全文获取类型
收费全文 | 227篇 |
免费 | 45篇 |
国内免费 | 32篇 |
专业分类
化学 | 73篇 |
晶体学 | 2篇 |
力学 | 1篇 |
数学 | 1篇 |
物理学 | 227篇 |
出版年
2022年 | 2篇 |
2021年 | 5篇 |
2020年 | 2篇 |
2018年 | 4篇 |
2017年 | 7篇 |
2016年 | 14篇 |
2015年 | 7篇 |
2014年 | 11篇 |
2013年 | 15篇 |
2012年 | 18篇 |
2011年 | 19篇 |
2010年 | 7篇 |
2009年 | 31篇 |
2008年 | 24篇 |
2007年 | 15篇 |
2006年 | 23篇 |
2005年 | 16篇 |
2004年 | 12篇 |
2003年 | 14篇 |
2002年 | 9篇 |
2001年 | 9篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有304条查询结果,搜索用时 15 毫秒
41.
Photoionization mass spectrometry (PIMS) with vacuum ultraviolet (VUV) light source provides an efficient and fragmentation-free
method for the soft ionization of gaseous compounds, in order to facilitate an understanding of thermal decomposition behavior
and chemical composition of polymeric materials. The PIMS was applied to the evolved gas analysis (EGA) system equipped with
a skimmer interface which is constituted based upon a jet separator principle between a vacuum MS chamber and an atmospheric
sample chamber in a furnace. A photoionization source with a deuterium (D2) lamp was closely installed to the vacuum ionization chamber of a mass spectrometer to improve the ionization efficiency.
The thermal decomposition of typical polymers in inert gas atmosphere was investigated by the EGA-PIMS and the resulting PI
mass spectrum was characterized satisfactorily by only the parent ions with no contribution as a result of fragmentation during
the ionization. The results suggested that the EGA-PIMS was an especially powerful and desirable in situ thermal analysis
method for polymeric materials which evolve organic gases simultaneously and concurrently. The combination of EGA equipped
with skimmer interface with no change of evolved gaseous species and PIMS with fragmentation-free during the ionization is
described briefly, and the effective results are presented by comparing with EGA using conventional electron impact ionization
mass spectrometry. 相似文献
42.
As an Hg-free lamp using phosphor, the Bi3+ and Eu3+ co-doped Y2O2S phosphors were prepared and their luminescence properties under vacuum ultraviolet(VUV) excitation were investigated. The VUV photoluminescent intensity of Y2O2S:Eu3+ was weak, however, considerably stronger red emission at 626 nm with good color purity was observed in Y2O2S:Eu3+,Bi3+ systems. Investigation on the photoluminescence reveals that the strong VUV luminescence of Y2O2S:Eu3+,Bi3+ at 147 nm is mainly because the Bi3+ acts as a med... 相似文献
43.
WANG Zhi-long WANG Yu-hua ZHANG Jia-chi 《高等学校化学研究》2008,24(6):679-682
As an Hg-free lamp using phosphor, the Bi^3+ and EH^3+ co-doped Y2O2S phosphors were prepared and their luminescence properties under vacuum ultraviolet(VUV) excitation were investigated. The VUV photoluminescent intensity of Y2O2S:Eu^3+ was weak, however, considerably stronger red emission at 626 nm with good color purity was observed in Y2O2S:Eu^3+,Bi^3+ systems. Investigation on the photoluminescence reveals that the strong VUV luminescence of Y2O2S:Eu^3+,Bi^3+ at 147 nm is mainly because the Bi^3+ acts as a medium and effectively performs the energy transfer process: Y^3+-O^2-→Bi^3+→Eu^3+, while the intense emission band at 172 nm is attributed to the absorption of the characteristic ^1So-^1P1 transition of Bi^3+ and the direct energy transfer from Bi^3+ to Eu^3+. The Y2O2S:Eu^3+,Bi^3+ shows excellent VUV optical properties compared with the commercial (Y,Gd)BO3:Eu^3+. Thus, the Y2O2S:Eu^3+,Bi^3+ can be a potential red VUV-excited candidate applied in Hg-free lamps for backlight of liquid crystal display. 相似文献
44.
Design and performance of BOREAS,the beamline for resonant X‐ray absorption and scattering experiments at the ALBA synchrotron light source 下载免费PDF全文
Alessandro Barla Josep Nicolás Daniele Cocco Secundino Manuel Valvidares Javier Herrero-Martín Pierluigi Gargiani Jairo Moldes Claude Ruget Eric Pellegrin Salvador Ferrer 《Journal of synchrotron radiation》2016,23(6):1507-1517
The optical design of the BOREAS beamline operating at the ALBA synchrotron radiation facility is described. BOREAS is dedicated to resonant X‐ray absorption and scattering experiments using soft X‐rays, in an unusually extended photon energy range from 80 to above 4000 eV, and with full polarization control. Its optical scheme includes a fixed‐included‐angle, variable‐line‐spacing grating monochromator and a pair of refocusing mirrors, equipped with benders, in a Kirkpatrick–Baez arrangement. It is equipped with two end‐stations, one for X‐ray magnetic circular dichroism and the other for resonant magnetic scattering. The commissioning results show that the expected beamline performance is achieved both in terms of energy resolution and of photon flux at the sample position. 相似文献
45.
A method of luminescent UV and VUV spectroscopy was used to study the evolution of color centers in anion-defective alumina single crystals exposed to high doses of gamma-radiation. A sharp drop in the intensity of the emission bands and, therefore, the concentration of F+ and F-centers associated with the formation of aggregate F2-type centers was found. The aggregate centers create an additional emission band in the range of (1.8–2.8) eV. When the crystals are exposed to middle and high doses, the photoluminescence (PL) intensity is the highest in the emission band of F22+-centers, which indicates a high concentration of the aggregates from singly charged oxygen vacancies (of F+-centers). When PL of the crystals exposed to high doses is excited with synchrotron radiation of the VUV range, a wide emission band in the red and near infrared (NIR) regions is registered. The centers related presumably to impurity defects, their aggregates and clusters consisting of several oxygen vacancies are responsible for this emission band. 相似文献
46.
Takanori Kiyokura Fumihiko MAEDA Yoshio Watanabe Yoshinori Iketaki Koumei Nagai Yoshiaki Horikawa Masaharu Oshima Eiji Shigemasa Akira Yagishita 《Optical Review》2000,7(6):576-578
The throughput of a Schwarzschild objective using undulator synchrotron radiation was measured. Conventionally, the throughput was estimated from the squared reflectivity of one multilayer mirror and from the obstruction ratio. However, we evaluated the transmission ratio from the input and output photon flux using a precisely calibrated monochromatic beam from an undulator light source. It was found that the objective has a maximum throughput of 8.5% at a wavelength of 13.9 nm. 相似文献
47.
48.
Jim J. Lin Steve Harich Dennis W. Hwang Malcom S. Wu Yuan T. Lee Xueming Yang 《中国化学会会志》1999,46(3):435-444
Elimination of atomic hydrogen (H) and molecular hydrogen (H2) are important elementary chemical processes in photochemistry and combustion chemistry. Recently, unique and sensitive detection techniques for atomic and molecular hydrogen detection were developed in our laboratory. Using the advanced molecular beam methods, we have studied the photodissociation of a few typical hydrocarbons at 157 nm excitation, especially their atomic and molecular hydrogen elimination processes. In this report, we will briefly describe the results from photodissociation of propane, ethylene, propyne and methanol at 157 nm excitation. These molecules represent different classes of hydrocarbons such as alkane, alkene, alkyne and alcohol. Through careful studies on differently deuterated compounds, clear pictures of selective atomic and molecular hydrogen elimination processes can be constructed for all of the above compounds. These results will help us to understand the dissociation dynamics of the small hydrocarbon molecules. 相似文献
49.
Wenjia Wang Xiaoyun Yang Guangcai Chang Pengfei An Kewen Cha Yuhui Dong Peng Liu 《Journal of synchrotron radiation》2017,24(4):781-786
A method to calibrate and stabilize the incident X‐ray energy for anomalous diffraction data collection is provided and has been successfully used at the single‐crystal diffraction beamline 1W2B at the Beijing Synchrotron Radiation Facilities. Employing a feedback loop to control the movement of the double‐crystal monochromator, this new method enables the incident X‐ray energy to be kept within a 0.2 eV range at the inflection point of the absorption edge. 相似文献
50.
The surface of cyclo-olefin polymer (COP) was treated with vacuum ultraviolet (VUV) light at 172 nm wavelength to improve the wettability and adhesion properties. Through VUV treatment in air, the terminal groups of the COP surface were oxidized into oxygen functional groups, containing CO, CO, and COO components, making the COP surface hydrophilic. The extent of oxygenation was evaluated by XPS and FTIR-ATR spectra, and it was shown that the surface properties, hydrophilicity, and functionalization were dependent on both VUV irradiation distance and irradiation time, which have an effect on the concentration of oxygen functional groups. VUV-light treatment with a short irradiation distance was more effective in introducing oxygen functional groups. 相似文献