全文获取类型
收费全文 | 96篇 |
免费 | 0篇 |
专业分类
化学 | 39篇 |
力学 | 2篇 |
数学 | 29篇 |
物理学 | 26篇 |
出版年
2020年 | 1篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2014年 | 2篇 |
2013年 | 11篇 |
2012年 | 3篇 |
2011年 | 4篇 |
2010年 | 1篇 |
2009年 | 3篇 |
2008年 | 1篇 |
2007年 | 2篇 |
2006年 | 3篇 |
2005年 | 2篇 |
2004年 | 4篇 |
2003年 | 2篇 |
2002年 | 5篇 |
2001年 | 3篇 |
1999年 | 4篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1980年 | 3篇 |
排序方式: 共有96条查询结果,搜索用时 421 毫秒
61.
Ozonolysis of an A.B-ring functionalized derivative of phytosterols found in the deodorizer distillate of canola oil gave the desired aldehyde 5, Canola oil thus provides a readily available and inexpensive source of a key intermediate 5 which is frequently employed in steroidal syntheses. 相似文献
62.
63.
This article explores the phenomenon of mathematical understanding, and offers a response to the question raised by Martin (2001) at the Annual Meeting of the Psychology of Mathematics Education Group (North American Chapter) about the possibility for and nature of collective mathematical understanding. In referring to collective mathematical understanding, we point to the kinds of learning and understanding we may see occurring when a group of learners work together on a piece of mathematics. We characterize the growth of collective mathematical understanding as a creative and emergent improvisational process and illustrate how this can be observed in action. In doing this, we demonstrate how a collective perspective on mathematical understanding can more fully explain its growth. We also discuss how considering the growth of mathematical understanding as a collective process has implications for classroom practice and in particular for the setting of mathematical tasks. 相似文献
64.
ANTIVIRAL ACTIVITY OF THE PHOTOACTIVE PLANT PIGMENT HYPERICIN 总被引:6,自引:0,他引:6
The polycyclic compound hypericin, a known photodynamic agent, was investigated for antiviral activity in the presence and absence of light. The three viruses tested: murine cytomegalovirus; Sindbis virus; and human immunodeficiency virus type 1, were all susceptible to hypericin; but these antiviral activities were considerably enhanced, in a dose-dependent manner, by exposure to light. 相似文献
65.
Simple calibration of a phase-based 3D imaging system based on uneven fringe projection 总被引:1,自引:0,他引:1
Phase-based fringe projection metrology systems have been widely used to obtain the shape of 3D objects. One vital step is calibration, which defines the relationship between the phase and depth data. Existing calibration methods are complicated because of the dependence of the relationship on the pixel position. In this Letter, a simple calibration procedure is introduced based on an uneven fringe projection technique, in which the relationship between phase and depth becomes independent of the pixel position and can be represented by a single polynomial function for all pixels. Therefore, given a set of discrete points with a known phase and depth in the measuring volume, the coefficient set of the polynomial function can be determined. A white plate having discrete markers with known separation is used to calibrate the 3D imaging system. Experimental results demonstrate that the proposed calibration method is simple to apply and can build up an accurate relationship between phase and depth data. 相似文献
66.
Lemeer S Kunold E Klaeger S Raabe M Towers MW Claudes E Arrey TN Strupat K Urlaub H Kuster B 《Analytical and bioanalytical chemistry》2012,402(1):249-260
Owing to its broad biological significance, the large-scale analysis of protein phosphorylation is more and more getting into
the focus of proteomic research. Thousands of phosphopeptides can nowadays be identified using state-of-the-art tandem mass
spectrometers in conjunction with sequence database searching, but localizing the phosphate group to a particular amino acid
in the peptide sequence is often still difficult. Using 180 individually synthesized phosphopeptides with precisely known
phosphorylation sites (p-sites), we have assessed the merits of the Mascot Delta Score (MD score) for the assignment of phosphorylation
sites from tandem mass spectra (MS/MS) generated on four different matrix-assisted laser desorption ionization (MALDI) mass
spectrometers including tandem time-of-flight (TOF/TOF), quadrupole time-of-flight, and ion trap mass analyzers. The results
show that phosphorylation site identification is generally possible with false localization rates of about 10%. However, a
comparison to previous work also revealed that phosphorylation site determination by MALDI MS/MS is less accurate than by
ESI-MS/MS particularly if several and/or adjacent possible phosphorylation acceptor sites exist in a peptide sequence. We
are making the tandem MS spectra and phosphopeptide collection available to the community so that scientists may adapt the
MD scores reported here to their analytical environment and so that informatics developers may integrate the MD score into
proteomic data analysis pipelines. 相似文献
67.
Matthew Towers 《Algebras and Representation Theory》2013,16(1):251-274
We show that the ordinary cohomology functor $\Lambda \mapsto {\operatorname{Ext}} ^* _\Lambda (k,k)$ from the category of augmented k-algebras to itself exchanges coproducts and products, then that Hochschild cohomology is close to sending coproducts to products if the factors are self-injective. We identify the multiplicative structure of the Hochschild cohomology of a product, modulo a certain ideal, in terms of the cohomology of the factors. 相似文献
68.
We present a fiber interferometer for the simultaneous measurement of phase at multiple wavelengths from a single broadband femtosecond laser. Narrow-bandwidth fiber Bragg gratings isolate a particular frequency from the broad-bandwidth laser pulse produced. The multiwavelength phase data permit the unambiguous measurement range to be significantly increased compared with the wavelengths used in the interferometer. Preliminary experimental results are presented for a two-frequency sensor with an absolute range of 0.13 mm and associated dynamic range of 43,000:1. 相似文献
69.
J. B. Hudson E. A. Graham G. C. Chan G. H. N. Towers 《Photochemistry and photobiology》1985,42(5):523-528
Abstract— Five photoactive furanyl compounds were investigated for their activities against viruses. The two furanocoumarins used were 8-methoxypsoralen (8-MOP) and angelicin; two furanochromones, visnagin and khellin, and the furanoquinoline, dictamnine, were also used. The DNA-containing herpes virus murine cytomegalovirus (MCMV) and the RNA-containing togavirus, Sindbis virus, were the target viruses. All five compounds inactivated both viruses in the presence of UVA, although Sindbis virus was much less sensitive. The relative order of antiviral potency was 8-MOP > dictamnine > visnagin > angelicin > khellin. Dictamnine however was slightly more effective than 8-MOP against Sindbis virus. None of the treatments affected the structural integrity of MCMV, nor did they interfere with the normal transit of the virus into host cells or the localisation of the viral genome in the cell nucleus. Some early viral gene functions were expressed but the viruses did not replicate. 相似文献
70.
F. J. Garcia E. Yamamoto Z. Abramowski K. Downum G. H. N. Towers 《Photochemistry and photobiology》1984,39(4):521-524
Abstract— Two analogues of α-terthienyl, namely 2, 5di(2'-thienyl) selenophene and 2, 5di(2'-thienyl) furan have been prepared and their phototoxicities toward several microorganisms have been compared. Dose response studies with Escherichia coli indicate that α-terthienyl is more active than these analogues. α-Terthienyl was shown to be the most effective of the three compounds in the photoinactivation of yeast alcohol dehydrogenase. Diagnostic tests showed the participation of singlet oxygen in the photosensitization to different extents by these three thiophenes. 相似文献