全文获取类型
收费全文 | 11781篇 |
免费 | 1530篇 |
国内免费 | 1455篇 |
专业分类
化学 | 6042篇 |
晶体学 | 82篇 |
力学 | 393篇 |
综合类 | 85篇 |
数学 | 791篇 |
物理学 | 2518篇 |
综合类 | 4855篇 |
出版年
2024年 | 47篇 |
2023年 | 208篇 |
2022年 | 395篇 |
2021年 | 397篇 |
2020年 | 436篇 |
2019年 | 450篇 |
2018年 | 366篇 |
2017年 | 365篇 |
2016年 | 483篇 |
2015年 | 550篇 |
2014年 | 656篇 |
2013年 | 767篇 |
2012年 | 880篇 |
2011年 | 869篇 |
2010年 | 599篇 |
2009年 | 594篇 |
2008年 | 667篇 |
2007年 | 540篇 |
2006年 | 528篇 |
2005年 | 476篇 |
2004年 | 395篇 |
2003年 | 473篇 |
2002年 | 652篇 |
2001年 | 532篇 |
2000年 | 349篇 |
1999年 | 345篇 |
1998年 | 246篇 |
1997年 | 203篇 |
1996年 | 213篇 |
1995年 | 159篇 |
1994年 | 160篇 |
1993年 | 133篇 |
1992年 | 150篇 |
1991年 | 109篇 |
1990年 | 106篇 |
1989年 | 72篇 |
1988年 | 60篇 |
1987年 | 45篇 |
1986年 | 34篇 |
1985年 | 16篇 |
1984年 | 12篇 |
1983年 | 12篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1979年 | 1篇 |
1971年 | 1篇 |
1959年 | 2篇 |
1957年 | 2篇 |
1955年 | 1篇 |
1936年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
81.
The wavelet and harmonic filtering method suggested by Zalevsky and Ouzieli is introduced in this paper and adopted in our volume holographic image recognition system. This composite filter combines several scaled versions of the cascaded wavelet and harmonic filter, obtaining high discrimination ability and wide dynamic range of rotation and scale deformations. Optical experiments are conducted to demonstrate the validity and practicability of the algorithm. To the best of our knowledge, this is the first report of using this algorithm in a volume holographic system. Moreover, the separate correlation approach proposed in this paper greatly simplifies the manufacturing process and reduces the cost of the system. 相似文献
82.
IntroductionThemethoxyradical (CH3O)isanimportantinter mediateinthephotochemicaloxidationofhydrocarbonsintheatmosphere ,1 3andplaysasignificantroleintrans formingnitricoxidetonitrogendioxide .4 Similarly ,thereactionmechanismsofhydroxylandcarbonmonoxide5,6ando… 相似文献
83.
We apply the least‐squares finite element method with adaptive grid to nonlinear time‐dependent PDEs with shocks. The least‐squares finite element method is also used in applying the deformation method to generate the adaptive moving grids. The effectiveness of this method is demonstrated by solving a Burgers' equation with shocks. Computational results on uniform grids and adaptive grids are compared for the purpose of evaluation. The results show that the adaptive grids can capture the shock more sharply with significantly less computational time. For moving shock, the adaptive grid moves correctly with the shock. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2006 相似文献
84.
Xiao-jing Cai Quan-sen Jiu Chun-yan Xue 《应用数学学报(英文版)》2007,23(4):637-650
In this paper,the Dirichlet problem of Stokes approximate of non-homogeneous incompressibleNavier-Stokes equations is studied.It is shown that there exist global weak solutions as well as global andunique strong solution for this problem,under the assumption that initial density ρ_0(x)is bounded away from0 and other appropriate assumptions(see Theorem 1 and Theorem 2).The semi-Galerkin method is applied toconstruct the approximate solutions and a prior estimates are made to elaborate upon the compactness of theapproximate solutions. 相似文献
85.
简要评估了“926”植物生长调节剂的经济效益和生态环境。分析了开发应用的前景。 相似文献
86.
Semilinear Differential Inclusions in Separable Banach SpacesXueXingmei(薛星美)andSongGuozhu(宋国柱)(DepartmentofMathematics,Nanjin... 相似文献
87.
Differentkindsofopenchaincrownethershavebeensynthesizedasthemodelcompoundsofionophoresandtheirinteractionswithsodium,potassiumandrareearthionshavealsobeenstudiedl'z.PanshowedCe(III)yieldedalf1complexwithl,8-bis(8'-quinolyloxy)-3,6-dioxaandtheCe(IIl)ioncoordinatedbothtoetheroxygenandquinolinenitrogenatoms3.TUmInleridentifiedtwolanthanidenitratecomplexeshavingastoichiometryof3:2(3RE:2L)'.InordertostUdythefunctionsofbothquinolineandbenzenering,introducedintothepolyetherchain,a1inearpolyether… 相似文献
88.
89.
90.
The correlation times (τc) and cross relaxation rates of toluene, dimethylformamide, tetrahydrofuran, water-acetone and water-dioxane adsorbed on silica gel, alumina and charcoal were obtained by measurements of the integrated intensities of cross and diagonal peaks in their NOESY spectra. The (τc) of the above mentioned systems is in the range of 10?6?10?9 s, much longer than that in the liquid (10?12?10?14 s). It was found that intramolecular rotation of toluene adsorbed on charcoal is slower than that on SiO2, Al2O3 and the inversion of α and β protons in tetrahydrofuran is very fast (τc = 1.76×10?9 s). The cross relaxation plays an important role in the relaxation of molecules adsorbed on solid surfaces with low electron densities. 相似文献