首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   238篇
  免费   10篇
  国内免费   1篇
化学   147篇
力学   2篇
数学   10篇
物理学   90篇
  2023年   7篇
  2022年   24篇
  2021年   17篇
  2020年   6篇
  2019年   9篇
  2018年   12篇
  2017年   7篇
  2016年   10篇
  2015年   5篇
  2014年   7篇
  2013年   13篇
  2012年   7篇
  2011年   13篇
  2010年   11篇
  2009年   7篇
  2008年   10篇
  2007年   7篇
  2006年   8篇
  2005年   6篇
  2004年   9篇
  2003年   16篇
  2002年   4篇
  2001年   9篇
  2000年   6篇
  1999年   3篇
  1998年   2篇
  1997年   1篇
  1996年   3篇
  1995年   2篇
  1994年   1篇
  1992年   3篇
  1990年   1篇
  1984年   1篇
  1982年   1篇
  1975年   1篇
排序方式: 共有249条查询结果,搜索用时 31 毫秒
71.
72.
Gamma ray transitions de-exciting states in the N = Z nucleus 70Br have been identified for the first time using the GASP and EUROBALL arrays coupled with ancillary detectors. The level scheme of 70Br has been established by means of particle-gated γ-γ and γ-γ-γ coincidences. The Coulomb energy differences between isobaric analogue states in 70Br and 70Se show a deviation from the expected behaviour which could be related to dripline effects. Received: 18 July 2001 / Accepted: 25 September 2001  相似文献   
73.
By using the fusion-evaporation reaction 28Si(36Ar,p3n) and spectroscopy of β-delayed γ-rays and charged particles on mass-separated sources, β-decay properties of the neutron-deficient isotope 60Ga were studied for the first time. The half-life of 60Ga was determined to be 70(15) ms, and, based on βγγ coincidences, the isobaric-analogue state in 60Zn was identified at 4851.9(7) keV. A semiempirical proton separation energy value of 40(70) keV was deduced for 60Ga. The experimental results on half-life, mass excess, proton separation energy, and structure of the 60Zn daughter states are discussed in comparison with various model predictions, including large-scale shell model calculations. Received: 4 September 2001 / Accepted: 12 November 2001  相似文献   
74.
The standard enthalpies of combustion and formation of cellulose acetates with different degrees of acetylation are determined. It is established that there is a proportional dependence of these thermochemical characteristics vs. the degree of acetylation, weight fraction of bonded acetic acid, and molar mass of the repeating unit of cellulose acetates.  相似文献   
75.
At the interaction of bis (η5-cyclopentadienyl)vanadium with iodobenzoic acid or trimethylsilyl o-iodobenzoate in toluene depending on the ratio of the initial reagents bis(η5-cyclopentadienyl)vanadium(o-iodobenzoate) or η5-cyclopentadienylvanadium-bis-o-iodobenzoate were obtained in high yields. The latter was also formed in the reaction of bis(η5-cyclopentadiene)vanadium dihloride with trimethylsilyl o-iodobenzoate.  相似文献   
76.
A thorough study of the photophysical and laser properties of 8‐aminoboron dipyrromethene dyes was undertaken to determine the role of amine substitution and spatial disposition on the properties of the dyes. It was found that the fluorescent and laser response varied significantly. Although primary amines give rise to highly fluorescent products at the blue edge of the visible region, secondary amines yield nonfluorescent analogues in polar media. The crystal structures of two analogues are reported and described. Steric hindrance and the higher electron‐releasing ability of the amine favor the formation of a quenching intramolecular charge‐transfer state. Accordingly, boron dipyrromethene derivatives with primary amines exhibited laser emission with efficiencies of up to 44 %. Besides, the more efficient derivative was also the most photostable, leading to a significant improvement in the lasing performance with regard to previously reported 8‐aminoboron dipyrromethene derivatives. An increase in the solvent polarity, and mainly the presence of tertiary cyclic amines, led to a dramatic decrease or even the loss of the laser action.  相似文献   
77.
A speculative investigation has been presented to explore the salient features of magnetohydrodynamic (MHD) Prandtl‐Eyring nanofluid over stretching surface. Effects of Navier slip and convective boundary conditions are included in flow configuration. The effects of higher order chemical reactions along with Nield conditions are assumed in the concentration of nanoparticles. The mathematical modelling of the said flow problem accomplished the nonlinear partial differential equations along with appropriate boundary conditions. The nondimensional form of governing problem is yielded with the aid of similarity variables. The pivotal physical quantities, ie, velocity, temperature, and concentration (in nondimensional form), within boundary layer region are computed with shooting technique. The physical significance of flow controlling parameters on velocity, temperature, and concentration is illustrated through graphs. Additionally, thermophysical aspects of fluid near stretching surface (wall friction factor, wall heat flux, and wall mass flux) are instantiated graphically. A comparison of the current solution with reported data is established to validate the accuracy of adapted procedure. It is observed that the current findings agree with existing data. This led to confidence on adapted numerical procedure.  相似文献   
78.
Excited states of 108 Te were populated in the 54 Fe + 58 Ni (270 MeV) reaction using the NORDBALL detector array equipped with charged-particle and neutron detector systems for reaction channel separation. Gamma rays belonging to the neutron deficient nucleus 108 Te were identified for the first time. On the basis of γγ-coincidence and angular correlation relations a level scheme was constructed with tentative spin and parity assignments. The structure of the nucleus is discussed in the framework of systematics of heavier Te nuclei.  相似文献   
79.
The reactions 16O(7Li, 2n) and 16O(7Li, np) populating 21Na and 21Ne have been studied at E L=27 MeV using the GASP γ-detector array. The level schemes for 21Na and 21Ne have been extended to higher spin. The population of the bands with K=3/2 and 1/2, forming parity doublets, are compared. Preferential E1 decay between bands of opposite parity is observed in agreement with the octupole scenario. The structure of these bands can be interpreted as consisting of an instrinsic asymmetric (4He + 16O) structure with octupole deformation.  相似文献   
80.
This paper deals with one of the basic philosophical questions in modern cosmology: can the so-called “Anthropic Principle”, considered as an alternative to the classical teleology of creation, be an adequate explanation of the evidence that our universe is “fine-tuned” for the emergence of life and consciousness. The main problem with this principle is not its presumed teleology, as it is sometimes wrongly supposed, but quite the contrary: its intention to avoid teleological explanations by including the existence of many universes (“multiverse”) into extended cosmological models. After having compared logical and cosmological many-worlds concepts, this paper reaches the conclusion that the ontological reality of the “multiverse” is an even more problematic presupposition than some properly revised version of teleological causality. This in itself does not imply the classical theistic explanation of creation, since it also yields a pantheistic explanation of the emergence of life and consciousness in our universe.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号