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991.
Marijana Gavranić Branko Kaitner Ernest Meštrović 《Journal of chemical crystallography》1996,26(1):23-28
The structures of N-(-naphthyl)-2-oxy-1-naphthaldimine1 and N-(-naphthyl)-2-oxy-1-naphthaldimine2 have been investigated by X-ray analysis and by spectroscopic methods. Crystals of1 are monoclinic, space groupPn, with cell dimensionsa=10.823(3),b=5.826(2),c=11.899 (3) Å, and =99.66(3)°. Compound2 crystallizes in the orthorhombic space groupPca21 witha=17.564(3),b=6.314(2), andc=13.663(4) Å. The IR spectra exhibited neither N–H nor O–H stretching frequencies. The existence of theintramolecular hydrogen bonding of N–H...O type was predicted by spectroscopic experiment but unequivocally established by diffraction experiment in both cases1 and2. The molecules1 and2 are significantly planar with considerable quinoid effect at the 2-oxy-naphthaldimine moiety. Although essentially planar, both molecules1 and2 show the delocalization of -electrons only in the central part of the molecules including C=N imino group with pendent ring carbon atoms.Intermolecular attractions in the crystals belong to weak van der Waals interactions-between discrete planar molecules spatially arranged into the expectedherringbone motif in the solid state. 相似文献
992.
A new heterogeneous catalyst composed of copper and nickel oxide particles supported within charcoal has been developed. It catalyzes cross-couplings that traditionally use palladium, nickel, or copper, including Suzuki-Miyaura reactions, Buchwald-Hartwig aminations, vinylalane alkylations, etherifications of aryl halides, aryl halide reductions, asymmetric conjugate reductions of activated olefins, and azide-alkyne "click" reactions. 相似文献
993.
The two component one-pot hydroformylation/Fischer indole synthesis sequence of 2,5 dihydropyrroles and phenyl hydrazines allows a facile and convenient access to tetrahydro-beta-carbolines in moderate to good yields. 相似文献
994.
This work is an extension of our investigations of the Kolbe--Schmitt reaction mechanism. The last step in the para route of the carboxylation reaction of alkali metal phenoxides is investigated at the B3LYP/LANL2DZ level of theory. Among several examined pathways, two mechanisms are proposed: the one involving a successive rearrangement of hydrogen and the other one based on the formation of free radicals. The former pathway is energetically comparable to the last step of the carboxylation reaction in the ortho position, whereas the latter pathway requires higher activation energy. Bearing in mind that the Kolbe--Schmitt reaction is performed at high temperatures, we assume that both reaction paths are plausible. 相似文献
995.
Marković S Stanković S Radenković S Gutman I 《Journal of chemical information and modeling》2008,48(10):1984-1989
The electronic structure of dicyclopenta[de,mn]anthracene (P1), dicyclopenta[ de,kl]anthracene (P2), and dicyclopenta[jk,mn]phenanthrene (P3) and their mutual isomerization processes are investigated using density functional theory. Two mechanisms for the thermal intraconversion of P1 to P2 were found. The first mechanism occurs via ethynylaceanthrylene (I0), and the second involves a 1,2-hydrogen shift. It is supposed that I0 is initially formed during the flash vacuum pyrolysis experiments, eventually rearranging to P2 on high temperatures. The energetics of the latter mechanism also indicate that P1 isomerizes to P2. The mechanism for a transformation of P2 to P3 is based on a ring contraction/ring conversion process and requires extremely high temperatures. Our investigation is in accord with the experimental results: unsuccessful synthesis of P1, stability of P2 at high temperature, and formation of P3 under extreme temperature regime. 相似文献
996.
Zarei M Kirsch S Müthing J Bindila L Peter-Katalinić J 《Analytical and bioanalytical chemistry》2008,391(1):289-297
The coupling of nano high-performance liquid chromatography (nanoHPLC) with matrix-assisted laser desorption/ionization (MALDI)
mass spectrometry (MS) via an automatic spotting roboter was developed and adapted for the first time for the analysis of
complex mixtures of glycosphingolipids (GSLs). The 2,5-dihydroxybenzoic acid and 6-azo-2-thiothymine matrix systems were adjusted
to concurrently meet the requirements for reproducible and homogeneous crystal formation with the liquid chromatography (LC)
eluent under the variable LC solvent composition over the course gradient and high ionization efficiency of the GSL species,
without the need for recrystallization. Precise adjustment of the automatic spotting parameters in terms of matrix flow rate,
on-tip collection time of the matrix/LC eluent solution and the matrix spotting mode, i.e., continuous and discontinuous,
was accomplished to collect individually nanoHPLC-separated species within distinct spots and consequently recover by MALDI
MS screening all major and minor GSL species in the mixtures. The nanoHPLC/MALDI MS coupling protocol was developed and applied
to a mixture of neutral GSLs purified from human erythrocytes and a monosialoganglioside mixture expressed by the murine MDAY-D2
cell line. Additionally, on-line nanoHPLC/MALDI doping with lithium cations of individually separated neutral GSLs was introduced
to enhance data interpretation of the GSL MS pattern, while preserving the same level of information and ultimately to enhance
structural assignment of components of interest. The method is demonstrated to be highly sensitive, reaching the low femtomole
level of detection of individual GSL species and is highlighted as a versatile analytical tool for glycolipidomic studies.
Figure
Automatic LC/MALDI MS profiling of glycosphingolipids
Mostafa Zarei and Stephan Kirsch contributed equally to this work. 相似文献
997.
Milutin Dostanić 《Journal d'Analyse Mathématique》2008,104(1):13-23
It is shown that the Berezin transform B on L
p
(D), where D is the unit disc, has norm
. Furthermore, the norms of a family of operators (on L
p
(D)) whose kernels are moduli of Bergman type kernels are also calculated.
Partially supported by MNZZS, Grant
ON144010 相似文献
998.
Miroslav Pavlović 《Mathematische Zeitschrift》2008,258(1):81-86
We prove that maps into
if and only if belongs to . In the case β < 1, we give another two equivalent conditions.
Supported by MNZŽS Serbia, Project No. ON144010. 相似文献
999.
Friscić T Fábián L Burley JC Reid DG Duer MJ Jones W 《Chemical communications (Cambridge, England)》2008,(14):1644-1646
Comparison of structure and hydration stability of pairs of chiral and racemic binary cocrystals indicates that the racemic solid is more stable than the chiral one; we illustrate that this difference might arise from intermolecular (crystal packing) factors in one case, while intramolecular (molecular conformation) factors are more significant in the other. 相似文献
1000.
Telalović S Ng JF Maheswari R Ramanathan A Chuah GK Hanefeld U 《Chemical communications (Cambridge, England)》2008,(38):4631-4633
Synergy between Br?nsted acid sites and Lewis acid sites in mesoporous Al-Zr-TUD-1 was demonstrated to exist in Br?nsted acid catalysed reactions, but not in Lewis acid catalysed reactions. 相似文献