全文获取类型
收费全文 | 1886篇 |
免费 | 63篇 |
国内免费 | 29篇 |
专业分类
化学 | 153篇 |
晶体学 | 3篇 |
力学 | 104篇 |
综合类 | 6篇 |
数学 | 294篇 |
物理学 | 1418篇 |
出版年
2024年 | 2篇 |
2023年 | 21篇 |
2022年 | 17篇 |
2021年 | 36篇 |
2020年 | 33篇 |
2019年 | 24篇 |
2018年 | 16篇 |
2017年 | 78篇 |
2016年 | 82篇 |
2015年 | 63篇 |
2014年 | 258篇 |
2013年 | 143篇 |
2012年 | 82篇 |
2011年 | 137篇 |
2010年 | 100篇 |
2009年 | 137篇 |
2008年 | 110篇 |
2007年 | 122篇 |
2006年 | 96篇 |
2005年 | 71篇 |
2004年 | 56篇 |
2003年 | 45篇 |
2002年 | 36篇 |
2001年 | 33篇 |
2000年 | 18篇 |
1999年 | 24篇 |
1998年 | 29篇 |
1997年 | 20篇 |
1996年 | 16篇 |
1995年 | 14篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 12篇 |
1991年 | 3篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1982年 | 2篇 |
排序方式: 共有1978条查询结果,搜索用时 15 毫秒
181.
LI Guohui CHEN Liaoyuan LUO Cuiwen 《核工业西南物理研究院年报(英文版)》2005,(1):82-84
In HL-2A tokamak experiment, high speed image acquisitoin system grabs images and shows them in real-time. It provides serial images of discharge to help scientists a lot to analyse the experiment. Neutral particle count system counts the number of neutral particles radiated from fusion plasmas. It provides the data to calculate the ion energy. 相似文献
182.
在遥感傅里叶变换红外光谱层析技术中,对于是否能够快速、经济地得出气体空间浓度分布图及预测浓度峰位置,重构算法的选择是至重要的。理想的重构算法即使在仪器噪声较大、存在测量误差、光线数量少以及待测气体在空间的分布不稳定情况下,也能够通过有限的测量数据和非对称的光线构型,得出理想的重构图。本文对遥感傅里叶变换红外光谱层析技术中采用的几种重构算法,如ART法、MART法、SIRT法和SBFM法等,作了扼要描述。与传统的ART法相比,MART法在迭代速度和迭代精度上有较大的优越性,SIRT法克服了采用代数重构技术所带来的模糊性,SBFM法使重构结果噪声明显减小。 相似文献
183.
定义L上加细的半拓扑生成序在GOH下的象和逆象,研究L上加细的拓扑共生结构的象和逆象,得到一些重要性质。 相似文献
184.
John J. Birmingham 《Journal of fluorescence》1997,7(1):45-54
Fluorescence lifetime imaging methodology has been successfully implemented at Unilever Research in a frequency-domain manner.
The experimental rig constructed comprises a wide-bandwidth electrooptic modulator operating on a CW argon-ion laser. The
modulated excitation with a typical upper modulation frequency limit of 200 MHz falls on macroscopic samples and the resultant
scattered light or fluorescence emission is then imaged onto a custom gain-modulatable image intensifier and slow-scan CCD
camera combination. Phase adjustment of the image intensifier relative to the laser modulator is achieved by the RF function
generator driving the intensifier. Both homodyne and heterodyne (500-Hz) strobing modes are employed to generate a double
image stack (scattered light reference and fluorescence emission) comprising an image sequence as a function of instrumental
phase difference. These image stacks are analyzed by Fourier least-squares methods to yield lifetime images by both phase
delay and normalized demodulation. Correct operation of the apparatus is deduced from the direct imaging of a quencher-induced
lifetime variation of BODIPY disulfonate over a range of concentrations. A typical industrially relevant sample, comprising
an investigation of the lifetime aspects of human dental enamel autofluorescence at 50MHz modulation frequency, is given.
This shows that there are real emission lifetime decreases of about 0.5 nsec in white-spot lesion areas compared to the surrounding
sound enamel. 相似文献
185.
At the personal dosimetry service of the ENEA Radiation Protection Institute, a fast neutron dosemeter based on chemically etched CR-39 (Poly Allyl Diglycol Carbonate) is operating since more than 20 years. Since then the track counting has been performed with a system consisting of a microscope, a video camera and an image analyser. A new automatic analysis system has been developed, based on automatic motion and vision tools and the programming language Labview 6, from National Instruments. The system selects the correct number of reading fields on the basis of a preliminary scan of the dosemeter, therefore operating motion and vision procedures in order to perform the analysis. For each reading field the system collects the track area distribution to which a previously optimised algorithm is applied, in order to correct the energy dependence of the response. For each dosemeter, a record containing the barcode and all data necessary for assessing the personal dose equivalent is stored in a routine file. Taking advantage of automatic vision and motion, a CR-39 reader with innovative features in terms of reproducibility, velocity and accuracy is now available even for the routine purposes of dosimetric services. 相似文献
186.
主动光学成象系统衬比传递特性及有效作用距离的分析 总被引:3,自引:0,他引:3
从传输介质对照明和成象光束衰减作用(吸收和散射)的分析入手,通过细致的定量分析,得出了主动系统(包括同轴和非同轴两架)成象材比传模型.这些模型都是将系统参数和衬比联系起来的明确的等式,而且还给出了精度较好的简化模型.这些模型可以为定量分析介质对成象的影响和有关系统设计提供有效而方便的理论工具. 相似文献
187.
本文讨论了带快门的内增强变象管相机的快门电路及其对扫描电路的干扰,干扰信号对相机性能指标的影响及解决方法。 相似文献
188.
Lagrangian duality can be derived from separation in the Image Space, namely the space where the images of the objective and
constraining functions of the given extremum problem run. By exploiting such a result, we analyse the relationships between
Wolfe and Mond-Weir duality and prove their equivalence in the Image Space under suitable generalized convexity assumptions.
相似文献
189.
The automatic image analysis system for scanning solid state nuclear track detectors is designed by utilizing a microdensitometer. The control of the entire system as well as the data analysis are accomplished with the IBM PC computer equipped with a FrameGrabber. The system counts the number of tracks and measures their geometrical parameters. The usage of the system is illustrated by counting rhombic tracks in mica detectors which were used for the investigation of the fusion–fission reaction 12C+ 208Pb. 相似文献
190.
We address in this paper the problem of defining belief functions, typically for multi-source classification applications in image processing. We propose to use mathematical morphology for introducing imprecision in the mass and belief functions while estimating disjunctions of hypotheses. The basic idea relies on the similarity between some properties of morphological operators and properties of belief functions. The framework of mathematical morphology guarantees that the derived functions have all required properties. We illustrate the proposed approach on synthetic and real images. 相似文献