全文获取类型
收费全文 | 2383篇 |
免费 | 75篇 |
国内免费 | 5篇 |
专业分类
化学 | 1542篇 |
晶体学 | 23篇 |
力学 | 67篇 |
数学 | 309篇 |
物理学 | 522篇 |
出版年
2023年 | 39篇 |
2022年 | 39篇 |
2021年 | 78篇 |
2020年 | 66篇 |
2019年 | 66篇 |
2018年 | 56篇 |
2017年 | 36篇 |
2016年 | 74篇 |
2015年 | 71篇 |
2014年 | 62篇 |
2013年 | 135篇 |
2012年 | 127篇 |
2011年 | 190篇 |
2010年 | 99篇 |
2009年 | 102篇 |
2008年 | 143篇 |
2007年 | 123篇 |
2006年 | 107篇 |
2005年 | 103篇 |
2004年 | 98篇 |
2003年 | 47篇 |
2002年 | 48篇 |
2001年 | 40篇 |
2000年 | 43篇 |
1999年 | 26篇 |
1998年 | 14篇 |
1997年 | 26篇 |
1996年 | 28篇 |
1995年 | 15篇 |
1994年 | 19篇 |
1993年 | 25篇 |
1992年 | 11篇 |
1991年 | 16篇 |
1990年 | 19篇 |
1989年 | 11篇 |
1988年 | 13篇 |
1987年 | 15篇 |
1986年 | 12篇 |
1985年 | 15篇 |
1984年 | 16篇 |
1983年 | 14篇 |
1982年 | 11篇 |
1981年 | 18篇 |
1980年 | 12篇 |
1979年 | 16篇 |
1978年 | 14篇 |
1977年 | 10篇 |
1976年 | 13篇 |
1973年 | 12篇 |
1972年 | 7篇 |
排序方式: 共有2463条查询结果,搜索用时 15 毫秒
11.
We analyze the well-posedness of the initial value problem for the dissipative quasi-geostrophic equations in the subcritical
case. Mild solutions are obtained in several spaces with the right homogeneity to allow the existence of self-similar solutions.
While the only small self-similar solution in the strong
Lp{\cal L}^{p}
space is the null solution, infinitely many self-similar solutions do exist in weak-
Lp{\cal L}^{p}
spaces and in a recently introduced [7] space of tempered distributions. The asymptotic stability of solutions is obtained
in both spaces, and as a consequence, a criterion of self-similarity persistence at large times is obtained. 相似文献
12.
We exhibit a characteristic structure of the class of all regular graphs of degree d that stems from the spectra of their adjacency matrices. The structure has a fractal threadlike appearance. Points with coordinates given by the mean and variance of the exponentials of graph eigenvalues cluster around a line segment that we call a filar. Zooming-in reveals that this cluster splits into smaller segments (filars) labeled by the number of triangles in graphs. Further zooming-in shows that the smaller filars split into subfilars labeled by the number of quadrangles in graphs, etc. We call this fractal structure, discovered in a numerical experiment, a multifilar structure. We also provide a mathematical explanation of this phenomenon based on the Ihara-Selberg trace formula, and compute the coordinates and slopes of all filars in terms of Bessel functions of the first kind. 相似文献
13.
Audrey A S G Lonni Ieda S Scarminio Lucas M C Silva Dalva T Ferreira 《Analytical sciences》2003,19(7):1013-1017
Phytochemical investigation of the aerial parts of three Baccharis species (Asteraceae family) was performed using HPLC and chemometric methods, with the objective of distinguishing between three morphologically very similar species: Baccharis genistelloides Persoon var. trimera (Less.) DC, B. milleflora (Less.) DC and B. articulata (Lam.) Persoon. With the help of Principal Component Analysis (PCA) and variance weights, it was possible to characterize the chromatographic profiles of the alcoholic extracts of the three species. Application of Soft Independent Modeling of Class Analogy (SIMCA) and K-Nearest Neighbor (KNN) methods on a training set of 74 extracts resulted in models that correctly classified all eight samples in an independent test set. 相似文献
14.
The computation of long wave propagation through the ocean obviously depends on the initial condition. When the waves are generated by a moving bottom, a traditional approach consists in translating the ‘frozen’ sea bed deformation to the free surface and propagating it. The present study shows the differences between the classical approach (passive generation) and the active generation where the bottom motion is included. The analytical solutions presented here exhibit some of the drawbacks of passive generation. The linearized solutions seem to be sufficient to consider the generation of water waves by a moving bottom. To cite this article: D. Dutykh et al., C. R. Acad. Sci. Paris, Ser. I 343 (2006). 相似文献
15.
We use the PCP-SAFT equation of state, which is of the Van der Waals type and has a sound physical basis, to predict mixture properties, such as vapor–liquid and liquid–liquid equilibria, as well as excess enthalpies. We use molecular properties, such as dipole moment, quadrupole moment, polarizability and dispersion interaction coefficients, that have been determined quantum mechanically in Part I of this publication and adjust the remaining three pure compound parameters to pure compound data. We finally present a new combination rule for the dispersion energy parameter ? that is based on the quantum mechanically determined data. The predictions based on quantum mechanically determined pure compound properties along with the new combination rule show an improved performance compared to the original PCP-SAFT combination rule. 相似文献
16.
R. S. Dias A. P. Roque D. M. S. S. Vitti 《Journal of Radioanalytical and Nuclear Chemistry》2006,269(3):661-663
Summary The objective of this study was to determine endogenous phosphorus excretion in sheep fed with different diets. Sixteen male
growing sheep, received a basic diet with: 42% hydrolyzed sugarcane bagasse (HSB), 45% lucerne hay (LH) plus 14% hydrolyzed
sugarcane bagasse, and 30% citrus pulp (CTP) plus 40% hydrolyzed sugarcane bagasse. A dose of 7.7 MBq 32P was injected into the left jugular vein of each animal. The P endogenous fecal losses were: 1.69, 2.50, 2.33 and 1.45 g/animal
for treatments HSB, LH, and CTP respectively (P>0.05). The type of diet influenced slight endogenous P excretion but altered
excretion of P in urine. Endogenous P excreted in feces (PF) comes mainly from saliva and represents an important loss of P. The estimation of net requirements of phosphorus (P) for
ruminants includes endogenous losses, which is also essential for calculating true absorption of this mineral. Physical structure
of the feed may influence endogenous losses, altering the metabolism of P and also the demand of this mineral, therefore being
important to know how different feeds affect endogenous P losses. 相似文献
17.
18.
Lucas Hernández Pedro Hernández José Vicente 《Fresenius' Journal of Analytical Chemistry》1993,345(11):712-715
Summary The determination of methyl-parathion (MPT), ortho (ONP), meta (MNP) and para nitrophenol (PNP) has been studied by differential pulse voltammetry with a carbon-paste electrode modified with 50% (w/w) of C18. A study of the influence of the pH in the preconcentration cell and the measurement cell was carried out for an electrode with 50% modifier and an accumulation time of 5 min. The voltammograms were recorded with a sweep rate of 40 mV s–1 and a pulse amplitude of 50 mV. With the optimum conditions of pH for both of the steps, various other variables were studied. The variables for each compound were optimized and the possibility of application to the determination of a mixture of the four compounds was investigated. The determination limits found for all the compounds are: 2 ng ml–1 for ONP, 5 ng ml–1 for MNP, 4.3 ng ml–1 for PNP and 7.9 ng ml–1 for MPT. The method was applied to samples of a small lake which gathers rain water and water filtered from land on which cereals are grown. 相似文献
19.
Dupieux P Alard JP Augerat J Babinet R Bastid N Brochard F Charmensat P De Marco N Fanet H Fodor Z Fraysse L Girard J Gorodetzky P Gosset J Laspalles C Lemaire MC L'Hôte D Lucas B Marroncle J Montarou G Parizet MJ Poitou J Qassoud D Racca C Schimmerling W 《Physics letters. [Part B]》1988,200(1-2):17-21
Proton-proton small angle correlations have been measured in neon-nucleus collisions, using the 4 pi detector Diogene, at 400 and 800 MeV per nucleon incident energies. Values of the size of the emitting region are obtained by comparison with the Koonin formula, taking into account the biases of the apparatus. The dependence of the density on target mass and incident energy is also analysed. 相似文献
20.