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101.
George L Sander W 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(13):3225-3232
The infrared spectra of the formic acid-water complexes isolated in argon matrices are reported. Both supersonic jet expansion and a conventional effusive source followed by trapping in solid argon at 10K are used to obtain the matrices. The experimental IR spectra are compared to the data obtained from high level ab initio (MP2) and DFT (B3LYP) calculations with 6-311++G(d,p) and aug-cc-pVTZ basis sets. The complex formation results in red shifts in the C=O and O-H stretching vibrations and a blue shift in the C-O stretching vibration of formic acid. The O-H stretching modes of water also exhibit pronounced red shifts. Both the MP2 and B3LYP calculations located three minima corresponding to cyclic HCOOH...H2O complexes with two hydrogen bond interactions. The binding energies are -10.3, -5.1, and -3.5 kcal mol(-1), respectively, for the three complexes at the MP2/ aug-cc-pVTZ level, corrected for the basis set superposition error (BSSE) using the Boys-Bernardi counterpoise scheme. Comparison of the calculated frequencies of the three complexes with the matrix IR spectrum reveals that the lowest energy complex is formed. In addition, a complex of formic acid with two water molecules is observed. 相似文献
102.
Wayland E. Noland Mary J. Walhstrom Michael J. Konkel Mark E. Brigham Annette G. Trowbridge Lisa M. C. Konkel Ronald P. Gourneau Cheryl A. Scholten Nina H. Lee John J. Condoluci Todd S. Gac Mehrdad Mostafaei Pour Peter M. Radford 《Journal of heterocyclic chemistry》1993,30(1):81-91
Tetrahydrocarbazoles have been prepared in one-flask syntheses from indoles, ketones or aldehydes, and maleimides, with acid catalysis. The reactions involve a condensation of the indole with the ketone or aldehyde, followed by an in situ trapping of the vinylindole in a Diels-Alder addition with a maleimide. Isomerization of the double bond into the indole nucleus gave the tetrahydrocarbazoles which were isolated ( 6, 9 , and 10 ). Variation of the indole, carbonyl compound, and maleimide has been explored. The predominant stereochemistry of the tetrahydro ring in the products is all-cis, although a second stereoisomer has been isolated. Two regioisomers were generated from all unsymmetrical 2-alkanones, except 2-butanone, which gave the single isomer 9a . Aromatization of tetrahydrocarbazoles 6 to carbazoles 7 was accomplished with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone. 相似文献
103.
Lisa Beck 《Annali di Matematica Pura ed Applicata》2011,190(4):553-588
We consider weak solutions ${u \in u_0 + W^{1,2}_0(\Omega,\mathbb{R}^N) \cap L^{\infty}(\Omega,\mathbb{R}^N)}$ of second-order nonlinear elliptic systems of the type $$- {\rm div} \,a (\, \cdot \,, u, Du ) = b(\, \cdot \,,u,Du)\qquad \text{ in }\Omega$$ with an inhomogeneity satisfying a natural growth condition. In dimensions ${n \in \{2,3,4\}}$ , we show that ${\mathcal{H}^{n-1}}$ -almost every boundary point is a regular point for Du, provided that the boundary data and the coefficients are sufficiently smooth. 相似文献
104.
Ni(II) complexation to amorphous hydrous ferric oxide: an X-ray absorption spectroscopy study 总被引:2,自引:0,他引:2
Xu Y Axe L Boonfueng T Tyson TA Trivedi P Pandya K 《Journal of colloid and interface science》2007,314(1):10-17
Ni(II) sorption onto iron oxides and in particular hydrous ferric oxide (HFO) is among the important processes impacting its distribution, mobility, and bioavailability in environment. To develop mechanistic models for Ni, extended X-ray absorption fine structure (EXAFS) analysis has been conducted on Ni(II) sorbed to HFO. Coprecipitation revealed the formation of the metastable alpha-Ni(OH)(2) at a Ni(II) loading of 3.5 x 10(-3) molg(-1). On the other hand, Ni(II) formed inner-sphere mononuclear bidentate complexes along edges of FeO(6) octahedra when sorbed to HFO surfaces with Ni-O distances of 2.05-2.07 A and Ni-Fe distances of 3.07-3.11 A. This surface complex was observed by EXAFS study over 2.8 x 10(-3) to 10(-1) ionic strength, pH from 6 to 7, a Ni(II) loading of 8 x 10(-4) to 8.1 x 10(-3) molg(-1) HFO, and reaction times from 4 hours to 8 months. The short- and long-range structure analyses suggest that the presence of Ni(II) inhibited transformation of the amorphous iron oxide into a more crystalline form. However, Ni(2+) was not observed to substitute for Fe(3+) in the oxide structure. This study systematically addresses Ni(II) adsorption mechanisms to amorphous iron oxide. The experimentally defined surface complexes can be used to constrain surface complexation modeling for improved prediction of metal distribution at the iron oxide/aqueous interface. 相似文献
105.
Gong J Vaidyanathan VG Yu X Kensler TW Peterson LA Sturla SJ 《Journal of the American Chemical Society》2007,129(7):2101-2111
Acylfulvenes (AFs) are a class of semisynthetic agents with high toxicity toward certain tumor cells, and for one analogue, hydroxymethylacylfulvene (HMAF), clinical trials are in progress. DNA alkylation by AFs, mediated by bioreductive activation, is believed to contribute to cytotoxicity, but the structures and chemical properties of corresponding DNA adducts are unknown. This study provides the first structural characterization of AF-specific DNA adducts. In the presence of a reductive enzyme, alkenal/one oxidoreductase (AOR), AF selectively alkylates dAdo and dGuo in reactions with a monomeric nucleoside, as well as in reactions with naked or cellular DNA, with 3-alkyl-dAdo as the apparently most abundant AF-DNA adduct. Characterization of this adduct was facilitated by independent chemical synthesis of the corresponding 3-alkyl-Ade adduct. In addition, in naked or cellular DNA, evidence was obtained for the formation of an additional type of adduct resulting from direct conjugate addition of Ade to AF followed by hydrolytic cyclopropane ring-opening, indicating the potential for a competing reaction pathway involving direct DNA alkylation. The major AF-dAdo and AF-dGuo adducts are unstable under physiologically relevant conditions and depurinate to release an alkylated nucleobase in a process that has a half-life of 8.5 h for 3-alkyladenine and less than approximately 2 h for dGuo adducts. DNA alkylation further leads to single-stranded DNA cleavage, occurring exclusively at dGuo and dAdo sites, in a nonsequence-specific manner. In AF-treated cells that were transfected with either AOR or control vectors, the DNA adducts identified match those from in vitro studies. Moreover, a positive correlation was observed between DNA adduct levels and cell sensitivity to AF. The potential contributing roles of AOR-mediated bioactivation and adduct stability to the cytotoxicity of AF are discussed. 相似文献
106.
Lisa A. Bischoff Jarno Riefer Raphael Wirthensohn Tobias Bischof Rüdiger Bertermann Dr. Nikolai V. Ignat'ev Prof. Dr. Maik Finze 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(60):13615-13620
Salts of the tetrakis(pentafluoroethyl)aluminate anion [Al(C2F5)4]− were obtained from AlCl3 and LiC2F5. They were isolated with different counter-cations and characterized by NMR and vibrational spectroscopy and mass spectrometry. Degradation of the [Al(C2F5)4]− ion was found to proceed via 1,2-fluorine shifts and stepwise loss of CF(CF3) under formation of [(C2F5)4−nAlFn]− (n=1–4) as assessed by NMR spectroscopy and mass spectrometry and supported by results of DFT calculations. In addition, the [(C2F5)AlF3]− ion was structurally characterized. 相似文献
107.
A Visible Light Photocatalytic Cross‐Dehydrogenative Coupling/Dehydrogenation/6π‐Cyclization/Oxidation Cascade: Synthesis of 12‐Nitroindoloisoquinolines from 2‐Aryltetrahydroisoquinolines 下载免费PDF全文
Fabian Rusch Lisa‐Natascha Unkel Dirk Alpers Dr. Frank Hoffmann Prof. Dr. Malte Brasholz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(23):8336-8340
A visible light‐induced photocatalytic dehydrogenation/6π‐cyclization/oxidation cascade converts 1‐(nitromethyl)‐2‐aryl‐1,2,3,4‐tetrahydroisoquinolines into novel 12‐nitro‐substituted tetracyclic indolo[2,1‐a]isoquinoline derivatives. Various photocatalysts promote the reaction in the presence of air and a base, the most efficient being 1‐aminoanthraquinone in combination with K3PO4. Further, the 12‐nitroindoloisoquinoline products can be accessed directly from C1‐unfunctionalized 2‐aryl‐1,2,3,4‐tetrahydroisoquinolines by extending the one‐pot protocol with a foregoing photocatalytic cross‐dehydrogenative coupling reaction, resulting in a quadruple cascade transformation. 相似文献
108.
Henri de Maissin Philipp R. Groß Obaid Mohiuddin Dr. Moritz Weigt Luca Nagel Marvin Herzog Zirun Wang Robert Willing Dr. Wilfried Reichardt Dr. Martin Pichotka Dr. Lisa Heß Prof. Dr. Thomas Reinheckel Prof. Dr. Henning J. Jessen Prof. Dr. Robert Zeiser Prof. Dr. Michael Bock Prof. Dominik von Elverfeldt Prof. Dr. Maxim Zaitsev Dr. Sergey Korchak Dr. Stefan Glöggler Prof. Dr. Jan-Bernd Hövener Prof. Dr. Eduard Y. Chekmenev Prof. Dr. Franz Schilling Dr. Stephan Knecht Dr. Andreas B. Schmidt 《Angewandte Chemie (International ed. in English)》2023,62(36):e202306654
109.
Wen Zhang Jing Jiang Chunhua Qin Lisa M. Pérez Alan R. Parrish Stephen H. Safe 《Supramolecular chemistry》2013,25(7-8):607-616
Three criteria are evaluated to assess the potential of a dendrimer based on triazines, 1, for use as a vehicle for drug delivery. These criteria are: (1) its ability to solubilize small hydrophobic guests as measured spectrophotometrically; (2) its ability to deliver a drug in vitro as evaluated using a gene reporter assay; and (3) its in vivo toxicity in mice as determined by autopsy and screens of liver and kidney function. Vehicle 1 solubilizes pyrene to a similar extent to dendrimers based on poly(arylether)s, 4, encapsulating approximately 0.2 molecules of pyrene per dendrimer. This activity is approximately 10-fold greater than that of the more polar poly(propyleneimine) and poly(amidoamine) dendrimers, 2 and 3. Gas-phase computational models reveal that both 1 and 4 have cores that are accessible to solvent, suggesting that these dendrimers can occupy much greater volumes than 2 and 3 whose cores are confined toward the interior of the structure. Electrostatic potential maps can be used to rationalize differences in solubilization between 1 and 4. Precipitation results from mixing cationic 1 with the anionic indomethacin, but not with methotrexate, suggesting that the composition of the drug may dictate the scope of delivery applications. Dendrimer 1 solubilizes 10-hydroxycamptothecin and a novel bisindolemethane; approximately four and five molecules of drug per dendrimer are solubilized, respectively. In cell-culture experiments using a luciferase reporter gene assay, the dendrimer:bisindolemethane conjugate shows comparable activity to the bisindolemethane delivered in aqueous DMSO, suggesting that the dendrimer does not preclude delivery of the molecule to an intracellular target. Preliminary toxicology studies of 1 in mice show that this molecule has no adverse toxicity to the kidneys or the liver in single doses delivered intraperitoneally up to 10?mg/kg. 相似文献
110.