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181.
We report the thermodynamics of binding of d-galactose and deoxy derivatives thereof to the arabinose binding protein (ABP). The "intrinsic" (solute-solute) free energy of binding DeltaG degrees (int) at 308 K for the 1-, 2-, 3-, and 6-hydroxyl groups of galactose is remarkably constant (approximately -30 kJ/mol), despite the fact that each hydroxyl group subtends different numbers of hydrogen bonds in the complex. The substantially unfavorable enthalpy of binding (approximately 30 kJ/mol) of 1-deoxygalactose, 2-deoxygalactose, and 3-deoxygalactose in comparison with galactose, cannot be readily accounted for by differences in solvation, suggesting that solute-solute hydrogen bonds are enthalpically significantly more favorable than solute-solvent hydrogen bonds. In contrast, the substantially higher affinity for 2-deoxygalactose in comparison with either 1-deoxygalactose or 3-deoxygalactose derives from differences in the solvation free energies of the free ligands. 相似文献
182.
We introduce a method for ungapped local multiple alignment (ULMA) in a given set of amino acid or nucleotide sequences. This method explores two search spaces using a linked optimization strategy. The first search space M consists of all possible words of a given length W, defined on the residue alphabet. An evolutionary algorithm searches this space globally. The second search space P consists of all possible ULMAs in the sequence set, each ULMA being represented by a position vector defining exactly one subsequence of length W per sequence. This search space is sampled with hill-climbing processes. The search of both spaces are coupled by projecting high scoring results from the global evolutionary search of M onto P. The hill-climbing processes then refine the optimization by local search, using the relative entropy between the ULMA and background residue frequencies as an objective function. We demonstrate some advantages of our strategy by analyzing difficult natural amino acid sequences and artificial datasets. A web interface is available at 相似文献
183.
Oscar Javier Hernandez Nir Nevo Dinur Chen Ji Sonia Bacca Nir Barnea 《Hyperfine Interactions》2016,237(1):158
We present calculations of the nuclear structure corrections to the Lamb shift in light muonic atoms, using state-of-the-art nuclear potentials. We outline updated results on finite nucleon size contributions. 相似文献
184.
185.
A subset S of a topological group G is called bounded if, for every neighborhood U of the identity of G, there exists a finite subset F such that S ⊆ FU, S ⊆ UF. The family of all bounded subsets of G determines two structures on G, namely the left and right balleans B
l
(G) and B
r
(G), which are counterparts of the left and right uniformities of G. We study the relationships between the uniform and ballean structures on G, describe all topological groups admitting a metric compatible both with uniform and ballean structures, and construct a group
analogue of Higson’s compactification of a proper metric space. 相似文献
186.
187.
A phtalimido group can be readily introduced at the 5″‐position of N‐Boc ribostamycin 6 under Mitsunobu reaction conditions. However, in the case of N‐Boc neomycin B 4 a competitive bicyclization process occurred within the ring IV of the antibiotic, which led to compound 8, whose structure was fully elucidated by NMR spectroscopic methods. Accordingly, particular care must be exercised to achieve this chemical modification of the four‐ring antibiotic. 相似文献
188.
A. Farran E. Figuerola J. de Pablo S. Hernandez 《International journal of environmental analytical chemistry》2013,93(3-4):245-256
Abstract The treatment of waste water containing three organophosphorous pesticides: diazinon, azinphos-methyl and fenthion by using continuous flow methodologies coupled on line with HPLC-UV detection is presented. Two continuous flow techniques: completely continuous flow and flow injection, both combined with two separation methods: liquid-liquid extraction and adsorption resins are discussed, as well as the influence of physical and chemical parameters on the analysis. Adsorption resins seem to be more suitalbe for the treatment of waste water at low pesticide concentraions while liquid-liquid extraction is more selective. 相似文献
189.
Romain Lafay Dr. German Montes‐Hernandez Dr. Emilie Janots Dr. Rodica Chiriac Nathaniel Findling François Toche 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(17):5417-5424
Herein, we report new insights into the nucleation and growth processes of chrysotile nanotubes by using batch and semi‐continuous experiments. For the synthesis of this highly carcinogenic material, the influences of temperature (90, 200, and 300 °C), Si/Mg molar ratio, and reaction time were investigated. From the semi‐continuous experiments (i.e., sampling of the reacting suspension over time) and solid‐state characterization of the collected samples by XRPD, TGA, FTIR spectroscopy, and FESEM, three main reaction steps were identified for chrysotile nucleation and growth at 300 °C: 1) formation of the proto‐serpentine precursor within the first 2 h of the reaction, accompanied by the formation of brucite and residual silica gel; 2) spontaneous nucleation and growth of chrysotile between about 3 and 8 h reaction time, through a progressive dissolution of the proto‐serpentine, brucite, and residual silica gel; and 3) Ostwald ripening growth of chrysotile from 8 to 30 h reaction time, as attested to by BET and FESEM measurements. Complementary results from batch experiments confirmed a significant influence of the reaction temperature on the kinetics of chrysotile formation. However, FESEM observations revealed some formation of chrysotile nanotubes at low temperatures (90 °C) after 14 days of reaction. Finally, doubling the Si/Mg molar ratio promoted the precipitation of pure smectite (stevensite‐type) under the same P (8.2 MPa)/T (300 °C)/pH (13.5) conditions. 相似文献
190.
Hernandez David Alejandro Rodriguez-Zavala Jaime Gustavo Tenorio Francisco J. 《Structural chemistry》2020,31(1):359-369
Structural Chemistry - Quantum chemistry calculations were performed to compare the reactivity indexes obtained within the conceptual density functional theory of phenolic and allyl-phenolic... 相似文献