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991.
992.
993.
Valentin Besse Alexandre Fortin Georges Boudebs Paula S. Valle Marcelo Nalin Cid B. de Araújo 《Applied physics. B, Lasers and optics》2014,117(3):891-895
The third-order optical properties of GeO2–Bi2O3–PbO–TiO2 glasses at 532 nm and 1,064 nm were studied to evaluate their potential for optical limiting and all-optical switching. The Z-scan technique was used to determine the nonlinear (NL) refractive index, n 2, and the NL absorption coefficient, α 2, of samples with different amounts of the constituent oxides. Values of n 2 ≈ + 0.7 × 10?14 cm2/W at 1,064 nm and ≈+1.5 × 10?14 cm2/W at 532 nm were measured. The NL absorption coefficient, α 2, was smaller than the minimum that our apparatus can measure (α 2 < 0.01 cm/GW) in the near-infrared (1,064 nm); in the visible region (532 nm), we obtained α 2 ≈ 4.4 cm/GW. The set of NL parameters measured indicates the potential usefulness of the GeO2–Bi2O3–PbO–TiO2 glasses for all-optical switching at 1,064 nm and for optical limiting at 532 nm. 相似文献
994.
995.
Das S Sherwin BD Aguirre P Appel JW Bond JR Carvalho CS Devlin MJ Dunkley J Dünner R Essinger-Hileman T Fowler JW Hajian A Halpern M Hasselfield M Hincks AD Hlozek R Huffenberger KM Hughes JP Irwin KD Klein J Kosowsky A Lupton RH Marriage TA Marsden D Menanteau F Moodley K Niemack MD Nolta MR Page LA Parker L Reese ED Schmitt BL Sehgal N Sievers J Spergel DN Staggs ST Swetz DS Switzer ER Thornton R Visnjic K Wollack E 《Physical review letters》2011,107(2):021301
We report the first detection of the gravitational lensing of the cosmic microwave background through a measurement of the four-point correlation function in the temperature maps made by the Atacama Cosmology Telescope. We verify our detection by calculating the levels of potential contaminants and performing a number of null tests. The resulting convergence power spectrum at 2° angular scales measures the amplitude of matter density fluctuations on comoving length scales of around 100 Mpc at redshifts around 0.5 to 3. The measured amplitude of the signal agrees with Lambda cold dark matter cosmology predictions. Since the amplitude of the convergence power spectrum scales as the square of the amplitude of the density fluctuations, the 4σ detection of the lensing signal measures the amplitude of density fluctuations to 12%. 相似文献
996.
Andreia LeiteAna M.G. Silva Ana NunesMariana Andrade Carla SousaLuís Cunha-Silva Paula GameiroBaltazar de Castro Maria Rangel 《Tetrahedron》2011,67(22):4009-4016
The synthesis and characterization of three novel tetradentate ligands (T1, T2 and T3) based on 3-hydroxy-4-pyridinone chelating units are described. The three ligands exhibit different flexibility due to the use of two different anchor molecules, piperazine and 1,2-diaminobenzene, and to the diverse length of the 3-hydroxy-4-pyridinone arms. All reactions were performed using both conventional heating and microwave irradiation in order to evaluate the possibility of using greener methods in these synthetic procedures. The results showed that, in all cases, microwave irradiation provides the desired ligands reducing reaction time in ca. 97%. The structure of ligand T3 was resolved by X-ray crystallography, showing significant hydrogen bonding and interesting π-π interaction between the benzene and pyridinone rings. The use of potentiometric and spectroscopic methods allowed determination of acidity constants and unequivocal assignment of proton loss for each pKa value. Interaction of the ligands with divalent metal ions was assessed by spectroscopic methods. 相似文献
997.
The synthesis and characterization of the first scandium arene inverted-sandwich complexes supported by a ferrocene diamide ligand (NN(fc)) are reported. Through the use of (NN(fc))ScI(THF)(2) as a precursor and potassium graphite (KC(8)) as a reducing agent, the naphthalene and anthracene complexes [(NN(fc))Sc](2)(μ-C(10)H(8)) and [(NN(fc))Sc](2)(μ-C(14)H(10)), respectively, were synthesized and isolated in moderate to high yields. Both molecular structures feature an inverted-sandwich geometry and exhibit short Fe-Sc distances. DFT calculations were employed to gain understanding of the electronic structures of these new scandium arene complexes. A variable-temperature NMR spectroscopic study of [(NN(fc))Sc](2)(μ-C(14)H(10)) indicated that two different structures are accessible in solution. Reactivity studies showed that the naphthalene complex [(NN(fc))Sc](2)(μ-C(10)H(8)) can be converted to the corresponding anthracene species [(NN(fc))Sc](2)(μ-C(14)H(10)) and that [(NN(fc))Sc](2)(μ-C(10)H(8)) can act as either a reductant or a proton acceptor. The reaction of [(NN(fc))Sc](2)(μ-C(10)H(8)) with excess pyridine led to a rare example of C-C bond formation between two pyridine rings at the para position. 相似文献
998.
999.
A single-laboratory validation study was conducted on an HPLC method for the detection and quantification of cyanidin-3-O-galactoside (C3Ga), cyanidin-3-O-glucoside (C3GI), cyanidin-3-O-arabinoside (C3Ar), peonidin-3-O-galactoside (P3Ga), and peonidin-3-O-arabinoside (P3Ar) in cranberry fruit (Vaccinium macrocarpon Aiton) raw material and finished products. An extraction procedure using a combination of sonication and shaking with acidified methanol was optimized for all five anthocyanins in freeze-dried cranberry fruit and finished products (commercial extract powder, juice, and juice cocktail). Final extract solutions were analyzed by HPLC using a C18 RP column. Calibration curves for all anthocyanin concentrations had correlation coefficients (r2) of > or = 99.8%. The method detection limits for C3Ga, C3Gl, C3Ar, P3Ga, and P3Ar were estimated to be 0.018, 0.016, 0.006, 0.013, and 0.011 microg/mL, respectively. Separation was achieved with a chromatographic run time of 35 min using a binary mobile phase with gradient elution. Quantitative determination performed in triplicate on four test materials on each of 3 days (n = 12) resulted in RSD(r) from 1.77 to 3.31%. Analytical range, as defined by the calibration curves, was 0.57-36.53 microg/mL for C3Ga, 0.15-9.83 microg/mL for C3GI, 0.28-17.67 microg/mL for C3Ar, 1.01-64.71 microg/mL for P3Ga, and 0.42-27.14 microg/mL for P3Ar. For solid materials prepared by the described method, this translates to 0.06-3.65 mglg for C3Ga, 0.02-0.98 mg/g for C3Gl, 0.03-1.77 mg/g for C3Ar, 0.10-6.47 mg/g for P3Ga, and 0.04-2.71 mg/g for P3Ar. 相似文献
1000.
A method previously validated to determine caftaric acid, chlorogenic acid, cynarin, echinacoside, and cichoric acid in echinacea raw materials has been successfully applied to dry extract and liquid tincture products in response to North American consumer needs. Single-laboratory validation was used to assess the repeatability, accuracy, selectivity, LOD, LOQ, analyte stability (ruggedness), and linearity of the method, with emphasis on finished products. Repeatability precision for each phenolic compound was between 1.04 and 5.65% RSD, with HorRat values between 0.30 and 1.39 for raw and dry extract finished products. HorRat values for tinctures were between 0.09 and 1.10. Accuracy of the method was determined through spike recovery studies. Recovery of each compound from raw material negative control (ginseng) was between 90 and 114%, while recovery from the finished product negative control (maltodextrin and magnesium stearate) was between 97 and 103%. A study was conducted to determine if cichoric acid, a major phenolic component of Echinacea purpurea (L.) Moench and E. angustifolia DC, degrades during sample preparation (extraction) and HPLC analysis. No significant degradation was observed over an extended testing period using the validated method. 相似文献