全文获取类型
收费全文 | 1495篇 |
免费 | 249篇 |
国内免费 | 117篇 |
专业分类
化学 | 392篇 |
晶体学 | 10篇 |
力学 | 375篇 |
综合类 | 26篇 |
数学 | 275篇 |
物理学 | 783篇 |
出版年
2024年 | 7篇 |
2023年 | 23篇 |
2022年 | 41篇 |
2021年 | 42篇 |
2020年 | 47篇 |
2019年 | 78篇 |
2018年 | 33篇 |
2017年 | 62篇 |
2016年 | 72篇 |
2015年 | 68篇 |
2014年 | 82篇 |
2013年 | 100篇 |
2012年 | 116篇 |
2011年 | 106篇 |
2010年 | 68篇 |
2009年 | 80篇 |
2008年 | 75篇 |
2007年 | 77篇 |
2006年 | 63篇 |
2005年 | 51篇 |
2004年 | 54篇 |
2003年 | 48篇 |
2002年 | 59篇 |
2001年 | 49篇 |
2000年 | 44篇 |
1999年 | 27篇 |
1998年 | 24篇 |
1997年 | 25篇 |
1996年 | 19篇 |
1995年 | 30篇 |
1994年 | 20篇 |
1993年 | 17篇 |
1992年 | 16篇 |
1991年 | 23篇 |
1990年 | 12篇 |
1989年 | 28篇 |
1988年 | 21篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 11篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1957年 | 2篇 |
排序方式: 共有1861条查询结果,搜索用时 15 毫秒
111.
本文研究了磷钨钼钒四元杂多酸及其还原产物杂多蓝的形成条件、光度性质、组成和在测定高速钢中高钼的应用。试验表明,磷钨钼钒杂多蓝光度法测定钼具有新颖性、高选择性、较高准确性和简便性,适于高速钢中>1%Mo的测定。 相似文献
112.
A consecutive preparation method based upon accelerated solvent extraction (ASE) coupled with high‐speed counter‐current chromatography (HSCCC) was presented and aesculin was obtained from Cortex fraxinus. The extraction condition of ASE was optimized with response surface methodology; some significant parameters such as the solvent system and its stability, the amount of loading sample in HSCCC were also investigated. The original sample was first extracted with methanol at 105°C and 104 bar for 7 min using ASE, then the extracts were consecutively introduced into the HSCCC system and separated and purified with the same ethyl acetate/n‐butanol/water (7:3:10, v/v/v) solvent system for five times without further exchange and equilibrium. About 3.1 ± 0.2 mg/g in each time and total of 15.4 mg/g aesculin with purity over 95% was isolated from Cortex fraxinus. The results demonstrated that the consecutive preparation method was time and solvent saving and high throughput, it was suitable for isolation of aesculin from Cortex fraxinus, and also has good potential on the separation and purification of effective compounds from natural product. 相似文献
113.
114.
《Physics and Chemistry of Liquids》2012,50(2):85-91
Abstract Ultrasonic sound velocities and densities were measured for the binary mixtures of p-chlorotoluene with l-alcohols. The alcohols included: l-propanol, l-butanol, l-pentanol, l-hexanol and l-heptanol. Isentropic compressibilities, ks and deviation in isentropic compressibility, Ks from ideal behaviour have been calculated from the results. The deviation in isentropic compressibility has been ascribed to competition between structure-breaking and structural effects to different extents. 相似文献
115.
A simple fabrication method for tapered capillary tip and its applications in high‐speed CE and ESI‐MS 下载免费PDF全文
Yong‐Qiang Cheng Yuan Su Xiao‐Xia Fang Jian‐Zhang Pan Qun Fang 《Electrophoresis》2014,35(10):1484-1488
Fabrication of capillaries with tapered tips is an important technique that is required in many analytical chemistry areas, such as ESI‐MS, CE, electrochemical analysis, and microinjection. This paper describes a simple and effective grinding‐based fabrication method for capillaries with tapered tips. A novel grinding mode utilizing the combination of rotation and precession of an elastic capillary was developed, which significantly improved the controllability to the grinding process as well as the capillary tip shape. The capillary was fabricated by fixing it in an electric drill installed perpendicularly, and grind the capillary tip rotated around its own axis as well as the drill axis on sandpapers. Compared with conventional fabrication techniques for capillary tips, the present method is easy to control the capillary tip shape in routine laboratories without the requirement of expensive equipments or poisonous reagent (e.g. hydrofluoric acid (HF) solution). Various capillaries with different tip diameters and tip taper angles could be fabricated using the present method with good controllability and reproducibility. These capillaries were applied in high‐speed CE and ESI‐MS analysis to demonstrate the feasibility and potential of this fabrication method. 相似文献
116.
用修正的RELIEF方法测量高速空气流瞬时速度的理论研究 总被引:3,自引:1,他引:2
修正了拉曼激发激光感应电子荧光(RamanExciationpulseLaser-inducedElectronicFluorescence简称RELIEF)方法,以实现对亚音速和超音速空气流多点时速度的测量,测量精度优于2%。 相似文献
117.
M. I. Finston 《Optics & Laser Technology》1985,17(2):83-88
The elementary optics of rotating-mirror high-speed cameras are analysed geometrically. The images in an off-axis scanning mirror are shown to lie on Pascal's limacon. The Miller principle by which shuttering is accomplished is described. A simple estimate of motion blurring is compared with the Rayleigh criterion. 相似文献
118.
In this paperwewill derive a generalized uncertainty principle (GUP) in a simple varying speed of light (VSL) model. First
we will show that VSL is an immediate consequence of GUP. Then, within the framework of a simple VSL model, we will show that
GUP can be expressed as a function of cosmological scale factor. This expression gives two main results: uncertainties in
position and momentum are actually cosmological models dependent and these uncertainties depend on mass and momentum of the
particle under consideration. The relationship between matter content of the Universe and the values of uncertainties in early
stages of the evolution of the Universe will be discussed in a mini-superspace approach. 相似文献
119.
120.
闪光辐射照相及光学高速摄影图象的增强处理 总被引:3,自引:0,他引:3
本文介绍图象增强处理技术在闪光辐射照相图象及光学高速摄影图象中的应用.针对闪光图象及高速摄影图象的特点,研究了一些有效的图象增强方法,取得了很好的应用效果. 文中给出了部分应用实例. 相似文献