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The herbicide, hexazinone, was applied four ways over ponderosa pine, 2–0 seedlings planted in northeast Oregon. The four treatments were two broadcast applications, a single broadcast application, a large spot application, and a small spot application. Seedling survival and growth were monitored for five growing seasons. Results indicate that survival more than doubled with either large or small spot applications compared to no application, and either one or two broadcast applications can increase survival an additional 30% over spot applications. Differences in stem volume were substantial, with two broadcast applications yielding more than twice the volume of a single broadcast treatment and more than five times the volume of seedlings treated with spot applications. Trees in small spots were still three times bigger than surviving seedlings in the control. These results are consistent with the concept of competition threshold. Management implications were considered in terms of cost of established seedlings. Although broadcast applications cost more per acre than spot applications, gains in seedling survival, growth and quality offset the additional cost and translate into lower established seedling costs. The cost effectiveness of broadcast applications also may be seen in the elimination of replanting or in-planting requirements and increases in long-term growth potential of the established trees.  相似文献   
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Patterns of morphological diversity were examined in Lupinus pilosus in relation to geographical origins or selection history of accessions. There was significant variation among accessions for most architectural and reproductive characters in a field experiment in Perth, Western Australia. Late flowering was associated with resetted early growth, profuse branching and collection in higher rainfall sites. High yield and profuse podding on the main stem was associated with large pods and leaves, many seeds per pod, greater height to the first main-stem pod, and collection in higher altitude sites. Ten groups of accessions, identified by hierarchical cluster analysis, accounted for 79% of genotype and 69% of genotype x character sums of squares. One group, possibly taxonomically distinct from the others, consisted exclusively of wild types from northern Israel with poor pod set and low seed yield, poor nodulation, pale foliage, and small leaves. Wild types from Turkey and Crete had rosetted early growth and were late flowering, and the Turkish group had extremely rapid mid-season growth. Ornamental types from Europe or Australia with pink, purple or white flowers clustered together in an early flowering group with vigorous early growth. A smooth-seeded type of L. pilosus was discovered in a group of short, late flowering and rough-seeded types from Syria.  相似文献   
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Freshwater species and ecosystems are gravely imperiled, particularly within urban landscapes of tropical Asia. In one of the region’s most urbanized landscapes (i.e., Singapore), we determined: (1) the importance of six different habitats (i.e., catchment reservoirs, estuarine reservoirs, forest streams, rural streams, ponds and monsoon canals) for conserving the diversity of freshwater molluscs; (2) key environmental factors (e.g., pH) affecting molluscan distribution; (3) important biogeographical determinants (e.g., area) of molluscan richness within each habitat; and (4) the habitat affinities of introduced species. High sampling saturation was achieved at most study habitats with minimal sampling effort, suggesting that the utilization of molluscs as bioindicators can expedite freshwater conservation initiatives. Estuarine reservoirs (6.0 ± 2.0) had the highest molluscan richness, vis-à-vis catchment reservoirs, forest streams, rural streams, ponds and monsoon canals (3.0 ± 1.5; 0; 3.3 ± 2.0; 1.8 ± 0.5 and 3.5 ± 0.5 respectively). Both reservoir types possessed species compositions distinct from other habitats and contained majority (76%) of the sampled species. Reservoirs therefore serve to conserve the bulk of local freshwater malacofauna, especially if they are maintained at near-neutral pH levels (i.e., ∼7.3) and contain large substrates (i.e., rocks). Area was the best predictor of molluscan richness across all habitats, implying that larger freshwater habitats require higher conservation priorities than smaller ones. Introduced (non-native) species (e.g., Pomacea canaliculata) had high affinities for reservoirs, which are in need of monitoring to curb population expansions. The interminable growth of human settlements urgently requires a reconciliatory approach, which includes the ecologically-sound design and management of modified habitats to complement reserves in sustaining native freshwater species.  相似文献   
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The present study investigated the effects of manipulating the GABAergic system on locomotor activity in juvenile spring chinook salmon, Oncorhynchus tshawytscha. In addition, we evaluated whether the GABAergic system is important for mediating the behavioural effects of corticotropin-releasing hormone (CRH). An intracerebroventricular (ICV) injection of the GABAa agonist muscimol caused an acute and dose dependent increase in locomotor activity in juvenile spring chinook salmon. ICV injections of the GABAa antagonist bicuculline prevented the increase in activity when administered concurrently with muscimol. The GABAb agonist baclofen had no effect on locomotor activity in this study. Furthermore, we found no evidence that the locomotor response to exogenous CRH was altered by the concurrent administration of muscimol or bicuculline. These results provide evidence to support the hypothesis that endogenous GABA within the central nervous system is involved in the control of locomotor activity in fish. The data also suggest that there is no interaction between the GABAergic system and CRH with regards to the control of locomotor activity in this species.  相似文献   
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Ten dogs were presented with fractures of the proximal tibial epiphysis and tuberosity. All dogs had a cranioproximal-caudodistal angulation of the tibial plateau. Six dogs had marked caudal displacement of the proximal tibial epiphysis, five of which had also sustained fractures of the proximal fibula. The estimated mean angle of inclination of the tibial plateau of affected limbs was 45.8 +/- 9.6 degrees, which was significantly greater (P<0.0005) than the estimated mean angle of the normal contralateral limb 26.2 +/- 6.6 degrees. The mean angle of inclination of the tibial plateau of dogs with fibular fractures (n=5) was not significantly different from dogs without fibular fractures (n=5) (P>0.25). Five dogs were treated conservatively and five were treated by three different methods of surgical repair. Surgically treated dogs had significantly greater preoperative tibial plateau angles (P<0.05). All dogs regained full limb usage, regardless of the method of treatment chosen.  相似文献   
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The Rose Bengal sensitised photo-oxidation of bioresmethrin (I), 2-benzylfuran-4-ylmethyl acetate (II), and 2-benzylfuran-4-ylmethanol (III) has been studied in methanol and methanol + water (1 + 1 by volume) solutions by monitoring the rate or oxygen removal from the system. The results indicate that the compounds studied are oxidised via reaction with singlet oxygen. Values for the rate constants for reaction of singlet oxygen with compounds I-III have been determined over the temperature range 293–308 K, and the energy of activation and entropy of activation for the reactions have been determined. The data have been interpreted in terms of the site of attack of singlet oxygen on the compounds.  相似文献   
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The effects of six factors, each at two levels and in all combinations, on herbage yield and weed content of perennial ( Lolium perenne ) and Italian ( L. multiflorum ) ryegrass were assessed in four autumn sowings of field plots, in 3 years and at two sites. The factors were (i) perennial (PRG) or Italian (IRG), (ii) normal or low seed rate, (iii) drilling or broadcasting the seed, (iv) normal or low N fertilizer rate, (v) ryegrass fungicide seed treatment and post-emergence insecticide sprays (F + I) or untreated, and (vi) herbicide treatment or untreated. Overall, herbage yield at the first harvest was increased by F + I and IRG (all sowings), and the higher rates of seed (three sowings) and N (two sowings). Variable results were obtained for the other two factors. Increased yield was often associated with reduced weed content. Significant interactions between factors were obtained at two sowings; in particular, F + I increased yield of IRG by 12% and 22%, but had no effect on PRG. A second harvest, in the following spring, was taken for two sowings and there was no effect of F + I or the higher rates of seed and N. Thus, it is concluded that the desired aim when establishing grass swards of an adequate plant population without excessive competition from weeds appeared to be obtained even with plots receiving the least inputs.  相似文献   
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