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101.
102.
Kumio Yokoigawa Yoko Okubo Kenji Soda Haruo Misono 《Journal of Molecular Catalysis .B, Enzymatic》2003,23(2-6):389-395
A psychrophilic alanine racemase from Bacillus psychrosaccharolyticus has a higher catalytic activity than a thermophilic alanine racemase from Bacillus stearothermophilus even at 60 °C in the presence of pyridoxal 5′-phosphate (PLP), although the thermostability of the former enzyme is lower than that of the latter one [FEMS Microbial. Lett. 192 (2000) 169]. In order to improve the thermostability of the psychrophilic enzyme, two hydrophilic amino acid residues (Glu150 and Arg151) at a surface loop surrounding the active site of the enzyme were substituted with the corresponding residues (Val and Ala) in the B. stearothermophilus alanine racemase. The mutant enzyme (ER150,151VA) showed a higher thermostability, and a markedly lower Km value for PLP, than the wild type one. In addition, the catalytic activities at low temperatures and kinetic parameters of the two enzymes indicated that the mutant enzyme was more psychrophilic than the wild type one. Thus, the psychrophilic alanine racemase was improved in both psychrophilicity and thermostability by the site-directed mutagenesis. The mutant enzyme may be useful for the production of stereospecifically deuterated NADH and various
-amino acids. 相似文献
103.
Keisuke Kitamura Kazuyoshi Okubo Kazuo Shibasaki 《Bioscience, biotechnology, and biochemistry》2013,77(8):1983-1984
For the screening of potent proteases of plant origin, gelatinolytic activities were measured for various vegetables and fruits. Green asparagus, kiwi fruit and miut were found to possess high proteolytic activities. Optimum temperatures for the activities of green asparagus and miut were 40 to 45°C and that of kiwi fruit was 60°C. Optimum pHs for the three activities were in neutral or slightly alkaline regions. The proteolytic enzymes of kiwi fruit and miut were stimulated by cysteine and EDTA but that of green asparagus was unaffected by them. 相似文献
104.
Masato Aoyama Hiroshi Dohi Shigeru Shioya Yukari Takeuchi Yuji Mori Tadakatu Okubo 《Applied animal behaviour science》1994,40(3-4)
A feeding-deterrent substance was isolated from cattle feces and its effects on ingestive behavior were examined in goats. The substance was added to alfalfa hay and presented to the goats in the following experiments. In a two-choice test, between control fodder and the fodder treated with the substance, animals avoided eating treated fodder. This food-deterrent effect was strengthened in a dose-dependent manner. The results of ingestive behavior analysis suggested that this substance affected the goats through olfaction. However, in a single-presentation test, where the goats had no choice, no effect on ingestive behavior was noticed. It is therefore suggested that the preference induced by the substance is relative rather than absolute in the ingestive behavior of goats. 相似文献
105.
Masami Harada Akira Okubo Keiko Shibata Sunao Yamazaki Shozo Toda 《Bioscience, biotechnology, and biochemistry》2013,77(4):1081-1084
As a part of the study of bubble expansion in wheat flour dough under temperature rise, the critical radius for expansion, and the time course of expansion of an isolated bubble were investigated. As the required physical properties for the calculation of the critical bubble radius for expansion and the time course of bubble expansion, the authors measured the surface tension of the liquid phase of wheat flour batter as a function of concentration and temperature, and the apparent diffusion coefficients of air in wheat flour dough as a function of temperature. The critical radius for expansion and the time course of expansion of the isolated bubble under temperature rise were compared with the theoretical values calculated from the diffusion theory. At constant temperature, the time course of bubble shrinkage in wheat flour dough was described well by diffusion theory with the surface tension and the apparent diffusion coefficient, indicating that the bubble shrinkage would be rate-limited by the diffusion in the liquid phase of wheat flour dough of air out of the bubble. Under temperature rise from 3°C to 43°C, every bubble larger than the critical radius expanded. This result is physically admissible. On the other hand, the calculated time course of the bubble radius under temperature rise was not in agreement with the experimental data. 相似文献
106.
S Shimura T Okubo S Maeda T Aoki M Tomioka Y Shindo T Takishima K Umeya 《Biorheology》1983,20(5):677-683
We studied the effects of expectorants (mucolytic agents) in vivo on the relaxation behavior of sputum viscoelasticity. Seven female and thirty-three male patients (56.8 +/- 19.3 yrs, range: 21 to 82 years old) with a chronic pulmonary disease except bronchial asthma were studied. They were randomly put into the control group or a group which would be given oral treatments with an expectorant for a week after a one week washout period. The groups were as follows: Group I (n = 8), control; Group II (n = 7), Bromhexine hydrochloride 24 mg per day; Group III (n = 10), Ambroxol 90 mg per day; Group IV (n = 9) alpha - Chymotrypsin buccle 100 ch.u. per day; Group V (n = 6), Serratiopeptidase 30 mg per day. In Groups IV & V, frequency dependence of sputum viscoelasticity at the range of omega = 10(-3) to 10(0) rad.sec-1 were clearly changed after the treatments, and the magnitude of the relaxation and its main relaxation time were significantly increased. On the other hand, in Groups I, II & III, no significant changes of the frequency dependences were observed. These findings suggest that proteolytic enzymes administered orally work on the molecular structure of sputum, and break down their linkages between subunits of the structure. 相似文献
107.
N Shibata T Ichikawa M Tojo M Takahashi N Ito Y Okubo S Suzuki 《Archives of biochemistry and biophysics》1985,243(2):338-348
The mannans of Candida albicans NIH A-207 (A strain, serotype A), C. albicans NIH B-792 (B strain, serotype B), and C. albicans J-1012 (J strain, serotype C) prepared by fractional precipitation with cetyltrimethylammonium bromide (Cetavlon) were investigated for their immunochemical properties. Upon treatment with 10 mM HCl at 100 degrees C for 60 min, the mannans of A and B strains each released a mixture of manno-oligosaccharides ranging from hexaose to mannose together with (for each one) an acid-modified mannan, while J-strain mannan released lower oligosaccharides, tetraose to mannose. The acid-modified mannan of B strain did not show antibody-precipitating activity against homologous antiserum, whereas acid-modified A- and J-strain mannans retained most of this activity. The acid-released oligosaccharides were assumed to consist of beta-1,2-linked D-mannopyranosyl residues from the results of specific rotation and proton magnetic resonance studies. 相似文献
108.
Naotaka Hamasaki Kenji Izuhara Kenshi Okubo Yoko Kanazawa Akira Omachi Robert A. Kleps 《The Journal of membrane biology》1990,116(1):87-91
Summary The line widths of35Cl– nuclear magnetic resonances were used to measure chloride binding by Band 3. Since this procedure related directly to binding, the data obtained may be interpreted more unequivocally than affinities derived from kinetic data which could be related to either translocation or binding. Chloride binding to the active sites in Band 3 was assessed from that portion of the total line width which was sensitive to 4,4-dinitrostilbene-2,2-disulfonic acid. These sites appeared to be completely inhibited by treatment of erythrocyte membranes with diethylpyrocarbonate. This result is consistent with our previous observation that this reagent inhibits anion transport in resealed erythrocyte ghosts (Izuhara, Okubo & Hamasaki, 1989,Biochemistry
28:4725–4728). Hydroxylamine could not reverse the diethylpyrocarbonate inhibition of chloride binding to Band 3. The pH-dependence of diethylpyrocarbonate reactivity suggests that the modified residues may be those of histidine. 相似文献
109.
M Toda S Okubo H Ikigai T Shimamura 《Nihon saikingaku zasshi. Japanese journal of bacteriology》1990,45(2):561-566
Among catechins tested, (-)epigallocatechin (EGC), (-)epicatechin gallate (ECg), (-) epigallocatechin gallate (EGCg) inhibited the growth of Staphylococcus aureus, Vibrio cholerae O1 classical Inaba 569B and El Tor Inaba V86. S. aureus was more sensitive than V. cholerae O1 to these compounds. EGCg showed also a bactericidal activity against V. cholerae O1 569B. Pyrogallol showed a stronger antibacterial activity against S. aureus and V. cholerae O1 than tannic and gallic acid. Rutin or caffein had no effect on them. ECg and EGCg showed the most potent anti-hemolysin activity against S. aureus alpha-toxin, Vibrio parahaemolyticus thermostable direct hemolysin (Vp-TDH) and cholera hemolysin. Among catechin relatives, only tannic acid had a potent anti-hemolysin activity against alpha-toxin. These results suggest that the catechol and pyrogallol groups are responsible for the antibacterial and bactericidal activities, while the conformation of catechins might play an important role in the anti-hemolysin activity. 相似文献
110.
The effects of inspiratory flow rate and inflation volume on pulmonary mechanics were investigated in six anesthetized-paralyzed cats ventilated by constant-flow inflation. Pulmonary mechanics were assessed using the technique of rapid airway occlusion during constant-flow inflation which allows measurement of the intrinsic pulmonary resistance (RLmin) and of the overall "pulmonary flow resistance" (RLmax), which includes the additional pulmonary pressure losses due to time constant inequalities within the lung and/or stress adaptation. We observed that, at fixed inflation volume, 1) RLmin fitted Rohrer's equation, 2) RLmax was higher at low than intermediate flows, and 3) RLmax-RLmin decreased progressively with increasing flow. At fixed flow, RLmax increased, whereas RLmin decreased with increasing volume. We conclude that during eupneic breathing in cats, the pulmonary flow resistance as conventionally measured includes a significant component reflecting stress adaptation. 相似文献