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《Scandinavian Journal of Forest Research》2012,27(1-4):195-204
A dynamic model of branch length and weight growth was developed for two contrasting sites, both with young stands of spruce. At one site sample trees were obtained from both unfertilised plots and from plots with increased growth rate maintained by annual fertilisation. At the second site unfertilised trees and trees subject to single applications of fertiliser were modelled. A model of the same structure was developed for each site and tested by application at the alternate site. In view of the close agreement between sites, model parameters were calculated based on all data combined. The model is driven by height increment and branch age. The sample trees were mostly open grown so that only a tentative estimate of the effects of between tree competition is given. The limitations of the model are stressed. 相似文献
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Gabrie A Detilleux J Jolly S Reginster J-Y Collin B Dessy-Doizé C 《Veterinary research communications》1999,23(1):15-40
Navicular bones from the four limbs of 95 horses, classified in 9 categories, were studied. The effects of age on navicular bone morphometry and histomorphometry were estimated, after adjustment of the data to even out the effects of front and rear limbs, morphometrical type, sex, weight, and size.All the external measurements of the navicular bone decreased significantly with increasing age. From the histomorphometrical data, cortical bone volume decreased with age in most horses, whereas cancellous bone volume and, in particular, the marrow spaces increased. The increase in the cancellous bone volume could have resulted from tunnelling of the internal part of the cortex, which converted it progressively into a porous trabecular-like structure. Trabecular bone volume also decreased with age and the trabecular lattice changed dramatically to become disconnected in aged horses. These observations corresponded closely to those reported for ageing of the skeletal system in humans.However, in sporting horses, the navicular cortical bone volume increased with age and the cancellous bone volume decreased. Exercise appeared to have decreased bone resorption and increased bone formation at the endocortical junction. The cancellous bone architecture was also improved, in that the trabecular lattice and trabecular bone volume remained unchanged in aged sporting horses. Our findings confirmed that exercise may be good practice to prevent age-related bone loss. 相似文献
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浅议园林道路的景观设计 总被引:2,自引:0,他引:2
道路在风景园林中起到组织交通、引导游览、分割空间、联系景点和构成园景的多功能作用.从园林道路的线形、材料、色彩、铺装图案和园林道路与山、水、植物、园林小品的布局等多个角度探讨了其景观设计原则. 相似文献
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《Scandinavian Journal of Forest Research》2012,27(4):373-385
Abstract Methods for small area estimations were compared for estimating the proportion of forest and growing stock volume of temperate mixed forests within a district of a member state (canton) in Switzerland. The estimators combine terrestrial data with remotely sensed auxiliary data. By using different model types, different sources of auxiliary data and different methods of processing the auxiliary data, the increase in estimation precision was tested. Using the canopy height derived from remote sensing data, the growing stock volume and the proportion of forest were estimated. The regression models used for the small area estimation provided a coefficient of determination of up to 68% for the timber volume. The proportion of plots correctly classified into forest and non-forest plots ranged between 0.9 and 0.98. Models calibrated over forest area only resulted in a maximal coefficient of determination of 37%. Even though these coefficients indicate a moderate model quality, the use of remote sensing data clearly improved the estimation precision of both the proportion of forest and the growing stock volume. Generally, Lidar data led to slightly higher estimates compared to data from aerial photography. It was possible to reduce the variance of the estimated proportion of forest to nearly one tenth compared with the variance based on the terrestrial measurements alone. Similarly, the variance of the growing stock volume could be reduced to one fourth as compared with the variance based solely on the terrestrial measurements. 相似文献
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探讨工业建筑设计的发展趋势 总被引:2,自引:0,他引:2
在新形势下工业建筑设计发生了很大的本质变化,展望目前工业建筑设计特点,结合工程探讨了工业建筑设计的实践几大发展新趋势。 相似文献
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Plants display an array of classical strategies to maximize phosphate (Pi) acquisition from sparingly soluble P sources. Acclimation to Pi-stress via elegant Pi-starvation induced (PSI) adjustments would reduce our current overreliance on expensive, polluting and non-renewable Pi-fertilizers. Nevertheless, differences in the ability of various species to solubilize sparingly soluble P-sources have been often evidenced; inter-cultivar variations are scarcely documented. Brassica is known as an effective, non-mycorrhizal user of sparingly soluble P-sources. Various growth parameters and biomass accumulation by genetically diverse Brassica cultivars were determined in four experiments using hydroponics and quartz sand culture media. Role of PSI root mediated pH changes, organic anions (OAs) exudation and altered root architecture in mobilization and acquisition of sparingly soluble P-forms [Jordan rock-P (RP) at 2 g l−1 and Ca3(PO4)2 (TCP) at 0.2 g l−1 respectively] was investigated. Cultivars showed considerable genetic variations in biomass accumulation, various growth parameters and root–shoot ratio. Concentration and total uptake of P, specific absorption rate of P, P-transport rate and P-utilization efficiency (PUE) were also significantly (P < 0.001) different for various cultivars and their dry matter was significantly correlated with P-uptake [r = 0.94** (significant at 1% level)]. P-tolerant cultivars showed substantial decrease in solution media pH because of H+ efflux and exuded more carboxylates than low P-sensitive cultivars under P-starvation. P-uptake by cultivars increased linearly with decreasing pH. The amount and types of OAs exuded from the roots of P-starved plants differed from those of plants grown under P-sufficient environment. In split pot study, with TCP and RP supplied spatially separated from other nutrients, efficient cultivars were still able to mobilize RP and TCP more efficiently than inefficient cultivars. In rhizobox study, the elongation rates of primary roots decreased but the elongation rates of the branched zones of primary roots and the length of lateral roots increased under P-starvation. Tested cultivars showed genetic diversity in accessing, mobilization, acquisition and utilization of Pi from sparingly soluble P forms. An arrange marriage of plant traits can explain cultivar’s access to different forms of sparingly soluble P, and in addition to altered lateral root topology and enhanced P-uptake and PUE, enhanced H+ efflux and OAs exudation are key factors in Pi scavenging from extra cellular sparingly soluble P-forms. 相似文献
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