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排序方式: 共有298条查询结果,搜索用时 15 毫秒
291.
Annemarie Hollstein 《Fresenius' Journal of Analytical Chemistry》1961,182(6):456
Ohne Zusammenfassung 相似文献
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Marjolijn Woutersen Shimshon Belkin Bram Brouwer Annemarie P. van Wezel Minne B. Heringa 《Analytical and bioanalytical chemistry》2011,400(4):915-929
Biosensors based on luminescent bacteria may be valuable tools to monitor the chemical quality and safety of surface and drinking
water. In this review, an overview is presented of the recombinant strains available that harbour the bacterial luciferase
genes luxCDABE, and which may be used in an online biosensor for water quality monitoring. Many bacterial strains have been described for
the detection of a broad range of toxicity parameters, including DNA damage, protein damage, membrane damage, oxidative stress,
organic pollutants, and heavy metals. Most lux strains have sensitivities with detection limits ranging from milligrams per litre to micrograms per litre, usually with
higher sensitivities in compound-specific strains. Although the sensitivity of lux strains can be enhanced by various molecular manipulations, most reported detection thresholds are still too high to detect
levels of individual contaminants as they occur nowadays in European drinking waters. However, lux strains sensing specific toxic effects have the advantage of being able to respond to mixtures of contaminants inducing the
same effect, and thus could be used as a sensor for the sum effect, including the effect of compounds that are as yet not
identified by chemical analysis. An evaluation of the suitability of lux strains for monitoring surface and drinking water is therefore provided. 相似文献
295.
The S(1)← S(0) fluorescence excitation spectrum of jet-cooled 2-hydroxy-1-naphthaldehyde (2H1N) with origin at 26,668 cm(-1) has been measured. Nine totally symmetric modes and three non-totally symmetric modes have been assigned in the excitation spectrum. Ab initio calculations indicate that 2H1N undergoes a planarity change upon excitation, which may account for the unusual intensity of non totally symmetric vibrational modes in the excitation spectrum. A number of low intensity features were observed on the low energy side of the origin which have been assigned to the 2H1N dimer rather than different ground state confomers of 2H1N. The origin of the S(1)← S(0) electronic transition of the dimer lies at ~26,401 cm(-1); combinations of two low frequency intermolecular modes of the dimer (59 cm(-1) and 17 cm(-1)) were also observed. The occurrence of excited state intramolecular proton transfer (ESIPT) in 2H1N cannot be proven on the basis of this work. A comparison of the (photo)physical properties of 2H1N with 1-hydroxy-2-naphthaldehyde (1H2N) [A. McCarthy and A.A. Ruth, PCCP, 2011, 13, 7485-7499 (Part 1)], however, indicate the plausibility of an ESIPT process in 2H1N. The strength of the intramolecular hydrogen bond (IMHB) in 2H1N was computed as ~10.6 kcal/mol, a value comparable to the IMHB strength of 1H2N. The establishment of a lower limit on the state lifetimes of 2H1N, of ~1.8 ps, indicates that any proposed ESIPT reaction in 2H1N may not proceed barrierlessly. Above an excess energy of ~1000 cm(-1), the intensity of the fluorescence excitation spectrum reduces significantly, indicating the onset of a non-radiative decay mechanism. 相似文献
296.
Surface-enhanced ATR-IR spectroscopy with interface-grown plasmonic gold-island films near the percolation threshold 总被引:1,自引:0,他引:1
Enders D Nagao T Pucci A Nakayama T Aono M 《Physical chemistry chemical physics : PCCP》2011,13(11):4935-4941
Flat nano-island films prepared by wet-chemical deposition were investigated with attenuated total reflection infrared (ATR-IR) spectroscopy and scanning electron microscopy (SEM) in order to analyze the correlation between film morphology and optical properties. Here we choose Au as representative coinage metal (Au, Ag, Cu) that shows strong structure-dependent surface-enhanced infrared absorption (SEIRA). Infrared spectra of octadecanethiol monolayers on films of different stages of morphologic development show effects that are characteristic for SEIRA, such as enhanced vibrational signals, Fano-type line shape, and adsorbate induced baseline shifts. Their extent was found to be strongly dependent on the structural details and the strongest enhancement occurs at the percolation threshold of the two-dimensional island system. Also films beyond percolation show significant enhancement due to residual nanoholes that are acting as hotspots. 相似文献
297.
Schäfer A Winter F Saak W Haase D Pöttgen R Müller T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(39):10979-10984
The reactivity of aryl‐substituted stannylenes, Ar2Sn ( 4 ), towards silylarenium borates, [R3SiArH][B(C6F5)4] ( 3 ), was investigated. The reaction with 2,3,4‐trimethyl‐6‐tert‐butylphenyl (mebp)‐substituted stannylene gave silyl‐substituted stannylium ions 2 a , b , which were characterized by NMR spectroscopy supported by the results of quantum‐mechanical computations of molecular structures and magnetic properties. The tri‐iso‐propylphenyl‐substituted stannylium ions 2 c , d undergo a decomposition reaction in toluene to give the dicationic tin–arene complex [Sn(C7H8)3]2+ ( 5 ) in the form of the [B(C6F5)4] salt in high yields. The 5 [B(C6F5)4]2 salt was identified by single crystal X‐ray diffraction analysis and by Mössbauer spectroscopy. The bonding situation was investigated by using natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM) calculations. The substitution of the weakly coordinating borate anion by the carboranate [CB11H6Br6]? results in replacement of the toluene ligands and formation of tin(II) carboranate with only weak Sn2+–anion interactions as suggested by the solid‐state structure of the isolated salt. 相似文献
298.