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101.
Milan Jakubek Zdeněk Kejík Robert Kaplánek Hana Veselá David Sýkora Pavel Martásek 《Supramolecular chemistry》2018,30(3):218-226
Perimidine-based chelators 1 and 2 were prepared, and their structures were confirmed by 1H and 13C NMR, MS spectroscopy and elemental analysis. These compounds were studied as specific synthetic receptors for the recognition of transition metal ions. They exhibited high affinity and selectivity towards Cu(II) ions. The conditional binding constants, linear dynamic range and detection limit were determined by UV–vis spectroscopy. These parameters demonstrated high potential of the prepared synthetic receptors for the recognition and determination of Cu(II) ions. The minimum detectable concentrations of Cu(II) ions for the synthetic receptors 1 and 2 were 270 and 75 nM (R 2 = 0.9915 and 0.9964) in aqueous medium (water/DMSO; 99:1 (v/v)), respectively. 相似文献
102.
Melanin offers protection against induction of cyclobutane pyrimidine dimers and 6-4 photoproducts by UVB in cultured human melanocytes 总被引:3,自引:0,他引:3
Smit NP Vink AA Kolb RM Steenwinkel MJ van den Berg PT van Nieuwpoort F Roza L Pavel S 《Photochemistry and photobiology》2001,74(3):424-430
The goal of this investigation was to correlate the melanin content in human pigmentary cells with the generation of UVB-induced photoproducts and to examine the relationship between the melanin content and the removal of the photoproducts. Cultured melanocytes from light-skinned individuals synthesized less melanin and produced more cyclobutane pyrimidine dimers and 6-4 photoproducts upon UVB exposure than did melanocytes from black skin. Tyrosine-stimulated melanogenesis provided protection against DNA damage in both cell types. In another set of pigmented cell lines a ratio between eumelanin and pheomelanin was determined. The assessment of association between DNA damage induction and the quantity and quality of melanin revealed that eumelanin concentration correlated better with DNA protection than pheomelanin. Skin type-I and skin type-VI melanocytes, congenital nevus (CN)-derived cells and skin type-II melanocytes from a multiple-melanoma patient were grown in media with low or high L-tyrosine concentration. The cells were irradiated with 200 J/m2 UVB, and the levels of the photoproducts were determined immediately and after 6 and 24 h. Once again the induction of the photoproducts was mitigated by increased melanogenesis, and it was inversely correlated with the skin type. No significant differences were found for the removal of photoproducts in the cultures of skin types I and VI and CN cells. No indications of a delay in the removal of photoproducts in the melanocytes from the multiple-melanoma patient were found either. 相似文献
103.
Alexander S. Lyakhov Pavel N. Gaponik Sergei V. Voitekhovich Ludmila S. Ivashkevich Alexander A. Kulak 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(10):1204-1206
There are two symmetry-independent molecules in the unit cell of the title compound, C7H5N5O3. The tetrazole and phenyl rings are essentially planar and are not coplanar in either molecule [dihedral angles 30.2 (1) and 7.0 (1)°]. In the structure, four molecules are connected by O—H⃛N bridges, forming four-membered molecular aggregates which are linked together by a complex three-dimensional hydrogen-bond network. 相似文献
104.
Pavel Rosmus 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》1987,99(12):1333-1335
105.
Pavel A. Dub Vladislava A. Levina Elena S. Shubina 《Journal of organometallic chemistry》2011,696(6):1174-6773
Compound trans-PtBr2(C2H4)(NHEt2) (1) has been synthesized by Et2NH addition to K[PtBr3(C2H4)] and structurally characterized. Its isomer cis-PtBr2(C2H4)(NHEt2) (3) has been obtained from 1 by photolytic dissociation of ethylene, generating the dinuclear trans-[PtBr2(NHEt2)]2 intermediate (2), followed by thermal re-addition of C2H4, but only in low yields. The addition of further Et2NH to 1 in either dichloromethane or acetone yields the zwitterionic complex trans-Pt(−)Br2(NHEt2)(CH2CH2N(+)HEt2) (4) within the time of mixing in an equilibrated process, which shifts toward the product at lower temperatures (ΔH° = −6.8 ± 0.5 kcal/mol, ΔS° = 14.0 ± 2.0 e.u., from a variable temperature IR study). 1H NMR shows that free Et2NH exchanges rapidly with H-bonded amine in a 4·NHEt2 adduct, slowly with the coordinated Et2NH in 1, and not at all (on the NMR time scale) with Pt-NHEt2 or -CH2CH2N(+)HEt2 in 4. No evidence was obtained for deprotonation of 4 to yield an aminoethyl derivative trans-[PtBr2(NHEt2)(CH2CH2NEt2)]− (5), except as an intermediate in the averaging of the diasteretopic methylene protons of the CH2CH2N(+)HEt2 ligand of 4 in the higher polarity acetone solvent. Computational work by DFT attributes this phenomenon to more facile ion pair dissociation of 5·Et2NH2+, obtained from 4·Et2NH, facilitating inversion at the N atom. Complex 4 is the sole observable product initially but slow decomposition occurs in both solvents, though in different ways, without observable generation of NEt3. Addition of TfOH to equilibrated solutions of 4, 1 and excess Et2NH leads to partial protonolysis to yield NEt3 but also regenerates 1 through a shift of the equilibrium via protonation of free Et2NH. The DFT calculations reveal also a more favourable coordination (stronger Pt-N bond) of Et2NH relative to PhNH2 to the PtII center, but the barriers of the nucleophilic additions of Et2NH to the C2H4 ligand in 1 and of PhNH2 to trans-PtBr2(C2H4)(PhNH2) (1a) are predicted to be essentially identical for the two systems. 相似文献
106.
Kamil Motyka Jan Hlavá?Miroslav Soural Pavel HradilPetr Krej?í Lubomír KvapilMiloš Weiss 《Tetrahedron letters》2011,52(6):715-717
2-(4-Amino-substituted-3-nitrophenyl)-3-hydroxyquinolin-4(1H)-ones have been studied to evaluate their fluorescence properties and possible use as molecular fluorescent probes. The amino group was substituted with various alkyl moieties possessing a suitable terminal functional group (such as hydroxy or amino group) that could serve to bind a 3-hydroxyquinolin-4(1H)-one (3HQ) fluorescence label to a biomolecule. Besides simple hydrocarbon chains, ligands containing ethylenoxy units as optimal spacers were also tested. The structure-fluorescence properties and theoretical applicability of the studied molecules are discussed. 相似文献
107.
Gonec T Bobal P Sujan J Pesko M Guo J Kralova K Pavlacka L Vesely L Kreckova E Kos J Coffey A Kollar P Imramovsky A Placek L Jampilek J 《Molecules (Basel, Switzerland)》2012,17(1):613-644
In this study, a series of thirty-five substituted quinoline-2-carboxamides and thirty-three substituted naphthalene-2-carboxamides were prepared and characterized. They were tested for their activity related to the inhibition of photosynthetic electron transport (PET) in spinach (Spinacia oleracea L.) chloroplasts. Primary in vitro screening of the synthesized compounds was also performed against four mycobacterial species. N-Cycloheptylquinoline-2-carboxamide, N-cyclohexylquinoline-2-carboxamide and N-(2-phenylethyl)quinoline-2-carboxamide showed higher activity against M. tuberculosis than the standards isoniazid or pyrazinamide and 2-(pyrrolidin-1-ylcarbonyl)quinoline and 1-(2-naphthoyl)pyrrolidine expressed higher activity against M. kansasii and M. avium paratuberculosis than the standards isoniazid or pyrazinamide. The most effective antimycobacterial compounds demonstrated insignificant toxicity against the human monocytic leukemia THP-1 cell line. The PET-inhibiting activity expressed by IC(50) value of the most active compound N-benzyl-2-naphthamide was 7.5 μmol/L. For all compounds, the structure-activity relationships are discussed. 相似文献
108.
Inside Cover: A Non‐Exploding Alkali Metal Drop on Water: From Blue Solvated Electrons to Bursting Molten Hydroxide (Angew. Chem. Int. Ed. 42/2016) 下载免费PDF全文
109.
Vapor pressures of six pentanols, 2-methyl-1-butanol (CAS Registry Number 137-32-6), 2-methyl-2-butanol (CAS Registry Number 75-85-4), 3-methyl-1-butanol (CAS Registry Number 123-51-3), 3-methyl-2-butanol (CAS Registry Number 598-75-4), 2-pentanol (CAS Registry Number 6032-29-7) and 3-pentanol (CAS Registry Number 584-02-1), were measured by the precision ebulliometry over an approximate pressure range from 9 to 99 kPa. The absolute uncertainties in pressure and temperature are estimated to be less than or equal to 7 Pa and 0.02 K, respectively. The results are represented by the Antoine equation and compared with available literature data. 相似文献
110.
Electronic structure of manganese ferrite is calculated using the density functional theory. Partially inverted structure with the inversion parameter y=0.0625 is considered, using four different supercells (Mn15Fe)A[Fe31Mn]BO64 that differ in relative position of FeA and MnB. The crystal structure was optimized by minimizing the forces acting on the atoms. The spin magnetic moments m of Mn and Fe ions depend to some extent on their position in the supercell, but we found that in all cases m(MnB) is considerably smaller (by approx. one Bohr magneton) than m(MnA). This indicates strongly that the formal valence of MnB is 3+. Trivalent manganese in an octahedral position is expected to exhibit a Jahn–Teller effect and corresponding analysis was performed. No pronounced localization of the extra electron in the octahedral sublattice that would represent the Fe2+ ion was found. 相似文献