全文获取类型
收费全文 | 1237篇 |
免费 | 60篇 |
国内免费 | 4篇 |
专业分类
化学 | 916篇 |
晶体学 | 7篇 |
力学 | 27篇 |
数学 | 76篇 |
物理学 | 275篇 |
出版年
2023年 | 11篇 |
2022年 | 3篇 |
2021年 | 18篇 |
2020年 | 17篇 |
2019年 | 17篇 |
2018年 | 13篇 |
2017年 | 9篇 |
2016年 | 34篇 |
2015年 | 29篇 |
2014年 | 38篇 |
2013年 | 63篇 |
2012年 | 84篇 |
2011年 | 103篇 |
2010年 | 63篇 |
2009年 | 57篇 |
2008年 | 78篇 |
2007年 | 80篇 |
2006年 | 84篇 |
2005年 | 66篇 |
2004年 | 55篇 |
2003年 | 50篇 |
2002年 | 43篇 |
2001年 | 23篇 |
2000年 | 23篇 |
1999年 | 18篇 |
1998年 | 11篇 |
1997年 | 9篇 |
1996年 | 20篇 |
1995年 | 7篇 |
1994年 | 13篇 |
1993年 | 13篇 |
1992年 | 15篇 |
1991年 | 10篇 |
1990年 | 9篇 |
1989年 | 9篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 8篇 |
1985年 | 15篇 |
1984年 | 7篇 |
1983年 | 7篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1978年 | 3篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1974年 | 3篇 |
1973年 | 4篇 |
排序方式: 共有1301条查询结果,搜索用时 31 毫秒
151.
152.
Lue-Yung Chow Chiu Swadesh R. Samanta 《Journal of Quantitative Spectroscopy & Radiative Transfer》1981,25(3):253-264
Photoionization of H2(1Σg+) in a vibrational υ″ and rotational N″ state into H2+(2Σg+) in a vibrational υ′ and rotational N′ state is studied theoretically. The differential cross section, after summing over the final states, is expressed in the well-known simple form of . Parallel expressions are obtained for H2+ in a specific υ′ state (in terms of σ(υ′) and β(υ′)) and for H2+ in a rotational fine level υ′N′ (in terms of σ(υ′N′) and β(υ′N′)). Asymmetry parameters β, β(υ′) and β υ′N′), which are expressed in terms of Racah and Clebsch-Gordan coefficients and electronic transition moments, can be reduced approximately to 2 lineary polarized light and to -1 for unpolarized light. Using single-center electronic wave functions and including partial eaves l = 1, 3, and 5, σ(υ′) and β(υ′) are computed as a function of υ′ at 584 Å. The computed σ(υ′) divided by the Frank-Condon overlap, in agreement with experimental results, increases monotonically with υ′; σT and β are computed in the incident photon energy range of 600–4000 Å and the results compare favorably with previous calculations. 相似文献
153.
Shan-Tao?Lai Ying-Nan?Chiu Ricardo?LetelierEmail author 《Journal of mathematical chemistry》2005,37(1):1-16
Labarthes primitive L-patterns for the 3nj-symbols, where n=3,4,5,6,7, are reported. It is shown that, any L-patterns of the angular momentum recoupling coefficients can be expressed in terms of linear combinations of the primitive L-patterns and how the 3nj-symbols can be calculated from the expressions presented here.AMS subject classification: 81QShan-Tao Lai–Permanent Address for reprint requestYing-Nan ChiuAlso– Institute of Atomic and Molecular Sciences, Academia Sinica,Taipei, Taiwan, R.O.C. 相似文献
154.
155.
The published method for synthesis of the bridgehead lactam 6,6,7,7-tetramethyl-1-azabicyclo [2.2.2]octan-2-one yields polymers almost exclusively. Use of dilution techniques provides a 27% yield of this highly strained molecule. Base-induced methanolysis of this tetramethyl compound occurs exceedingly slowly compared to some other less crowded homologues. A buttressing effect is postulated to account for part of this effect. 相似文献
156.
M J Cwik G P Chiu J H Fischer E Chow-Tung B L Currie 《Journal of chromatography. A》1985,338(1):123-130
A high-performance liquid chromatographic procedure is described for the analysis of tolazoline in serum and urine. This assay procedure is suitable for the analysis of micro-samples (50 or 100 microliters serum and 100 microliters urine). Samples are extracted in a single step and injected into a reversed-phase high-performance liquid chromatography system for detection at 210 nm. The clinical applicability of this assay is demonstrated by the determination of tolazoline serum and urine concentrations in neonates. In addition, the presence of urine conjugates and the extent of serum protein binding were investigated. This assay procedure has the required sensitivity (0.1 microgram/ml), accuracy and precision for both routine monitoring and pharmacokinetic characterization of tolazoline in neonates and adults. 相似文献
157.
Semi-empirical molecular orbital conformational analyses of benzocyclooctatetraene, 1, dibenzo [a, c] cyclooetatetraene, 2 dibenzo [a, e] cyclooctatetraene, 3 tribenzo[a, c, e]-cyclooctatetraene, 4 tetrabenzo[a, c, e, g] cyclooetatetraene, 5 octafluorocyclooetatetraene, 6A, and cyclooctatetraene, 6B, have been done at the MNDO and MINDO/3 (excluding 4 and 5) levels of approximation. Comparison of these results with the X-ray structural data for 1 (as determined in the present work and the other benzannelated cyclooctatetraenes showed that, while MNDO is vastly superior to MINDO/3 both fail to account for the subtle effects of benzannelation on the conformation of the cyclooetatetraene ring. The experimental data indicate that the tub conformation of cyclooetatetraene is only slightly perturbed by the successive fusion of one and two non-adjacent benzene rings, but steric repulsion between adjacent annelated benzene rings, when present, predominates and gives rise to more folded configurations. Compound 1 crystallizes in space group P21/n with a = 1 1.856(2 B = 6.327(1 c = 12.470(3 Å, β = 110.03(2)°, and Z = 4. The structure has been solved by direct methods and refined to R = 0.049 for 1435 observed Mo-K diffractometer data. 相似文献
158.
Huang CH Chang YH Wang HW Cheng S Lee CY Chiu HT 《The journal of physical chemistry. B》2006,110(24):11818-11822
Porous carbon materials with pore sizes from 3 to 200 nm were synthesized by reacting hexafluorobenzene with Na liquid at 623 K. NaF crystals, a byproduct formed in the reaction, acted as nanotemplate to assist the pore formation. By employing hexafluorobenzene to react with Na incorporated within the channels (diameter 200 nm) of anodized aluminum oxide (AAO) membranes at 323-623 K, the carbon material can be fabricated into aligned porous nanotube arrays (ca. 250 nm in diameter, ca. 20 nm in wall thickness, ca. 0.06 mm in length, and ca. 3-90 nm in pore diameter). These materials were characterized by X-ray diffraction, scanning and transmission electron microscopy, X-ray energy dispersive spectroscopy, electron diffraction, thermal gravimetric analysis, and nitrogen physical adsorption experiments. 相似文献
159.
160.