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Theileria orientalis (also known historically as T. sergenti and T. buffeli) is responsible for benign or non-transforming theileriosis, and exerts its major effect through erythrocyte destruction. The life cycle of T. orientalis is essentially similar to that of other Theileria species, except that the schizonts do not induce transformation and fatal lymphoproliferation. The pathogenesis of anaemia as a result of infection is not clearly established and may be multifaceted. Clinical signs of weakness, reluctance to walk and abortion are early but non-specific indications of disease, particularly if accompanied by a history of cattle being moved. Physical examination may reveal pallor (pale eyes, vaginal mucosa), pyrexia, and elevated heart and respiratory rates. T. orientalis is an economically important parasite of cattle in New Zealand, Australia and Japan, especially where naïve animals are introduced into an endemic area or in animals under stress. Increased awareness of the risks posed by the parasite is required to enable management practices to be implemented to minimise its impact.  相似文献   
3.
Objective To compare the efficacy of the non-steroidal antiinflammatory drugs, diclofenac sodium and flunixin meglumine as adjuncts to the antibiotic treatment of bovine respiratory disease (BRD). Procedure We randomly allocated 80 Holstein calves with BRD to three groups. All the calves received a dose of 2.5 mg/kg tulathromycin by single subcutaneous injection and two of the groups received, in addition, either 2.5 mg/kg diclofenac sodium as a single intramuscular injection (diclofenac group, n = 30) or 2.2 mg/kg flunixin meglumine as an intravenous injection on the first three consecutive days after tulathromycin administration (flunixin group, n = 30). All calves were given a clinical score prior to initial treatment (day 0) and after treatment (days 1, 2, 3, 7 and 14) by observing appetite, demeanour, rectal temperature, the rate and type of respiration, presence or absence of coughing, and nasal discharge. Results During the first 48 h, improvement of adverse signs of respiratory disease, such as pyrexia and elevated respiratory rate, and of a high clinical index score was significant in the two adjunct groups compared with the calves receiving antibiotic alone. The reduction in pyrexia was greatest in the diclofenac group. There were no statically significant differences between treatment groups with regard to eventual perceived recovery from respiratory disease in 14 days. Conclusion In this trial, a single intramuscular dose of diclofenac sodium was equally effective as three intravenous injections of flunixin meglumine given on consecutive days as adjunctive therapy for BRD.  相似文献   
4.
The biotopes occupied by pedunculate oak (Quercus robur L.)and rebollo oak (Quercus pyrenaica Willd.) in Galicia were characterizedusing different parameters, enabling a comparative analysisof its habitats. Thirty-nine plots of pedunculate oak and 40of rebollo oak were inventoried and 25 ecological parameters(physiographic, climatic and edaphic) were measured to describethe biotopes, along with 14 stand parameters to characterizethe structure and the silviculture of these forests; some ofthem were used in previous works about the autecology of bothspecies. Quercus robur was found to occupy a wider range ofecological habitats and their distribution is oceanic; Q. pyrenaicapresents a more Mediterranean phytoclimatic position. The resultsindicated that the distribution of oak forests in Galicia ismore closely related to physiographic and climatic featuresthan to edaphic, because the nature of the substrates that theyoccupy is similar. Analysis of fragility/aggressiveness betweenboth species and chestnut shows that the aggressiveness of bothoaks, mainly pedunculate, was much higher, except at high altitudes,and in areas with a high mean temperature, where rebollo ismore aggressiveness. Comparison of the two Quercus shows formost of the parameters that Q. robur is the more aggressivespecies.  相似文献   
5.
The aetiological agents of the abdominal swelling affecting farmed larvae of gilt-head seabream, Sparus aurata L., were studied. Four Vibrio strains were isolated from larvae of S. aurata affected by this disease, and all strains reproduced the disease in healthy larvae under controlled infection experiments, producing a significant increase of the mortality rates compared to the control (non-inoculated larvae). Several enzymatic properties, which can act as .virulence factors, were demonstrated both in the extracellular products (ECPs) and In live cells of the strains tested. Histopathological examinations of the infected fish larvae revealed important changes of the anterior intestine and liver characterized by a marked hyperthrophy of the intestinal epithelium and hepatocytes, and by a separation of the mucosal and submucosal layers in the digestive tube. These histological alterations were associated with the constant presence of cocobacillar bacteria in the anterior intestine and in the liver. However, the precise pathogenic mechanisms of the strains tested have not been completely elucidated yet.  相似文献   
6.
The determination of optimum crop management practices for increasing soybean production can provide valuable information for strategic planning in the tropics. However, this process is time consuming and expensive. The use of a dynamic crop simulation model can be an alternative option to help estimate yield levels under various growing conditions. The objectives of this study were to evaluate the performance of the Cropping System Model (CSM)‐CROPGRO‐Soybean and to determine optimum management practices for soybean for growing conditions in the Phu Pha Man district, Thailand. Data from two soybean experiments that were conducted in 1991 at Chiang Mai University and in 2003 at Khon Kaen University were used to determine the cultivar coefficients for the cultivars CM 60 and SJ 5. The CSM‐CROPGRO‐Soybean model was evaluated with data from two experiments that were conducted at Chiang Mai University. The observed data sets from farmers’ fields located in the Phu Pha Man district were also used for model evaluation. Simulations for different management scenarios were conducted with soil property information for seven different soil series and historical weather data for the period 1972–2003 to predict the optimum crop management practices for soybean production in the Phu Pha Man district. The results of this study indicated that the cultivar coefficients of the two soybean cultivars resulted in simulated growth and development parameters that were in good agreement with almost all observed parameters. Model evaluation showed a good agreement between simulated and observed data for phenology and growth of soybean, and demonstrated the potential of the CSM‐CROPGRO‐Soybean model to simulate growth and yield for local environments, including farmers’ fields, in Thailand. The CSM‐CROPGRO‐Soybean simulations indicated that the optimum planting dates from June 15 to July 15 produced maximum soybean yield in a rainfed environment. However, the planting date December 15 produced the highest yield under quality irrigation. Soybean yield was slightly improved by applying nitrogen at a rate of 30 kg N ha?1 at planting. Soybean yield also improved when the plant density was increased from 20 to 40 plants m?2. The results from this study suggest that the CSM‐CROPGRO‐Soybean model can be a valuable tool in assisting with determining optimum management practices for soybean cropping systems in the Phu Pha Man district and might be applicable to other agricultural production areas in Thailand and southeast Asia.  相似文献   
7.
Summary Linkage among loci controlling various morphological traits in cowpea were determined using F2 progenies. Data were collected on individual plants of four crosses segregating for several loci. Recombination estimates between the following pairs of loci were as follows: Sw (swollen vs normal stem base)-Fbc (cream vs green flower buds) (41±4.8%), Pus(purple vs green stems)-Cbr (cocoa-brown vs straw-yellow dry pods) (31±5.7%), Pup(purple vs green immature pods)-Cbr (30±5.7%), Pus-Pup (4±1.5%), Ndt (non-determinate vs determinate)-Pd (peduncle colour) (26±2.8%), Ndt-Hg (semi-erect vs erect plant type) (26±2.8%), Pt(purple vs green pod tips)-Bk (greyish-black vs straw-yellow dry pods) (19±2.4%) and Hg-Bpd (normal vs branching peduncle (24±9.5%). Four linkage groups (LG) were identified in these studies. The proposed LG I contained loci Sw and Fbc; LG II loci Pus, Pup, and Cbr; LG III loci Pd, Ndt, Gh, and Bpd; and LG IV loci Ptand Bk.  相似文献   
8.
Even though conservation tillage may be ideal for the semi-arid tropics (SAT) in view of results from studies and tillage practices in the U.S.A. and Australia, studies conducted in semi-arid regions of Africa appear to support the use of conventional tillage systems. Some of the reasons for this apparent discrepancy are because of the physical properties of the soils in semi-arid Africa, particularly the Sahelian zones where the soils are sandy, have high bulk densities and therefore low total porosities and form crusts upon wetting and drying. Consequently, no-till or reduced tillage systems that do not have the soil surface covered by residue in irder to prevent formation of crust as a result of raindrop impact, tend to lose water through runoff in a region where water economy is essential. Also, because these soils have inherently high bulk densities, conventional tillage systems appear to be suitable since they increase the macropores, reduce both bulk density and strength and thus ensure prolific root distribution and the resultant exploration of water and nutrients at greater soil depths. Notwithstanding, it seems that since most of the SAT soils are structurally unstable, further conventional tillage even though it has ephemeral advantages, may in the long term be exacerbating the problems of structural instability and their deleterious effect on water and soil conservation and therefore on crop production. We suggest that at this stage soil tillage research in the semi-arid regions of Africa and Asia should re-examine some of the concepts of conservation tillage in relation to soil physical properties and processes in order to obtain a tillage system that ensures high crop yields without destruction of the soil resource.  相似文献   
9.
This paper describes a pilot investigation dealing with changes in chemical composition of wood in pollution-stressed white pine trees, taken from two forested ecosystems of Southern Ontario, Canada. The implications of this research lie in a much needed search for a potential bloindicator of a pre-decline, incipient-stress induced (and/or contributed by) the air-pollutants.  相似文献   
10.
A long-term soil fertility experiment (1988-1999) at the Regional Agricultural Research Station, Bhairhawa, Nepal, was analysed to determine: (1) how long the yields of rice (Oryza sativa L.) and wheat (Triticum aestivum L.) can be sustained without K but with N and N+P (NP) applied with or without farmyard manure (FYM) and green manure, and (2) the impact of K application on yields. Starting from the 1995 wheat season, the experiment was modified to accommodate K at 0, 42, and 84 kg ha-1 in plots receiving NP to study the response of rice and wheat to K. Both rice and wheat responded to K application but the response of wheat was substantially higher, indicating that the availability of native K may have been lower in wheat. Rice yields were lower in treatments without P than with P, and yields declined significantly (0.11-0.20 Mg ha-1 year-1) in all the treatments except in NP and NP+FYM. Wheat yield was more adversely affected than rice yield when P and K were not applied. In addition, wheat yields were low (average 0.5-2.1 Mg ha-1 in various treatments). Wheat yields declined (0.08-0.12 Mg ha-1 year-1) in all but FYM treatments indicating the role of FYM in sustaining yields. The interaction of K deficiency with Helminthosporium leaf blight (spot blotch and tan spot) is also suggested as one of the factors limiting wheat yields. The estimated K balance in soil was highly negative. Results suggest that farmers should apply adequate amount of K for higher and sustainable rice and wheat yields.  相似文献   
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