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991.
Cheng-Hua Huang Pamela D. Roberts Liane R. Gale Wade H. Elmer Lawrence E. Datnoff 《European journal of plant pathology / European Foundation for Plant Pathology》2013,136(3):509-521
Fusarium crown and root rot caused by Fusarium oxysporum f. sp. radicis-lycopersici (FORL) is a serious soilborne disease reducing tomato yields in Florida, a leading state in fresh market tomato production in the United States. One hundred and twenty five isolates of FORL were collected from the three main tomato-growing counties in Florida between 2006 and 2008. Vegetative compatibility groups (VCGs) and 10 microsatellite loci were used to infer the population structure of FORL. Up to 69.8 % of the isolates could be assigned to one of three VCGs, 0094, 0098 or 0099, with frequencies of 38.6, 24.4, and 6.8 % respectively. A medium level of population differentiation (Φst?=?0.159) was detected among the three counties, and three optimal clusters (populations) were supported by discriminant analysis of principal components. In addition, each population had some individuals that likely migrated from other populations. Migration probably played an important role in shaping the population structure of FORL since repeated VCGs and multilocus genotypes were observed in the three counties. Considerable migrants (> 1.33 migrants per generation) were also detected between the three counties, resulting in an increase in the effective population size and genetic diversity of F. oxysporum f. sp. radicis-lycopersici. Although migration is an important evolutionary force, mutation and parasexual recombination could not be completely ruled out as contributing causes to the genetic diversity of FORL. Management strategies that limit the movement of F. oxysporum f. sp. radicis-lycopersici are necessary to reduce the evolutionary potential of the pathogen. 相似文献
992.
Fernando Monroy Wim H. van der Putten Etienne Yergeau Simon R. Mortimer Henk Duyts T. Martijn Bezemer 《Soil biology & biochemistry》2012
Ecosystems consist of aboveground and belowground subsystems and the structure of their communities is known to change with distance. However, most of this knowledge originates from visible, aboveground components, whereas relatively little is known about how soil community structure varies with distance and if this variability depends on the group of organisms considered. In the present study, we analyzed 30 grasslands from three neighboring chalk hill ridges in southern UK to determine the effect of geographic distance (1–198 km) on the similarity of bacterial communities and of nematode communities in the soil. We found that for both groups, community similarity decayed with distance and that this spatial pattern was not related to changes either in plant community composition or soil chemistry. Site history may have contributed to the observed pattern in the case of nematodes, since the distance effect depended on the presence of different nematode taxa at one of the hill ridges. On the other hand, site-related differences in bacterial community composition alone could not explain the spatial turnover, suggesting that other factors, such as biotic gradients and local dispersal processes that we did not include in our analysis, may be involved in the observed pattern. We conclude that, independently of the variety of causal factors that may be involved, the decay in similarity with geographic distance is a characteristic feature of both communities of soil bacteria and nematodes. 相似文献
993.
Olivia Rice Simon H. Miller John P. Morrissey Fergal O’Gara 《Biology and Fertility of Soils》2012,48(2):235-238
Successful exploitation of bacterial inoculants in agriculture requires that the inoculant can colonize the crop rhizosphere
and then express the gene(s) of interest. This study focuses on two glucose-metabolizing genes that are associated with the
inorganic phosphate solubilization phenotype of Pseudomonas fluorescens: gcd, which encodes glucose dehydrogenase, and pqqB, which encodes a cofactor required for Gcd activity. Tn5-lux-gene fusions were created to assess the expression of these genes in situ on roots of two maize hybrids, DK315 and PR37Y15.
Expression was compared to in vitro levels in the presence of root exudates and different carbon sources. Although root exudates
from both varieties triggered similar levels of expression in in vitro cultures, there was a marked difference in situ, where
significantly higher expression levels of both genes were observed on DK315 roots. This correlates with a higher level of
rhizosphere colonization by the inoculant on this hybrid (over PR37Y15) and illustrates the importance of monitoring both
colonization and expression levels in tandem. In addition to demonstrating expression of these important genes in the rhizosphere,
this study also illustrates that variation can exist between cultivars or varieties and demonstrates a methodology to monitor
the expression of genes of interest in the rhizosphere of the selected crop variety on which the inoculant is to be applied. 相似文献
994.
Despite the effectiveness of primary treatment modalities for cancer, the side effects of treatments, medication resistance, and the deterioration of cachexia after disease progression lead to poor prognosis. A supportive treatment modality to overcome these limitations would be considered a major breakthrough. Here, we used two different target drugs to demonstrate whether a nutraceutical formula (fish oil, Se yeast, and micronutrient-enriched nutrition; NuF) can interfere with cancer cachexia and improve drug efficacy. After Lewis lung cancer (LLC) tumor injection, the C57BL/6 mice were orally administered targeted therapy drugs Iressa and Sutent alone or combined with NuF for 27 days. Sutent administration effectively inhibited tumor size but increased the number of lung metastases in the long term. Sutent combined with NuF had no significant difference in tumor weight and metastasis compare with Sutent alone. However, NuF slightly attenuated metastases number in lung may via mesenchymal marker N-cadherin suppression. NuF otherwise increased epithelial-like marker E-cadherin expression and induce NO-mediated intrinsic apoptotic pathway in tumor cells, thereby strengthening the ability of the targeted therapy drug Iressa for inhibiting tumor progression. Our results demonstrate that NuF can promote the anticancer effect of lung cancer to targeted therapy, especially in Iressa, by inhibiting HIF-1α and epithelial-mesenchymal transition (EMT) and inducing the apoptosis of lung cancer cells. Furthermore, NuF attenuates cancer-related cachectic symptoms by inhibiting systemic oxidative stress. 相似文献
995.
The effect of different nutrient media on growth, physicochemical, and agar properties of the marine algae Gracilaria cliftonii was investigated in ocean water (OW) and inland saline water (ISW). G. cliftonii fronds were cultured in 500-mL and 25-L containers with different nutrient media: Aquasol, Total, Guillard f2, Walnes, and Modified-Provasoli's Enriched Seawater in OW and ISW at 35 ppt. Specific growth rate (SGR) was higher in OW than ISW irrespective of nutrient media in both volumes. Growth of G. cliftonii in Guillard f2-supplemented OW was significantly higher than other nutrient media in both water types. Nutrient media had no influence on growth and agar properties. However, f2?supplemented OW resulted in significantly higher agar yield (58.3% db) as compared to other media. Either f2 or Walnes media are preferred nutrient sources for culturing G. cliftonii in ocean and inland saline water. 相似文献
996.
Helen Gurney‐Smith Nadia Plamondon Simon Yuan Christopher M Pearce 《Aquaculture Research》2013,44(8):1236-1253
The basket cockle (Clinocardium nuttallii) is a candidate species for aquaculture in the northeast Pacific. The aim of the current research was to assess the feasibility of C. nuttallii grow‐out, with an emphasis on growth performance and qualities affecting product marketability. In this article, we investigated the combined effects of culture mode (intertidal and off‐bottom suspended culture) and initial stocking density (1500, 3000, 10 500 and 21 000 ind m?2) on C. nuttallii survival and growth during the first year of grow‐out (May through October). In intertidal culture, cockles exhibited low survival and poor growth rates. In suspended culture, survival was consistently high (>96%) at all stocking densities tested; growth and condition parameters had the highest values at 1500 and 3000 ind m?2. The edible portion (meat yield) exceeded 40% of the whole wet weight at all stocking densities, occurrences of fouled and deformed cockles were <1% and no commensal species were observed. Depending on the minimum harvestable size and stocking density chosen, harvestable proportions constituted from 1.1% to 15.2% by October of the first grow‐out year in the suspended system. The effects of stocking density and depth on second year grow‐out performance of C. nuttallii are reported in a companion paper (Dunham et al. in this issue). 相似文献
997.
Helen Gurney‐Smith Nadia Plamondon Simon Yuan Christopher M Pearce 《Aquaculture Research》2013,44(8):1277-1299
We investigated the effects of culture mode (intertidal and off‐bottom suspended culture) and initial stocking density (5%, 10%, 35% and 70% bottom cover) on survival, growth and condition indices of three size cohorts (16, 22 and 32 mm initial shell length) of the basket cockle, Clinocardium nuttallii, during a second year of grow‐out. In addition, we evaluated the effects of depth (2, 4 and 6 m) in suspended culture. All size cohorts demonstrated significantly higher growth rates, soft‐tissue biomass and condition indices in the off‐bottom suspended system compared to the intertidal one. In suspended culture, however, C. nuttallii exhibited sub‐optimal survival, shell deformities and heavy fouling. For all size cohorts, stocking density had a significant effect on most growth and condition parameters, except meat yield indices, in both culture modes. An initial maximum stocking density of 10% cover is recommended for all size cohorts. Culture depth did not have a consistent statistically significant effect on any of the growth or condition parameters. Depending on the grow‐out scenario, stocking density and harvestable size chosen, the cumulative harvestable proportion after the second year of grow‐out constituted 15.5–63.1% of the seed planted. Our results could be used to develop and improve culture techniques for C. nuttallii and other cockle species. 相似文献
998.
Simon R. Bush Sonsai Kosy 《Aquaculture Economics & Management (Blackwell Science)》2013,17(3):285-311
This article provides a detailed empirical study of investment patterns in small-scale rural aquaculture and its relation to pond location based on a systematic fish pond survey in Lao PDR. Nominal investment categories of fish ponds were created based on stocking rate, feed and water and then spatially cross-referenced with a range of environmental factors, including distance to roads, land use, and distance to water resources. Contrary to current aquaculture development policies, the results show the dynamic nature of fish ponds as a source of water, native fish and exotic fish. It is concluded that policy makers and extension officers can make use of simple diagnostic models of fish pond use and investment to develop more contingent support to farmers that takes into consideration a wider portfolio of living aquatic resources in rural communities. 相似文献
999.
Simon R. Bush Nguyen Tri Khiem Le Xuan Sinh 《Aquaculture Economics & Management (Blackwell Science)》2013,17(4):271-293
The Vietnamese government's policies for an export-led economy have supported the rapid growth of Pangasius production but have had limited success in mitigating the environmental and social impacts stemming from unplanned and ad hoc expansion. Recognising the poor performance of state regulation the industry and government have turned to private or market-based environmental and social standards for Pangasius production. The success of these private governance arrangements is dependent on the capacity of producers to comply with standards within their wider environmental, social, cultural and economic context. This paper reviews current concerns over the sustainability of Pangasius production and draws attention to the challenges private governance initiatives face in steering towards sustainable production. 相似文献
1000.