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41.
T Yotsuyanagi N Ohta T Futo S Ito D N Chen K Ikeda 《Chemical & pharmaceutical bulletin》1991,39(11):3003-3006
Irreversible bindings of cis-diamminedichloroplatinum(II) (cis-DDP) to human serum albumin (HSA) were investigated in a pH 7.4 buffer containing 0.1 M NaCl at various molar ratios (cis-DDP/HSA) up to 60 over a 14 d period (37 degrees C). The metal binding seemed to reach a plateau when incubated at less than 10 times excess of cis-DDP. As the molar ratio increased, the reaction rate was relatively fast within the first day, followed by a moderate increase in the metal binding. When incubated at 60 times excess of cis-DDP, the metal bound as much as 20 mol per mol of HSA in 14 d. Fluorescence quenching of the metal-bound protein suggested that the tryptophan residue was gradually exposed to a hydrophilic environment as the metal binding increased. Furthermore, cis-DDP cleaved disulfide bonds at the ratio of 1 mol of disulfide bond per 5.3 mol of the metal binding. It was therefore suggested that the metal binding also occurred at several sites other than the disulfide bond. Warfarin binding to the metal-bound protein, examined by fluorescence changes, also decreased with increasing metal binding or cleavage of the disulfide bonds. Thus, cis-DDP bound to multiple sites in addition to the lone sulfhydryl group (Cys-34), suggesting that massive conformational changes of the protein took place. 相似文献
42.
Adding the cosmological term , which is assumed to be variable in this paper, to the Brans-Dicke Lagrangian, we try to understand the meaning of the term and to relate it to the mass of the universe. We also touch upon the Dirac large-number hypothesis, applying the results obtained from the application of our theory to a uniform cosmological model. 相似文献
43.
Summary A pure silica gel (Pia Seed 5S-60-SIL), synthesized by the hydrolysis of pure tetraethoxysilane [Si(OCH2CH3)4], was applied as a cation-exchange stationary phase in ion chromatography with indirect photometric detection for common
mono-and divalent cations (Li+, Na+, NH4
+, K+, Mg2+, and Ca2+) using various protonated aromatic monoamines (tyramine [4-(2-aminethyl) phenol], benzylamine, phenylethylamine, 2-methylpyridine
and 2,6-dimethylpyridine) as eluet ions. When using 0.75 mM tyramine-0.25 mM oxalic acid-1.5 mM 18-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane)
at pH 5.0 as the eluent, excellent simultaneous separation and highly sensitive detection at 275 nm for these mono-and divalent
cations were achieved on the Pia Seed 5S-60-SIL column (150×4.6 mm I.D.) in 20 min. 相似文献
44.
45.
Umebayashi Y Fujimori T Sukizaki T Asada M Fujii K Kanzaki R Ishiguro S 《The journal of physical chemistry. A》2005,109(40):8976-8982
Raman spectra of liquid 1-ethyl-3-methylimidazolium (EMI+) salts, EMI(+)BF4-, EMI(+)PF6-, EMI(+)CF3SO3-, and EMI(+)N(CF3SO2)2-, were measured over the frequency range 200-1600 cm(-1). In the range 200-500 cm(-1), we found five bands originating from the EMI+ ion at 241, 297, 387, 430, and 448 cm(-1). However, the 448 cm(-1) band could hardly be reproduced by theoretical calculations in terms of a given EMI+ conformer, implying that the band originates from another conformer. This is expected because the EMI+ involves an ethyl group bound to the N atom of the imidazolium ring, and the ethyl group can rotate along the C-N bond to yield conformers. The torsion energy for the rotation was then theoretically calculated. Two local minima with an energy difference of ca. 2 kJ mol(-1) were found, suggesting that two conformers are present in equilibrium. Full geometry optimizations followed by normal frequency analyses indicate that the two conformers are those with planar and nonplanar ethyl groups against the imidazolium ring plane, and the nonplanar conformer is favorable. It elucidates that bands at 241, 297, 387, and 430 cm(-1) mainly originate from the nonplanar conformer, whereas the 448 cm(-1) band does originate from the planar conformer. Indeed, the enthalpy for conformational change from nonplanar to planar EMI+ experimentally obtained by analyzing band intensities of the conformers at varying temperatures is practically the same as that evaluated by theoretical calculations. We thus conclude that the EMI+ ion exists as either a nonplanar or planar conformer in equilibrium in its liquid salts. 相似文献
46.
Extraction equilibria for the 4-(2-Pyridylazo)-Resorcinol-Nickel(II)-Quaternary-Ammonium salt system
The extraction equilibria of nickel(II)-PAR complexes with tetradecyldimethylbenzylammonium chloride(Q+Cl?) are investigated. Two kinds of nickel complex are extracted by chloroform: Ni(HR)2,nQ+Cl?(0)(?500 = 3.73·104l mol?1cm?1) at about pH 5 and 2Q+ NiR2-2(o)(?500 = 8.08·104 l mol?1 cm?1) at above pH 8.5. The extraction constant for 2Q+ NiR2-2(o) was evaluated as [2Q+ NiR2-2]0/[NiR2-2] [Q+]2 = 1011.16 at μ = 0.1 (Na2SO4. Synergic extraction studies of the Ni(HR)2 species under slightly acidic conditions show that the species is Ni(HR)2(H2O)2in auqeous solution and is extracted into chloroform as the adduct Ni(HR)2(TBP)2 (?535 = 3.57·104 l mol?1 cm?1. Based on the extraction behavior of these complexes, the structures of the Ni2+—PAR complexes are discussed. 相似文献
47.
The association constants, kd, of dichloroacetic acid (DCA) with ethers (tetrahydrofuran, tetrahydropyran, dibutyl ether, 1,4-dioxane) were measured in CCl4 from 20°–40° using near IR spectra. A linear relationship between log10KD and log10Kp was found, where Kp was the association constant of phenol with ethers. On the basis of their relationship the association constants of DCA with propylene oxide (PO) were estimated from those of phenol with PO. Furthermore, the ring-openings of PO with chloroacetic acids (trichloroacetic acid (TCA) or DCA) were studied kinetically in toluene. It was found that the PO-TCA reactions obeyed the second-order kinetics dependent on the first order both in the PO concn and in the TCA concn, and that the PO-DCA reactions obeyed the third-order kinetics on the first order in the PO concn and on the second order in the DCA concn. The elementary reaction rate constants were estimated on the basis of measured rate constants and estimated equilibrium constants and activation enthalpies were obtained from their temp dependence to be 13.5 in the PO-TCA reaction and 19.7 in the PO-DCA reaction. The mechanism was based on the activation enthalpy of elementary reaction and it was concluded that the main factor governing the reaction was the extent of activation of the protonated oxirane (the extent of polarization of the C-O bond in the oxirane ring). 相似文献
48.
Hirota J Satomi Y Yoshikawa K Takao T 《Rapid communications in mass spectrometry : RCM》2003,17(5):371-376
Epsilon -N,N,N-trimethyllysine (K(me3)) is a component of a number of proteins and plays an important role in the expression of their biological functions. Trimethylation, which causes an incremental increase in mass of 42.0470 Da from that of the corresponding MH(+) ion, cannot be distinguished from the acetylation (+42.0106 Da), which also occurs on epsilon-amino groups of Lys or alpha-amino groups in many proteins, without high-accuracy mass measurement which is accurate to within the second decimal place. MALDI-MS and MS/MS have been applied for the analyses of post-translational modifications of histone H3, which is known to contain both multiple acetylation and methylation sites in its sequence. During the measurements of the modified peptides, a novel fragmentation which involves the loss of trimethylamine from K(me3) was found. This characteristic fragmentation, which was observed to produce ions separated by 59 Da from the conventional precursor ion or sequence ions, would be useful for probing K(me3) units in the sequence. 相似文献
49.
The ion-pair extraction equilibria of the iron(II) and iron(III) chelates of 4-(2-pyridylazo)resorcinol (PAR, H(2)L) are described. The anionic chelates were extracted into chloroform with benzyldimethyltetradecylammonium chloride (QC1) as counter-ion. The extraction constants were estimated to be K(ex1)(Fe(II)) = [Q{Fe(II)(HL)L}](0)/[Q(+)][{Fe(II)(HL)L}(-)] = 10(8.59 +/- 0.11), K(ex2)(Fe(II)) = [Q(2){Fe(II)L(2)}](o)/ [Q(+)](2)[{Fe(II)L(2)}(2-)] = 10(12.17 +/- 0.10) and K(ex1)(Fe(III)) = [Q{Fe((III))L(2)}](o)/(Q(+)][{Fe(III)L(2)}(-)] = 10(6.78 +/- 0.15) at I = 0.10 and 20 degrees , where [ ](o) is concentration in the chloroform phase. Aggregation of Q{Fe(III)L(2)} in chloroform was observed and the dimerization constant (K(d) = [Q(2){Fe(III)L(2)}(2)](o)/[Q{Fe(III)L(2)}](o)(2)) was evaluated as log K(d) = 4.3 +/- 0.3 at 20 degrees . The neutral chelates of {Fe(II)(HL)(2)} and {Fe(III)(HL)L}, and the ion-pair of the cationic chelate, {Fe(III)(HL)(2)}ClO(4), were also extracted into chloroform or nitrobenzene. The relationship between the forms and extraction properties of the iron(II) and iron(III) PAR chelates are discussed in connection with those of the nickel(II) and cobalt(III) complexes. Correlation between the extraction equilibrium data and the elution behaviour of some PAR chelates in ion-pair reversed-phase partition chromatography is also discussed. 相似文献
50.
A method is described for determination of the steroidal saponin, eruboside B, originating in garlic and garlic products as the p-nitrobenzoyl chloride (PNBC) derivative by reversed-phase liquid chromatography (with ultraviolet detection at 260 nm. Proto-eruboside B was extracted from garlic (Allium sativum L.); subjected to solid-phase extraction (SPE) with a C18 cartridge, Florisil column chromatography, and silica gel column chromatography; and then enzymatically converted to eruboside B, which was applied as an external standard. Steroidal saponins in garlic and commercial garlic products were extracted with methanol and purified by SPE cartridges, followed by enzymatic treatment. A frostanol saponin such as proto-eruboside B is enzymatically transformed to a spirostanol saponin, eruboside B. After the derivatization with PNBC, the saponin derivative was chromatographed on a C8 column with a gradient elution of (A) 80% aqueous acetonitrile and (B) 100% acetonitrile. The detection limit of the developed method was 1 microg/g for the samples. The method was applied to the analysis of garlic and garlic health food products available in Japan. 相似文献