全文获取类型
收费全文 | 1170篇 |
免费 | 32篇 |
国内免费 | 1篇 |
专业分类
化学 | 711篇 |
晶体学 | 7篇 |
力学 | 44篇 |
数学 | 78篇 |
物理学 | 363篇 |
出版年
2023年 | 10篇 |
2022年 | 18篇 |
2021年 | 21篇 |
2020年 | 17篇 |
2019年 | 28篇 |
2018年 | 14篇 |
2017年 | 21篇 |
2016年 | 38篇 |
2015年 | 34篇 |
2014年 | 30篇 |
2013年 | 69篇 |
2012年 | 64篇 |
2011年 | 85篇 |
2010年 | 46篇 |
2009年 | 36篇 |
2008年 | 52篇 |
2007年 | 45篇 |
2006年 | 50篇 |
2005年 | 44篇 |
2004年 | 31篇 |
2003年 | 30篇 |
2002年 | 27篇 |
2001年 | 26篇 |
2000年 | 11篇 |
1999年 | 18篇 |
1998年 | 11篇 |
1997年 | 8篇 |
1996年 | 12篇 |
1995年 | 13篇 |
1994年 | 14篇 |
1993年 | 20篇 |
1992年 | 15篇 |
1991年 | 16篇 |
1990年 | 12篇 |
1989年 | 9篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 15篇 |
1983年 | 16篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 13篇 |
1979年 | 11篇 |
1978年 | 10篇 |
1977年 | 15篇 |
1976年 | 10篇 |
1975年 | 10篇 |
1973年 | 6篇 |
1971年 | 5篇 |
1966年 | 5篇 |
排序方式: 共有1203条查询结果,搜索用时 15 毫秒
51.
A. Karnik S. Kailas A. Chatterjee P. Singh A. Navin D. C. Biswas D. M. Nadkarni A. Shrivastava S. S. Kapoor 《Zeitschrift für Physik A Hadrons and Nuclei》1995,351(2):195-198
The fission fragment angular distributions for the system12C +232Th have been measured in the energy range 0.97<>c.m./VB<1.22. the=" measured=" anisotropies=" have=" been=" compared=" with=" the=" predictions=" of=" the=" standard=" saddle=" point=" statistical=" model,=" using=" the=" second=" moment=" of=" the=" compound=" nucleus=" spin=" distribution=">1.22.>l2 deduced from a Wong model fit to the fission excitation function. While the measured anisotropies agree with the standard saddle point statistical model for Ec.m./VB>1.05, they are abnormally large at lower energies. This is also true for the existing measurements of16O and19F +232Th systems. Since for this system pre-equilibrium fission contributions are not expected, this anomaly indicates strong channel coupling effects leading to an increase in l2 at sub-barrier energies.The authors thank Drs. R.K. Choudhury and A. Saxena for useful discussions, Dr. R.J. Singh for making the thorium target and the Pellectron operation staff for excellent operation of the machine. 相似文献
52.
We have studied isospin symmetry violation in nuclear reactions by measuring simultaneously the cross-section of the following
two reactionsp +d →3H π+ andp +d →3He π0. The experiment was perfomed at the cooler synchrotron accelerator COSY, Jülich at several beam energies close to the correspondingη production threshold. We also have ongoing programmes onη-nucleus final-state interaction studies viap+6 Li →7 Be +η reactions, high resolution search for dibaryonic resonances and lambda-proton final state interaction studies. The experimental
details and results obtained so far are presented here 相似文献
53.
B. Sen B. Das P. Chatterjee 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,49(2):211-216
Nonlinear dust acoustic solitary waves in a dusty plasma are studied for nonzero kinematic viscosity. Sagdeev’s potential
can be obtain upto any order in ϕ. The existence of soliton solution is determined by pseudopotential approach. It is seen
that the electron inertia has a significant effect on the existence of solitary waves in presence of kinematic viscosity. 相似文献
54.
Sharvan Kumar Vikas Malik Jyoti Shukla Yogendra Kumar Deepak Bansal Prof. Dr. Ratnamala Chatterjee Prof. Dr. Pritam Mukhopadhyay 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(18):4740-4750
Organic spin-based molecular materials are considered to be attractive for the generation of functional materials with emergent optoelectronic, magnetic, or magneto-conductive properties. However, the major limitations to the utilization of organic spin-based systems are their high reactivity, instability, and propensity for dimerization. Herein, we report the synthesis, characterization, and magnetic and electronic studies of three ambient stable radical ions ( 1 a.+ , 1 b.+ , and 1 c.+ ). The radical ions 1 b.+ and 1 c.+ with BPh4− and BF4− counter anions, respectively, were synthesized in excellent yields by means of anion metathesis of 1 a.+ with Br− as its counter anion. Notably, synthesis of 1 a.+ was achieved in an ecofriendly, solvent-free protocol. The radical ions were characterized by means of single-crystal X-ray diffraction studies, which revealed the discrete nature of the radical ions and extensive hydrogen-bonding interactions within the radical ions and with the counter anions. Thus, radical ions can be organized to form infinite supramolecular arrays using weak noncovalent interactions. In addition, the Br−, BF4−, and BPh4− anions formed diverse types of anion–π interactions with the naphthalene and imide rings of the radical ions. The radical ions were characterized by means of X-band electron paramagnetic resonance (EPR) spectroscopy in solution and in the solid state. Magnetic studies revealed their paramagnetic nature in the range of 10 to 300 K. The radical ions exhibited high resistivity approaching the gigaohm (GΩ) scale. In addition, the radical ions exhibited panchromism. 相似文献
55.
Russian Journal of Organic Chemistry - A mild and efficient procedure has been developed for the synthesis of 3-amino-1-benzofurans by intramolecular cyclization of the corresponding... 相似文献
56.
Shovon Chatterjee Pritam Dey Nilimesh Das Khushubo Tiwari Dr. Tanmoy Maiti Prof. Pratik Sen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(7):1506-1510
An ultra-slow crystal growth over a period of 24 h of a newly synthesized CH3NH3Pb1/2Bi1/3I3 perovskite (MPBI) nanocrystal in non-polar toluene medium is reported here. From several spectroscopic techniques as well as from TEM analysis we found that the size of nanocrystals changes continuously with time, in spite of being capped by the ligands. Using a single molecular spectroscopic technique, we also found that this size change is not due to the stacking of nanocrystals but due to crystal growth. The notable temperature dependence and reversible nature of the nanocrystals growth is explained by the dynamic nature of the capping. The observed temperature-dependent ultra-slow growth is believed to be a pragmatic step towards controlling the size of perovskite NC in a systematic manner. 相似文献
57.
A. Banerjee S. B. Dutta Choudhury S. Chatterjee 《General Relativity and Gravitation》1992,24(9):991-999
It is shown that in the case of a spherical nonstatic fluid distribution undergoing shear-free motion the field equations in higher dimensional space-time can be reduced to a single second-order differential equation involving an arbitrary function of the radial co-ordinate. This result extends to higher dimensions a similar one obtained by Wyman and Faulkes earlier for 4D space-time. Solving this differential equation a number of new solutions is found, and the dynamical behaviour of one of the models is briefly discussed. The ansatz is later generalised to include the electromagnetic field as well. 相似文献
58.
Spectral properties and emission efficiencies of GdVO4 phosphors 总被引:2,自引:0,他引:2
M. Anitha P. Ramakrishnan A. Chatterjee G. Alexander H. Singh 《Applied Physics A: Materials Science & Processing》2002,74(2):153-162
GdVO4 with activators Eu, Dy, Sm and Bi has been synthesised by a solid-state reaction. GdVO4:Eu3+ (3%) yielded the highest quantum efficiency of 95%. Interesting energy-transfer properties have been revealed in the mixed-activator
phosphor (GdVO4:Eu3+, Sm3+) when excited in the 4f shell of Sm3+ at 408 nm. Bismuth-activated GdVO4 gives rise to a broad-band emission peaking at 525 nm in comparison to YVO4:Bi3+, which gives an emission peak at 570 nm under UV excitation. The quantum efficiency of GdVO4:Bi3+ increases gradually with bismuth concentration and reaches a maximum of 80% for a bismuth concentration of ≈0.5%. There is
a shift in the excitation band of GdVO4:Bi3+ towards longer wavelengths with increasing concentration of bismuth, which can lead to energy transfer from bismuth to europium
in a phosphor with both these activators. Heat treatment of GdVO4:Bi3+ at 1500 °C for 3–3.5 h resulted in a large percentage of bismuth being lost from the lattice as evaluated by X-ray fluorescence.
However, if a large percentage of bismuth (of the order of 3% or more) is initially added, a sufficient quantity of bismuth
can still be retained after heat treatment, which can lead to the development of ceramic scintillators for X-ray tomographic
applications. Addition of 3–5% boron gives a white GdVO4 phosphor without any chemical treatment.
Received: 27 Feruary 2001 / Accepted: 1 August 2001 / Published online: 30 October 2001 相似文献
59.
Animesh Chatterjee 《Journal of sound and vibration》2010,329(16):3325-3334
Vibration measurements offer an effective, inexpensive and fast means of non-destructive testing of structures and various engineering components. There are mainly two approaches to crack detection through vibration testing; open crack model with emphasis on changes in modal parameters and secondly, the breathing crack model focusing on nonlinear response characteristics. The open crack model based on linear response characteristics can identify the crack only at an advanced stage. Researchers have shown that a structure with a breathing crack behaves more like a nonlinear system, similar to that of a bilinear oscillator and the nonlinear response characteristics can very well be investigated to identify the presence of the crack. In the present study, the bilinear restoring force is approximated by a polynomial series and a nonlinear dynamic model of the cracked structure is developed using higher order frequency response functions. The effect of crack severity on the response harmonic amplitudes are investigated and a new procedure is suggested whereby the crack severity can be estimated through measurement of the first and second harmonic amplitudes. 相似文献
60.
ABSTRACTA low carbon high Mn, Ti microalloyed dual phase TWIP steel has been processed through cold rolling and annealing. X-ray diffraction reveals the maximum austenite (≈92%) in HRACST sample whereas, the 50CD sample shows 29% ferrite. The microstructure of HRAC and HRACST samples reveal austenite grains with annealing twins and deformation induced ferrite (DIF). The higher amount of DIF along with deformation twins form during cold deformation. Annealing at 500°C shows recovery, whereas at 700°C shows partial recrystallisation and at 900°C reveals almost full recrystallisation. TEM microstructures of the 900°C for 30?min samples reveal annealing twins with TiC particle. Strong Brass {110}<112> and Goss{110}<001> texture components are observed in HRAC, HRACST and 50CD samples. Goss Twin (GT) {113}<332> and Copper Twin (Cu-T) {552}<115> components are observed in 50CD sample. Addition of Ti results in an average grain size of 20?μm. Maximum YS (1176?MPa) and UTS (1283?MPa) values with the lowest ductility of 11% have been obtained for the 50CD sample which is related to the formation of extensive deformation twin and a higher fraction of DIF. 700°C-30?min and 700°C-60?min samples show an increase in ductility (23% and 34%, respectively) with a marginal decrease in tensile strength (1054?MPa). Annealing at 900°C shows ductility restoration up to 60% with higher tensile strength compared to HRACST sample. Ductile fracture of HRAC and HRACST samples transform to brittle fracture in the 50CD sample. Annealing at 900°C for 30?min shows ductile fracture with some (Fe, Mn)S and TiC particles. 相似文献