全文获取类型
收费全文 | 6568篇 |
免费 | 1098篇 |
国内免费 | 666篇 |
专业分类
化学 | 2474篇 |
晶体学 | 78篇 |
力学 | 928篇 |
综合类 | 66篇 |
数学 | 757篇 |
物理学 | 4029篇 |
出版年
2024年 | 16篇 |
2023年 | 70篇 |
2022年 | 173篇 |
2021年 | 173篇 |
2020年 | 188篇 |
2019年 | 162篇 |
2018年 | 155篇 |
2017年 | 199篇 |
2016年 | 284篇 |
2015年 | 296篇 |
2014年 | 333篇 |
2013年 | 498篇 |
2012年 | 334篇 |
2011年 | 435篇 |
2010年 | 311篇 |
2009年 | 414篇 |
2008年 | 445篇 |
2007年 | 447篇 |
2006年 | 471篇 |
2005年 | 339篇 |
2004年 | 337篇 |
2003年 | 295篇 |
2002年 | 285篇 |
2001年 | 229篇 |
2000年 | 260篇 |
1999年 | 185篇 |
1998年 | 177篇 |
1997年 | 136篇 |
1996年 | 114篇 |
1995年 | 108篇 |
1994年 | 78篇 |
1993年 | 67篇 |
1992年 | 64篇 |
1991年 | 40篇 |
1990年 | 36篇 |
1989年 | 24篇 |
1988年 | 17篇 |
1987年 | 19篇 |
1986年 | 13篇 |
1985年 | 20篇 |
1984年 | 22篇 |
1983年 | 6篇 |
1982年 | 14篇 |
1981年 | 15篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1974年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有8332条查询结果,搜索用时 15 毫秒
121.
122.
在加工光楔列阵线聚焦系统时,人为地使各单元楔角与精确的理论值之间存在一定的偏差,以使单元衍射引起的大尺度不均匀性得到改善,文中进行了理论计算和实验验证,在既能改善均匀性,又能保证一定的焦线能量利用率的情况下,给出了合理的偏差数据,为优化均匀聚焦系统的工程设计提供了必要的依据。 相似文献
123.
124.
125.
126.
为了实现对基于自由摆的平板的控制,建立了基于自由摆的平板控制系统.首先分析平板的控制转角与自由摆转角的关系,推导出关系式,再对控制单元、反馈单元进行分析比较给出方案,采用32位LPC2138(ARM7)处理器为平板控制系统的中央控制单元,实现由高精度电位器测量出摆动角度后由步进电机控制的平板在周期摆动中做相应反馈调整,然后在现有器件的基础上编制出控制软件,在设备上进行调试,最后对系统的精度进行分析并进行实际测量.测量结果表明激光笔在摆动中照射在靶板上的光斑偏离基准线最大0.89cm,基本满足对平板的控制要求. 相似文献
127.
Ruifang Fang Aijun Zeng Linglin Zhu Longhai Liu Huijie Huang 《Optics Communications》2012,285(24):4884-4886
A simultaneous measurement method for the retardation and the fast axis angle of the eighth-wave plate in real time is proposed. The beam emitted from the laser passes through the circular polarizer and the eighth-wave plate to be measured successively, and then is split by the Dammann grating to form three sub-beams. They are analyzed by an analyzer array and detected by a detector array. Three detection signals are obtained simultaneously to calculate the retardation and the fast axis angle in real time. In experiments, a crystal quartz sample is measured at different fast axis angles. The average and standard deviation of its retardation respectively are 40.9°and 0.5°. The maximum measurement deviation of the fast axis angle is 2.1°. The usefulness of the method is verified. 相似文献
128.
Tsutomu Furuta Toshihiro IsobeMunetoshi Sakai Sachiko MatsushitaAkira Nakajima 《Applied Surface Science》2012,258(7):2378-2383
During evaporation, shape changes of nanoliter-scale (80-100 nL) water droplets were evaluated on two superhydrophobic surfaces with different random roughness (nm-coating, μm-coating). The square of the contact radius and the square of the droplet height decreased linearly with evaporation time. However, trend changes were observed at around 170 s (nm-coating) and around 150 s (μm-coating) suggesting a wetting mode transition. The calculated droplet radii for the wetting mode transition from the average roughness distance and the average roughness height of these surface structures were approximately equal to the experimental values at these trend changes. A certain level of correlation between the roughness size and droplet radius at the wetting mode transition was confirmed on surfaces with random roughness. 相似文献
129.
Superhydrophobic surfaces have shown inspiring applications in microfluidics, and self-cleaning coatings owing to water-repellent and low-friction properties. However, thermodynamic mechanism responsible for contact angle hysteresis (CAH) and free energy barrier (FEB) have not been understood completely yet. In this work, we propose an intuitional 3-dimension (3D) droplet model along with a reasonable thermodynamic approach to gain a thorough insight into the physical nature of CAH. Based on this model, the relationships between radius of three-phase contact line, change in surface free energy (CFE), average or local FEB and contact angle (CA) are established. Moreover, a thorough theoretical consideration is given to explain the experimental phenomena related to the superhydrophobic behavior. The present study can therefore provide some guidances for the practical fabrications of the superhydrophobic surfaces. 相似文献
130.
We study the propagation of anisotropic sound and shock waves in dipolar Bose-Einstein condensate in three dimensions (3D) as well as in quasi-two (2D, disk shape) and quasi-one (1D, cigar shape) dimensions using the mean-field approach. In 3D, the propagation of sound and shock waves are distinct in directions parallel and perpendicular to dipole axis with the appearance of instability above a critical value corresponding to attraction. Similar instability appears in 1D and not in 2D. The numerical anisotropic Mach angle agrees with theoretical prediction. The numerical sound velocity in all cases agrees with that calculated from Bogoliubov theory. A movie of the anisotropic wave propagation in a dipolar condensate is made available as supplementary material. 相似文献