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1.
Seasonal variations in individual contacts give rise to a complex interplay between host demography and pathogen transmission. This is particularly true for wild populations, which highly depend on their natural habitat. These seasonal cycles induce variations in pathogen transmission. The seasonality of these biological processes should therefore be considered to better represent and predict pathogen spread. In this study, we sought to better understand how the seasonality of both the demography and social contacts of a mountain ungulate population impacts the spread of a pestivirus within, and the dynamics of, this population. We propose a mathematical model to represent this complex biological system. The pestivirus can be transmitted both horizontally through direct contact and vertically in utero. Vertical transmission leads to abortion or to the birth of persistently infected animals with a short life expectancy. Horizontal transmission involves a complex dynamics because of seasonal variations in contact among sexes and age classes. We performed a sensitivity analysis that identified transmission rates and disease-related mortality as key parameters. We then used data from a long-term demographic and epidemiological survey of the studied population to estimate these mostly unknown epidemiological parameters. Our model adequately represents the system dynamics, observations and model predictions showing similar seasonal patterns. We show that the virus has a significant impact on population dynamics, and that persistently infected animals play a major role in the epidemic dynamics. Modeling the seasonal dynamics allowed us to obtain realistic prediction and to identify key parameters of transmission.
Electronic supplementary material
The online version of this article (doi:10.1186/s13567-015-0218-8) contains supplementary material, which is available to authorized users. 相似文献2.
3.
Gordon D. Hastie Gi‐Mick Wu Simon Moss Pauline Jepp Jamie MacAulay Arthur Lee Carol E. Sparling Clair Evers Douglas Gillespie 《水产资源保护:海洋与淡水生态系统》2019,29(Z1):119-130
- Many marine industries may pose acute risks to marine wildlife. For example, tidal turbines have the potential to injure or kill marine mammals through collisions with turbine blades. However, the quantification of collision risk is currently limited by a lack of suitable technologies to collect long‐term data on marine mammal behaviour around tidal turbines.
- Sonar provides a potential means of tracking marine mammals around tidal turbines. However, its effectiveness for long‐term data collection is hindered by the large data volumes and the need for manual validation of detections. Therefore, the aim here was to develop and test automated classification algorithms for marine mammals in sonar data.
- Data on the movements of harbour seals were collected in a tidally energetic environment using a high‐frequency multibeam sonar on a custom designed seabed‐mounted platform. The study area was monitored by observers to provide visual validation of seals and other targets detected by the sonar.
- Sixty‐five confirmed seals and 96 other targets were detected by the sonar. Movement and shape parameters associated with each target were extracted and used to develop a series of classification algorithms. Kernel support vector machines were used to classify targets (seal vs. nonseal) and cross‐validation analyses were carried out to quantify classifier efficiency.
- The best‐fit kernel support vector machine correctly classified all the confirmed seals but misclassified a small percentage of non‐seal targets (~8%) as seals. Shape and non‐spectral movement parameters were considered to be the most important in achieving successful classification.
- Results indicate that sonar is an effective method for detecting and tracking seals in tidal environments, and the automated classification approach developed here provides a key tool that could be applied to collecting long‐term behavioural data around anthropogenic activities such as tidal turbines.
4.
This paper takes a close look at the urban governance and political culture of Macao, the world largest casino city. Macao has experienced spectacular economic growth since gaming liberalisation in 2002 and China's Free Individual Travel scheme launched in 2003. However, the booming gaming sector has crowded out other sectors of Macao. It has not only made the city's economy mono‐structured and consequently extremely vulnerable to external shocks and fluctuations but also induced serious social divisions and political controversies within the local community. By tracing the root cause of the ongoing dilemma and crisis in the mode of governance, the dynamic relationships between formal and informal institutions, consensus politics and the social group culture are intensively discussed in a historical context. In fact, the sustainable development of the former Portuguese colony has largely been hindered by its residents' passive attitudes toward political communication, non‐transparent urban governance, the absence of a middle class and the dominance of pro‐establishment social groups. 相似文献
5.
Saengchan Senapin Kornsunee Phiwsaiya Pauline Kiatmetha Boonsirm Withyachumnarnkul 《Aquaculture International》2011,19(4):693-704
A recent study showed Thalassiosira weissflogii to be a diatom containing suitable nutrition for larviculture of the black tiger shrimp, Penaeus monodon. Accurate and practical identification of this diatom species is therefore important for commercial hatcheries. The purpose
of this study was to establish a DNA-based method of identification to supplement morphological examination, avoiding confusion
with other Thalassiosira sp. Primers, 18SF/28SR1, specific for ribosomal DNA genes (3′-end of 18S rDNA through 5′-end of 28S rDNA, covering two internal
transcribed spacers), were employed as a first-step polymerase chain reaction, followed by a second nested amplification using
specifically designed primers, ITS1-F-D/ITS1-R-D. The nested-PCR result revealed specificity in the detection, distinguishing
T. weissflogii from T. pseudonana, Cyclotella meneghiniana, and Chaetoceros sp., and the PCR fragment of the amplified region had a sequence that was 99% identical to the T. weissflogii sequence held by GenBank. 相似文献
6.
Knut Schneider Maria-Belen Turrion Pauline F. Grierson Juan F. Gallardo 《Biology and Fertility of Soils》2001,34(3):151-155
Acid phosphatase activity (APA), labile P fractions and fine root growth were studied in an oak (Quercus pyrenaica Willd.) forest in the Sierra de Gata, in western central Spain. Soils in the region are acid and rich in organic matter, with low levels of extractable inorganic P but with a high proportion of organic P. In such soils, the activity of phosphatase enzymes is likely to be important for the control of P mineralization and P cycling and, consequently, can affect the availability of P for plant uptake. The biomass of fine roots was about 25-fold that of leaf litter, demonstrating a high allocation of C resources to the root system in order to compensate for a low availability of soil nutrients. The study compared plots fertilized with triple superphosphate (100 kg P ha-1) to control (unfertilized) plots. Fertilizer application had no significant effect on APA and fine root density; however, there were significant differences in available and microbial P. Spatial and seasonal variations in the APA were related to plant root density and biotic demand. Seasonal differences in the APA may also be the consequence of changes in the amount of hydrolysable organic substrates at different times of the year. 相似文献
7.
Pauline Oker-Blom 《Agricultural and Forest Meteorology》1985,34(1):31-40
Using a model of shoot geometry the distribution of irradiance at the needle surface area of a shoot in different radiation conditions is simulated and shoot photosynthesis calculated. It is shown that the distribution of irradiance is very sensitive to radiation field geometry, affecting the efficiency of the utilization of radiant energy in photosynthesis. As a result, the photosynthetic response of a shoot in natural conditions is, for instance, highly dependent on the proportions of direct and diffuse solar radiation, being higher the greater is the proportion of diffuse radiation. 相似文献
8.
Pauline Kiatmetha Wipawan Siangdang Boosya Bunnag Saengchan Senapin Boonsirm Withyachumnarnkul 《Aquaculture International》2011,19(4):599-609
The purpose of this study was to compare the performance of two species of diatoms, Thalassiosira weissflogii and Chaetoceros gracilis, in the larviculture of the black tiger shrimp Penaeus monodon. Shrimp larvae were fed with either C. gracilis, T. weissflogii, or a combination of the two species of diatoms. The larvae fed solely with T. weissflogii or a combination of the two types of diatom had significantly higher survival rates and faster metamorphosis than those fed
solely with C. gracilis. The numbers of diatom cells consumed by larvae during 3-h periods were determined, revealing that larvae consumed significantly
higher numbers of C. gracilis than T. weissflogii. However, when the protein, total fatty acid, and polyunsaturated fatty acid content of the two species of diatom are compared,
significantly higher amounts of each are found in T. weissflogii. Converting the number of diatom cells consumed into equivalent protein, total fatty acid, eicosopentaenoic acid, and decosahexaenoic
acid reveals that larvae fed with T. weissflogii received significantly higher amounts of all the nutrients, compared to those consuming C. gracilis. The results showed an advantage of feeding T. weissflogii to C. gracilis in enhancing survival and metamorphosis in P. monodon larvae. 相似文献
9.
Peter R. Gildemacher Elmar Schulte-Geldermann Dinah Borus Paul Demo Peter Kinyae Pauline Mundia Paul C. Struik 《Potato Research》2011,54(3):253-266
In Kenya, seed potato quality is often a major yield constraint in potato production as smallholder farmers use farm-saved
seed without proper management of seed-borne pests and diseases. Farm-saved seed is therefore often highly degenerated. We
carried out on-farm research to assess whether farmer-managed positive seed selection could improve yield. Positive selection
gave an average yield increase in farmer-managed trials of 34%, corresponding to a 284-€ increase in profit per hectare at
an additional production cost of only 6 €/ha. Positive selection can be an important alternative and complementary technology
to regular seed replacement, especially in the context of imperfect rural economies characterized by high risks of production
and insecure markets. It does not require cash investments and is thus accessible for all potato producers. It can also be
applied where access to high-quality seed is not guaranteed. The technology is also suitable for landraces and not recognized
cultivars that cannot be multiplied formally. Finally, the technology fits seamlessly within the seed systems of Sub-Saharan
Africa, which are dominated by self-supply and neighbour supply of seed potatoes. 相似文献
10.
Burak K. Pekin Matthias M. Boer Craig Macfarlane Pauline F. Grierson 《Forest Ecology and Management》2009
Water stress and fire disturbance can directly impact stand structure, biomass and composition by causing mortality and influencing competitive interactions among trees. However, open eucalypt forests of southwest Australia are highly resilient to fire and drought and may respond differently to increased fire frequency and aridity than forests dominated by non-eucalypt species. We measured the variation in stem density, basal area, stand biomass, sapwood area, leaf area and litterfall across 16 mixed jarrah (Eucalyptus marginata) and marri (Corymbia calophylla) forest stands along an aridity gradient in southwest Australia that had variable fire histories. Fire frequency was defined as the total number of fires over a ∼30-year period and aridity as the ratio of potential evapotranspiration to annual precipitation. Total stand biomass and sapwood area were predicted from diameter at breast height of individual jarrah and marri trees using allometric equations. Leaf area was estimated using digital cover photography. More arid and frequently burnt stands had higher stem density, especially of smaller trees, which were mainly jarrah. Overall, both standing biomass and leaf area decreased at more arid sites, while sapwood area was largely unaffected by aridity, suggesting that these stands respond to increased water limitation by decreasing their leaf area relative to their sapwood area. Biomass of marri was reduced at more arid and, to a lesser extent, at more frequently burnt stands. However, total stand biomass (jarrah and marri) and leaf area index did not vary with fire frequency, suggesting that less marri biomass (due to slower growth rates, higher mortality or less recruitment) was compensated by an increase in the density of jarrah trees (regeneration). We conclude that increased fire and drought shift tree species composition towards more fire-resistant species and result in denser stands of smaller trees. In contrast, total stand biomass declines with increasing aridity, but has no association with fire frequency. 相似文献