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971.
Parimal Kundu Samiran Mitra Sonjay Kumar Dilip Banerjee Ranga Lal Bhattacharya 《Transition Metal Chemistry》1995,20(5):417-422
Summary Double complex salts containing cationic CuII having cyclic ligand piperazine (pipz), N-methylpiperazine (mpipz) and N,N-dimethylpiperazine (dmpipz) and hexacyanoferrate(III) ion have been synthesized and characterized by elemental analyses, i.r. and electronic spectra, and magnetic moment measurements. Mössbauer spectra at room temperature and at 80 K, were recorded in order to evaluate the metal-metal charge transfer and the impact of the cyclic ligand present in cationic moiety of the double complex salt upon the Mössbauer spectra of the hexacyanoferrate(III) ion. Evidence for metal-metal charge transfer is supported by electronic spectra and magnetic susceptibilities. Variable temperature e.p.r. spectra were recorded in order to determine the distortion of crystal system. Thermally induced stereochemical studies have been carried out with the help of i.r. spectral data. Kinetics of thermochemical reactions have also been studied. Activation energies (E
infa
sup*
) and inception temperatures for the thermochemical reactions show the order of stability of the double complex salts follows the trend: dmpipz > mpipz > pipz, which indicates that the + I effect is more pronounced than steric effect. 相似文献
972.
The kinetics of the anation reaction of cis-diaquo-bis-oxalatochromate(III) ion by DL-alanine has been studied spectrophotometrically
in the pH range 3.8 to 7.3, where DL-alanine remains in zwitterionic form. A second-order rate law has been established. Reaction
rates in three different ethanol-water mixtures were measured. In each solvent medium the anation rate is higher as compared
to water exchange reaction at a particular temperature. The activation parameters (gDH# and ΔS#) in different ethanol-water mixtures were obtained from Eyring plots. ΔG#(ΔH# −TΔS
#) values were calculated in each solvent medium and compared with that of the isotopic water exchange process. A reaction
mechanism involving theS
N2 path has been suggested. 相似文献
973.
Sk. F. Ahmed S. Khan P. K. Ghosh M. K. Mitra K. K. Chattopadhyay 《Journal of Sol-Gel Science and Technology》2006,39(3):241-247
Al doped SnO2 thin films have been synthesized by a sol-gel dip coating technique with different percentages of Al on glass and silicon
substrates. X-ray diffraction studies confirmed the proper phase formation in the films and atomic percentage of aluminium
doping in the films was obtained by energy dispersive X-ray studies. SEM studies showed the particle sizes lying in the range
100–150 nm for the undoped films and it decreased with increase of Al doping. Optical transmittance spectra of the films showed
high transparency (∼80%) in the visible region and the transparency increases with the increase of Al doping in the films.
The direct allowed bandgap of the films have been measured for different Al concentration and they lie within the range of
3.87–4.21 eV. FTIR studies depicted the presence of Sn–O, Al–O, bonding within the films. The room temperature electrical
conductivities of the films are obtained in the range of 0.21 S cm−1 to 1.36 S cm−1 for variation of Al doping in the films 2.31–18.56%. Room temperature Seebeck coefficients, SRT of the films were found in the range +56.0 μVK−1 to −23.3 μVK−1 for variation of Al doping in the films 18.56–8.16%. It is observed that the Seebeck coefficient changes its sign at 12.05%
of Al in the films indicating that below 12.05% of Al doping, SnO2:Al behaves as an n-type material and above this percentage it is a p-type material. 相似文献
974.
Mohammad Yazdanbakhsh Mohammad Hakimi Majid M. Heravi Mitra Ghassemzadeh Bernhard Neumüller 《无机化学与普通化学杂志》2004,630(5):627-629
The reaction of 4‐amino‐1, 2, 4‐triazin‐3(2H)‐thione‐5‐one (ATTO, 1 ) with [Cu(PPh3)2]NO3 in ethanol led to the complex [Cu(PPh3)2(ATTO)]NO3 ( 2 ). 2 was characterized by elemental analyses, IR, 1H NMR and Raman spectroscopy. A single‐crystal X‐ray diffraction of compound 2 revealed that ATTO acts as a bidentate ligand via its nitrogen and sulfur atoms. Crystal data for 2 at 20 °C: space group P21/n with a = 975.7(1), b = 1533.5(2), c = 2504.2(3) pm, β = 92.25(1)°, Z = 4, R1 = 0.0632. 相似文献
975.
D:A-Friedoolean-25-ol (
) and 25-al (
) have been synthesised from D:A-friedoolean-7β -ol (
). Substituted tetrahydrofuran rings are opened up on treatment with lithium in ethylene-diamine to yield the corresponding saturated alcohols. 相似文献
976.
Sorption of51Cr(VI) by MnO2 has been studied as a function of pH and ionic concentration in the presence of certain added cations and anions. The findings are explained in the light of deprotonation/hydroxyl ion association reaction on oxide surface and its subsequent interaction with the tracer. Infrared spectroscopy has shown the chemical interaction of Cr(VI) on the surface of MnO2. The influence of certain interfering ions has been shown on the sorption of51Cr(VI) on MnO2 surface. An attempt has been made to concentrate traces of51Cr under optimum experimental conditions. The experimental observation shows that the activity sorbed under specified conditions can be recovered appreciably by leaching the pre-adsorbed carrier. 相似文献
977.
C. Robert Lucas Kamala Mitra Subhendu Biswas Shyamal Kumar Chattopadhyay Bibhutosh Adhikary 《Transition Metal Chemistry》2005,30(2):185-190
A series of mononuclear MnII and MnIV complexes of general formulae [MnL2(NCS)2] (1a–1d) and [Mn(L)2(NCS)2] (2a–2c) have been prepared where L are Schiff bases obtained by the condensation of pyridine-2-aldehyde with para-alkyl-substituted aniline, and L are the corresponding amide ligands. The room temperature magnetic susceptibility data of (1a–1d) indicate that MnII is in a high spin state. The cyclic voltammograms of (1a–1d) exhibit a one-electron quasi-reversible MnIIMnIII oxidation. A linear correlation has been found when E0[MnIII/MnII] is plotted against Hammett p parameters. X-ray crystallographic data of (1b) shows that the central MnII ion adopts a distorted octahedral geometry with six different Mn–N distances. Upon oxidation of MnII complexes (1b–1d) by H2O2, the corresponding MnIV complexes (2a–2c) were obtained, and the Schiff base ligands were oxidized to the corresponding amides. The lowest energy LMCT bands of these MnIV complexes correlate linearly with Hammett p parameters. The redox behavior of the MnIV complexes has been investigated by cyclic voltammetry. E.p.r. spectra of the MnII and MnIV complexes are also reported. 相似文献
978.
Summary Application of hexamethylphosphoramide (HMPA) in the iron(III)-thiocyanate system gives a simple, sensitive and highly selective method for the spectrophotometric determination of Fe(III) in the organic phase (CHCl3). The color is stable for more than 24 hours in CHCl3. The system obeys Beer's law for 7g Fe/ml and the optimum concentration range is found to be 0.5–5g/ml. The molar absorptivity of 1.33×104 l·mole–1·cm–1, and Sandell's sensitivity is 0.0044/cm2 at 460 nm The composition of Fe(III) to thiocyanate is found to be 13 in the presence of HMPA in CHCl3. The method is free from interferences of many anions and cations. The method has been used to determine iron in bauxite ore.
Flüssig-flüssig-Extraktion von Eisenrhodanid nach Zusatz von Hexatnethyl-pbosphoramid: Direkte spektrophotometrische Bestimmung in der organischen Phase
Zusammenfassung Der Zusatz von Hexamethylphosphoramid (HMPA) zu Eisen(III)-Thiocyanat führt zu einer einfachen, empfindlichen und sehr selektiven Methode der spektrophotometrischen Bestimmung von Fe(III) in organischer Phase (CHCl3). Die Farbe bleibt in Chloroform mehr als 24 Stunden beständig. Das System entspricht dem Beerschen Gesetz unterhalb 7g Fe/ml. Das Konzentrationsoptimum liegt zwischen 0,5 und 5g/ml. Die molare Extinktion beträgt 1,33·104 l·Mol–1·cm–1, die Empfindlichkeit nach Sandell 0,0044g/cm2 bei 460 nm. Das Verhältnis Fe(III): Rhodanid in CHCl3 ist 13 in Gegenwart von HMPA. Die Methode wird von vielen Anionen und Kationen nicht gestört. Sie wurde zur Bestimmung von Eisen in Bauxit verwendet.相似文献
979.
Pinaki Mitra Subhas C. Nandy 《Journal of Algorithms in Cognition, Informatics and Logic》1998,28(2):315-338
In this paper we present an algorithm to compute the rectilinear geodesic voronoi neighbor of an arbitrary query pointqamong a setSofmpoints in the presence of a set ofnvertical line segment obstacles inside a rectangular floor. The distance between a pair of points α and β is the shortest rectilinear distance avoiding the obstacles in and is denoted by δ(α, β). The rectilinear geodesic voronoi neighbor of an arbitrary query pointq,RGVN(q) is the pointpi ∈ Ssuch that δ(q, pi) is minimum. The algorithm suggests a preprocessing of the elements of the setsSand inO((m + n)log(m + n)) time such that for an arbitrary query pointq, theRGVNquery can be answered inO(log(m + n)) time. The space required for storing the preprocessed information isO(n + m log m). If the points inSare placed on the boundary of the rectangular floor, a different technique is adopted to decrease the space complexity toO(m + n). This technique works even if the obstacles are rectangles instead of line segments. Finally, the parallelization of the preprocessing steps for the latter algorithm is suggested, which takesO(log3(m + n)) time, usingO((m + n)1.5/log2(m + n)) processors andO(log(m + n)) query time. 相似文献
980.