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1.
2.
Relative molar responses (RMRs) of some straight-chain aliphatic alkanes, ketones, aldehydes, alcohols, carboxylic acids, primary amines, aniline, and nitrobenzene derivatives were investigated related to naphthalene. Most of the respective compounds have not been investigated yet due to their high polarity or high boiling point. The earlier cross section data for oxygenated compounds were changed to RMRs which are more utilizable from an analytical aspect. A linear correlation was found between the RMRs and the carbon atom numbers in primary amines. In the cases of aniline and nitrobenzene derivatives the RMRs were also determined; however, no functional relationship was found. The measurement conditions, i.e., the type of column affect the apparent RMRs of aliphatic primary amines. A midpolar column having a higher maximum operating temperature provides a more sensitive apparent RMR (Rtx-1701) than the basic polar column having a lower maximum temperature (Stabilwax-DB), because a high temperature allows setting a higher injector temperature and a higher amount of compound can reach the ion source. Knowing correlations the quantitative analysis passes into easier and fewer reference materials are needed to investigate a sample having many components, because the sensitivities can be determined from the correlations studied in this paper. This is also valid for aromatic compounds, even though no functional relationship exists. 相似文献
3.
Skeleton Decoration of NHCs by Amino Groups and its Sequential Booster Effect on the Palladium‐Catalyzed Buchwald–Hartwig Amination 下载免费PDF全文
Yin Zhang Dr. Vincent César Golo Storch Dr. Noël Lugan Dr. Guy Lavigne 《Angewandte Chemie (International ed. in English)》2014,53(25):6482-6486
A challenging synthetic modification of PEPPSI‐type palladium pre‐catalysts consisting of a stepwise incorporation of one and two amino groups onto the NHC skeleton was seen to exert a sequential enhancement of the electronic donor properties. This appears to be positively correlated with the catalytic performances of the corresponding complexes in the Buchwald–Hartwig amination. This is illustrated, for example, by the quantitative amination of 4‐chloroanisole by morpholine within 2 h at 25 °C with a 2 mol % catalyst/substrate ratio or by a significant reduction of catalytic loading (down to 0.005 mol %) for the coupling of aryl chlorides with anilines (max TON: 19 600). 相似文献
4.
利用KrF激光泵浦高压H_2,在同轴前向的受激拉曼散射(SRS)作用下,产生受激拉曼放大,1阶Stokes光对泵浦光的转换效率为17.2%,并对影响放大过程和转换效率的若干因素作了分析。 相似文献
5.
Maxime Noël Sergey Ananev Mattias Mases Xavier Devaux Juhan Lee Ivan Evdokimov Manuel Dossot Edward McRae Alexander V. Soldatov 《固体物理学:研究快报》2014,8(11):935-938
We report on a first study of single walled carbon nanotubes (SWCNTs) after application of dynamic (shock) compression. The experiments were conducted at 19 GPa and 36 GPa in a recovery assembly. For comparison, an experiment at a static pressure of 36 GPa was performed on the material from the same batch in a diamond anvil cell (DAC). After the high pressure treatment the samples were characterized by Raman spectroscopy and transmission electron microscopy (TEM). After exposure to 19 GPa of shock compression the CNT material exhibited substantial structural damage such as CNT wall disruption, opening of the tube along its axis (“unzipping”) and tube shortening (“cutting”). Dynamic compression to 36 GPa resulted in essentially complete CNT destruction whereas at least a fraction of the nanotubes was recovered after 36 GPa of static compression though severely damaged. The results of these shock wave experiments underline the prospect of using SWCNTs as reinforcing units in material WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
6.
Understanding the activity and selectivity of molecular catalysts for CO2 reduction to fuels is an important scientific endeavour in addressing the growing global energy demand. Cobalt–terpyridine compounds have been shown to be catalysts for CO2 reduction to CO while simultaneously producing H2 from the requisite proton source. To investigate the parameters governing the competition for H+ reduction versus CO2 reduction, the cobalt bisterpyridine class of compounds is first evaluated as H+ reduction catalysts. We report that electronic tuning of the ancillary ligand sphere can result in a wide range of second-order rate constants for H+ reduction. When this class of compounds is next submitted to CO2 reduction conditions, a trend is found in which the less active catalysts for H+ reduction are the more selective towards CO2 reduction to CO. This represents the first report of the selectivity of a molecular system for CO2 reduction being controlled through turning off one of the competing reactions. The activities of the series of catalysts are evaluated through foot-of-the-wave analysis and a catalytic Tafel plot is provided. 相似文献
7.
José Luis Martínez-Hernández Marco Arnulfo Mata-Gómez Cristóbal Noé Aguilar-González Anna Ilyina 《Applied biochemistry and biotechnology》2010,160(7):2045-2053
The production of extracellular and mycelia-associated penicillin G acylase (maPGA) with Mucor griseocyanus H/55.1.1 by surface-adhesion fermentation using Opuntia imbricata, a cactus, as a natural immobilization support was studied. Enzyme activity to form 6-aminopencillanic acid (6-APA) from
penicillin G was assayed spectrophotometrically. The penicillin G hydrolysis to 6-APA was evaluated at six different times
using PGA samples recovered from the skim milk medium at five different incubation times. Additionally, the effect of varying
the penicillin G substrate concentration level on the PGA enzyme activity was also studied. The maximum reaction rate, V
max, and the Michaelis constant, K
M, were determined using the Michaelis–Menten model. The maximum levels for maPGA and extracellular activity were found to
be 2,126.50 international unit per liter (IU/l; equal to 997.83 IU/g of support) at 48 h and 755.33 IU/l at 60 h, respectively.
Kinetics of biomass production for total biomass showed a maximum growth at 60 h of 3.36 and 2.55 g/l (equal to 0.012 g of
biomass per gram of support) for the immobilized M. griseocyanus biomass. The maPGA was employed for the hydrolysis of penicillin G to obtain 6-APA in a batch reactor. The highest quantity
of 6-APA obtained was 226.16 mg/l after 40-min reaction. The effect of substrate concentration on maPGA activity was evaluated
at different concentrations of penicillin G (0–10 mM). K
M and V
max were determined to be 3.0 × 10−3 M and 4.4 × 10−3 mM/min, respectively. 相似文献
8.
The determination of seven arsenic species in seafood was performed using ion exchange chromatography on an IonPac AS7 column with inductively coupled plasma mass spectrometry detection after microwave assisted extraction. The effect of five parameters on arsenic extraction recoveries was evaluated in certified reference materials. The recoveries of total arsenic and of arsenic species with the two best extraction media (100% H2O and 80% aqueous MeOH) were generally similar in the five seafood certified reference materials considered. However, because MeOH co-elutes with arsenite, which would result in a positively biased arsenite concentration, the 100% H2O extraction conditions were selected for validation of the method. Figures of merit (linearity, LOQs (0.019-0.075 mg As kg−1), specificity, trueness (with recoveries between 82% (As(III)) and 104% (As(V) based on spikes or certified concentrations), repeatability (3-14%), and intermediate precision reproducibility (9-16%) of the proposed method were satisfactory for the determination of arsenite, monomethylarsonic acid, dimethylarsinic acid, arsenate, arsenobetaine and arsenocholine in fish and shellfish. The performance criteria for trimethylarsine oxide, however, were less satisfactory. The method was then applied to 65 different seafood samples. Arsenobetaine was the main species in all samples. The percentage of inorganic arsenic varied between 0.4-15.8% in shellfish and 0.5-1.9% at the utmost in fish. The main advantage of this method that uses only H2O as an extractant and nitric acid as gradient eluent is its great compatibility with the long-term stability of both IEC separation and ICP-MS detection. 相似文献
9.
10.
Gabriele Laudadio Sebastian Govaerts Ying Wang Davide Ravelli Hannes F. Koolman Maurizio Fagnoni Stevan W. Djuric Prof. Timothy Noël 《Angewandte Chemie (International ed. in English)》2018,57(15):4078-4082
A mild and selective C(sp3)?H aerobic oxidation enabled by decatungstate photocatalysis has been developed. The reaction can be significantly improved in a microflow reactor enabling the safe use of oxygen and enhanced irradiation of the reaction mixture. Our method allows for the oxidation of both activated and unactivated C?H bonds (30 examples). The ability to selectively oxidize natural scaffolds, such as (?)‐ambroxide, pregnenolone acetate, (+)‐sclareolide, and artemisinin, exemplifies the utility of this new method. 相似文献