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991.
Ju‐Young Kim Chan‐Ho Kim Duck‐Joe Yoo Kyung‐Do Suh 《Journal of Polymer Science.Polymer Physics》2000,38(14):1903-1916
Tailor‐made urethane acrylate anionomer (UAA) chains show higher viscosity and polyelectrolyte behavior in dimethyl sulfoxide (DMSO) than in water and toluene. Water is a nonsolvent for the hydrophobic soft segment but a good solvent for the hydrophilic hard segments, so hydrophobic segments are aggregated and form particles in the water phase, resulting in a smaller viscosity. Also, the fact that the viscosity of UAA chains is lowest in toluene can be interpreted as a result of ionic aggregation due to the nonpolarity of toluene. The structures of UAA networks dramatically change with the nature of the solvents used (i.e., the interaction between the UAA chains and the solvents used changes); this is confirmed by the results of tensile property, morphology, and wide‐angle X‐ray scattering data. Ionic aggregation formed in UAA/toluene (UATG networks) and hydrophobic aggregation formed in UAA/water (UAAG networks) are locked in by a chemical crosslinking reaction and result in a greater modulus and X‐ray scattering intensity. The greater elongation and swelling ratio in methylene chloride of UATG networks prepared in a UAA/toluene solution indicates that toluene is a better solvent than DMSO for the hydrophobic segments of UAA chains. Also, the greater swelling ratio in a pH 11 buffer solution and greater modulus of UAAG networks show that water is a better solvent than DMSO for hydrophilic ionic segments. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1903–1916, 2000 相似文献
992.
Young Joo Lee Jae Yeol Maeng Eok‐Kyun Lee Bongsoo Kim Sehun Kim Kyu‐Kwang Han 《Journal of computational chemistry》2000,21(5):380-387
We present an atom‐resolved analysis method that traces physical quantities such as the root‐mean‐square bond length fluctuation and coordination number for individual atoms as functions of temperature or time. This method is applied to explain the temperature‐dependent behaviors of three types of NiN (N=12,13,14) clusters. The detailed studies for the three types of clusters reveal characteristics as follows: (a) as the temperature increases, all three types of clusters undergo two‐stage melting, irrespective of the existence of vacancy or adatom on the icosahedral surfaces, (b) the melting of icosahedral clusters with vacancy starts with vacancy hopping, which has not been observed for any type of small clusters (N<34), (c) the melting of the icosahedral clusters with adatom (N=14) is initiated by adatom hopping, followed by the site exchange between the adatom and surface atoms. © 2000 John Wiley & Sons, Inc. J Comput Chem 21: 380–387, 2000 相似文献
993.
994.
Fabrication of superhydrophobic surface from a supramolecular organosilane with quadruple hydrogen bonding 总被引:5,自引:0,他引:5
A supramolecular organosilane, 2-(3-(triethoxysilyl)propylaminocarbonylamino)-6-methyl-4[1H]pyrimidinone comprising quadruple hydrogen bonds has been synthesized in one step from commercially available starting materials. The synthesized supramolecular organosilane can be stabilized and phase-separated by dimerization via the linear array of quadruple hydrogen bonds in solution. This property of the supramolecular organosilane has been exploited to fabricate structuring materials having a superhydrophobic surface property. We have successfully generated the interconnected granular structure with adequate roughness for superhydrophobicity via sol-gel process. 相似文献
995.
Hong YS Lee D Kim W Jeong JK Kim CG Sohng JK Lee JH Paik SG Lee JJ 《Journal of the American Chemical Society》2004,126(36):11142-11143
The post-polyketide synthase modification of geldanamycin (1) biosynthesis is of interest as a means of introducing structural diversity into the compound. From the inactivation of a gene encoding carbamoyltransferase, we demonstrated that the C-17 hydroxylation and the C-21 oxidation precede O-carbamoylation and that the hypothetical progeldanamycin does not possess a double bond at C-4 and C-5. More importantly, our result revealed new intermediates 4,5-dihydro-7-O-descarbamoyl-7-hydroxygeldanamycin (3) and 4,5-dihydrogeldanamycin (5), indicating that O-carbamoylation occurs prior to the C-4,5 cis double bond formation in geldanamycin biosynthesis. 相似文献
996.
Deep Eutectic Solvent-Based HS-SME Coupled with GC for the Analysis of Bioactive Terpenoids in Chamaecyparis obtusa Leaves 总被引:1,自引:0,他引:1
Headspace-solvent microextraction (HS-SME) was developed as a solvent-minimized extraction technique, but few studies have examined the applications of deep eutectic solvents (DESs) to the HS-SME of bioactive compounds. In this study, HS-SME was developed for the extraction of bioactive compounds using DESs as extraction solvents. DESs, which were prepared by mixing choline chloride (ChCl) with ethylene glycol (EG) at different ratios, were applied to the extraction of three terpenoids from Chamaecyparis obtusa leaves by HS-SME. The ChCl/EG ratio in the DESs, HS-SME conditions, such as the extraction temperature and extraction time, and sample/DES ratio were optimized. All extracts were analyzed by GC. Under optimized conditions, the limits of detection were 2.006 ng mL?1 for linalool, 3.150 ng mL?1 for α-terpineol and 2.129 ng mL?1 for terpinyl acetate. The relative standard deviations were in the range of 2.1–6.8 %. The recoveries of the three terpenoids were in the range of 79.4–103 %. HS-SME is simple and rapid compared to heat reflux extraction and ultrasonic extraction. Moreover, DESs can be used in HS-SME for the extraction of a range of bioactive and volatile compounds. 相似文献
997.
JIN Yin-zhe ROW Kyung Ho 《高等学校化学研究》2007,23(4):412-416
A molecular imprinted polymer(MIP)was prepared with quercetin as the template and methacrylic acid(MAA)as the functional monomer.Acetonitrile and methanol were used as the porogen with ethylene glycol dimethacrylate(EGDMA)as the crosslinker and 2,2'-azobis(isobutyronitrile)(AIBN)as the initiator.The experimental parameters of the equilibrium isotherms were estimated via linear and nonlinear regression analyses.The linear equation as the functions of the adsorption concentration of the single compound in its solution and the competitive adsorption of the single compound in its mixed compounds solution was then expressed,and the adsorption equilibrium data were correlated to Langmuir and Freundlich isotherm models.The mixture compounds show competitive adsorption on the specific binding sites of quercetin-MIP.Furthermore,the competitive Langmuir isotherms were applied to the mixture compounds.The adsorption concentrations of quercetin,( )catechin( C),and(-)epicatechin(EC)on the quercetin molecular imprinted polymer were compared.The quercetin-imprinted polymer shows extraordinarily higher adsorption ability for quercetin than for the two catechin compounds that were also assessed. 相似文献
998.
Jin‐Woong Kim Jung‐Eun Lee Jee‐Hyun Ryu Jong‐Suk Lee Su‐Jin Kim Sang‐Hoon Han Ih‐Seop Chang Hak‐Hee Kang Kyung‐Do Suh 《Journal of polymer science. Part A, Polymer chemistry》2004,42(10):2551-2557
A new colloidal silver system is presented in which a fine colloidal silver is in situ deposited onto functionalized porous poly(ethylene glycol dimethacrylate) [poly(EGDMA)] microspheres. The effectiveness of the silver deposition has been investigated through an examination of the surface characteristics of poly(EGDMA) microspheres. The result reported in this study demonstrate that the control of the surface area and surface functionality (in this study, a hydroxyl group) of poly(EGDMA) microspheres is an important factor that practically determines the degree of deposition of colloidal silver. X‐ray analysis has shown that silver nanoparticles are dispersed evenly on inner and outer surfaces and have a face center cubic phase. Preservation testing has shown that silver‐containing poly(EGDMA) microspheres have powerful antibacterial properties and, therefore, have significant potential as new preservatives. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2551–2557, 2004 相似文献
999.
Joo D. L. Laboy J. Kolomeisky A. Zhuo Q. Clouthier D. J. Chan C. P. Merer A. J. Judge R. H. 《Journal of Molecular Spectroscopy》1995,170(2)
High-resolution infrared spectra of the low-lying ν3, ν4, and ν5 fundamentals of the transient molecule DCOCl are reported. These type-A/B hybrid bands have been analyzed in detail, providing extensive rotational assignments for the DCO35Cl and DCO37Cl isotopomers. The ground state constants have been refined by a simultaneous fit of the available microwave data and FTIR combination differences from the three bands. The excited state constants have been determined by fitting assignments over a wide range of J and Ka values. A small perturbation was found at high Ka values in the ν4 band and determined to be due to a ΔKa = −2 interaction with the rotational levels of the 61 vibrational state. 相似文献
1000.
Mai Ha Hoang Myung Hee Kim Min Ju Cho Kyung Hwan Kim Kyu Nam Kim Jung‐Il Jin Dong Hoon Choi 《Journal of polymer science. Part A, Polymer chemistry》2008,46(15):5064-5076
We synthesized new nonlinear optical (NLO) chromophores containing a 3,5‐bis(3,5‐bisbenzyloxy‐benzyloxy)‐benzoate dendron. Tricyanopyrroline (TCP)‐based chromophores were designed and prepared by virtue of its strong electron withdrawing property. A soluble polyimide containing 6‐({4‐[2‐(1‐allyl‐4‐cyano‐5‐dicyanomethylene‐2‐oxo‐2,5‐dihydro‐1H‐pyrrol‐3‐yl)‐vinyl]‐phenyl}‐butyl‐amino)‐hexanoyl group in the side chain was also prepared as an NLO active host polymer. A benzoate dendron was tethered at two different binding positions of the chromophore to yield two different guest molecules. Thin‐film composites of these dendronized chromophores dissolved in the NLO active polyimide host were employed to fabricate the electro‐optic (EO) samples. The EO properties of new NLO polyimides containing dendronized chromophores were compared with those of the sample with nondendronized plain chromophores. The effect of a bulky dendron on the EO properties was investigated using an in situ reflection technique. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5064–5076, 2008 相似文献