全文获取类型
收费全文 | 1046篇 |
免费 | 44篇 |
国内免费 | 60篇 |
专业分类
1150篇 |
出版年
2023年 | 5篇 |
2022年 | 11篇 |
2021年 | 11篇 |
2020年 | 13篇 |
2019年 | 25篇 |
2018年 | 14篇 |
2017年 | 12篇 |
2016年 | 18篇 |
2015年 | 17篇 |
2014年 | 57篇 |
2013年 | 67篇 |
2012年 | 36篇 |
2011年 | 66篇 |
2010年 | 58篇 |
2009年 | 68篇 |
2008年 | 68篇 |
2007年 | 53篇 |
2006年 | 59篇 |
2005年 | 42篇 |
2004年 | 59篇 |
2003年 | 31篇 |
2002年 | 27篇 |
2001年 | 20篇 |
2000年 | 19篇 |
1999年 | 26篇 |
1998年 | 31篇 |
1997年 | 19篇 |
1996年 | 15篇 |
1995年 | 16篇 |
1994年 | 18篇 |
1993年 | 11篇 |
1992年 | 21篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1989年 | 14篇 |
1988年 | 6篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 23篇 |
1984年 | 2篇 |
1983年 | 6篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 7篇 |
1978年 | 8篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 2篇 |
排序方式: 共有1150条查询结果,搜索用时 15 毫秒
101.
Christine De Paillerets Jacques Gallay Michel Vincent Monique Rogard Annette Alfsen 《生物化学与生物物理学报:生物膜》1981,644(1):134-142
The lipid dynamics of the adrenocortical microsomal membranes was studied by monitoring the fluorescence anisotropy and excited state lifetime of a set of anthroyloxy fatty acid probes (2-, 7-, 9- and 12-(9-anthroyloxy)-stearic acid (AP) and 16-(9-anthroyloxy)palmitic acid (AS). It was found that a decreasing polarity gradient from the aqueous membrane interface to the membrane interior, was present. This gradient was not modified by the proteins, as evidenced by comparison of complete membranes and derived liposomes, suggesting that the anthroyloxy probes were not in close contact with the proteins. An important change of the value of the mean rotational relaxation time as a function of the position of the anthroyl ring along the acyl chain was evidenced. In the complete membranes, a relatively more fluid medium was evidenced in the C16 as compared to the C2 region, while the rotational motion appeared to be the most hindered at the C7–C9 level. In the derived liposomes, a similar trend was observed but the mobility was higher at all levels. The decrease of the mean rotational relaxation time was more important for 12-AS and 16-AP. Temperature dependence of the mean rotational relaxation time of 2-AS, 12-AS and 16-AP in the complete membranes revealed the existence of a lipid reorganization occurring around 27°C and concerning mainly the C16 region. The extent to which the acyl chain reacted to this perturbation at the C12 level depended on pH. The presence of proteins increased the apparent magnitude of this reorganization and also modified the critical temperature from approx. 23°C in the derived liposomes to approx. 27°C in the complete membranes. Thermal dependence of the maximum velocity of the , the second enzyme in the enzymatic sequence, responsible for the biosynthesis of the in the adrenal cortex microsomes, was studied. The activation energy of the catalyzed reaction was found to be low and constant () in the temperature range 16–40°C at pH 7.5, 8.5 and 9, corresponding to the minimum, intermediate and maximum rate, respectively. A drastic increase of the activation energy () was observed at temperature below 16°C at pH 7.5. A correlated change of the as function of temperature was detected; at 36°C while at 13°C the value shifted to 8.7. The pH range of the group ionization was narrower at 13°C. In contrast with the behaviour of the , the was apparently unaffected by the lipid reorganization at 27°C. It is suggested that this enzyme possesses a different and more fluid lipid environment than the bulk lipids. 相似文献
102.
103.
104.
为了研究甘露糖正向筛选体系在巨尾桉遗传转化过程中的有效性,构建了以6-磷酸甘露糖异构酶(6-phosphomannose isomerase,PMI)为筛选标记的pCAMBIA1301植物表达载体,并将该载体通过农杆菌介导的遗传转化转入木本植物巨尾桉中。将获得的阳性植株通过氯酚红(chlorophenol red,CPR)法及PCR检测,桉树遗传转化的阳性率达到26.09%。另外,通过正交试验优化法,对巨尾桉组培快繁体系建立过程中不同浓度激素配比进行了研究,建立起良好的巨尾桉组织培养再生体系,由甘露糖筛选敏感性测试,获得了巨尾桉筛选临界浓度,蔗糖与甘露糖比例为19∶11,优化了巨尾桉遗传转化体系,为今后巨尾桉组织培养与遗传转化研究提供了重要的参考依据。 相似文献
105.
Families of Czech Landrace (94 litters and 636 offspring) were tested for halothane sensitivity, A-O (S), H, PHI and PGD phenotypes. Informative matings for the estimation of recombination rates between marker loci were selected. The following recombination frequencies were established: S-Phi = 4.8 % (2.5 % -10.7 %);S-H = 6.8 % (4.3 %-11.7 %); Phi-H = 2.6 % (0.9 %-5.3 9%); H-Pgd = 4.4 % (1.6 %-8.0 %). CCCC-overs were observed also between S- Hal, Hal-H andHal - Pgd, but were not found between Phi - Hal. On the basis of these results it has been possible to revise the position of the S locus in this linkage group. The most probable gene order would be: S - Phi - Hal (or Hal - Phi) -H- (P02) - Pgd.
A striking difference was found between the number of halothane-sensitive pigs (87) and Haln Hal n genotypes determined by haplotyping (123). Segregation rates in 19 backcross matings and experimental matings of the animals proved that this difference is mostly due to incomplete CCC or low expression of halothane sensitivity. 相似文献
A striking difference was found between the number of halothane-sensitive pigs (87) and Hal
106.
Xueping Chen Xiaosha Zhang Chen Li Teng Guan Huifang Shang Liying Cui Xin‐Min Li Jiming Kong 《Journal of neurochemistry》2013,124(1):45-58
A major hallmark of mutant superoxide dismutase (SOD1)‐linked familial amyotrophic lateral sclerosis is SOD1‐immunopositive inclusions found within motor neurons. The mechanism by which SOD1 becomes aggregated, however, remains unclear. In this study, we aimed to investigate the role of nitrosative stress and S‐nitrosylation of protein disulfide isomerase (PDI) in the formation of SOD1 aggregates. Our data show that with disease progression inducible nitric oxide synthase (iNOS) was up‐regulated, which generated high levels of nitric oxide (NO) and subsequently induced S‐nitrosylation of PDI in the spinal cord of mutant SOD1 transgenic mice. This was further confirmed by in vitro observation that treating SH‐SY5Y cells with NO donor S‐nitrosocysteine triggered a dose‐dependent formation of S‐nitrosylated PDI. When mutant SOD1 was over‐expressed in SH‐SY5Y cells, the iNOS expression was up‐regulated, and NO generation was consequently increased. Furthermore, both S‐nitrosylation of PDI and the formation of mutant SOD1 aggregates were detected in the cells expressing mutant SOD1G93A. Blocking NO generation with the NOS inhibitor N‐nitro‐l ‐arginine attenuated the S‐nitrosylation of PDI and inhibited the formation of mutant SOD1 aggregates. We conclude that NO‐mediated S‐nitrosylation of PDI is a contributing factor to the accumulation of mutant SOD1 aggregates in amyotrophic lateral sclerosis. 相似文献
107.
《Bioscience, biotechnology, and biochemistry》2013,77(6):1340-1343
A variant of P450 BM3 with an F87V substitution [P450 BM3 (F87V)] is a substrate-promiscuous cytochrome P450 monooxygenase. We investigated the bioconversion of various flavonoids (favanones, chalcone, and isoflavone) by using recombinant Escherichia coli cells, which expressed the gene coding for P450 BM3 (F87V), to give their corresponding hydroxylated products. Potent antioxidative activities were observed in some of the products. 相似文献
108.
Hajime Katano Masahiro Takakuwa Takafumi Itoh 《Bioscience, biotechnology, and biochemistry》2013,77(7):1057-1060
A colorimetric method for the reducing monosaccharide determination is optimized for the assay of glucose isomerase, which converts glucose (Glc) to fructose (Fru). Test solution was mixed with 20-fold volume of the 50 mM Na2SiO3, 600 mM Na2MoO4, and 0.95 M HCl aqueous solution (pH 4.5), in which a yellow molybdosilicate species was formed. The mixture was kept at 70 °C for 30 min. Test solution containing 10 mM level Fru gave a remarkable blue reaction mixture, in which the Mo(VI) species was reduced by Fru to form a blue molybdosilicate species. The blueness increased with the Fru concentration. Glc cannot render the reaction mixture blue as strong as Fru. Thus, the colorimetric method can be used advantageously for the determination of 10 mM level Fru in the Glc isomerase reaction mixture, even in the presence of 100 mM level Glc, and has been applied successfully to the microtiter plate assay of the enzyme. 相似文献
109.
《Bioscience, biotechnology, and biochemistry》2013,77(10):2174-2180
Some characteristics of phosphoglucose isomerase (PGI, EC 5.3.1.9) from banana were measured during fruit ripening of three banana cultivars. In banana, PGI was present as two dimeric isoenzymes, named PGI1 and PGI2, which had similar native molecular masses but differed in relation to heat stability and isoelectric point. Total PGI activity showed a distinct two-step change during fruit ripening. Before the climacteric period, PGI activity gradually decreased with the starch content, then its activity began to increase with sucrose accumulation. The ratio of PGI1, and PGI2 was constant, indicating that both enzymes would be involved in starch degradation and sucrose synthesis. PGI activity and changes in carbohydrate composition suggests the existence of some control to fit the requirements of the intense carbon flow from starch to sucrose. 相似文献
110.
Yasuo Aizono Masaru Funatsu Yukio Fujiki Masayoshi Watanabe 《Bioscience, biotechnology, and biochemistry》2013,77(2):317-324
A species of rice bran lipase (lipase II) was purified by ammonium sulfate precipitation, followed by successive chromatographies on DEAE-cellulose, Sephadex G–75 and CH-Sephadex C–50. Both polyacrylamide disc electrophoresis and ultracentrifugation demonstrated that the enzyme protein is homogeneous. The isoelectric point of the enzyme was 9.10 by ampholine electrophoresis. The sedimentation coefficient of the enzyme was evaluated to be 2.60 S, and the molecular weight to be 33,300 according to Archbald’s method. The enzyme showed the optimum pH between 7.5 and 8.0, and the optimum temperature at about 27°C. It was stable over the pH range from 5 to 9.5 and below 30°C. In substrate specificity, the enzyme exhibited a high specificity toward triglycerides having short-carbon chain fatty acids, although it was capable of hydrolyzing the ester bonds in the rice and olive oil. 相似文献