全文获取类型
收费全文 | 196篇 |
免费 | 11篇 |
国内免费 | 4篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 6篇 |
2020年 | 12篇 |
2019年 | 18篇 |
2018年 | 6篇 |
2017年 | 7篇 |
2016年 | 8篇 |
2015年 | 4篇 |
2014年 | 11篇 |
2013年 | 15篇 |
2012年 | 2篇 |
2011年 | 5篇 |
2010年 | 4篇 |
2009年 | 7篇 |
2008年 | 7篇 |
2007年 | 11篇 |
2006年 | 8篇 |
2005年 | 7篇 |
2004年 | 10篇 |
2003年 | 6篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 7篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有211条查询结果,搜索用时 32 毫秒
1.
2.
3.
Pollination Ecology of Pedicularis punctata Decne. (Scrophulariaceae) in the Kashmir Himalaya 总被引:2,自引:0,他引:2
Abstract The pollination ecology of Pedicularis punctata was studied in the Pir Panjal Range of the Kashmir Himalaya in the summer of 1989. Its nectarless, rostrate, long-tubed flower was found to be pollinated exclusively by Bombus foragers vibrating pollen while the stigma contacted pollen in the pollinator's cervical crevice. Workers of Bombus tunicatus and B. flavothoracicus comprised 95% of its pollinators. Pollen-foraging fidelity of its pollinators was greatest where diversity of Bombus -pollinated plant species in three plant communities was least. Foragers on other plants carried virtually no Pedicularis pollen. P. punctata is a mid-season blooming species similar in its pollination syndrome to comparable species in other geographic regions. The enigmatic function of its long, nectarless corolla tube, even more exaggerated in other Asiatic species, requires further investigation. 相似文献
4.
Georg Miehe 《Plant Ecology》1988,79(1-2):21-32
The vegetation of Mt Everest is described by means of the dominant plant formations and characteristic features of biotopes. Climatic data givenin connection with weather observations show evidence that the extreme asymmetry of the altitudinal vegetation belt on the south and north slope is induced by heavy rainfall on the south slope and the desiccating effect of the Himalaya föhn in the valleys of the north slope. Biotope shift from hypsozonal distribution on the south slope to extrazonal distribution on the north slope is described, the patterns of the actual timber line are discussed in order to reconstruct the natural upper forest limit, and regressive plant successions during the last 400 years of man's impact are summarized. The dominant vegetation pattern of the alpine belt is compared with that in the European Alps. On the arid north slope alpine steppe communities occur up to 5 500 m. The highest altitudinal vegetation belt and the highest plant communities at 5 960 m are dominated by periglacial processes. The highest records of flowering plants (6 100/6 200 m) and lichens (7 400 m) are discussed in light of the present knowledge on high-altitude vegetation ecology. 相似文献
5.
Dr. P. K. Khosla O. P. Toky R. P. Bisht S. Hamidullah 《Trees - Structure and Function》1995,10(2):108-113
In the mid-western Himalaya (altitude 1350 m, rainfall 1100 mm), multipurpose trees found as escapees in agricultural fields or naturally growing in the forests, play an important role in providing fuel, fooder and small timber to the farmers. Shoot elogation, and tree architecture of 4 year old trees of Grewia optiva, Robinia pseudoacacia and Celtis australis (early successionals), and Quercus leucotrichophora, Q. glauca and Ilex odorata (late successionals), were analyzed. All the late successional species showed a proleptic type of bud and branch production, while the early successional trees made growth through syllepsis. The shoot elongation differed significantly (P <0.05) with the crown position, and ranged from 11 to 30 cm in different species. Early successional species tended to maintain a comparatively narrow crown and showed a significantly (P <0.05) higher ramification ratio, and multilayered canopy. The late successionals, in contrast, showed a wide crown with monolayered canopy, adapted to the weak light intensity. There was only one flush of leaves in Q. leucotrichophora and Q. glauca while in the rest of the species there were two distinct flush periods. The results are important for the management of agroforestry trees. 相似文献
6.
R. K. Gupta 《Plant Ecology》1978,37(2):111-118
Summary Effects of human influences on the vegetation of the Western Himalaya have been reviewed. Impacts of forest management practices, over-grazing, surface mining, defence and development operations, and road building activities, are severe in the region. This has created an alarming situation for soil and water conservation. Increased soil loss and runoff pose a threat to various reservoirs built for various uses and have increased hazards of erosion and floods in the Indus and Ganga basin regions.Nomenclature follows Hooker (1872–1897) and Gupta (1968). 相似文献
7.
AbstractThe present study aims to exploit microbial potential from colder region to produce lipase enzyme stable at low temperatures. A newly isolated bacterium GBPI_508 from Himalayan environment, was investigated for the production of cold-active lipase emphasizing on its aggregation properties. Plate based assays followed by quantitative production of enzyme was estimated under different culture conditions. Further characterization of partially purified enzyme was done for molecular weight determination and activity and stability under varying conditions of pH, temperature, and in presence of organic solvents, inhibitors, and metal ions. The psychrotolerant bacterium was identified as Pseudomonas palleroniana following 16S rRNA gene sequencing. Maximum lipase production by GBPI_508 was recorded in 7?days at 25?°C utilizing yeast extract as nitrogen source and olive oil as substrate in the lipase production medium. Triton X-100 (1%) in the medium as emulsifier significantly enhanced the lipase production. Lipase produced by bacterium showed aggregation which was confirmed by dynamic light scattering and native PAGE. SDS-PAGE followed by zymogram analysis of partially purified enzyme showed two active bands of ~50?kDa and ~54?kDa. Optimum activity of partially purified enzymatic preparation was recorded at 40?°C while the activity remained nearly consistent from pH 7.0 to 12.0, whereas, maximum stability was recorded at pH values 7.0 and 11.0 at 25?°C. Interestingly, lipase in the partially purified fraction retained 60% enzyme activity at 10?°C. Medium chain pNP ester (C10) was the most preferred substrate for the lipase of GBPI_508. The lipase possessed >50% residual activity when incubated with different organic solvents (25% v/v) except toluene and dichloromethane which inhibited the activity below 50%. Partially purified enzyme was also stable in the presence of metal ions and inhibitors. The study suggests applicability of GBPI_508 lipase in low temperature conditions such as cold-active detergent formulations and cold bioremediation. 相似文献
8.
DNA barcodes in species tagging have become a popular tool for taking inventories of species from different groups worldwide. The present study aimed to generate DNA barcodes of butterfly species from the Western Himalayas in Uttarakhand, India. The Indian Western Himalayan region (IWHR) has been explored to a limited extent about butterfly species’ diversity. However, the IWHR is prone to environmental change, and slight variations in climatic conditions can influence species diversity and change butterflies' range. The mitochondrial cytochrome c oxidase I (COI) gene was first used to generate the DNA barcode for butterflies from this region on a broad scale. 28 morphologically identified species, consisting of 102 sequences, were finally grouped into 26 species, with only two species showing ambiguity in species identification. These species had < 3% sequence variations from their neighboring relatives, suggesting cryptic species diversity. Generated sequences were also compared with the GenBank data of conspecific geographical locations, which showed intraspecies variation ranging from 1.3% to 7.3%. It was also noted that butterfly species have both intra and interspecies sequence divergence. In the phylogenetic-based species identification, a total of 28 species belonging to 4 families of butterflies were successfully discriminated, and two species at the genus level, which had high intra-specific divergence (0.025), were considered. However, the high intra-species sequence divergence observed may represent the presence of hidden species. 相似文献
9.
Robert Bagchi Mike Crosby Brian Huntley David G. Hole Stuart H. M. Butchart Yvonne Collingham Mohit Kalra Jagadish Rajkumar Asad Rahmani Mitra Pandey Hum Gurung Le Trong Trai Nguyen Van Quang Stephen G. Willis 《Global Change Biology》2013,19(4):1236-1248
We forecasted potential impacts of climate change on the ability of a network of key sites for bird conservation (Important Bird Areas; IBAs) to provide suitable climate for 370 bird species of current conservation concern in two Asian biodiversity hotspots: the Eastern Himalaya and Lower Mekong. Comparable studies have largely not accounted for uncertainty, which may lead to inappropriate conclusions. We quantified the contribution of four sources of variation (choice of general circulation models, emission scenarios and species distribution modelling methods and variation in species distribution data) to uncertainty in forecasts and tested if our projections were robust to these uncertainties. Declines in the availability of suitable climate within the IBA network by 2100 were forecast as ‘extremely likely’ for 45% of species, whereas increases were projected for only 2%. Thus, we predict almost 24 times as many ‘losers’ as ‘winners’. However, for no species was suitable climate ‘extremely likely’ to be completely lost from the network. Considerable turnover (median = 43%, 95% CI = 35–69%) in species compositions of most IBAs were projected by 2100. Climatic conditions in 47% of IBAs were projected as ‘extremely likely’ to become suitable for fewer priority species. However, no IBA was forecast to become suitable for more species. Variation among General Circulation Models and Species Distribution Models contributed most to uncertainty among forecasts. This uncertainty precluded firm conclusions for 53% of species and IBAs because 95% confidence intervals included projections of no change. Considering this uncertainty, however, allows robust recommendations concerning the remaining species and IBAs. Overall, while the IBA network will continue to sustain bird conservation, climate change will modify which species each site will be suitable for. Thus, adaptive management of the network, including modified site conservation strategies and facilitating species' movement among sites, is critical to ensure effective future conservation. 相似文献
10.