全文获取类型
收费全文 | 132篇 |
免费 | 3篇 |
国内免费 | 8篇 |
专业分类
化学 | 48篇 |
晶体学 | 1篇 |
力学 | 19篇 |
综合类 | 2篇 |
数学 | 47篇 |
物理学 | 26篇 |
出版年
2023年 | 4篇 |
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2016年 | 7篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 5篇 |
2012年 | 4篇 |
2011年 | 7篇 |
2010年 | 5篇 |
2009年 | 12篇 |
2008年 | 4篇 |
2007年 | 6篇 |
2006年 | 7篇 |
2005年 | 6篇 |
2004年 | 3篇 |
2003年 | 7篇 |
2002年 | 2篇 |
2001年 | 5篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1978年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有143条查询结果,搜索用时 15 毫秒
1.
We establish the construction theory of function based upon a local field K p as underlying space. By virture of the concept of pseudo-differential operator, we introduce "fractal calculus"(or, p-type calculus, or, Gibbs-Butzer calculus). Then, show the Jackson direct approximation theorems, Bermstein inverse approximation theorems and the equivalent approximation theorems for compact group D( Kp) and locally compact group K+p(= Kp), so that the foundation of construction theory of function on local fields is established. Moreover, the Jackson type, Bernstein type,and equivalent approximation theorems on the H ?lder-type space Cσ(Kp), σ 0, are proved; then the equivalent approximation theorem on Sobolev-type space Wrσ(Kp),σ≥ 0, 1 ≤ r +∞, is shown. 相似文献
2.
Terence Tao 《偏微分方程通讯》2013,38(7-8):1471-1485
The endpoint Strichartz estimates for the Schrödinger equation is known to be false in two dimensions[7]. However, if one averages the solution in L2 in the angular variable, we show that the homogeneous endpoint and the retarded halfendoint estimates hold, but the full retarded endpoint fails. In particular, the original verisions of these estimates hold for radial data 相似文献
3.
《Analytical letters》2012,45(12):1239-1248
Abstract Reference electrodes limiting interfering effects of conventional reference electrodes on the measurement involving ion-selective electrodes have been developed. They are constructed of a plastic body with porous plug or sleeve junction. Solid state, low impedance, ion-selective electrodes (cupric, cadmium, fluoride) in the equilibrium of corresponding ion solution are used as the half-cells. The absence of interfering ions in the electrolyte allows the determination of the ion of interest at extremely low levels without interference. The electrodes have good reproducibility and stable intercomparison potentials of ± 0.2 mV. The performance of the electrodes has been tested for the measurement of sub-ppm halide levels. Data on stability, reproducibility, effects of temperature, ionic strengthand pH is presented and compared to that of conventional reference electrodes. 相似文献
4.
According to the transmission characteristics of high-speed long-haul optical transmission system, the main construction method of Low-Density Parity-Check (LDPC) code for optical transmission system is presented and a novel construction algorithm of LDPC code is proposed, the theoretical analysis shows that the parity check matrix of the LDPC code constructed by the proposed construction algorithm has no four-girth phenomenon, this is also theoretically proved out. Both the novel LDPC(3969,3720) code with 6.69% redundancy and the novel LDPC(8281,7920) code with 4.56% redundancy for optical transmission systems are constructed by using the presented construction method and proposed construction algorithm. The simulation results show that the net coding gain (NCG) of the two novel LDPC codes at the eighteenth iteration for the BER of 10?12 are respectively 1.63 dB and 1.49 dB more than that of the RS(255,239) code in ITU-T G.975. Moreover, the decoding of the LDPC code in the hardware can parallel be implemented, so the decoding speed of the two novel LDPC codes are very rapid, the complexities of implementing the two novel LDPC codes, compared with the concatenated codes in ITU-T G.975.1, are relatively lower, furthermore, the hardware overhead and storage space can relatively be saved and the computation complexity can be reduced in implementing the hardware in the future. As a result, the two novel LDPC codes can better be suitable for high-speed long-haul optical transmission systems. 相似文献
5.
6.
We present calculations of the desorption rate of water molecules from MgO(0 0 1) at a range of coverages θ and temperatures T. Our aim is to demonstrate that this can be done without making uncontrollable statistical mechanical approximations, and we achieve this by using the potential of mean force method reported previously. As in our earlier work on desorption of isolated molecules, we use a classical interaction model. We find that correlations between adsorbed molecules greatly increase the simulation time needed to obtain good statistical accuracy, compared with the isolated molecule. The activation energy for desorption varies significantly with coverage. The calculations also yield the chemical potential of adsorbed molecules as a function of θ and T, from which we can deduce the critical temperature and coverage for phase separation of adsorbed molecules. 相似文献
7.
8.
9.
Marcos D. Fernández Samuel Quintana Noelia Chavarría José A. Ballesteros 《Applied Acoustics》2009,70(5):753-760
Noise is one of the most highly found physical contaminants in the construction sector. The most negative effects caused by noise exposure are related to the hearing system and may produce professional deafness or even permanent deafness. As these effects have a very important influence on people’s health and well-being, it is necessary to assess the noise exposure and to develop mechanisms for studying and proposing preventive solutions.This work has studied the noise levels which the workers of the construction sector are exposed to. A number of representative measurements have been carried out using a sound level meter and a dosimeter to collect data from workers devoted to different tasks in the construction process. Analysis of the most important levels and indexes have been done with those data, and afterwards, they have been compared with the limits imposed by the different current regulations. 相似文献
10.