全文获取类型
收费全文 | 258篇 |
免费 | 116篇 |
国内免费 | 26篇 |
专业分类
化学 | 71篇 |
力学 | 5篇 |
数学 | 16篇 |
物理学 | 308篇 |
出版年
2023年 | 1篇 |
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 3篇 |
2012年 | 1篇 |
2011年 | 25篇 |
2010年 | 6篇 |
2009年 | 7篇 |
2007年 | 3篇 |
2006年 | 9篇 |
2005年 | 4篇 |
2004年 | 8篇 |
2003年 | 5篇 |
2002年 | 15篇 |
2001年 | 6篇 |
2000年 | 14篇 |
1999年 | 36篇 |
1998年 | 44篇 |
1997年 | 33篇 |
1996年 | 6篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 70篇 |
1992年 | 46篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 8篇 |
1988年 | 9篇 |
1987年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1968年 | 2篇 |
1967年 | 2篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1963年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有400条查询结果,搜索用时 15 毫秒
101.
PARALLEL AUXILIARY SPACE AMG FOR H(curl) PROBLEMS 总被引:2,自引:0,他引:2
In this paper we review a number of auxiliary space based preconditioners for the second order definite and semi-definite Maxwell problems discretized with the lowest order Nedelec finite elements. We discuss the parallel implementation of the most promising of these methods, the ones derived from the recent Hiptmair-Xu (HX) auxiliary space decomposition [Hiptmair and Xu, SIAM J. Numer. Anal., 45 (2007), pp. 2483-2509]. An extensive set of numerical experiments demonstrate the scalability of our implementation on large-scale H(curl) problems. 相似文献
102.
GUAN Ya-Feng ZHOU Liang-Mo LI Ling-EDalian Institute of chemical physics Chinese Academy of Sciences P.O.Box Dalian Liaoning China 《中国化学》1994,12(3):265-269
A live retention database for compound identification in isothermal and any step temperature programmed capillary gas chromatography has been developed. The database utilizes the Kovats retention indices of compounds on a given stationary phase and the retention time of n-alkanes measured at isothermal conditions on the column to be used, together with the programming parameters. Identification is performed by search operation that compares the calculated results with the retention values of unknown peaks. Cross-reference of the search results of different operating conditions is performed automatically by the database in order to increase the reliability of the identification. The error of the database conversion is ≤± 0.5 index unit, or ≤± 1% on retention time. This paper describes the principle and the structure of the database in detail. The experimental results for different calsses of compounds tested at divers operating conditions will be presented in Part Ⅱ. 相似文献
103.
低泵浦能量类氖锗等离子体软X射线激光实验 总被引:1,自引:1,他引:1
提出并采用具有一定时间间隔的双束脉冲加热锗薄膜靶方法,在泵浦激光能量100J,靶长10mm的实验条件下,观察到波长19.61nm和23.63nm两条类氖锗3s-3p激光跃迁线。19.61nm(J=0-1)的激光跃迁线发射强度较23.63nm(J=2-1)激光线的强度大,其发散角较后者小。 相似文献
104.
105.
Boling GUO Yongqian HAN Ganshan YANG Institute of Applied Physics Computational Mathematics Nonlinear Center for Studies P. O. Box Beijing China Graduate School of China Academy of Engineering Physics P. O. Box Beijing 《Communications in Nonlinear Science & Numerical Simulation》2000,5(1)
In 1986, Zhou and Guo in [1] proved the global existence of weak solution for generalized Landau-Lifshitz equations without Gilbert term in multi-dimensions. They consider thehomogeneous boundary problemwith the initial value conditionfor the system of ferromagnetic chain with several variableswhere j(x, t, Z) is a given 3-dimensional vector funC-non in x e R", t E R+, Z e R', W(x)is a given 3-dimensional initial value function on fi, fi is a bounded domain in n-dimensionalEuclidean space… 相似文献
106.
利用ICCD飞秒扫描成象和飞秒时间分辨光谱装置实验研究了高等植物捕光天线LHCⅡ三聚体和PSⅡ颗粒复合物的超快光谱动力学,经过吸收光谱和发射光谱分析,确定在LHCⅡ三聚体中至少存在7种Chl分子光谱特性,分别是Chlb653/656658.7、Chla662.0665.2、Chla/b670/671677.1、Chla675.0677.1、Chla680/681682.9、Chla685.0689.1和Chla695.0695.6.采用光强1013光子/cm2/脉冲激励浓度为30μg/mL的捕光天线LHCⅡ三聚体,在650nm到705nm谱段逐点探测分析处理,产生了2组短寿命组分210fs、520fs和5.2ps、36.7ps及2个长寿命组分1.8ns、2ns.最快的3个寿命210fs、520fs和5.2ps反映了三聚体Chlb分子向Chla分子的激发能传递过程;寿命36.7ps反映了Chla分子向相邻单体Chla分子的激发能传递过程;最长的2个寿命1.8ns和2ns是在三聚体中Chla分子通过中间体Chla分子辐射荧光,分别跃迁回基态的过程.获得的6个寿命组分有把激发能传递时间与Chla/b分子发射光谱相结合的特点.经拟合处理解析PSⅡ颗粒复合物光谱,得到3个组分谱,其峰值分别为686.8nm、692.2nm和694.9nm,与LHCⅡ比较分析,说明天然构型的PSⅡ有很强的吸收光能和有效传递光能的本领. 相似文献
107.
108.
109.
We present a computer model of diffusion limited aggregation with linear seed. The clusters with varying linear seed lengths are simulated, and their pattern structure, fractal dimension and multifractal spectrum are obtained. The simulation results show that the linear seed length has little effect on the pattern structure of the aggregation clusters if its length is comparatively shorter. With its increasing, the linear seed length has stronger effects on the pattern structure, while the dimension D f decreases. When the linear seed length is larger, the corresponding pattern structure is cross alike. The larger the linear seed length is, the more obvious the cross-like structure with more particles clustering at the two ends of the linear seed and along the vertical direction to the centre of the linear seed. Furthermore, the multifractal spectra curve becomes lower and the range of singularity narrower. The longer the length of a linear seed is, the less irregular and nonuniform the pattern becomes. 相似文献
110.
Ran RAN Guo Xing XIONG* Yu Hong ZHANG Shi Shan SHENG Wei Shen YANG State Key Laboratory of Catalysis Dalian Institute of Chemical Physics Chinese Academy of Sciences P.O.Box Dalian 《中国化学快报》2001,(3)
Partial oxidation of methane (POM) has several advantages over the traditional industrial method of steam reforming, such as much higher space velocity, reduced capital and operation cost and optimized the ratio of the products (H2/CO). Many investigators are interested in the POM reaction over monolith now1-3. Monolith is a kind of ceramic-like metal oxide material. It has relative high surface to volume ratio compared to commercial pellets, low pressure drop during the reaction process2,… 相似文献