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   395篇
  免费   41篇
  国内免费   117篇
  2024年   2篇
  2023年   7篇
  2022年   7篇
  2021年   14篇
  2020年   17篇
  2019年   15篇
  2018年   13篇
  2017年   17篇
  2016年   7篇
  2015年   19篇
  2014年   28篇
  2013年   37篇
  2012年   40篇
  2011年   40篇
  2010年   33篇
  2009年   31篇
  2008年   23篇
  2007年   37篇
  2006年   26篇
  2005年   21篇
  2004年   25篇
  2003年   12篇
  2002年   10篇
  2001年   8篇
  2000年   8篇
  1999年   8篇
  1998年   5篇
  1997年   7篇
  1996年   2篇
  1995年   3篇
  1994年   2篇
  1993年   4篇
  1992年   12篇
  1991年   1篇
  1990年   1篇
  1989年   2篇
  1988年   1篇
  1987年   1篇
  1986年   1篇
  1985年   2篇
  1983年   1篇
  1981年   2篇
  1957年   1篇
排序方式: 共有553条查询结果,搜索用时 15 毫秒
1.
2.
Oceanic islands are productive habitats for generating new species and high endemism, which is primarily due to their geographical isolation, smaller population sizes and local adaptation. However, the short divergence times and subtle morphological or ecological divergence of insular organisms may obscure species identity, so the cryptic endemism on islands may be underestimated. The endangered weevil Pachyrhynchus sonani Kôno (Coleoptera: Curculionidae: Entiminae: Pachyrhynchini) is endemic to Green Island and Orchid Island of the Taiwan‐Luzon Archipelago and displays widespread variation in coloration and host range, thus raising questions regarding its species boundaries and degree of cryptic diversity. We tested the species boundaries of P. sonani using an integrated approach that combined morphological (body size and shape, genital shape, coloration and cuticular scale), genetic (four genes and restriction site‐associated DNA sequencing, RAD‐seq) and ecological (host range and distribution) diversity. The results indicated that all the morphological datasets for male P. sonani, except for the colour spectrum, reveal overlapping but statistically significant differences between islands. In contrast, the morphology of the female P. sonani showed minimum divergence between island populations. The populations of P. sonani on the two islands were significantly different in their host ranges, and the genetic clustering and phylogenies of P. sonani established two valid evolutionary species. Integrated species delimitation combining morphological, molecular and ecological characters supported two distinct species of P. sonani from Green Island and Orchid Island. The Green Island population was described as P. jitanasaius sp.n. Chen & Lin, and it is recommended that its threatened conservation status be recognized. Our findings suggest that the inter‐island speciation of endemic organisms inhabiting both islands may be more common than previously thought, and they highlight the possibility that the cryptic diversity of small oceanic islands may still be largely underestimated.  相似文献   
3.
王根法  邱云 《动物学报》1989,35(3):313-317
应用氧电极技术测定了正常钉螺和受药物作用钉螺的耗氧量。结果表明不同地区、不同温度环境、不同性别、野外收集、人工饲养及感染毛蚴的钉螺的耗氧都不同;已知九种有效杀螺药都有抑制钉螺耗氧的作用而十三种无杀螺效果的化合物则不影响钉螺的耗氧;氯化镉有抑制钉螺呼吸的作用,亦呈现杀死钉螺的作用。  相似文献   
4.
Complete mRNA sequence of transferrin from Galleria mellonella was obtained, and compared with those of other species. Until now, two types of insect transferrin were reported. Transferrins in cockroach and termite have two iron binding sites while those in most other insect groups, studied for the protein, have only one. It was suggested that the presence of two types of transferrin was related with transferrin evolution, because vertebrate transferrins have two iron binding sites, called N and C terminal lobe. It was shown that G. mellonella transferrin also has only one iron binding site (N terminal lobe), and the deduced amino acid sequence was most similar to those of Manduca sexta and Bombyx mori.  相似文献   
5.
This study was performed to explore novel and valuable uses of insect resources, important subjects of the natural compound used in bio‐industries. The whole bodies of two crickets, Gryllus bimaculatus and Teleogryllus emma, selected from medicinal insect species, were carefully ground and treated with 80% EtOH. The insect extracts were solubilized and separated by hexane, butanol, and D.W according to their polarities. Three types of extracts, a D.W fraction (G1) and a boiling extract (G2) of an introduced cricket, G. bimaculatus, and a D.W fraction (T1) of a Korean local cricket, T. emma, were prepared to assay immune stimulating activity of cricket originated compounds. The all of three treated cricket extracts showed to increase IL‐4, IFN‐, and TNF‐α. Among those extract, extract G2, boiled extract from G. bimaculatus, was the best immune–enhancing fraction. The results of this study could be fundamental information for further works to use insects as natural resources having plenty of potentials and varieties.  相似文献   
6.
耐药菌,尤其是多重耐药菌的出现和持续进化给人类健康带来了巨大的威胁。在抗生素逐渐失去特效作用的情况下,科学界和医药界又把眼光重新投向了抗菌的天然生物-噬菌体,并在一些研究中证明了噬菌体可以作为新的武器去替代抗生素治疗耐药菌感染。通过对噬菌体治疗及衍生的裂解酶治疗的世界专利申请进行统计及分析,获得了专利发展趋势、申请人分布特点及主要专利申请人等信息,详细分析了噬菌体及裂解酶治疗的主要专利技术路线和研发热点。  相似文献   
7.
为了开发高效的食用菌绿色保鲜剂,以新鲜的白色金针菇为供试材料,以花椒精油和丁香精油为供试熏蒸剂,分别在常温(25±1)℃和低温(4±1)℃条件下开展了适用于金针菇保鲜的精油种类和浓度的筛选试验,并对金针菇贮藏期内的感官评价、失重率、呼吸强度、褐变度、多酚氧化酶(PPO)活性、苯丙氨酸解氨酶(PAL)活性、丙二醛(MDA)以及总酚含量进行了测定。结果显示,常温(25±1)℃条件下用0.1 mL·kg-1花椒精油和0.5 mL·kg-1丁香精油保鲜效果优于其他处理,且有统计学意义(P<0.05),0.1 mL·kg-1花椒精油和0.5 mL·kg-1丁香精油处理组感官评分分别高于对照组23.4%和27.8%,二者均能够抑制金针菇褐变、减轻腐败变质,且有统计学意义(P<0.05);在低温(4±1)℃贮藏试验中发现,0.1 mL·kg-1花椒精油和0.5 mL·kg-1丁香精油均能有效抑制呼吸强度和PPO活性的升高(P<0.05),其呼吸高峰较对照组分别降低了28.3%和39.6%;贮藏15 d后,精油处理组PPO活性较对照组分别降低了8.2%和16.6%;精油处理有效降低了MDA含量的产生,保持着较高的总酚含量、减轻腐烂褐变的程度。第15天时,对照组MDA含量为1.75 μmol·g-1,而花椒精油和丁香精油处理组MDA含量分别比对照组低0.15、0.40 μmol·g-1,丁香精油处理组显著低于花椒精油处理组和对照组(P<0.05)。研究结果表明,0.1 mL·kg-1花椒精油和0.5 mL·kg-1丁香精油均对金针菇采后贮藏保鲜效果显著,其中,0.5 mL·kg-1丁香精油的保鲜效果最明显,在15d的贮藏期内,金针菇依然保持着良好的品质,而对照组已经轻微褐变,部分开始腐烂。研究结果为花椒精油和丁香精油应用于金针菇采后贮藏保鲜提供了理论依据。  相似文献   
8.
The soil bacterial communities have been widely investigated. However, there has been little study of the bacteria in Qinghai-Tibet Plateau, especially about the culturable bacteria in highland barley cultivation soil. Here, a total of 830 individual strains were obtained at 4°C and 25°C from a highland barley cultivation soil in Qamdo, Tibet Autonomous Region, using fifteen kinds of media. Seventy-seven species were obtained, which belonged to 42 genera and four phyla; the predominant phylum was Actinobacteria (68.82%), followed by Proteobacteria (15.59%), Firmicutes (14.29%), and Bacteroidetes (1.30%). The predominant genus was Streptomyces (22.08%, 17 species), followed by Bacillus (6.49%, five species), Micromonospora (5.19%, four species), Microbacterium (5.19%, four species), and Kribbella (3.90%, three species). The most diverse isolates belonged to a high G+C Gram-positive group; in particular, the Streptomyces genus is a dominant genus in the high G+C Gram-positive group. There were 62 species and 33 genera bacteria isolated at 25°C (80.52%), 23 species, and 18 genera bacteria isolated at 4°C (29.87%). Meanwhile, only eight species and six genera bacteria could be isolated at 25°C and 4°C. Of the 77 species, six isolates related to six genera might be novel taxa. The results showed abundant bacterial species diversity in the soil sample from the Qamdo, Tibet Autonomous Region.  相似文献   
9.
10.
Endothelial lipase (EL) activity has been implicated in HDL metabolism and in atherosclerotic plaque development; inhibitors are proposed to be efficacious in the treatment of dyslipidemia related cardiovascular disease. We describe here the discovery of a novel class of anthranilic acids EL inhibitors. XEN445 (compound 13) was identified as a potent and selective EL inhibitor, that showed good ADME and PK properties, and demonstrated in vivo efficacy in raising plasma HDLc concentrations in mice.  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