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241.
Emma Petiot Frantz Fournier Cécile Gény Hervé Pinton Annie Marc 《Applied biochemistry and biotechnology》2010,160(6):1600-1615
The paper proposes a rapid screening method for a first step improvement of an animal component-free medium dedicated to the growth of the anchorage-dependent Vero cell line. A new, rapid, and non-invasive technique is presented to specifically monitor cultures of adherent cells in 96-well plates. The operating conditions of an image analyzer are adapted to take into account the decrease of cell size when the attached cell density increases. An experimental design is carried out to assess the influence of ten component groups in the original medium. Two groups including protein extracts, growth factor, insulin, glucose, and pyruvate show significant positive effects. The groups with vitamins and molecules related to nitrogenous bases display a less pronounced influence. The mixture of amino acids, B1 vitamin, magnesium sulfate, and sodium phosphate as well as the couple sodium citrate and ferric chloride lead to a downward trend. The screening results are proved to be scalable in stirred cultures with cells on microcarriers. An improved serum-free medium, with some component groups being removed or added, can be rapidly formulated to reach respectively similar or 1.6 times higher cell density than in the original medium. The results from this global approach could be helpful to further focus experiments on identified medium components. 相似文献
242.
Abbott AP Nandhra S Postlethwaite S Smith EL Ryder KS 《Physical chemistry chemical physics : PCCP》2007,9(28):3735-3743
In this paper, we describe the first example of a sustained galvanic coating deposited on a surface from a non-aqueous liquid. We present the surface characterization of electroless silver deposits on copper substrates from a solution of Ag(+) ions in an ionic liquid based on a choline chloride (ChCl) eutectic. Through a study of these deposits and the mechanism of formation using acoustic impedance spectroscopy (QCM), probe microscopy (AFM) and electron microscopy (SEM/EDX), we demonstrate that sustained growth of the silver deposit is facilitated by the porous nature of the silver. This is in contrast to the dip-coating reaction of silver ions in aqueous media, where the reaction stops when surface coverage is reached. Electroless silver deposits of up to several microns have been obtained by dip coating in ionic liquids without the use of catalysts of strong inorganic acids. 相似文献
243.
Emma E. Smith Leonie A. Cooke Maighréad McCourt James H.R. Tucker 《Tetrahedron letters》2007,48(37):6569-6572
Directed Michaelis-Arbuzov reactions of support-bound internucleotide O-benzyl- or O-methyl-phosphite triesters with meta-phenylazobenzylamine or alkane-/glycol-linked α,ω-diamines were effected in the presence of iodine. The corresponding tritylated phosphoramidate-linked 11-mers were fully deprotected and released from the support under standard conditions and the fast- and slow-diastereoisomers of both the E- and the Z-meta-phenylazobenzyl-appended oligomers were readily resolved by RP-HPLC. The primary amine-functionalised oligonucleotides were either purified, detritylated and then finally treated with N-hydroxysuccinimidyl carboxylic acid ester derivatives of photoswitchable moieties (Route A) or first derivatised and then subsequently purified and detritylated (Route B). This latter route enabled resolution of fast- and slow-isomers of the trityl-on oligomers bearing novel photoswitchable azopyridine or 9-alkoxyanthracene moieties using RP-HPLC, following which the pure diastereoisomers were detritylated and characterised by MALDI-MS. 相似文献
244.
Cavero E Uriel S Romero P Serrano JL Giménez R 《Journal of the American Chemical Society》2007,129(37):11608-11618
Novel metallomesogens with luminescent properties and liquid crystalline behavior at room temperature have been achieved by the preparation of zinc complexes with polycatenar pyrazole and bis(pyrazolyl)methane ligands. Their molecular structures do not have a conventional shape in that they are far from the typical rod-like and flat disc-like geometries of common liquid crystals. They consist of a nonplanar nucleus due to the methylene spacer and/or the coordination to the tetrahedral center, as confirmed by single crystal analysis of the cores. The different numbers and positions of side chains in the pyrazole ligand enabled us to access lamellar and columnar mesophases and, of particular interest, to obtain columnar arrangements at room temperature. Supramolecular models for the organization of the molecules in the mesophases are proposed on the basis of the small-angle XRD diffractograms. The zinc complexes display luminescence in the near UV-blue region with large Stokes shifts. An interplay between non-conventional molecular shapes (due to the tetrahedral core) and the supramolecular mesomorphic order (due to the ligand design) led to materials that interestingly embody two rather opposite properties, a columnar self-organizational ability and luminescence with weak intermolecular interactions. 相似文献
245.
246.
García-López J Peralta-Pérez E Forcén-Acebal A García-Granda S López-Ortiz F 《Chemical communications (Cambridge, England)》2003,(7):856-857
The first examples of the PN-directed dilithiation of (N-methoxycarbonyl)phosphazenes in the C(alpha) and C(ortho) to the phosphorus, and the use of these dianions in the formation of tri- and tetra-substituted olefins through stereospecific thermolysis of a new type of isolable bicyclic 1,2-oxaphosphetanes are described. 相似文献
247.
Costa-Balogh FO Aberg C Sousa JJ Sparr E 《Langmuir : the ACS journal of surfaces and colloids》2005,21(23):10307-10310
In this paper, we demonstrate, for the first time, how an external osmotic gradient can be used to regulate diffusion of solutes across a lipid membrane. We present experimental and theoretical studies of the transport of different solutes across a monoolein membrane in the presence of an external osmotic gradient. The osmotic gradient introduces phase transformations in the membrane, and it causes nonlinear transport behavior. The external gradient can thus act as a kind of switch for diffusive transport in the skin and in controlled release drug formulations. 相似文献
248.
Aggarwal VK Alonso E Bae I Hynd G Lydon KM Palmer MJ Patel M Porcelloni M Richardson J Stenson RA Studley JR Vasse JL Winn CL 《Journal of the American Chemical Society》2003,125(36):10926-10940
A variety of metalated tosylhydrazone salts derived from benzaldehyde have been prepared and were reacted with benzaldehyde in the presence of tetrahydrothiophene (THT) (20 mol %) and Rh(2)(OAc)(4) (1 mol %) to give stilbene oxide. Of the lithium, sodium, and potassium salts tested, the sodium salt was found to give the highest yield and selectivity. This study was extended to a wide variety of aromatic, heteroaromatic, aliphatic, alpha,beta-unsaturated, and acetylenic aldehydes and to ketones. On the whole, high yields of epoxides with moderate to very high diastereoselectivities were observed. A broad range of tosylhydrazone salts derived from aromatic, heteroaromatic, and alpha,beta-unsaturated aldehydes was also examined using the same protocol in reactions with benzaldehyde, and again, good yields and high diastereoselectivities were observed in most cases. Thus, a general process for the in situ generation of diazo compounds from tosylhydrazone sodium salts has been established and applied in sulfur-ylide mediated epoxidation reactions. The chiral, camphor-derived, [2.2.1] bicyclic sulfide 7 was employed (at 5-20 mol % loading) to render the above processes asymmetric with a range of carbonyl compounds and tosylhydrazone sodium salts. Benzaldehyde tosylhydrazone sodium salt gave enantioselectivities of 91 +/- 3% ee and high levels of diastereoselectivity with a range of aldehydes. However, tosylhydrazone salts derived from a range of carbonyl compounds gave more variable selectivities. Although those salts derived from electron-rich or neutral aldehydes gave high enantioselectivities, those derived from electron-deficient or hindered aromatic aldehydes gave somewhat reduced enantioselectivities. Using alpha,beta-unsaturated hydrazones, chiral sulfide 7 gave epoxides with high diastereoselectivities, but only moderate yields were achieved (12-56%) with varying degrees of enantioselectivity. A study of solvent effects showed that, while the impact on enantioselectivity was small, the efficiency of diazo compound generation was influenced, and CH(3)CN and 1,4-dioxane emerged as the optimum solvents. A general rationalization of the factors that influence both relative and absolute stereochemistry for all of the different substrates is provided. Reversibility in formation of the betaine intermediate is an important issue in the control of diastereoselectivity. Hence, where low diastereocontrol was observed, the results have been rationalized in terms of the factors that contribute to the reduced reversion of the syn betaine back to the original starting materials. The enantioselectivity is governed by ylide conformation, facial selectivity in the ylide reaction, and, again, the degree of reversibility in betaine formation. From experimental evidence and calculations, it has been shown that sulfide 7 gives almost complete control of facial selectivity, and, hence, it is the ylide conformation and degree of reversibility that are responsible for the enantioselectivity observed. A simple test has been developed to ascertain whether the reduced enantioselectivity observed in particular cases is due to poor control in ylide conformation or due to partial reversibility in the formation of the betaine. 相似文献
249.
Claudio Tonelli Antonella Di Meo Emma Barchiesi 《Journal of polymer science. Part A, Polymer chemistry》2002,40(23):4266-4280
A series of perfluoropolyether bis‐carboxylic esters was synthesized and their hydrolytic stability investigated. Their formula is ROOCCF2O(CF2CF2O)p(CF2O)qCF2COOR, where p/q = 1.07 and p + q = 2.94. The alkyl group, R, varied both in terms of steric hindrance and electron‐withdrawing ability. Kinetic and thermodynamic data were obtained under homogeneous conditions and compared to a fully hydrogenated ester having a closely related structure CH3(CH2)3OOCCH2O(CH2CH2O)nCH2COO(CH2)3CH3, where n? = 10.6. Neutral ester hydrolysis (NEH) conditions were selected with methyl ethyl ketone as a solvent and a 3–4:1 water/ester ratio. The course of the reaction was monitored by 19F NMR or 1H NMR (when R = CH3CH2? ). Results indicated that the hydrolysis of fluorinated esters, with alkyl aliphatic substituents, is governed by steric hindrance of the substituents. Two distinctive kinetic regimes were observed. The first one, at low conversion, was characterized by lower kinetic constants and related to true NEH conditions. The second regime appeared at higher conversion when acidic autocatalysis dictated the reaction behavior. This is the only observed mechanism when esters more sensitive to the hydrolysis are considered. In these cases, polar factors prevail over steric considerations. Finally, all fluorinated esters of the class (I) showed a much higher reactivity than the hydrogenated ester whose hydrolysis took place only in the presence of a strong acidic catalyst. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4266–4280, 2002 相似文献
250.
Gahan LR Grillo VA Hambley TW Hanson GR Hawkins CJ Proudfoot EM Moubaraki B Murray KS Wang D 《Inorganic chemistry》1996,35(4):1039-1044
Reaction of manganese(II) perchlorate hexahydrate with a methanol solution of 1-thia-4,7-diazacyclononane ([9]aneN(2)S) resulted in the isolation of the manganese(II) complex [Mn([9]aneN(2)S)(2)](ClO(4))(2). The X-ray structure of this complex is reported: crystal system orthorhombic, space group Pbam, No. 55, a = 7.937(2) ?,b = 8.811(2) ?, c = 15.531(3) ?, Z = 2, R = 0.0579. The complex is high spin (S = (5)/(2)) with an effective magnetic moment (&mgr;(eff)) 5.82 &mgr;(B) at 298 K and 5.65 &mgr;(B) at 4.2 K. Computer simulation of the Q-band EPR spectrum of [Mn([9]aneN(2)S)(2)](ClO(4))(2) yields g = 1.99 +/- 0.01, |D| = 0.19 +/- 0.005 cm(-)(1), and E/D = 0.04 +/- 0.02. For the analogous hexaamine complex [Mn([9]aneN(3))(2)](ClO(4))(2) ([9]aneN(3) = 1,4,7-triazacyclononane) analysis of the EPR spectra produced the following values: g = 1.98 +/- 0.01, |D| = 0.09 +/- 0.003 cm(-)(1), and E/D = 0.1 +/- 0.01. The spin Hamiltonian parameters for [Mn([9]aneN(2)S)(2)](ClO(4))(2) derived from the EPR spectra produced a good fit to the magnetic susceptibility data. 相似文献