downstream data transmission. The system performance has been investigated for non-return-to-zero (NRZ) and return-to-zero (RZ) data formats operating at varying bit rates by varying the length of the fiber for analyzing the feasibility of this co-existence. The results have been compared for NRZ and RZ formats for upstream and downstream data in terms of Q value and eye opening. It is observed that RZ modulation format is superior as compared to conventional NRZ format and the faithful transmission of signal has been carried up to 90 km at 1577 nm for downstream and 140 km at 1270 nm for upstream. 相似文献
70.
N. Dixit N. Anasane M. Chavda D. Bodas H. P. Soni 《Crystal Research and Technology》2012,47(10):1105-1112
We have reported the synthesis of cubic (zinc blende) phase ZnS: Ni2+ nanoparticles using a simple wet‐chemical method. Synthesized ZnS: Ni2+ nanoparticles had been characterized by X‐ray diffraction (XRD) and Energy Dispersive X‐ray (EDX) analysis. Surface morphologies were studied using Scanning Electron Microscopy (SEM). Fourier Transform Infrared (FTIR) spectra of selected samples were also carried out to confirm the presence of capping agent on the surface of the material. We have demonstrated that various morphologies like spherical, tetrapods, sheet and long‐armed multipods are emerged by simple chemical route without any vigorous reaction parameters and changing the concentration of dopant ions only. The probable mechanism for such morphologies has also been suggested. 相似文献