全文获取类型
收费全文 | 66篇 |
免费 | 15篇 |
国内免费 | 2篇 |
专业分类
化学 | 11篇 |
力学 | 4篇 |
数学 | 5篇 |
物理学 | 63篇 |
出版年
2023年 | 1篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 1篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 4篇 |
2014年 | 5篇 |
2013年 | 5篇 |
2012年 | 5篇 |
2011年 | 4篇 |
2010年 | 4篇 |
2009年 | 4篇 |
2008年 | 2篇 |
2007年 | 2篇 |
2006年 | 3篇 |
2005年 | 5篇 |
2004年 | 4篇 |
2003年 | 5篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有83条查询结果,搜索用时 15 毫秒
41.
针对大中口径舰炮对海射击训练时,缺少设备测量相对靶船中心的弹丸落点散布精度,提出了一种利用舰载光电跟踪仪交汇测量方法。以靶船型值为基准,利用靶船型值在屏幕上的像素尺寸,求出相对光电跟踪仪电视中心的弹着点线及偏置角,将两艘舰艇光电跟踪仪分别测量出的两条弹着点线相交,即可求出相对于靶船中心的脱靶量。给出了交会测量弹着水柱的数学模型,对测量精度进行了分析,计算结果表明脱靶量误差小于3m。 相似文献
42.
Wenjun Chen Yaqing Yang Guozhu Cai Yajun Zheng Shaoming Wang Jiandong Yuan 《辐射效应与固体损伤》2013,168(9-10):809-818
ABSTRACTWuwei heavy ion therapy center is the first Chinese heavy ion accelerator facility developed for cancer therapy, in which four terminals are distributed and the height of the vertical terminal is up to 18?m. Installation units of vertical terminal are diverse and complex, moreover, these units present poor alignment visibility. Thereby, it is difficult to perform the alignment among these components. Based on the laser tracker and high precision three-dimensional surveying control network, this paper proposes an efficient alignment method using multiple conversion of magnet fiducial data and pre-alignment of complex magnet unit. All the components are successfully aligned, and meanwhile the installation efficiency of vertical terminals is improved. Alignment accuracy of magnets is less than 0.1?mm. Error analysis presents that this alignment method achieves its goal. 相似文献
43.
当激光跟踪仪应用于多传感器三维视觉测量系统的全局标定时,由于标定现场环境复杂,靶标球镜面区域所成光斑随环境光强、视觉测量系统观察角度和激光投射角度的变化而改变,给靶标球镜面中心的准确定位提出了很大的挑战。设计了一种对光照变化不敏感、对激光点形状和光强分布无要求的靶标球镜面中心定位方法。该方法首先利用图像分割法准确定位靶标球所在区域,然后对该区域进行滤波,去除图像中的噪声并增强靶标球与背景的对比度,之后进行靶标球分割和强反光区域去除,通过图像形态学处理得到靶标球镜面区域,最后对该区域的像素坐标进行统计,得到镜面中心定位坐标。实验采用79幅复杂多变的镜面区域光斑图像进行实验验证,该方法正确定位率可达到91.2%,其中平均定位误差RMS低于0.74像素,基本满足全局标定对靶标球镜面中心定位精度的要求。 相似文献
44.
DONG Yi-Fan ZHANG Fei QIAO Rui PENG Wen-Xi FAN Rui-Rui GONG Ke WU Di WANG Huan-Yu 《中国物理C(英文版)》2015,39(11):116202-116202
The Dark Matter Particle Explorer(DAMPE) is an upcoming scientific satellite mission for high energy gamma-ray, electron and cosmic ray detection. The silicon tracker(STK) is a subdetector of the DAMPE payload.It has excellent position resolution(readout pitch of 242 μm), and measures the incident direction of particles as well as charge. The STK consists of 12 layers of Silicon Micro-strip Detector(SMD), equivalent to a total silicon area of6.5 m2. The total number of readout channels of the STK is 73728, which leads to a huge amount of raw data to be processed. In this paper, we focus on the on-board data compression algorithm and procedure in the STK, and show the results of initial verification by cosmic-ray measurements. 相似文献
45.
在简要分析和对比各种检测导轨直线度方法的基础上,提出利用激光跟踪仪测量超长导轨直线度的方法,对该方法的基本原理和实现步骤进行了分析和研究。结合工程实例,对一数控机床的20 m超长导轨进行了直线度测量,得到其2个方向上的直线度分别为27 m和25 m。该方法拓宽了激光跟踪仪的现有功能,能精确快速地完成对超长导轨直线度的检测,并可以实现对超长导轨2个方向直线度的分离,测量导轨的长度可达到70 m,检测精度为0.4 m/m。 相似文献
46.
Structure and Action Mechanism of Ligninolytic Enzymes 总被引:2,自引:0,他引:2
Wong DW 《Applied biochemistry and biotechnology》2009,157(2):174-209
Lignin is the most abundant renewable source of aromatic polymer in nature, and its decomposition is indispensable for carbon
recycling. It is chemically recalcitrant to breakdown by most organisms because of the complex, heterogeneous structure. The
white-rot fungi produce an array of extracellular oxidative enzymes that synergistically and efficiently degrade lignin. The
major groups of ligninolytic enzymes include lignin peroxidases, manganese peroxidases, versatile peroxidases, and laccases.
The peroxidases are heme-containing enzymes with catalytic cycles that involve the activation by H2O2 and substrate reduction of compound I and compound II intermediates. Lignin peroxidases have the unique ability to catalyze
oxidative cleavage of C–C bonds and ether (C–O–C) bonds in non-phenolic aromatic substrates of high redox potential. Manganese
peroxidases oxidize Mn(II) to Mn(III), which facilitates the degradation of phenolic compounds or, in turn, oxidizes a second
mediator for the breakdown of non-phenolic compounds. Versatile peroxidases are hybrids of lignin peroxidase and manganese
peroxidase with a bifunctional characteristic. Laccases are multi-copper-containing proteins that catalyze the oxidation of
phenolic substrates with concomitant reduction of molecular oxygen to water. This review covers the chemical nature of lignin
substrates and focuses on the biochemical properties, molecular structures, reaction mechanisms, and related structures/functions
of these enzymes.
Reference to a company and/or products is only for purposes of information and does not imply approval of recommendation of
the product to the exclusion of others that may also be suitable. All programs and services of the US Department of Agriculture
are offered on a nondiscriminatory basis without regard to race, color, national origin, religion, sex, age, marital status,
or handicap. 相似文献
47.
48.
Quintessence field is a widely-studied candidate of dark energy. There is ``tracker solution' in quintessence models, in which evolution of the field ø at present times is not sensitive to its initial conditions. When the energy density of dark energy is neglectable (Ωø<< 1), evolution of the tracker solutioncan be well analysed from ``tracker equation'. In this paper, we try tostudy evolution of the quintessence field from ``full tracker equation',which is valid for all spans of Ωø. We get stable fixed points of wø and Ωø (noted as \hat{w}ø and \hat{Ω}ø) from the ``full tracker equation', i.e., wø and Ωø will always approach \hat{w}ø and \hat{Ω}ø respectively. Since \hat{w}ø and \hat{Ω}ø are analytic functions of ø, analytic relation of \hat{w}ø ~ \hat{Ω}ø can be obtained, which is a good approximation for the wø ~ Ωø relation and can be obtained for the most type of quintessence potentials. By using this approximation, we find that inequalities \hat{w}ø < wø and \hat{Ω}ø < Ωø are statisfied if the wø (or \hat{w}ø) decreases with time. In this way, the potential U(ø) can be constrained directly from observations, by no need of solving the equations of motion numerically. 相似文献
49.
报道了一套适用于激光外差辐射计的高精度太阳跟踪仪,为激光外差辐射计提供用以反演大气成分的柱浓度和垂直廓线的太阳光。太阳跟踪系统采用太阳运行轨迹跟踪与光电跟踪相结合的跟踪方式,具有精度高、全时空特点。测量了该太阳跟踪仪的跟踪精度,X和Y轴方向跟踪精度分别达到0.068°和0.06°,能够满足激光外差辐射计在大气和天文领域中对太阳光收集的要求。进而把太阳跟踪仪与实验室研制的激光外差辐射计集合起来,测量了3.5 μm附近的太阳光谱,得到了CH4在整层大气中的吸收情况,为下一步反演整层大气中CH4的柱浓度和垂直廓线奠定了基础。 相似文献
50.
Fluorescent Phosphorus Dendrimer as a Spectral Nanosensor for Macrophage Polarization and Fate Tracking in Spinal Cord Injury
下载免费PDF全文
![点击此处可从《Macromolecular bioscience》网站下载免费的PDF全文](/ch/ext_images/free.gif)