全文获取类型
收费全文 | 291篇 |
免费 | 89篇 |
国内免费 | 14篇 |
专业分类
化学 | 35篇 |
晶体学 | 41篇 |
力学 | 2篇 |
综合类 | 2篇 |
数学 | 1篇 |
物理学 | 186篇 |
无线电 | 127篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 11篇 |
2021年 | 24篇 |
2020年 | 6篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 8篇 |
2016年 | 17篇 |
2015年 | 17篇 |
2014年 | 21篇 |
2013年 | 49篇 |
2012年 | 22篇 |
2011年 | 18篇 |
2010年 | 10篇 |
2009年 | 14篇 |
2008年 | 15篇 |
2007年 | 14篇 |
2006年 | 19篇 |
2005年 | 14篇 |
2004年 | 16篇 |
2003年 | 7篇 |
2002年 | 7篇 |
2001年 | 7篇 |
2000年 | 5篇 |
1999年 | 11篇 |
1998年 | 11篇 |
1997年 | 5篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有394条查询结果,搜索用时 671 毫秒
1.
2.
3.
4.
We have initiated a search for a new type of nuclear matter, theη-mesic nucleus, using beams from the multi-GeV hadron facility, COSY at Juelich, Germany. A large acceptance scintillator detector, ENSTAR has been designed and built at BARC, Mumbai and fully assembled and tested at COSY. A test run for calibration and evaluation has been completed. In this contribution we present the design and technical details of the ENSTAR detector and how it will be used to detect protons and pions (the decay products ofη-mesic bound state). The detector is made of plastic scintillators arranged in three concentric cylindrical layers. The readout of the detectors is by means of optical fibres. The layers are used to generate ΔE –E spectra for particle identification and total energy information of stopped particles. The granularity of the detector allows for position (θ and ?ø determination making the event reconstruction kinematically complete 相似文献
5.
地方时与区时在电离层研究中的差异 总被引:2,自引:0,他引:2
本文指出混淆地时与区时两个时间概念在电离层研究中带来的差异的严重性,建议使用地方与区时这两个名词,而抛弃“本地时”和“当地时”等容易引起混淆的名词。 相似文献
6.
A delayed coincidence method, time-interval analysis (TIA), has been applied to successive – decay events on the millisecond time-scale. Such decay events are part of the 220Rn216Po (T1/2 145 ms) (Th-series) and 219Rn215Po (T1/2 1.78 ms) (Ac-series). By using TIA in addition to measurement of 226Ra (U-series) from -spectrometry by liquid scintillation counting (LSC), two natural decay series could be identified and separated. The TIA detection efficiency was improved by using the pulse-shape discrimination technique (PSD) to reject -pulses, by solvent extraction of Ra combined with simple chemical separation, and by purging the scintillation solution with dry N2 gas. The U- and Th-series together with the Ac-series were determined, respectively, from alpha spectra and TIA carried out immediately after Ra-extraction. Using the 221Fr217At (T1/2 32.3 ms) decay process as a tracer, overall yields were estimated from application of TIA to the 225Ra (Np-decay series) at the time of maximum growth. The present method has proven useful for simultaneous determination of three radioactive decay series in environmental samples. 相似文献
7.
Summary A new, highly sensitive and selective gas chromatography method, using radiochemical detection (GC-DR) was developed for the
selective determination of3H-labelled deramciclane and its N-desmethyl metabolite in dog plasma. Inter-day accuracy and precision, as well as system
suitability of the GC-RD method was investigated during the method validation. The calibration curve was proved to be linear
(r=0.9986) in a wide concentration range (13–1000 ngeqv mL−1)
The lower limit of quantitation (LLOQ) was 13.7 ngeqv mL−1, and the limit of the detection (LOD) was 1 ngeqv mL−1.
Using this new GC-RD method, plasma levels of3H-labelled deramciclane and its metabolite were determined in dogs, after the administration of a single 10 mg kg−1 oral dose. Pharmacokinetic curves and the calculated pharmacokinetic parameters were compared to those obtained using a previously
elaborated gas chromatography-nitrogen selective detection method (GC-NPD) and to those obtained by measuring the plasma level
of total radioactivity (liquid scintillation counting, LSC). Pharmacokinetic curves and the calculated pharmacokinetic parameters
obtained with the two different gas chromatography detection methods (NPD and RD) showed good correlation. Comparison of these
results to those acquired by total radioactivity measurement demonstrated that deramciclane was intensively metabolised. Moreover,
the biological half-life (t
1
2/β
) of the unknown metabolites proved to be more than a magnitude longer than the half-life of the parent compound or that of
N-desmethyl metabolite.
Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997. 相似文献
8.
Shihai You Tingting Zhu Yumin Wang Zeng-Kui Zhu Zhongyuan Li Jianbo Wu Panpan Yu Lina Li Chengmin Ji Yaxing Wang Shuao Wang Junhua Luo 《Advanced functional materials》2023,33(9):2210481
The exceptional photophysical properties of 3D organic–inorganic lead halide hybrids (OILHs) endow their significant potential for usage in optoelectronics, which has sparked intense research on novel 3D OILHs and associated applications. However, constructing new 3D OILHs based on large organic cations suffers from tough challenges due to the limitation of the Goldschmidt tolerance factor rule, let alone further explorations of their practical applications. Herein, a brand-new 3D lead chloride hybrid, (1MPZ)Pb4Cl10·H2O ( 1 , 1MPZ = 1-methylpiperazine) is reported, featuring a dense 3D lead chloride framework made of the corner-, edge-, and face-shared lead chloride polyhedra. 1 presents a broadband white light emission with a large Stokes shift and a nanosecond photoluminescence lifetime, which originates from radiative recombination of self-trapped excitons (STEs) induced by the highly distorted structure. Such a reabsorption-free and fast-decayed STEs emission coupling with the dense 3D architecture further enables 1 with effective X-ray scintillation with good sensitivity. Impressively, 1 also shows superior environmental and radiation stability. This study provides a new 3D OILH with appealing luminescence, not only expanding the 3D OILH family but also inspiring the exploitation of their optoelectronic applications. 相似文献
9.
The nature and relative contributions (RCs) of various radiative recombination processes to the photoluminescence (PL) spectra for bulk nanostructured Pb0.30Cd0.70I2 solid solutions have been established at different temperatures. The analysis indicates that the PL is caused by free, bound and self-trapped excitons as well as by donor-acceptor pairs emission with the participation of shallow and deep acceptor centers. It was shown that X-ray luminescence (XRL) spectra are also determined by these recombination processes. However, their RC and the temperature evolution are considerably different. Besides, XRL spectra contain an intense long-wavelength band associated with the emission of many LO-phonons. It was shown that the deep luminescence surface states, associated with the self-trapped excitons and deep intrinsic defects, mainly determine the intensity of XRL spectra both at 80 K and room temperature. The results obtained open the way to the optimization of the scintillator properties of the investigated materials. 相似文献
10.
K. Irmer 《Isotopes in environmental and health studies》2013,49(10):417-418
Bei der kontinuierlichen Durchstrahlungsprüfung von Werkstücken werden überwiegend Meßeinrichtungen, bestehend aus 60Co-Strahlungsquelle, Szintillationsdetektor und schreibendem Meßgerät, verwendet 1. 相似文献