全文获取类型
收费全文 | 988篇 |
免费 | 20篇 |
国内免费 | 2篇 |
专业分类
化学 | 748篇 |
晶体学 | 11篇 |
力学 | 17篇 |
数学 | 18篇 |
物理学 | 216篇 |
出版年
2021年 | 4篇 |
2020年 | 8篇 |
2019年 | 10篇 |
2016年 | 14篇 |
2015年 | 18篇 |
2014年 | 20篇 |
2013年 | 37篇 |
2012年 | 41篇 |
2011年 | 55篇 |
2010年 | 24篇 |
2009年 | 27篇 |
2008年 | 60篇 |
2007年 | 38篇 |
2006年 | 44篇 |
2005年 | 39篇 |
2004年 | 37篇 |
2003年 | 36篇 |
2002年 | 30篇 |
2001年 | 28篇 |
2000年 | 17篇 |
1999年 | 10篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 11篇 |
1995年 | 6篇 |
1994年 | 11篇 |
1993年 | 17篇 |
1992年 | 16篇 |
1991年 | 21篇 |
1990年 | 12篇 |
1989年 | 13篇 |
1988年 | 19篇 |
1987年 | 27篇 |
1986年 | 13篇 |
1985年 | 25篇 |
1984年 | 19篇 |
1983年 | 11篇 |
1982年 | 25篇 |
1981年 | 20篇 |
1980年 | 15篇 |
1979年 | 16篇 |
1978年 | 9篇 |
1977年 | 16篇 |
1976年 | 6篇 |
1975年 | 9篇 |
1974年 | 12篇 |
1973年 | 7篇 |
1971年 | 5篇 |
1968年 | 5篇 |
1967年 | 5篇 |
排序方式: 共有1010条查询结果,搜索用时 15 毫秒
31.
P. K. Kuroda I. O. Essien Deig-nevy Sandoval 《Journal of Radioanalytical and Nuclear Chemistry》1984,84(1):23-32
A marked increase in the concentration of238U in rain was observed at Fayetteville (36 °N, 94 °W), Arkansas, after the 18 May 1980 eruption of Mount St. Helens. The fallout of natural uranium observed during the summer months of 1980 can be attributed to the 18 May 1980 events, which ejected an amount of ash material on the order of 4 km3 or about 8·1015 grams into the atmosphere.234U and235U were found to be highly enriched relative to238U in several rain samples collected at Fayetteville, Arkansas, prior to the volcanic eruption. The anomalous uranium seems to have originated from the Soviet satellite Cosmos-954, which fell over Canada, on 24 January 1978. The effect of the 25th Chinese nuclear test, which occurred on 16 October 1980, on the concentrations of uranium isotopes in rain appears to have been insignificant. 相似文献
32.
P. K. Kuroda T. Barbod S. N. Bakhtiar 《Journal of Radioanalytical and Nuclear Chemistry》1987,111(1):137-146
Marked variations in the ratios of228Th/232Th,230Th/232Th and238U/232Th ratios were observed in rain samples collected at Fayetteville (36°N, 94°W), Arkansas, during 1980 through 1983. These variations are attributed to the fallout from the 1980 and 1982 eruptions of Mount St. Helens and El Chichón volcanoes.This investigation was supported by the National Science Foundation under Grant ATM 84-07618. 相似文献
33.
Principles of the thorium-230 dating method were applied to the study of thorium and uranium isotopes in a series of rain samples collected at Fayetteville (36°N, 94°W), Arkansas, since 1980. The results indicate that the rainwater contains volcanic ash materials with a wide variety of ages, which were blown up onto the upper stratosphere from the 18 May 1980 eruption of Mount St. Helens and the 28 March 1982 eruption of E1 Chichón. These volcanic materials seem to have stayed airborne for a number of years and profoundly affected the global atmospheric inventories of thorium and uranium isotopes.This investigation was supported by the National Science Foundation under Grant ATM 84-07618. 相似文献
34.
A simple and sensitive method is described for the determination of biogenic indole compounds adsorbed on cellulose or alumina plates for thin-layer chromatography by room-temperature phosphorimetry. The optimum conditions were investigated for 5-hydroxyindole-3-acetic acid and indole-3-acetic acid. The compounds are spotted on the plates, which are then sprayed successively with sodium citrate or sodium acetate, and sodiu iodide solutions. The plates are dried completely under a stream of dry nitrogen, and immediately dipped in molten paraffin. The phosphorescence is stable for at least 3 h even in moist air. The limits of detection for nine biogenic indole compounds tested are between 2 and 300 pmol per sample spot. 相似文献
35.
36.
Time-resolved magneto photoluminescence in a diluted magnetic semiconductor Cd 0.9 Mn 0.1 Te has been carried out with varying exciton density from 10 14 to 10 19 cm m 3 . The reduction of the Zeeman shift and that of the magnetic polaron energy was found under strong photoexcitation. The spectral feature is interpreted in terms of the heating of the manganese spin subsystem. Polarization dependence of the spin heating is observed for the first time, revealing the contribution of the spin flip between excitons and magnetic ions to the heating process. 相似文献
37.
Shiro Okumura Rieko Kuroda Kuniyo Inouye 《Applied biochemistry and biotechnology》2014,174(2):494-505
We constructed a simple method for discrimination of single nucleotide polymorphism (SNP) with a surface plasmon resonance (SPR)-based sensor by determining the binding volume (BV) between a target SNP allele and a probe complementary to the target. In the method, a novel additive termed “blocker,” which is a short single-stranded DNA complementary to the target, was used. The blocker enhanced the BV of the target only to the full-match probe 10-fold or more, so the SNP alleles could be discriminated readily. The effect of the blocker concentration was also examined. The BV to only a full-match probe increased with increasing the blocker concentration and reached a plateau at the concentration of 300–500 nM. To assess the effectiveness of this method, the SNP associated with progressive rod-cone degeneration in dog was determined. The results of genotyping with the method were in good agreement with those obtained by direct sequencing. 相似文献
38.
39.
Abstract Three cases are described where chirality is recognized by achiral molecules, where chirality is induced into achiral compounds through interactions with chiral compounds, and lastly where induced chirality in the solid-state is utilized for an enantio-selective photoreaction. In the first instance, the thermodynamically and kinetically preferred diastereoisomer of an optically labile chromium complex depended on the nature of the achiral solvent. In the second case, for the first time 1,2-chloroethane was trapped and observed in a chiral near-eclipsed form and 1-chloropropane in the truly eclipsed form at room temperature in a 1:1 inclusion complex with an optically active host molecule. Finally, induced chirality in a prochiral compound in the solid-state was successfully employed in an enantio-selective photoreaction. In the two cases, solid-state CD provided valuable information. 相似文献
40.
Mitsunori Oda Takanori Kajioka Kazuya Ikeshima Ryuta Miyatake Shigeyasu Kuroda 《合成通讯》2013,43(13):2335-2343
The trimethylsilyl enol ether of l-acetylcyclohepta-1,3,5-triene was transformed to 3,3-dialkyl-1,2,3,8-tetrahydroazulen-1-one by a two-step sequence involving the Mukaiyama aldol reaction with ketones and the subsequent Nazarov cyclization. 相似文献