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991.
Polysiloxanes with pendant poly(ethylene oxide) side chains (4 were prepared by the dehydrocoupling reaction of poly(methylhydrosiloxane) (PMHS, 3 with 2-(2-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)ethoxy)ethanol (1 and poly(ethylene glycol) methyl ether (2 using a metal catalyst. Catalysts investigated were tin(II) 2-ethylhexanoate, Rh(Ph3P)3Cl, and Pd2(dba)3. The reaction of a cyclic siloxane, D4H, with 1 catalyzed by Pd2(dba)3 was also carried out to synthesize siloxane 6. The polysiloxanes were characterized by 1H NMR, 29Si NMR, FT-IR, and GPC. 29Si NMR study of these comb-like polysiloxanes revealed that there is a significant difference in the structure of the siloxane polymers prepared depending upon the catalyst. M, D, and T units were observed when tin(II) was used as a catalyst, but only M and D units were detected when Rh(Ph3P)3Cl or Pd2(dba)3 was employed. Furthermore, M and T units are negligible for the cyclic siloxane 3 using Pd2(dba)3. A mechanism is proposed to account for these observations. 相似文献
992.
Sabry Khalil 《Mikrochimica acta》1999,130(3):181-184
Ion-association complexes of Naphazoline HCl (I), Tolazoline HCl (II) and Xylometazoline HCl (III) with [Co(NO2)6]3– and [Fe(CN)6]3– were precipitated and the excess of the unreacted iron or cobalt comples was determined. A new method using atomic emission and atomic absorption spectrometry for the determination of the above drags in pure solutions and in pharmaceutical preparations is given. The drugs have been determined in the ranges 0.98–14.76, 0.78–11.80 and 1.12–16.80 g/ml solutions of I, II and III. respectively, using [Co(NO2)6]3–], with mean relative standard deviations of 0.4–1.5% and 1.92%–19.68, 1.52–5.68 and 2.24–22.4 g/ml solutions of I, II and III, respectively using [Fe(CN)6]3– with mean relative standard deviations of 0.6–1.6%. The recovery values of 98.12–101.26% indicate high precision and accuracy. 相似文献
993.
Khalil MM Ali SA Ramadan RM 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2001,(5):1017-1024
Reaction of Ru3(CO)12, with 2-(2'-pyridyl)benzimidazole (HPBI) resulted in the formation of Ru(CO)3(HPBI) (I) complex. In presence of pyridine or dipyridine, the two derivatives [Ru(CO)3(HPBI)].Py (II) and [Ru(CO)3(HPBI)].dpy (III) were isolated. The corresponding reactions of Os3(CO)12 yielded only one single product; Os(CO)2(HPBI)2 (IV). Spectroscopic studies of these complexes revealed intramolecular metal to ligand CT interactions. Reactions of RuCl3 with HPBI gave three distinct products; [Ru(HPBI)2Cl2]Cl (V), [Ru(HPBI)(dipy)Cl2]C1 (VI) and [Ru(PBI)2(py)2]Cl (VII). The UV-vis studies indicated the presence of intramolecular ligand to metal CT interactions. Electrochemical investigation of the complexes showed some irreversible, reversible and quasi-reversible redox reactions due to tautomeric interconversions through electron transfer. 相似文献
994.
Mishra A Wernsdorfer W Abboud KA Christou G 《Journal of the American Chemical Society》2004,126(48):15648-15649
The preparation of a new family of mixed transition metal/lanthanide clusters is reported. The reaction of [Mn3O(O2CPh)6(py)2(H2O)] with Ln(NO3)3 (Ln = Nd, Gd, Dy, Ho, and Eu) in a 1:2 molar ratio in MeOH/MeCN (1:20 v/v) leads to dark crystals in 55-60% isolated yield of complexes all containing the [Mn11Ln4]45+ core. The Dy compound has been found to give out-of-phase AC susceptibility signals, suggesting it might be a single-molecule magnet (SMM). This was confirmed by the observation of magnetization hysteresis loops. An Arrhenius plot constructed from magnetization decay data gave a barrier to relaxation of 9.3 K and showed the temperature-independent relaxation at very low temperatures indicative of quantum tunneling of magnetization. This is the initial demonstration of hysteresis and quantum behavior in a mixed 3d/4f SMM. 相似文献
995.
A method for simultaneous determination of uranium and thorium based on the deviation of their fission cross-section curves has been developed. Using a D-T neutron generator two different neutron spectra were produced with and without moderator around the target. The detection limits were found to be 0.044 mg and 0.25 mg in the presence of a moderator, while for fast neutrons 0.017 mg and 0.037 mg for uranium and thorium, respectively.This work was supported in part by the Ministry of Higher Education and the Hungarian Academy of Sciences. 相似文献
996.
Khalil A. Mahmoud Antony J. Rest Helmut G. Alt 《Journal of organometallic chemistry》1983,246(2):c37-c41
Infrared spectroscopic evidence including 13CO labelling and energy-factored force-field fitting is presented for the first time to show that the radicals (η5-C5H5)-M(CO)3? (M = MO, W) and HCO are produced on photolysis of (η5-C5H5)M(CO)3H complexes in CO matrices at 12 K. 相似文献
997.
Cameron TM Ortiz CG Ghiviriga I Abboud KA Boncella JM 《Journal of the American Chemical Society》2002,124(6):922-923
Reaction of [Mo(NPh)(PMe3)3(o-(Me3SiN)2C6H4)] (1) with molecular hydrogen (ca. 1 atm) at -10 degrees C in toluene-d8 results in the formation of dihydrogen complex [Mo(NPh)(PMe3)2(H2)(o-(Me3SiN)2C6H4)] (2) by 1H and 31P NMR spectroscopy. In solution at -50 degrees C 1 and 2 are present in a 1:3 ratio, respectively. The nature of dihydrogen ligand bonding in 2 was probed by T1 analysis and analysis of the JH-D coupling constant in the deuterium hydride isotopomer of 2 giving H-H distances of 1.18 A and 1.17 A, respectively. When allowed to warm to 30 degrees C, 2 reacts affording [Mo(NPh)(PMe3)3(o-(Me3SiN)(NH)C6H4)] (3) over a 1 h period. The X-ray structures of 1 and 3 are reported. 相似文献
998.
The rates of the acid hydrolysis of potassium ethyl malonate in presence of KCl, NaCl, Li2SO4 and MgSO4 in water and in 50% by weight of dioxane—water mixture were measured. The concentration of the added salts covered the range 0–1M. A negative salt effect on the rate of the half-ester hydrolysis was observed. The applicability ofBrønsted's equation was tested and deviations found were explained as due among other reasons, to the operation of an iondipole type of interaction. The correlation between the hydration numbers as well as the radii of the cations of the added electrolytes and the reaction rate were discussed. The activation energy was found to increase with an increase of the concentration of electrolyte due to the relative changes in solvation of the transition state as a result of hydration of the electrolytes added. The thermodynamic properties of the activated complex were calculated and discussed as functions of the salt concentration. A remarkable linear compensation between H
and S
was found.
Der kinetische Salz-Effekt bei der sauren Hydrolyse von Kaliumethylmalonat in Wasser und in 50% Dioxan—Wasser
Zusammenfassung Es wurde die Kinetik der Hydrolyse von Kaliumethylmalonat in Gegenwart von KCl, NaCl, Li2SO4 und MgSO4 (jeweils 0–1M) in Wasser und in 50% (w/w) Dioxan—Wasser untersucht. Es wurde ein negativer Salz-Effekt bezüglich der Hydrolysegeschwindigkeit des Halbesters beobachtet. Es werden sowohl Korrelationen zwischen Hydratationszahlen bzw. Ionenradien und der Reaktionsgeschwindigkeit, als auch zwischen Aktivierungsenergie und Elektrolytkonzentration diskutiert. Die thermodynamischen Parameter werden als Funktion der Salzkonzentration untersucht.相似文献
999.
G. Xomeritakis N.G. Liu Z. Chen Y.-B. Jiang R. Köhn P.E. Johnson C.-Y. Tsai P.B. Shah S. Khalil S. Singh C.J. Brinker 《Journal of membrane science》2007
We present a new processing scheme for the deposition of microporous, sol–gel derived silica membranes on inexpensive, commercially available anodic alumina (Anodisk™) supports. In a first step, a surfactant-templated mesoporous silica sublayer (pore size 2–6 nm) is deposited on the Anodisk support by dip-coating, in order to provide a smooth transition from the pore size of the support (20 or 100 nm) to that of the membrane (3–4 Å). Subsequently, the microporous gas separation membrane layer is deposited by spin-coating, resulting in a defect-free dual-layer micro-/mesoporous silica membrane exhibiting high permeance and high selectivity for size selective gas separations. For example, in the case of CO2:N2 separation, the CO2 permeance reached 3.0 MPU (1 MPU = 10−7 mol m−2 s−1 Pa−1) coupled with a CO2:N2 separation factor in excess of 80 at 25 °C. This processing scheme can be utilized for laboratory-scale development of other types of microporous or dense inorganic membranes, taking advantage of the availability, low cost and low permeation resistance of anodic alumina (or other metal oxide) meso- and macroporous supports. 相似文献
1000.
Khalil S 《The Analyst》1999,124(2):139-142
A coated wire trazodone-selective electrode based on incorporation of trazodone-tetraphenylborate ion pair in a poly(vinylchloride) coating membrane was constructed. The influences of membrane composition, temperature, pH of the test solution, and foreign ions on the electrode performance were investigated. The electrode showed a Nernstian response over a trazodone concentration range from 1.41 x 10(-5) to 0.89 x 10(-2) M, at 25 degrees C, and was found to be very selective, precise, and usable within the pH range 2.4-9.0. The standard electrode potentials, E degree, were determined at 20, 25, 30, 35, 40 and 45 degrees C and used to calculate the isothermal temperature coefficient (dE degree/dT) of the electrode. Temperatures higher than 45 degrees C seriously affected the electrode performance. The electrode was successfully used for potentiometric determination of trazodone hydrochloride both in pure solutions and in pharmaceutical preparations. 相似文献