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1.
C. Z. Chuai S. Li K. Almdal J. Alstrup J. Lyngaae‐Jrgensen 《Journal of Polymer Science.Polymer Physics》2004,42(5):898-913
The compatibilization effect of polystyrene (PS)‐poly(dimethylsiloxane) (PDMS) diblock copolymer (PS‐b‐PDMS) and the effect of rheological properties of PS and PDMS on phase structure of PS/PDMS blends were investigated using a selective extraction technique and scanning electron microscopy (SEM). The dual‐phase continuity of PS/PDMS blends takes place in a wide composition range. The formation and the onset of a cocontinuous phase structure largely depend on blend composition, viscosity ratio of the constituent components, and addition of diblock copolymers. The width of the concentration region of the cocontinuous structure is narrowed with increasing the viscosity ratio of the blends and in the presence of the small amount diblock copolymers. Quiescent annealing shifts the onset values of continuity. The experimental results are compared with the volume fraction of phase inversion calculated with various theoretical models, but none of the models can account quantitatively for the observed data. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 898–913, 2004 相似文献
2.
Yuri M. Boiko Anders Bach Jørgen Lyngaae-Jørgensen 《Journal of Polymer Science.Polymer Physics》2004,42(10):1861-1867
Films of amorphous polystyrene (PS) with a weight-average molecular weight (Mw) of 225 × 103 g/mol were bonded in a T-peel test geometry, and the fracture energy (G) of a PS/PS interface was measured at the ambient temperature as a function of the healing time (th) and healing temperature (Th). G was found to develop with (th)1/2 at Th = Tg-bulk − 33 °C (where Tg-bulk is the glass-transition temperature of the bulk sample), and log G was found to develop with 1/Th at Tg-bulk − 43 °C ≤ Th ≤ Tg-bulk − 23 °C. The smallest measured value of G = 1.4 J/m2 was at least one order of magnitude larger than the work of adhesion required to reversibly separate the PS surfaces. These three observations indicated that the development of G at the PS/PS interface in the temperature range investigated (<Tg-bulk) was controlled by the diffusion of chain segments feasible above the glass-transition temperature of the interfacial layer, in agreement with our previous findings for fracture stress development at several polymer/polymer interfaces well below Tg-bulk. Close values of G = 8–9 J/m2 were measured for the symmetric interfaces of polydisperse PS [Mw = 225 × 103, weight-average molecular weight/number-average molecular weight (Mw/Mn) = 3] and monodisperse PS (Mw = 200 × 103, Mw/Mn = 1.04) after healing at Th = Tg-bulk − 33 °C for 24 h. This implies that the self-bonding of high-molecular-weight PS at such relatively low temperatures is not governed by polydispersity. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1861–1867, 2004 相似文献
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4.
Nis Halland Tore Hansen Karl Anker Jrgensen 《Angewandte Chemie (International ed. in English)》2003,42(40):4837-4837
5.
6.
Leif Kjr Jrgensen 《Journal of Graph Theory》1989,13(1):75-85
A probabilistic result of Bollobás and Catlin concerning the largest integer p so that a subdivision of Kp is contained in a random graph is generalized to a result concerning the largest integer p so that a subdivision of Ap is contained in a random graph for some sequence A1, A2,… of graphs such that Ai+1 contains a subdivision of Ai. A similar result is proved for subdivisions with odd paths or cycles. The result is applied to disprove a conjecture of Chartrand, Geller, and Hedetniemi. The maximum number of edges in a graph without a subdivision of Kp, p = 4, 5, with odd paths or cycles is determined. 相似文献
7.
The reaction of metallic aluminium surfaces, aluminium oxides, hydrated oxides and sulphate with gaseous anhydrous hydrogen fluoride was studied at 470°C and pressures between 10 and 100 torr. The complementary analytical techniques of X-ray induced photoelectron spectra, X-ray and electron diffraction, and electron microscopy were used for identifying the (frequently unexpected) products. 相似文献
8.
Andrzej Barszczewicz Michal Jaszuński Krystyna Kamieńska-Trela Trygve Helgaker Poul Jørgensen Olav Vahtras 《Theoretical chemistry accounts》1993,87(1-2):19-28
Summary
Ab initio calculations of parameters which characterize the NMR spectrum are presented for the cyclopropene molecule. The London orbitals CHF (or GIAO-CHF, Gauge-Independent Atomic Orbital Coupled Hartree-Fock) results for the shielding constants are in good agreement with the experimental data, accurately determined, and with otherab initio values. The calculations of the NMR spin-spin coupling constants have been performed using the Multiconfiguration Time-Dependent Hartree-Fock (MC TDHF) approach. Different basis sets and MC SCF wavefunctions were used to estimate the accuracy of the results. Good agreement is obtained with the coupling constants estimated using the available experimental data.Dedicated to Professor Werner Kutzelnigg on the occasion of his 60th birthday 相似文献
9.
[reaction: see text]. A simple, palladium-catalyzed method to convert aryl halides to the parent anilines using lithium bis(trimethylsilyl)amide (LiN(SiMe3)2) is reported. The reaction is catalyzed by Pd(dba)2 and P(t-Bu)3 and can be run with as little as 0.2 mol % of catalyst. The reaction is faster than competing generation of benzyne intermediates and, therefore, provides the aniline products regiospecifically. 相似文献
10.
Yasser M. Loksha Per T. Jrgensen Erik B. Pedersen Mahmoud A. El‐Badawi Ahmed A. El‐Barbary Claus Nielsen 《Journal of heterocyclic chemistry》2002,39(2):375-382
5‐Alkyl‐4‐benzyl‐1,3‐dihydroimidazol‐2‐ones ( 3a‐d ) and 5‐alkyl‐4‐benzyl‐1,3‐dihydroimidazole‐2‐thiones (7a‐d) were prepared via Dakin West reaction on DL‐phenylalanine with the appropriate aliphatic acid anhydrides followed by hydrolysis and reaction with potassium cyanate or potassium thiocyanate. Compounds 3a‐d were alkylated with ethoxymethyl chloride to give the alkylated imidazoles 5a‐d which were considered analogues of Emivirine with deletion of carbonyl group at the 4‐position. Alkylation of 7a‐d afforded the corresponding S‐alkylated derivatives 8a‐p which in a similar way were considered analogues of S‐DABO. However all the imidazole derivatives were devoid of activity against HIV. 相似文献