全文获取类型
收费全文 | 158篇 |
免费 | 7篇 |
专业分类
化学 | 140篇 |
力学 | 1篇 |
数学 | 3篇 |
物理学 | 21篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 1篇 |
2016年 | 3篇 |
2015年 | 7篇 |
2014年 | 2篇 |
2013年 | 9篇 |
2012年 | 13篇 |
2011年 | 7篇 |
2010年 | 9篇 |
2009年 | 6篇 |
2008年 | 16篇 |
2007年 | 11篇 |
2006年 | 10篇 |
2005年 | 8篇 |
2004年 | 10篇 |
2003年 | 9篇 |
2002年 | 3篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 5篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有165条查询结果,搜索用时 609 毫秒
51.
Shigeru Arai Keiji Nakayama Yukari Suzuki Kei-ichiro Hatano Takayuki Shioiri 《Tetrahedron letters》1998,39(52):2459-9742
Treatment of cyclic or acyclic -haloenones with various carbon nucleophiles involving active methylene functions afforded the corresponding dihydrofurans in a stereoselective manner with good to high yields. This reaction system can provide a general and practical methodology for the construction of dihydrofuran rings. 相似文献
52.
Swelling behaviors of poly(vinyl alcohol) (PVA) gel were investigated in solutions of salts containing certain divalent ions, namely, alkaline-earth-metal halides and sulfates of alkali-metals, alkaline-earth-metals, and transition metals. The gel deswelled in the solutions of the alkaline-earth-metal chlorides but swelled in those of the bromides. However, the cation specificities of the swelling for both of the halides were roughly the same: the degrees of swelling are Sr2+2+2+. The gel deswelled for all sulfate solutions with specificities for alkali-metal and alkaline-earth-metal cations: the swelling degrees are K+;Na+2++. There was no order for transition metals. 相似文献
53.
Feng Gao Huijuan Zhao Yukari Tanikawa Kazhuhiro Homma Yukio Yamada 《Optical and Quantum Electronics》2005,37(13-15):1287-1304
Our recent diffuse optical tomography experiments on human lower legs and forearms are presented using the time-resolved measuring system and image reconstruction algorithm based on the modified generalized pulse spectrum technique. It was shown that the spatial resolution and quantitativeness of the resultant images, was rather poor, and the interior blood vessels invisible in the absorption images. To clarify this issue, the influences of target contrast and size on the image reconstruction were investigated with simulated data. We have found that the quantitativeness of the reconstructed optical properties was prone to be spoiled by the small size ratio and high contrast of the interior targets to the background, and the incompleteness of information embedded in the featured data-types, evidently answers for the degradation of the image quality. It was shown in a further simulative investigation that the image quality could be substantially improved by making full use of the time-resolved data. 相似文献
54.
Chemical forms of arsenic were examined in six tissues (gill, mid-gut gland, siphon, foot, mantle and adductor muscle) of the clam Meretrix lusoria. The gill was found to contain higher levels of arsenic than the other tissues. Regardless of the nature of the tissues, the presence of arsenobetaine was established by HPLC0ICP; it was a minor arsenic compound in gill but a major one in the other tissues. The major arsenic compound in gill, which was more cationic than arsenobetaine, was obtained in a relatively pure state by ion-exchange chromatography, gel filtration and HPLC. It was positive to the Dragendorff reagent and iodine vapor but negative to ninhydrin reagent. Its 1HNMR spectrum exhibited only one signal at δ 1.7 (singlet) and its FAB mass spectrum gave a base peak at m/e 135 [(CH3)4As+] and two significant peaks at m/e 120 [(CH3)3As] and 106 [(CH3)2AsH]. These results suggested that the major arsenic compound in gill exists as a tetramethylarsonium salt (CH3)4As+ · X?. The tetramethylarsonium salt was also found as a minor component in the tissues other than the gill. 相似文献
55.
Takeshi Inoue Takeshi Furukawa Akihiro Yoshimi Tsubasa Nanao Masatoshi Chikamori Kunifumi Suzuki Hironori Hayashi Hirokazu Miyatake Yuichi Ichikawa Masato Tsuchiya Naoto Hatakeyama Sota Kagami Makoto Uchida Hideki Ueno Yukari Matsuo Takeshi Fukuyama Koichiro Asahi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2016,70(6):129
56.
Yamano Y Fujita Y Mizuguchi Y Nakagawa K Okano T Ito M Wada A 《Chemical & pharmaceutical bulletin》2007,55(9):1365-1370
An improved synthesis of gamma-hydroxybutenolides 1a-d was achieved via crossed aldol condensation between aldehydes 2a-d and the protected gamma-hydroxy-beta-methylbutenolides 3 or 4 using the bulky Lewis acid, aluminum tris(2,6-diphenylphenoxide) (ATPH). Using this same methodology, the gamma-hydroxybutenolides 17a-d having various heteroaromatic rings were synthesized and their anti-tumor activities were evaluated. 相似文献
57.
In capillary electrochromatography (CEC), magnetic particles (MPs) were packed in a fused silica capillary by using the magnetic field to be retained without frits. For a chiral CEC separation, avidin was immobilized onto the surface of the MPs (AVI-MPs) as a stationary phase by using the physical adsorption technique. The injected AVI-MPs into the capillary were stably captured with the magnet (surface magnetic flux density, 250 mT) under the separation voltage of 10 kV (190 V/cm). By employing the fritless AVI-MPs packed capillary, the chiral separation of ketoprofen was successfully attained with the packing length of only 5 cm. Effects of the modification condition of avidin, pH of background solution, and the packing length on the enantioseparation were also investigated. Under the optimal condition, furthermore, the repeatability for the retention time of ketoprofen was better than 1.5% in the relative standard deviation and the capillary-to-capillary reproducibility was also acceptable in the prepared fritless capillaries. 相似文献
58.
Hirata Y Whitehurst E Cullings E 《The Journal of the Acoustical Society of America》2007,121(6):3837-3845
Native English speakers were trained to identify Japanese vowel length in three types of training differing in sentential speaking rate: slow-only, fast-only, and slow-fast. Following Pisoni and Lively's high phonetic variability hypothesis [Pisoni, D. B., and Lively, S. E., Speech Perception and Linguistic Experience, 433-459 (1995)], higher stimulus variability by means of training with two rates was hypothesized to aid learners in adapting to speech rate variation more effectively than training with only one rate. Trained participants identified the length of the second vowel of disyllables, short or long, embedded in a sentence of the respective rate, and received immediate feedback. The three trained groups' abilities before and after training were examined with tests containing sentences of slow, normal, and fast rates, and were compared with those of a control that was not trained. A robust effect of slow-fast training, a marginal effect of slow-only training, but no significant effect of fast-only training were found in the overall test scores. Slow-fast and slow-only training showed small advantages over fast-only training on the fast-rate test scores, while effects for all three training types were found on the slow- and normal-rate test scores. The degree to which the results support the high phonetic variability hypothesis is discussed. 相似文献
59.
Kitaoka M Tsuruda Y Tanaka Y Goto M Mitsumori M Hayashi K Hiraishi Y Miyawaki K Noji S Kamiya N 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(19):5387-5392
A new synthetic strategy for DNA-enzyme conjugates with a novel architecture was explored using a natural cross-linking catalyst, microbial transglutaminase (MTG). A glutamine-donor substrate peptide of MTG was introduced at the 5-position on the pyrimidine of deoxyuridine triphosphate to prepare a DNA strand with multiple glutamine-donor sites by polymerase chain reaction (PCR). A substrate peptide that contained an MTG-reactive lysine residue was fused to the N terminus of a thermostable alkaline phoshatase from Pyrococcus furiosus (PfuAP) by genetic engineering. By combining enzymatically the substrate moieties of MTG introduced to the DNA template and the recombinant enzyme, a DNA-(enzyme)(n) conjugate with 1:n stoichiometry was successfully obtained. The enzyme/DNA ratio of the conjugate increased as the benzyloxycarbonyl-L-glutaminylglycine (Z-QG) moiety increased in the DNA template. The potential utility of the new conjugate decorated with signaling enzymes was validated in a dot blot hybridization assay. The DNA-(enzyme)(n) probe could clearly detect 10(4) copies of the target nucleic acid with the complementary sequence under harsh hybridization conditions, thereby enabling a simple detection procedure without cumbersome bound/free processes associated with a conventional hapten-antibody reaction-based DNA-detection system. 相似文献
60.
Iwao Okamoto Yusuke Takahashi Mika Sawamura Mio Matsumura Hyuma Masu Kosuke Katagiri Isao Azumaya Masanori Nishino Yukari Kohama Nobuyoshi Morita Osamu Tamura Hiroyuki Kagechika Aya Tanatani 《Tetrahedron》2012,68(27-28):5346-5355
Redox-induced conformational alteration of N-aryl-N-phenylamides, in which the N-aryl group consists of a hydroquinone–p-quinone system, was examined. The reduced form bearing a dihydroxyphenyl or dimethoxyphenyl group exists mainly in the E-form, whereas the oxidized form bearing a N-benzoquinone moiety takes the Z-form both in the crystal and in solution. This redox-induced conformational alteration is associated with a marked change in optical properties. This system appears to have suitable properties for use in external redox stimulus-responsive functional switching. 相似文献