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31.
We describe a simple electrochemical protocol for studying the ion-exchange binding of non-electroactive ions, specifically mono- and divalent metal cations of biological relevance (Mg(2+), Ca(2+), and K(+)), to DNA-modified surfaces. After incubation in a dilute solution of multiply charged transition metal complex (5.0 microM [Ru(NH(3))(6)]Cl(3)), gold electrodes modified with thiolate-DNA monolayers respond to the presence of these non-electroactive metal cations by producing significant changes in the cyclic voltammograms (i.e., decrease of the integrated charge and shift of formal potential) of the surface-bound redox complex ([Ru(NH(3))(6)](3+)). The divalent cations (particularly Mg(2+)) can be detected at very low concentrations (<10 microM), while the on-set value for K(+) is substantially higher (50 mM). The equilibrium binding constants for Mg(2+) and Ca(2+) to DNA-modified surfaces were calculated. 相似文献
32.
An efficient, cost-effective and environmentally benign synthesis of novel tetracyclic bis-isoxazolopyrroloquinoline derivatives has been developed via one-pot four-component reaction of 4-amino-3-methyl-5-styrylisoxazoles, dimedone, aryl glyoxal monohydrates and 5-amino-3-methylisoxazole by employing water as a reaction medium and acetic acid (AcOH) as a green promoter. The advantages of this protocol are environmentally friendly, metal-free, less reaction time, operational simplicity, high yields, broad substrate scope and easy purification. Most significant of all, this method is green. 相似文献
33.
Values of the incoherent scattering function SK for scattering of photons from K-shell electrons are computed for 2He, 3Li, 4Be and 5B at photon energies 6, 10, 14, and 18 keV by using screened hydrogenic wavefunctions. The screening has been taken into account by the Thomas-Fermi model of the neutral atom. Unlike the previous calculations we have used a distorted Coulomb wavefunction for the ejected electron. The effects of Coulomb distortion and of screening corrections are discussed. It is shown that the screening correction and the Coulomb distortion in the ejected electron wavefunction play significant roles in the study of incoherent X-ray scattering by bound electrons. 相似文献
34.
Subhasis Mallick Subala Mondal Arup Mandal Biplab K. Bera Parnajyoti Karmakar Alak K. Ghosh 《国际化学动力学杂志》2011,43(9):498-506
The kinetics of the interaction of three glycine‐containing dipeptides, namely, glycine‐L‐leucine (Gly‐Leu), glycine‐L‐isoleucine (Gly‐Ile), and glycine‐valine (Gly‐Val) with [Pt(en)(H2O)2](ClO4)2 has been studied spectrophotometrically as a function of [substrate complex], [dipeptides] and temperature at a particular pH(4.0), where the substrate complex exists predominantly as the diaqua species and the dipeptides as a zwitterion. The substitution reaction shows two consecutive steps; the first is the ligand‐assisted anation and the second is the chelation step. The activation parameters for both the steps were evaluated using Eyring's equation. The low ΔH1≠ and large negative value of ΔS1≠ as well as ΔH2≠ and ΔS2≠ indicate an associative mode of activation for both the aqua ligand substitution processes. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 498–506, 2011 相似文献
35.
It is shown that a large class of solutions of Yang's equations for self-dual SU(2) gauge fields can be obtained from the solutions of two-dimensional and four-dimensional Laplace equations. 相似文献
36.
Organocatalytic Asymmetric Mannich Cyclization of Hydroxylactams with Acetals: Total Syntheses of (−)‐Epilupinine, (−)‐Tashiromine,and (−)‐Trachelanthamidine 下载免费PDF全文
Dr. Dipankar Koley Yarkali Krishna Kyatham Srinivas Afsar Ali Khan Ruchir Kant 《Angewandte Chemie (International ed. in English)》2014,53(48):13196-13200
An asymmetric, organocatalytic, one‐pot Mannich cyclization between a hydroxylactam and acetal is described to provide fused, bicyclic alkaloids bearing a bridgehead N atom. Both aliphatic and aromatic substrates were used in this transformation to furnish chiral pyrrolizidinone, indolizidinone, and quinolizidinone derivatives in up to 89 % yield and 97 % ee. The total syntheses of (?)‐epilupinine, (?)‐tashiromine, and (?)‐trachelanthamidine also achieved to demonstrate the generality of the process. 相似文献
37.
Nadanathangam Vigneshwaran Gopalakrishnapillai Bijukumar Nivedita Karmakar Sneh Anand Anoop Misra 《Macromolecular Symposia》2003,193(1):119-128
Isoelectric focusing (IEF) of glycated hemoglobin (GHb) was carried out in ultra-thin polyacrylamide gels to separate the hemoglobin-advanced glycation endproducts (Hb-AGEs) from the hemoglobin-A1C (HbA1C) fraction. Precast polyacrylamide gels (Ampholine® PAGplate) were used in Pharmacia LKB Multiphor II for this purpose. The separated bands for Hb-AGE and HbA1C based on their isoelectric point (pI), were confirmed with the purifed fractions obtained from the cation exchange chromatographic technique. From the calibration curve, the pI values were found to be 6.748 and 6.495 for HbA1C and Hb-AGE, respectively. The lowering of pI values for glycated hemoglobin, when compared to unglycated hemoglobin (pI = 6.852), can be attributed to the glycation at the amino terminals of the peptide chains. Increased reduction in pI value for Hb-AGE can be attributed to the effect of glycation of amino groups at various sites on the peptide chains, apart from the terminal amino groups. Fluorescence analysis was carried out for the purified fraction of Hb-AGE which showed the formation of a new fluorophor adduct having the excitation and emission maxima at 308 nm and 345 nm, respectively. Time-dependent formation of Hb-AGE under in vitro conditions was monitored by fluorescence (308/345 nm) over a period of 120 days, which showed its formation only after 3 weeks of incubation. 相似文献
38.
Reenamoni Saikia Chaliha K. Annapurna Anal Tarafder V.S. Tiwari P.K. Gupta Basudeb Karmakar 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2010,75(1):243-250
Precursor glass of composition 25K2O–25Nb2O5–50SiO2 (mol%) doped with Er2O3 (0.5 wt% in excess) was isothermally crystallized at 800 °C for 0–100 h to obtain transparent KNbO3 nanostructured glass–ceramics. XRD, FESEM, TEM, FTIRRS, dielectric constant, refractive index, absorption and fluorescence measurements were carried out to analyze the morphology, dielectric, structure and optical properties of the glass–ceramics. The crystallite size of KNbO3 estimated from XRD and TEM is found to vary in the range 7–23 nm. A steep rise in the dielectric constant of glass–ceramics with heat-treatment time reveals the formation of ferroelectric nanocrystalline KNbO3 phase. The measured visible photoluminescence spectra have exhibited green emission transitions of 2H11/2, 4S3/2 → 4I15/2 upon excitation at 377 nm (4I15/2 → 4G11/2) absorption band of Er3+ ions. The near infrared (NIR) emission transition 4I13/2 → 4I15/2 is detected around 1550 nm on excitation at 980 nm (4I15/2 → 4I11/2) of absorption bands of Er3+ ions. It is observed that photoluminescent intensity at 526 nm (2H11/2 → 4I15/2), 550 nm (4S3/2 → 4I15/2) and 1550 nm (4I13/2 → 4I15/2) initially decrease and then gradually increase with increase in heat-treatment time. The measured lifetime (τf) of the 4I13/2 → 4I15/2 transition also possesses a similar trend. The measured absorption and fluorescence spectra reveal that the Er3+ ions gradually enter into the KNbO3 nanocrystals. 相似文献
39.
Tocher DA Drew MG Nag S Pal PK Datta D 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(8):2230-2237
HL and MeL are prepared by condensing benzil dihydrazone with 2-formylpyridine and 2-acetylpyridine, respectively, in 1:2 molar proportions. While in a reaction with [Ru(C(6)H(6))Cl(2)]2, HL yields the cation [Ru(C(6)H(6)){5,6-diphenyl-3-(pyridin-2-yl)-1,2,4-triazine}Cl]+, MeL gives the cation [Ru(C(6)H(6))(MeL)Cl]+. Both the cations are isolated as their hexafluorophosphate salts and characterised by X-ray crystallography. In the case of HL, double domino electrocyclic/elimination reactions are found to occur. The electrocyclic reaction occurs in a C=N-N=C-C=N fragment of HL and the elimination reaction involves breaking of a C-H bond of HL. Density functional calculations on model complexes indicate that the identified electrocyclic reaction is thermochemically as well as kinetically feasible for both HL and MeL in the gas phase. For a double domino reaction, similar to that operative in HL, to occur for MeL, breaking of a C-C bond would be required in the elimination step. Our model calculations show the energy barrier for this elimination step to be much higher (329.1 kJ mol(-1)) for MeL than that for HL (96.3 kJ mol(-1)). Thus, the domino reaction takes place for HL and not for MeL. This accounts for the observed stability of [Ru(C(6)H(6))(MeL)Cl]+ under the reaction conditions employed. 相似文献
40.
I. Banerjee Soumen Karmakar Naveen V. Kulkarni Ashok B. Nawale V. L. Mathe A. K. Das S. V. Bhoraskar 《Journal of nanoparticle research》2010,12(2):581-590
The synthesis of nanoparticles of titanium dioxide (TiO2) with varying percentages of anatase and rutile phases is reported. This was achieved by controlling the operating pressure
in a transferred-arc, direct current thermal plasma reactor in which titanium vapors are evaporated, and then exposed to ambient
oxygen. The average particle size remained around 15 nm in each case. The crystalline structure of the as-synthesized nanoparticles
of TiO2 was studied with X-ray diffraction analysis; whereas the particle morphology was investigated with the help of transmission
electron microscopy. The precursor species responsible for the growth of these nanoparticles was studied with the help of
optical emission spectroscopy. As inferred from the X-ray diffraction analysis, the relative abundance of anatase TiO2 was found to be dominant when synthesized at 760 Torr, and the same showed a decreasing trend with decreasing chamber pressure.
The study also reveals that anatase TiO2 is a more effective photocatalytic agent in degrading methylene blue by comparison to its rutile phase. 相似文献