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11.
An oxygen electrode was used to estimate the respiration rate of basal 1 cm sections of Prosopis juliflora cuttings. The respiration rate per unit dry mass decreased linearly with increasing diameter at a rate of 0.42 nmol02g–1s–1mm–1 between the range of 1–3 mm diameter. However, as a result of increased mass, total respiration for the whole 1 cm section of tissue increased linearly with increasing diameter. The average respiration rate of the basal 1 cm of stem tissue, measured 14 days after insertion in the propagator, was almost double that of the 1 cm section of tissue above it (1.01 nmol02g–1s–1 compared to 0.57 nmol02g–1s–1). The value of this technique as an aid to our understanding of the development of adventitious roots is discussed. 相似文献
12.
Effects of dietary lipid level and vegetable oil on fatty acid metabolism in Atlantic salmon (Salmo salar L.) over the whole production cycle 总被引:1,自引:0,他引:1
D.R. Tocher J.G. Bell F. McGhee J.R. Dick J. Fonseca-Madrigal 《Fish physiology and biochemistry》2003,29(3):193-209
Changes in fatty acid metabolism in Atlantic salmon (Salmo salar) induced by vegetable oil (VO) replacement of fish oil (FO) and high dietary oil in aquaculture diets can have negative impacts
on the nutritional quality of the product for the human consumer, including altered flesh fatty acid composition and lipid
content. A dietary trial was designed to investigate the twin problems of FO replacement and high energy diets in salmon throughout
the entire production cycle. Salmon were grown from first feeding to around 2 kg on diets in which FO was completely replaced
by a 1:1 blend of linseed and rapeseed oils at low (14–17%) and high (25–35%) dietary oil levels. This paper reports specifically
on the influence of diet on various aspects of fatty acid metabolism. Fatty acid compositions of liver, intestinal tissue
and gill were altered by the diets with increased proportions of C18 polyunsaturated fatty acids and decreased proportions of n-3 highly unsaturated fatty acids (HUFA) in fish fed VO compared
to fish fed FO. HUFA synthesis in hepatocytes and enterocytes was significantly higher in fish fed VO, whereas β-oxidation
was unaltered by either dietary oil content or type. Over the entire production cycle, HUFA synthesis in hepatocytes showed
a decreasing trend with age interrupted by a large peak in activity at seawater transfer. Gill cell prostaglandin (PG) production
showed a possible seasonal trend, with peak activities in winter and low activities in summer and at seawater transfer. PG
production in seawater was lower in fish fed the high oil diets with the lowest PG production generally observed in fish fed
high VO. The changes in fatty acid metabolism induced by high dietary oil and VO replacement contribute to altered flesh lipid
content and fatty acid compositions, and so merit continued investigation to minimize any negative impacts that sustainable,
environmentally-friendly and cost-effective aquaculture diets could have in the future.
Abbreviations: FO - fish oil; HUFA - highly unsaturated fatty acids acids (carbon chain length ≥C
20 with ≥3 double bonds); LO - linseed oil; RO - rapeseed oil; VO - vegetable oil.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
13.
The effect of dietary n−3 and n−6 polyunsaturated fatty acids (PUFAs) on juvenile Arctic charr Salvelinus alpinus (L.) were investigated with respect to essential fatty acid (EFA) deficiency and lipid metabolism using one commercial and
12 casein-based test diets. Arctic charr with mean weight of 1.6g were fed test diets for 12 weeks at 10°C. At the end of
the feeding, blood, liver, muscle and whole fish were sampled to determine haematocrit, haemoglobin, water content, lipid
and fatty acid composition. Charr fed diets containing 0–1.0% n−3 PUFAs showed typical EFA deficiency signs: fatty liver or
elevated water content in whole body or substantial accumulation of 20:3n−9 in liver polar lipids. These signs were less apparent
or disappeared when charr were fed diets containing ≥ 2.0% 18:3n−3. No correlation was found between dietary PUFAs and haematocrit
or haemoglobin values. Significant changes in fatty acid composition of liver polar lipids in charr fed dietary PUFAs indicate
that charr can convert 18:3n−3, 18:2n−6 and 20:5n−3 into long-chain PUFAs. While charr had a direct incorporation of dietary
22:6n−3 into liver and muscle there appears to be preferential utilization of n−3 PUFAs for elongation and desaturation. The
conversion of 18:4n−3 was less in muscle than in livers. These findings, combined with data on growth and feed efficiency
reported previously by Yang and Dick (1993), indicate that charr require 1−2% dietary 18:3n−3 (dry weight). Small amounts
of dietary 18:2n−6 (up to 0.7%) did not have detrimental effects on charr. 相似文献
14.
The static or declining supply of fish oil from industrial fisheries demands the search of alternatives, such as plant (vegetable)
oils, for diets in expanding marine aquaculture. Vegetable oils are rich in C18 polyunsaturated fatty acids but devoid of the n-3 highly unsaturated fatty acids in fish oils. Previous studies, primarily
with salmonids, have shown that including vegetable oils in their diets increased hepatocyte fatty acid desaturation. In the
present study, we have investigated the effects of dietary partial substitution of fish oil (FO) with rapeseed oil (RO), linseed
oil (LO) and olive oil (OO) on the desaturation /elongation and, -oxidation capacities of [1-14C]18:3n-3 in isolated hepatocytes from European sea bass (Dicentrarchus labrax L.), in a simultaneous combined assay. Fish were fed during 34 weeks with diets containing 100% FO, or RO, LO and OO, each
included at 60% with the balance being met by FO, with no detrimental effect upon growth or survival. The highest total desaturation
rates were found in hepatocytes of fish fed FO diet (0.52±0.08 pmol/h/mg protein) and OO diet (0.43±0.09 pmol/h/mg protein),
which represented 3.2% and 2.7% of total [1-14C]18:3n-3 incorporated, respectively. In contrast, lowest desaturation rates were presented by hepatocytes of fish fed LO
and RO diets (0.23±0.06 and 0.14±0.05 pmol/h/mg protein, respectively) represented 1.4% and 0.9% of total [1-14C]18:3n-3 incorporated, respectively. The rates of [1-14C]18:3n-3 β-oxidized were between 11-fold and 35-fold higher than desaturation. However, no significant differences were observed
among β-oxidation activities in hepatocytes of fish fed any of the diets. The present study demonstrated that the European
sea bass, as a carnivorous marine fish, presented a ‘marine’ fish pattern in the metabolism of 18:3n-3 to 20:5n-3 and 22:6n-3.
This species appeared to have all the enzymic activities necessary to produce 22:6n-3 but presented only extremely low rates
of fatty acid bioconversion. Furthermore, nutritional regulation of hepatocyte fatty acid desaturation was minimal, and dietary
vegetable oils did not increase desaturase activities, and in RO and LO treatments the activity was significantly lower.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
Douglas R. Tocher John D. Castell James R. Dick John R. Sargent 《Fish physiology and biochemistry》1994,13(6):451-461
The direct effects of osmotic pressure (salinity) on growth performance and lipid composition were investigated in fish cells
in culture. Cell lines from a relatively stenohaline marine species, turbot (Scophthalmus maximus) (TF) and an anadromous species, Atlantic salmon (AS) were cultured in media supplemented with NaCl to produce osmotic pressures
varying from 300 to 500 mOsm kg−1. The growth rates of the two cell lines were affected in a similar manner by the salinity of the media with the rank order
for both peak cell numbers and growth rates up to the day of peak cell number being 300 > 350 > 400 > 450 > 500 mOsm kg−1. Cell death occurred in both cell lines in older cultures at all salinities with the greatest loss of viable cells in media
of 300 and 350 kg−1. However, there were quantitative and qualitative differences between the cell lines in their lipid metabolism in response
to the salinity of the media. The lipid content expressed per cell showed a positive correlation between lipid per cell and
salinity in TF cells, but this was less apparent in AS cells. The percentage of total polar lipid classes increased with increasing
salinity in TF cells due mainly to graded increases in the percentages of choline phospholipids. In contrast, there were no
significant differences in the proportions of polar and neutral lipid classes with salinity in AS cells. The only significant
effect of salinity in AS cells was a decreased proportion of dimethylacetals in total lipid at the highest salinity. The same
significant effect of salinity on dimethylacetal content of total lipid was observed in TF cells. However, in addition there
was a graded decrease in the percentage of 18:2n-9 in TF cell total lipid with increasing salinity. This was accompanied by
increased percentages of total n-3 and n-6 PUFA with higher proportions of both groups of PUFA at 450 and 500 compared with
300 mOsm kg−1. The results show that environmental salinity, in the absence of hormonal or other physiological stimuli, has direct effects
on the growth and lipid metabolism of fish cells and that these effects differ in cells from different fish species. 相似文献
16.
Dick van der Zee 《Landscape Ecology》1990,4(4):225-236
The relation between landscape and recreation is very complex. There are various, interrelated approaches to analyze this relation, such as land evaluation, impact analysis, spatial behaviour analysis, and assessment of the scenic quality of the landscape or landscape evaluation. In many of these approaches airphoto interpretation can be a useful tool. 相似文献
17.
18.
Inheritance of fiber quality and lint yield in a chemically mutated population of cotton 总被引:2,自引:0,他引:2
Andy D. Herring Dick L. Auld M. Dean Ethridge Eric F. Hequet E. Bechere Cary J. Green Roy G. Cantrell 《Euphytica》2004,136(3):333-339
The narrow germplasm base of the upland cotton (Gossypium hirsutum L.), grown on the Texas high plains historically, has limited improvement of fiber quality. Chemical mutagenesis and subsequent selection have helped the development of lines with improved fiber quality in cultivars adapted to this region. This study was conducted to determine the inheritance of improvements in fiber quality. M3 lines with divergent fiber properties of micronaire, length, and strength were selected from a population of Paymaster HS 200 treated with 3% v/v ethyl methanesulfonate (EMS) for two hours. The 115 selected lines of M4 and M5 generation were evaluated for fiber quality and lint yield. Regression of the M4 and M5 on the M3 generation, as well as the M5 on the M4 was used to generate narrow sense heritability coefficients. Significant variations were observed between the mutant lines in all generations except for lint yield in the M5 (1997). The highest heritability estimates were found in fiber length (h
2= 0.29** to 0.46**). Micronaire and strength showed intermediate heritability estimates of h
2= 0.14 to 0.19, while lint yield had a very low heritability estimate of h
2= 0.03. Fiber length and strength were correlated (r= 0.58** to 0.46**) in all the three generations. The mutants identified in these studies have the potential to improve fiber quality of upland cotton without introducing alien genes that may reduce adaptation to short growing season production regions. 相似文献
19.
Lymphoid cell-glioma cell interaction enhances cell coat production by human gliomas: novel suppressor mechanism 总被引:1,自引:0,他引:1
S J Dick B Macchi S Papazoglou E H Oldfield P L Kornblith B H Smith M K Gately 《Science (New York, N.Y.)》1983,220(4598):739-742
Certain human glioma lines produce mucopolysaccharide coats that impair the generation of cytolytic lymphocytes in response to these lines in vitro. Coat production is substantially enhanced by the interaction of glioma cells with a macromolecular factor released by human peripheral blood mononuclear cells in culture. This interaction thus constitutes an unusual mechanism by which inflammatory cells may nonspecifically suppress the cellular immune response to at least one class of solid tumors in humans. 相似文献
20.
The study of past forest change provides a necessary historical context for evaluating the outcome of human-induced climate change and biological invasions. Retrospective analyses based on fossil and genetic data greatly advance our understanding of tree colonization, adaptation, and extinction in response to past climatic change. For instance, these analyses reveal cryptic refugia near or north of continental ice sheets, leading to reevaluation of postglacial tree migration rates. Species extinctions appear to have occurred primarily during periods of high climatic variability. Transoceanic dispersal and colonization in the tropics were widespread at geological time scales, inconsistent with the idea that tropical forests are particularly resistant to biological invasions. 相似文献