全文获取类型
收费全文 | 5122篇 |
免费 | 285篇 |
国内免费 | 442篇 |
专业分类
化学 | 352篇 |
晶体学 | 2篇 |
力学 | 250篇 |
综合类 | 95篇 |
数学 | 4326篇 |
物理学 | 824篇 |
出版年
2024年 | 6篇 |
2023年 | 78篇 |
2022年 | 82篇 |
2021年 | 100篇 |
2020年 | 142篇 |
2019年 | 135篇 |
2018年 | 144篇 |
2017年 | 134篇 |
2016年 | 133篇 |
2015年 | 96篇 |
2014年 | 234篇 |
2013年 | 547篇 |
2012年 | 204篇 |
2011年 | 278篇 |
2010年 | 263篇 |
2009年 | 343篇 |
2008年 | 356篇 |
2007年 | 337篇 |
2006年 | 294篇 |
2005年 | 291篇 |
2004年 | 215篇 |
2003年 | 198篇 |
2002年 | 198篇 |
2001年 | 136篇 |
2000年 | 137篇 |
1999年 | 137篇 |
1998年 | 114篇 |
1997年 | 83篇 |
1996年 | 78篇 |
1995年 | 64篇 |
1994年 | 55篇 |
1993年 | 40篇 |
1992年 | 24篇 |
1991年 | 16篇 |
1990年 | 18篇 |
1989年 | 9篇 |
1988年 | 11篇 |
1987年 | 17篇 |
1986年 | 24篇 |
1985年 | 19篇 |
1984年 | 8篇 |
1983年 | 12篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 3篇 |
1978年 | 4篇 |
1973年 | 2篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1957年 | 3篇 |
排序方式: 共有5849条查询结果,搜索用时 31 毫秒
111.
The vapor pressures and osmotic coefficients of solutions of (R4N)2[MoS4] (R = ethyl, n-propyl and n-butyl) in acetone have been measured by head space-gas chromatography (HS-GC). Experimental data for the osmotic coefficients have been expressed by three thermodynamic models including the ionic interaction model of Pitzer, the electrolyte non-random two liquid (e-NRTL) model and the non-random factor (NRF) model. The ability of the models to fit the osmotic coefficient was compared on the basis of the standard deviation of the fittings. The results show that the considered models provide reliable results, but the Pitzer's model gives better results than the NRTL and the NRF methods, especially in the dilute region. 相似文献
112.
Vera V. Kovacevic-Vujcic 《Mathematical Programming》1991,52(1-3):467-479
This paper proposes a procedure for improving the rate of convergence of interior point methods for linear programming. If (x
k
) is the sequence generated by an interior point method, the procedure derives an auxiliary sequence (
). Under the suitable assumptions it is shown that the sequence (
) converges superlinearly faster to the solution than (x
k
). Application of the procedure to the projective and afflne scaling algorithms is discussed and some computational illustration is provided. 相似文献
113.
Summary The influence of the isothermal temperature, program rate, initial temperature and flow rate on retention indices was studied. The methods of Kováts, Van Den Dool and Local Lagrange Interpolation are compared. Ten experimental measurements were carried out on a capillary column coated with OV-101 stationary phase. 相似文献
114.
In this paper, the a posteriori error estimates of Chebyshev–Petrov–Galerkin approximations are investigated. For simplicity, we choose the Poisson equation with Dirichlet boundary conditions to discuss the a posteriori error estimators, and deduce their efficient and reliable properties. Some numerical experiments are performed to verify the theoretical analysis for the a posteriori error estimators. 相似文献
115.
M. Alcolea Palafox 《光谱学快报》2013,46(8):1395-1415
The infrared and laser Raman spectra (100-4000 cm1) of benzocaine hydrochloride were recorded and its vibrations analysed. A theoretical spectrum with the AM1 semiempirical method was calculated. An infrared study with the temperature was also made. From the experimental data, the torsion and inversion barriers of amine group were calculated. 相似文献
116.
117.
Defect turbulence described by the one-dimensional complex Ginzburg–Landau equation is investigated and analyzed via a birth–death process of the local structures composed of defects, holes, and modulated amplitude waves (MAWs). All the number statistics of each local structure, in its stationary state, are subjected to Poisson statistics. In addition, the probability density functions of interarrival times of defects, lifetimes of holes, and MAWs show the existence of long-memory and some characteristic time scales caused by zigzag motions of oscillating traveling holes. The corresponding stochastic process for these observations is fully described by a non-Markovian master equation. 相似文献
118.
Amol D. RautRavindranath Shashidhar Jayant R. Bandekar Balu P. Kapadnis 《Radiation Physics and Chemistry》2012,81(1):82-85
Campylobacter, a common poultry intestine commensal, is a well known cause of human gastric illnesses across the globe. Consumption of contaminated poultry meat is a major cause of Campylobacter related infections. In the present study, radiation sensitivity of indigenous strains of C. jejuni and C. coli isolated from poultry was evaluated. The decimal reduction dose (D10) values of different Campylobacter isolates at 0-4 °C in saline and blood broth were in the range of 0.120-0.210 kGy and 0.170-0.234 kGy, respectively. D10 values in chicken meat homogenate for Campylobacter were in the range of 0.110-0.190 kGy. Chicken meat samples were inoculated with C. jejuni and exposed to gamma radiation to study the effectiveness of radiation treatment in elimination of Campylobacter. Radiation treatment with a dose of 1 kGy could achieve complete elimination of 105 CFU of Campylobacter/g in poultry meat samples. No recovery of Campylobacter was observed, even after enrichment and selective plating in 1 kGy treated chicken meat samples stored at 4 °C up to 7 days. Present study shows that irradiation of poultry meat with 1 kGy can ensure safety of poultry meat. 相似文献
119.
《Discrete Mathematics》2023,346(6):113349
The problem of reconstructing the characteristic polynomial of a graph of order at least 3 from the collection of characteristic polynomials of its vertex-deleted subgraphs was posed by Cvetkovi? in 1973 as a spectral counter part to the well-known Ulam's reconstruction conjecture. Over the last 50 years, this problem has received notable attention, many positive results have been obtained, but in the general case the problem is still unresolved. In particular, no counter example is found in literature. In this expository paper we survey classical and some more recent results concerning the polynomial reconstruction problem, discuss some related problems, variations and generalizations. 相似文献
120.
We present a study of time-delay effects on a two-actor conflict model based on nonlinear differential equations. The state of each actor depends on its own state in isolation, its previous state, its inertia to change, the positive or negative feedback and a time delay in the state of the other actor. We use both theoretical and numerical approaches to characterize the evolution of the system for several values of time delays. We find that, under particular conditions, a time delay leads to the appearance of oscillations in the states of the actors. Besides, phase portraits for the trajectories are presented to illustrate the evolution of the system for different time delays. Finally, we discuss our results in the context of social conflict models. 相似文献