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排序方式: 共有82条查询结果,搜索用时 15 毫秒
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Berta Caballero-López José M. Blanco-Moreno Nicolás Pérez-Hidalgo José M. Michelena-Saval Juli Pujade-Villar Emilio Guerrieri José A. Sánchez-Espigares F. Xavier Sans 《Journal of pest science》2012,85(1):81-88
The aphid–natural enemy interaction in winter wheat fields constitutes a complex system that has been frequently studied because
of its implication for biological control. However, not all of the aphids living in cereal fields are crop pests, as there
are also aphids living on weeds that may serve as alternative hosts or prey for aphid parasitoids or predators. In this context,
a concomitant survey of the plant and insect communities was conducted to understand how different plant communities affect
the abundance and richness of aphids and the interactions with their natural enemies. The plant community was split into functional
groups (grasses, legumes and forbs), and the aphid community was divided into feeding groups according to their host preferences
(specialists in grasses or forbs). The grass aphids, which dominated the total aphid catches, responded positively to grass
cover, which was particularly enhanced in the conventional fields. Conversely, the forb aphids, which mainly conditioned the
total species richness of the aphids, were closely correlated with the local abundance of legumes. The system of cereal aphid-parasitoids
was enhanced in the conventional fields, where the abundance of grasses was higher, whereas the legumes of the organic fields
indirectly played a key role in enhancing the richness of the parasitoids and the abundance of predators. Our findings indicate
that a bottom-up effect exists throughout the plant community, aphids, and aphidophagous insects and that plant community
characteristics should be considered to better understand cereal aphid control. 相似文献
3.
During three consecutive seasons, two different deficit irrigation strategies were compared with control fully irrigated trees
regarding their capacity to induce early bloom and harvest in “Algerie” loquat. The first strategy, a continuous deficit irrigation
strategy, consisted in a uniform reduction of 20% water needs through the entire season; the second strategy, a regulated
deficit irrigation approach, while accounting for the same global reduction of 20% loquat water needs, concentrated water
shortages after harvest from mid-May through the end of August. Regulated deficit irrigation resulted more successful. Postharvest
regulated deficit irrigation advanced full bloom 10–20 days depending on the season. Such enhancement led to more precocious
and valuable yield, with an average increase of fruit value of 0.21 € kg−1. The effects of continuous deficit irrigation were less noticeable and average fruit value was increased 0.08 € kg−1. Yield and fruit quality were not affected for the different deficit irrigation strategies. Water savings established around
1450 m3 ha−1 year−1. Deficit irrigation rose water use efficiency up to more than a 40%. 相似文献
4.
选择了4种家鱼作指示生物,用紫外分光光度法测定其白肌中RNA和DNA的含量。结果表明:同种鱼,污染区的RNA含量显著低于对照区,白鲢和鳊鱼白肌中RNA/DNA低于对照区;不同种的鱼,污染区鱼肌核酸比对照区下降的程度有鳊鱼>白鲢>鲫鱼和鲤鱼的趋势。鱼肌核酸下降同水体重金属污染有一定联系,RNA是比RNA/DNA更合适的指标,鳊鱼和白鲢是比鲫鱼和鲤鱼更敏感的指示生物。 相似文献
5.
三角网格曲面的参数化是车身曲面重建过程中的一个重要环节。三角网格曲面参数化是一个由3D到2D的可逆变换,可将对三角网格曲面的操作转化为对二维平面网格的操作,这样就大大地减小了应用操作的复杂性。在车身曲面重建的基础上研究了一种既保角又保面积的参数化方法,并判断其是否适应于车身曲面重建过程中的三角网格参数化。通过VC6.0编程结合UG软件为平台,应用车身实例来实现这种参数化方法的算法。 相似文献
6.
Touriño S Selga A Jiménez A Juliá L Lozano C Lizárraga D Cascante M Torres JL 《Journal of agricultural and food chemistry》2005,53(12):4728-4735
Pine (Pinus pinaster) bark is a rich source of procyanidin oligomers. From a total polyphenolic extract, we have generated fractions of different procyanidin composition. The mixtures, devoid of gallate esters, were active as free radical scavengers against ABTS(*+), DPPH, and HNTTM. Pine bark fractions were tested for antioxidant activity in solution (hydrogen donation and electron transfer) and emulsion (inhibition of lipid peroxidation) and compared with their galloylated counterparts from grape origin. While galloylation clearly influenced the free radical scavenging efficiency in solution, it did not seem to play a determinant role in protection against lipid peroxidation in emulsion. The fractions were very mild inhibitors of cell proliferation. Because gallate esters appear to interfere with crucial cell functions, gallate free pine procyanidins may be the innocuous chemopreventative agents of choice for many applications in food and skin protection. 相似文献
7.
Milner RJ Peyton J Cooke K Fox LE Gallagher A Gordon P Hester J 《Journal of the American Veterinary Medical Association》2005,227(7):1118-1122
OBJECTIVE: To determine response rates and survival times for cats with lymphoma treated with the University of Wisconsin-Madison chemotherapy protocol. DESIGN: Retrospective study. ANIMALS: 38 cats with lymphoma. PROCEDURE: Medical records were reviewed, and information on age, sex, breed, FeLV and FIV infection status, anatomic form, clinical stage, and survival time was obtained. Immunophenotyping was not performed. RESULTS: Mean +/- SD age of the cats was 10.9 +/- 4.4 years. Overall median survival time was 210 days (interquartile range, 90 to 657 days), and overall duration of first remission was 156 days (interquartile range, 87 to 316 days). Age, sex, anatomic form, and clinical stage were not significantly associated with duration of first remission or survival time. Eighteen of the 38 (47%) cats had complete remission, 14 (37%) had partial remission, and 6 (16%) had no response. Duration of first remission was significantly longer for cats with complete remission (654 days) than for cats with partial remission (114 days). Median survival time for cats with complete remission (654 days) was significantly longer than median survival time for cats with partial remission (122 days) and for cats with no response (11 days). CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that a high percentage of cats with lymphoma will respond to treatment with the University of Wisconsin-Madison chemotherapy protocol. Age, sex, anatomic form, and clinical stage were not significantly associated with duration of first response or survival time, but initial response to treatment was. 相似文献
8.
Loading in implant dentistry to accelerate prosthodontic treatment has been receiving increasing interest. The aim of this study was to investigate the effect of an early controlled lateral loading (after 7 days) on the establishment of osseointegration by means of resonance frequency analysis. Two groups of six beagle dogs each were used. Group I had implants without loading. Group II had implants loaded with a new prototype compression abutment that created controlled semi-static loading. Loaded implants showed slightly better stability after 5 weeks of healing, but the difference was not significant. We concluded that controlled loading is beneficial to maintain, and even improve, stability during the early critical healing period. 相似文献
9.
马铃薯晚疫病菌(Phytophthora infestans)能侵染多种茄科植物,它引起的马铃薯晚疫病,是马铃薯生产中的第一大病害。为了开发能在田间快速检测马铃薯晚疫病病原的方法,利用P. infestans T30-4基因组测序数据的contig 1.18131,设计qPCR和LAMP引物,优化扩增条件后得到引物的特异性和灵敏度,最后通过检测田间收获薯块,比较形态学传统方法、qPCR及LAMP的差异。特异性检测结果发现,qPCR和LAMP仅在含有P. infestans DNA模板的体系有阳性扩增,在寄主和其他微生物DNA中均无扩增;在优化的条件下,qPCR和LAMP的检测下限可达1×10 -6ng/μL,在有寄主和其他微生物DNA存在的条件下,引物的灵敏度没有显著差异。利用两种快速方法对在大理、丽江及昆明3个地区田间收获薯块上检测发现,qPCR和LAMP方法得到的检出率差异极为不显著(P=0.420),两种快速检测方法和形态学鉴定方法检出率差异极显著(P=0.009)。在大理、丽江及昆明3个地区的薯块中,两种分子检测方法检出率均比形态学方法高。其中,qPCR检测方法比形态学方法分别提高了12.00%、2.00%、8.70%;LAMP检测方法比形态学方法分别提高了11.30%、2.00%、8.70%。 相似文献