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991.
Li Liu Ling‐Xiang Qiao Shi‐Zhong Liu Dong‐Mei Cui Chun‐Mei Zhang Zheng‐Ji Zhou Zu‐Liang Du Wai‐Yeung Wong 《Journal of polymer science. Part A, Polymer chemistry》2008,46(10):3193-3206
A new family of organometallic/inorganic composite Langmuir‐Blodgett (LB) films consisting of rigid‐rod polyplatinayne polymer ([Pt‐T(OMe‐Fl)T]∞ or [Pt‐T(F‐Fl)T]∞, where the triplet bonds are abbreviated by T, and fluorene ring by Fl) as the π‐conjugated organometallic molecule, polyoxometalate (POM, POM = K3PMo12O40, H3PW12O40, or H6P2W18O62) of the Keggin and Dawson structures as the inorganic component, and dimethyldioctadecylammonium bromide (DODA) or a mixture of octadecanoic acid (OA) and docosanoic acid (DA) as the auxiliary film‐forming agent were prepared and characterized by π–A isotherms, UV–Vis absorption spectra, photoluminescence spectra, atomic force microscopy imaging, scanning tunneling microscopy, and low‐angle X‐ray diffraction. Our experimental results indicate that steady, even, and ordered Langmuir and LB films are formed in pure water and polyoxometalate subphases. It was shown that the POM molecules are probably embedded inside the polyplatinayne molecules in the LB film structure and they can quench the luminescence of the Pt polyyne. These Pt‐polyyne based LB films display interesting electric conductivity behavior. [Pt‐T(OMe‐Fl)T]∞/DODA/HPW12 monolayer film shows a good electrical conductivity, and the tunneling current amounts to ±100 nA when the voltage is set at ±8 V. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3193–3206, 2008 相似文献
992.
Cortlandt G. Pierpont 《Journal of Chemical Sciences》2002,114(4):247-254
The properties of transition metal complexes containing catecholate and radical semiquinonate ligands have often been found
to be unusual and unexpected. Crystals of Rh(CO)2(3,6-DBSQ), containing the 3,6-di-tert-butyl-1,2-semiquinonate ligand, form as long thin needles that are observed to bend
reversibly upon irradiation with NIR light. Crystallographic characterization reveals a stacked solid state lattice with planar
molecules aligned with metal atoms atop one another. Electronic spectra recorded in the solid state and in solution show an
intense band at 1600 nm that maps the energy dependence of crystal bend angle. The transition is a property of the stacked
assembly, rather than of an individual complex molecule, and appears associated with an MLCT process that transfers charge
from an antibonding band formed by interacting Rhd
z
2
orbitals to the vacant quinone π* orbital. Related observations have been made on the [Co(μ-pyz)(3,6-DBSQ)(3,6-DBCat)]npolymer. Photomechanical properties appear associated with electronic transitions that lead to a physical change in axial
length of a linear polymer, coupled with a soft solid state lattice that permits axial contraction/expansion without crystal
fracture. 相似文献
993.
Nobuo Yoshida 《Journal of statistical physics》2008,133(6):1033-1058
We consider a discrete-time stochastic growth model on d-dimensional lattice. The growth model describes various interesting examples such as oriented site/bond percolation, directed
polymers in random environment, time discretizations of binary contact path process and the voter model. We study the phase
transition for the growth rate of the “total number of particles” in this framework. The main results are roughly as follows:
If d≥3 and the system is “not too random”, then, with positive probability, the growth rate of the total number of particles is
of the same order as its expectation. If on the other hand, d=1,2, or the system is “random enough”, then the growth rate is slower than its expectation. We also discuss the above phase
transition for the dual processes and its connection to the structure of invariant measures for the model with proper normalization.
Supported in part by JSPS Grant-in-Aid for Scientific Research, Kiban (C) 17540112. 相似文献
994.
Fareha Zafar Khan Masashi Shiotsuki Fumio Sanda Yoshiyuki Nishio Toshio Masuda 《Journal of polymer science. Part A, Polymer chemistry》2008,46(7):2326-2334
The amino acid esters of hydroxypropyl cellulose (HPC) [R′ = H ( 2a ), CH3 ( 2b ), CH2CH(CH3)2 ( 2c ), CH2CONH2 ( 2d ), CH2CH2CONH2 ( 2e ), CH2CH2CH2CH2 NHOCOC(CH3)3 ( 2f )] were synthesized in good yield by the reaction of t‐butoxycarbonyl (t‐Boc)‐protected amino acids with hydroxy groups of HPC ( 1 ; molar substitution (MS), 4.61). The amino acid functionalities displaying varied chemical nature, shape, and bulk were utilized and the bulk of the substituent on the α‐carbon of amino acids was elucidated to be of vital significance for the observed degree of incorporation (DSEst). The 1H NMR spectra and elemental analysis were employed to determine the degree of incorporation of amino acid moiety (DSEst) and almost complete substitution of the hydroxy protons was revealed for 2a , 2b , and 2f . The presence of the peaks characteristic of the carbonyl group in the FTIR spectra furnished further evidence for the successful esterification of HPC. The starting as well as the resulting polymers ( 1 and 2a – f ) were soluble in polar organic solvents; however, the esterification of 1 with bulky organic moieties resulted in an increased hydrophobicity as all of the amino acid‐functionalized polymers ( 2a – f ) were insoluble in water. The onset temperatures of weight loss of 2a – f were 175–230 °C, indicating fair thermal stability. The amino acid functionalization led to the enhanced polymer chain stiffness, and the glass transition temperatures of the derivatized polymers were 30–40 °C higher than that of 1 (Tg 3.9 °C; cf. Tg of 2a – f , 35.1–43.3 °C). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2326–2334, 2008 相似文献
995.
The non-thermal phase transition in high energy collisions is studied in detail in the framework of random cascade model.
The relation between the characteristic parameter Ap, of phase transition and the rank q of moment is obtained using Monte Carlo simulation, and the existence of two phases in
self-similar cascading multiparticle systems is shown. The relation between the critical point qc of phase transition on the
fluctuation parameter a is obtained and compared with the experimental results from NA22. The same study is carried out also
by analytical calculation under central limit approximation. The range of validity of the central limit approximation is discussed. 相似文献
996.
Nickel chloride was excited in a high frequency discharge source and the band at 3664 Å was photographed at an inverse dispersion of 0.59 Å/mm on a two metre plane grating spectrograph. The rotational analysis was carried out and the molecular constants of the upper state are reported. The rotational isotopic shifts due to37Cl support the rotational analysis. The electronic transition involved is identified to beβ 2Δ5/2 →X 1 2Δ5/2. 相似文献
997.
Tamotsu Hashimoto Yusuke Makino Michio Urushisaki Toshikazu Sakaguchi 《Journal of polymer science. Part A, Polymer chemistry》2008,46(5):1629-1637
Living cationic polymerization of 2‐adamantyl vinyl ether (2‐vinyloxytricyclo[3.3.1.1]3,7decane; 2‐AdVE) was achieved with the CH3CH(OiBu)OCOCH3/ethylaluminum sesquichloride/ethyl acetate [CH3CH(OiBu)OCOCH3/Et1.5AlCl1.5/CH3COOEt] initiating system in toluene at 0 °C. The number‐average molecular weights (Mn's) of the obtained poly(2‐AdVE)s increased in direct proportion to monomer conversion and produced the polymers with narrow molecular weight distributions (MWDs) (Mw/Mn = ~1.1). When a second monomer feed was added to the almost polymerized reaction mixture, the added monomer was completely consumed and the Mn's of the polymers showed a direct increase against conversion of the added monomer. Block and statistical copolymerization of 2‐AdVE with n‐butyl vinyl ether (CH2?CH? O? CH2 CH2CH2CH3; NBVE) were possible via living process based on the same initiating system to give the corresponding copolymers with narrow MWDs. Grass transition temperature (Tg) and thermal decomposition temperature (Td) of the poly(2‐AdVE) (e.g., Mn = 22,000, Mw/Mn = 1.17) were 178 and 323 °C, respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1629–1637, 2008 相似文献
998.
999.
1000.
V. Renugopalakrishnan G. Madrid G. Cuevas A. T. Hagler 《Journal of Chemical Sciences》2000,112(1):35-42
Density functional theory was applied to the calculation of molecular structures of N-methyl formamide (NMF), N,N-dimethyl
formamide (DMF), and N,N-dimethyl acetamide (DMA). DFT calculations on NMF, DMF, and DMA were performed using a combination
of the local functional of Vosko, Wilk, and Nusair (VWN) with the nonlocal exchange functional of Becke and the nonlocal correlational
functional of Lee, Yang, and Parr (BLYP). The adiabatic connection method (ACM) of Becke has also been used, for the first
time, for the calculation of molecular structures of NMF, DMF, and DMA. The calculated molecular structures are in excellent
agreement with the experimental geometries of NMF and DMA derived from gas-phase electron-diffraction studies. Sparse experimental
data on the gas-phase geometry of DMF reported in the literature compares well with the DFT results on DMF. DFT emerges as
a powerful method to calculate molecular structures. 相似文献