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991.
A. K. Shukla S. Saini P. Kumar J. S. P. Rai A. K. Srivastava 《Journal of polymer science. Part A, Polymer chemistry》1989,27(1):43-51
The polymerization of vinyl acetate initiated by β-picolinium-p-chlorophenacylide was carried out at 30, 35, and 40°C, using the 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 L mol?1 s?1. The results are explained in terms of radical mode of polymerization with degradative initiator transfer; the principal mode of termination, however, was biomolecular. 相似文献
992.
P. K. Srivastava 《Journal of Chemical Sciences》1989,101(2):177-180
Chaotic oscillations in redox potential have been observed in thiophenol-KIO3-H2SO4 system in batch reactors. These occur in a concentration and temperature range. Bifurcation from a stable regime to a chaotic
regime occurs in a straight way in the entire concentration and temperature range. Oscillations were also studied in continuously
stirred tank reactors. These oscillations are deterministic chaos. It is tentatively suggested that chaos in the system is
due to a time delay caused by a large number of intermediates. 相似文献
993.
Acetoacetanilide, benzoylacetanilide and their derivatives have been examined in ultraviolet region in a series of solvents covering a broad polarity range e. e. from chloroform (Z, 63.2) to methanol (Z .83.6). Transition energies and oscillator strengths have been calculated and transition energy (ET) has been plotted against Z-values, a new empirical measurement of solvent polarity. A linear relationship was observed between the transition energy and Z-values for π → π* and n → π* transitions. These transitions are identified as charge transfer (c-t) transitions and with the solvents having carbonyl oxygen and sulphur atom a c-t complex formation has been suggested. Strong electron-donating substituents on phenyl group of the nitrogen atom also showed a weak to moderate n → π* transitions. These substituents have no influence on the position of the λmax in the same solvent. Stabilization energy of the excited state of these ligands and hence the dipole moments of the excited states have been calculated in comparison with pyridinium iodide. Solvent sensitivities of these ligands have also been calculated. 相似文献
994.
Nagappa AN Kole PL Srinivas D Vivek D Ullas DP Srivastava RC 《Colloids and surfaces. B, Biointerfaces》2005,43(1):21-27
Role of surface activity in the mechanism of action of thioridazine (THR) has been studied. THR has been shown to generate liquid membrane it self and also in association with the relevant membrane lipids, sphingomyelin and cholesterol in series with a supporting membrane. Transport of relevant biogenic amines e.g. dopamine, nor-adrenaline, adrenaline, serotonin, gamma amino butyric acid (GABA) and glutamic acid and ions viz. sodium, potassium, and calcium has been studied in the presence of liquid membranes generated by THR and THE in association with sphingomyelin-cholesterol. The data on modifications in the permeability of relevant biogenic amines and ions indicate that the liquid membranes generated by THR may contribute to the mechanism of action of THR. 相似文献
995.
Anion recognition through novel C-thiophenecalix[4]resorcinarene: PVC based sensor for chromate ions
Novel ionophore, C-thiophenecalix[4]resorcinarene (I) has been synthesized and characterized by IR, NMR and C, H, N analysis. Poly(vinyl chloride) (PVC) based membranes of ionophore (I) using dibutylphthalate (DBP), dioctylphthalate (DOP), 1-chloronapthalene (CN), tris(2-ethylhexyl) phosphate (TEHP) and bis(2-ethylhexyl)sebacate (DOS) as plasticizing solvent mediators were prepared and used as Cr selective sensors. Of the various sensors prepared, the one with membrane composition 2:66:120 mg (I: PVC: DBP) exhibited the best performance. This sensor works well over a wide concentration range 5.6 × 10−6-1.0 × 10−1 M (detection limit ∼ 0.30 ppm) with Nernstian compliance (29.0 mV per decade) between pH 6.5-10.0 with a fast response time of ∼13 s. The selectivity coefficient values as determined by fixed interference method (FIM) indicate excellent selectivity for Cr ions over a large number of anions. The sensor exhibits adequate shelf-life ( ∼5 months) with good reproducibility (S.D. ± 0.2 mV). The sensor has been used in the potentiometric titration of chromate with Pb(II). Determination of chromium in electroplating waste using the sensor was successfully achieved. 相似文献
996.
Glycine cresol red (G. C. R) has been used as a complexometric indicator and a reagent for the spectrophotometric determination of inorganic ions1-4. It forms stable coloured chelates iusolution with some metal ions under appropriate conditions. This communication give the composition and stability of tungsten G. C. R. Chelate. 相似文献
997.
The composition and stability of the chelate formed between Zr(IV) and chromotrope 2R has been investigated using spectrophotometric methods. The chelate is violet in color and has λmax at 530 nm. The composition, determined by different methods is 1 : 1. The chelate is stable between pH 1.0-3.0. The value of log K as determined by two different methods are 4.48±0.2 and 4.21±0.1 and the values of free energy of formation are —6.21±0.2 and —5.83±0.1 respectively at 30°C. The system obeys Beer's Law over a concentration range of 2.50 to 20.0 ppm of zirconium. The effective range of photometric determination is 3.50 to 19.05 ppm of zirconium. 相似文献
998.
Summary Halogen oxidation of several LMo(CO)s andcis-L2Mo(CO)4 (L = Ph3P1Ph3As and Ph3Sb) derivatives has been studied. The LMo(CO)5 complexes react with halogens to give hexacoordinate LMo(CO)3 X2 (X = Cl, Br or I) derivatives which are of very rare occurrence. Similar reactions withcis-L2Mo(CO)4 give heptacoordinate L2Mo(CO)3X2 derivatives. The complexes have been characterised by elemental analysis, i.r. and conductivity measurements. 相似文献
999.
Srivastava A Ghorai S Bhattacharjya A Bhattacharya S 《The Journal of organic chemistry》2005,70(17):6574-6582
A novel low-molecular mass tetrameric sugar derivative containing azobenzene core, 1, showed pronounced hydrogelation at micromolar concentration. Based on this observation, four related azobenzene based tetrameric sugar derivatives, 4-7, and three tetrameric sugar derivatives with a bis-terephthalamide core, 9-11, were also synthesized. However, none of these closely related analogues of the compound 1 showed effective gelation. The gel formed from 1 was characterized extensively using melting temperature analysis, UV-vis, FT-IR, circular dichroism spectroscopy, and scanning electron microscopy. The resultant gel exhibited impressive tolerance to the pH variation of the aqueous phase and gelated water in the pH range of 4-10. While UV-vis and CD spectroscopy indicated that pronounced aggregation of the azobenzene chromophores in 1 was responsible for gelation, FT-IR studies showed that hydrogen bonding is also a contributing factor in the gelation process. The melting of gel was found to depend on the pH of the aqueous medium in which gel was formed. The gel showed considerable photostability to UV irradiation, indicating tight intermolecular packing inside the gelated state that rendered azobenzene groups in the resultant aggregate refractory to photoisomerization. The electron micrographs of the aqueous gels of 1 showed the existence of spongy globular aggregates in such gelated materials. Addition of salts to the aqueous medium led to a delay in the gelation process and also caused remarkable morphological changes in the microstructure of the gel. 相似文献
1000.
T. N. Srivastava A. K. S. Chauhan Miss Manjula Agarwal 《Transition Metal Chemistry》1978,3(1):378-379
Summary Binuclear complexes of phenyltin(IV) chlorides with transition metal chelates of tetradentate Schiff bases derived from acetylacetone, benzoylacetone oro-hydroxyacetophenone and ethylenediamine or propylenediamine, of the general formula PhnSnCl4-nML (where n = 1 or 2, M = Ni11 or Cu11 and L2–= the Schiff base dianion), have been synthesised and characterized through elemental analysis, conductance and i.r. spectroscopic data. The coordination of metal chelates to tin involves two triply bonded oxygen atoms giving rise to an octahedral environment around SnIV. The molar conductance of the complexes in nitrobenzene shows the presence of the uncoordinated ML and phenyltin(IV) chloride moieties in solution.Author to whom all correspondence should be directed. 相似文献