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111.
Pulse propagation in a random medium is mainly determined by the two-frequency mutual coherence function which satisfies the parabolic equation. It has recently been shown that this equation can be solved by separation of variables, thereby reducing the solution for any structure function to the solution of ordinary differential equations. In this paper, the method is applied for a beam-wave excitation in a random medium. The exact solution for a quadratic medium is derived. For non-quadratic power-law media an analytical expression at equal positions is presented. 相似文献
112.
Jasmin Bühler Sandra Muth Karl Fischer Manfred Schmidt 《Macromolecular rapid communications》2013,34(7):588-594
A high‐molar‐mass cylindrical brush polymer with a main chain degree of polymerization of Pw = 1047 is synthesized by free‐radical polymerization of a poly‐2‐isopropyloxazoline macromonomer with Pn = 28. The polymerization is conducted above the lower phase transition temperature of the macromonomer, i.e., in the phase‐separated regime, which provides a sufficiently concentrated macromonomer phase mandatory to obtain high‐molar‐mass cylindrical brushes. Upon heating to the phase transition temperature, the hydrodynamic radius is observed to shrink from 34 to 27 nm. Further increase in temperature resulted in aggregated chains which were observed to coexist with single chains until eventually only aggregates of μm size were detectable.
113.
Hongjuan Dong Jasmin Kemptner Martina Marchetti-Deschmann Christian Peter Kubicek Günter Allmaier 《Analytical and bioanalytical chemistry》2009,395(5):1373-1383
Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI–TOF MS) has been proved to be a powerful
tool for the identification and characterization of microorganisms based on their surface peptide/protein pattern. Because
of the complexity of microorganisms, there are no standardized protocols to acquire reproducible peptide/protein profiles
for a broad range of microorganisms and for fungi in particular. Small variations during MALDI MS sample preparation affect
the quality of mass spectra quite often. In this study, we were aiming to develop a sample preparation method for the analysis
of colored, a quite often observed phenomenon, and mycotoxin-producing Fusarium conidia spores using MALDI–TOF MS. Different washing solvent systems for light- and deep-colored (from slightly orange to
red-brown) conidia spores and connected sample deposition techniques were evaluated based on MS reproducibility and number
and intensities of peaks. As a method of choice for generation of reproducible and characteristic MALDI–TOF mass spectra,
the use of a washing process for colored Fusarium conidia spores with acetonitrile/0.5% formic acid (7/3) was found and subsequently combined with two-layer volume technique
(spores/matrix (ferulic acid) solution was deposited onto a MALDI target, and after solvent evaporation, a second matrix layer
was deposited). With the application of this sample preparation method, for deep-colored Fusarium species, 19 abundant molecular ions in the m/z range 2,000–10,000 were always detected with an S/N ratio of 3:1 or better. Finally this optimized sample preparation for
the first time provided mass spectrometric fingerprints of strongly colored Fusarium conidia spores resulting in the possibility of differentiation of such spores at the species level.
相似文献
114.
From Praxelis clematidea a phenylalanine derivative has been isolated, its structure being elucidated by spectroscopic methods and confirmed by synthesis. 相似文献
115.
The aerial parts of afforded in addition to asteriscunolides A, B, C and D twelve further humulene derivatives, two bicyclic compounds also derived from humulene, a bisabolene derivative and the diisovalerate of coniferyl alcohol. The structures and the configurations of these compounds were determined mainly by spectroscopic methods. The problem of the proposed isolation of “stable conformers” of the asteriscunolides is discussed. 相似文献
116.
Cyclocondensation of 2,4,6-triaminopyrimidine ( 4 ) with ethyl N-benzyl-4-oxo-3-pyrrolidine carboxylate ( 5 ) in diphenyl ether regiospecifically afforded a new tricyclic, angular 1,3,8-trisubstituted pyrrolo[3′,4′:4,5]-pyrido[2,3-d]pyrimidine-6-one 1 in excellent yield. The ketoester 5 was prepared by a literature method. Compound 1 in addition to being a new heterocyclic system is an important key precursor to a variety of classical and nonclassical tricyclic, 5-deaza analogues of the folate cofactor 5,10-methylenetetrahydrofolate 3 . 相似文献
117.
[structure: see text] The first enantioselective total synthesis of tonantzitlolone, a novel 15-membered macrocyclic diterpene, utilized a Julia olefination, a highly selective, potassium enolate-based anti-Felkin aldol reaction, and an E-selective ring-closing metathesis as key C-C bond-forming steps. The absolute configuration of tonantzitlolone is established. 相似文献
118.
Faure S Stern C Espinosa E Douville J Guilard R Harvey PD 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(11):3469-3481
Eleven new complexes, including mono-, heterobi-, and homobimetallic cofacial bisporphyrins, (Pd)H2DPS, (M)H2DPX, (M)H2DPB, (PdZn)DPS, (PdZn)DPX, (Pt)2DPX, (M)2DPB (M = Pd, Pt), and (Pt)P (DPS4- = 4,6-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]dibenzothiophene tetraanion, DPX(4-) = 4,5-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]-9,9-dimethylxanthene tetraanion, DPB4- = 1,8-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]biphenylene tetraanion, P2- = 5-phenyl-2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrin dianion) have been synthesized and characterized. The photophysical properties of the donor (M)P (M=Pd or Pt, P=porphyrin chromophore) and the acceptor (free base H(2)P or (Zn)P) depend on the C(meso)-C(meso) distance and the presence of a heavy atom such as Pd(II) or Pt(II). The data were compared with those for the known compounds (Pd)2DPS, (Pd)2DPX, H4DPS, H4DPX, H4DPB, (Pd)P, (Zn)P, and H(2)P. The rate constants for triplet-triplet energy transfer (k(ET)) were measured for the heterobimetallic (PdZn) and monometallic [(M)H2] derivatives (M=Pd, Pt). The fluorescence lifetimes (Deltatau(F)) of the acceptors decrease as a result of the heavy-atom effect, and vary as follows: (Pd)H2DPS<(Pd)H2DPX approximately (Pd)H2DPB. The k(ET) values calculated according to the equation k(ET)=(1/tau(emi)-1/tau(emi) (0)), where tau(emi) (0) is the emission lifetime of the homobimetallic bisporphyrins (no ET occurs), are equal to 0, 247+/-57 and 133+/-52 s(-1) for DPS, DPX, and DPB, respectively, in the (Pd)H(2) series. These measurements allowed the range of distance over which the Dexter mechanism for T(1)-T(1) energy transfer ceases to operate to be determined. This distance is somewhere between 4.3 and 6.3 A, in agreement with our recent findings on singlet-singlet energy transfer. During the course of this study, the X-ray crystal structure for (Pd)H2DPX was obtained; triclinic (P1), a = 11.1016(1), b = 14.9868(2), c = 20.6786(3) A, alpha = 102.091(1), beta = 100.587(1), gamma = 101.817(1) degrees , V = 3199.19(7) A(3), Z = 2. 相似文献
119.
The aerial parts of Chromolaena laevigata gave four new compounds derived from chromolaenin, four clerodane derivatives and a new type of norsesquiterpenes as well as two sesquiterpenes with a new carbon skeleton. 相似文献
120.