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981.
Study of fungal degradation products of polycyclic aromatic hydrocarbons using gas chromatography with ion trap mass spectrometry detection 总被引:5,自引:0,他引:5
Representatives of polycyclic aromatic hydrocarbons (PAHs) were degraded by ligninolytic fungus Irpex lacteus. The products were analyzed by GC-Ion trap mass spectrometry. The combination of full scan mass spectra, product ion scans (MS-MS) and derivatization of the degradation products of anthracene, phenanthrene, fluoranthene and pyrene provided further insight in the degradation mechanism initiated by I. lacteus. Particularly, the product ion scans enabled the interpretation of unknown degradation products, even though they were only produced at trace level. Most of the structures suggested were later confirmed with authentic standards. 相似文献
982.
We report the initial Fock space multireference coupled cluster method with the full inclusion of single, double, and triple excitations (FS-CCSDT) for the (1,1) sector. We present pilot applications for calculating excitation energies for the N(2) molecule and the Ne atom. The performance of the current model, along with the FS-CCSD one, has been studied in comparison with the equation-of-motion coupled-cluster and the similarity transformed methods. 相似文献
983.
[structure: see text] The 1,3-diphenyl-1H-pyrazolo[3,4-b]-quinoline chromophore is a versatile building block for the construction of brightly fluorescent molecular sensors. Facile synthetic procedures allow integration of the chromophore into fluorophore-spacer-receptor systems as well as fluoroionophores operating via intramolecular charge transfer. Whereas the former photoinduced electron-transfer probes show strong analyte-induced fluorescence enhancement, the latter exhibit bright ratiometric dual emission. Employing prototype macrocyclic receptors, the favorable signaling features for metal ion recognition are demonstrated. 相似文献
984.
[reaction: see text]. Glycoproteins are particularly suited to protein semisynthesis since homogeneous samples for biological analyses are not readily available using traditional recombinant techniques. Here we apply glycosyl iodoacetamides, normally used for the modification of bacterially derived proteins, to solid-phase glycopeptide synthesis. This provides access to glycopeptide alpha-thioesters, which may lend themselves to the semisynthesis of homogeneous N-linked glycoprotein mimics and novel glycopeptide libraries. 相似文献
985.
Maria Gdaniec Tomasz Bytner Monika Szyrszyng Tadeusz Połonski 《Journal of inclusion phenomena and macrocyclic chemistry》2001,40(3):243-247
The crystalline inclusion compounds of cholic acid (CA) and deoxycholic acid (DCA) with several nitrosobenzenes were prepared. The IR spectra and crystal structures of these compounds confirmed inclusion of the monomeric form of the C-nitroso compounds. The DCA compounds have 2 : 1 host:guest stoichiometry and P21 symmetry. Guest molecules are enclosed in channels and disordered. In the CA-nitrobenzene inclusion compound (1·CA) the host:guest stoichiometry is 1 : 1. The host molecules form typical CA bilayer aggregates and guest molecules are accommodated in helicoidal channels. The guest nitroso group is not coplanar with the phenyl ring; the torsion angle on the C–N bond is 8.6(8)°. The solid-state circular dichroism spectrum of 1·CA shows the negative Cotton effect at 780 nm corresponding to the n–* electronic transition that can be associated with the P helicity of the guest molecule. The extremely weak magnitude of the Cotton effects exhibited by the DCA complexes points to a nearly planar arrangement of the NO group and the phenyl ring in the guest molecules. 相似文献
986.
Differences between the rates of oxidation of substrates by horseradish peroxidase in buffer, aqueous micellar solution of
Brij 35 and in reverse micelles formed of Brij 30 in several hydrocarbons are discussed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
987.
In vivo study of triazine herbicides in plants by SPME 总被引:1,自引:0,他引:1
The use of SPME for in vivo monitoring of herbicide levels in plant tissues is evaluated. Fibers are exposed to the plant tissue with the aid of buffer located at the fiber/tissue interface region. Following this extraction period the extracted amount is estimated by solvent desorption and LC-MS-MS. 相似文献
988.
989.
Gruszecki WI Gagoś M Hereć M 《Journal of photochemistry and photobiology. B, Biology》2003,69(1):49-57
Fluorescence emission from amphotericin B dissolved in 2-propanol-water was recorded in the spectral region 500-650 nm. The fluorescence excitation spectrum corresponds to the absorption spectrum of the monomeric drug. The large energy shift between the excitation and emission bands indicates that emission takes place from an energy level different than that responsible for absorption. These levels were attributed to the 2(1)A(g) and 1(1)B(u) states, respectively. Excitation of the same sample with short wavelength radiation (below 350 nm) yields light emission between 400 and 550 nm. The fluorescence excitation spectrum corresponding to this emission band displays distinct maxima at 350, 334 and 318 nm. This band was analyzed in terms of the exciton splitting theory and assigned to amphotericin B in a dimeric form, in which chromophores are spaced by 4.9 A. The binding energy of the dimers, determined to be 4.9 kJ/mol, indicates that the structures are stabilized by van der Waals interactions. The same type of molecular structures was also detected in the lipid membranes formed with dipalmitoylphosphatidylcholine. Linear dichroism of amphotericin B embedded in lipid multibilayers indicates that molecules are distributed between two fractions: parallel (38%) and perpendicular (62%) with respect to the membrane. The biological importance of such membrane organization is discussed. 相似文献
990.
Gas-liquid chromatography was applied to investigate the mechanism of alpha-cyclodextrin (alpha-CD) complexation processes with some chiral monoterpenoids differing from each other in chemical properties and structure. They were chosen from hydrocarbons, alcohols, aldehydes and ketones of acyclic, monocyclic and bicyclic structure. The relationships between the retention factor, k, of a guest solute (G) and alpha-CD concentration were studied. The obtained data enabled the stoichiometry, the stability of individual complexes and the separation factor of enantiomers to be determined. It was found that almost all the investigated monoterpenoids, apart from the acyclic ones, form inclusion complexes with alpha-CD. Straight-line relations (r vs. [alpha-CD]) were observed for monocyclic alcohols and pulegone, without any trace of enantioselectivity. This behaviour indicates that the 1:1 stoichiometry of the G-CD complexes does not lead to chiral recognition. Parabolic relations arising from 1:2 stoichiometry were found for limonene, alpha-phellandrene, some monocycylic ketones and all the investigated bicyclic terpenoids. It appeared that only the second step of complexation displayed marked enantioselectivity. However, a loss of efficiency resulting from slower equilibration is then noticeable. Attempts are made to rationalize the chromatographic results with respect to the structure of the investigated compounds. 相似文献