全文获取类型
收费全文 | 9344篇 |
免费 | 943篇 |
国内免费 | 600篇 |
专业分类
化学 | 321篇 |
晶体学 | 38篇 |
力学 | 2650篇 |
综合类 | 94篇 |
数学 | 6098篇 |
物理学 | 1686篇 |
出版年
2024年 | 12篇 |
2023年 | 102篇 |
2022年 | 84篇 |
2021年 | 115篇 |
2020年 | 242篇 |
2019年 | 225篇 |
2018年 | 231篇 |
2017年 | 243篇 |
2016年 | 299篇 |
2015年 | 253篇 |
2014年 | 395篇 |
2013年 | 828篇 |
2012年 | 398篇 |
2011年 | 518篇 |
2010年 | 422篇 |
2009年 | 548篇 |
2008年 | 577篇 |
2007年 | 577篇 |
2006年 | 524篇 |
2005年 | 473篇 |
2004年 | 438篇 |
2003年 | 416篇 |
2002年 | 370篇 |
2001年 | 310篇 |
2000年 | 327篇 |
1999年 | 262篇 |
1998年 | 271篇 |
1997年 | 225篇 |
1996年 | 178篇 |
1995年 | 124篇 |
1994年 | 118篇 |
1993年 | 102篇 |
1992年 | 111篇 |
1991年 | 94篇 |
1990年 | 79篇 |
1989年 | 45篇 |
1988年 | 31篇 |
1987年 | 25篇 |
1986年 | 29篇 |
1985年 | 38篇 |
1984年 | 52篇 |
1983年 | 32篇 |
1982年 | 39篇 |
1981年 | 28篇 |
1980年 | 19篇 |
1979年 | 17篇 |
1978年 | 11篇 |
1976年 | 5篇 |
1973年 | 8篇 |
1957年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
991.
Xiao-Bo Gong Yu-Qing Li Quan-Chao Gao Bin-Bin Cheng Bao-Rong Shen Zhi-Qiang Yan Zong-Lai Jiang 《Acta Mechanica Sinica》2011,27(6):1071-1080
The adhesion of endothelial progenitor cells(EPCs) on endothelial cells(ECs) is one of the critical physiological processes for the regenesis of vascular vessels and the prevention of serious cardiovascular diseases.Here,the rolling and adhesion behavior of EPCs on ECs was studied numerically.A two-dimensional numerical model was developed based on the immersed boundary method for simulating the rolling and adhesion of cells in a channel flow.The binding force arising from the catch bond of a receptor and ligand pair was modeled with stochastic Monte Carlo method and Hookean spring model.The effect of tumor necrosis factor alpha(TNF-α) on the expression of the number of adhesion molecules in ECs was analyzed experimentally.A flow chamber system with CCD camera was set up to observe the top view of the rolling of EPCs on the substrate cultivated with ECs.Numerical results prove that the adhesion of EPC on ECs is closely related to membrane stiff-ness of the cell and shear rate of the flow.It also suggests that the adhesion force between EPC and EC by P-selectin glycoprotein ligand-1 only is not strong enough to bond the cell onto vessel walls unless contributions of other catch bond are considered.Experimental results demonstrate that TNF-α enhanced the expressions of VCAM,ICAM,P-selectin and E-selectin in ECs,which supports the numerical results that the rolling velocity of EPC on TNF-α treated EC substrate decreases obviously compared with its velocity on the untreated one.It is found that because the adhesion is affected by both the rolling velocity and the deformability of the cell,an optimal stiffness of EPC may exist at a given shear rate of flow for achieving maximum adhesion rates. 相似文献
992.
993.
基本解方法与边界节点法求解Helmholtz方程的比较研究 总被引:4,自引:4,他引:0
基本解方法和边界节点法是基于径向基函数的两种重要无网格边界离散数值技术。针对Helmholtz方程,本文比较研究这两种数值方法在不同计算区域问题上的计算精度、插值矩阵对称性、病态性及计算成本。数值试验结果表明,两种方法都可以有效求解边界数据准确的Helmholtz问题。在数值离散过程中,两种方法都可以通过调整配置点的位... 相似文献
994.
995.
Scale up of gas-solid circulating fluidized bed (CFB) risers poses many challenges to researchers.In this paper,CFD investigation of hydrodynamic scaling laws for gas-solid riser flow was attempted on the basis of two-fluid model simulations,in particular,the recently developed empirical scaling law of Qi,Zhu,and Huang (2008).A 3D computational model with periodic boundaries was used to perform numerical experiments and to study the effect of various system and operating parameters in hydrodynamic scaling o... 相似文献
996.
The unsteady processes of the Marangoni migration of deformable liquid drops are simulated numerically in a wider range of Marangoni number (up to Ma = 500) in the present work. A steady terminal state can always be reached, and the scaled terminal velocity is a monotonic function decreasing with increasing Marangoni number, which is generally in agreement with corresponding experimental data. The topological structure of flow field in the steady terminal state does not change as the Marangoni number increases, while bifurcation of the topological structure of temperature field occurs twice at two corresponding critical Marangoni numbers. A third critical value of Marangoni number also exists, beyond which the coldest point jumps from the rear stagnation to inside the drop though the topological structure of the temperature field does not change. It is found that the inner and outer thermal boundary layers may exist along the interface both inside and outside the drop if Ma > 70. But the thickness decreases with increasing Marangoni number more slowly than the prediction of potential flow at large Marangoni and Reynolds numbers. 相似文献
997.
We study the diffusive logistic equation with a free boundary in higher space dimensions and heterogeneous environment. Such a model may be used to describe the spreading of a new or invasive species, with the free boundary representing the expanding front. For simplicity, we assume that the environment and the solution are radially symmetric. In the special case of one space dimension and homogeneous environment, this free boundary problem was investigated in Du and Lin (2010) [10]. We prove that the spreading-vanishing dichotomy established in Du and Lin (2010) [10] still holds in the more general and ecologically realistic setting considered here. Moreover, when spreading occurs, we obtain best possible upper and lower bounds for the spreading speed of the expanding front. When the environment is asymptotically homogeneous at infinity, these two bounds coincide. Our results indicate that the asymptotic spreading speed determined by this model does not depend on the spatial dimension. 相似文献
998.
999.
In this paper,we are concerned with the existence of positive solutions to an m-point boundary value problem with p-Laplacian of nonlinear fractional differential equation.By means of Krasnosel'skii fixed-point theorem on a convex cone and Leggett-Williams fixed-point theorem,the existence results of solutions are obtained. 相似文献
1000.
Lihua Chen Dept.of Math. Computer Science Fuqing Branch of Fujian Normal University Fuqing Fujian Jiaqi Mo Dept.of Math. Anhui Normal University Wuhu Anhui Faculty of Science Huzhou Teacher College Huzhou Zhejiang 《Annals of Differential Equations》2011,(4):434-439
An initial boundary value problem of semilinear nonlocal reaction diffusion equations is considered.Under some suitable conditions,using the asymptotic theory,the existence and asymptotic behavior of the interior layer solution to the initial boundary value problem are studied. 相似文献