全文获取类型
收费全文 | 515篇 |
免费 | 13篇 |
国内免费 | 30篇 |
专业分类
化学 | 194篇 |
晶体学 | 1篇 |
力学 | 8篇 |
综合类 | 1篇 |
数学 | 153篇 |
物理学 | 201篇 |
出版年
2023年 | 18篇 |
2022年 | 4篇 |
2021年 | 4篇 |
2020年 | 7篇 |
2019年 | 5篇 |
2018年 | 6篇 |
2017年 | 8篇 |
2016年 | 7篇 |
2015年 | 5篇 |
2014年 | 22篇 |
2013年 | 27篇 |
2012年 | 20篇 |
2011年 | 30篇 |
2010年 | 21篇 |
2009年 | 41篇 |
2008年 | 27篇 |
2007年 | 53篇 |
2006年 | 32篇 |
2005年 | 23篇 |
2004年 | 16篇 |
2003年 | 18篇 |
2002年 | 15篇 |
2001年 | 21篇 |
2000年 | 14篇 |
1999年 | 9篇 |
1998年 | 26篇 |
1997年 | 13篇 |
1996年 | 13篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1980年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有558条查询结果,搜索用时 15 毫秒
71.
P. Jänker H. Leitz K.E.G. Löbner M. Moralles H.G. Thies 《The European Physical Journal A - Hadrons and Nuclei》1999,4(2):147-155
This paper contributes to the discussion on the phenomena of the enhanced emission of low–energetic charged particles during
compound nuclei decay. The decay of compound nuclei 52Fe, 56Ni, and 59Cu was studied. Energy spectra and emission angles of evaporated charged particles were measured in coincidence with gamma
rays to determine the corresponding evaporation residue nucleus. Additionally, evaporation residue distributions were determined
with the Munich rf recoil spectrometer. In this way, detailed channel–specific evaporation data were obtained for theoretical
analysis. We extracted evaporation barriers and compared them with corresponding fusion barriers. The main result was revealed
to be a lowering of the evaporation barrier for protons and alpha particles relative to the fusion barriers. But the observed
effect is not as intensive as reported in recent studies.
Received: 15 June 1998 / Revised version: 5 November 1998 相似文献
72.
K. Jessen W. Andrejtscheff M. Bergström P. von Brentano A. Dewald B. Herskind H. Meise C. Schumacher G. Sletten O. Stuch D. Weißhaar I. Wiedenhöver J. Wrzesinski 《The European Physical Journal A - Hadrons and Nuclei》1999,4(1):9-10
A new high-spin isomer in 145Sm was observed by in-beam γ-ray spectroscopy with the reaction 122Sn(27Al,3np) at 127 MeV performed at the Nordball multi-detector array in Roskilde. The excitation energy of the isomer was determined
to be E
x= 11147 keV, and using the generalized centroid-shift method its half-life was found to be T
1/2= (7.4 ± 1.0) ns.
Received: 23 October 1998 相似文献
73.
This paper presents a further study of the Manning and Darcy-Weisbach resistance coefficients, as they play a significant role in assessing the cross-sectional mean velocity, conveyance capacity and determining the lateral distribution of depth mean velocity and local boundary shear stress in compound channels. The relationships between the local, zonal and overall resistance coefficients, and a wide range of geometries and different roughness between the main channel and the flood plain are established by analyzing a vast amount of experimental data from a British Science and Engineering Research Council Flood Channel Facility (SERC-FCF). And the experimental results also show that the overall Darcy-Weisbach resistance coefficient for a compound channel is the function of Reynolds number, but the function relationship is different from that for a single channel. By comparing and analyzing the conventional methods with the experimental data to predict composite roughness in compound channels, it is found that these methods are not suitable for compound channels. Moreover, the reason why the conventional methods can not assess correctly the conveyance capacity of compound channels is also analyzed in this paper.The project supported by the National Natural Science Foundation of China (50279024), the National Key Basic Research and Development Program of China (973 Program) (2003CB415202) and the Specialized Research Fund for the Doctoral Program of Higher Education (20030610039)The English text was polished by Ron Marshall 相似文献
74.
非线性偏最小二乘导数分光光度法同时测定复方新诺明中二组分的含量 总被引:3,自引:0,他引:3
构造了导数光谱与多组分浓度间的非线性模型 ,以偏最小二乘法估计模型参数 ,建立了同时测定两组分的非线性偏最小二乘导数分光光度法 ,方法用于复方新诺明中磺胺甲唑SMZ(Sulfamethoxazole)和甲氧苄啶TMP(Trimethoprim)含量的测定 ,10份模拟样中SMZ ,TMP的回收率分别为 99 8%和 10 0 1% ,RSD分别为 1 3%和 1 6 %。结果明显好于线性偏最小二乘导数分光光度法。用该法测定复方新诺明片中的二组分含量测定结果与药典方法一致 ,该法为复方制剂的分光光度分析提供了更为理想的新途径。 相似文献
75.
76.
77.
78.
We examine the limiting average availability of a maintained system that deteriorates due to random shock process and as a response to its usage (wear out). System’s failures are not self-announcing, hence, failures must be detected via inspection. We consider randomly occurring shocks that arrive according to a Poisson process and cumulatively damage the system. Two models are considered: in Model 1 the shock and wear out processes are independent of the external environment and in Model 2, the shocks arrival rate, the shock magnitudes and the wear out rate are governed by a random environment which evolves as a Markov process. We obtain the system’s availability for both models. 相似文献
79.
We study the quantization problem for certain types of jump processes. The probabilities for the number of jumps are assumed to be bounded by Poisson weights. Otherwise, jump positions and increments can be rather generally distributed and correlated. We show in particular that in many cases entropy coding error and quantization error have distinct rates. Finally, we investigate the quantization problem for the special case of Rd-valued compound Poisson processes. 相似文献
80.
By linking queueing concepts with risk theory, we give a simple and insightful proof of the tax identity in the Cramér-Lundberg model that was recently derived in Albrecher & Hipp [Albrecher, H., Hipp, C., 2007. Lundberg’s risk process with tax. Blätter der DGVFM 28 (1), 13-28], and extend the identity to arbitrary surplus-dependent tax rates. 相似文献