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41.
Hossein Vahabi Laurent Ferry Claire Longuet Rodolphe Sonnier Claire Negrell-Guirao Ghislain David José-Marie Lopez-Cuesta 《European Polymer Journal》2012,48(3):604-612
The influence of phosphonated groups on thermal degradation and flammability has been investigated in the case of two chemically modified PMMA. Thermogravimetric analysis as well as pyrolysis combustion flow calorimetry have been used to define the efficiency of phosphorus in both condensed and vapor phases. A theoretical study was also performed to determine the contribution of phosphonated groups to the effective heat of combustion, residue content and heat release capacity. Empirical and theoretical approaches agreed to highlight that PMMA modified with monophosphonated comonomer is more efficient in both condensed and vapor phases in terms of flammability and char formation. These results were attributed to the ability of phosphonate groups to interact with ester groups and also to the weakness of the P–C–N bonds. Moreover, this study proposes a method for designing the chemical environment of phosphonate group in polymers to achieve better flame retardancy. 相似文献
42.
Ismaili L Truong TT André C Thomassin M Mozer JL Robert JF Xicluna A Refouvelet B Millet J Nicod L Guillaume YC 《Journal of AOAC International》2003,86(2):222-228
The mechanism of the binding of D,L dansyl amino acids to teicoplanin was investigated. Na+ was used as an indicator of the interactions between the solutes and teicoplanin. The number (n) of sodium ions, Na+, excluded from the solute-teicoplanin interface when analyte transfer occurred was determined. A thermodynamic study and enthalpy-entropy compensation were performed to further explore the interaction mechanism. From these results, it was shown that teicoplanin was balanced between 2 conformational states characterized by distinct enantioselective properties. This approach indicates that liquid chromatography (LC) is a useful tool to extract physicochemical and molecular information from retention data. Thus, LC can be used as a complementary technique with the conventional techniques of molecular interaction analysis. 相似文献
43.
A novel synthetic approach to diversely functionalized indoles is described. Boc-protected ortho-aminostyrenes undergo an alkyllithium addition reaction, thereby generating a lithiated intermediate, which upon reaction with specific electrophiles sets up a cascade reaction process between the reacted electrophile and ortho-amino substituent, facilitating an in situ ring closure, followed by dehydration, to generate an indole ring system. This methodology is demonstrated by the synthesis of a range of 3,5-, 1,3,5-, and 2,3,5-substituted indoles. 相似文献
44.
Brian W. Skelton A. Fiona Waters Claire R. Whitaker Allan H. White 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(11):m435-m438
Both of the title compounds, catena‐poly[[[tetraaquamagnesium(I)]‐μ‐4,4′‐bipyridine‐κ2N:N′] diiodide bis(4,4′‐bipyridine) solvate], {[Mg(C10H8N2)(H2O)4]I2·2C10H8N2}n, (I), and catena‐poly[[[μ‐4,4′‐bipyridine‐bis[diiodobis(propan‐1‐ol)strontium(I)]]‐di‐μ‐4,4′‐bipyridine‐κ4N:N′] bis(4,4′‐bipyridine) solvate], {[Sr2I4(C10H8N2)3(C3H8O)4]·2C10H8N2}n, (II), are one‐dimensional polymers which are single‐ and double‐stranded, respectively, the metal atoms being linked by the 4,4′‐bipyridine moieties. The Mg complex, (I), is [cis‐{(H2O)4Mg(N‐4,4′‐bipyridine‐N′)(2/2)}](∞|∞)I2·4,4′‐bipyridine and Mg has a six‐coordinate quasi‐octahedral coordination environment. The Sr complex, (II), is isomorphous with its previously defined Ba counterpart [Kepert, Waters & White (1996). Aust. J. Chem. 49 , 117–135], being [(propan‐1‐ol)2I2Sr(N‐4,4′‐bipyridine‐N′)(3/2)](∞|∞)·4,4′‐bipyridine, with the I atoms trans‐axial in a seven‐coordinate pentagonal–bipyramidal Sr environment. 相似文献
45.
The ionic Diels-Alder reaction, whereby an alpha,beta-unsaturated acetal in combination with a Lewis or Bronsted acid forms an equilibrium concentration of an activated dienophile, has been developed to provide an enantioselective synthesis of cis-decalins. Cyclohex-2-enone type chiral acetals of (2R,3R)-butane-2,3-diol have been screened against Lewis and Br?nsted acids with a variety of dienes and are efficient for the synthesis of a limited subset of cis-decalin structures. Diastereoselectivities of 73% and 82% have been found for the asymmetric ionic Diels-Alder reaction between the chiral acetal derivatives of cyclohex-2-enone (6) and 2-methylcyclohex-2-enone (18) with 2,3-dimethyl-1,3-butadiene (7). Terminal substituents on the diene partner in general render the system unreactive. However a synthetically useful cis-decalin 31, derived from the reaction of 2-methylcyclohex-2-enone and Z-3-t-butyldimethyl-silyloxypenta-1,3-diene has been prepared in enantiomerically pure form in 74% isolated yield using this asymmetric ionic Diels-Alder protocol. 相似文献
46.
[reaction: see text] Pd nanoparticles (approximately 2 nm in size) microencapsulated in polyurea is an efficient and recyclable catalyst for reductive ring-opening hydrogenolysis of epoxides, using either HCOOH/Et(3)N or H(2) as a hydrogen donor. 相似文献
47.
Tammy J. Siciliano Michael C. Deblock Semih Durmus Claire A. Tessier 《Journal of organometallic chemistry》2011,696(5):1066-8615
Bis(1,3-dimethylimidazol-2-ylidene)silver(I) nitrate and bis(4,5-dichloro-1,3-dimethylimidazol-2-ylidene)silver(I) nitrate were prepared by reacting the corresponding imidazolium nitrate salts with silver oxide. Bis(1,3-dimethylimidazol-2-ylidene)gold(I) nitrate and bis(4,5-dichloro-1,3-dimethylimidazol-2-ylidene)gold(I) nitrate salts were prepared via transmetallation of their silver precursors with chloro dimethylsulfide gold. The anticancer properties were determined using NCI-H460 lung cancer cells. Efficacy was established by comparison of the gold and silver compounds with cisplatin. 相似文献
48.
Folliet N Roiland C Bégu S Aubert A Mineva T Goursot A Selvaraj K Duma L Tielens F Mauri F Laurent G Bonhomme C Gervais C Babonneau F Azaïs T 《Journal of the American Chemical Society》2011,133(42):16815-16827
In the context of nanomedicine, liposils (liposomes and silica) have a strong potential for drug storage and release schemes: such materials combine the intrinsic properties of liposome (encapsulation) and silica (increased rigidity, protective coating, pH degradability). In this work, an original approach combining solid state NMR, molecular dynamics, first principles geometry optimization, and NMR parameters calculation allows the building of a precise representation of the organic/inorganic interface in liposils. {(1)H-(29)Si}(1)H and {(1)H-(31)P}(1)H Double Cross-Polarization (CP) MAS NMR experiments were implemented in order to explore the proton chemical environments around the silica and the phospholipids, respectively. Using VASP (Vienna Ab Initio Simulation Package), DFT calculations including molecular dynamics, and geometry optimization lead to the determination of energetically favorable configurations of a DPPC (dipalmitoylphosphatidylcholine) headgroup adsorbed onto a hydroxylated silica surface that corresponds to a realistic model of an amorphous silica slab. These data combined with first principles NMR parameters calculations by GIPAW (Gauge Included Projected Augmented Wave) show that the phosphate moieties are not directly interacting with silanols. The stabilization of the interface is achieved through the presence of water molecules located in-between the head groups of the phospholipids and the silica surface forming an interfacial H-bonded water layer. A detailed study of the (31)P chemical shift anisotropy (CSA) parameters allows us to interpret the local dynamics of DPPC in liposils. Finally, the VASP/solid state NMR/GIPAW combined approach can be extended to a large variety of organic-inorganic hybrid interfaces. 相似文献
49.
Guillaume Erbland Dr. Seifallah Abid Yohan Gisbert Nathalie Saffon-Merceron Yuichiro Hashimoto Leonardo Andreoni Théo Guérin Dr. Claire Kammerer Prof. Dr. Gwénaël Rapenne 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(71):16328-16339
The design and synthesis of two families of molecular-gear prototypes is reported, with the aim of assembling them into trains of gears on a surface and ultimately achieving controlled intermolecular gearing motion. These piano-stool ruthenium complexes incorporate a hydrotris(indazolyl)borate moiety as tripodal rotation axle and a pentaarylcyclopentadienyl ligand as star-shaped cogwheel, equipped with five teeth ranging from pseudo-1D aryl groups to large planar 2D paddles. A divergent synthetic approach was followed, starting from a pentakis(p-bromophenyl)cyclopentadienyl ruthenium(II) complex as key precursor or from its iodinated counterpart, obtained by copper-catalyzed aromatic Br/I exchange. Subsequent fivefold cross-coupling reactions with various partners allowed high structural diversity to be reached and yielded molecular-gear prototypes with aryl-, carbazole-, BODIPY- and porphyrin-derived teeth of increasing size and length. 相似文献
50.