全文获取类型
收费全文 | 158篇 |
免费 | 25篇 |
专业分类
林业 | 24篇 |
农学 | 1篇 |
基础科学 | 1篇 |
17篇 | |
综合类 | 11篇 |
农作物 | 7篇 |
水产渔业 | 32篇 |
畜牧兽医 | 46篇 |
园艺 | 7篇 |
植物保护 | 37篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 6篇 |
2019年 | 11篇 |
2018年 | 14篇 |
2017年 | 13篇 |
2016年 | 15篇 |
2015年 | 7篇 |
2014年 | 9篇 |
2013年 | 12篇 |
2012年 | 10篇 |
2011年 | 11篇 |
2010年 | 7篇 |
2009年 | 7篇 |
2008年 | 7篇 |
2007年 | 10篇 |
2006年 | 8篇 |
2005年 | 1篇 |
2004年 | 4篇 |
2003年 | 6篇 |
2002年 | 3篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有183条查询结果,搜索用时 0 毫秒
91.
92.
93.
Fish oxygen requirement is a fundamental variable of aquaculture system design and management, as it is the basis for determining water flow rates for sustaining stock. A study on oxygen consumption of California halibut (Paralichthys californicus) between 3.2 and 165.6 g was conducted in small raceways (2.41 m long, 0.28 m wide, and 0.22 m high; operational water depth between 0.05 and 0.10 m with a quiescent zone 19 cm long in the effluent section) working as open respirometers in a recirculating system under farm-like conditions. The fish were fed commercial dry pelleted feeds at a ratio of ~0.70–3.00% of body weight (BW) and stocked at densities between 94% and 316% percent coverage area (PCA). Oxygen consumption rates were determined by mass balance calculations. The mean and maximum oxygen consumption rates (g O2/kg fish/day) for juvenile California halibut under the conditions tested can be expressed by Mday = 15.077W?0.2452 and Mday = 17.266W?0.2033, respectively, where W is fish weight in grams. The determination of oxygen consumption by California halibut in farm-like conditions provides valuable information on the oxygen requirement of these fish in an aquacultural setting. This information can be used for designing and sizing a rearing facility for the intensive culture of California halibut. 相似文献
94.
Adriana Schultz Moreira Laura González-Torres Raul Olivero-David Sara Bastida Juana Benedi Francisco J. Sánchez-Muniz 《Plant foods for human nutrition (Dordrecht, Netherlands)》2010,65(3):290-298
The effects of diets including restructured meats (RM) containing Wakame or Nori on total liver glutathione status, and several
antioxidant enzyme gene expressions and activities were tested. Six groups of ten male growing Wistar rats each were fed a
mix of 85% AIN-93 M diet and 15% freeze-dried RM for 35 days. The control group (C) consumed control RM, the Wakame (W) and
the Nori (N) groups, RM with 5% Wakame and 5% Nori, respectively. Animals on added cholesterol diets (CC, CW, and CN) consumed
their corresponding basal diets added with cholesterol (2%) and cholic acid (0.4%). Alga and dietary cholesterol significantly
interact (P < 0.002) influencing all enzyme expressions but not activities. The cholesterol supplement decreased most enzyme expression
and activity. W-RM vs. C-RM increased (P < 0.05) expression of GPx, GR, Mn-SOD, and Cu,Zn-SOD and decreased that of catalase. N-RM vs. C-RM increased (P < 0.05) expression of catalase and Mn-SOD. GR activity increased in W-RM rats while SOD activity increased, but that of Se-GPx
decreased in N animals. W-RM increased total and reduced glutathione and decreased the redox index. CN diet induced significantly
lower plasma cholesterol levels (P < 0.001) than the CW diet. In conclusion, Nori-RM is a hypocholesterolemic food while Wakame-RM is an antioxidant food. This
should be taken into account when including this kind of RM as potential functional foods in human. 相似文献
95.
This paper addresses the issue of automatic wood defect classification. A tree-structure support vector machine (SVM) is proposed
to classify four types of wood knots by using images captured from lumber boards. Simple and effective features are proposed
and extracted by partitioning the knot images into three distinct areas, followed by utilizing a novel order statistic filter
to yield an average pseudo color feature in each area. Excellent results have been obtained for the proposed SVM classifier
that is trained by 800 wood knot images. Performance evaluation has shown that the proposed SVM classifier resulted in an
average classification rate of 96.5% and false alarm rate of 2.25% over 400 test knot images. Future work will include more
extensive tests on large data set and the extension of knot types. 相似文献
96.
97.
Survival,male morphotypes,female and male proportion,female reproductive status and tag loss in crosses among three populations of freshwater prawn Macrobrachium rosenbergii (de Man) in India 下载免费PDF全文
Bindu R Pillai Kanta D Mahapatra Raul W Ponzoni Lopamudra Sahoo P L Lalrinsanga Wagdy Mekkawy Hooi Ling Khaw Nguyen H Nguyen Swagathika Mohanty Sovan Sahu Gunamaya Patra 《Aquaculture Research》2015,46(11):2644-2655
The present study examined the variation in survival, proportion of male morphotypes, female and male proportion, female reproductive status and tag losses in nine crosses from a complete (3 × 3) diallel mating of three populations of Macrobrachium rosenbergii in India. The populations originated from Gujarat (north‐west), Kerala (south‐west) and Odisha (east), representing different agro‐ecological regions in India. Progeny from 60 families (4773 juveniles) were individually tagged and reared for 16–17 weeks in earthen ponds. Binary logistic regression was used to analyse the data. Survival rate was greatest (0.88) for Kerala × Odisha (KO; the first letter represents the sire), whereas it was lowest (0.75) for both Kerala × Kerala (KK) and Gujarat × Kerala (GK). Significantly greater proportions of large male morphotypes were observed in KK cross and in combinations involving Kerala population. The highest proportion of immature females, as well as of non‐berried females, was observed in the Odisha × Odisha (OO) cross. Tag loss was greatest for KK (0.35) and lowest for GG (0.19). We found significant variations among crosses for all studied traits suggesting the possibility of including them in genetic improvement programmes of this species. 相似文献
98.
Leaf‐cutting ants are generally recognized as important pest species in Neotropical America. They are eusocial insects that exhibit social organization, foraging, fungus‐cultivation, hygiene and a complex nest structure, which render their management notoriously difficult. A lack of economic thresholds and sampling plans focused on the main pest species preclude the management of leaf‐cutting ants; such management would facilitate their control and lessen insecticide overuse, particularly the use of insecticidal baits. Recent restrictions on the use of synthetic compounds for such purposes impose additional challenges for the management of leaf‐cutting ants. Considerable effort has been exerted regarding these challenges, which are addressed herein, but which also remain challenges that are yet to be conquered. © 2013 Society of Chemical Industry 相似文献
99.
100.
Diogo Alagador Maria Trivi?o Jorge Orestes Cerdeira Raul Brás Mar Cabeza Miguel Bastos Araújo 《Landscape Ecology》2012,27(2):291-301
Habitat fragmentation is one of the greatest threats to biodiversity. To minimise the effect of fragmentation on biodiversity,
connectivity between otherwise isolated habitats should be promoted. However, the identification of linkages favouring connectivity
is not trivial. Firstly, they compete with other land uses, so they need to be cost-efficient. Secondly, linkages for one
species might be barriers for others, so they should effectively account for distinct mobility requirements. Thirdly, detailed
information on the auto-ecology of most of the species is lacking, so linkages need being defined based on surrogates. In
order to address these challenges we develop a framework that (a) identifies environmentally-similar habitats; (b) identifies
environmental barriers (i.e., regions with a very distinct environment from the areas to be linked), and; (c) determines cost-efficient
linkages between environmentally-similar habitats, free from environmental barriers. The assumption is that species with similar
ecological requirements occupy the same environments, so environmental similarity provides a rationale for the identification
of the areas that need to be linked. A variant of the classical minimum Steiner tree problem in graphs is used to address
c). We present a heuristic for this problem that is capable of handling large datasets. To illustrate the framework we identify
linkages between environmentally-similar protected areas in the Iberian Peninsula. The Natura 2000 network is used as a positive
‘attractor’ of links while the human footprint is used as ‘repellent’ of links. We compare the outcomes of our approach with
cost-efficient networks linking protected areas that disregard the effect of environmental barriers. As expected, the latter
achieved a smaller area covered with linkages, but with barriers that can significantly reduce the permeability of the landscape
for the dispersal of some species. 相似文献