首页 | 官方网站   微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   82篇
  免费   6篇
生物科学   88篇
  2024年   1篇
  2023年   3篇
  2022年   5篇
  2021年   1篇
  2020年   6篇
  2019年   7篇
  2018年   10篇
  2017年   6篇
  2016年   1篇
  2015年   2篇
  2014年   3篇
  2013年   7篇
  2012年   5篇
  2011年   7篇
  2010年   2篇
  2009年   7篇
  2007年   2篇
  2006年   4篇
  2005年   3篇
  2004年   1篇
  2002年   2篇
  2001年   1篇
  1982年   1篇
  1977年   1篇
排序方式: 共有88条查询结果,搜索用时 0 毫秒
61.
Molecular Biology Reports - Cellulases like endoglucanase II (EGII) from Trichoderma reesei are the industrial enzymes responsible for breakdown of cellulosic materials. Due to its importance for...  相似文献   
62.
Killer cell immunoglobulin-like receptors (KIR) regulate natural killer cell response against infection and malignancy. KIR genes are variable in the number and type, thereby discriminating individuals and populations. Herein, we analyzed the KIR gene content diversity in four native populations of Iran. The KIR genomic diversity was comparable between Bakhtiari and Persian and displayed a balance of A and B KIR haplotypes, a trend reported in Caucasian and African populations. The KIR gene content profiles of Arab and Azeri were comparable and displayed a preponderance of B haplotypes, a scenario reported in the natives of America, India, and Australia. A majority of the B haplotype carriers of Azeri and Arab had a centromeric gene-cluster (KIR2DS2-2DL2-2DS3-2DL5). Remarkably, this cluster was totally absent from the American natives but occurred at highest frequencies in the natives of India and Australia in combination with another gene cluster at the telomeric region (KIR3DS1-2DL5-2DS5-2DS1). Therefore, despite having similar frequencies of B haplotypes, the occurrence of B haplotype-specific KIR genes, such as 2DL2, 2DL5, 3DS1, 2DS1, 2DS2, 2DS3, and 2DS5 in Azeri and Arab were substantially different from the natives of America, India, and Australia. In conclusion, each Iranian population exhibits distinct KIR gene content diversity, and the Indo-European KIR genetic signatures of the Iranians concur with geographic proximity, linguistic affinity, and human migrations. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   
63.
64.
The effects of iron nanoparticles and salicylic acid (SA) on strawberry (Fragaria?×?ananassa Duch.) plants in conditions of drought stress were surveyed under in vitro conditions to find the optimum combination for strawberry tissue culture. Cuttings of the Queen Elisa cultivar were surveyed in a three-way factorial experiment with three replications in 2015. The results showed that drought stress significantly affected all measured parameters of strawberry plantlets under in vitro condition in a negative way. SA compensated for the negative effects of drought stress on strawberry plantlets and improved their growth parameters under in vitro culture. Strawberry plantlets treated with iron nanoparticles were able to cope with stressful conditions better than untreated ones. This study found that iron, a micronutrient in plant growth and in vitro development, greatly influenced the plantlets’ growth parameters and other measured traits. These results indicate that the efficiency of tissue culture and in vitro culture of strawberries could be improved by increased application of iron in the form of nanoparticles. The results might also indicate that the application of iron nanoparticles along with SA can be a useful method for providing higher quantity and quantity in the in vitro culture of strawberries, and could be used for adapting strawberry plants to drought before transplanting them in the field.  相似文献   
65.
The effects of long term salinity on some morpho-physiological characteristics were studied in strawberry Kurdistan and Queen elisa cultivars. Vegetative and biochemical traits were measured in strawberry cultivars subjected to three levels of salinity including 0, 40 and 80 mM at 20, 40 and 60th days after NaCl addition. Results showed that in both cultivars the dry weight of plant organs decreased in response to NaCl, except of crown weight in cv. Kurdistan. Root to shoot ratio increased due to a greater reduction in above ground biomass under salinity. Strawberry cultivars tended to decrease their stomatal conductance, RWC, proline, soluble carbohydrates and proteins during the different evaluation periods. Compared to the 20th day, peroxidase activity decreased at 80 mM during 40 and 60 days in cv. Queen elisa. On the contrary, ascorbate peroxidase activity elevated until the 40th day and decreased afterwards, in addition application of 40 and 80 mM NaCl increased the ascorbate peroxidase activity of both studied cultivars. Catalase activity increased from 20th until 60th days in cv. Queen elisa, while showed increase in cv. Kurdistan until day 40 and then decreased again at day 60. Application of 40 and 80 mM NaCl resulted in an increase in peroxidase, ascorbate peroxidase and catalase activities of both cultivars. The Queen elisa cv. showed lower tolerance index (45.88%) compared with cv. Kurdistan (67.97%). Finally, higher salinity resistance of cv. Kurdistan is probably associated with its ability to maintain higher RWC and higher activity of antioxidant enzymes.  相似文献   
66.
Summary The yield data of 39 cultivars of diverse commercial classes of beans (Phaseolus vulgaris L.) planted in seven locations in Michigan were subjected to cluster and canonical variate analyses. The essential findings and conclusions can be summarized as follows: (1) Cluster analysis classified the cultivars into sub-sets or clusters almost identically coinciding with their commercial class designation. Canonical variate analysis completely confirmed the sub-groupings. Within class similarities were attributed to a narrow genetic base resulting from a common genetic relationship, or at least sharing of a common gene pool. (2) It was found that two clusters could possess almost identical mean (cluster mean) yields, and deviate in opposite directions over the same range of environments. (3) When total genotype × environmental interaction variance was partitioned into between and within clusters, the cluster × environment portion constituted 80% of the total. (4) These results imply that if the behavior of a given cultivar across a series of environments is known, the behavior of all other members of the class across a similar range of environments would be predictable.Journal Article No. 10329 of the Michigan Agricultural Experiment Station  相似文献   
67.
In the present work, the influence of Cu+ binding to N3- and N7-positions of hypoxanthine on energetic, geometrical and topological properties of hypoxanthine–guanine, hypoxanthine–adenine, hypoxanthine–cytosine, hypoxanthine–thymine and hypoxanthine–hypoxanthine mismatches is theoretically investigated. The calculations, in gas phase, are performed at B3LYP/6-311++G(3df,3pd) level of theory. Unlike the other mispairs, Cu+ binding to N3-position of hypoxanthine causes the proton transfer process from enol form of hypoxanthine to imino forms of adenine and cytosine. This process also occurs in all mismatches having enol form of hypoxanthine when Cu+ binds to N7-position of hypoxanthine. The mismatches are stabilized by hydrogen bonds. The influence of Cu+ on hydrogen bonds is also examined by atoms in molecules (AIM) and natural bond orbital (NBO) analyses.

Communicated by Ramaswamy H. Sarma  相似文献   

68.
Immunomodulatory function of bone marrow derived mesenchymal stem cells in cancer has recently been investigated. But the resident mesenchymal stem cells as whole in cancer and in the breast cancer tissue have not been studied well. In the present work we isolated adipose derived stem cells (ASCs) from breast cancer and normal breast tissues to investigate the expressions of IL-4, IL-10 and transforming growth factor (TGF)-β1 in ASCs and to see if ASCs isolated from patients can modulate the regulatory molecules on peripheral blood lymphocytes. Our results showed that IL-10 and TGF-β1 have significantly higher mRNA expressions in ASCs isolated from breast cancer patients than those from normal individuals (P value <0.05). The culture supernatant of ASCs isolated from breast cancer patients with pathological stage III induced upregulation of the mRNA expression levels of IL-4, TGF-β1, IL-10, CCR4 and CD25 in PBLs. In addition, the percentage of CD4+CD25highFoxp3+ T regulatory cells was increased in vitro. When the same culture supernatant was added to ASCs isolated from normal subjects augmentation of the mRNA expressions of IL-4, IL-10, IL-8, MMP2, VEGF and SDF-1 in normal ASCs was also observed. These data collectively conclude that resident ASCs in breast cancer tissue may have crucial roles in breast tumor growth and progression by inducing regulatory molecules and promoting anti-inflammatory reaction within the tumor microenvironment. Further investigation is required to see if the immune suppression induced by ASCs is an independent property from tumor cells or ASCs gain their immunosuppressive potential from malignant cells.  相似文献   
69.
Hereditary inclusion body myopathy (HIBM), a neuromuscular disorder, is caused by mutations in UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE), the key enzyme of sialic acid biosynthesis. To date, more than 40 different mutations in the GNE gene have been reported to cause the disease. Ten of them, representing mutations in both functional domains of GNE, were recombinantly expressed in insect cells (Sf9). Each of the mutants that was analyzed displayed a reduction in the two known GNE activities, thus revealing that mutations may also influence the function of the domain not harboring them. The extent of reduction strongly differs among the point mutants, ranging from only 20% reduction found for A631T and A631V to almost 80% reduction of at least one activity in D378Y and N519S mutants and more than 80% reduction of both activities of G576E, underlined by structural changes of N519S and G576E, as observed in CD spectroscopy and gel filtration analysis, respectively. We therefore generated models of the three-dimensional structures of the epimerase and the kinase domains of GNE, based on Escherichia coli UDP-N-acetylglucosamine 2-epimerase and glucokinase, respectively, and determined the localization of the HIBM mutations within these proteins. Whereas in the kinase domain most of the mutations are localized inside the enzyme, mutations in the epimerase domain are mostly located at the protein surface. Otherwise, the different mutations result in different enzymatic activities but not in different disease phenotypes and, therefore, do not suggest a direct role of the enzymatic function of GNE in the disease mechanism.  相似文献   
70.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司    京ICP备09084417号-23

京公网安备 11010802026262号