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991.
Yu-Yen Kao Kung-Tien Liu Ming-Feng Huang Tai-Chia Chiu Huan-Tsung Chang 《Journal of chromatography. A》2010,1217(4):582-587
We describe simultaneous analysis of naphthalene-2,3-dicarboxaldehyde (NDA)-amino acid and NDA-biogenic amine derivatives by CE in conjunction with light-emitting diode-induced fluorescence detection using poly(ethylene oxide) (PEO) solutions containing sodium dodecyl sulfate (SDS). After sample injection, via EOF 0.1% PEO prepared in 100 mM TB solution (pH 9.0) containing 30 mM SDS entered a capillary filled with 0.5 M TB solution (pH 10.2) containing 40 mM SDS. Under this condition, 14 NDA-amino acid and NDA-amine derivatives were separated within 16 min, with high efficiency ((1.0–3.2) × 105 theoretical plates) and sensitivity (LODs at S/N = 3 ranging from 2.06 to 19.17 nM). In the presence of SDS and PEO, analytes adsorption on the capillary wall was suppressed, leading to high efficiency and reproducibility. The intraday analysis RSD values (n = 3) of the mobilities for the analytes are less than 0.52%. We have validated the practicality of this approach by quantitative determination of 9 amino acids in breast cancer cells (MCF-7) and 10 amino acids in normal epithelial cells (H184B5F5/M10). The concentrations of Tau and Gln in the MCF-7 cells were different than those in the H184B5F5/M10 cells, respectively. Our results show the potential of this approach for cancer study. 相似文献
992.
This review article provides a critical overview of several different synthetic approaches developed for asymmetric preparation of fluorine-containing amines, amino alcohols, α- and β-amino acids. The common feature of these methods is the application of sulfinyl group as a chiral auxiliary to control the stereochemical outcome of the reactions under study. In particular, the following general methods are critically discussed: diastereoselective methylene transfer from diazomethane to the carbonyl of β-keto-γ-fluoroalkyl sulfoxides as a general approach for preparation of various α-fluoroalkyl α-sulfinylalkyl oxiranes. The resulting compounds were used as true chiral synthons for their further elaboration via oxidative or reductive desulfurization, to numerous fluorine-containing and biologically relevant amino- and hydroxy-containing derivatives. Another general approaches discussed here are asymmetric additions to CN double bond. One of them is addition of chiral sulfoxide stabilized carbon nucleophiles to fluorine-containing imines, leading to convenient preparation of alpha-fluoroalkyl derivatives of alpha amino acids and amines. Another approach is asymmetric Reformatsky reaction between N-sulfinyl imines and ethyl bromodifluoroacetate allowing operationally convenient preparation of α,α-difluoro-β-amino acids in enantiomerically pure form. Finally, structurally similar but mechanistically different addition reactions of diethyl difluoromethylphosphonate to N-sulfinyl imines, as a general approach to asymmetric synthesis of α,α-difluoro-β-aminophosphonates and phosphonic acids, are discussed. Effect of fluorine on the mechanism and stereochemical outcome of these reactions is discussed in detail and compared, where it is possible, with that of the analogous reactions of fluorine-free substrates. 相似文献
993.
Pavel K. Mykhailiuk Nataliia M. Voievoda Sergii Afonin Igor V. Komarov 《Journal of fluorine chemistry》2010,131(2):217-1302
An optimized procedure for the multigram synthesis of 3-(trifluoromethyl)bicyclo[1.1.1]pent-1-ylglycine (CF3-Bpg) has been developed. The overall yield of the synthesis for the optimized up-scaling was increased from 35% to 53%. Moreover, conditions for separating the key isomeric aminonitriles 7 and 8 by crystallization were found, which greatly facilitated the isolation of 8 on a multigram scale. Following this optimized protocol, 100 g of optically pure CF3-Bpg have been synthesized. 相似文献
994.
Silylated functionalized arylboronic acids were converted into corresponding iodinated arylboronic acids in good yields via the electrophilic ipso-desilylation effected with iodine chloride in refluxing CHCl3. Disilylated arylboronic acids were susceptible to diiodination. In addition, the structural characterization and reactivity of a novel sterically hindered ortho-silylated diarylborinic ester were reported. The potential of selected iodinated phenylboronic acids as monomers for the Suzuki-Miyaura cross-coupling polymerization was demonstrated. 相似文献
995.
Anke Schmauder Dipl.‐Chem. L. David Sibley Prof. Martin E. Maier Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(14):4328-4336
The first total synthesis of the cyclodepsipeptide chondramide A ( 2 b ) is described. This depsipeptide is composed of four subunits, namely L ‐alanine, N‐Me‐D ‐tryptophan, 3‐amino‐2‐methoxy‐propionic acid (β‐tyrosine derivative), and a 7‐hydroxy‐alkenoic acid. While the configuration of the stereogenic centers in the 7‐hydroxy‐alkenoic acid were known, the configuration of the tyrosine derivative required clarification and turned out to be (2S,3R) or (2L ,3L ), respectively. The synthesis of the 3‐amino‐2‐methoxy‐3‐arylpropanoic ester 20 b relied on an asymmetric dihydroxylation yielding diol ent‐ 15 a followed by a regioselective Mitsunobu substitution leading to 3‐azido‐2‐hydroxypropanoate 18 b . We could also show that the ester bond in the seco compound 26 b can be fashioned by a Mitsunobu esterification by using hydroxy ester (7S)‐ 7 and the tripeptide acid 25 b . This synthesis should allow for the preparation of various analogues. 相似文献
996.
Lei Yang Dr. Qiming Zhu Shengmei Guo Bo Qian Chungu Xia Hanmin Huang Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(5):1638-1645
A cooperative catalytic system established by the combination of an iron salt and a chiral Brønsted acid has proven to be effective in the asymmetric Friedel–Crafts alkylation of indoles with β‐aryl α′‐hydroxy enones. Good to excellent yields and enatioselectivities were observed for a variety of α′‐hydroxy enones and indoles, particularly for the β‐aryl α′‐hydroxy enones bearing an electron‐withdrawing group at the para position of the phenyl ring (up to 90 % yield and 91 % ee). The proton of the chiral Brønsted acid, the Lewis acid activation site, as well as the inherent basic site for the hydrogen‐bonding interaction of the Brønsted acid are responsible for the high catalytic activities and enantioselectivities of the title reaction. A possible reaction mechanism was proposed. The key catalytic species in the catalytic system, the phosphate salt of FeIII, which was thought to be responsible for the high activity and good enantioselectivity, was then confirmed by ESIMS studies. 相似文献
997.
Nathalie Dupré Pauline Rémy Dr. Kévin Micoine Dr. Cécile Boglio Dr. Serge Thorimbert Dr. Emmanuel Lacôte Dr. Bernold Hasenknopf Prof. Max Malacria Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(24):7256-7264
The preparation of new organosoluble Lewis acidic polyoxometalates (POMs) is reported. These complexes were prepared by the incorporation of Zr, Sc, and Y atoms into the corresponding monolacunary Dawson [P2W17O61]10? and Keggin [PW11O39]7? polyoxotungstates. The catalytic activity of these compounds was evaluated for C? C bond formation in the Diels–Alder, Mannich, and Mukaiyama‐type reactions. Comparisons with previously described Lewis acidic POMs are reported. Competitive reactions between imines and aldehydes or between various imines demonstrated that fine tuning of the reactivity could be reached by varying the metal atom incorporated into the polyanionic framework. A series of experiments that employed pyridine derivatives allowed us to distinguish between the Lewis and induced Brønsted acidity of the POMs. These catalysts activate imines in a Lewis acidic way, whereas aldehydes are activated by indirect Brønsted catalysis. 相似文献
998.
Gaku Fukuhara Dr. Yoshihisa Inoue Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(26):7859-7864
An enantiomeric binaphthyl unit was tethered to adjacent thiophenes with oxyethylene linkers to give a chiral polythiophene with binaphthocrown ether cavities. Upon inclusion of a chiral cationic guest in the cavity of the chiral crown ether–polythiophene conjugate, the bithiophene unit was twisted to shorten the effective conjugation length of polythiophene backbone, enabling us to sense the guest binding by reading out the amplified optical signal gains arising from the backbone structure change. This strategy allowed us to discriminate the guest chirality without using chiroptical signals or a circular dichroism spectrometer to achieve the highest enantioselectivity of 7.3 for valine methyl ester with a 40‐fold enhanced sensitivity compared with the corresponding monomeric sensor. 相似文献
999.
The development of a two phase hollow fiber liquid-phase microextraction technique, followed by gas-chromatography-flame ionization detection (GC-FID) for the profiling of the fatty acids (FAs) (lauric, myristic, palmitic, stearic, palmitoleic, oleic, linoleic, linolenic and arachidic) in vegetable oils is described. Heptadecanoic acid methyl ester was used as the internal standard. The FAs were transesterified to their corresponding methyl esters prior to the extraction. Extraction parameters such as type of extracting solvent, temperature, extraction time, stirring speed and salt addition were studied and optimized. Recommended conditions were extraction solvent, n-tridecane; extraction time, 35 min; extraction temperature, ambient; without addition of salt. Enrichment factors varying from 37 to 115 were achieved. Calibration curves for the nine FAs were well correlated (r(2)>0.994) within the range of 10-5000 μg L(-1). The limit of detection (signal:noise, 3) was 4.73-13.21 ng L(-1). The method was successfully applied to the profiling of the FAs in palm oils (crude, olein, kernel, and carotino cooking oil) and other vegetable oils (soybean, olive, coconut, rice bran and pumpkin). The encouraging enrichments achieved offer an interesting option for the profiling of the minor and major FAs in palm and other vegetable oils. 相似文献
1000.
István Ilisz Zoltán Pataj Róbert Berkecz Aleksandra Misicka Dagmara Tymecka Ferenc Fülöp Hee Jung Choi Myung Ho Hyun Antal Péter 《Journal of chromatography. A》2010,1217(7):1075-1082
Reversed-phase high-performance liquid chromatographic methods were developed for the separation of enantiomers of eleven unnatural β2-amino acids on a new chiral stationary phase, using the 11-methylene-unit spacer of aminoundecylsilica gel for the bonding of (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid as selector. The nature and concentration of the acidic and organic modifiers, the pH, the mobile phase composition, and the structures of the analytes substantially influenced the retention and resolution. Separations were carried out at constant mobile phase compositions in the temperature range 7–40 °C and the changes in enthalpy, Δ(ΔH°), entropy, Δ(ΔS°), and free energy, Δ(ΔG°) were calculated. The elution sequence was determined in some cases: the S enantiomers eluted before the R enantiomers. 相似文献