全文获取类型
收费全文 | 445篇 |
免费 | 20篇 |
国内免费 | 3篇 |
专业分类
化学 | 339篇 |
力学 | 6篇 |
数学 | 76篇 |
物理学 | 47篇 |
出版年
2023年 | 5篇 |
2022年 | 1篇 |
2021年 | 21篇 |
2020年 | 8篇 |
2019年 | 11篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 25篇 |
2015年 | 20篇 |
2014年 | 10篇 |
2013年 | 32篇 |
2012年 | 39篇 |
2011年 | 35篇 |
2010年 | 23篇 |
2009年 | 17篇 |
2008年 | 28篇 |
2007年 | 24篇 |
2006年 | 20篇 |
2005年 | 28篇 |
2004年 | 25篇 |
2003年 | 23篇 |
2002年 | 21篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1995年 | 1篇 |
1993年 | 3篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1908年 | 1篇 |
排序方式: 共有468条查询结果,搜索用时 55 毫秒
461.
Elena Amico di Meane Margherita Plassa Francesca Rolle Michela Sega 《Accreditation and quality assurance》2009,14(11):607-611
Metrologically traceable measurements are needed, in environmental monitoring, to provide meaningful information on the pollution
level and the possibility to have suitable reference standards is crucial to this purpose to calibrate instruments. The Italian
National Institute of Metrological Research (I.N.Ri.M.), as a primary metrological institute, realizes and maintains primary
standards for the basic and derived units of the International System of Units (SI). In this framework and regarding gas analysis,
in the last few years I.N.Ri.M. has started a research line on the preparation of primary reference mixtures (PRMs) by the
gravimetric method that led to plan and build a facility for evacuating and filling cylinders and a device for high precision
weighing. In the present work the developments in such field at I.N.Ri.M. are reported to underline the relevance, in the
atmospheric pollutants monitoring, of performing accurate and reliable measurements and having reference standards fit for
the calibration of the analytical instrumentation. 相似文献
462.
Michela Sega Elena Amico di Meane Francesca Rolle 《Accreditation and quality assurance》2009,14(11):601-605
Metrology in chemistry has its own features, which distinguish it from classical metrology: due to the lack of primary methods
applicable in routine measurements, metrological traceability of measurement results can be achieved by using in a proper
way suitable certified reference materials (CRMs), which can assure a direct relation to a reference. This article deals with
the activity of the Italian National Institute of Metrological Research (Istituto Nazionale di Ricerca Metrologica—I.N.Ri.M.)
on the analysis of various polychlorinated biphenyls congeners in organic solution by means of gas-chromatography coupled
with mass spectrometry. The metrological traceability approach in the quantification step is pursued via calibration solutions
prepared by gravimetrically diluting a CRM. The uncertainty for the calibration solutions was evaluated taking into account
all the relevant contributions. 相似文献
463.
Juliette Moreau Dr. Umberto Giovanella Dr. Jean‐Philippe Bombenger Dr. William Porzio Dr. Varun Vohra Laura Spadacini Dr. Giuseppe Di Silvestro Prof. Luisa Barba Dr. Gianmichele Arrighetti Dr. Silvia Destri Dr. Mariacecilia Pasini Dr. Michele Saba Dr. Fancesco Quochi Dr. Andrea Mura Prof. Giovanni Bongiovanni Prof. Mauro Fiorini Dr. Michela Uslenghi Dr. Chiara Botta Dr. 《Chemphyschem》2009,10(4):647-653
All‐organic nanostructured host–guest materials (see picture) show enhanced, tunable fluorescence due to a high concentration of dyes with controlled spatial and geometrical organization that allows controlled resonant energy transfer. Homogeneous films of deoxycholic acid host–guests, provide coatings that convert near‐UV light into blue light with an efficiency higher than that of the standard polymeric blends.
464.
Ranieri Bizzarri Michela Serresi Stefano Luin Fabio Beltram 《Analytical and bioanalytical chemistry》2009,393(4):1107-1122
Green fluorescent protein (GFP) and its variants have been used as fluorescent reporters in a variety of applications for
monitoring dynamic processes in cells and organisms, including gene expression, protein localization, and intracellular dynamics.
GFP fluorescence is stable, species-independent, and can be monitored noninvasively in living cells by fluorescence microscopy,
flow cytometry, or macroscopic imaging techniques. Owing to the presence of a phenol group on the chromophore, most GFP variants
display pH-sensitive absorption and fluorescence bands. Such behavior has been exploited to genetically engineer encodable
pH indicators for studies of pH regulation within specific intracellular compartments that cannot be probed using conventional
pH-sensitive dyes. These pH indicators contributed to shedding light on a number of cell functions for which intracellular
pH is an important modulator. In this review we discuss the photophysical properties that make GFPs so special as pH indicators
for in vivo use and we describe the probes that are utilized most by the scientific community. 相似文献
465.
Andrea Carrer Claudio Laquatra Ludovica Tommasin Michela Carraro 《Molecules (Basel, Switzerland)》2021,26(21)
The permeability transition (PT) is an increased permeation of the inner mitochondrial membrane due to the opening of the PT pore (PTP), a Ca2+-activated high conductance channel involved in Ca2+ homeostasis and cell death. Alterations of the PTP have been associated with many pathological conditions and its targeting represents an incessant challenge in the field. Although the modulation of the PTP has been extensively explored, the lack of a clear picture of its molecular nature increases the degree of complexity for any target-based approach. Recent advances suggest the existence of at least two mitochondrial permeability pathways mediated by the F-ATP synthase and the ANT, although the exact molecular mechanism leading to channel formation remains elusive for both. A full comprehension of this to-pore conversion will help to assist in drug design and to develop pharmacological treatments for a fine-tuned PT regulation. Here, we will focus on regulatory mechanisms that impinge on the PTP and discuss the relevant literature of PTP targeting compounds with particular attention to F-ATP synthase and ANT. 相似文献
466.
467.
Sergio Sisti Fabio Ioele Filippo Scarchilli Dr. Marco Galeotti Prof. Gino A. DiLabio Prof. Michela Salamone Prof. Massimo Bietti 《European journal of organic chemistry》2023,26(37):e202300419
Kinetic and product studies on the reactions of tert-alkoxyl radicals with secondary and tertiary alkanamides bearing benzylic α-C−H bonds, isoindoline, tetrahydroisoquinoline and the corresponding N-acetyl derivatives were carried out. Product studies on the reactions with the tert-butoxyl radical (tBuO⋅) point toward exclusive HAT from the benzylic α-C−H bonds. Comparison of the kH values measured for reaction with the cumyloxyl radical (CumO⋅) with those obtained previously for the corresponding reactions of N-alkyl- and N,N-dialkylalkanamides, are indicative of a lack of benzylic activation and the operation of steric and stereoelectronic effects. Compared to N-methyl and N-ethyl groups, the presence of N-benzyl groups increases the barrier required to reach the optimal conformation for HAT, where the α-C−H bond to be cleaved is perpendicular to the plane of the amide, precluding concurrent overlap with the phenyl π-system. When the benzylic α-C−H bonds are in a conformation that allows for optimal overlap with both the phenyl π-system and the amide π-system or amine nitrogen lone pair, as in the isoindoline and tetrahydroisoquinoline derivatives, increases in kH that exceed 2-orders of magnitude were observed, highlighting the strong contribution provided by stereoelectronic activation to these HAT processes. 相似文献
468.