全文获取类型
收费全文 | 531篇 |
免费 | 12篇 |
国内免费 | 3篇 |
专业分类
化学 | 441篇 |
晶体学 | 13篇 |
力学 | 5篇 |
数学 | 56篇 |
物理学 | 31篇 |
出版年
2022年 | 4篇 |
2021年 | 5篇 |
2020年 | 8篇 |
2019年 | 11篇 |
2018年 | 11篇 |
2017年 | 7篇 |
2016年 | 14篇 |
2015年 | 9篇 |
2014年 | 18篇 |
2013年 | 25篇 |
2012年 | 13篇 |
2011年 | 15篇 |
2010年 | 8篇 |
2009年 | 5篇 |
2008年 | 18篇 |
2007年 | 5篇 |
2006年 | 13篇 |
2005年 | 15篇 |
2004年 | 12篇 |
2003年 | 25篇 |
2002年 | 30篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 15篇 |
1995年 | 10篇 |
1994年 | 3篇 |
1993年 | 15篇 |
1992年 | 10篇 |
1991年 | 12篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 15篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 15篇 |
1981年 | 13篇 |
1980年 | 13篇 |
1979年 | 11篇 |
1978年 | 15篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1973年 | 3篇 |
1970年 | 3篇 |
1905年 | 2篇 |
排序方式: 共有546条查询结果,搜索用时 31 毫秒
91.
Vollmer W 《Chemistry & biology》2008,15(2):93-94
FtsZ is a prokaryotic homolog of eukaryotic tubulin and forms the essential bacterial cell division ring (Z-ring). A new study in this issue of Chemistry & Biology, L?ppchen et al., provides further evidence that differences in nucleotide-binding properties of FtsZ and tubulin can be exploited to specifically target the bacterial Z-ring. 相似文献
92.
Back Cover: Retention of Native Protein Structures in the Absence of Solvent: A Coupled Ion Mobility and Spectroscopic Study (Angew. Chem. Int. Ed. 45/2016)
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
93.
Sajimon MC Ramaiah D Suresh CH Adam W Lewis FD George MV 《Journal of the American Chemical Society》2007,129(30):9439-9445
Upon exposure to UV light, the disubstituted dibenzobarrelene derivative 1a turns green in the solid phase and reverts back to its original pale-yellow color within several hours in the dark. The lifetime of the colored species in degassed benzene at room temperature is 37 +/- 2 s (Ea for decoloration is 14.5 +/- 0.7 kcal mol-1 and log A is 8.92 +/- 0.5 s-1) and highly sensitive to molecular oxygen; the Stern-Volmer quenching constant is 6.9 +/- 0.2 x 108 M-1 s-1. Similarly, the disubstituted dibenzobarrelenes 1b and 1c exhibited pink coloration when exposed to UV light in the solid phase. On the basis of combined experimental and theoretical evidence, it is proposed that upon photoexcitation the excited singlet state of 1a undergoes rapid intersystem crossing to its triplet state, followed by intramolecular delta-H abstraction, to yield the triplet biradical intermediate (3)2. Upon prolonged irradiation, 2 undergoes cyclization to the alcohol 3, which affords the enone 4 as the final photoproduct. The delta-H abstraction on the triplet-state potential energy surface, calculated at the B3LYP/6-31G* level of density functional theory (DFT), has an activation energy of 18.5 kcal/mol. Further, the absorption spectrum of the triplet biradical (3)2, obtained from time-dependent DFT calculations, displays an intense absorption maximum at 670 nm, which is in good agreement with the observed absorption peak at 700 nm. The molecular-orbital analysis of the triplet diradical (3)2 suggests that its long-wavelength absorption involves the transition of the unpaired electron from the comparatively localized benzyl-type HOMO to the extensively conjugated benzoyl-type LUMO. The present experimental and theoretical results strongly support the intervention of a long-lived triplet biradical (3)2 in the photochromism of appropriately substituted dibenzobarrelenes. 相似文献
94.
Saito H Sivaguru J Jockusch S Dyer J Inoue Y Adam W Turro NJ 《Chemical communications (Cambridge, England)》2007,(8):819-821
Photoisomerization of encapsulated Z-enecarbamates within the hydrophobic chiral cavities of gamma-CD showed higher diastereoselectivities in the photoproducts than those obtained in solution. The selective encapsulation of the enecarbamates and the following isomerization process are both diastereoselectively controlled by gamma-CD. 相似文献
95.
Waldemar Adam Chantu R. Saha-Mller Simon B. Schambony Katharina S. Schmid Thomas Wirth 《Photochemistry and photobiology》1999,70(4):476-483
The stereochemical course of the singlet-oxygen ene reaction with acyclic olefins may be controlled if in the substrate conformational fixation (1,3-allylic strain) an allyl-ic substituent for interaction with the attacking oxygen enophile aligns. Various substrates were chosen to elucidate the features of the olefin that are necessary to control the sense (threo versus erythro) and the extent of the ii-facial preference of the singlet-oxygen attack. Depending on the electronic properties of the double bond and the nature of the allylic substituent, threo or erythro selectivity may be imposed through hydrogen bonding, electrostatic and steric effects and stereoelectronic alignment. Such directing properties, especially that of the hydroxy group, were also confirmed in the other reaction modes of singlet oxygen, namely the [4+2] cycloaddition to chiral naphthylenic alcohols and the [2+2] cycloaddition to an adamantylidene-substituted allylic alcohol. The syntheses of the natural products Merucathin and Iso-dihydromahubanolide B are two examples in which such stereocontrolled photooxygenations have been used as key steps to build up the required chirality diastereose-lectively. 相似文献
96.
Waldemar Studziski Wojciech Powiardowski Weronika Osiska 《Molecules (Basel, Switzerland)》2021,26(21)
During the operation of swimming pools, large losses of water from the backwash of swimming pool filters are observed. This water is often discharged into sewers or used to sprinkle sports grounds. The aim of the research was to design and build an installation for purification and recovery of backwash water (BWW). It consists of flocculation, pre-filtration, and ultrafiltration based on filter tubes and ozone disinfection. Backwash water treatment installation contributes to purification and improvement of water quality. The effectiveness of the removal of microbial contamination with the use of the system was over 99%. The high efficiency of removing physicochemical impurities was also achieved. Water turbidity was reduced from 96.9 NTU to 0.13 NTU. After using the system, the oxidability of water decreased from 6.26 mg O2∙dm−3 to 0.4 mg O2∙dm−3. When using the system, a reduction of total organic carbon by 80% was also noticed. After the treatment process, water meets the strict criteria and can be returned to the pool system of water as fresh water with parameters of supply water—directly to the overflow tank. It has been shown that up to 96% of water can be recovered with the technology. The cost comparison showed annual savings of over EUR 9000. 相似文献
97.
Juan Pablo Navarrete Waldemar Barrera 《Bulletin of the Brazilian Mathematical Society》2009,40(1):99-106
In this paper, we prove following: If G ⊂ PU (2, 1) is an infinite, discrete group, acting on Pℂ2 without complex invariant lines, then the component containing ℍPℂ2 of the domain of discontinuity Ω(G) = PPℂ2∖ Λ (G), according to Kulkarni, is G-invariant complete Kobayashi hyperbolic.
The authors were supported by the Universidad Autónoma de Yucatán and the Universidad Nacional Autónoma de México. 相似文献
98.
J. Sivaguru Catherine Hooper Marissa R. Solomon Waldemar Adam Yoshihisa Inoue Nicholas J. Turro 《Tetrahedron》2006,62(46):10647-10659
The stereoselectivity in the reactions of the E/Z enecarbamates 1, equipped with the oxazolidinone chiral auxiliary, has been examined for singlet oxygen (1O2), ozone (O3), and 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) in a variety of solvents as a function of temperature. The oxidative cleavage of the alkenyl functionality by 1O2 and O3 releases the enantiomerically enriched methyldesoxybenzoin (MDB) product. The extent (% ee) as well as the sense (R vs S) of the stereoselectivity in the MDB formation depends on the electronic nature of the oxidant. A high stereoselectivity, substantially dependent on solvent and temperature, is displayed for the reactions with 1O2, whereas the ground-state reactants O3 and PTAD are rather unaffected by solvent and temperature variations. The present comparative analysis clearly substantiates our hypothesis of stereoselective vibrational quenching of the attacking 1O2, whereas O3 and PTAD are only subject to steric impositions. The electronically excited 1O2 is sensitive to all three stereochemically relevant structural characteristics embodied in the chiral enecarbamates, namely the R/S configuration at the C4 position of the oxazolidinone chiral auxiliary, the Z/E geometry of the ‘alkene’ functionality, and R/S configuration at the C3′ position of the enecarbamate side chain. 相似文献
99.
100.
Izabela Bobowska Aleksandra Wypych-Puszkarz Agnieszka Opasinska Waldemar Maniukiewicz Piotr Wojciechowski 《Phase Transitions》2017,90(1):44-53
ABSTRACTEffects of the elevated temperature on the structure evolution of the ZnO nanorod array (ZNA) and their hybrid nanocomposite with layered (tetramethyl)ammonium titanate (LTMAT) prepared by the liquid phase deposition were investigated. The vertically oriented ZnO nanorods were deposited on a quartz plate by a chemical bath deposition method and then they were penetrated by the LTMAT using the dip-coating method from the water solution. As a result of such an experimental procedure, an assembly composed of the ZNA with LTMAT was obtained and called hybrid nanocomposite. Since the LTMAT converts to TiO2 upon subsequent sintering at 350 °C, it can be regarded as TiO2 precursor for the thermal treatment experiments. The experiments with ZNA and their hybrid nanocomposite at the elevated temperature revealed coalescence of the deposited ZnO nanorods and crystallization of zinc titanate with Zn2TiO4 stoichiometry. 相似文献