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   266篇
  免费   3篇
化学   130篇
晶体学   9篇
力学   17篇
数学   33篇
物理学   80篇
  2021年   5篇
  2020年   4篇
  2019年   7篇
  2018年   4篇
  2017年   8篇
  2016年   7篇
  2015年   5篇
  2014年   10篇
  2013年   13篇
  2012年   11篇
  2011年   3篇
  2010年   4篇
  2009年   7篇
  2008年   13篇
  2007年   17篇
  2006年   6篇
  2005年   14篇
  2004年   13篇
  2003年   7篇
  2002年   8篇
  2001年   2篇
  2000年   5篇
  1999年   3篇
  1998年   2篇
  1997年   3篇
  1996年   2篇
  1995年   4篇
  1994年   7篇
  1993年   3篇
  1992年   2篇
  1991年   2篇
  1990年   4篇
  1989年   5篇
  1988年   4篇
  1987年   4篇
  1985年   6篇
  1984年   3篇
  1983年   4篇
  1982年   4篇
  1980年   2篇
  1978年   2篇
  1976年   3篇
  1975年   3篇
  1973年   6篇
  1971年   3篇
  1970年   2篇
  1969年   2篇
  1966年   1篇
  1965年   1篇
  1918年   2篇
排序方式: 共有269条查询结果,搜索用时 15 毫秒
81.
82.
We present a measurement of the polarization observed for bottomonium states produced in p-Cu collisions at square root of s = 38.8 GeV. The angular distribution of the decay dimuons of the Upsilon(1S) state shows no polarization at small values of the fractional longitudinal momentum x(F) and transverse momentum p(T) but significant positive transverse production polarization for either p(T)>1.8 GeV/c or for x(F)>0.35. The Upsilon(2S+3S) (unresolved) states show a large transverse production polarization at all values of x(F) and p(T) measured. These observations challenge NRQCD calculations of the polarization expected in the hadronic production of bottomonium states.  相似文献   
83.
Inferences made from analysis of BOLD data regarding neural processes are potentially confounded by multiple competing sources: cardiac and respiratory signals, thermal effects, scanner drift, and motion-induced signal intensity changes. To address this problem, we propose deconvolution filtering, a process of systematically deconvolving and reconvolving the BOLD signal via the hemodynamic response function such that the resultant signal is composed of maximally likely neural and neurovascular signals. To test the validity of this approach, we compared the accuracy of BOLD signal variants (i.e., unfiltered, deconvolution filtered, band-pass filtered, and optimized band-pass filtered BOLD signals) in identifying useful properties of highly confounded, simulated BOLD data: (1) reconstructing the true, unconfounded BOLD signal, (2) correlation with the true, unconfounded BOLD signal, and (3) reconstructing the true functional connectivity of a three-node neural system. We also tested this approach by detecting task activation in BOLD data recorded from healthy adolescent girls (control) during an emotion processing task.  相似文献   
84.
A generalized bounded variation characterization of Banach spaces possessing the Radon‐Nikodym property is given in terms of the average range. We prove that a Banach space X has the Radon‐Nikodym property if and only if for each function of generalized bounded variation on [0, 1], the average range is a nonempty set at almost all .  相似文献   
85.
Infrared and Raman spectra were obtained for the fluorinated ethanes, CF3CHFC? and CF3CHFBr, and their deuterated isotopomers. A vibrational assignment of these molecules is reported.  相似文献   
86.
Optical activity of n-pi transitions in polynucleotides   总被引:4,自引:0,他引:4  
  相似文献   
87.
A procedure for isolating the real roots of an equation is presented. The technique requires only function values and can be applied readily to complicated transcendental functions. A program implementing the technique is provided.  相似文献   
88.
89.
Ultraviolet photoemission spectra (UPS) are presented for condensed layers of three ethylated amines; mono‐, di‐, and triethylamine (TEA) on the Si(100) surface at 100 K. The photoemission peaks associated with the nitrogen lone pair electrons are identified in the amines and compared with the corresponding spectra for condensed ammonia. Shifts in the lone pair binding energy for the ethyl‐substituted amines are shown to be consistent with conventional chemical paradigms. Also, for comparison purposes spectra for two nonethylated amines, trimethylamine (TMA), and its silicon analog, trisilylamine (TSA), are presented and discussed. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
90.
Infrared laser action spectroscopy is used to characterize divalent calcium ions solvated by up to 69 water molecules. The spectrum for Ca(2+)(H2O)12 indicates that in the predominant structure, eight inner-shell water molecules solvate the metal ion and donate one hydrogen bond to one of four second-shell, double-acceptor water molecules. Eight-coordinate solvation is consistent with results from many condensed-phase studies, and contrasts with results for smaller gas-phase clusters that are most consistent with six-coordinate solvation. Each water molecule in this structure of Ca(2+)(H2O)12 coordinates with two other members of the cluster. With increasing cluster size, the number of two-coordinate water molecules decreases, whereas that of three-coordinate water molecules increases. The number of one-coordinate water molecules increases until n approximately 18, but they are essentially depleted by n approximately = 30. Spectra of the largest clusters, which have effective concentrations of divalent calcium that are less than 1 M, exhibit only subtle changes with increasing cluster size. The bonded-OH regions of these spectra are similar to, but blue-shifted from that of bulk water, whereas the free-OH regions are well-resolved and indicate that the surfaces of these clusters are well-structured. These results comprise the most extensive vibrational spectroscopic study yet performed on metal ion hydration in the gas phase and provide insights into metal ion solvation in bulk and interfacial environments.  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