全文获取类型
收费全文 | 26021篇 |
免费 | 3979篇 |
国内免费 | 2359篇 |
专业分类
化学 | 17790篇 |
晶体学 | 545篇 |
力学 | 1082篇 |
综合类 | 280篇 |
数学 | 782篇 |
物理学 | 11880篇 |
出版年
2024年 | 38篇 |
2023年 | 210篇 |
2022年 | 562篇 |
2021年 | 634篇 |
2020年 | 837篇 |
2019年 | 759篇 |
2018年 | 727篇 |
2017年 | 975篇 |
2016年 | 1249篇 |
2015年 | 1152篇 |
2014年 | 1273篇 |
2013年 | 2583篇 |
2012年 | 1654篇 |
2011年 | 1587篇 |
2010年 | 1316篇 |
2009年 | 1439篇 |
2008年 | 1501篇 |
2007年 | 1510篇 |
2006年 | 1408篇 |
2005年 | 1241篇 |
2004年 | 1258篇 |
2003年 | 1066篇 |
2002年 | 1139篇 |
2001年 | 779篇 |
2000年 | 796篇 |
1999年 | 673篇 |
1998年 | 586篇 |
1997年 | 485篇 |
1996年 | 408篇 |
1995年 | 431篇 |
1994年 | 323篇 |
1993年 | 280篇 |
1992年 | 252篇 |
1991年 | 187篇 |
1990年 | 172篇 |
1989年 | 120篇 |
1988年 | 129篇 |
1987年 | 110篇 |
1986年 | 98篇 |
1985年 | 82篇 |
1984年 | 79篇 |
1983年 | 36篇 |
1982年 | 54篇 |
1981年 | 30篇 |
1980年 | 31篇 |
1979年 | 37篇 |
1978年 | 12篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1973年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
151.
152.
为借助激光全息进行无损检测,获得位相物体的信息,对位相物体激光全息二次曝光法无损检测进行了研究,指出一般的二次曝光法测位相物体典型光路的缺点,提出了物光波2次通过样品的改进方案。利用此方案对一些位相物体(如普通玻璃和有机玻璃)作了无损检测实验,得到了较满意的实验结果。与普通检测方法相比,该方法具有精度高、结果直接可靠、不损伤物体等诸多优点。对改进方案稍作改动,即可用于塑料制品和玻璃制品生产线对加工产品进行在线产品质量监控。 相似文献
153.
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
154.
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
155.
利用傅里叶光学理论,证明了一种新型波面传感器——旋转软刀口波面传感器的概念.在经典刀口法的刀口区,以渐变透过率代替突变透过率函数,在光瞳象面上可获得反映光瞳面位置待测波面位相梯度及位相梯度方向的调制信号.文中给出了实验结果和讨论. 相似文献
156.
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
157.
Wieczorek-Ciurowa K. Gamrat K. Paryło M. Shirokov Ju. G. 《Journal of Thermal Analysis and Calorimetry》2002,70(1):165-172
The physical mixtures of hydroxocarbonates of Cu and Ni with aluminium were activated using a laboratory planetary mill. The
chemical reactions and alloy formations as the effects of grinding were followed by the phase analysis of solid products based
on the thermogravimetry and X-ray diffractometry. Experimental evidence indicates that the nature of reactions and products
of mechanical activation was dependent on the amount of aluminium and time of grinding.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
158.
159.
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
160.
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