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   399篇
  免费   21篇
  2023年   1篇
  2022年   8篇
  2021年   9篇
  2020年   8篇
  2019年   7篇
  2018年   12篇
  2017年   9篇
  2016年   14篇
  2015年   28篇
  2014年   24篇
  2013年   31篇
  2012年   26篇
  2011年   25篇
  2010年   24篇
  2009年   15篇
  2008年   28篇
  2007年   19篇
  2006年   17篇
  2005年   13篇
  2004年   16篇
  2003年   7篇
  2002年   5篇
  2001年   6篇
  2000年   11篇
  1999年   5篇
  1998年   8篇
  1997年   4篇
  1996年   5篇
  1994年   3篇
  1993年   2篇
  1992年   1篇
  1991年   1篇
  1990年   1篇
  1989年   3篇
  1986年   1篇
  1985年   4篇
  1983年   1篇
  1982年   1篇
  1981年   3篇
  1980年   2篇
  1979年   1篇
  1977年   1篇
  1975年   2篇
  1968年   1篇
  1966年   1篇
  1964年   1篇
  1963年   1篇
  1962年   3篇
  1887年   1篇
排序方式: 共有420条查询结果,搜索用时 15 毫秒
11.
Land‐use changes and the expansion of protected areas (PAs) have amplified the interaction between protected and unprotected areas worldwide. In this context, ‘interface processes' (human–nature and cross‐boundary interactions inside and around PAs) have become central to issues around the conservation of biodiversity and ecosystem services. This scientific literature review aimed to explore current knowledge and research gaps on interface processes regarding terrestrial PAs. At first, 3,515 references related to the topic were extracted through a standardized search on the Web of Science and analyzed with scientometric techniques. Next, a full‐text analysis was conducted on a sample of 240 research papers. A keyword analysis revealed a wide diversity of research topics, from ‘pure' ecology to sociopolitical research. We found a bias in the geographical distribution of research, with half the papers focusing on eight countries. Additionally, we found that the spatial extent of cross‐boundary interactions was rarely assessed, preventing any clear delimitation of PA interactive zones. In the 240 research papers we scanned, we identified 403 processes that were studied. The ecological effects of PAs were well documented and appeared to be positive overall. In contrast, the effects of PAs on local communities were understudied and, according to the literature focusing on these, were very variable according to local contexts. Our findings highlight key research advances on interface processes, especially regarding the ecological outcomes of PAs, the influence of human activities on biodiversity, and PA governance issues. In contrast, main knowledge gaps concern the spatial extent of interactive zones, as well as the interactions between local people and conservation actions and how to promote synergies between them. While the review was limited to terrestrial PAs, its findings allow us to propose research priorities for tackling environmental and socioeconomic challenges in the face of a rapidly changing world.  相似文献   
12.
Environmental Biology of Fishes - Cortisol is recognized as a physiological indicator of stress in fish. However, this hormone is typically measured in plasma samples. In this study, cortisol...  相似文献   
13.
A keratinolytic serine protease secreted by Purpureocillium lilacinum (formerly Paecilomyces lilacinus) upon culture in a basal medium containing 1% (w/v) hair waste as carbon and nitrogen source was purified and characterized. After purification the keratinase was resolved by SDS-PAGE as a homogeneus protein band of molecular mass 37.0 kDa. The extracellular keratinase of P. lilacinum was characterized by its appreciable stability over a broad pH range (from 4.0 to 9.0), and up to 65 °C, along with its strong inhibition by phenylmethylsulphonyl fluoride among the protease inhibitors tested (98.2% of inhibition), thus suggesting its nature as a serine protease. The enzyme was active and stable in the presence of organic solvents such as dimethylsulfoxide, methanol, and isopropanol; certain surfactants such as Triton X-100, sodium dodecylsulfate, and Tween 85; and bleaching agents such as hydrogen peroxide. These biochemical characteristics suggest the potential use of this enzyme in numerous industrial applications.  相似文献   
14.
15.
Hydrobiologia - The study of variation of species composition among sites is key to understanding community ecology, but few studies have assessed beta diversity patterns in highly dynamic stream...  相似文献   
16.
In the context of recent molecular phylogenies of the basal grades of Compositae, we investigated the utility of pollen morphology within the tribe Gochnatieae. The pollen of 64 species of Anastraphia, Cnicothamnus, Cyclolepis, Gochnatia, Pentaphorus, and Richterago was studied using light microscopy and scanning electron microscopy. In addition, three extra-Gochnatieae genera (Ianthopappus, Leucomeris, and Nouelia) were examined as they were traditionally morphologically related to members of the tribe Gochnatieae. Three of the species of Gochnatieae were examined using transmission electron microscopy. Two pollen types, and two new subtypes, have been recognized on the basis of the pollen shape, size, and exine sculpture. The pollen features of Gochnatia sect. Moquiniastrum and G. cordata are similar and distinctive within the genus and support the recently re-circumscribed section Hedraiophyllum. Within the species with echinate pollen surface, the distinctive spine length of Anastraphia supports its recent resurrection as a genus. The identity of Pentaphorus could not be supported by pollen features as was for other morphological characteristics. The pollen features shared across Cyclolepis, Ianthopappus, Leucomeris, Nouelia and Gochnatia sect. Moquiniastrum, as well as those shared by Richterago and Anastraphia could be a result of parallel evolution.  相似文献   
17.
Abstract

Glycyrrhiza glabra L. is considered an important source of bioactive compounds. This study aimed at the development of an efficient solution for the treatment of oral candidiasis. Several extracts of Glycyrrhiza glabra L. were prepared using different solvents and their potential in vitro antifungal activity was assessed. Ethanolic extracts showed the most promising results against C. albicans. This extract was incorporated into mucoadhesive nanoparticles (PLA, PLGA and alginate), which were further included in an oral gel, an oral film and a toothpaste, respectively. The results showed that nanoparticles were successfully produced, presenting a mean size among 100–900?nm with high encapsulation efficiency. In vitro studies showed that the most bioadhesive formulation was the oral film with extract-loaded PLGA nanoparticles, followed by the toothpaste with extract-loaded alginate nanoparticles and the oral gel with extract-loaded PLA nanoparticles.  相似文献   
18.
19.
Suspension-cultured cells of Vitis vinifera cv Monastrell were used to investigate the effects of methyljasmonate, ethylene and salicylic acid separately or in combination with cyclodextrins on both trans-resveratrol production and the induction of defense responses.  相似文献   
20.
Pollen grains of 20 taxa from Gochnatia , Ianthopappus , and Richterago (Compositae - Mutisieae) have been studied. Pollen morphological characters and intergeneric differences are described. Pollen of grains of Richterago and Ianthopappus are relatively larger with thickened exine in the mesocolpia and possess coarse, supratectal spinuliferous processes the height of which is less than their diameter at the base. In Gochnatia , the pollen is medium-sized, the exine is not thickened in the mesocolpia and has minute supratectal spinuliferous processes the height of which is equal or slightly more than 3 w m. Ianthopappus corymbosus is the only species in which the infratectum is thicker than the tectum. With reference to the pollen size and the exine thickness this species appears phylogenetically closer to Richterago than to Gochnatia .  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