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991.
Substituted 2-halomethyl-2,3-dihydrobenzofurans were synthesized in one pot and in mild yield from substituted o-allylphenols with diacetoxyiodobenzene in the presence of 12 or Br2 in dry CH2Cl2 under reflux. 相似文献
992.
Wing Hong Chan Albert Wai Ming LeeYiu Sing Lam Jian Zhong Lu 《Microchemical Journal》2002,72(2):201-207
A fast responsive sodium ion selective fluorescent optode membrane mounted on an optical fiber has been developed. The sensing membrane contained fluorescein octadecyl ether octadecyl ester (FODEE), potassium tetrakis(4-chlorophenyl) borate (KTpClPB) and a calix[4]arene tetraester in a plasticized poly(vinyl chloride) (PVC) matrix. It exhibited a reversible response to Na+ in 0.5 mol/l of HCl in the concentration range of 1.0×10−6 to 0.1 mol/l. The selectivity, response time, reproducibility and lifetime of the optode membrane were discussed. The practical use of this sensor was demonstrated by real sample analysis in complex sample solutions such as beverage and urine samples. 相似文献
993.
Xiao‐Lin Wang Yan‐Dong He Li‐Yan You Zhong‐Yuan Lu Ze‐Sheng Li 《Journal of Polymer Science.Polymer Physics》2009,47(4):353-365
Dissipative particle dynamics simulations are applied to investigate the monolayer and multilayer film formations on different solid substrates by physical deposition. The influences of the polymer concentration, the polymer chain length, the solvent quality, and the interactions between the polymer solution and the solid substrate surface on the film formation dynamics and the mechanism are studied in detail. The results are analyzed in terms of the thickness and the shape of the deposited film, the kinetics of phase separation in the polymer solution, and the contact angle formed between the polymer aggregations and the substrate surface. Moreover, we suggest two strategies, designing a deposition process analogous to “chemical titration” and physically blocking interlayer diffusion by a simple crosslinked network barrier, to deposit the compact monolayer and multilayer films with better quality, respectively. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 353–365, 2009 相似文献
994.
Fang Lu Xiu‐Li Wang Si‐Chong Chen Ke‐Ke Yang Yu‐Zhong Wang 《Journal of polymer science. Part A, Polymer chemistry》2009,47(20):5344-5353
Starch and poly(p‐dioxanone) (PPDO) are the natural and synthetic biodegradable and biocompatible polymers, respectively. Their copolymers can find extensive applications in biomedical materials. However, it is very difficult to synthesize starch‐graft‐PPDO copolymers in common organic solvents with very good solubility. In this article, well‐defined polysaccharides‐graft‐poly(p‐dioxanone) (SAn‐PPDO) copolymers were successfully synthesized via the ring‐opening polymerization of p‐dioxanone (PDO) with an acetylated starch (SA) initiator and a Sn(Oct)2 catalyst in bulk. The copolymers were characterized via Fourier transform infrared spectroscopy, 1H NMR, gel permeation chromatography, thermogravimetric analysis (TG), differential scanning calorimetry, and wide angle x‐ray diffraction. The in vitro degradation results showed that the introduction of SA segments into the backbone chains of the copolymers led to an enhancement of the degradation rate, and the degradation rate of SAn‐PPDO increased with the increase of SA wt %. Microspheres with an average volume diameter of 20 μm, which will have potential applications in controlled release of drugs, were successfully prepared by using these new copolymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5344–5353, 2009 相似文献
995.
Yang‐Fei Zhang Shu‐Lin Bai Xiong‐Kui Li Zhong Zhang 《Journal of Polymer Science.Polymer Physics》2009,47(10):1030-1038
The viscoelastic properties of the epoxy filled with silica nanoparicles have been investigated by dynamic nanoindentation and characterized by the storage modulus and loss tangent. The materials studied are neat epoxy and silica/epoxy composites with silica volume fraction of 1, 3, 6, 10, and 14 vol %, respectively. The silica nanoparticles with an average diameter of 25 nm are found to disperse homogeneously in the epoxy matrix. The effect of the particle content, force frequency, and penetration load on the viscoelastic behavior is studied and discussed. The comparison with traditional testing methods such as tension, bending, and DMTA is made. Besides, theoretical results by using micromechanics models are also obtained and compared with the experimental results. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1030–1038, 2009 相似文献
996.
Hong‐Sheng Xu Xiujuan J. Dai Peter R. Lamb Zhong‐Ming Li 《Journal of Polymer Science.Polymer Physics》2009,47(23):2341-2352
Poly(L ‐lactide) (PLLA)/multiwall carbon nanotube (MWNT) composites were prepared by the solvent‐ultrasonic‐casting method. Only very low concentrations of MWNTs (<0.08 wt %) were added in the composites. Isothermal and nonisothermal crystalline measurements were carried out on PLLA/MWNT composites to investigate the effect of MWNTs on PLLA crystalline behavior. DSC results showed that the incorporation of MWNTs significantly shortened the crystalline induction time and increased the final crystallinity of the composite, which indicated MWNTs have a strong nucleation effect on PLLA even at very low concentrations. The nonisothermal crystallization measurements showed that the MWNTs greatly speed up crystallization during cooling. From isothermal crystallization results, both PLLA and PLLA/MWNT composites samples closely followed a relationship based on Lauritzen‐Hoffman theory, with the regime II to III transition shifting to lower temperature with increasing MWNT concentration. A double melting peak appeared in both nonisothermal and isothermal measurements. The conditions under which it appeared were found to closely depend on the regime II‐III transition temperature obtained from Lauritzen‐Hoffman theory. From the magnitude and position of melting peaks, it is proposed that the double melting peak is caused by a disorder‐order crystal phase transition. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2341–2352, 2009 相似文献
997.
998.
Yali Fu Jingchang Zhang Zhong Huang Xiuyu Wang Yuguang Lv Weiliang Cao 《Journal of photochemistry and photobiology. A, Chemistry》2008,197(2-3):329-334
Four ternary complexes of Tb(III) were synthesized by introducing the first ligand (L1) (N-phenylanthranilic acid (N-HPA), α-furoic acid (FURA)) and the second ligand (L2) (1,10-phenanthroline (Phen), 2,2′-dipyridyl (Bipy)), respectively. These complexes were characterized by elemental analysis, infrared spectra, XRD, UV spectra and fluorescence spectra. The effect of L1 and L2 on the fluorescence properties of terbium complexes was discussed. It showed that all the complexes exhibited ligand-sensitized green emission. The fluorescent intensity increased in the sequence of Tb(FURA)3Bipy < Tb(N-PA)3Phen < Tb(FURA)3Phen < Tb(N-PA)3Bipy. It indicated that L1 affected fluorescence properties of the complexes differently when the corresponding L2 altered. Meanwhile, the influence of L2 on the luminescence properties of the complexes also depends on L1. The results showed that L1 and L2 affected each other and worked together as a whole. The matching of L1, L2 and Tb3+ ion is very important to the luminescence properties of Tb(III) ternary complexes. 相似文献
999.
We consider the evolution of a black hole involving an f(R) global monopole based on the Extended Uncertainty Principle (EUP). The black hole evolutions refer to the instability due to the Parikh-Kraus-Wilczeck tunneling radiation or fragmentation. It is found that the EUP corrections make the entropy difference larger to encourage the black hole to radiate more significantly. We also show that the appearance of the EUP effects results in the black hole's division. The influence from the global monopole and the revision of general relativity can also adjust the black hole evolution simultaneously but cannot change the final result that the black hole will not be stable because of the EUP's effects. 相似文献
1000.
Syntheses,Structures, and Photophysical Properties of Two Coordination Polymers Based on 2,3‐Dioxo‐1,2,3,4‐tetrahydroquinoxaline‐6‐carboxylic Acid 下载免费PDF全文
Two complexes based on the ligand 1,4‐dihydro‐2,3‐quinoxalinedione, namely [Mn(H2L)2(H2O)2]n ( 1 ) and {[Zn2(H2L)2(tz)2] · 5H2O}n ( 2 ) (H3L = 2,3‐dioxo‐1,2,3,4‐tetrahydroquinoxaline‐6‐carboxylic acid, Htz = 1,2,4‐triazole) were hydrothermally synthesized and characterized by elemental analyses, IR spectroscopy, as well as single‐crystal and powder X‐ray diffraction. Complex 1 exhibited a 1D comb‐like chain formed by H2L– anions linking MnII ions, whereas complex 2 was a 2D layer‐like structure with square‐shaped windows and outstretched arms built by combination of H2L– and tz– ligands with ZnII ions. The adjacent chains or layers connected with each other by intermolecular hydrogen bonding and π–π stacking to further extend to a 3D supermolecular framework. In addition, the thermal stabilities, luminescence properties, and optical energy gap of 1 and 2 were investigated in detail. 相似文献