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991.
Hanmura T Ichihashi M Monoi T Matsuura K Kondow T 《The journal of physical chemistry. A》2005,109(29):6465-6470
The reaction process of the production of CrOH(C2H4)2(+) was studied in connection with the ethylene polymerization on a silica-supported chromium oxide catalyst (the Phillips catalyst). Cluster ions CrOH(C2H4)2(+) and CrOH(C4H8)+ were produced by the reactions of CrOH+ with C2H4 (ethylene) and C4H8 (1-butene), respectively, and were allowed to collide with a Xe atom under single collision conditions. The cross section for dissociation of each parent cluster ion was measured as a function of the collision energy (collision-induced dissociation, or CID). It was found that (i) the CID cross section for the production of CrOH+ from CrOH(C2H4)2(+) increases sharply at the threshold energy of 3.16 +/- 0.22 eV and (ii) the CID cross section for the production of CrOH+ and C4H8 from CrOH(C4H8)+ also increases sharply at the threshold energy of 3.26 +/- 0.21 eV. In comparison with the calculations based on a B3LYP hybrid density functional method, it is concluded that two ethylene molecules in CrOH(C2H4)2(+) are polymerized to become 1-butene. The calculation also shows that the dimerization proceeds via CrOH(C2H4)+ (ethylene complex) and CrOH(C2H4)2(+) (ethylene complex), in which the ethylene molecules bind with CrOH+ through a pi-bonding. 相似文献
992.
H. Ito Y. Tsutsumi K. Minagawa J. Takimoto K. Koyama 《Colloid and polymer science》1995,273(8):811-815
High pressure crystallization of polypropylene was studied by means of PVT measurements and computer simulations. The isothermal crystallization behaviour were described by using a model which takes into account the effect of pressure on the temperature dependence of nucleation rate and linear growth rate. The agreement between the simulation and the experiments was seen in the tendency that the crystallization was accelerated by the high pressure. The non-isothermal crystallization behavior was also simulated by applying a generalized Avrami equation. The simulation curves well reproduced the experimental values below relative crystallinity 0.5 and below 100 MPa. 相似文献
993.
Takehiko Terao Shiro Maeda Tokio Yamabe Kazuo Akagi Hideki Shirakawa 《Chemical physics letters》1984,103(5):347-351
13C NMR spectra of undoped polyacetylene,(CH)x, have been measured. The existence of 3.4 mol% methylene moieties as defects in the (CH)x chains has been observed in trans-(CH)x. Measurements of partially cis-to-trans isomerized (CH)x suggest the existence of isolated cis regions. 相似文献
994.
Fukuji Higashi Akira Tai Kazuo Adachi 《Journal of polymer science. Part A, Polymer chemistry》1970,8(9):2563-2577
Polymers having polyamine structures were obtained by the condensation reaction between diethyl succinylsuccinate (1,4-diethoxycarbonyl-2,5-dihydroxy-1,4-cyclohexadiene) and aliphatic diamines. The reactions were carried out in high polar solvents such as N-methylpyrrolidone (NMP) and N,N-dimethylformamide (DMF). The mode of the polymerization reaction and the structure of the polymers were verified by studies of model compounds. The polymers thus obtained were conveniently utilized as coating and adhesive materials and were able to be cast into films. 相似文献
995.
Nakane T Maeda Y Ebihara H Arai Y Masuda K Takano A Ageta H Shiojima K Cai SQ Abdel-Halim OB 《Chemical & pharmaceutical bulletin》2002,50(9):1273-1275
Two new migrated hopane triterpenoids, viz. 4alpha-hydroxyfilican-3-one and fern-9(11)-en-12beta-ol, and olean-18-en-3-one and olean-12-en-3-one as the first example of oleanane compounds from Adiantum ferns were isolated along with many other known triterpenoids from Adiantum capillus-veneris of China and Egypt. Their structures were elucidated by spectroscopic analyses. 相似文献
996.
Shozo Shibata Masamichi Furukawa Eijiro Kamata Kazuo Goto 《Analytica chimica acta》1970,50(3):439-446
The heterocyclic azo compound, 1-[(5-chloro-2-pyridyl)azo]-2-naphthol (5-Cl-β-PAN), forms various coloured metal chelates, which can be extracted with different organic solvents. Chelate stability is greatly affected by pH. The molar absorptivities are usually considerably greater than those of the β-PAN chelate. Although the bathochromic shifts produced on chelation are no greater than those with 5-Br-β-PAN, the selectivity is increased. The reactivity of tri- and tetravalent metal ions is decreased appreciably by introduction of the chlorine. A correct choice of pH, solvent and masking reagent allows 5-C1-β-PAN to be made reasonably selective. 相似文献
997.
Compaction of TiO2 suspended particles utilizing the hydrophilic/hydrophobic transition of a cationic thermosensitive copolymer of N-isopropylacrylamide (NIPAM) and N-dimethylaminopropylacrylamide (DMAPAA) was examined. The surface of suspended TiO2 particles were sufficiently covered with the adsorbed polymer molecules at room temperature, and the suspension was subsequently heated above the transition temperature of the polymer. The thrusting motion of a plunger was used in order to provide an adequate mechanical force to compact the TiO2 suspended particles. The transition temperature was dependent on the DMAPAA content in the copolymer and the pH of the suspension. The transition temperature increased with increasing DMAPAA content and decreased with increasing pH. While suspended TiO2 particles were not compacted with poly(NIPAM), hard compacted sludge was readily obtained for cationic copolymer even if the content of DMAPAA groups was as low as 0.23 mol%. Furthermore, residual polymer molecules in the supernatant were not detected even if the polymer dosage was increased. These findings were attributed to the hydrophobic interaction of thermosensitive copolymer molecules adsorbed on TiO2 particles. 相似文献
998.
N-Phenylthiomethyl derivatives of α-amino acid esters are attacked by α,β-unsaturated carboxylates in the presence of sodium hydride, undergoing 1,3-dipolar cycloaddition to give pyrrolidines. 相似文献
999.
Summary A new method for the resolution of an antisymmetrized product of molecular orbitals into VB structures is proposed. Here VB structures are projected from a single Slater determinant associated with the ground state using the first-order density matrix. The present theory is applied to the ground state of some conjugated hydrocarbons, and special attention is paid to the covalent type VB structures. 相似文献
1000.
Itoh M Watanabe K Hatakeyama M Tachibana M 《Analytical and bioanalytical chemistry》2002,372(4):532-536
An X-ray spectrometric method has been developed for the determination of 41Ca in the biological-shield concrete of nuclear reactors. The concrete sample was first decomposed with nitric, hydrofluoric, and perchloric acids. Calcium was then separated from other radionuclides by ion-exchange chromatography and recovered as an oxalate precipitate. X-rays at 3.3 keV from 41Ca in the calcium oxalate pellet were measured. The detection efficiency of the X-ray measurement at 3.3 keV was calculated from those obtained by measuring 55Fe standard pellets at 5.9 keV using mass-absorption coefficients of the calcium oxalate pellet at each X-ray energy. A lower limit of determination of 8 Bq g(-1) was obtained for a sample weight of 1 g. 相似文献