全文获取类型
收费全文 | 11107篇 |
免费 | 2456篇 |
国内免费 | 4416篇 |
专业分类
化学 | 8315篇 |
晶体学 | 584篇 |
力学 | 908篇 |
综合类 | 369篇 |
数学 | 1914篇 |
物理学 | 5889篇 |
出版年
2024年 | 35篇 |
2023年 | 109篇 |
2022年 | 451篇 |
2021年 | 429篇 |
2020年 | 371篇 |
2019年 | 389篇 |
2018年 | 359篇 |
2017年 | 552篇 |
2016年 | 353篇 |
2015年 | 573篇 |
2014年 | 694篇 |
2013年 | 924篇 |
2012年 | 939篇 |
2011年 | 967篇 |
2010年 | 1007篇 |
2009年 | 1078篇 |
2008年 | 1238篇 |
2007年 | 1031篇 |
2006年 | 1090篇 |
2005年 | 863篇 |
2004年 | 623篇 |
2003年 | 480篇 |
2002年 | 430篇 |
2001年 | 604篇 |
2000年 | 592篇 |
1999年 | 329篇 |
1998年 | 158篇 |
1997年 | 151篇 |
1996年 | 125篇 |
1995年 | 117篇 |
1994年 | 139篇 |
1993年 | 98篇 |
1992年 | 94篇 |
1991年 | 64篇 |
1990年 | 77篇 |
1989年 | 86篇 |
1988年 | 65篇 |
1987年 | 51篇 |
1986年 | 45篇 |
1985年 | 25篇 |
1984年 | 37篇 |
1983年 | 30篇 |
1982年 | 15篇 |
1981年 | 20篇 |
1980年 | 10篇 |
1979年 | 15篇 |
1977年 | 5篇 |
1965年 | 5篇 |
1962年 | 4篇 |
1957年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Modulation Frequency Multiplexed Tunable Diode Laser Spectroscopy System for Simultaneous CO, CO2 Measurements
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A modulation frequency multiplexed dual diode-laser system is developed for simultaneous detection of the two most common fire gas products CO and CO2. Simultaneous detection is achieved by modulating each laser at different frequencies, demodulating the signal by a pair of lock-in amplifiers for each gas. Laser beams are combined and detected by one detector after passing through an identical optical path. The experimental results show little performance degradation associated with modulation frequency multiplexing, and no cross-talk between the two multiplexed detection channels is measured. 相似文献
102.
氢化物原子荧光法(HG-AFS)测定鸡蛋中的硒 总被引:4,自引:0,他引:4
本文建立了一种HG-AFS法测定食疗蛋中硒的方法,该方法简单,快速,同时也提高了分析的灵敏度。方法的检出限为0.3μg/L,食疗蛋中硒的样品测定的相对标准偏差<10%,回收率在90%以上。 相似文献
103.
104.
本文应用表面分析技术研究HL-1装置中SiC涂层的等离子体辐照性能。结果表明,SiC材料应用于孔栏和壁涂层有利于减少杂质和提高等离子体品质。 相似文献
105.
NongYueHE JianXinTANG SongLI HongCHEN AnCunZHOU 《中国化学快报》2005,16(3):397-400
Polypropylene microporous membranes were treated with plasma in a mixture of N2 and H2 (1:2 in volume). Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and ultra-violet (UV) spectra demonstrated the success of grafting amino groups. The density of the polar amino groups on the membrane surface is about 0.59 μmol/cm^2. The as-treated membranes were successively applied to the in situ synthesis of oligonucleotides and an average coupling yield was more than 98%. The surface feature of the treated membrane is suggested to be responsible for its advantage over a glass slide. 相似文献
106.
Pinning effect of lead lanthanum titanate (PLT) ferroelectric thin films with excess PbO of 20 mol% has been studied for deposition on diffe rent substrates. Silicon, sapphire and quartz were used as substrates on which P t/Ti or LaNiO3 thin films were deposited as bottom electrodes. Electron probe analysis results showed that there was still a certain amount of excess Pb in PLT films after annealing at 550 ℃ for 1 h, and the amount of it was dependent on the substrate used. The distribution of excess Pb in the films was investig ated by Auger electron spectroscopy depth profile. It was shown that the substrates and the bottom electrodes had significant effects on the content and distrib ution of excess Pb in PLT films. The excess Pb and its accumulation at the inter face between the film and bottom electrode may act as pinning centers and have a pinning effect on domains, which can be observed by abnormal P-E hysteresis loops and abnormal C-V curves. The excess Pb content in the films and the accumulation of Pb at the interface were high in PLT films deposited on Pt/Ti/S i, and considerable pinning effect was observed. As LaNiO3 would absorb most part of the excess Pb in PLT films, the content of excess Pb in the films deposited on LaNiO3/Si was very low and the pinning effect was hardly observed. 相似文献
107.
108.
该文给出了Logistic分布纪录值序列部分和的中心极限定理;对于Pareto分布纪录值序列的部分和T_n,获得了lnT_n的中心极限定理.这一工作不仅具有概率论的极限理论方面的研究价值,而且在金融、保险等领域也具有相当重要的应用前景. 相似文献
109.
HL-2A װ��MW ������������ϵͳ��˿��Դ����������� 总被引:1,自引:0,他引:1
�ɼ̶���κ���죬��ţ��ܽ��� 《核聚变与等离子体物理》2006,39(3):227-231
The main circuit topology, control hardware and control sequence of the cathode filament power supply for the HL-2A neutral beam heating system was introduced. Feedback control simulation of main circuit of filament power supply is carried out through MATLAB simulation software. It is found that the ripple factor is about 1%when the current is about 1000A, and the ripple coefficient increases to 3% when the current drops to 200A. Without the AC filter reactor in series L1 and parallel harmonic filter LC in the low level control cabinet, the output current ripple coefficient becomes larger obviously. It shows that L1 and LC not only absorb harmonic current, but also filter the chopper waveform after AC voltage regulation to make the output waveform smoother. 相似文献
110.
基于EM算法和Laplace逼近, 本文给出了研究ZI (即含0较多的)纵向计数数据模型的影响分析方法. 为了识别含0较多的分组计数数据中的强影响点, 本文将ZI纵向数据模型中取值为0的数据赋予一定的权重; 而把随机效应看作缺失数据; 在此基础上引入EM算法, 从而应用完全数据对数似然函数的条件期望以及相应的$Q$距离函数进行影响分析; 并进一步应用Laplace逼近方法简化EM算法中的积分计算. 在此基础上, 基于数据删除模型和局部影响分析方法导出了适用于ZI纵向计数数据模型的诊断统计量. 本文也通过实际计数数据的例子验证了诊断统计量的有效性. 相似文献