全文获取类型
收费全文 | 3442篇 |
免费 | 181篇 |
国内免费 | 4篇 |
专业分类
3627篇 |
出版年
2022年 | 16篇 |
2021年 | 24篇 |
2020年 | 9篇 |
2019年 | 16篇 |
2018年 | 23篇 |
2017年 | 24篇 |
2016年 | 26篇 |
2015年 | 48篇 |
2014年 | 66篇 |
2013年 | 245篇 |
2012年 | 136篇 |
2011年 | 185篇 |
2010年 | 121篇 |
2009年 | 124篇 |
2008年 | 209篇 |
2007年 | 193篇 |
2006年 | 196篇 |
2005年 | 188篇 |
2004年 | 220篇 |
2003年 | 208篇 |
2002年 | 229篇 |
2001年 | 63篇 |
2000年 | 47篇 |
1999年 | 75篇 |
1998年 | 66篇 |
1997年 | 46篇 |
1996年 | 48篇 |
1995年 | 52篇 |
1994年 | 45篇 |
1993年 | 52篇 |
1992年 | 58篇 |
1991年 | 38篇 |
1990年 | 41篇 |
1989年 | 40篇 |
1988年 | 35篇 |
1987年 | 26篇 |
1986年 | 42篇 |
1985年 | 27篇 |
1984年 | 29篇 |
1983年 | 25篇 |
1982年 | 21篇 |
1981年 | 29篇 |
1980年 | 25篇 |
1979年 | 21篇 |
1978年 | 14篇 |
1977年 | 17篇 |
1976年 | 19篇 |
1975年 | 28篇 |
1974年 | 21篇 |
1973年 | 17篇 |
排序方式: 共有3627条查询结果,搜索用时 0 毫秒
91.
Nobutaka Takahashi Akinori Suzuki Yasuo Kimura Satoshi Miyamoto Saburo Tamura Takashi Mitsui 《Bioscience, biotechnology, and biochemistry》2013,77(9):1115-1122
Piericidin B was isolated from mycellia of Streptomyces mobaraensis besides piericidin A. On the basis of IR, NMR and mass spectral studies together with chemical evidences, its structure was assigned as Id. Its physiological activities are also deescribd. 相似文献
92.
An inulinase was highly purified from the culture broth of Penicillium purpurogenum by chromatographies on DEAE-Sepharose CL-6B, Toyopearl HW-65, and Bio-Gel P-100. The enzyme was homogeneous by disc electrophoretic analysis. The molecular weight was 6.4 × 104 by SDS-disc electrophoresis and gel filtration on Bio-Gel P-150. The isoelectric point was pH 3.6 by isoelectric focusing. The enzyme hydrolyzed inulin rapidly, but did not affect sucrose. By paper chromatography analysis, the major products from inulin were tri-, tetra-, penta-, and hexa-saccharides. The substrate specificity of the enzyme on hydrolyses of fructo-oligosaccharides[1F(1-β-d-fructofuranosyl)n sucrose (n = 1 to 6 and n (average of polymerization degree) = 8)] were examined. The Km values and relative maximum velocities for the hydrolyses of inulin and fructo-oligosaccharides (GFn, n = 2 to 7 and n = 9) were as follows: inulin, (DP = 35) 0.21 mM and 100; GF9, 0.24 mM and 86.5; GF7, 0.33 mM and 132; GF6, 0.85 mM and 71.2; GF5, 3.8 mM and 25.4; GF4, 2.8 mM and 28.8; GF3, (nystose) 16 mM and 0.8; GF2 (1-kestose), 8.4 mM and 0.2. The molecular activities for the hydrolyses of fructo-oligosaccharides (GFn, n = 2 to 6) were increased depending on the degree of polymerization of fructosyl residues, and were nearly constant if the polymerization degree was over seven. These results strongly suggested that the endo-type inulinase from Penicillium purpurogenum had a subsite structure consisting of at least seven subsites. 相似文献
93.
94.
The process of dehydration of soybean protein coagulate in expression involves two mechanisms, filtration and consolidation. The filtration process was explained by Ruth’s filtration model. The consolidation process, except for secondary consolidation, was analyzed by the modified consolidation model of Shirato et al., taking into account the compressibility of cake. The modified coefficient of consolidation was not affected significantly by the pressure applied. Evaluation of the modified coefficient of consolidation is of importance for an attempt to improve the current production of soybean protein. 相似文献
95.
Hideyuki Tanaka Yasuo Nakatomi Masaji Ogura 《Bioscience, biotechnology, and biochemistry》2013,77(11):3087-3093
The metabolic fates of the carbon skeletons of [U-14C]glycine and l-[U-14C]threonine were investigated in growing rats fed with diets containing different percentages of protein calories (0, 5, 10, 15, and 30PC%) at 4100 kcal of metabolizable energy per kg of diet.The incorporation of 14C into the body protein at 12 hr after the injection of 14C-glycine was about 58% of the dose in rats fed with the 10 or 15 PC% diet, and the values were reduced in both the lower and higher PC% groups. A considerable amount of 14C was recovered in the soluble fraction, and it was attributed to labeled glycine and serine in the free amino acid pools of the tissues.The incorporation of 14C into the body protein from 14C-threonine was extremely high in the dietary groups of 0 to 10 PC%, and it decreased in the 30PC% group. Conversely, the expired 14C02 production was much less until the dietary protein level reached at 10PC%, and it increased with higher PC% in the diets. The change in the activity of hepatic threonine dehydratase in rats fed diets with increasing protein levels was similar to that of the expired 14C02 production from 14C- threonine.These results indicate that, though the metabolic patterns for glycine and threonine differ from each other, their responses to dietary protein levels change at 10 to 15 PC%, where the growth rate reached its approximate maximum. 相似文献
96.
97.
Yasuo Kitagawa Etsuro Sugimoto Hideo Chiba 《Bioscience, biotechnology, and biochemistry》2013,77(1):199-206
The amino acid composition of beef liver d-glycerate dehydrogenase (EC 1.1.1.29) was determined. Results of sodium dodecyl sulfate gel electrophoresis and measurements of the number of NADH bound by the enzyme and the number of the essential sulfhydryl groups suggested that the enzyme was composed of two identical subunits with the molecular weight of 36,000. Close relation between the essential sulfhydryl groups and the coenzyme binding site was also suggested. Effect of an alkylating agent (bromopyruvate) with the structure similar to the substrate was studied. Effects of iodoacetate and iodoacetamide were also studied. It was suggested that these reagents behaved as active-site-directed irreversible inhibitors of the enzyme. Bromopyruvate exhibited a high affinity to the enzyme. Iodoacetate (anionic reagent) had a higher affinity than iodoacetamide (neutral reagent). 相似文献
98.
Enzymes for ecdysteroid biosynthesis: their biological functions in insects and beyond 总被引:1,自引:0,他引:1
Steroid hormones are responsible for the coordinated regulation of many aspects of biological processes in multicellular organisms. Since the last century, many studies have identified and characterized steroidogenic enzymes in vertebrates, including mammals. However, much less is known about invertebrate steroidogenic enzymes. In the last 15?years, a number of steroidogenic enzymes and their functions have been characterized in ecdysozoan animals, especially in the fruit fly Drosophila melanogaster. In this review, we summarize the latest knowledge of enzymes crucial for synthesizing ecdysteroids, the principal insect steroid hormones. We also discuss the functional conservation and diversity of ecdysteroidogenic enzymes in other insects and even non-insect species, such as nematodes, vertebrates, and lower eukaryotes. 相似文献
99.
l-Glutamic acid was formed from d-, l-, and dl-PCA with cell-free extract of Pseudomonas alcaligenes ATCC-12815 grown in the medium containing dl-PCA as a sole source of carbon and nitrogen. The enzyme(s) involved in this conversion reaction was distributed in the soluble fraction within the cell and in 0.5 saturated fraction at the fractionation procedure with the saturation of ammonium sulfate. Optimum pH of this enzyme(s) lied at pH 8.5 and optimum temperature was 30°C. Cu (5 × 10?3 m) inhibited the reaction considerably while Ca or Fe accelerated it. PALP (1×10?3 m) also gave an enhanced activity to some extent. The enzyme preparation converted dextro-rotatory enan-thiomorph of PCA to its laevo-rotatory one which in turn was not converted to the opposite rotation direction by this enzyme. Furthermore, the preparation did not, if any, show d-glutamic acid racemase activity. Isotopic experiments with using dl-PCA-1-14C revealed that l-glutamic acid-1-14C was formed by the cleavage of –CO–NH– bond of pyrrolidone ring of PCA. It was concluded that dl-PCA when assimilated by the present bacterium is at first transformed to l-PCA by the optically isomerizing enzyme and subsequently is cleaved to l-glutamic acid probably by the PCA hydrolysing enzyme. 相似文献
100.
Kazuki Sato Hiroyuki Anaguchi Komei Kobayashi Taeko Morinaga Naoyuki Nishimura Yasuo Kobayashi 《Bioscience, biotechnology, and biochemistry》2013,77(8):2047-2053
Temperature-sensitive sporulation mutants were isolated spontaneously from Bacillus subtilis 168 TT by a sequential transfer method. A representative mutant strain, ts32, was characterized in detail. The mutant grew normally at 30°C and 42°C, but did not sporulate at 42°C. Electron microscopic observation and physiological analysis showed that the mutant was blocked at stage 0-1 of sporulation. Genetic analysis suggested that the mutation was located at the spo0B locus on the B. subtilis chromosome. Temperature-shift experiments clearly showed that the spo0B gene product functions only at the beginning of sporulation. 相似文献