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181.
Monika Moszner Anna M Trzeciak Józef J Zió?kowski 《Journal of molecular catalysis. A, Chemical》1998,130(3):351-248
Rhodium(II) complexes with dioximes [Rh(Hdmg)2(PPh3)]2 [I] (Hdmg=monoanion of dimethylglyoxime) and [Rh(Hdmg)(ClZndmg)(PPh3)]2 [II] catalyse hydroformylation and hydrogenation reactions of 1-hexene at 1 MPa CO/H2 and 0.5 MPa H2 at 353 K, respectively. Hydroformylation with complex [I] produces 94% of aldehydes (n/iso=2.2) and 6% 2-hexene whereas the second catalyst [II] gives ca. 40% of aldehydes (n/iso=2.1) and 60% of 2-hexene. Corresponding Rh(III) complexes are inactive in hydroformylation except of RhH(Hdmg)2(PPh3) [III], which shows activity similar to [I]. Complexes [Rh(Hdmg)2(PPh3)]2 [I], [Rh(Hdmg)(ClZndmg)(PPh3)]2 [II], RhH(Hdmg)2(PPh3) [III] and [Rh(Hdmg)2(PPh3)2]ClO4 [V] catalyse 1-hexene hydrogenation with an average TON ca. 18 cycles/mol [Rh]×min. Complex [II] has also been found to catalyse hydrogenation of cyclohexene, 1,3-cyclohexadiene and styrene. 相似文献
182.
Summary Nickel(II) xanthates react with amines to form nickel(II) dithiocarbamates and thiourethanes, both products of nucleophilic substitution at the sp2 carbon atom. If the reaction is conducted under carbon monoxide the nickel and sulphur-containing byproduct of thiourethane formation is transformed partly into Ni(CO)4. 相似文献
183.
Natalia V. Loginova Tat’yana V. Koval’chuk Rimma A. Zheldakova Anna A. Chernyavskaya Nikolai P. Osipovich Gennady K. Glushonok Henry I. Polozov Victor L. Sorokin Oleg I. Shadyro 《Central European Journal of Chemistry》2006,4(3):440-457
Cu (II) complexes with the sterically hindered diphenol derivatives 3,5-di(tert-butyl)-1,2-benzenediol (I), 4,6-di(tert-butyl)-1,2,3-benzenetriol (II) and the sulfur-containing 4,6-di(tert-butyl)-3-(2-hydroxyethylsulfanyl)-1,2-benzenediol (III) and 2-[4,6-di(tert-butyl)-2,3-dihydroxyphenylsulfanyl]acetic acid (IV) have been synthesized and characterized by elemental analysis, TG/DTA, FT-IR, ESR, XPS, XPD and conductivity measurements.
Compounds I–III can coordinate in their singly deprotonated forms and act as bidentate ligands. These compounds yield Cu (II) complexes of the stoichiometry Cu(L)2, which have square planar geometry (g| > g⊥ > ge). Unlike them, compound IV behaves as a terdentate ligand, and its complex Cu(LIV)2 has distorted octahedral geometry. According to ESR data, only the Cu(LII)2 complex contains a very small amount of phenoxyl radicals. Antimicrobial activities of these ligands and their respective
Cu (II) complexes have been determined with respect to Gram-positive and Gram-negative bacteria, as well as on yeasts. Their
phytotoxic properties against Chlorella vulgaris 157 were also examined. 相似文献
184.
Montserrat Ferrer Anna Juli Roser Reina Oriol Rossell Miquel Seco Dominique de Montauzon 《Journal of organometallic chemistry》1998,560(1-2)
Treatment of [(ClAu)2(diphosphine)] {diphosphine=bis(diphenylphosphino)methane (dppm), bis(diphenylphosphino)isopropane (dppip), 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp)} with two equivalents of the anion [Fe2(μ-CO)(CO)6(μ-PPh2)]− in the presence of TlBF4 gives the new heterometallic diclusters [{Fe2(μ-CO)(CO)6(μ-PPh2)Au}2(diphosphine)] that have been isolated and characterized. Their 31P-NMR spectra show different patterns as a function of the diphosphine ligand. The electrochemical behavior of these compounds has been investigated and compared with that of the mono- [Fe2(μ-CO)(CO)6(μ-PPh2)(μ-AuPPh3)] and tricluster [{Fe2(μ-CO)(CO)6(μ-PPh2)Au}3(triphos)] derivatives. 相似文献
185.
Vincenza Bruno Anna Castaldo Roberto Centore Augusto Sirigu Felice Sarcinelli Mauro Casalboni Roberto Pizzoferrato 《Journal of polymer science. Part A, Polymer chemistry》2002,40(10):1468-1475
The synthesis of the new chromophores 2‐{4‐[4‐(N,N‐dihydroxyethylamino)‐phenylazo]‐phenyl}‐6‐nitrobenzoxazole ( 1 ) and 4‐[4‐(N,N‐dihydroxyethylamino)phenylazo]‐benzoic acid ( 2 ) is described. Three homopolymers obtained by the polycondensation of 1 with propyloxy‐terephthalic acid and 1 and 2 with 2,4‐tolylenediisocianate as well as two copolymers obtained by polycondensation of appropriate mixtures of chromophores 1 and 2 with 2,4‐tolylene‐diisocianate were prepared and characterized. All as‐prepared polymers but one (homopolyurethane of 1 ) were amorphous and exhibited good optical clarity, good thermal stability above the glass transition, and solubility in organic solvents. The second‐order nonlinear optical behavior of the amorphous polymers was investigated on spin‐coated corona‐poled films through second harmonic generation (SHG) experiments at 1064 nm. At this wavelength, resonance‐enhanced values of the SHG coefficient d33 were found in the range between 6 and 34 pm/V where higher values were observed for polymers with a higher molar content of 1 . © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1468–1475, 2002 相似文献
186.
Monika Tarnowska Adam Liwo Mark D. Shenderovich Inta Liepiņa Alexander A. Golbraikh Zbigniew Grzonka Anna Tempczyk 《Journal of computer-aided molecular design》1993,7(6):699-719
Summary The effect of the substitution in position 1 on the low-energy conformations of the oxytocin/vasopressin 20-membered ring was investigated by means of molecular mechanics. Three representative substitutions were considered: -mercapto-,-dimethyl)propionic acid (Dmp), (-mercapto-,-cyclopentamethylene)propionic acid (Cpp), both forming strong antagonists, and (,-dimethyl--mercapto)propionic acid (-Dmp), forming analogs of strongly reduced biological activity, with the -mercaptopropionic (Mpa) residue taken as reference. Both ECEPP/2 (rigid valence geometry) and AMBER (flexible valence geometry) force fields were employed in the calculations. Three basic types of backbone conformations were taken into account which are distinguished by the type of -turn at residues 3 and 4: 1/III, II, and I/III, all types containing one or two intra-annular hydrogen bonds. The allowed (ring-closed) disulfide-bridge conformations were searched by an algorithm formulated in terms of scanning the disulfide-bridge torsional angle C-S-S-C. The ECEPP/2 and AMBER energies of the obtained conformations were found to be in reasonable agreement. Two of the low-energy conformers of the [Mpa1]-compound agreed very well with the cyclic part of the two conformers found in the crystal structure of [Mpa1]-oxytocin. An analysis of the effect of -substitution on relative energies showed that the conformations with the N-C-CH2-CH2 (1) and C-CH2-CH2-S (1) angles of the first residue around (–100°, 60°) and (100°, –60°) are not affected; this in most cases implies a left-handed disulfide bridge. In the case of -substitution the allowed values of 1 are close to ± 60°. This requirement, being in contradiction to the one concerning -substitution, could explain the very low biological activity of the -substituted analogs. The conformational preferences of substituted compounds can largely be explained by the analysis of local interactions within the first residue. Based on the selection of the conformations which are low in energy for both the reference and -substituted compounds, two distinct types of possible binding conformations were proposed, the first one being similar to the crystal conformer with a left-handed disulfide bridge, the second one having a right-handed bridge, but a geometry different from that of the crystal conformer with the right-handed bridge. The first type of disulfide-bridge arrangement is equally favorable for both I/III and II types of backbone structure, while the second one is allowed only for the II type of backbone. No conformation of the I/III type has a low enough energy to be considered as a possible binding conformation for all of the active compounds studied in this work. 相似文献
187.
Napper AM Head NJ Oliver AM Shephard MJ Paddon-Row MN Read I Waldeck DH 《Journal of the American Chemical Society》2002,124(34):10171-10181
A systematic determination of electronic coupling matrix elements in U-shaped molecules is demonstrated. The unique architecture of these systems allows for the determination of the electronic coupling through a pendant molecular moiety that resides between the donor and acceptor groups; this moiety quantifies the efficiency of electron tunneling through nonbonded contacts. Experimental electron-transfer rate constants and reaction free energies are used to calibrate a molecular-based model that describes the solvation energy. This approach makes it possible to experimentally determine electronic couplings and compare them with computational values. 相似文献
188.
Münzer DF Meinhold P Peters MW Feichtenhofer S Griengl H Arnold FH Glieder A de Raadt A 《Chemical communications (Cambridge, England)》2005,(20):2597-2599
Substrate engineered, achiral carboxylic acid derivative was biohydroxylated with various mutants of cytochrome P450 BM-3 to give two out of the four possible diastereoisomers in high de and ee. The BM-3 mutants exhibit up to 9200 total turnovers for hydroxylation of the engineered substrate, which without the protecting group is not transformed by this enzyme. 相似文献
189.
Dariusz Matosiuk Kalevi Pihlaja Vladimir V. Ovcharenko Izabela Dybaa Anna E. Kozio Maria Gdaniec Halina Szumio Zbigniew Karczmarzyk 《Journal of heterocyclic chemistry》2003,40(1):93-99
The pseudo‐Michael reaction of 1‐aryl‐2‐aminoimidazolines‐2 with diethyl ethoxymethylenemalonate (DEEM) was investigated. Extensive structural studies were performed to confirm the reaction course. For derivatives with N1 aromatic substituents, it was found that the reaction course was temperature dependent. When the reaction temperature was held at ?10 °C only the formation of 1‐aryl‐7(1H)‐oxo‐2,3‐dihydroimi‐dazo[1,2‐a]pyrimidine‐6‐carboxylates ( 4 ) was observed in contrast to earlier suggestions. Under the room temperature conditions, the same reaction yielded mixtures, with varying ratio, of isomeric 1‐aryl‐7(1H)‐oxo‐ ( 4a‐4f ) and 1‐aryl‐5(1H)‐oxo‐2,3‐dihydroimidazo[1,2‐a]pyrimidine‐6‐carboxylates ( 5a‐5f ). The molecular structure of selected isomers, 4b and 5c , was confirmed by X‐ray crystallography. Frontal chro‐matography with delivery from the edge was applied for the separation of the isomeric esters. The isomer ratio of the reaction products depended on the character of the substituents on the phenyl ring. The 1‐aryl‐7(1H)‐oxo‐carboxylates ( 4a‐4f ) were preferably when the phenyl ring contained H, 4‐CH3, 4‐OCH3 and 3,4‐Cl2 substituents. Chloro substitution at either position 3 or 4 in the phenyl ring favored the formation of isomers 5a‐5f . The isomer ratios were confirmed both by 1H NMR and chromatography. The reaction of the respective hydrobromides of 1‐aryl‐2‐aminoimidazoline‐2 with DEEM, in the presence of triethylamine, gave selectively 5(1H)‐oxo‐esters ( 5a‐5f ). 相似文献
190.
Six new divalent lanthanide complexes using triglyme (trigly) and tetraglyme (tetgly) as achiral ligands have been prepared, using a facile synthetic method, in search for enantioselective solid-state reagents. The crystal structures of cis-[SmI2(trigly)thf] (1), trans-[YbI2(trigly)thf] (2), trans-[SmI2(trigly)dme] (3), trans-[YbI2(tetgly)] (4), trans-[EuI2(tetgly)thf] (5), and [Sm(tetgly)2][SmI3(tetgly)]I (6) have been determined. All complexes, except 5, are chiral. The 10-coordinate cation in 6 displays a helical chirality since the two tetraglyme ligands are wrapped around the samarium ion. Since trans-[YbI2(tetgly)] (4), which has a chiral arrangement of terminal methyl groups, crystallizes as a conglomerate, preferential crystallization and consequent enantioselective reduction of acetophenone was attempted, but resulted in racemic products, possibly on account of racemic twinning in 4. 相似文献