首页 | 本学科首页   官方微博 | 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   1019篇
  免费   56篇
  2024年   1篇
  2023年   5篇
  2022年   11篇
  2021年   41篇
  2020年   22篇
  2019年   31篇
  2018年   33篇
  2017年   32篇
  2016年   49篇
  2015年   51篇
  2014年   57篇
  2013年   83篇
  2012年   109篇
  2011年   90篇
  2010年   48篇
  2009年   52篇
  2008年   63篇
  2007年   43篇
  2006年   46篇
  2005年   43篇
  2004年   32篇
  2003年   24篇
  2002年   26篇
  2001年   11篇
  2000年   4篇
  1999年   8篇
  1998年   8篇
  1997年   6篇
  1996年   5篇
  1995年   3篇
  1994年   5篇
  1993年   2篇
  1992年   6篇
  1991年   5篇
  1990年   3篇
  1989年   2篇
  1988年   2篇
  1987年   1篇
  1985年   1篇
  1984年   1篇
  1981年   4篇
  1977年   2篇
  1975年   3篇
  1960年   1篇
排序方式: 共有1075条查询结果,搜索用时 62 毫秒
131.
Embryogenic calli were obtained within 3–4 weeks on MS medium supplemented with 3% sucrose, 200 mg I-1 caseinhydrolysate, and 3 mg l?1 each of 2,4-D and NAA from 3–4 days imbibed seeds. Heart-shaped embryos differentiated when growth regulators were withdrawn gradually. Quantification of somatic embryo formation showed a direct relationship between initial response, somatic embryo formation and its subsequent germination. The somatic embryos germinated into emblings with 90% conversion frequency on MS medium containing 2% sucrose.  相似文献   
132.
Protected cultivation of ornamental flowers, as a commercial venture, becomes less profitable with excessive use of fertilizers. The present study examined the influence of microbial biofilm inoculants (AnabaenaAzotobacter, AnabaenaTrichoderma and TrichodermaAzotobacter) on the availability of soil nutrients and structure of rhizosphere microbial communities in three varieties of chrysanthemum (var. White Star, Thai Chen Queen and Zembla). Varietal-specific responses in growth, enzyme activities, flower yield of plants and availability of soil nutrients were recorded. Dehydrogenase activity was highest in var. White Star treated with the AnabaenaTrichoderma biofilm inoculants. The AnabaenaAzotobacter inoculant enhanced the availability of nitrogen, phosphorus and micronutrients in the soil, besides 40–50% increase in soil organic carbon, as compared to carrier alone or no inoculation. PCR-DGGE profiling of the cyanobacterial communities and qPCR quantification of 16S rRNA abundance of bacteria, archaea and cyanobacteria in the rhizosphere soils, revealed the stronger influences of these inoculants, especially in var. Zembla. Principal Component Analysis (PCA) helped to illustrate that the enhanced microbe-mediated availability of soil macro-and micronutrients, except iron content (Fe), was the most influential factor facilitating improved plant growth and yield parameters. The AnabaenaAzotobacter, and Anabaena–Trichoderma biofilm inoculants, proved superior in all three chrysanthemum varieties.  相似文献   
133.
134.
135.
Abstract

Based on worm like chain model, DNA structural parameters—tilt, roll and rise, derived from crystallographic database have been used to determine the flexibility of DNA that regulates the nucleosomal translational positioning. Theoretically derived data has been compared to the experimental values available in Ioshikhes and Trifonov's database. The methodology has been extended to determine the flexibility of 18S rRNA genome in eukarya, where yeast shows a distinct difference when compared with mammals like human, mouse and rabbit.  相似文献   
136.
137.
The lactic acid bacterium Pediococcus acidilactici has recently been reported to help in treating constipation, diarrhea, relieving stress, and enhancing growth rate and immune response in humans, birds, fishes, and small animals. In the present study, we sequenced and analyzed the whole genome of P. acidilactici NRCC1, a novel isolate from rumen fluid of dromedary camel (Camelus dromedarius). The genome of P. acidilactici NRCC1 was assembled into 60 contigs, comprising 1,785,679 bp and 42.5% GC content. The 1705 CDS were predicted and annotated using the RAST server. The genome encodes numerous enzymes for utilization of different carbohydrates. It also harbors genes for antibiotic biosynthesis and many others which might confer probiotic properties. The comparative genome analysis with P. acidilactici DSM 20284 revealed some unique features in P. acidilactici NRCC1. Thus, the genome sequencing of P. acidilactici NRCC1 has opened up new horizons for further research in animal probiotics and feed supplements.  相似文献   
138.
139.
Epithelial abnormality during the transformation of oral submucous fibrosis (OSF) into oral squamous cell carcinoma has been well studied and documented. However, the differential contribution of atrophy and hyperplasia for malignant potentiality of OSF is yet to be resolved. Existing diagnostic conjectures lack precise diagnostic attributes which may be effectively resolved by substantiation of specific molecular pathology signatures. Present study elucidates existence of cellular competitiveness in OSF conditions using computer-assisted neighbourhood analysis in quantitative immunohistochemistry (IHC) framework. The concept of field cancerization was contributory in finding correspondence among neighbouring cells of epithelial layers with reference to differential expression of cardinal cancer-related genes [c-Myc (oncogene), p53 (tumour suppressor), and HIF-1α (hypoxia regulator)] which are known to be important sensors in recognizing cellular competitive interface. Our analyses indicate that different states of OSF condition may be associated with different forms of competitiveness within epithelial neighbouring cells which might be responsible to shape the present and future of the pre-malignant condition. Analytical findings indicated association of atrophic epithelium with stress-driven competitive environment having low c-Myc, high-p53, and stable HIF-1α (the looser cells) which undergo apoptosis. Whereas, the cells with high c-Myc+ (winner cells) give rise to hyperplastic epithelium via possible mutation in p53. The epithelial dysplasia plausibly occurs due to clonal expansion of c-Myc and p53 positive supercompetitor cells. Present study proposes quantitative IHC along with neighbourhood analysis which might help us to dig deeper on to the interaction among epithelial cell population to provide a better understanding of field cancerization and malignant transformation of pre-malignancy.  相似文献   
140.
The recent advancement in new generation fluorinated pyrethroids (e.g., transfluthrin, metofluthrin etc.), the use of semi-volatile vapour phase insecticides for control of mosquitoes and other domestic pests rises. Enabling the examination of the vapour toxicity profiles of these molecules and many other similar new generation molecules will provide new avenues for researchers for understanding the bio-potency in the spatial killing of pests. Hence, it is critical to establish a well-controlled portable vapour-phase bioassay method that can provide the desired precision, accuracy, linearity and robustness. In this respect, we have designed a vapour-toxicity apparatus comprising glass assemblies and developed a novel bioassay method. We found that KT50 and percentage knockdown at 60?min reflect the concentration dependency. This validates and confirms that the method is sensitive enough to distinguish between concentrations and suitable for concentration-response experiments. We found that KT50 and percentage knockdown at 60?min at a given concentration does not differ significantly between experiments. Hence, the method has repeatability and precision. Percentage mortality and total KT50 against Culex quinquefasciatus shows that percentage mortality increases and KT50 decreases linearly with the increasing concentration. This method provides an easy to operate tool to test the vapour toxicity profiles of any vapour phase insecticide molecules against mosquitoes and flying insects.  相似文献   
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