全文获取类型
收费全文 | 870篇 |
免费 | 10篇 |
国内免费 | 1篇 |
专业分类
化学 | 491篇 |
晶体学 | 19篇 |
力学 | 24篇 |
数学 | 68篇 |
物理学 | 279篇 |
出版年
2022年 | 12篇 |
2021年 | 14篇 |
2020年 | 18篇 |
2019年 | 16篇 |
2018年 | 14篇 |
2017年 | 9篇 |
2016年 | 13篇 |
2015年 | 7篇 |
2014年 | 33篇 |
2013年 | 63篇 |
2012年 | 38篇 |
2011年 | 48篇 |
2010年 | 28篇 |
2009年 | 20篇 |
2008年 | 34篇 |
2007年 | 23篇 |
2006年 | 28篇 |
2005年 | 30篇 |
2004年 | 22篇 |
2003年 | 16篇 |
2002年 | 34篇 |
2001年 | 18篇 |
2000年 | 15篇 |
1999年 | 13篇 |
1998年 | 10篇 |
1997年 | 14篇 |
1996年 | 11篇 |
1995年 | 9篇 |
1994年 | 12篇 |
1993年 | 17篇 |
1992年 | 12篇 |
1991年 | 13篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1988年 | 13篇 |
1987年 | 12篇 |
1986年 | 11篇 |
1984年 | 12篇 |
1983年 | 8篇 |
1982年 | 17篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1979年 | 12篇 |
1978年 | 13篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1975年 | 12篇 |
1974年 | 7篇 |
1973年 | 12篇 |
1972年 | 5篇 |
排序方式: 共有881条查询结果,搜索用时 15 毫秒
31.
Gross dissolution of natural calcite crystal in concentrated nitric acid give interesting results. The gross dissolution is maximum at 6 M concentration of HNO3. The activation energy increases as the concentration of HNO3 increases. Similarly pre-exponential factor is also increases as concentration increases. The combined effect of activation energy and pre-exponentail factor gives the peak at 6 M concentration of nitric acid. 相似文献
32.
33.
We report a method for the measurement of nematic liquid crystal (NLC) cell parameters i.e., switching voltage, birefringence, retardation, dielectric anisotropy, average tilt angle and change in refractive index with applied DC voltage to LC material. The proposed method is based on optical interferometry and Fourier transform fringe analysis technique, in which we obtain 2-dimensional (2D) phase map of the interferograms as a function of applied voltage. Mach-Zehnder interferometer (MZI) was used for the study of cell parameters and interferograms were recorded at different applied DC voltages to NLC cell using CCD camera. From the phase map, 2D-refractive index distribution of the LC cell with applied voltage was reconstructed. Analytical equations are derived based on optical interferometry and then solved to obtain cell parameters. The present method is fast and can give 2D-cell parameters from only two quick interferograms. 相似文献
34.
Cumulant functions are introduced to describe the statistical state of a radiation field. These functions are simply related
to the optical coherence functions but have some interesting features. It is shown that if the cumulant functions of all orders
greater than some numberN
0 vanish then they also vanish for all orders greater than 2. Thermal field is the only field having this property. This property
holds whether the field is described by a classical stochastic process or by a quantum density operator. Further the particular
operator ordering used in defining these cumulant functions for the quantized field affects only the second order cumulant
function. To describe the statistical state of a vector field such as partially polarized or unpolarized radiation, one would
need to introduce cumulant tensors. 相似文献
35.
KM Varier AM Vinodkumar NVSV Prasad PV Madhusudhana Rao DL Sastry Lagy T Baby MC Radhakrishna NG Puttaswamy JJ Das P Sugathan N Madhavan AK Sinha DO Kataria 《Pramana》1999,53(3):529-533
Large enhancements have been observed in the sub-barrier fusion cross sections for Ti+Ni systems in our previous studies.
Coupled channel calculations incorporating couplings to 2+ and 3− states failed to explain these enhancements completely. A possibilty of transfer channels contributing to the residual enhancements
had been suggested. In order to investigate the role of relevant transfer channels, measurements of one- and two-nucleon transfer
were carried out for 46,48Ti+61Ni systems. The present paper gives the results of these studies. 相似文献
36.
V. K. Aswal J. V. Joshi P. S. Goyal Rajesh Patel R. V. Upadhyay R. V. Mehta 《Pramana》2004,63(2):285-290
Small-angle neutron scattering studies have been carried out to check the structural integrity of citryltrimethylammonium
bromide (CTABr) micelles in a magnetic fluid for different magnetic fluid concentrations at two different temperatures 303
and 333 K. It is found that the CTABr micelles grow with increasing magnetic fluid concentration and there is a decrease in
the micellar size with increase in temperature. 相似文献
37.
Nonequilibrium steady-state currents, unlike their equilibrium counterparts, continuously dissipate energy into their physical surroundings leading to entropy production and time-reversal symmetry breaking. This Letter discusses these issues in the context of quantum impurity models. We use simple thermodynamic arguments to define the rate of entropy production sigma and show that sigma has a simple information-theoretic interpretation in terms of nonequilibrium distribution functions. This allows us to show that the entropy production is strictly positive for any nonequilibrium steady state. We conclude by applying these ideas to the resonance level model and the Kondo model. 相似文献
38.
Prof. Henning Hopf Prof. Stephen A. Matlin Prof. Goverdhan Mehta Prof. Alain Krief 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(6):2170-2174
In chemistry and other sciences, hype has become commonplace, compounded by the hypocrisy of those who tolerate or encourage it while disapproving of the consequences. This reduces the credibility and trust upon which all science depends for support. Hype and hypocrisy are but first steps down a slippery slope towards falsification of results and dissemination of fake science. Systemic drivers in the contemporary structure of the science establishment encourage exaggeration and may lure the individual into further steps along the hype-hypocrisy-falsification-fakery continuum. Collective, concerted intervention is required to effectively discourage entry to this dangerous pathway and to restore and protect the probity and reputation of the science system. Chemists must play and active role in this effort. 相似文献
39.
Dr. Showkat Rashid Dr. Bilal A. Bhat Prof. Goverdhan Mehta 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(71):17005-17010
Previously unknown entities in the form of 1,2,3,4,5,6,7,8,9,10-decahydroxydecalins (DHDs) have been conceptualized and the first member of this class, an inosito-inositol, has been synthesized from aromatic hydrocarbon naphthalene following a flexible strategy that is amenable to diversity creation. The DHD accessed here has been subjected to preliminary in silico evaluation with Aβ and may hold some promise in Alzheimer's disease therapeutics. 相似文献
40.
The objective of this paper is to investigate the role of the set of irrational numbers as the codomain of order-preserving
functions defined on topological totally preordered sets. We will show that although the set of irrational numbers does not
satisfy the Debreu property it is still nonetheless true that any lower (respectively, upper) semicontinuous total preorder
representable by a real-valued strictly isotone function (semicontinuous or not) also admits a representation by means of
a lower (respectively, upper) semicontinuous strictly isotone function that takes values in the set of irrational numbers.
These results are obtained by means of a direct construction. Moreover, they can be related to Cantor’s characterization of the real line to obtain much more general results on the semicontinuous
Debreu properties of a wide family of subsets of the real line.
相似文献