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991.
Plant diversity of secondary forests in response to anthropogenic disturbance levels in montane regions of northeastern China 总被引:4,自引:0,他引:4
The effects of anthropogenic disturbances on forest structure and plant diversity of secondary forest ecosystems were evaluated
based on the classification by site factors in the montane regions of northeastern China. Forty-five sample plots containing
720 sub-plots of overstory species (8 m × 8 m), 1,440 quadrats of understory species (2 m × 2 m), and 1,440 quadrats of herbaceous
layer species (1 m × 1 m) were clustered into five groups (G1, G2, G3, G4 and G5) by site variables with Hierarchical Cluster
Analysis. Meanwhile, the disturbance levels corresponding to the five groups were determined according to the factors influencing
human disturbances (D0-G2, D1-G1, D2-G3, D3-G5, and D4-G4). Species diversities of overstory, understory, herbaceous layer
and overall species were evaluated using species number, Margalef index, Pielou index, Shannon–Wiener index, and Simpson index;
and β-diversities (Whittaker index, Cody index). Basal area of stands exhibited a decreasing trend along the disturbance level
due to a gradual increase in the extraction of timber by the human disturbances. The indices of species diversity suggested
that overstory and understory species were distributed evenly among the groups or disturbance levels. There were no absolutely
dominant tree species in the secondary forest ecosystems. The differences in site factors and the current disturbance intensities
were not intense enough to lead to loose changes in overstory and understory species. The species diversity indices exhibited
the maximum values at D3 (G5) for herbaceous layer species; this may suggest that the current disturbance intensities were
intense enough to lead the changes of herbaceous layer species. Three rare and endangered species (Juglans mandshurica, Fraxinus mandshurica and Acanthopanax senticosus) were found within the secondary forests. These rare and endangered species appeared in each clustered group or disturbance
level, which suggested that the current disturbance intensity in the study area was not strong enough to influence the distribution
of rare and endangered species. The current disturbances in the secondary forests may not lead to a decrease in stability
and complexity of the overstory and understory species, but the higher disturbance level may be intense enough to change the
habitat fitness for the herbaceous species.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized authors. 相似文献
992.
A study was conducted to determine the dynamic of Zn content between soil and plant in the natural protection zone of Leymus chinensis grassland in Changling County (44°30′–44°45′N; 123°31′–124°10′E), Jilin Province, China. Results showed that the total Zn
content was lower, available Zn content had a moderate level in the soil, and the plants was not lack of Zn. During the growing
season, content of total Zn and available Zn in soil showed a down-trend distribution along the soil profile. Content of total
Zn had a significantly positive correlation with that of the organic matter, but it was negatively correlated to soil pH.
Monthly dynamic of the average content of total Zn showed a “V” type curve in the growing season from May to August, and July
was the nadir. The trend of the average content of available Zn was similar to the content of total Zn, but was down after
August; Zn content variation in the organs and litter of L. chinensis was great, with the order of root>rhizome >leaf>stem>litter. The ratio of available Zn content in A layer versus B layer
was more than 2 times that of the total Zn, which indicated that the soil of A layer had higher enrichment capacity of available
Zn. The enrichment of Zn in the root of L. chinensis was 44.17 times as that in the soil. The absorbing intensity of root had a significantly negative correlation with the activity
of Zn in the soil (r=−0.8800, p<0.01).
Biography: ZHOU Xiao-mei (1966–), female, Ph.D., associate professor of Jilin Normal University, Siping 136000, P.R. China. 相似文献
993.
Effect of temperature and compression on the mechanical behavior of steam-treated wood 总被引:2,自引:0,他引:2
The mechanical behavior of steamed spruce wood changes dramatically with compression along the grain, the change being much more moderate perpendicular to the grain. The stiffness decrement due to increased temperature is greatest in the tangential material direction. The stiffness decrement due to compression is greatest along the grain. Compression to 80% compressive strain at 131°C inverts the order of the material directions regarding stiffness, the stiffness being the least along the grain. Plastic strain due to compression is greater at higher temperatures. The compression-induced decrement of stiffness along the grain is greater at higher temperatures, but the off-axis decrement of stiffness is less at higher temperatures. 相似文献
994.
Participatory mapping and GIS are both necessary to model the interactions between humans and their environment. A case study
from the forest margin in the Congo Basin demonstrates how data from participatory community mapping and other social science
methods can be prepared for quantitative modelling. This approach bridged the gap between spatial modelling data and social
decision-making in space by elaborating a geographically consistent social representation of the landscape and giving a geographical
base to the connection between land use, its cultural representation, and its social management. This was achieved through
an iterative process of GIS cartography, using feedback from village informants and field checking, to transpose the spatial
references from participatory mapping sketches into reliable geographic locations. As well as demonstrating the utility of
such data for modelling, this work clarified the distribution of land rights among the six main owner-clans spread through
the eight hamlets in the watershed. The ‘basin’ of spatial resources and its relation to the rules of land use and natural
resource management were defined for each clan. Land-use systems at the forest-agriculture interface in the study area proved
to be complex, strongly driven by social rules and influenced by history and settlement strategies. These social and historical
aspects established the framework within which communities make current decisions and interventions.
The authors thank the people of Akok for their collaboration and hospitality. Village technician Michel Engueng and village
contact Adolphe Ze facilitated and assisted this work. Our thanks also to Julie Mbazo’o and Remy Assoumou, both members of
the ‘social side’ working group of the FLORES modelling team. Christopher Legg’s contribution to the discussion of this work
through his constant reviewing of the CamFlores model is gratefully recognized. Finally, thanks to the whole CIFOR-ACM team
for numerous scientific and methodological inputs. The Italian Foreign Ministry funded the work of Valentina Robiglio (APO-GIS
specialist) through an APO contract with IITA. The European Union (Tropical Forestry budget line DG VIII) contributed to the
CIFOR’s research program on the ‘Adaptive Collaborative Management of Forests’ (ACM) in Africa, and to the Alternative to
Slash and Burn (ASB) program in Cameroon on ‘Environmental Services and Rural Livelihoods’ through the World Agroforestry
Centre. 相似文献
995.
Tree planting for poverty reduction in less-favoured areas of the Ethiopian highlands 总被引:1,自引:0,他引:1
This paper assesses the potential impact of planting of eucalypt trees as a strategy to reduce poverty in a less-favoured
area of the highlands of Ethiopia. Results from simulations with a bio-economic model for a less-favoured case study area
in the highlands are combined with survey data at community, household and plot level to assess how general the results of
the bio-economic model are. Application of the bio-economic model shows clearly that land degradation, population growth,
stagnant technology and drought threaten food security. Household welfare and land quality are deteriorating rapidly in the
area and interventions are urgently needed to avoid human disaster. Planting of eucalypts on land unsuitable for crop production
may substantially increase household incomes if market outlets for trees can be found. Tree planting will not have severe
negative effects on food production or land conservation. A policy combining promotion of tree planting and conservation of
cropland may achieve win-win benefits in terms of increased household incomes as well as more sustainable land-use. Analysis
of survey data from the Amhara Region of Ethiopia reveals that there is a large area of land that is unsuitable for crop production
located close to all-weather roads in the less-favoured areas of the region. Few trees have been planted on this type of land
up to now. The past policy seems to have discouraged tree planting except on homestead plots that are more suitable for food
crops.
This paper reports part of the IFPRI/ILRI project ‘Policies for Sustainable Land Management in the East African Highlands’.
These two agencies have provided funds and logistical support for the work. The Norwegian Ministry of Foreign Affairs has
provided funds for this research in the Amhara Region in Ethiopia. The authors also draw on earlier work funded by Research
Council of Norway. Any correspondence should be directed to the first author. 相似文献
996.
BYUNBong-Kyu YANShan-chun LICheng-de 《林业研究》2003,14(3):210-212
Genus Eurydoxa Filipjev in China is reviewed and noted for the first time. Based on the present study, two species are recognized, including rhodopa Diakonoff and advena Filipjev. All available information for the species is reviewed and provided. 相似文献
997.
1-Hydroxyethyl-2-alkyl-2-imidazoline (HEAI) and its derivative sulfonate amphoteric surfactant were synthesized using tall oil fatty acid as the raw material. Suitable experimental conditions for synthesizing the intermediate and final products were probed. Their chemical structures were also investigated by means of infrared spectroscopy and hydrogen nuclear magnetic resonance spectroscopy. Based on the results of these analyses, it has been found that during the reaction process of HEAI with sodium 3-chloro-2-hydroxypropane sulfonate under alkaline condition the imidazoline ring was hydrolyzed to amides, and the obtained amphoteric surfactant was actually a complex mixture of amides. An etherification reaction in the hydroxyethyl group was also observed when the HEAI/sodium 3-chloro-2-hydroxypropane sulfonate molar ratio was more than 1:1. 相似文献
998.
SUHan-ying LINDai-bin 《林业研究》2003,14(1):83-86
The investigation was carried out on 10-year-old plantation of Fraxinus mandshurica in Mao‘er Mountain Experimental Station of Northeast Forest University.tree height(H),diameter at breast height(D1.3) and the increment of tree height in 5 years (H5),the thickness of humus layer,as well as the soil moisture were measured for the plantation and the growth indexes(H,D1.3,H5) for different site conditions were analyzed.The results showedthat main site factors influencing the growth of Fraxinus mandshurica were soil moisture,gradient and location of siope in order.The growth of Fraxinus mandshurica was better on the middle-or up-slope site than on the down-slope site.Soil moisture and late frost caused by terrain are the main reasons that limit the growth of Fraxinus mandshurica plantation. 相似文献
999.
Kenaf (Hibiscus cannabinus) plants are widely known for their contribution to the global and regional environment because of their ability to fix CO2. On the other hand, some scientists have doubts about CO2 fixation by kenaf and have misgivings about the effect of kenaf on the ecosystem. We have characterized the structural characteristics
of cell walls of bast fibers, cores, roots, and leaves of kenaf during the maturation of plants and investigated the rate
of photosynthesis. During maturation of the kenaf plant the cellulose (bast fiber 52–59%, core 44–46%) and lignin (bast fiber
9.3–13.2%, core 18.3–23.2%) contents increased significantly. The aromatic composition of the lignin of bast fiber was significantly
different from that of the core lignin and of other plants. The lignin of bast fiber appears similar to pure syringyl lignin.
Fixation of CO2 by kenaf plants and their contribution to the global environment are discussed. A significatly high rate of photosynthesis
of kenaf plants was observed compared to that of woody plants in Japan, but the amount of CO2 fixation depends on the characteristics of the plantation. If the kenaf was planted in high density, about twice as much
CO2 was fixed as was fixed by trees in a tropical rain forest.
Received: April 22, 2002 / Accepted: July 24, 2002
Acknowledgments This project was supported by the Science and Technology Agency (STA) fellowship of the Japan International Science and Technology
Exchange Center (JISTEC), which has been successfully applied by Dr. Shuji Hosoya, Forestry and Forest Products Research Institute.
We thank Dr. Toshio Sumizono and Mr. Masao Sakurai, Forestry and Forest Products Research Institute, for their kind help in
determining the rate of photosynthesis and cultivating the kenaf plants, respectively. We also express our appreciation to
Dr. Quang Hung Le, College of Agriculture and Forestry, Ho Chi Minh City, Vietnam for offering information about the cultivation
of kenaf at Thu Duc District, Ho Chi Minh City. 相似文献
1000.
神农架地区珍衡植物沿河岸带的分布格局 总被引:2,自引:0,他引:2
Due to the importance of riparian zone in maintaining and protecting regional biodiversity, increasingly more ecologists paid
their attentions to riparian zone and had been aware of the important effects of riparian zone in basic study and practical
management. In this study, 42 sampling belts (10 m×100m) parallel to the bank of Xiangxi River at different elevations in
Shennongjia Area were selected to investigate the riparian vegetation and rare plants. 14 species of rare plants were found
distributing in riparian zone, accounting for 42.4% of the total rare plant species in Shennongjia Area. The main distribution
range of the 14 rare plant species was the evergreen and deciduous mixed broadleaved forest at elevation of 1200–1800 m, where,
species diversity of plant community was the maximum at the moderate elevation. The analysis of TWINSPAN divided the 14 rare
species into 3 groups against the elevation, namely low elevation species group, moderate elevation species group, and high
elevation species group. The analysis of DCA ordination showed similar results to that of TWINSPAN. In the paper, the authors
discussed the reasons forming the distribution pattern of rare plant species, and pointed out that the important function
of riparian zone on rare plant species protection.
Foundation item: This project was supported by National Natural Science Foundation of China (NSFC39970123), and Changbai Mountain Open Research
Station, Chinese Acadamy of Science.
Biography: JIANG Ming-xi (1965-), male, associate professor in Wuhan Institute of Botany, Chinese Academy of Sciences, Wuhan 430074,
P. R. China
Responsible editor: Chai Ruihai 相似文献