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101.
Ayesha Kausar Sonia ZulfiqarCafer T. Yavuz Muhammad Ilyas Sarwar 《Polymer Degradation and Stability》2011,96(7):1333-1341
A new generation of segmented thermoplastic poly(urethane-thiourea-imide)s (PUTIs) was synthesized via reaction of polyethylene glycol and thiourea-based prepolymer with dianhydride as chain extenders. NCO-terminated prepolymer was synthesized from a new diisocyanate, 3-(3-((4-isocyanatophenyl)carbamoyl)thioureido)phenyl-4-isocyanatophenylcarbamate (IPCT), as a hard segment and PEG forming soft segment. The starting materials and polymers were characterized by conventional methods and physical properties such as solubility, solution viscosity, molecular weight, thermal stability and thermal behavior were studied. PUTIs showed partially crystalline structures. Weight average molecular weights of PUTIs (GPC measurements) were in the range of 1,68,694-1,97,035. Moreover, thermogravimetric analysis indicated that poly(urethane-thiourea-imide)s were fairly stable above 500 °C having T10 of 521-543 °C. Investigation of the results authenticated the approach of introducing thiourea (using IPCT) and imide structure in polyurethanes for the improvement of thermal stability. In comparison to typical polyurethanes, these polymers exhibited better heat resistance, chemical resistance as well as processability. 相似文献
102.
Sonia Fiorilli Dario Caldarola Hao Ma Barbara Onida 《Journal of Sol-Gel Science and Technology》2011,60(3):260-265
Silica spheres with uniform size of 230–250 nm were functionalized with sulfonic groups and bi-functionalized with carboxylic and sulfonic groups via a co-condensation route, by adding the organosilanes (3-(triethoxysilyl)mercaptopropyl and 4-(triethoxysilyl)butyronitrile) to a pre-hydrolized TEOS solution. The conversion of mercapto and cyano groups to, respectively, sulfonic and carboxylic groups was carried out by treating both the samples with nitric acid solution. The presence of alkyl-SO3H and alkyl-COOH species at the silica surface in an approximate molar ratio of 1:1 was assessed by TG and NMR. FT-IR spectroscopy showed that both Brønsted acidic groups are accessible and give proton-transfer reaction to ammonia with the formation of ammonium ion. Sulfonic groups react irreversibly with ammonia at room temperature at variance with carboxylic groups which give a reversible proton-transfer, in agreement with the stronger Brønsted acidity of the former. 相似文献
103.
Sonia Aguado-Ullate Octavio González-del Moral Alberto Hernán-Gómez Miguel Mena Cristina Santamaría 《Journal of organometallic chemistry》2011,696(25):4011-4017
The ability of the oxonitride [{Ti(η5-C5Me5)(μ-O)}3(μ3-N)] (1) to act as an organometallic ligand has been studied from both theoretical and experimental points of view. DFT calculations have allowed understanding the electronic structure of 1, and rationalizing its chemical behavior by comparison with the electronic structures of isoelectronic species [{Ti(η5-C5Me5)(μ-O)}3(μ3-CH)] and [{Ti(η5-C5Me5)(μ-NH)}3(μ3-N)]. Reactions of 1 with different inorganic molecules such as [Mo(CO)3(1,3,5-Me3C6H3)] or AlEt3 have confirmed the possibility of 1 to act as a tridentate or monodentate ligand to give the [{(CO)3Mo}(μ3-O)3{Ti3(η5-C5Me5)3(μ3-N)}] (2) and [{Et3Al}(μ3-O){(μ-O)2Ti3(η5-C5Me5)3(μ3-N)}] (3) complexes, respectively. Surprisingly, reactions of 1 with [M(CO)6] (M = Cr, Mo, W) complexes led to activate the μ3-N unit in 1 to afford the new compounds [Ti3(η5-C5Me5)3(μ-O)4{(NC)M(CO)5}]2 [M = Cr (4), Mo (5), W (6)]. Molecular structures of complexes 2-6 have been established by single crystal X-ray analysis. 相似文献
104.
Ayesha Kausar Sonia Zulfiqar Liaquat Ali Muhammad Ilyas Sarwar 《Monatshefte für Chemie / Chemical Monthly》2011,17(3):201-209
Abstract
New diacid dichlorides bearing phenyl thiourea groups were prepared by a facile synthetic approach and characterized using spectroscopic and elemental analyses. A series of novel aromatic and semiaromatic polyamides were prepared via a condensation route from the synthesized diacid dichlorides with 4,4′-oxydianiline. The polymers were characterized by FT-IR, 1H NMR, 13C NMR, and their physical properties, including their solution viscosities, solubilities and thermal properties, were studied too. Polyamides with phenyl thiourea moieties in the backbone showed good solubilities in amide solvents such as DMAc, DMF, DMSO, and NMP. All of the synthesized polymers had η inh values of 0.042–0.053 dm3/g, and were obtained in quantitative yield. GPC measurements of the synthesized polyamides indicated M w values of 64,759–86,172. The crystallinity of the polymers was evaluated via their X-ray diffraction patterns. Their glass transition temperatures were found to be 218–229 °C. Furthermore, thermogravimetric analysis indicated that the polymers were thermally stable in the range 300–398 °C in a N2 atmosphere. 相似文献105.
Santos Fustero Javier MoscardóMaría Sánchez-Roselló Sonia FloresMarta Guerola Carlos del Pozo 《Tetrahedron》2011,67(38):7412-7417
The organocatalytic synthesis of quinolizidine alkaloids (+)-myrtine, (−)-lupinine, and (+)-epiepiquinamide is described. It involved, as the key step, an enantioselective intramolecular aza-Michael reaction (IMAMR) catalyzed by Jørgensen catalyst I, affording the common precursor with high enantioselectivity. This compound was subsequently transformed into the three alkaloids in a highly diastereoselective manner. 相似文献
106.
Martínez-Salvador S Forniés J Martín A Menjón B 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(29):8085-8097
The homoleptic, square‐planar organoplatinum(II) compound [NBu4]2[Pt(CF3)4] ( 1 ) undergoes oxidative addition of CF3I under mild conditions to give rise to the octahedral organoplatinum(IV) complex [NBu4]2[Pt(CF3)5I] ( 2 ). This highly trifluoromethylated species reacts with Ag+ salts of weakly coordinating anions in Me2CO under a wet‐air stream to afford the aquo derivative [NBu4][Pt(CF3)5(OH2)] ( 4 ) in around 75 % yield. When the reaction of 2 with the same Ag+ salts is carried out in MeCN, the solvento compound [NBu4][Pt(CF3)5(NCMe)] ( 5 ) is obtained in around 80 % yield. The aquo ligand in 4 as well as the MeCN ligand in 5 are labile and can be cleanly replaced by neutral and anionic ligands to furnish a series of pentakis(trifluoromethyl)platinate(IV) compounds with formulae [NBu4][Pt(CF3)5(L)] (L=CO ( 6 ), pyridine (py; 7 ), tetrahydrothiophene (tht; 8 )) and [NBu4]2[Pt(CF3)5X] (X=Cl ( 9 ), Br ( 10 )). The unusual carbonyl–platinum(IV) derivative [NBu4][Pt(CF3)5(CO)] ( 6 ) is thermally stable and has a νCO of 2194 cm?1. The crystal structures of 2? CH2Cl2, 5 , [PPh4][Pt(CF3)5(CO)] ( 6′ ), and 7 have been established by X‐ray diffraction methods. Compound 2 has shown itself to be a convenient entry to the chemistry of highly trifluoromethylated platinum compounds. To the best of our knowledge, compounds 2 and 4 – 10 are the organoelement compounds with the highest CF3 content to have been isolated and adequately characterized to date. 相似文献
107.
Geagea R Ladeira S Mazières S Destarac M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(13):3718-3725
Molybdenum and chromium pentacarbonyldiphenylphosphinocarbodithioate complexes have been prepared in a one‐pot reaction from the corresponding metallocarbonyldiphenylphosphine. The complexes have been characterised by IR, 1H, 31P and 13C NMR spectroscopies and by mass spectrometry. The solid‐state structures of [Cr(CO)5{PPh2CS2CH(Ph)CH3}] ( 1 ) and [Mo(CO)5{PPh2CS2CH(Ph)CH3}] ( 2 ) are reported. Compounds 1 and 2 are isostructural and crystallise in the triclinic P$\bar 1Molybdenum and chromium pentacarbonyldiphenylphosphinocarbodithioate complexes have been prepared in a one-pot reaction from the corresponding metallocarbonyldiphenylphosphine. The complexes have been characterised by IR, (1)H, (31)P and (13)C?NMR spectroscopies and by mass spectrometry. The solid-state structures of [Cr(CO)(5){PPh(2)CS(2)CH(Ph)CH(3)}] (1) and [Mo(CO)(5){PPh(2)CS(2)CH(Ph)CH(3)}] (2) are reported. Compounds 1 and 2 are isostructural and crystallise in the triclinic P1 space group. These new organometallic compounds are highly efficient reversible chain-transfer agents for reversible addition-fragmentation chain-transfer (RAFT) polymerisation of styrene (St) and n-butyl acrylate (nBA), with controlled number-average molar mass values and narrow dispersities (<1.2). The controlled character of the polymerisation was further exemplified by the synthesis of St and nBA diblock copolymers. 相似文献
108.
Boronate ureas are introduced as a new class of noncovalent catalysts for conjugate addition reactions with enhanced activity. Through intramolecular coordination of the urea functionality to a strategically placed Lewis acid, rate enhancements up to 10 times that of more conventional urea catalysts are observed. The tunable nature of boronate ureas is a particularly attractive feature and enables the rational design of catalysts for optimal performance, in terms of both activity and stereocontrol, in new bond-forming processes. 相似文献
109.
110.
Zattoni A Rambaldi DC Casolari S Roda B Reschiglian P 《Journal of chromatography. A》2011,1218(27):4132-4137
Reinjection of one ore more collected fractions of eluted samples is recognized as a useful procedure in analytical separation techniques, among which field-flow fractionation (FFF), to improve the actual separation of complex samples. Hollow-fiber flow FFF (HF5) is a micro-channel subset of flow FFF (F4), which has recently reached a performance comparable to that of standard, flat-channel F4. To further improve HF5 of complex protein samples, we present a new device and method for in-line, reinjection HF5 that we call tandem HF5 (HF5/HF5). HF5 is ideally suited for tandem operation because (1) small channel volume and low operation flow rates allow reducing dilution and volume of the collected fractions, and (2) the relaxation/focusing step that takes place between the 1st and 2nd run (refocusing) allows reestablishing the volume and concentration of the sample plug before the 2nd elution. HF5/HF5 proves particularly effective in the case of oligomeric proteins since it allows collecting and reinjecting the bands that correspond to each separated oligomeric form. This provides information on the dynamic equilibria between the different oligomers. For HF5/HF5 operations, a modified, prototype HF5 instrumentation is presented which includes a "trap" constituted of a four-port, two-way valve positioned downstream the UV detector and a collection loop. The effect of refocusing conditions on HF5/HF5 performance is investigated by varying refocusing time. With a complex protein samples such as blood serum, HF5/HF5 can improve detectability of the low abundance components since overloading effects due to high-abundance components are reduced. This is shown for serum lipoproteins: while after the 1st run high density lipoproteins (HDLs) are not separated from high-abundance serum proteins, after the 2nd run it is shown possible to separate the HDL subclasses. 相似文献