全文获取类型
收费全文 | 20589篇 |
免费 | 233篇 |
国内免费 | 2篇 |
专业分类
林业 | 3789篇 |
农学 | 1478篇 |
基础科学 | 149篇 |
3511篇 | |
综合类 | 1060篇 |
农作物 | 2615篇 |
水产渔业 | 2139篇 |
畜牧兽医 | 2823篇 |
园艺 | 1172篇 |
植物保护 | 2088篇 |
出版年
2023年 | 29篇 |
2022年 | 88篇 |
2021年 | 163篇 |
2020年 | 97篇 |
2019年 | 121篇 |
2018年 | 2832篇 |
2017年 | 2773篇 |
2016年 | 1293篇 |
2015年 | 212篇 |
2014年 | 219篇 |
2013年 | 274篇 |
2012年 | 1093篇 |
2011年 | 2447篇 |
2010年 | 2275篇 |
2009年 | 1438篇 |
2008年 | 1571篇 |
2007年 | 1839篇 |
2006年 | 291篇 |
2005年 | 312篇 |
2004年 | 314篇 |
2003年 | 336篇 |
2002年 | 198篇 |
2001年 | 135篇 |
2000年 | 132篇 |
1999年 | 57篇 |
1998年 | 28篇 |
1997年 | 17篇 |
1996年 | 9篇 |
1995年 | 10篇 |
1993年 | 20篇 |
1992年 | 23篇 |
1991年 | 14篇 |
1990年 | 23篇 |
1989年 | 22篇 |
1988年 | 18篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1980年 | 5篇 |
1978年 | 11篇 |
1977年 | 6篇 |
1974年 | 5篇 |
1972年 | 6篇 |
1971年 | 3篇 |
1970年 | 3篇 |
1969年 | 4篇 |
1968年 | 8篇 |
1967年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Mark K. Asplen Gianfranco Anfora Antonio Biondi Deuk-Soo Choi Dong Chu Kent M. Daane Patricia Gibert Andrew P. Gutierrez Kim A. Hoelmer William D. Hutchison Rufus Isaacs Zhi-Lin Jiang Zsolt Kárpáti Masahito T. Kimura Marta Pascual Christopher R. Philips Christophe Plantamp Luigi Ponti Gábor Vétek Heidrun Vogt Vaughn M. Walton Yi Yu Lucia Zappalà Nicolas Desneux 《Journal of pest science》2015,88(3):469-494
52.
Akram Taghizadeh Saroukolai Saeid Moharramipour Mohammad Hadi Meshkatalsadat 《Journal of pest science》2010,83(1):3-8
Red flour beetle Tribolium castaneum (Herbst) and rice weevil Sitophilus oryzae (L.) are considered to be the major insect pests in storage. Essential oils from aromatic plants are recognized as proper
alternatives to fumigants. Thymus persicus (Ronniger ex Rech. f.) is one of these plants that have medicinal properties and is indigenous to Iran. The essential oil
was obtained from aerial parts of the plant and analyzed by GC and GC–MS. Carvacrol (44.69%) and thymol (11.05%) were the
major constituents of the oil extracted. In this experiment, fumigant toxicity of the essential oil was studied against T. castaneum, S. oryzae at 27 ± 1°C and 60 ± 5% RH in dark condition. The adult insects were exposed to the concentrations of 51.9, 111.1, 207.4
and 370.4 μl/l air to estimate median lethal time (LT50) values. The fumigant toxicity was increased in response to increased essential oil concentrations. The LT50 values at the lowest and the highest concentrations tested were ranged from 28.09 to 13.47 h for T. castaneum, and 3.86 to 2.30 h for S. oryzae. It was found that S. oryzae adults were much more susceptible to the oil than T. castaneum. After 24 h of exposure, the LC50 values (95% fiducial limit) for T. castaneum and S. oryzae were estimated to be 236.9 (186.27–292.81) and 3.34 (2.62–4.28) μl/l air, respectively. These results suggest that T. persicus essential oil merits further study as potential fumigant for the management of these stored-product insects. 相似文献
53.
54.
Purpose
The variation in soil microbial community patterns is primarily influenced by ecological processes associated with spatial distance and environmental heterogeneities. However, the relative importance of these processes in determining the patterns of soil microbial biodiversity in different successional forests remains unclear.Materials and methods
Based on the species data from denaturing gradient gel electrophoresis (DGGE) analysis, we described the composition and beta diversity of ammonia-oxidizing archaea (AOA) community, an important functional microbial group in regulating nitrogen cycle, in a middle-succeed stand (60 years of secondary succession) and an undisturbed native stand in a subtropical forest in southern China. The composition pattern was examined using a multi-response permutation procedure (MRPP), and the beta diversity was described using the Sørensen index. The relative influence of edaphic, vegetational, spatial, and topographical factors on AOA composition and beta diversity was assessed by variation partitioning and multiple regression on distance matrices (MRM), respectively.Results and discussion
We did not find any stand-specific patterns in AOA community composition in the two stands; however, the influential variables were different between the two stands; 7.3 and 4.5 % of the total variation in AOA community composition could be explained by edaphic (i.e., available potassium and total phosphorus) and spatial variables, respectively, in the middle-succeed stand, while 3.7 and 2.8 % of the variation were explained by spatial variable and available phosphorus, respectively, in the native stand. Soil total phosphorus influenced the beta diversity of AOA community most in the middle-succeed stand, while genetic distance of tree species was found to be the most important factor in driving the beta diversity pattern in the native stand.Conclusions
Soil nutrients influenced the beta diversity of AOA community in the middle-succeed stand more than that in the native stand, while vegetation is more important in the native stand. The substantial unexplained variations were possibly due to the effects of other unmeasured variables. Nevertheless, dispersal process is more important in controlling AOA community composition in the native stand, while processes associated with environmental heterogeneities are more important in the middle-succeed stand in this subtropical forest.55.
56.
Manjeet B. L. Pander R. Sharma S. S. Dhaka Ankit Magotra Kapil Dev 《Tropical animal health and production》2017,49(8):1689-1695
Foot and mouth disease (FMD) is the most contagious disease of mammals and a major threat to animal husbandry sector. In India, vaccination with the inactivated trivalent (O, A and Asia1) vaccine is one proven way for protecting the livestock from FMD. However, many outbreaks have been reported in different parts of the country. Therefore, present study was aimed at elucidating the effects of genetic and non-genetic factors on FMD viral vaccine-elicited immune response in Hardhenu cattle. The effect of season of vaccination was not consistent. The effect of status of animal was significant for all the pre and post AB titres except for pre AB titre of serotype O and post AB titre of Asia1.The estimates of heritability for response to vaccination were low to high ranging from 0.11 to 0.45. The highest heritability estimate was obtained for serotype O and the lowest for Asia1. The heritability estimates for pre and post AB titres ranged from 0.15 to 0.33. All the pre and post AB titres and responses to vaccination had genetic correlations ranged from high negative to high positive among them. Results of this study highlight the variation in vaccine response which needs to be further exploited on large-scale animal data for better immunization and protection against highly contagious viral vesicular disease of cloven-hoofed animals. 相似文献
57.
Faidherbia albida is an ideal agroforestry tree commonly intercropped with annual crops like millet and groundnuts in the dry and densely populated areas of Africa. With its peculiar reverse phenology, it makes growth demands at a different time from that of crops. In addition, it deposits great amount of organic fertilizer on food crops. Leaves entering soils are comparable to fertilization of almost 50 t·ha 1 ·year 1 of manure in dense stands of 50 large trees per ha. These nutrients help maximize agricultural production and reduce the need for a fallow period on poorer soils. Research has shown that millet grown under F. albida yielded 2.5 and 3.4 fold increases in grain and protein, respectively. Animals eat pods which contain mean amounts of crude protein of 20.63% and carbohydrate of 40.1% in seeds. Moreover, the continued existence of F. albida in agroforestry parklands as in Ethiopia and Mali signifies the success of traditional conservation measures. Modern scientists have also developed much interest in the role of agroforestry in maintaining long-term biological balance between agriculture and livestock production systems. To ensure food security, which still remains a major challenge in sub-Saharan Africa, and concurrently minimize environmental degradation, promotion of agroforestry that specifically involves indigenous trees is crucial. We discuss the prospective role of F. albida in alleviating poverty while simultaneously protecting the environment from factors associated with, for example, deforestation and loss of biodiversity. The overall aim is to promote wide-scale adoption of F. albida as a valuable tree crop in farming systems, particularly in those areas where it remains unexploited. 相似文献
58.
Eucalypt (Eucalyptus spp.) tree farming is a source of income for many smallholders in developing and emerging countries and critical to the resource
supply of many pulp and paper companies. These companies rely on smallholders adopting tree farming, sometimes by offering
a contract. This paper reports a study from four regions of Thailand, where smallholder eucalypt tree farming is important,
which investigated what characteristics of smallholders were associated with greater adoption of tree farming. A total of
461 eucalypt tree farmers and 171 non-tree farmers were randomly selected and surveyed in these regions, using a door-to-door
household survey. A logit analysis corroborated hypotheses about the drivers of adoption. Qualitative analyses were used to
inform interpretation of the quantitative results and shed light on the role of eucalypt tree farming in smallholders’ livelihood.
Results demonstrate that those with suitable land available are more likely to adopt eucalypt tree farming than others. In
addition, perception of land tenure security matters in the adoption of tree growing, but holding a formal land tenure document
does not. Adoption of eucalypt tree farming in Thailand is not part of a land use intensification strategy. Instead, eucalypts
are used as an alternative crop for low productivity land, on which eucalypts are the most profitable crop. Eucalypt tree
farming also gives smallholders an opportunity to diversify their income. In addition, this alternative land use has the advantage
of requiring low labour inputs between planting and harvest. This is particularly advantageous for many tree growers who have
off-farm income or rely on hired labour for farming their land. 相似文献
59.
Krishnan HB Jang S Kim WS Kerley MS Oliver MJ Trick HN 《Journal of agricultural and food chemistry》2011,59(4):1223-1228
Legumes, including soybeans ( Glycine max ), are deficient in sulfur-containing amino acids, which are required for the optimal growth of monogastric animals. This deficiency can be overcome by expressing heterologous proteins rich in sulfur-containing amino acids in soybean seeds. A maize 27 kDa γ-zein, a cysteine-rich protein, has been successfully expressed in several crops including soybean, barley, and alfalfa with the intent to biofortify these crops for animal feed. Previous work has shown that the maize 27 kDa zein can withstand digestion by pepsin and elicit an immunogenic response in young pigs. By use of sera from patients who tested positive by ImmunoCAP assay for elevated IgE to maize proteins, specific IgE binding to the 27 kDa γ-zein is demonstrated. Bioinformatic analysis using the full-length and 80 amino acid sliding window FASTA searches identified significant sequence homology of the 27 kDa γ-zein with several known allergens. Immunoblot analysis using human serum that cross-reacts with maize seed proteins also revealed specific IgE-binding to the 27 kDa γ-zein in soybean seed protein extracts containing the 27 kDa zein. This study demonstrates for the first time the allergenicity potential of the 27 kDa γ-zein and the potential that this protein has to limit livestock performance when used in soybeans that serve as a biofortified feed supplement. 相似文献
60.
ABSTRACT: The present study reports the annual variation in consumption of the sea urchin Strongylocentrotus intermedius by avian predators on a rocky shore where the culture of sea urchins has been conducted. Carrion crow and a few gull species were the most abundant avian predators and consumed a large number of sea urchins. Crows consumed mostly natural sea urchins, approximately 36 kg ww/ha per year on the intertidal rocky bench, but the gull species consumed mostly cultured sea urchins, approximately 100 kg ww/ha per year in the culture area. The seasonal variation in the amount of sea urchins consumed by crows was higher than that by the gull species, presumably because of the difference in foraging behavior in association with the seasonal tidal cycle. The natural sea urchins consumed are an allochthonous input from the subtidal to the intertidal habitat, and thus, crow predation may not affect the natural and the cultured populations of the sea urchin. The gull species consumed much of the cultured sea urchin, and thus, may be regarded as an effective predator causing damage to sea urchin culture. The results suggest that further studies are needed to determine why the gull species selectively feed on cultured sea urchins. 相似文献