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   9998篇
  免费   1466篇
  国内免费   871篇
化学   3850篇
晶体学   136篇
力学   337篇
综合类   27篇
数学   643篇
物理学   7342篇
  2024年   8篇
  2023年   87篇
  2022年   111篇
  2021年   132篇
  2020年   169篇
  2019年   194篇
  2018年   203篇
  2017年   272篇
  2016年   332篇
  2015年   305篇
  2014年   449篇
  2013年   830篇
  2012年   558篇
  2011年   706篇
  2010年   521篇
  2009年   705篇
  2008年   704篇
  2007年   799篇
  2006年   673篇
  2005年   557篇
  2004年   530篇
  2003年   418篇
  2002年   427篇
  2001年   347篇
  2000年   368篇
  1999年   299篇
  1998年   256篇
  1997年   159篇
  1996年   195篇
  1995年   155篇
  1994年   127篇
  1993年   103篇
  1992年   110篇
  1991年   75篇
  1990年   53篇
  1989年   50篇
  1988年   61篇
  1987年   43篇
  1986年   36篇
  1985年   38篇
  1984年   37篇
  1983年   13篇
  1982年   25篇
  1981年   32篇
  1980年   7篇
  1979年   9篇
  1978年   10篇
  1977年   6篇
  1976年   8篇
  1973年   9篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
The magnitude of spectral change in blood glucose measurements with diffuse reflectance spectroscopy is investigated. Spectral change is estimated by simulation of light propagation in skin tissue and measurements of absorbance spectra of aqueous glucose solution. Required sensitivity of spectrophotometers for monitoring change in the blood glucose concentration as small as 10 mg/dL has been obtained using the estimated change in the absorbance spectrum and mean pathlength of light in tissue.  相似文献   
992.
利用可加性规则,使用HartreeFock波函数,采用由束缚原子概念修正过的复光学势(由静 电势、交换势、修正极化势及吸收势这四部分组成),在较大的能量(30—5000eV)范围内对 电子被甲烷及氯代甲烷(CH4,CCl4,CHCl3,CH2Cl2和CH 3Cl)散射的总截面进行了计算,且将计算结果与实验结果及其他理论计算 结果进行 了比较.结果表明,利用被束缚原子概念修正过的复光学势及可加性规则进行计算,所得结 果的精度要比利用未被束缚原子概念修正的复光学势及可加性规则进行计算得到的结果好很 多.因此,在复光学势中采用束缚原子概念可提高电子被分子散射的总截面的计算准确度. 关键词: 电子散射 可加性规则 束缚原子 总截面  相似文献   
993.
The integrodifferential equation method is used to study the spectrum of a nanoparticle colloid for the example of interaction of three arbitrarily arranged dielectric particles made up of nonresonant atoms (the eigenfrequency of the transition is far from the emission frequency) with incorporated barium atoms in an external optical radiation field. The effect on the light-scattering properties of a nanosphere in the ensemble of its distant “neighbors” is studied; an additional peak associated with them is observed as a frequency close to the resonance for an isolated nanosphere, which under certain conditions has higher intensity than the main peak corresponding to optical near-field resonance in a two-particle system. The dependence of the spectrum of the nanosized system on the geometric structure is studied, and it is shown that very precise tuning of the resonance frequency is possible by varying the angular distribution of the particles. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 5, pp. 641–646, September–October, 2006.  相似文献   
994.
We have studied the ratio of the intensities of radiation scattered by a layer of blood in a cuvet and by the cuvet walls for normal incidence or incidence at the Brewster angle for probing radiation from a He-Ne laser, linearly polarized in the plane of incidence (plane of observation) or orthogonal to that plane. We have compared it with the intensity of the radiation reflected by the surface of the cuvet wall, as estimated based on the geometric approximation. We have found the optimal conditions for probing and observing scattering for the layer in a cuvet, where such conditions are characterized by a minimal effect from the cuvet walls and the maximum ratio of useful signal to background. Report given at the Fifth International Scientific and Technical Conference on Quantum Electronics, 22–25 November 2004, Minsk, Belarus. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 2, pp. 270–272, March–April, 2006.  相似文献   
995.
We investigate the scattering process of impulse in vertical granular chain with light impurities. When the perturbation is weak, the quantities describing the reflection rate exhibit power-law behavior with the impurity depth. The exponent is nearly independent of vi. When the perturbation is very strong, the vertical chain shows similar behavior to that of the horizontal chain, so the exponent is nearly zero. Our numerical investigation begins from the weak perturbation region and extends to the nonlinear region and found a peak of the exponent. The difficulty in extending the numerical investigation to a stronger perturbation region is analyzed.PACS numbers: 45.70.-n, 43.25. y, 46.40.Cd  相似文献   
996.
The physical meaning of bare and dressed scattering matrix singularities has been investigated. Special attention has been attributed to the role of the well-known invariance of the scattering matrix with respect to the field transformation of the effective Lagrangian. Examples of evaluating bare and dressed quantities in various models are given.  相似文献   
997.
1 Introduction  Ifalightbeam passesthroughtheparticulatetransparentmedium ,itsintensitywillbeweakenedbecauseoftheextinctionofparticles[1] .Thisphenomenoniscausedbythescatteringandabsorptionof particles.Thescatteringelectromagneticwavesarediffusedinspaceal…  相似文献   
998.
Angle distributions of the degree and azimuth of polarization of radiation scattered by individual leaves were measured. The polarization characteristics of the reflected radiation were investigated at four radiation wavelengths (460, 550, 680, and 740 nm) and angles of exposure of leaves to light of 60–70°. The experiments were performed with leaves of maples (Acer platonoides) at different stages of vegetation and withering. More than 1000 distributions of the spectral polarization characteristics of the reflected radiation were obtained for maple leaves taken from regions with different ecological conditions during 1993–1995 It was established that the spectral polarization characteristics of the radiation scattered by a leaf markedly change with the state of the leaf. Belarusian State University, 4, F. Skorina Ave., Minsk, 220080, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 1, pp. 107–113, January–February, 1998.  相似文献   
999.
We consider small oscillations of a system of pairwise interacting particles in an external field near a stable equilibrium. The system is assumed to consist of finitely many channels, i.e., semi-infinite linear chains of particles, attached to a scatterer, which is a finite system of interacting particles. Direct and inverse scattering problems are considered. In particular, an algorithm finding characteristics of the channels on the basis of scattering data is given.  相似文献   
1000.
The adsorption of potassium on Fe(100) was studied by time-of-flight forward scattering and recoiling spectroscopy (TOF-SARS), low energy electron diffraction (LEED) and Auger electron spectroscopy (AES). After heating to 650 K of the potassium saturated surface the formation of a p(3 × 3) potassium superstructure was observed by LEED. TOF-SARS experiments ruled out the adsorption of potassium in the on-top, bridge and four-fold hollow site. The only site which is in agreement with all experimental results is the substitutional site where K replaces an Fe atom of the topmost layer of the crystal. This is the first time a substitutional adsorption site has been found on a bcc surface. On an fcc surface such an adsorption site has been found recently for adsorption of sodium and potassium on Al(111).  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