全文获取类型
收费全文 | 2530篇 |
免费 | 80篇 |
国内免费 | 5篇 |
专业分类
化学 | 2073篇 |
晶体学 | 14篇 |
力学 | 22篇 |
数学 | 264篇 |
物理学 | 242篇 |
出版年
2024年 | 3篇 |
2023年 | 24篇 |
2022年 | 75篇 |
2021年 | 80篇 |
2020年 | 60篇 |
2019年 | 54篇 |
2018年 | 28篇 |
2017年 | 30篇 |
2016年 | 81篇 |
2015年 | 87篇 |
2014年 | 91篇 |
2013年 | 150篇 |
2012年 | 174篇 |
2011年 | 200篇 |
2010年 | 117篇 |
2009年 | 111篇 |
2008年 | 194篇 |
2007年 | 199篇 |
2006年 | 158篇 |
2005年 | 150篇 |
2004年 | 105篇 |
2003年 | 103篇 |
2002年 | 68篇 |
2001年 | 18篇 |
2000年 | 34篇 |
1999年 | 19篇 |
1998年 | 11篇 |
1997年 | 17篇 |
1996年 | 16篇 |
1995年 | 12篇 |
1994年 | 9篇 |
1993年 | 13篇 |
1992年 | 8篇 |
1991年 | 7篇 |
1990年 | 9篇 |
1988年 | 7篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 16篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1975年 | 2篇 |
1938年 | 1篇 |
1933年 | 1篇 |
1931年 | 1篇 |
排序方式: 共有2615条查询结果,搜索用时 31 毫秒
991.
Alice M Proverbio Valentina Brignone Silvia Matarazzo Marzia Del Zotto Alberto Zani 《BMC neuroscience》2006,7(1):44-10
Background
Current cognitive neuroscience models predict a right-hemispheric dominance for face processing in humans. However, neuroimaging and electromagnetic data in the literature provide conflicting evidence of a right-sided brain asymmetry for decoding the structural properties of faces. The purpose of this study was to investigate whether this inconsistency might be due to gender differences in hemispheric asymmetry. 相似文献992.
Giglio A Battistella S Talarico FF Brandmayr TZ Giulianini PG 《Micron (Oxford, England : 1993)》2008,39(5):552-558
Carabus lefebvrei Dejean 1826 is an helicophagous Italian endemic ground beetle that lives in central and south Apennines mountain forests, from lower altitudes to about 1500 m. In ground beetles, no morphofunctional data about immune system is available, even though they are well known both taxonomically and ecologically and they have been often used as indicators of the habitat quality due to their specificity to certain habitat types. In the current investigation the cellular population in the hemolymph of adult and third instar larvae of C. lefebvrei has been characterized by means of light and electron microscopy analysis and phagocytosis assays were performed in vivo by injection of 0.9 microm carboxylate-modified polystyrene latex beads in order to identify the hemocyte types involved in phagocytosis. Four morphotypes of circulating hemocytes were found both in larvae and in adults: prohemocytes, granulocytes, oenocytoids and plasmatocytes. After in vivo artificial non-self-challenge treatments, C. lefebvrei showed a non-specific immune response involving phagocytosis performed by plasmatocytes, both in adults and in larvae and by oenocitoids in larvae. In untreated animals, the hemocyte type presenting a firm phagocytic activity, the plasmatocytes, presented a percentage significantly higher in larvae than in adults, and after latex beads injections in larvae there was a tendency of significant difference in plasmatocyte percentage compared to controls injected with phosphate saline buffer. We think that these differences could be correlated with the peculiar morphology (less chitinization) and ecology of larval stages that are more sensitive to pathogens than adults. 相似文献
993.
Stefan Kowarik Alexander Gerlach Alexander Hinderhofer Silvia Milita Francesco Borgatti Federico Zontone Toshiyasu Suzuki Fabio Biscarini Frank Schreiber 《固体物理学:研究快报》2008,2(3):120-122
We report high structural order in thin films of the organic semiconductor perfluoro‐pentacene (PFP), which is a candidate material for n‐type applications, deposited by vacuum sublimation on oxidized silicon wafers. Bragg reflections up to high order in both specular and grazing incidence geometries and a mosaicity of less than 0.01° demonstrate the well defined structure. The thin film entirely consists of crystallites with a structure close to the bulk phase without any contamination with a second phase. Real‐time X‐ray measurements show that PFP grows in a Stranski–Krastanov growth mode with the first monolayer wetting the substrate before 3d‐growth sets in during growth of the second monolayer. Implications for its use are discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
994.
Silvia?CingolaniEmail author Angela?Pistoia 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2004,55(2):201-215
In this paper we shall consider the critical elliptic
equation
where
and a(x)
is a real continuous, non
negative function, not identically zero. By using a local Pohozaev
identity, we show that problem (0.1) does not admit a
family of solutions
which blows-up and concentrates as
at some zero point x0 of a(x)
if the order of flatness of the function a(x) at x0 is
相似文献
995.
Silvia Dassié Marco Vianello Renato Zanovello. 《Mathematics of Computation》2000,69(230):749-756
We show that an asymptotic summation method, recently proposed by the authors, can be conveniently applied to slowly convergent power series whose coefficients are rational functions of the summation index. Several numerical examples are presented.
996.
We give a new lower bound for the rectilinear crossing number of the complete geometric graph Kn. We prove that and we extend the proof of the result to pseudolinear drawings of Kn.
Dedicated to the memory of our good friend and mentor Víctor Neumann-Lara.
Received: April, 2003
Final version received: March 18, 2005 相似文献
997.
Spectral properties of normal (2k+1)-banded Toeplitz matrices of order n, with k≤⌊
n/2⌋, are described. Formulas for the distance of (2k+1)-banded Toeplitz matrices to the algebraic variety of similarly structured normal matrices are presented. 相似文献
998.
In this work, a qualitative analysis is carried out for reaction–advection–diffusion (RAD) systems modeling the interactions between two species with Allee effect. In particular, we study different scenarios: mutualism, competition, and a predator–prey relationship in order to investigate the survival or extinction of both populations. Global existence and uniqueness of positive solutions of the proposed RAD problems are demonstrated. Equilibrium states and asymptotic behavior of solutions are obtained using the monotone method and the upper and lower solutions technique. Numerical simulations by a Crank–Nicolson monotone iterative method of the different asymptotic solution dynamics are shown to illustrate our theoretical results. 相似文献
999.
We study minimum degree conditions for which a graph with given odd girth has a simple structure. For example, the classical work of Andrásfai, Erd?s, and Sós implies that every n‐vertex graph with odd girth and minimum degree bigger than must be bipartite. We consider graphs with a weaker condition on the minimum degree. Generalizing results of Häggkvist and of Häggkvist and Jin for the cases and 3, we show that every n‐vertex graph with odd girth and minimum degree bigger than is homomorphic to the cycle of length . This is best possible in the sense that there are graphs with minimum degree and odd girth that are not homomorphic to the cycle of length . Similar results were obtained by Brandt and Ribe‐Baumann. 相似文献
1000.
PACMAN (Passive and Active Compensability Multicriteria ANalysis) is a multiple criteria methodology based on a decision maker oriented notion of compensation, called compensability. A basic step of PACMAN is the construction of compensatory functions, which model intercriteria relations for each pair of criteria on the basis of compensability. In this paper we examine a simplified version of PACMAN, which uses the so-called linear compensatory functions and consistently reduces the overall complexity of its implementation in practical cases. We use Mathematica® to develop a computer-aided graphical interface that eases the interaction among the actors of the decision process at each stage of PACMAN. We also propose the possibility to perform a sensitivity analysis in this simplified version of PACMAN as a nonlinear optimization problem. 相似文献