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   212篇
  免费   85篇
  国内免费   14篇
化学   57篇
晶体学   2篇
力学   16篇
综合类   1篇
数学   19篇
物理学   216篇
  2023年   1篇
  2022年   3篇
  2021年   10篇
  2020年   3篇
  2019年   7篇
  2018年   10篇
  2017年   9篇
  2016年   13篇
  2015年   10篇
  2014年   23篇
  2013年   35篇
  2012年   11篇
  2011年   14篇
  2010年   13篇
  2009年   19篇
  2008年   12篇
  2007年   17篇
  2006年   9篇
  2005年   16篇
  2004年   6篇
  2003年   9篇
  2002年   6篇
  2001年   9篇
  2000年   5篇
  1999年   5篇
  1998年   6篇
  1997年   5篇
  1996年   4篇
  1995年   1篇
  1994年   2篇
  1993年   4篇
  1992年   5篇
  1991年   1篇
  1990年   2篇
  1989年   2篇
  1988年   1篇
  1986年   1篇
  1980年   1篇
  1976年   1篇
排序方式: 共有311条查询结果,搜索用时 15 毫秒
31.
Angular distributions for the 163Dy(t,p) and 177Hf(t,p) reactions were measured using 17 MeV tritons from the McMaster University Tandem Van de Graaff accelerator. Reaction products were analyzed with a magnetic spectrograph and detected with photographic emulsions. Favored L=0 transitions confirmed assignments of the 5/2[523] band in 165Dy and 7/2[514] band in 179Hf. Additional L=0 transitions in each nuclide identified previously unknown 5/2 levels in 165Dy and 7/2 ones in 179Hf. Overall trends of L=0 strengths support the existence of subshell closures at neutron numbers 98 and 108. On the basis of a relatively strong L=2 transition, the Kπ=11/2 γ-vibration based on the 7/2[514] state is identified at 1689 keV in 179Hf, about 440 keV above its previously-assigned Kπ=3/2 partner.  相似文献   
32.
An analysis of data of target fragments of 28Si-AgBr (at 14.5 AGeV) reveals the existence of emission asymmetry in the azimuthal plane, which is found to depend on the number of target fragments. The comparison with the data of 32S-AgBr (at 200 AGeV) and 16O-AgBr (at 60 AGeV) interactions indicates that emission asymmetry depends on the projectile mass and energy.  相似文献   
33.
焊接变形光学测量技术研究   总被引:1,自引:0,他引:1  
针对薄板焊接变形测量难的问题,提出了一种非接触式三维光学实时测量薄板焊接变形的新方法。首先通过2个高分辨率高速数字相机从不同观察点同时拍摄物体运动的视频图像;然后运用三维重建技术,包括共线方程、基于共面方程的像片定向、直接线性变换解法、外极线几何约束和光束平差解法等重建待测标志点的三维坐标;最后依据同名点将不同时刻薄板的变形状态关联起来,计算出待观测点的焊接变形量,并实时绘制显示出变形曲线。与传统方法相比,该方法具有不受焊接温度及强烈干扰影响和实时、高效、高精度等优点。  相似文献   
34.
Unter Verwendung von Indiumphthalocyanin als Target wurde der Anreicherung von 114mIn durch den Szilard-Chalmers-Prozeβ untersucht. Bei Bestrahlung in der Spaltzone des Kernreaktors gelang es, spezifische Aktivitäten zu erzielen, die ohne Anreicherung nur durch sehr lange Bestrahlungszeiten erreicht werden können. Die Abhängigkeit der spezifischen Aktivität der spezifischen Aktivität von der Bestrahlungs zeit, von der Art und der Vorbehandlung der Targetverbindung, von der Dauer der Lagerung der bestrahlten Proben und von der Abtrennmethode wird angegeben.  相似文献   
35.
Es werden methodische Untersuchungen zur Entwicklung eines Monte-Carlo-Programmes zur Berechnung der Tiefen-verteilung der primären Ionisationen auf der Grundlage der Vielfachstreutheorie von Molière beschrieben. Anhand aus-gewählter Zwei-Element-Targets wird die Leistungsfähigkeit von drei Varianten eines entsprechenden Elektronentrans-portmodells untersucht. Unter Benutzung der entwickelten Elektronentransportmodelle werden für die Elektronenstrahl-mikroanalyse interessierende Größen, wie Rückstreukoeffizient, Rückstreufaktor und Absorptionskorrektion, berechnet.  相似文献   
36.
A substoichiometic analytical method of high sensitivity combined with adsorptive sampling has been worked out for the determination of traces of silver in palladium making use of the selective deposition of microquantities of silver from aqueous solutions of palladium salts on cathodically polarized platioum surfaces. The stability and reporducibility of the saturation values of deposited silver are practially independent of the content and concentration of silver and palladium in the solution. The sensitivity proved to be 0.01 ppm, the accuracy ± 30 per cent.  相似文献   
37.
Abstract

The range and energy-loss of 16.34 MeV/u 238U in Kapton-polyamide plastic have been measured by the nuclear track technique. The experimental ranges are compared with two sets of theoretical values. It has been observed that ranges obtained from the computer code ‘DEDXT’ are found to be 5–8% lower as compared to measured ones whereas those from Northcliffe and Schilling are about 10–15% overestimated above 8 MeV/u.  相似文献   
38.
We consider a general optimal switching problem for a controlled diffusion and show that its value coincides with the value of a well-suited stochastic target problem associated to a diffusion with jumps. The proof consists in showing that the Hamilton–Jacobi–Bellman equations of both problems are the same and in proving a comparison principle for this equation. This provides a new family of lower bounds for the optimal switching problem, which can be computed by Monte-Carlo methods. This result has also a nice economical interpretation in terms of a firm's valuation.  相似文献   
39.
The complexity of biological samples determines that the detection of a single biomolecule is unable to satisfy actual needs. Moreover, the “false positives” results caused by a single biomolecule detections easily leads to erroneous clinical diagnosis and treatment. Thus, it is important for the homogenous quantification of multiple biomolecules in not only basic research but also practical application. As a consequent, a large number of literatures have been exploited to monitor multiple biomolecules in homogenous solution, enabling facilitating the development of the disease diagnosis, treatment as well as drug discovery. One-dimensional nanomaterials and two-dimensional nanomaterials have special physical and chemical properties, such as good electrochemical properties, stable structure, large specific surface area, and biocompatibility, which are widely used in electrochemical and fluorescent detection of biomolecules. This tutorial review highlights the recent development for the detection of multiple biomolecules by using nanomaterials including one-dimensional materials (1DMs) as well as two-dimensional materials (2DMs).  相似文献   
40.
Lipid metabolism has a significant function in the central nervous system and Alzheimer's disease (AD) is an age-related senile disease characterized by central nerve degeneration. The pathological development of AD is closely related to lipid metabolism disorders. To reveal the influence of Kai-Xin-San (KXS) on lipid metabolism in APP/PSI transgenic mice and potential therapeutic targets for treating AD, brain tissue samples were collected and analyzed by high-throughput lipidomics based on UPLC–Q/TOF-MS. The collected raw data were processed by multivariate data analysis to discover the potential biomarkers and lipid metabolic profiles. Compared with the control wild-type mouse group, nine potential lipid biomarkers were found in the AD model group, of which seven were up-regulated and two were down-regulated. Orally administrated KXS can reverse the changes in these potential biomarkers. Compared with the model group, a total of six differential metabolites showed a recovery trend and may be potential targets for KXS to treat AD. This study showed that high-throughput lipidomics can be used to discover the perturbed pathways and lipid biomarkers as potential targets to reveal the therapeutic effects of KXS.  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