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61.
F. Vanderbist P. Leleux C. Angulo E. Casarejos M. Couder M. Loiselet G. Ryckewaert P. Descouvemont M. Aliotta T. Davinson Z. Liu P. J. Woods 《The European Physical Journal A - Hadrons and Nuclei》2006,27(2):183-186
The 15O(α,α)15O elastic scattering is investigated using a 15O radioactive beam and a He gas cell limited by Mylar windows. The width of a 19Ne state at an excitation energy of 5.35MeV is measured as Γα = 3.2±1.6keV, in agreement with charge symmetry estimate. 相似文献
62.
Ying Xia Sheng Feng Zhen Liu Yan Zhang Jianbo Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(27):8002-8005
A RhI‐catalyzed three‐component reaction of tert‐propargyl alcohol, diazoester, and alkyl halide has been developed. This reaction can be considered as a carbene‐involving sequential alkyl and alkynyl coupling, in which C(sp) C(sp3) and C(sp3) C(sp3) bonds are built successively on the carbenic carbon atom. The RhI‐carbene migratory insertion of an alkynyl moiety and subsequent alkylation are proposed to account for the two separate C C bond formations. This reaction provides an efficient and tunable method for the construction of all‐carbon quaternary center. 相似文献
63.
A New and Facile Synthesis of Novel Pyrazolothienopyrimidines and Imidazopyrazolothienopyrimidines
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4‐Amino‐3‐methyl‐1‐phenyl‐1H‐thieno[2,3‐c]pyrazole‐5‐carboxamide ( 5 ), which was synthesized by an innovative method, was used as a versatile precursor for synthesizing pyrazolothienopyrimidines and imidazopyrazolothienopyrimidines compounds. Reaction of amino thienopyrazole carboxamide 5 with triethyl orthoformate afforded thienopyrazolopyrimidine 6 . Chlorination of the latter compound, using phosphorus oxychloride afforded the chloro pyrazolothienopyrimidine 7 , which underwent nucleophilic substitution reactions with various primary and secondary amines to give the alkyl (aryl) amino pyrimidine compounds 8a–d . On the other hand, the reaction of chloropyrimidine 7 with thiourea afforded the pyrimidine thione compound 9 , which was alkylated with α‐halogentaed compounds to afford the S‐alkylated derivatives 10a–c . Also, chloroacetylation of the amino carboxamide 5 using chloroacetyl chloride yielded the chloromethyl pyrazolothienopyrimidine 12 , which underwent nucleophilic substitu‐ tion reactions with various primary and secondary amines to afford the alkyl (aryl) aminomethyl compounds 13a–f . The latter Compounds underwent Mannich reaction to give imidazopyrimidothieno‐ pyrazoles 14a–c . The newly synthesized compounds and their derivatives were fully characterized by elemental and spectral analysis. 相似文献
64.
In this account, we provide a brief summary of recent developments in ruthenium‐catalyzed metathesis cascade reactions towards the total synthesis of natural products. We also highlight recent progress from our own laboratory regarding the synthesis of securinega alkaloids and humulanolides, which has resulted in the development of novel ruthenium‐catalyzed metathesis cascade reactions. Inspired and guided by the pioneering and elegant research conducted in this area, we developed a regio‐controlled relay dienyne metathesis cascade reaction and a cyclobutene‐promoted RCM/ROM/RCM cascade reaction for the synthesis of securinega alkaloids and humulanolides, respectively. 相似文献
65.
Aurélie BlondRoba Moumné Guillaume BégisMorgane Pasco Thomas Lecourt Laurent Micouin 《Tetrahedron letters》2011,52(25):3201-3203
Rhodium(II)-catalyzed decomposition of carbene precursors grafted to the alcohol of diaminocyclopentanols promotes clean formation of a C-N bond via 1,6-insertion into an adjacent carbamate or azide. These modifications of 2-deoxystreptamine surrogates might give rise to aminoglycoside mimics where the two nitrogen atoms will be differentiated. 相似文献
66.
Zhenwei Zhang 《Journal of organometallic chemistry》2011,696(24):3852-3860
The detailed mechanism for arylation of styrene or its α-CF3 substituted analog using aryliron complex [CpFe(CO)2Ar] was studied using density functional theory calculations. Results of calculations show that the arylation mechanism mainly involves three steps: (1) a ligand exchange process between a CO and styrene or its derivative; (2) migration of Ar group from Fe to β-C of styrene; (3) β-H (or β-F) elimination and dissociation of the stilbene derivative from the CpFeHCO (or CpFeFCO) moiety. Both of Steps (2) and (3) experience a similar four-memberred cyclic transition state. The dπ-pπ interaction stabilizes the CC π coordinated complexes and the agostic interaction plays an important role in stabilizing intermediates and promoting elimination of the β-H (or β-F if available). For arylation of the α-CF3 substituted styrene, our calculations clarified that the dissociation of ethylene derivatives to give PF (product for β-F elimination) is kinetically and thermodynamically more favorable than to give PH (product for β-H elimination), which is the determined step for the selectivity of the final products. 相似文献
67.
Adinarayana Doddi Rüdiger W. Seidel Roland A. Fischer 《Journal of organometallic chemistry》2011,696(13):2635-2640
Reactions of the sterically bulky mono-valent group 13 bisimidinate gallium(I), Ga(DDP) (1) (DDP = 2-{(2, 6-diisopropylphenyl)amino}-4-{(2, 6-diisopropylphenyl)imino}-2-pentene, HC(CMeNC6H3-2,6-iPr2)2) with olefin supported group 10 complexes, [(diene)PtCl2] [diene = 1,5-cyclooctadiene (COD), endo-dicyclopentadiene (dcy)] and [(COD)Pd(Me)(OTf)] (OTf = O3SCF3) are reported. These reactions afforded [(COD)Pt(Cl){ClGa(DDP)}] (2), [(dcy)Pt(Cl){ClGa(DDP)}] (3) and [(DDP)Ga(Me)(OTf)] (4) in moderate yields. Compounds 2-4 were characterized by elemental analysis, NMR (1H, 13C) spectroscopy and also by single crystal X-ray structural analysis. The solid state structures of complexes 2 and 3 reveal the oxidative insertion of Ga(DDP) into the Pt-Cl bond without altering the π-coordinated double bonds in the olefin. 相似文献
68.
H. Iwasaki T. Motobayashi H. Akiyoshi Y. Ando N. Fukuda H. Fujiwara Zs. Fülöp K. I. Hahn Y. Higurashi M. Hirai I. Hisanaga N. Iwasa T. Kijima A. Mengoni T. Minemura T. Nakamura M. Notani S. Ozawa H. Sagawa H. Sakurai S. Shimoura S. Takeuchi T. Teranishi Y. Yanagisawa M. Ishihara 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):55-58
Experimental studies on in-beam γ-ray spectroscopy using a 12Be radioactive beam are presented. Inelastic scattering of the neutron-rich 12Be nucleus on 208Pb, 12C, and (CH2)n targets has been studied by measuring de-excitation γ-rays in coincidence with scattered particles. The level schemes and
transition probabilities are determined for low-lying excited states in 12Be. The present paper presents a brief review of the spectroscopic results, which may be associated with the N = 8 shell quenching near the drip line.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
69.
The study of excited 55Mn levels with the 52Cr(α, pγ) reaction was extended to levels up to 3161 keV. With a Ge(Li) detector, DSA measurements in gold-backed targets were made, as well as angular correlations; both of these experiments were done in coincidence with protons detected near 180°. A multiple-detector NaI(Tl) array was also used in the same reaction geometry for better γ-ray detection efficiency. Mean lifetimes of 12 levels from 2727 to 3161 keV are reported. Spins and sometimes parities of the following levels were deduced from the angular-correlation analyses and lifetime results: 1885 keV, ?; 2199 keV, (?); 2311 keV, (); 2366keV, ?; 2727 keV, ; 2823 keV, . Multipole mixing ratios and M1 and E2 transition rates of the radiations from these and from the 1292 keV level are presented. The similarity of the low-lying level structure and of interlevel transitions in 55Mn to those in certain other f3 nuclei is examined. 相似文献
70.
A “Coulomb-modified” dispersion relation is applied to low-energy p-4He forward elastic scattering. To check the validity of the modification, the results are compared with those deduced from n-4He elastic scattering. Completely analogous information is obtained for the two processes. The exchange of three bound nucleons is found to contribute strongly to N-4He forward scattering. The corresponding 4He-3H-p and 4He-3He-n coupling constants are evaluated as Rp = 3.8±0.3 and Rn = 3.0±0.3, respectively. These constants are related to the strength of the asymptotic wave function of nucleons in 4He and thus to the tail of the nucleon distribution. A comparison of Rp with the empirical proton distribution in 4He as deduced from e-4He elastic scattering shows excellent agreement. From Rp and Rn the effective ranges of the singlet 3H-p and 3He-n interactions in the ground state of 4He are determined to be equal, in accordance with charge symmetry, and to have a value of reff = 1.072±0.006 fm. 相似文献