全文获取类型
收费全文 | 2735篇 |
免费 | 450篇 |
国内免费 | 258篇 |
专业分类
化学 | 515篇 |
晶体学 | 13篇 |
力学 | 473篇 |
综合类 | 31篇 |
数学 | 603篇 |
物理学 | 1808篇 |
出版年
2024年 | 7篇 |
2023年 | 22篇 |
2022年 | 36篇 |
2021年 | 55篇 |
2020年 | 64篇 |
2019年 | 54篇 |
2018年 | 60篇 |
2017年 | 73篇 |
2016年 | 68篇 |
2015年 | 85篇 |
2014年 | 78篇 |
2013年 | 196篇 |
2012年 | 97篇 |
2011年 | 165篇 |
2010年 | 121篇 |
2009年 | 165篇 |
2008年 | 182篇 |
2007年 | 190篇 |
2006年 | 200篇 |
2005年 | 167篇 |
2004年 | 148篇 |
2003年 | 131篇 |
2002年 | 175篇 |
2001年 | 122篇 |
2000年 | 131篇 |
1999年 | 96篇 |
1998年 | 115篇 |
1997年 | 80篇 |
1996年 | 54篇 |
1995年 | 54篇 |
1994年 | 46篇 |
1993年 | 38篇 |
1992年 | 36篇 |
1991年 | 25篇 |
1990年 | 18篇 |
1989年 | 8篇 |
1988年 | 10篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 9篇 |
1984年 | 14篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1974年 | 2篇 |
1936年 | 1篇 |
排序方式: 共有3443条查询结果,搜索用时 15 毫秒
991.
G. Li S. Wu P. Zhou 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(2):267-277
The dressed-state populations and the resonance fluorescence spectrum of a V-type three-level atom driven by a strong coherent
field and a weak stochastic one simultaneously are investigated. There can be significant population inversion due to the
effect of the stochastic field. The atomic resonance fluorescence spectrum can be controlled by adjusting the frequency difference
between the coherent field and the stochastic one and the coherent Rabi frequency. Peak suppression and line narrowing occur
under appropriate conditions.
Received 23 June 2000 and Received in final form 18 January 2001 相似文献
992.
Grzegorz Piszczek Badri P. Maliwal Ignacy Gryczynski Jonathan Dattelbaum Joseph R. Lakowicz 《Journal of fluorescence》2001,11(2):101-107
We describe multiphoton excitation of the lanthanides europium (Eu3+) and terbium (Tb3+) when these ions are complexed with nucleic acids, proteins, and fluorescent chelators. In all cases excitation occurs by multiphoton absorption of the sensitizers. For the nucleotide GDP and an oligonucleotide with several guanines, the sensitized emission of Tb3+ excited at 776 nm indicated a three-photon process. For Tb3+ bound to the wild-type troponin C and a single tryptophan mutant (26W), excitation at 794 nm was also close to a three-photon process. For lanthanide chelators containing various sensitizers, we observed three-photon excitation in the case of methyl anthranilate, a mixuture of two- and three-photon excitation for carbostyril 124, and a two-photon process with a coumarin derivative. In the case of coumarin-sensitized emission of Eu3+ varied from a two- to a three-photon process at wavelengths ranging from 780 to 880 nm. The sensitized luminescence also shows significantly higher photostability compared to the fluorescence from the organic fluorophores alone. These results suggest the use of multiphoton-induced sensitized lanthanide fluorescence in biochemistry and cellular imaging.On leave from the Institute of Experimental Physics 相似文献
993.
Ch. Schlegel P. von Neumann-Cosel J. de Boer J. Gerl M. Kaspar I. Kozhoukharov M. Loewe H.J. Maier P.J. Napiorkowsky I. Peter M. Rejmund A. Richter H. Schaffner J. Srebrny M. Würkner H.J. Wollersheim 《The European Physical Journal A - Hadrons and Nuclei》2001,10(2):135-138
In-beam Coulomb excitation of the exotic odd-odd nucleus 180Ta has been studied by using a 136Xe beam and a setup consisting of five EUROBALL CLUSTER detectors and the Darmstadt-Heidelberg Crystal Ball array. Spectroscopic
information on the extremely rare 180Ta is obtained from the comparison between an enriched (3.6±0.3% 180Ta) and a natural tantalum target. Possible evidence for a depopulation from the long-lived high-spin J
π = 9- isomer to the short-lived J
π = 1+ ground state is searched for by different methods. The decay of low-K bandheads, which are nanosecond isomers, towards the ground-state band can be demonstrated in delayed spectroscopy. A γγ
coincidence analysis provides indications of K = 5 in-band transitions. Finally, when the Crystal Ball is used as an energy and γ multiplicity filter, signals of decay
into the K = 0 band are observed.
Received: 23 January 2001 / Accepted: 8 February 2001 相似文献
994.
SHAO Liang SHAO Dan SHAO Chang-Gui H. Noda CHEN Yi-Han 《理论物理通讯》2006,46(1):77-86
In 4-dimensional R-gravity, using the linear and square terms of the expanding expression of the space-time connection, we calculate the possible curvature excitation (order k^4) of gravitational field, which is given by the first term of quantum Wilson loop (w) through two-point Green's function of the connection. At the same time using the tree diagram propagators of gravitons, the lowest order (k^4) correction to (w) is also calculated through the graviton self-energy in the term. Under the accuracy condition up to order k^4, we have obtained a complete expression of the excitation contributed from the leading term (w^(2))of (w). 相似文献
995.
Photoluminescence of multiwalled carbon nanotubes excited at different wavelengths 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In this paper the multiwalled carbon nanotubes (MWNTs) were synthesized by a
chemical vapour deposition and the SEM graph shows that the sample has good
construction. The micro-Raman spectrum shows the characteristic line of the MWNTs
and an additional line produced by the defects on the outer surface of MWNTs. The
photoluminescence (PL) spectra observed experimentally are variable under different
excitation wavelengths and the strong excitation wavelength dependence of
luminescence indicates a distribution of emitters which include electron $\pi$ in
excited states and the Van Hove singularities. The absorption spectra confirm the
transition channels which are consistent with the PL emission. 相似文献
996.
通过把Lamb基本解中的调和函数转换为扁球坐标系下的表达式,这项研究成功地得到了一个新的Stokes流动三维基本解.此基本解可用于解决任意多个扁椭球处于任意位置和方向时的流动问题.应用最小二乘法,三维流动问题中常遇到的收敛性差的困难在此得以完全克服.结果表明该方法具有准确度高,收敛性好和计算量小的特点.由于扁球可用于模拟从圆盘到圆球的多种物体形状,此基本解被用于系统地分析了各种几何因素对两个扁球所受力和力矩的影响.为了显示此方法的通用性,该基本解还用于研究了两例三个扁球的问题. 相似文献
997.
Excitation energies and electromagnetic transition strengths in even-even ^96-108Mo nuclei have been described systematically be using the proton-neutron interacting boson model (IBM-2).It appears that the properties of low-lying levels in these isotopes,for which the comparison between experiment and theory is possible,can be satisfactorily described by the IBM-2 model,provided proper account is taken of the presence at low energy of states having a mixed-symmetry character.It seems possible to identify,in each isotope,a few states having such a character,the lowest ones being either 22^ or 23^ levels.It is found that these nuclei are in the transition from U(5) to SU(3). 相似文献
998.
基本解方法属于径向基函数类方法,它使用微分算子的基本解作为基于欧氏距离的径向基函数.借助测地距离,给出了求解各向异性材料中的热传导方程的基本解方法.该方法无需对时间进行离散或Laplace变换,也无需进行变量变换,而是直接在整个时间空间区域上进行求解.文中给出了数值例子,来验证基于测地距离的基本解方法在求解该各向异性问题时的稳定性和有效性. 相似文献
999.
ZHENG Chun-Long FEI Jin-Xi 《理论物理通讯》2007,48(4):657-661
Starting from an improved projective method and a linear variable separation approach, new families of variable separation solutions (including solltary wave solutlons, periodic wave solutions and rational function solutions) with arbitrary functions [or the (2+ 1)-dimensional general/zed Broer-Kaup (GBK) system are derived. Usually, in terms of solitary wave solutions and/or rational function solutions, one can find abundant important localized excitations. However, based on the derived periodic wave solution in this paper, we reveal some complex wave excitations in the (2+1)-dimensional GBK system, which describe solitons moving on a periodic wave background. Some interesting evolutional properties for these solitary waves propagating on the periodic wave bactground are also briefly discussed. 相似文献
1000.
常规净水工艺去除有机物效果的三维荧光光谱分析法 总被引:5,自引:0,他引:5
有机物的荧光特性被广泛用来解析其在水体中的来源与分布。荧光光谱技术具有灵敏度高、选择性好、且不破坏样品结构的优点,非常适合用来研究有机物的化学和物理性质。运用三维荧光光谱分析技术对常规净水工艺中有机物的去除效果进行了研究。实验结果表明,三维荧光光谱技术能有效地揭示净水工艺中有机物的变化过程。在整个净水过程中,没有完全消除类富里酸荧光物质,也没有产生新的荧光物质。就类富里酸荧光物质的去除效果而言,混凝沉淀基本没有去除作用,过滤作用的去除率在5%~15%之间。 相似文献