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   204篇
  免费   11篇
化学   119篇
晶体学   7篇
力学   7篇
数学   26篇
物理学   56篇
  2022年   6篇
  2021年   8篇
  2020年   6篇
  2019年   5篇
  2018年   3篇
  2017年   4篇
  2016年   17篇
  2015年   9篇
  2014年   11篇
  2013年   10篇
  2012年   12篇
  2011年   15篇
  2010年   12篇
  2009年   14篇
  2008年   9篇
  2007年   17篇
  2006年   14篇
  2005年   9篇
  2004年   9篇
  2003年   7篇
  2001年   5篇
  2000年   2篇
  1999年   3篇
  1997年   2篇
  1996年   1篇
  1992年   2篇
  1989年   1篇
  1988年   1篇
  1974年   1篇
排序方式: 共有215条查询结果,搜索用时 31 毫秒
121.
Rhizomelic chondrodysplasia punctata is a member of genetic peroxisomal disorders. Delayed myelination, which is probably related to the inadequacy of plasmalogens biosynthesis, is an important feature of this disorder. Direct assessment of neuropathologic aspects of RCDP syndrome such as neuronal degeneration and delayed myelination is possible with MR spectroscopy.In this report, MR spectroscopy findings (decreased Cho/Cr and increased Ins-Gly/Cr ratios and increased levels of mobile lipids) of a rhizomelic chondrodysplasia punctata case supporting delayed myelination are presented. This is the second report of MR spectroscopy examination of the specific brain metabolic changes associated with rhizomelic chondrodysplasia punctata.  相似文献   
122.
To determine whether differences exist between neurofibromatosis type 1 (NF1) patients with or without focal lesions and healthy normal volunteers in the metabolite ratios of normal appearing white matter, 27 patients with NF1 (with parenchymal lesion, MR positive, n: 17; without parenchymal lesions, MR negative, n: 10) and 20 healthy volunteers underwent MRI and short TE (31 ms) proton MR spectroscopy (MRS). In 17 patients with parenchymal lesions, 61 focal lesions were detected by MRI. MRS was performed from normal appearing frontal and posterior parietal white matter (FWM and PWM) in NF1 and from control groups. NAA/Cr, Cho/Cr and MI/Cr ratios were calculated. Significant increase in Cho/Cr and MI/Cr ratios were found in FWM and PWM in MR negative and positive groups when compared to control group. NAA/Cr ratio in MR positive group was significantly decreased in FWM compared to control group. There were no significant differences between FWM and PWM in all metabolite ratios of MR negative group. MI/Cr ratio in MR positive group was significantly elevated in PWM compared to FWM. Metabolite changes detected by MRS could indicate demyelination and gliosis in normal appearing white matter in all NF1 patients, and additionally neuroaxonal damage in the FWM of NF1 patients with focal lesions. For that reason, in the clinical evaluation and follow-up of these patients MRS features of normal appearing white matter should be considered in addition to focal lesions.  相似文献   
123.
We show that two of the nonlinear lattice equations studied by Ayhan & Bekir [Commun Nonlinear Sci Numer Simulat 17 (2012) 3490–3498] have already been investigated by Aslan [Commun Nonlinear Sci Numer Simulat 15 (2010) 1967–1973] using an improved version of the same method. The solutions obtained by the latter one include the solutions obtained by the former one.  相似文献   
124.
Structural Chemistry - The electronic structure and electronic transitions of four new mono Schiff base derivatives are interpreted by using absorption and fluorescence spectra including 28...  相似文献   
125.
126.
Recently, many important nonlinear partial differential equations arising in the applied physical and mathematical sciences have been tackled by a popular approach, the so-called Exp-function method. In this paper, we present some shortcomings of this method by analyzing the results of recently published papers. We also discuss the possible improvement of the effectiveness of the method.  相似文献   
127.
In this paper, we demonstrate the effectiveness of the so-called (G′/G)-expansion method by examining some nonlinear evolution equations with physical interest. Our work is motivated by the fact that the (G′/G)-expansion method provides not only more general forms of solutions but also periodic and solitary waves. If we set the parameters in the obtained wider set of solutions as special values, then some previously known solutions can be recovered. The method appears to be easier and faster by means of a symbolic computation system.  相似文献   
128.
In this rapid communication we describe a new approach to protein detection with chemiluminescence. By combining common practices in protein detection with chemiluminescence, microwave technology, and metal-enhanced chemiluminescence, we show that we can use low power microwaves to substantially increase enzymatic chemiluminescent reaction rates on metal substrates. As a result, we have found that we can in essence trigger chemiluminescence with low power microwave (Mw) pulses and ultimately, perform on-demand protein detection assays. Using microwave triggered metal-enhanced chemiluminescence (MT-MEC), we not only improve the sensitivity of immunoassays with enhanced signal-to-noise ratios, but we also show that we can accurately quantify protein concentrations by integrating the photon flux for discrete time intervals.  相似文献   
129.
The metal content of Colorado potato beetles elytra in Turkey was determined using the energy dispersive X-ray fluorescence method. A radioisotope excited X-ray fluorescence analysis using the method of standard addition is applied for the elemental analysis of Colorado potato beetles elytra. An annular 241Am radioactive source and an annular 55Fe radioactive source were used for excitation of characteristic K X-rays. An Si(Li) detector which has a full-width at half-maximum for photons was used for intensity measurements. The procedure of sample preparation and the results of analysis were presented.  相似文献   
130.
With the aid of symbolic computation system Mathematica, several explicit solutions for Fisher's equation and CKdV equation are constructed by utilizing an auxiliary equation method, the so called G′/G-expansion method, where the new and more general forms of solutions are also constructed. When the parameters are taken as special values, the previously known solutions are recovered.  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