首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   71篇
  免费   4篇
林业   1篇
  18篇
综合类   7篇
农作物   5篇
水产渔业   14篇
畜牧兽医   29篇
园艺   1篇
  2022年   1篇
  2021年   2篇
  2020年   1篇
  2019年   2篇
  2018年   2篇
  2017年   1篇
  2016年   1篇
  2015年   2篇
  2013年   3篇
  2012年   5篇
  2011年   1篇
  2009年   4篇
  2008年   10篇
  2007年   2篇
  2006年   5篇
  2005年   4篇
  2004年   5篇
  2003年   1篇
  2002年   2篇
  2001年   3篇
  2000年   4篇
  1999年   1篇
  1998年   1篇
  1995年   1篇
  1989年   1篇
  1985年   1篇
  1983年   1篇
  1982年   1篇
  1979年   1篇
  1976年   1篇
  1971年   1篇
  1970年   1篇
  1969年   1篇
  1968年   2篇
排序方式: 共有75条查询结果,搜索用时 31 毫秒
61.
  • 1. Denison's Barb, Puntius denisonii (Day) is an endemic and endangered cyprinid fish of the Western Ghats biodiversity hotspot in peninsular India, which is the focus of an organized yet undocumented fishery targeting juveniles for the international aquarium trade.
  • 2. Research on P. denisonii has been very limited and there has been no systematic effort to assess and monitor their abundance, distribution and populations.
  • 3. Anecdotal and circumstantial evidence indicates a highly restricted distribution, low abundance, declining populations, low catch per unit effort and increasing market prices, providing evidence of an impending conservation crisis and the need for urgent management of wild stocks.
  • 4. This paper reviews current knowledge, provides results from the authors' field study and suggests priorities for conservation and management actions for P. denisonii in the streams of Kerala.
Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
62.
Hilsa, Tenualosa ilisha has received much attention for culture due to decline of the natural population. Lack of knowledge on larval rearing is the bottleneck for its culture. This study was aimed at developing larval rearing protocols for hilsa shad. Hilsa larvae (4 days old, 4.76 ± 0.06 mm/0.49 ± 0.01 mg) were stocked in fibreglass‐reinforced plastic tanks (1.7 m3 water volume) at 300, 600 and 1,200 nos/m3 in triplicates in three experimental systems viz., E‐I (circular, 0.567 m water depth), E‐II (circular, 0.962 m water depth) and E‐III (rectangular, 0.567 m water depth) and reared for 46 days. The larvae were supplied with Chlorella vulgaris, Brachionus calyciflorus, mixed phytoplankton and mixed zooplankton during 4–50, 6–25, 8–50 and 26–50 days of their age respectively. In each system, higher (p < 0.05) fry survival at 300 nos/m3 than in higher densities indicates density dependent stress. Circular tanks showed higher survival (13.3%–61.31%) than in rectangular tanks (6.88%–27.26%) in each stocking density, indicating the importance of tank shape for rearing. Water depth affected fry survival in circular tanks (E‐I and E‐II) at 300 nos/m3; at 0.962 m depth, survival was higher (61.31%, p < 0.05) than that of 0.567 m depth (49.93%). Good fry survival was achieved through feeding the larvae initially with Chlorella followed by co‐feeding with Brachionus, mixed phytoplankton and zooplankton and rearing in circular tanks at 300 nos/m3 densities at 1 m depth. This first‐ever larval rearing protocol is useful for mass production of fry to support hilsa aquaculture in future.  相似文献   
63.
Associations of land cover/land use variables and the presence of dogs in urban vs. rural address locations were evaluated retrospectively as potential risk factors for canine leptospirosis in Kansas and Nebraska using Geographic Information Systems (GIS). The sample included 94 dogs positive for leptospirosis predominantly based on a positive polymerase chain reaction test for leptospires in urine, isolation of leptospires on urine culture, a single reciprocal serum titer of 12,800 or greater, or a four-fold rise in reciprocal serum titers over a 2-4 weeks period; and 185 dogs negative for leptospirosis based on a negative polymerase chain reaction test and reciprocal serum titers less than 400. Land cover features from 2001 National Land Cover Dataset and 2001 Kansas Gap Analysis Program datasets around geocoded addresses of case/control locations were extracted using 2500m buffers, and the presence of dogs' address locations within urban vs. rural areas were estimated in GIS. Multivariate logistic models were used to determine the risk of different land cover variables and address locations to dogs. Medium intensity urban areas (OR=1.805, 95% C.I.=1.396, 2.334), urban areas in general (OR=2.021, 95% C.I.=1.360, 3.003), and having urban address locations (OR=3.732, 95% C.I.=1.935, 7.196 entire study region), were significant risk factors for canine leptospirosis. Dogs regardless of age, sex and breed that live in urban areas are at higher risk of leptospirosis and vaccination should be considered.  相似文献   
64.
A real-time, volatile-detection-assisted control system was designed for microwave drying. Detected volatile signals were integrated to a fuzzy logic algorithm to determine the drying temperature. A phase controller was used to automatically and continuously adjust the microwave power. A data acquisition unit with developed program was employed to integrate the entire control. Carrot samples were used in system tests. The results showed that the designed system could successfully achieve the desired temperature, power, and volatiles control and lead to acceptable product's quality.  相似文献   
65.
Associations of housing, population, and agriculture census variables, and presence near public places were retrospectively evaluated as potential risk factors for canine leptospirosis using Geographic Information Systems (GIS). The sample population included 94 dogs positive for leptospirosis based on a positive polymerase chain reaction test for leptospires on urine, isolation of leptospires on urine culture, a single reciprocal serum titer of 12,800 or greater, or a four-fold rise in reciprocal serum titers over a 2-4 week period; and 185 dogs negative for leptospirosis based on a negative polymerase chain reaction test and reciprocal serum titers less than 400. Multivariable logistic regressions revealed different risk factors among different census units; however, houses lacking complete plumbing facilities [OR=2.80, 95% C.I.=1.82, 4.32 (census unit, block group); OR=1.36, 95% C.I.=1.28, 1.45 (census tract); OR=3.02, 95% C.I.=2.60, 3.52 (county)]; and poverty status by age (18-64) [OR=2.04, 95% C.I.=1.74, 2.39 (block group); OR=1.53, 95% C.I.=1.41, 1.67 (census tract); and OR=1.62, 95% C.I.=1.50, 1.76 (county)] were consistent risk factors for all census units. Living within 2500m of a university/college and parks/forests were also significantly associated with leptospirosis status in dogs. Dogs that live under these circumstances are at higher risk for leptospirosis and pet owners should consider vaccination.  相似文献   
66.
67.
68.
The solar neutrino puzzle is deepening into a paradox that refutes the basic logic of the reaction chain that powers the sun by the fusion of protons into heavy elements. Experiments now reveal a serious anomaly in the relative neutrino fluxes from the different steps in the chain. Neutrinos from boron-8 at the end of the chain are seen but hardly any are seen from beryllium-7, without which the observed boron-8 cannot be made. The only apparent way to avoid a paradoxical "missing link" in the sun's energy chain is a nonzero neutrino mass, an idea that can be tested in future experiments.  相似文献   
69.
Dynamic oscillatory rheology of two wheat protein isolate (Prolite 100 and Prolite 200) doughs (≈48% moisture content, wet basis) were studied over a frequency range of 0.1–10 Hz during temperature sweep from 20 to 90 °C at a heating rate of 2 °C/min. Both doughs behaved similarly during heating; showed a threshold value and increased sharply, thereafter. Prolite 200 dough had a higher elastic modulus (G′) and lower phase angle (δ) whereas Prolite 100 showed a distinct gel point at 52.2 °C followed by significant increase up to 90 °C. Rheological data of doughs after isothermal heating at 90 °C for 15 min followed by cooling to 20 °C resulted in strong mechanical strength. However, Prolite 100 dough showed more viscoelastic characteristics with significant transformation from liquid-like to solid-like behavior after heating than Prolite 200. Thermal analysis of isolates indicated distinct endothermic peaks in wider temperature range (50–130 °C) at various moisture levels. Lower temperatures could be associated with denaturation of various fractions of proteins whereas higher temperature linked to glass transition temperature of isolates. SDS–PAGE did not show any clear distinction among protein subunits between two isolates. Dielectric measurements of isolates at frequencies from 500 to 3000 MHz and temperature range between 30 and 80 °C indicated Prolite 200 had higher dielectric constant (ε′) and loss factor (ε″) than Prolite 100. Isolates showed significant changes in dielectric properties above 50 °C indicating protein denaturation and supported rheological and calorimetric data.  相似文献   
70.
The objective of this study is to conduct a comprehensive assessment of the transport of isoxaflutole and RPA 202248 and their accumulation potential in semistatic water bodies, using a distributed watershed scale model and observed water quality data. A conceptual model was developed to characterize the fate and transport of isoxaflutole residues to and in surface water. The soil and water assessment tool (SWAT), a continuous daily time-step watershed model, was used to simulate the processes identified in the conceptual model. Monitoring data were available for a number of surface water bodies within the major product use area as a result of extensive and intensive residue monitoring. Detailed product use information at the zip-code level was obtained through dealer sales and a grower survey. The hydrologic and chemical transport results from the SWAT model were validated by comparison to available monitoring data from selected water bodies. Upon validation, the model was used to simulate the fate of isoxaflutole-derived residues in the water bodies using long-term historical weather data. The results from this investigation indicate no evidence of long-term accumulation of isoxaflutole and its metabolite RPA 202248 in semistatic water bodies.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号