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171.
M. K. Das N. Ramamoorthy B. R. Sarkar R. S. Mani 《Journal of Radioanalytical and Nuclear Chemistry》1987,111(2):469-475
We have studied the feasibility of producing57Co (271.3 d) via the55Mn(, 2n)57Co reaction (55Mn–100%). The thick target yield of57Co in the 28 to 18 MeV energy region was measured as 3.87 Ci/Ah. However, the proximity and overlap of the excitation functions for (, n), (, 2n) and (, 3n) reactions on55Mn are such that the production of pure57Co in high yields free of58Co (70.8 d) and56Co (78.8 d) has not been feasible. We have also studied a new method for ancillary production of57Co via the reactions58Ni(, p)57Co and
during the course of producing62Zn by60Ni(, 2n)62Zn reaction. In this case the yield of57Co of reasonable purity has been up to 1 Ci/Ah. 相似文献
172.
Nigamananda Das 《Transition Metal Chemistry》1993,18(4):372-376
Summary The kinetics of reversible complexation of Ni(OH2)
inf6
sup2+
with oxygen-bonded glycinatocobalt(III) substrates N4-Co(glyH)gly2+ [N4 = (en)2 or trien; glyH = H3N+CH2-COO–] have been investigated by the stopped-flow technique in the 20–35° C range, at pH = 6.08–6.82 and I = 0.3 mol dm–3. The formation of N4Co(glyH)glyNi4+ occurred via the reaction of Ni(OH2)
inf6
sup2+
with the deprotonated form of the cobalt(III) substrates, N4Co-(glyH)gly2+. The rate and activation parameters for the formation and dissociation of the binuclear species are reported. The formation rate constants k
f (at 25° C), activation enthalpy and entropy H
, S
for N4Co-(glyH)glyNi4+ are 320±49, 341 ± 52dm3mol–1 s–1, 78 ± 7, 79 ± 5 kJmol–1 and 64 ± 24, 69 ± 18 JK–1 mol–1 for the ethylenediamine and triethylenetetraminecobalt(III) substrates, respectively. This result indicates that the rate and activation parameters are virtually independent of the nature of N4 moities, which strongly suggests that the formation of mono-bonded species occurs via entry of one of the pendant NH2 groups into the coordination sphere of nickel(II) via a rate-limiting Ni-OH2 bond dissociation mechanism (Id). The binuclear species exist in dynamic equilibrium between the monodentate and chelated forms, with the chelate form predominating. The low values of spontaneous dissociation rate constant for the binuclear species (k
r- 0.095–1 at 25° C) in comparison with the high values of dissociation rate constants of monodentate nickel(II) complexes reported in the literature also support the chelate nature of the binuclear species. 相似文献
173.
G. D. Wals H. A. Das H. A. Van Der Sloot 《Journal of Radioanalytical and Nuclear Chemistry》1980,57(1):215-222
A simple method is presented for the determination of inorganic arsenic in water samples. The lower limit of determination
is 0.01 μg·1−1. Penta-and trivalent arsenic ions as well as arsenic acid substituted with aromatic ligands are collected by coprecipitation
with Fe(OH)3. After irradiation the arsenic is separated from the iron by adsorption to Al2O3. The overall efficiency is (97∓1)%. The procedure takes one day per ∼20 samples. It has been checked by standard addition.
Data for sea- and surface-water are given. As the concentration of aromatic arsenic-compounds is very small in comparison
to that of the inorganic species, it does not affect the result of the determination. 相似文献
174.
Abstract— Triplet-and singlet-related photoprocesses of pyrene-1-aldehyde (PA) in various solvents have been investigated in detail using 337.1 and 355 nm laser flash photolysis in conjunction with time-correlated determination of fluorescence lifetimes (τF ) and steady-state photochemical and absorption-emission spectral measurements. In benzene, the lowest triplet of PA (43 < ET < 46 kcal/mol) has a lifetime of about 50 µs (τT ) and displays the absorption maximum at 443 nm with a maximum extinction coefficient (εmax ) of 21000 M -1 cm-1 ; the corresponding ketyl radical has a sharp absorption maximum at 428 nm (εmax ≥ 25000 M -1 cm-1 ). The quantum yields (φT ) of lowest triplet occupation are high in nonprotic solvents (0.6–0.8), decrease in protic solvents (alcohols) as the polarity of the latter is increased, and maintain a complementary relationship with the quantum yields (φF ) of fluorescence. Quantum yields (φPC ) of loss of PA due to photoreactions in some solvents have also been determined under conditions of steady irradiation at 366 nm; φPC is in the range 0.1–0.2 in electron-rich olefinic solvents such as cyclohexene and tetramethylethylene. These results concerning τF , τT , φF . φT and φPC as well as the effects of 1,2,4-trimethoxybenzene and 2,5-dimethyl-2,4-hexadiene as quenchers for fluorescence, triplet yield, and photochemistry are discussed in the light of possible state orders for PA in polar and nonpolar environments. 相似文献
175.
Biswanath Das Maddeboina Krishnaiah Keetha Laxminarayana K. Ravinder Reddy 《Journal of molecular catalysis. A, Chemical》2007,270(1-2):284-288
Sulfated zirconia has been employed as an efficient recyclable catalyst for the preparation of various β-acetamidoketones or esters at room temperature. The process involves the one-pot multicomponent reactions of aromatic aldehydes, enolizable ketones or β-ketoesters and acetonitrile in the presence of acetyl chloride. 相似文献
176.
N. R. Das P. S. Chakraborty S. N. Bhattacharyya 《Journal of Radioanalytical and Nuclear Chemistry》1977,36(2):419-425
Present investigation deals with neutron activation analysis of gold in some varieties of geological samples related to auriferous
quartz veins. A few plant specimens of the area were also analyzed. The gold contents in the rock samples as determined by
the destructive way of analysis vary in the range 10−5 to 10−7%. In case of plant samples, however, the non-destructive method of analysis of the plant ashes was followed and the concentration
of gold was found to be of the order of 10−5%. In plants, besides gold, some associated elements, such as La, Ce, Sm, Lu, Zr, Hf, Se, W, As and Sb were also identified. 相似文献
177.
Razaghi M. Gandomkar M. Ahmadi V. Das N. K. Connelly M. J. 《Optical and Quantum Electronics》2012,44(3-5):255-263
Optical and Quantum Electronics - In this paper, we analyse the picosecond wavelength conversion using semiconductor optical amplifier (SOA) with a novel technique. For an accurate and precise... 相似文献
178.
179.
180.
Parag Deshpande Zhang Jie Ramesh Subbarayan Vijay Kumar Mamidi Raja Haranadha Babu Chunduri Tapas Das Sathyavageeswaran Shreeram 《Biomedical chromatography : BMC》2013,27(2):142-147
A simple, sensitive and specific high‐performance liquid chromatography mass spectrometry (LC‐MS/MS) method was developed and validated for the quantification of β‐hydroxy‐β‐methyl butyrate (HMB) in small volumes of rat plasma using warfarin as an internal standard (IS). The API‐4000 LC‐MS/MS was operated under the multiple reaction‐monitoring mode using the electrospray ionization technique. A simple liquid–liquid extraction process was used to extract HMB and IS from rat plasma. The total run time was 3 min and the elution of HMB and IS occurred at 1.48 and 1.75 min respectively; this was achieved with a mobile phase consisting of 0.1% formic acid in a water–acetonitrile mixture (15:85, v/v) at a flow rate of 1.0 mL/min on a Agilent Eclipse XDB C8 (150 × 4.6, 5 µm) column. The developed method was validated in rat plasma with a lower limit of quantitation of 30.0 ng/mL for HMB. A linear response function was established for the range of concentrations 30–4600 ng/mL (r > 0.998) for HMB. The intra‐ and inter‐day precision values for HMB were acceptable as per Food and Drug Administration guidelines. HMB was stable in the battery of stability studies, viz. bench‐top, autosampler freeze–thaw cycles and long‐term stability for 30 days in plasma. The developed assay method was applied to a bioavailability study in rats. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献