全文获取类型
收费全文 | 694篇 |
免费 | 19篇 |
国内免费 | 3篇 |
专业分类
化学 | 320篇 |
晶体学 | 11篇 |
力学 | 9篇 |
数学 | 44篇 |
物理学 | 332篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 8篇 |
2019年 | 18篇 |
2018年 | 16篇 |
2017年 | 9篇 |
2016年 | 19篇 |
2015年 | 15篇 |
2014年 | 21篇 |
2013年 | 55篇 |
2012年 | 32篇 |
2011年 | 47篇 |
2010年 | 25篇 |
2009年 | 33篇 |
2008年 | 38篇 |
2007年 | 31篇 |
2006年 | 33篇 |
2005年 | 27篇 |
2004年 | 22篇 |
2003年 | 16篇 |
2002年 | 22篇 |
2001年 | 12篇 |
2000年 | 9篇 |
1999年 | 7篇 |
1998年 | 11篇 |
1997年 | 4篇 |
1996年 | 19篇 |
1995年 | 18篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1992年 | 15篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 7篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1983年 | 14篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 8篇 |
1979年 | 7篇 |
1978年 | 9篇 |
1977年 | 2篇 |
1975年 | 4篇 |
1958年 | 1篇 |
1938年 | 2篇 |
排序方式: 共有716条查询结果,搜索用时 15 毫秒
21.
D. Ghosh J. Roy M. Basu A. Bhattacharjee T. Guhathakurta K. Sengupta 《Czechoslovak Journal of Physics》1982,32(11):1221-1224
This paper presents an extensive study on the dependence of the mean number of the fast fragment of the target nucleus n
g on the incident beam energy in proton-nucleus interaction in emulsion in the range 6·2E
0400 GeV/c. It has been observed that n
g decreases in the range 6·2E
0200 GeV/c, then increases and attains an approximately steady value up to 400 GeV/c. It is very difficult to explain this behaviour with the help of the existing nuclear production models.The author would like to thank Prof A. J. Herz (CERN), Prof. K. D. Tolostov (Dubna, U.S.S.R.), Prof. P. L. Jain (State University of New York, U.S.A.), Prof. G. Giacomelly (Italy) for kindly supplying the exposed emulsion plates. 相似文献
22.
The 4-hydrazinobenzyl alcohol ( 3 was prepared (58%)) by diiobutylaluminiumhydride reduction of methyl 4-hydrazinobenzoate ( 4 ), whereas LiA1H4 or LiBh4 reduction of 4 proceeded further to yield (via intermediate 3 ) (4-tolyl)hydrazine ( 5 ). The alcohol 3 was stable under O2-free conditions and exhibited no tendency to eliminate H2O, neither thermally nor with H+ catalysis. Oxidation of 3 with SeO2 yielded 4-(hydroxymethyl)benzine-diazonium ion ( 8 ), identified by its azo coupling product 9 with 2-naphthol. Condensation of 3 with 1-benzyl 5-Hydrogen N-(benzyloxycarbonyl)-L-glutamate ( 10 ) in presence of dicyclohexylcarbodiimide afforded 81% of N2-(benzyloxycarbonyl)-L- glutamic acid 1-(benzyl-ester) 5-{2-[4-(hydroxymethyl)phenyl]hydrazide} ( 11 ) which upon controlled hydrogenolysis (quinoline-sulfur-poisoned Pd/C catalyst) gave 82% of L-Glutamic acid 5-{2-[4-(hydroxymethyl)phenyl] hydrazide} ( 1 ), i. e. agaritine, a metabolite of Agaricus bisporus. Without poisoning of the catalyst, hydrogenolysis of ( 11 ) yielded L-glutamic acid 5-[2-(4-tolyl)hydrazide] ( 12 ). 相似文献
23.
P. C. Deka H. Sarma Subir Sarkar T. D. Goswami B. K. Sarma 《Indian Journal of Physics》2009,83(7):1025-1030
With the growing understanding of the role of radon and its daughter products as major sources of radiation exposure, the
importance of large number of estimation of radon concentration in various parts of the country is realized. Inhalation of
radon, thoron and their decay products is the major source of the total radioactive dose received by the human population
from natural radiation. The indoor radon and thoron progeny levels in Nalbari area of Assam are studied by using the LR-115
(type II) Solid State Nuclear Track Detector in Plastic Twin Chamber dosimeter. Radon and thoron progeny levels in different
types of dwellings for one full calendar year are presented in this paper. For Assam Type (A.T.) houses, indoor radon progeny
concentrations vary from 0.17 to 0.64 mWL with an annual geometric mean of 0.27 mWL and that for Reinforced Cement Concrete
(R.C.C.) houses vary from 0.22 mWL to 0.60 mWL with the annual geometric mean of 0.37 mWL. The thoron progeny levels in A.T.
houses also vary from 0.01 to of 0.05 mWL with an annual geometric mean of 0.02 mWL and that for R.C.C. houses vary from 0.02
to 0.08 mWL with the annual geometric mean of 0.04 mWL.
相似文献
24.
25.
26.
Debanjan Bhattacharjee Parameswara Rao Alapati 《Molecular Crystals and Liquid Crystals》2017,648(1):66-76
This article represents the electrical studies of an interdigitated highly skewed N(4-n-pentyloxybenzylidene) 4-n-alkylaniline (5O.16) compound. Interestingly the compound is partially bent like and unsymmetrical in alkyl chain length. Dielectric and impedance spectroscopy studies indicate the coupling between the liquid crystal and the electrical field. Studies were carried out as a function of temperature as well as frequency. Semicircular nature of the Cole–Cole plots indicates the reorientation of the molecule with the applied field. Using the experimental data and the theoretically fitted results the effective equivalent model circuit was designed. Which used to explain the behavior of the compound under the external electric effect and the influence of the electrodes with different variable represent the resistor circuit. However, the effect of the conductivity of temperature and frequency are also reported. 相似文献
27.
We consider the Sel’kov model of glycolytic oscillator for a quantitative study of the limit cycle oscillations in the system.
We identify a region of parameter space where perturbation theory holds and use both Linstedt Poincaré technique and harmonic
balance to obtain the shape and frequency of the limit cycle. The agreement with the numerically obtained result is excellent.
We also find a different extreme, where the limit cycle is of the relaxation oscillator variety, has a large time period and
it is seen that, as a particular parameter in the model is varied, the time period increases indefinitely. We characterize
this divergence numerically. A calculational method is devised to capture the divergence approximately. 相似文献
28.
Abazov VM Abbott B Abdesselam A Abolins M Abramov V Acharya BS Adams DL Adams M Ahmed SN Alexeev GD Alves GA Amos N Anderson EW Baarmand MM Babintsev VV Babukhadia L Bacon TC Baden A Baldin B Balm PW Banerjee S Barberis E Baringer P Barreto J Bartlett JF Bassler U Bauer D Bean A Begel M Belyaev A Beri SB Bernardi G Bertram I Besson A Beuselinck R Bezzubov VA Bhat PC Bhatnagar V Bhattacharjee M Blazey G Blessing S Boehnlein A Bojko NI Borcherding F Bos K Brandt A Breedon R Briskin G Brock R 《Physical review letters》2001,87(6):061802
We present results of searches for technirho (rho(T)), techniomega (omega(T)), and Z' particles, using the decay channels rho(T),omega(T),Z'-->e(+)e(-). The search is based on 124.8 pb(-1) of data collected by the D0 detector at the Fermilab Tevatron during 1992-1996. In the absence of a signal, we set 95% C.L. upper limits on the cross sections for the processes pp-->rho(T),omega(T),Z'-->e(+)e(-) as a function of the mass of the decaying particle. For certain model parameters, we exclude the existence of degenerate rho(T) and omega(T) states with masses below about 200 GeV. We exclude a Z' with mass below 670 GeV, assuming that it has the same couplings to fermions as the Z boson. 相似文献
29.
A. Bhattacharyay J.K. Bhattacharjee 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(1):137-141
Reaction diffusion systems can exhibite both spatial and temporal patterns. We show that the effect of spatial variation of
the removal rate can have significant effect on the stability boundaries. In particular there can be a case of parametric
resonance.
Received 11 March 1998 相似文献
30.
Effects of Hall current on a steady hydromagnetic (MHD) fully developed flow in a rotating environment within a parallel plate
channel in the presence of an inclined magnetic field is studied. From an extension of literature [13] subject to a forced
oscillation it is observed that the present paper is methodically more correct to work first in the steady state where forced
oscillation becomes insignificant and then new results are expected for an unsteady MHD flow under the influence of a pulse-oscillator.
Exact solutions of the governing equations are obtained in a closed form. The graphical representation for the velocity and
the induced magnetic field are depicted graphically and the heat transfer at both the plates are presented in tables. 相似文献