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21.
Brain tissues of 716 slaughtered domestic chickens (524 broilers and 192 hens) were bioassayed for viable toxoplasms. Each tissue was homogenized and subcutaneously injected into 4 SPF mice. Six weeks later the mice were euthanatized and their brains microscopically examined for Toxoplasma gondii tissue cysts. Three (0.4%) out of a total of 716 birds were positive. All positive cases were hens. This is the first isolation of T. gondii from chickens in Croatia. 相似文献
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The riverscape perspective recognizes the heterogeneous habitat types within the stream corridor as a single, integrated ecological
unit operating across spatial scales. Although there is ample evidence that the riverscape notion is appropriate in understanding
the physical phenomena of stream corridors, significantly less attention has focused on its ecological ramifications. To this
end, we surveyed riverscape habitat variables and bird community characteristics in the Champlain Valley of Vermont, USA.
From the data collected, we used information theoretic methodology (AICc) to model relationships between bird community attributes and key habitat variables across the riverscape. Our models with
the greatest support suggest that riverine bird communities respond to a suite of characteristics; representing a variety
of riverscape habitats at the in-stream, floodplain, and riparian levels. Channel slope, drainage area, percent conifers,
and in-stream habitat condition were among the most influential variables. We found that piscivores are potentially important
indicators of riverscape condition, responding to a host of variables across the riverscape. Our results endorse a holistic
approach to assessing and managing the mosaic of patches in the riverscape and suggest that a riverscape approach has significant
conservation potential. 相似文献
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To study the bark beetle attacks on Turkish fir stands and to determine the principle site and stand factors influencing beetle
attacks, trap log method was used in the Western Black Sea Region of Turkey. The study was carried out in ten different locations
prior to flying time in February 2003. On each experimental plot, three healthy fir trees with 30–50 cm diameter and 200 m
apart were cut down with a chainsaw. From each sampling tree, needles were sub-sampled for determination of specific leaf-area
and macro-nutrient concentrations. In addition, on each experimental plot, crown closure, basal-area, and stand density were
measured. To determine the bulk density and nutrient concentrations of the soil, samples were taken around trees on each plot.
The relationship between measured stand variables, the number of beetle species and beetle populations were evaluated using
correlation and stepwise multiple regression procedure. Eight different species belonging to four different families from
Coleoptera were identified in examining the trap logs. Six of these eight species (Pissodes piceae Illig., Pissodes notatus Fabr., Cryphalus piceae Ratz., Pityophthorus pityographus Ratz., Xyloterus lineatus Oliv., Pityokteines curvidens Germ.) were identified as harmful beetles (HB). The other two (Thanasimus formicarius L. and Rhizophagus dispar Payk.) were identified as predator species. The analysis showed that the total number of HB increased as the site’s slope
and needle specific leaf area increased. However, as needle N concentrations increased, HB population decreased. Increased
Ca concentration in fir needle reduced total insect attack. 相似文献
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This study focuses on the problem of irregular diameter structure in a silver fir–beech selection (plenter) forest with a “surplus” of large diameter trees and a lack of natural regeneration and small diameter trees. We sampled 274 plots (900 m2 each) in the Belevine research site (266.24 ha) in the mountain region Gorski Kotar (Croatia), where diameter (dbh) distribution, diameter increment, and natural regeneration were analyzed in detail. A low density of natural regeneration, weak annual recruitment of small (10 cm dbh) diameter trees (only five trees per hectare), delayed diameter growth of trees, and a low annual rate of trees reaching the next dbh class were attributed to the current irregular dbh structure. The stand development prediction for the next 50 years is based on a simulation model, which considers the current diameter structure, increment, recruitment, and future cutting regime. Intensive cutting in the first of five 10-year cutting cycles (intensity higher of 25%) is needed to initiate natural regeneration and to accelerate growth of young silver fir trees. In the next 50 years, the irregular diameter structure will be gradually improved. 相似文献
30.
E. Rakhshani A. A. Talebi N. G. Kavallieratos A. Rezwani S. Manzari Željko Tomanović 《Journal of pest science》2005,78(4):193-198
The parasitoids (Hymenoptera, Braconidae, Aphidiinae) of the cowpea aphid, Aphis craccivora Koch, were investigated throughout two far distant provinces, Tehran and Sistan-Baluchestan. Colonies of the cowpea aphid
were collected from different host plants and reared under laboratory conditions until the parasitoids emerged. The aphids
were parasitized by an expected range of parasitoids. The species were Aphidius colemani Viereck, Lysiphlebus fabarum (Marshall), Lysiphlebus confusus Tremblay and Eady, Lysiphlebus testaceipes (Cresson), Binodoxys acalephae (Marshall), Binodoxys angelicae (Haliday), Praon volucre (Haliday) and Ephedrus persicae Froggatt. L. testaceipes is reported here for the first time in Iran. The most common species was L. fabarum followed by B. acalephae and L. confusus. A key is provided for identification and host plant associations are considered. 相似文献