全文获取类型
收费全文 | 703篇 |
免费 | 13篇 |
国内免费 | 15篇 |
专业分类
化学 | 474篇 |
晶体学 | 18篇 |
力学 | 5篇 |
数学 | 28篇 |
物理学 | 206篇 |
出版年
2022年 | 4篇 |
2021年 | 9篇 |
2019年 | 5篇 |
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 9篇 |
2015年 | 9篇 |
2014年 | 7篇 |
2013年 | 28篇 |
2012年 | 30篇 |
2011年 | 28篇 |
2010年 | 20篇 |
2009年 | 20篇 |
2008年 | 36篇 |
2007年 | 30篇 |
2006年 | 32篇 |
2005年 | 25篇 |
2004年 | 34篇 |
2003年 | 38篇 |
2002年 | 29篇 |
2001年 | 30篇 |
2000年 | 26篇 |
1999年 | 14篇 |
1998年 | 9篇 |
1997年 | 8篇 |
1996年 | 14篇 |
1995年 | 4篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 9篇 |
1991年 | 10篇 |
1990年 | 12篇 |
1989年 | 8篇 |
1987年 | 12篇 |
1986年 | 11篇 |
1985年 | 21篇 |
1984年 | 17篇 |
1983年 | 8篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1978年 | 10篇 |
1977年 | 12篇 |
1976年 | 5篇 |
1974年 | 7篇 |
1973年 | 5篇 |
1972年 | 9篇 |
1970年 | 3篇 |
1969年 | 3篇 |
1967年 | 5篇 |
排序方式: 共有731条查询结果,搜索用时 250 毫秒
151.
Masahiro Aoyama Tomokatsu Hayakawa Sawao Honda Yuji Iwamoto 《Journal of luminescence》2012,132(10):2603-2607
In this research, zeolite-derived aluminosilicate phosphors were synthesized through the ion exchange route. Red light-emitting property of Eu3+-doped aluminosilicate phosphors were discussed from a view point of the Eu content, heat-treatment condition and the oxidation state of Eu ions. The crystalline phase of the host aluminosilicates could be successfully controlled as designed based on the published NaAlO2–SiO2 binary phase diagram. Orange-red emission peaks derived from the 5D0→7Fj (j=0, 1, 2, 3, 4) transition of Eu3+ were observed around 590–700 nm, and 4f65d→4f7 transition of Eu2+ was observed at around 400–500 nm. The relative intensity I(5D0→7F2) of the dominant emission peak at 612 nm increased consistently with the Eu content. The results of the XANES spectroscopy analysis revealed that Eu2+ ion in the 1400 °C as heat-treated host aluminosilicate were successfully converted to Eu3+ by the additional annealing at 1100 °C. The Eu contents and heat-treatment conditions were determined to exhibit the best performance as a red phosphor, which were 10 wt% and 1500 °C, respectively 相似文献
152.
Planar-chiral palladium complexes {[[N,N'-[1,4-butanediylbis(oxy-7,1-naphthalenediyl)]bis(2-pyridinecarboxamidato)](2-)-κN(1),κN(1)',κN(2),κN(2)']palladium (PdL(4)) and [[2,2'-[1,4-butanediylbis[[(oxy-7,1-naphthalenediyl)imino]methyl]]dipyrrolato](2-)-κN(1),κN(1)',κN(2),κN(2)']palladium (PdL(5))} were synthesized from achiral tetradentate ligands N,N'-[1,4-butanediylbis(oxy-7,1-naphthalenediyl)]bis(2-pyridinecarboxamide) (H(2)L(4)) and N,N'-bis[(1H-pyrrol-2-yl)methylidene]-7,7'-(1,4-butanediyldioxy)bis(1-naphthalenamine) (H(2)L(5)) bearing two dissymmetric bidentate units at both ends and a Pd(II) ion, respectively. The palladium complexes were crystallized in the monoclinic space group P2(1)/n with the unit cell parameters a = 16.5464(6) ?, b = 11.3534(4) ?, c = 17.6697(7) ?, β = 115.5300(10)°, and Z = 4 for PdL(4) and a = 17.2271(8) ?, b = 10.1016(5) ?, c = 17.9361(9) ?, β = 105.6310(10)°, and Z = 4 for PdL(5). The planar-chiral structures of PdL(4) and PdL(5) were confirmed by single-crystal X-ray analyses, resulting in the fact that the crystals were racemic mixtures. The racemic mixtures were successfully resolved by using chiral high-performance liquid-chromatography techniques. Racemizations of the complexes were found to be drastically dependent on the arrangement of the charged or uncharged metal-binding N atoms of the ligands. 相似文献
153.
The electric fields created by lightning discharges in a neutral atmosphere are calculated in the time representation. It
is shown that asymmetric strokes containing horizontal currents can generate pronounced pulsed electric fields. A high-power
quasistatic field can influence the middle atmosphere together with pulses. The motion of the current wave in a complex-geometry
stroke channel can lead to an increase in the number of emitted pulses. At the periphery of the lightning cell, upon the arrival
of the pulse, the electric field vector turns upward, to the stroke axis, and sideward. We also expect an increase in atmospheric
turbulence due to convection at the frontal part of the cloud. The emerging inhomogeneities of the atmospheric temperature
and density can facilitate the onset of plasma processes generated by the electric field of a strong thunderstorm. Since convection
and the focusing electric fields are concentrated at the periphery, their joint action can lead to the appearance of circular
and prolate luminous formations.
Institute of Radiophysics and Electronics of the National Academy of Sciences, Khar’kov, Ukraine; The University of Electro-Communications,
Tokyo, Japan. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 6, pp. 699–722, June, 1998. 相似文献
154.
张玉虎 M.Oshima T.Morikawa T.Hayakawa Y.Toh 周小红 何建军 刘忠 甘再国 T.Shizuma M.Koizumi A.Osa J.Katakura Y.Hatsukawa M.Matsuda N.Shinohara T.Ishii H.Kusakari M.Sugawara K.Furuno T.Komatsubara T.Une 温书贤 竺礼华 王治民 许甫荣 《中国物理 C》2003,(4)
利用重离子熔合蒸发反应和在束γ谱学实验方法研究了双奇核176,178Ir和182 Au的高自旋态结构 ,在这 3个双奇核中观测到了基于πi13 2 νi13 2 准粒子组态下的转动带 .以能级间隔系统学为判据 ,对184Au核中πi13 2 νi13 2 转动带能级自旋进行了指定 .指出176,178Ir和182 ,184Au 4个双奇核的πi13 2 νi13 2 转动带在低自旋区均出现旋称反转 .对πi13 2 νi13 2 转动带旋称反转现象进行了定性的讨论 .用推转壳模型对πh9 2 νi13 2 带和πi13 2 νi13 2 带能级结构进行了理论研究 ,发现当采用形变和对力自洽计算后 ,从理论上可以定性地解释两个半退耦带出现的旋称反转现象 相似文献
155.
156.
Atsushi Yamamoto Mio Kawai Mitsunori Sakamoto Shuji Kodama Kazuichi Hayakawa 《Analytical sciences》2008,24(3):361-364
A sensitive and variable-wavelength optical rotatory (OR) detector for high-performance liquid chromatography is presented. This design is entirely different from that of conventional OR detectors consisting of a crossed polarizer pair. By placing a polarizing prism and a retardation plate into a commercial circular dichroism (CD) detector, the OR signal was obtained. The Mueller matrix approach was used to prove the principle of the OR signal appearance. Sugars and 4-androstene-3,17-dione were chosen as test compounds. The limit of detection was below 0.5 microg of injected sucrose at 260 nm, which was superior to that obtained with a conventional OR detector. For 4-androstene-3,17-dione, which is CD active, and shows a large anomalous OR dispersion curve, our detector gave a large OR signal with approximately half the intensity of the CD signal at 340 nm. 相似文献
157.
S. Hayakawa N. Kabuki 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(1):163-173
Charge inversion mass spectrometry was used to produce the electronically
excited species CHn (n=3–5) from their corresponding positive ions by
neutralization with an alkali metal target, and then to subsequently detect
and mass-analyze the negative ions formed from the neutral fragments
produced from the dissociation of the excited neutrals. The trapezoidal
shape and the intensity of the peak associated with CH2- ions in
the charge inversion spectrum of CH3+ ions indicated that the
CH3 neutrals dissociated mainly into CH2 + H without a large
activation barrier. The most intense peak in the spectrum of CH4+
ions was that associated with CH2- ions, and this peak comprised a
combination of both trapezoidal and triangular shaped peaks. The trapezoidal
shaped peak was attributed to CH2- ions resulting from direct
dissociation of CH4 into CH2 + H2. The concurrent
dissociation of CH4 into CH3 + H was followed by the further
subsequent dissociation of the deformed CH3 fragments into CH2 +
H, and this was proposed to be the origin of the triangular shaped component
of the CH2- peak. In the spectrum of CH5+ ions, the
CH3- peak was much less intense than the CH2- peak,
which was proposed to be the result of the geometry of the CH3, formed
from the dissociation of CH5 into CH3 + H2,being
substantially distorted from the D3h symmetry, leading to its further
subsequent dissociation. 相似文献
158.
Kenji Hanabusa Xuanjing Ye Akio Kurose Hirofusa Shirai Tadao Hayakawa Nobumasa Hojo 《Journal of polymer science. Part A, Polymer chemistry》1989,27(12):4191-4204
Amphiphilic active 4-dodecanoyl-2-nitrophenyl esters of dipeptide containing β-alanine ( 1 – 5 ) were prepared and their polycondensation was studied in detail. The critical micelle concentrations of the active esters 1 – 5 were determined in water by the dye method and the apparent mean aggregation number of reversed micelles formed by model compound 6 was determined by the osmotic method. The results of polycondensation can be explained by assuming that aggregations such as micelle and reversed micelle play an important role in polycondensation. The obtained new poly(dipeptide)s were examined by IR, 1H NMR, x-ray diffraction, and circular dichroism spectra. 相似文献
159.
T. Hayakawa M. Oshima T. Toh T. Shizuma J. Katakura Y. Hatsukawa M. Matsuda H. Kusakari M. Sugawara 《中国科学G辑(英文版)》2004,47(5)
Nuclei with N and Z near magic number can be well described by the nuclear shell model. The 145Tb nucleus has a valence proton and a pair of neutron holes with respect to the doubly closed 146Gd nucleus. Therefore, it is expected that the excitations in 145Tb be dominated by single-particle configurations. A detailed measurement of the excitation scheme in 145Tb would give us an opportunity to examine the behavior of multi-particle excitations involving high angular momentum orbits and provi… 相似文献
160.