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171.
B. L. Rao P. P. Parekh M. Sankar Das 《Journal of Radioanalytical and Nuclear Chemistry》1969,2(1-2):79-89
A radiochemical method has been devised for the separation of bismuth activities of the natural series,viz.214Bi,210Bi and212Bi, and applied to the indirect estimation of their corresponding precursors,222Rn,210Pb and212Pb, in a wide variety of geological materials. The method consists of the solvent extraction of bismuth in radiochemically
pure form from the sample solution atpH 2 with diallyldithiocarbamido-hydrazine (Dalzin) in chloroform, and back extraction with 2M acid. The advantages of this method over the dithizone extraction system are discussed. 相似文献
172.
An optimized semi-automatic protocol for parallel synthesis of up to 96 peptide nucleic acids (PNA) or PNA-peptide conjugates using Boc-protection strategy has been developed using a robotic system. The approach is illustrated by synthesizing PNA and PNA-peptide libraries varying between 15 and 27 amino acid units. The peptides (NLS (nuclear localization signal) or Tat-peptide) were attached to N-terminus of the PNA. The method was found to be far superior to that based on the SPOT/Fmoc protocol by which PNA oligomers are synthesized on a modified cellulose membrane. On a 0.5 micromole scale the method typically yielded 2 mg product of 90% purity by HPLC/MALDI-TOF analysis. This approach is suitable for screening of a large number of PNA and/or peptide sequences for biochemical and biological studies. 相似文献
173.
Thorium was precipitated from homogeneous solution by photochemical reduction of periodate to iodate in a solution containing thorium and perchloric acid, by means of a 2537 A low-pressure mercury vapour lamp. For weighing, the precipitate was redissolved, precipitated once as thorium hydroxide, and finally as thorium oxalate, which was ignited to thorium dioxide. Quantitative results were obtained in the range 35-180 mg of thorium. 相似文献
174.
Summary Results of spectrophotometric, conductometric and dialysis studies on the interaction of acridine orange monohydrochloride dye with sodiumdodecylsulfate (anionic), cetyltrimethylammoniumbromide (cationic) and Triton X 100 (nonionic) surfactants have been reported. The anionic surfactant, SDS has been observed to undergo both electrostatic and hydrophobic interactions with the dye cation. Aggregation of the dye molecules can be destroyed when the surfactant is in large excess, whereas, excess dye can check micellization of SD S. At a ratio of AO:SDS=1:7 and above, dye embedded mixed micelles are formed. These remain in a separate phase, probably as coacervates. At lower ratios than 1:7, aggregation of dye molecules is induced, which being complexed with SDS become stabilized as colloids. The colloid and the coacervate have been observed to be thermally stable, negatively charged materials that can be broken by salts, and cations of higher valency are more effective in this regard. An 1:3 = AO:SDS colloid has beeen found to be sufficiently large like the coacervates to pass through a membrane having cut off permeability for molecular weights 12,000 and above. All the above features of AO-SDS interaction have been observed to be absent for AO-CTAB and AO-TX 100 systems, Even hydrophobic interaction has played an insignificant role in these cases. Thus, the dye cation, the cationic and the nonionic surfactants have almost retained their self physicochemical identities in solution in the presence of each other. Electrostatic interaction is thus the primary requirement for acridine orange-surfactant (anionic) system; the hydrophobic effect is secondary and may become co-operative.With 9 figures and 2 tables 相似文献
175.
Keda Zhang G. Sudesh Kumar D. C. Neckers 《Journal of polymer science. Part A, Polymer chemistry》1985,23(5):1293-1305
We report herein studies of Co(OAc)2 and related transition metal compounds which serve as catalysts for aldol condensations when complexed with bipyridine, triphenyl phosphine, and crown ether. A comparison has been made with polymeric complexes of cobalt(II), which serve the same purpose. Cobalt complexes of built-in polyureas based on bipyridine and crown ether as well as those immobilized to polystyrene by triphenylphosphine and poly(4-vinyl pyridine) are also reported. 相似文献
176.
Sukumar Aditya Syamal Bandopadhyay Rebati C. Das Bata K. Nanda 《Thermochimica Acta》1981,46(3):337-340
From rehydration experiments the hydrates Ba(OH)2 · 8 H2O, Ba(OH)2 · 3 H2O β-Ba(OH)2, · 1 H2O, and γ-Ba(OH)2 · 1 H2O have been found in the system Ba(OH)2-H2O. Thermoanalytical measurements (DTA, TG, DTG, high temperature X-ray diffraction, high temperature Raman scattering) on these hydrates are reported. Thermal decomposition of Ba(OH)2 · 8 H2O and Ba(OH)2 · 3 H2O always results in the formation of β-Ba(OH)2 · 1 H2O, the stable form of the monohydrates at ambient temperature. Dehydration of β- and γ-Ba(OH)2 · 1 H2O, both of which form anhydrous β-Ba(OH)2 as the first product of decomposition, starts at 105 and 115°C, respectively. Single crystals of Ba(OH)2 · 3 H2O and γ-Ba(OH)2 · 1 H2O were prepared from Ba(OH)2 · 8 H2O meltings and from ethanolic solutions of Ba(OH)2 , respectively. The crystal data are: Ba(OH)2 · 3 H2O (orthorhombic, Pnma): a = 764.0(2), b = 1140,3(5), c = 596.5(1) pm, Z = 4; γ-Ba(OH)2 · 1 H2O (monoclinic, P21/m or P21): a = 704.9(2), b = 418.4(1), c = 633.3(1) pm, β = 111.45(2)°, Z = 2. 相似文献
177.
A simple method for the determination of molybdenum and tungsten in sea and surface water is presented. Molybdenum and tungsten are concentrated on activated charcoal by adsorption as the ammonium pyrrolidine dithiocarbamate complex; the optimal pH for adsorption is 1.3. Mo and W are then determined by thermal neutron activation, forming 99Mo (T = 66.7 h) and 137W (T = 23.8 h), respectively. The 99mTc daughter of 99Mo is measured as soon as the equilibrium between 99mTc(T= 6 h) and 99Mo is established. The detection limits are 0.05 μg Mo l-1 and 0.05 μg W l-1 (or 0.001 μg W l-1 after a simple chemical separation). 相似文献
178.
A. K. Shukla S. Saini P. Kumar J. S. P. Rai A. K. Srivastava 《Journal of polymer science. Part A, Polymer chemistry》1989,27(3):807-815
Polymerization of vinyl acetate initiated by β-picolinium p-chlorophenacylide was carried out at 30, 35, and 40°C, using conventional dilatometric technique. The initiator and the monomer exponent values were 0.80 ± 0.15 and unity, respectively. The polymerization was inhibited in the presence of hydroquinone, but was favored by nonpolar solvent and polymerization temperature. The energy of activation was 90.3 KJ mol?1. An average value of k/kt for the present system was found to be 0.37 × 10?2. The results are explained in terms of a radical mode of polymerization with degradative initiator transfer; the principal mode of termination, however, was bimolecular. 相似文献
179.
Devendra Kumar Uday Razdan Alka D. Gupta 《Journal of polymer science. Part A, Polymer chemistry》1992,30(7):1477-1487
Various melt-polymerizable bisimido-bisphthalonitrile polymer precursors were synthesized by the reaction of 4-aminophthalonitrile (4-APN) with bis(3,4-dicarboxyphenyl) dimethylsilane dianhydride (SIDA), 4,4′-hexafluoroisopropylidene diphthalic anhydride (6FDA), bis(3,4-dicarboxyphenyl)ether dianhydride (ODPA), and 3,3′, 4,4′-tetracarboxylichenzophen+ne dianhydride (BTDA) in an aprotic solvent. The synthesized monomers showed crystalline melting at 269 and 271°C. Elemental analysis, differential thermal analysis (DTA), infrared (IR), nuclear magnetic resonance (1H-NMR) and mass spectral studies were carried out to characterize the synthesized monomers. Thermogravimetric analysis (TGA) of the synthesized monomers showed their thermal stability at 410–400°C. A detailed study and NMR investigation of the first step of condensation reaction was carried out and indicated the formation of a transient charge transfer complex. Thermal cyclization of the formed intermediate, however, gave the required monomers. A preliminary study demonstrated that melt-polymerization of the synthesized monomers gave thermallystable, tough polymers. 相似文献
180.
Mukul Biswas Sukhendu K. Das 《Journal of polymer science. Part A, Polymer chemistry》1981,19(12):3155-3164
A new polymeric azodye has been synthesized from carbazole by diazotization of its derivative N-methylcarbazole-3,6-diamine and subsequent coupling reaction with 2,2-bis(4-hydroxyphenyl-3-sulfonate-Na)-propane prepared from bisphenol-A. Its physico-chemical, electrical, and thermal properties have been characterized; finally, its application to the preparation of colored semiconductive films from polyvinyl alcohol has been studied. 相似文献