全文获取类型
收费全文 | 37977篇 |
免费 | 4780篇 |
国内免费 | 3840篇 |
专业分类
化学 | 26121篇 |
晶体学 | 861篇 |
力学 | 1521篇 |
综合类 | 297篇 |
数学 | 2816篇 |
物理学 | 14981篇 |
出版年
2023年 | 303篇 |
2022年 | 710篇 |
2021年 | 802篇 |
2020年 | 1103篇 |
2019年 | 1046篇 |
2018年 | 1038篇 |
2017年 | 1203篇 |
2016年 | 1510篇 |
2015年 | 1349篇 |
2014年 | 1502篇 |
2013年 | 3655篇 |
2012年 | 1988篇 |
2011年 | 2221篇 |
2010年 | 1914篇 |
2009年 | 2257篇 |
2008年 | 2174篇 |
2007年 | 2095篇 |
2006年 | 2110篇 |
2005年 | 1802篇 |
2004年 | 1692篇 |
2003年 | 1591篇 |
2002年 | 1528篇 |
2001年 | 1089篇 |
2000年 | 1186篇 |
1999年 | 958篇 |
1998年 | 798篇 |
1997年 | 654篇 |
1996年 | 614篇 |
1995年 | 569篇 |
1994年 | 480篇 |
1993年 | 397篇 |
1992年 | 359篇 |
1991年 | 272篇 |
1990年 | 224篇 |
1989年 | 180篇 |
1988年 | 170篇 |
1987年 | 146篇 |
1986年 | 139篇 |
1985年 | 527篇 |
1984年 | 393篇 |
1983年 | 280篇 |
1982年 | 277篇 |
1981年 | 196篇 |
1980年 | 158篇 |
1979年 | 171篇 |
1977年 | 102篇 |
1976年 | 98篇 |
1975年 | 93篇 |
1974年 | 122篇 |
1973年 | 158篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
载能离子穿过固体界面引起界面原子迁移使界面原子混合和物质成分变化,从而导致界面发生材料相变。简要介绍了载能离子辐照引起金属/绝缘体界面混合效应及相变现象的主要实验研究进展、低能离子和高能离子辐照引起金属/绝缘体界面现象差异,并对离子辐照引起界面混合及相变的机制进行了初步探讨。When penetrating an interface between two kind of solids, energetic ions can induce atomic diffusion at both sides of the interface and then result in intermixing, atom re-distribution or composition change, as well as phase transformation. Main progress on the study of intermixing and phase change at metal/insulator interface induced by energetic ion irradiations, the difference of phenomena occurred at metal/insulator interfaces induced by high-and low-energy ions were briefly reviewed. Furthermore, the possible mechanisms related to intermixing and phase change at metal/insulator interface produced by energetic ion irradiations were also discussed in short words. 相似文献
102.
A new probabilistic cellular automaton model is introduced to simulate cluster and interface growth in two dimensions. The dynamics of this model is an extension to higher dimensions of the compact directed percolation studied by Essam. Numerical results indicate that the two-dimensional cluster coarsening and growth can be described only approximately by the conventional cluster size scaling due to a crossover in the growth mode. The spreading of the initially flat interface follows a purely diffusional,t
1/2, law. 相似文献
103.
本文介绍非线性方程转化直线性方程和多元线性回归法来分析近代物理实验中塞曼效应分裂干涉圆环多处选点测量的处理过程。 相似文献
104.
Jos A. Gmez-Pedrero Juan A. Quiroga M. Jos Terrn-Lpez Daniel Crespo 《Optics and Lasers in Engineering》2006,44(12):1297-1310
In this paper we present the application of a direct demodulation method for the measurement of surface topography by means of Shadow-Moiré. In our set-up, we use three LEDs (with green, red and blue peak wavelengths) to illuminate the grating. Due to the different position of these light sources, a polychromatic Shadow-Moiré fringe pattern is produced, which can be described as the superposition of three monochromatic (red, green and blue) fringe patterns. Taking the image of this polychromatic fringe pattern with a RGB CCD camera, we get a monochromatic fringe pattern stored at each RGB channel of the CCD. The direct demodulation algorithm employed uses these fringe patterns to calculate the wrapped phase map. After unwrapping the phase map using a standard multi-grid technique, we implemented an automatic procedure to detect the area of interest of the phase map by removing low modulation zones and to calculate the absolute value of the phase. In this way it is possible to determine the topography of a surface with a single RGB snapshot maintaining a simple experimental set-up, which is an important feature, especially for the study of dynamic phenomena such as deformations. We present the experimental results obtained after measuring different objects with both smooth and rough surface textures. 相似文献
105.
由于混凝土材料理化特性的差异,高强混凝土的弯压极限应变明显地小于普通混凝土,依据试验结果分析了高强混凝土的弯压极限应变变化规律,并给出了它的计算公式. 相似文献
106.
利用莫尔条纹的准正弦特性的三维轮廓术 总被引:5,自引:0,他引:5
分析了两个矩形光栅迭合产生的莫尔条纹的光强分布特性,通过选择适当的光栅参数,可得到一个近似的正弦分划板,并把它用于三维面形测量中,实验结果表明,这种方法简单,易于自动处理,有广泛的实用价值。 相似文献
107.
相型同步启动时间的M/M/c排队系统 总被引:4,自引:0,他引:4
本文研究带有同步启动时间的M/M/c系统,其中启动时间是相型变量,给出了稳态和等待时间分布等结果。 相似文献
108.
Hans -Peter Deutsch 《Journal of statistical physics》1992,67(5-6):1039-1082
A complete outline is given for how to determine the critical properties of polymer mixtures with extrapolation methods similar to the Ferrenberg-Swendsen techniques recently devised for spin systems. By measuring not only averages but the whole distribution of the quantities of interest, it is possible to extrapolate the data obtained in only a few simulations nearT
c
over the entire critical region, thereby saving at least 90% of the computer time normally needed to locate susceptibility peaks or cumulant intersections and still getting more precise results. A complete picture of the critical properties of polymer mixtures in the thermodynamic limit is then obtained with finite-size scaling functions. Since the amount of information extracted from a simulation in this way is drastically increased as compared to conventional methods, the investigation of mixtures with long chains or built-in asymmetries is now possible. As an example, the critical points, exponents, and amplitudes of dense, symmetric polymer mixtures with chain lengths ranging fromN=16 up toN=256 are determined within the framework of the 3D bond fluctuation model using grand canonical simulation techniques. As an example for an asymmetry, the generalization of the method to asymmetric monomer potentials is briefly discussed. 相似文献
109.
Yan Shun MA Qing Hua MENG Hong Yu SHI Yuan De LONG Tian Bao HUANG 《中国化学快报》2006,17(6):807-808
Dencichine (β-N-oxalyl-L-α, β-diaminopropionic acid, L-ODAP), a nonprotein amino acid, is a haemostatic agent present in important Chinese medicinal herbs such as Panax notoginseng, as well as other Panax species1. It was first isolated from the seeds … 相似文献
110.
S. S. Batsanov 《Russian Chemical Bulletin》1994,43(2):199-201
Experimental data are used to determine the atomic volumes and radii of the elements of subgroups IV–VIIA in the structures of metallic phases at high pressures. Metallic radii of nonmetals are compared with values based on Pauling and Goldschmidt calculations.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 220–222, February, 1994. 相似文献