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301.
302.
Laura Pop Pierrik Lassalas László Csaba Bencze Monica Ioana Toşa Botond Nagy Florin Dan Irimie Christophe Hoarau 《Tetrahedron: Asymmetry》2012,23(6-7):474-481
Stereoselective preparative enzymatic acylation and hydrolysis/methanolysis of various C-substituted rac-thiazol-2-yl-methanols were achieved for the preparation of enantiopure or enantiomerically enriched, naturally occurring 2-hydroxymethylthiazoles. The absolute configurations of the resulting secondary alcohols were determined by a detailed 1H NMR study of Mosher’s derivatives. 相似文献
303.
Dmitar Zori? Du?an Lazar Ognjen Rudi? Miroslava Radeka Jonjaua Ranogajec Helena Hir?enberger 《Journal of Thermal Analysis and Calorimetry》2012,110(1):489-495
The article presents the results of physical and chemical properties of lightweight aggregates (LWA) obtained by the thermal treatments of raw composition based on fly ash, supplied by electric plants from Serbia. The production process of LWA consists of raw material preparation, plastic shaping?Cextrusion, granulation, and thermal treatment at three temperatures: 1100, 1150, and 1200?°C. The final firing temperature (T?=?1150?°C) is chosen based on the mechanical and physical properties of the designed aggregates. The particle-size distribution of the LWAs is unimodal (d????16?mm) while the density value varies from 0.98 to 1.99?g/cm3. The water absorption values are determined by use of two methods: 24?h of soaking in cold water and 5?h of boiling. The thermal conductivity of unbound, fired LWA particles is determined by measuring the amount of axially transferred heat in the stationary state. The obtained value of the LWA thermal conductivity (???=?0.0872?W/mK, T?=?1150?°C) is suitable for the production of structural concrete blocks with improved thermal insulating properties. Because of their high-porosity and -compressive strength values, the designed LWA could be used instead of the conventional aggregates in the production of concrete blocks. Consequently, a real valorization of the waste material such as fly ash in Serbia was established. 相似文献
304.
Silvia Dulanská Boris Remenec Erik Durkot Du?an Galanda ?ubomír Mátel 《Journal of Radioanalytical and Nuclear Chemistry》2012,293(3):847-850
Procedure for analysis of plutonium isotopes in soil samples was developed using a new molecular recognition technology product AnaLig?Pu-02 gel. Extraction chromatography TEVA? Resin was used for purification of plutonium phase to remove thorium impurities which interfere in Pu determination by alpha spectrometry. The performance of the method was successfully tested by analysis of a sand stimulant sample and a soil sample spiked with known activity of 239Pu. The results obtained for procedures were compared in terms of activities and recoveries. 相似文献
305.
Alkali Blue 6B-attached poly(2-hydroxyethyl methacrylate) (poly(HEMA)) microporous films were investigated as chelate forming sorbents for heavy metal removal. Poly(HEMA) microporous films were prepared by UV-initiated photo-polymerization of HEMA in the presence of an initiator (azobisisobutyronitrile (AIBN)). Alkali Blue 6B was attached covalently. These films with a swelling ratio of 58%, and carrying 14.8 mmol Alkali Blue 6B m(-2) which were then used in the removal of Cd(II), Zn(II) and Pb(II) from aqueous media. Adsorption rates were very high, equilibrium was achieved in about 30 min. The maximum adsorption of heavy metal ions onto the Alkali Blue 6B-attached films were 41.4 mmol m(-2) for Cd(II), 52.4 mmol m(-2) for Zn(II), and 64.5 mmol m(-2) for Pb(II). When the heavy metal ions competed during the adsorption from a mixture the adsorption values for Cd(II), Zn(II) and Pb(II) were quite close. Heavy metal ions were desorbed by using 0.1 M HNO(3). A significant amount of the adsorbed heavy metal ions (up to 95%) could be desorbed in 30 min. Repeated adsorption/desorption cycles showed the feasibility of these novel dye-attached microporous films for heavy metal removal. 相似文献
306.
Marija Mirković Drina Janković Sanja Vranješ‐Đurić Magdalena Radović Dragana Stanković Dušan Mijin Nadežda Nikolić 《应用有机金属化学》2012,26(7):347-355
Two novel diamine dioxime ligands, 4,7‐diaza‐3,8‐diethyldecane‐2,9‐dione bis oxime (3) and 4,9‐diaza‐3,10‐diethyldodecane‐2,11‐dione bis oxime (5), were synthesized in order to develop new brain perfusion imaging agents, based on 99mTc(V)‐complexes. The synthesis involved condensation of 2‐hydroxyimino‐3‐pentanone with appropriate diamine in protic solvent which afforded the bis imine adducts. Subsequent reduction of imine functional groups yielded a diastereoisomeric mixture of 3 and 5. UV–visible, IR, 1H NMR, 13C NMR and elemental analysis were used to characterize the structures of the synthesized compounds. 99mTc‐complexes of both diamine dioximes were prepared and radiolabeling conditions optimized to give the maximum yield. Physicochemical parameters of the labeled complexes as well as and their biodistribution in rats were investigated. Both compounds (3 and 5) formed 99mTc‐complexes with a net charge of zero, determined by electrophoresis. The resultant lipophilic 99mTc‐complexes of 3 and 5 were readily formed at pH ~9.0 within 10 min at room temperature with yields of 90% and 95%, respectively. The 99mTc‐3 complex was found to be stable within 1 h, while 99mTc‐5 was stable for a few hours. A significant brain uptake of 99mTc‐3 (2.1% injected dose) and 99mTc‐5 (1.8% injected dose) complexes, 2 min after injection, is in accordance with their lipophilicity. The present study suggests that both ligands are promising candidates as new 99mTc‐based brain‐imaging agents. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
307.
Beşli S Coles SJ Davies DB Eaton RJ Hursthouse MB Kiliç A Shaw RA Yenilmez Ciftçi G Yeşilot S 《Journal of the American Chemical Society》2003,125(16):4943-4950
A problem has arisen in using chiral shift reagents (CSR) and chiral solvating agents (CSA) to determine meso and racemic forms of diastereoisomers in which the stereogenic centers of the molecules are separated by achiral spacers. It is found that NMR signals of both meso and racemic forms of diastereoisomers may exhibit doubling on addition of CSR/CSA, which means that unequivocal assignments cannot be made without characterizing the effects for separate meso and racemic forms; this is particularly important for additions of CSR/CSA at relatively low concentrations, which always result in the splitting of some NMR signals of diastereoisomers. The phenomenon is demonstrated in the (31)P NMR spectra of meso and racemic forms of three spermine-bridged gem-disubstituted cyclotriphosphazatrienes, 1a-c, and compared with analogous achiral molecules, the per-substituted spermine-bridged cyclotriphosphazatrienes 2a-d. As expected, only one set of (31)P NMR signals was observed for the achiral compounds 2a-d, even on addition of CSA. Two sets of (31)P NMR ABX multiplets corresponding to meso and racemic diastereoisomers were observed for compounds 1a-c; on addition of CSA, the signals of at least one of the multiplets for each compound separated into more than the expected groups of three lines with an intensity distribution of 2:1:1. To understand this phenomenon, the meso and racemic forms of 1a and 1b and the meso form of 1c have been separated and characterized by X-ray crystallography. On addition of CSA to the racemic forms of 1a and 1b, the (31)P NMR spectrum shows the expected doubling of signals, but, unexpectedly, the same is observed for each of the meso forms of 1a-c. Analogous results using both CSA and CSR have been obtained for the meso and racemic forms of the diastereoisomeric piperazine-bridged macrocyclic-phosphazene compound, 3, whereas no effect was observed for the two meso forms of the doubly bridged macrocyclic-phosphazene compound 4. The phenomenon of doubling of the (31)P NMR signals of the meso form of singly bridged cyclotriphosphazatrienes, 1a-c and 3, is explained by consideration of the equilibrium in solution of independent complexation of a chiral ligand with molecules that have two chiral cyclophosphazene moieties separated by an achiral spacer group. The results show that the stereogenicity of such diastereoisomeric molecules in solution cannot be characterized unequivocally by NMR measurements on addition of either CSR or CSA. 相似文献
308.
Chemical effects on Kβ/Kα X-ray intensity ratios for some Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn compounds are studied experimentally. The X-ray spectra were measured by using a Si (Li) solid state detector with high resolution. The vacancies were produced by heavily filtered 241Am gamma rays. It is found that the Kβ/Kα X-ray intensity ratios measured with compounds deviated up to 43% from the corresponding values of the pure elements. The values for pure elements are compared with the other experimental and with theoretical values. 相似文献
309.
E. M. Köksal N. Çelebi B. Ataksor A. Ulug M. Taşdelen G. Kopuz B. Akar M. T. Karabulut 《Journal of Radioanalytical and Nuclear Chemistry》2004,259(2):213-216
As part of a national program to determine public exposure to natural radiation, indoor air 222Rn concentrations were determined in dwellings of Turkey. The 222Rn concentrations were measured with time-integrating passive nuclear etched track detectors in 27 provincial centers. The
indoor radon concentrations were found to be in the range of 10-380 Bq.m-3.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
310.
Haçan Awad François Trécourt Guy Quéguiner Francis Marsais 《Tetrahedron letters》2004,45(42):7873-7877
4-Chloropyridine was deprotonated on treatment with 1/3 equiv of the highly coordinated magnesate Bu3(TMP)MgLi2 in THF at −10 °C, as evidenced by trapping with I2. The use of Bu(TMP)2MgLi in Et2O allowed the reaction of 2-chloropyridine, giving the 3-functionalized derivative as the main product. Mixtures of 3- and 4-functionalized derivatives were obtained when 2,6-dichloropyridine was involved in the reaction. Performing the reaction on 3-chloropyridine with lithium magnesates in THF, either the 4,4′-dimer or the 4-iodo derivative was formed after quenching by I2, the former using 1/3 equiv of Bu2(TMP)MgLi and the latter using 1 equiv of (TMP)3MgLi. Similar results were observed with 3,5-dichloropyridine, 2,5-dichloropyridine and 3-chloro-2-fluoropyridine. 1,2-Migration of the lithium arylmagnesate formed by deprotonation was proposed to justify the dimers formation. 相似文献