全文获取类型
收费全文 | 188篇 |
免费 | 10篇 |
专业分类
198篇 |
出版年
2017年 | 2篇 |
2015年 | 6篇 |
2014年 | 5篇 |
2013年 | 21篇 |
2012年 | 7篇 |
2011年 | 2篇 |
2010年 | 8篇 |
2009年 | 4篇 |
2008年 | 4篇 |
2007年 | 9篇 |
2006年 | 10篇 |
2005年 | 15篇 |
2004年 | 9篇 |
2003年 | 6篇 |
2002年 | 8篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
1941年 | 4篇 |
1940年 | 1篇 |
1939年 | 1篇 |
1937年 | 2篇 |
1936年 | 1篇 |
1935年 | 3篇 |
1934年 | 2篇 |
1933年 | 4篇 |
排序方式: 共有198条查询结果,搜索用时 0 毫秒
1.
Seizaburo Shiraga Masayuki Kawakami Masaji Ishiguro Mitsuyoshi Ueda 《Applied microbiology》2005,71(8):4335-4338
Immobilization of enzymes on some solid supports has been used to stabilize enzymes in organic solvents. In this study, we evaluated applications of genetically immobilized Rhizopus oryzae lipase displayed on the cell surface of Saccharomyces cerevisiae in organic solvents and measured the catalytic activity of the displayed enzyme as a fusion protein with α-agglutinin. Compared to the activity of a commercial preparation of this lipase, the activity of the new preparation was 4.4 × 104-fold higher in a hydrolysis reaction using p-nitrophenyl palmitate and 3.8 × 104-fold higher in an esterification reaction with palmitic acid and n-pentanol (0.2% H2O). Increased enzyme activity may occur because the lipase displayed on the yeast cell surface is stabilized by the cell wall. We used a combination of error-prone PCR and cell surface display to increase lipase activity. Of 7,000 colonies in a library of mutated lipases, 13 formed a clear halo on plates containing 0.2% methyl palmitate. In organic solvents, the catalytic activity of 5/13 mutants was three- to sixfold higher than that of the original construct. Thus, yeast cells displaying the lipase can be used in organic solvents, and the lipase activity may be increased by a combination of protein engineering and display techniques. Thus, this immobilized lipase, which is more easily prepared and has higher activity than commercially available free and immobilized lipases, may be a practical alternative for the production of esters derived from fatty acids. 相似文献
2.
Masaji Koshioka Shigeru Hisajima Richard P. Pharis Noboru Murofushi 《Bioscience, biotechnology, and biochemistry》2013,77(9):2627-2631
Gibberellin A5 (GA5), a native GA of immature seeds of Pharbitis nil, was fed to Pharbitis nil cell suspension cultures as [C-l, 3H] GA5 (3.1 Ci/mmol), and its metabolism over a 48 hr period was investigated. Radioactivity in free GA metabolites was 13.1%, with 79.9% in GA glucosyl conjugate-like metabolites. Only 7.0% of the radioactivity remained as [3H] GA5. Tentative identifications were based on comparison with retention times of authentic free GAs and/or glucosyl conjugates after sequential chromatography on Si gel partition column → gradient-eluted C18 HPLC-radiocounting (RC) → isocratic-eluted C18 HPLC-RC, and showed that [3H] GA5 was converted to [3H] GA1 (2%), [3H] GA3 (4%), [3H] GA6 (2%), [3H] GA22 (1%) and their glucosyl conjugates, and also to [3H] GA8 glucoside, and [3H] GA5 glucosyl conjugates. The major conjugate-like substances were [3H] GA1 and [3H] GA3 glucosyl esters, at 15% and 34%, respectively, of the total extractable radioactivity. 相似文献
3.
Zaprinast, a well-known cyclic guanosine monophosphate-specific phosphodiesterase inhibitor, is an agonist for GPR35 总被引:1,自引:0,他引:1
We found that zaprinast, a well-known cyclic guanosine monophosphate-specific phosphodiesterase inhibitor, acted as an agonist for a G protein-coupled receptor, GPR35. In our intracellular calcium mobilization assay, zaprinast activated rat GPR35 strongly (geometric mean EC(50) value of 16nM), whereas it activated human GPR35 moderately (geometric mean EC(50) value of 840nM). We also demonstrated that GPR35 acted as a Galpha(i/o)- and Galpha(16)-coupled receptor for zaprinast when heterologously expressed in human embryonic kidney 293 (HEK 293) cells. These findings will facilitate the research on GPR35 and the drug discovery of the GPR35 modulators. 相似文献
4.
Barthet G Gaven F Framery B Shinjo K Nakamura T Claeysen S Bockaert J Dumuis A 《The Journal of biological chemistry》2005,280(30):27924-27934
The 5-hydroxytryptamine type 4 receptors (5-HT4Rs) are involved in memory, cognition, feeding, respiratory control, and gastrointestinal motility through activation of a G(s)/cAMP pathway. We have shown that 5-HT4R undergoes rapid and profound homologous uncoupling in neurons. However, no significant uncoupling was observed in COS-7 or HEK293 cells, which expressed either no or a weak concentration of GRK2, respectively. High expression of GRK2 in neurons is likely to be the reason for this difference because overexpression of GRK2 in COS-7 and HEK293 cells reproduced rapid and profound uncoupling of 5-HT4R. We have also shown, for the first time, that GRK2 requirements for uncoupling and endocytosis were very different. Indeed, beta-arrestin/dynamin-dependent endocytosis was observed in HEK293 cells without any need of GRK2 overexpression. In addition to this difference, uncoupling and beta-arrestin/dynamin-dependent endocytosis were mediated through distinct mechanisms. Neither uncoupling nor beta-arrestin/dynamin-dependent endocytosis required the serine and threonine residues localized within the specific C-terminal domains of the 5-HT4R splice variants. In contrast, a cluster of serines and threonines, common to all variants, was an absolute requirement for beta-arrestin/dynamin-dependent receptor endocytosis, but not for receptor uncoupling. Furthermore, beta-arrestin/dynamin-dependent endocytosis and uncoupling were dependent on and independent of GRK2 kinase activity, respectively. These results clearly demonstrate that the uncoupling and endocytosis of 5-HT4R require different GRK2 concentrations and involve distinct molecular events. 相似文献
5.
Immobilization of enzymes on some solid supports has been used to stabilize enzymes in organic solvents. In this study, we evaluated applications of genetically immobilized Rhizopus oryzae lipase displayed on the cell surface of Saccharomyces cerevisiae in organic solvents and measured the catalytic activity of the displayed enzyme as a fusion protein with alpha-agglutinin. Compared to the activity of a commercial preparation of this lipase, the activity of the new preparation was 4.4 x 10(4)-fold higher in a hydrolysis reaction using p-nitrophenyl palmitate and 3.8 x 10(4)-fold higher in an esterification reaction with palmitic acid and n-pentanol (0.2% H2O). Increased enzyme activity may occur because the lipase displayed on the yeast cell surface is stabilized by the cell wall. We used a combination of error-prone PCR and cell surface display to increase lipase activity. Of 7,000 colonies in a library of mutated lipases, 13 formed a clear halo on plates containing 0.2% methyl palmitate. In organic solvents, the catalytic activity of 5/13 mutants was three- to sixfold higher than that of the original construct. Thus, yeast cells displaying the lipase can be used in organic solvents, and the lipase activity may be increased by a combination of protein engineering and display techniques. Thus, this immobilized lipase, which is more easily prepared and has higher activity than commercially available free and immobilized lipases, may be a practical alternative for the production of esters derived from fatty acids. 相似文献
6.
Annual production rates of reproductive organs inFagus crenata forests in the lower area of the species' range were studied using 10 litter traps in 1980–1986. The production rates of
dispersed pollen were estimated by multiplying the number of fallen male inflorescences per ha per year by the mean amount
of pollen per inflorescence before anthesis. Large annual fluctuations in the production rates of male and female inflorescences
were recognized, whereas their annual trends were synchronized with each other. Pollen production rates were within the range
1.0–6900 (mean: 1630)×109ha−1 yr−1, the maximum/minimum ratio attaining 7000.F. crenata was the lowest producer of pollen among seven tree species studied: the number of pollen grains equivalent to a single ovule
was in the range 6.0–14×104. Furthermore, the mean dry weight of a single pollen grain (3.77×10−5mg) was higher than for wind-pollinated species. Three factors seemed to cause the low seed fertility ofF. crenata. The dry-matter production rate in the best seed year reached 3252 kg ha−1 yr−1, of which pollen accounted for 259 kg ha−1 yr−1. Unproductive years with less than 10% of the maximum production occurred four times in a 7-yr period. In such years there
were fewer male and female inflorescences, and more fruit dropped as a result of insect damage. Lower nut dissemination would
play an important role in suppressing any increase in nut predators, and fewer flowers would be produced to avoid wastage
of photosynthates in a cool-temperate climate. 相似文献
7.
8.
Masaji Koshioka Alan Jones Mayumi N. Koshioka Richard P. Pharis 《Phytochemistry》1983,22(7):1585-1590
The native gibberellin A4 (GA4), in radioactive form ([1,2-3H]GA4, 1.06 Ci/mmol), was fed to carrot somatic cell cultures (suspension and immobilized cell systems) and its metabolism over a 48 hr period was investigated. It was found that the [3H]GA4 was metabolized to at least two GAs, [3H]GA1 and [3H]GA8, six GA glucosyl conjugates, [3H]GA1-0(3)-glucoside, [3H]GA1-0(13)-glucoside, [3H]GA1-glucosyl ester, [3H]GA4-glucoside, [3H]GA4-glucosyl ester, a [3H]GA8 glucosyl conjugate(s) and a previously unknown [3H]GA1 glucosyl conjugate ([3H]GA1-0(3,13)-diglucoside-like compound). The GA1-diglucoside-like compound was found only in extracts of cells and was present in significant amounts (33 % of total extractable radioactivity). All other metabolites were present in both cells and medium. For extracts of the medium, no differences between the suspension and immobilized cultures existed in types of [3H]GA4 metabolites although quantitative differences were apparent. 相似文献
9.
Localization of arachidonate 12-lipoxygenase in parenchymal cells of porcine anterior pituitary 总被引:2,自引:0,他引:2
N Ueda A Hiroshima K Natsui F Shinjo T Yoshimoto S Yamamoto K Ii K Gerozissis F Dray 《The Journal of biological chemistry》1990,265(4):2311-2316
12-Lipoxygenases oxygenate arachidonic acid producing its 12S-hydroperoxy derivative and are well known as platelet and leukocyte enzymes. When a peroxidase-linked immunoassay of the enzyme according to the avidin-biotin method was applied to the cytosol fractions from various parts of porcine brain, a considerable amount of the enzyme was found in the anterior pituitary. The enzyme level (about 200 ng/mg cytosol protein) corresponded to about 6% of the enzyme content in porcine peripheral leukocytes. Posterior and intermediate lobes showed about one-tenth of the enzyme level of anterior pituitary. Other parts of porcine brain contained the 12-lipoxygenase in amounts below 7 ng/mg cytosol protein. The cytosol fraction (0.7 mg of protein) of anterior pituitary produced 12S-hydroxy-5,8,10,14-eicosatetraenoic acid from 25 microM arachidonic acid in about 34% conversion at 24 degrees C for 5 min, giving a specific enzyme activity about 3 nmol/min/mg protein. Furthermore, various octadecapolyenoic acids were oxygenated almost as fast as the arachidonate 12-oxygenation. When anterior pituitary was investigated immunohistochemically with anti-12-lipoxygenase antibody, most of the immunostained cells were certain parenchymal cells with granules, which were not blood cells. These biochemical and immunohistochemical results provide a good reason for considering that 12-lipoxygenase does play an important role in pituitary function. 相似文献
10.
Takuya Tsunoda Hiroshi Tanimura Hiroki Yamaue Makoto Iwahashi Masaji Tani Mikoko Tamai Kazuo Arii Kohei Noguchi 《Biotherapy》1992,4(1):9-15
In adoptive immunotherapy, the number of effector cells is one of the major factors relating to the therapeutic efficacy. We demonstrated that tumor-infiltrating lymphocytes (TILs) were stimulated to proliferate by incubation with interleukin 2 (IL-2) plus interleukin 4 (IL-4). TILs cultured with IL-2 plus IL-4 increased 3.1-fold more than TILs cultured with IL-2 alone. However, IL-4 did not alter the cytotoxic activity of TILs against autologous tumor cells and established tumor cell lines. It is suggested that IL-2 receptor is related to the mechanism of the proliferation of activated TILs cultured by combination with IL-2 and IL-4. Thus, the combination of IL-2 and IL-4 may increase the efficacy of adoptive immunotherapy using activated TILs. 相似文献