全文获取类型
收费全文 | 114篇 |
免费 | 2篇 |
专业分类
化学 | 69篇 |
力学 | 5篇 |
数学 | 28篇 |
物理学 | 14篇 |
出版年
2022年 | 2篇 |
2021年 | 1篇 |
2020年 | 4篇 |
2019年 | 2篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2014年 | 5篇 |
2013年 | 7篇 |
2012年 | 8篇 |
2011年 | 11篇 |
2010年 | 2篇 |
2009年 | 4篇 |
2008年 | 8篇 |
2007年 | 6篇 |
2006年 | 6篇 |
2005年 | 7篇 |
2004年 | 6篇 |
2003年 | 2篇 |
2002年 | 6篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1972年 | 3篇 |
1971年 | 1篇 |
排序方式: 共有116条查询结果,搜索用时 15 毫秒
31.
T Christensen J B Reitan G Kinn 《Journal of photochemistry and photobiology. B, Biology》1990,7(2-4):337-346
Clinical evidence indicates that phototherapy of hyperbilirubinaemia in newborn infants is a safe and efficient form of therapy. The short-term side effects are not serious and seem to be well controlled. There are few long-term follow-up studies of phototherapy-treated infants. Therefore one cannot completely exclude the possibility that side effects can be found in future studies. With this background we undertook the present study of possible genotoxic effects of phototherapy. Human cells of the established glioblastoma cell line TMG-1 were used. The cells were exposed to visible light in the presence of different concentrations of bilirubin or in the absence of bilirubin. DNA was unwound in alkaline solution and the induction of strand breaks was assayed by a method taking advantage of the fluorescence from the dye Hoechst 33258. Blue light induced single-strand breaks in the DNA of cells in culture in the absence of bilirubin. During irradiation of bilirubin solutions with blue and green phototherapy light, long-lived toxic photoproducts were formed under in vitro conditions. At high and clinically relevant bilirubin concentrations, the effects of blue and green light were relatively similar. At low concentrations, there was a smaller effect of green light as expected from the absorption spectrum of bilirubin. It remains to be seen whether the genotoxic effect observed in the present studies can occur in vivo. 相似文献
32.
A computer program for the calculation of the MP2 energy correction for a Kramers-restricted Dirac-Hartree-Fock four component
wave-function is presented. In the spirit of the integral-driven direct SCF scheme the algorithm has been developed as direct
MP2, calculating integrals as they are needed and avoiding the integral storage bottle-neck of conventional MP2. Relativistic
MP2 is applied to ground state (1Σ+) CuF, AgF and AuF.
Received: 15 December 1996 / Accepted: 2 April 1997 相似文献
33.
Human adenocarcinoma cells of the line WiDr and human leukemia T cells of the line Jurkat were incubated with 5-aminolevulinic acid and found to produce protoporphyrin IX (PpIX). They were able to transfer a fraction of the sensitizer to neighboring control cells. The transfer took place through direct membrane contact. Light exposures, inactivating about 20% of the sensitized cells, did not result in any acceleration of the transfer of PpIX. This is in contrast to what has been reported for PpIX in erythrocytes from patients with erythropoietic protoporphyria. In these cells light exposure transfers PpIX from the binding sites on hemoglobin to the plasma membrane and further to neighboring cells. The lack of light-induced transfer in the WiDr and Jurkat cells may be related to the binding sites of PpIX, supposedly membrane lipids and proteins embedded therein. Light exposure slightly increased the rate of loss of PpIX from WiDr cells. 相似文献
34.
DISTRIBUTION OF 5-AMINOLEVULINIC ACID-INDUCED PORPHYRINS IN NODULOULCERATIVE BASAL CELL CARCINOMA 总被引:6,自引:0,他引:6
Qian Peng Trond Warloe Johan Moan Helen Heyerdahl Harald B. Steen Jahn M. Nesland Karl-Erik Giercksky 《Photochemistry and photobiology》1995,62(5):906-913
Abstract— Microscopic fluorescence photometry incorporating a light-sensitive thermo-electrically cooled charge-coupled device (CCD) camera was employed to investigate the fluorescence distribution of 5-aminolevulinic acid (ALA)-induced porphyrins in 22 patients with a total number of 52 noduloul-cerative basal cell carcinomas (BCC) after topical ALA application with or without dimethylsulfoxide (DMSO)/ethylenediaminetetraacetic acid (EDTA) or after intravenous administration of ALA. Both localization patterns and amounts of ALA-induced porphyrins in the BCC were studied. The ALA-induced porphyrins were localized only in the superficial layers of the noduloulcerative BCC lesions after topical application of 20% ALA alone for 3 h. However, both the penetration of ALA into deep lesions and the production of the ALA-induced porphyrin fluorescence were increased after topical administration of 20% ALA and 20% DMSO/4% EDTA for 3 h. Prior treatment with 99% DMSO for 15 min further enhanced the ALA penetration into the BCC lesions after topical application of the ALA/DMSO/EDTA mixture and produced more ALA-induced porphyrins by a factor of about three compared with those treated with ALA alone. The penetration of ALA into the deep BCC lesions could also be increased by prolonging the time of topical application of 20% ALA/4% EDTA to 29–48 h (without DMSO). Intravenous injection of ALA led to a more homogeneous distribution of the ALA-derived porphyrins in the whole noduloulcerative BCC lesions. 相似文献
35.
Numerical Algorithms - This is an overview of examples and problems posed in the late 1600s up to the mid 1700s for the purpose of testing or explaining the two different implementations of the... 相似文献
36.
A short and concise synthesis of volicitin is presented. The synthesis is based on repeated chemoselective copper salt cross coupling reactions of alkynes and propargylic halides. 相似文献
37.
Dr. Jørn Eivind Tungen Dr. Lisa Gerstmann Prof. Dr. Anders Vik Roberta De Matteis Dr. Romain Alexandre Colas Prof. Dr. Jesmond Dalli Prof. Dr. Nan Chiang Prof. Dr. Charles Nicholas Serhan Prof. Dr. Markus Kalesse Prof. Dr. Trond Vidar Hansen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(6):1476-1480
New drugs that can resolve inflammation without immunosuppressive effects are at the medicinal chemistry frontier. Pro-resolving endogenously formed small molecules, that is, the resolvins, are excellent candidates displaying such bioactions. The first total synthesis of the specialized pro-resolving mediator RvD1n−3 DPA has been achieved using the underutilized sp3–sp3 Negishi cross coupling reaction and an alkyne hydrosilylation–protodesilylation protocol. Biological evaluations revealed that this novel mediator displays low nanomolar pro-resolving properties and potently activates the human DRV1/GPR32 receptor. As such, this endogenous natural product is a lead compound for the development of novel immunoresolvents. 相似文献
38.
Amalie F. Reinertsen Dr. Karoline G. Primdahl Roberta De Matteis Prof. Jesmond Dalli Prof. Trond V. Hansen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(7):e202103857
Herein we report the first total synthesis of RvD2n-3 DPA, an endogenously formed mediator biosynthesized from the omega-3 fatty acid n-3 docosapentaenoic acid. The key steps are the Midland Alpine borane reduction, Sonogashira cross-coupling reactions, and a Z-selective alkyne reduction protocol, yielding RvD2n-3 DPA methyl ester in 13 % yield over 12 steps (longest linear sequence). The physical property data (UV chromophore, chromatography and MS/MS fragmentation) of the synthetic lipid mediator matched those obtained from biologically produced material. Moreover, synthetic RvD2n-3 DPA also carried the potent biological activities of enhancing macrophage uptake of Staphylococcus aureus and zymosan A bioparticles. 相似文献
39.
Trond Peder Flaten 《Coordination chemistry reviews》2002,228(2):385-395
Tea (Camellia sinensis) is one of a few plants accumulating aluminium (Al), making tea a major source of dietary Al intake. This paper reviews published studies on the concentrations, speciation and bioavailability of Al in tea. With very few exceptions, the total concentration of Al in tea infusions is in the range 1-6 mg l−1. Probably more than 90% of this Al is bound to organic matter, but the nature of the organic species is unclear. Three studies using size exclusion chromatography provide evidence for Al species in the molecular mass (MM) range 4000-8500 Da, probably polyphenolic complexes. Two ultrafiltration studies indicate the presence of Al species with MMs above 10,000. The relative amount of the different organic Al species in tea infusions is unclear, and even the identity of any of these has not been demonstrated with certainty. A possible exception is Al trioxalate, which may be an important species based on evidence from two 27Al-NMR studies. It seems fairly well established that drinking tea leads to measurable, but moderate increases in urinary Al excretion. However, the Al present in tea does not seem to be much more bioavailable than that from other dietary sources. Even so, it cannot be dismissed that tea infusions may contain particularly bioavailable and neurotoxic compounds such as Al maltolate, but this is at present speculative. 相似文献
40.
SITES OF PHOTODYNAMICALLY INDUCED DNA REPAIR IN HUMAN CELLS 总被引:1,自引:0,他引:1
Abstract Human REH cells were incubated with the photosensitizers meso -tetra(4-sulfonatophenyl)porphyrin (TSPP=TPPS4 ) or meso -tetra(3-hydroxyphenyl)porphyrin (3-THPP). The relatively hydrophilic TSPP was partly found in the cytoplasm and partly in the nuclei, whereas the lipophilic 3-THPP was found apparently in membranes and not inside the nuclei. After illumination, sites of DNA repair were labeled by means of a monoclonal antibody against proliferating cell nuclear antigen (PCNA) bound in the nuclei. The amount of bound PCNA in non-S-phase cells was proportional to the light dose. The bound PCNA was homogeneously distributed in the nuclei 0.5 h after photodynamic treatment (PDT) with TSPP. In contrast, for cells given PDT with 3-THPP, the periphery of the nuclei was selectively labeled, indicating that the initial DNA damage was localized close to the sensitizer at the nuclear membrane. 相似文献