全文获取类型
收费全文 | 561篇 |
免费 | 44篇 |
国内免费 | 2篇 |
专业分类
林业 | 25篇 |
农学 | 14篇 |
基础科学 | 11篇 |
71篇 | |
综合类 | 62篇 |
农作物 | 21篇 |
水产渔业 | 46篇 |
畜牧兽医 | 314篇 |
园艺 | 14篇 |
植物保护 | 29篇 |
出版年
2023年 | 3篇 |
2022年 | 7篇 |
2021年 | 6篇 |
2020年 | 11篇 |
2019年 | 14篇 |
2018年 | 9篇 |
2017年 | 7篇 |
2016年 | 14篇 |
2015年 | 6篇 |
2014年 | 20篇 |
2013年 | 23篇 |
2012年 | 30篇 |
2011年 | 35篇 |
2010年 | 13篇 |
2009年 | 19篇 |
2008年 | 40篇 |
2007年 | 38篇 |
2006年 | 38篇 |
2005年 | 40篇 |
2004年 | 38篇 |
2003年 | 26篇 |
2002年 | 36篇 |
2001年 | 9篇 |
2000年 | 8篇 |
1999年 | 10篇 |
1998年 | 9篇 |
1997年 | 9篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 10篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1973年 | 4篇 |
1968年 | 2篇 |
1967年 | 3篇 |
1963年 | 2篇 |
1938年 | 2篇 |
排序方式: 共有607条查询结果,搜索用时 12 毫秒
101.
Jojoba (Simmondsia chinensis L. [Schneider]) is a wind-pollinated perennial shrub native to the Sonoran Desert. In recent years commercial plantations in Arizona and Catamarca, Argentina have dramatically decreased in size and number, going from 13,000 ha in the early 1980s to about 2,300 ha today. The main reason for this decrease is yields being lower than expected, with low pollination percentages considered the main source of the problem, although use of inferior genetic material has contributed to the problem. Artificial or supplemental pollination has been used successfully in other crops to increase yields, and it was thought that this could also be used for jojoba. A trial was carried out over two seasons in which pollen collected in Arizona, was mechanically applied to commercial fields in Catamarca. The first year yields were significantly (P < 0.05) greater in the fields in which pollen had been applied, than in the controls. The second year yields were not measured. Rather the number of capsules with fruit, aborts, and empty capsules were counted on a number of randomly selected branches. This technique gives a good estimate of yield, and the results showed that pollen application significantly (P < 0.05) increased expected yields. In conclusion, application of supplemental pollen increases jojoba yields and hence should be considered a viable option for commercial plantations. Additional work is required, however, to determine the correct application rate so as to minimize collection costs, and determine when application should take place to optimize efficacy. 相似文献
102.
特殊大豆蛋白HP300对断奶仔猪生产性能影响的研究 总被引:13,自引:0,他引:13
选用48头30日龄断奶体重约7kg的杜长大三元杂交猪。随机分到2个处理组,每个处理3个重复,每个重复8头猪,对照组日粮为玉米-豆粕型日粮,试验组日粮在有等氨基酸水平基础上用HP300替代普通豆粕,试验期21d。试验结果表明:断奶后第一周猪平均日增重以HP300组为高,176.7g/d,比豆粕组高23.14%;第2周HP300组猪的平均日增重显著高于豆粕组(P〈0.05),提高16.33%,但第3周 相似文献
103.
104.
Movement and habitat use of the freshwater catfish (Tandanus tandanus) in a remnant floodplain wetland 下载免费PDF全文
Wayne M. Koster David R. Dawson Pam Clunie Fern Hames John McKenzie Paul D. Moloney David A. Crook 《Ecology of Freshwater Fish》2015,24(3):443-455
Knowledge of the movement and habitat use of fishes is important in identifying and understanding the causes of population declines and predicting how populations are likely to respond to management interventions. In this study, radiotelemetry was used to examine the spring and summer movement and habitat use patterns of the freshwater catfish (Tandanus tandanus) in a remnant wetland to inform the development of recovery actions for this threatened species. Twenty‐one adult fish were tagged and released within Tahbilk Lagoon, Victoria, Australia, in September 2009. Fish were located every 1–2 weeks between September 2009 and February 2010, a period which coincides with the spawning period for the species. Eleven of the fish were also tracked every 2 h for 68 consecutive hours in December 2009 to examine diel movements. The study revealed that freshwater catfish make extensive use of cover (e.g. wood and macrophytes) and typically have limited ranges (median total linear range and 90% linear range 599 and 173 m respectively), although they occasionally moved more extensively (up to 1.5 km) between floodplain and riverine habitats. Fish moved over much greater areas at night compared with during the day. There was also evidence of sex‐specific variation in movement, with a trend for greater movement of female fish at night compared with males. The results of the study suggest that strategies that protect macrophyte and wood habitats and improve connectivity between riverine and floodplain habitats are likely to be important in maintaining and restoring remnant populations of this species. 相似文献
105.
Upendra M. Sainju Harry H. Schomberg Bharat P. Singh Wayne F. Whitehead P. Glynn Tillman Sharon L. Lachnicht-Weyers 《Soil & Tillage Research》2007,96(1-2):205-218
Cover crops may influence soil carbon (C) sequestration and microbial biomass and activities by providing additional residue C to soil. We examined the influence of legume [crimson clover (Trifolium incarnatum L.)], nonlegume [rye (Secale cereale L.)], blend [a mixture of legumes containing balansa clover (Trifolium michelianum Savi), hairy vetch (Vicia villosa Roth), and crimson clover], and rye + blend mixture cover crops on soil C fractions at the 0–150 mm depth from 2001 to 2003. Active fractions of soil C included potential C mineralization (PCM) and microbial biomass C (MBC) and slow fraction as soil organic C (SOC). Experiments were conducted in Dothan sandy loam (fine-loamy, kaolinitic, thermic, Plinthic Kandiudults) under dryland cotton (Gossypium hirsutum L.) in central Georgia and in Tifton loamy sand (fine-loamy, siliceous, thermic, Plinthic Kandiudults) under irrigated cotton in southern Georgia, USA. Both dryland and irrigated cotton were planted in strip tillage system where planting rows were tilled, thereby leaving the areas between rows untilled. Total aboveground cover crop and cotton C in dryland and irrigated conditions were 0.72–2.90 Mg C ha−1 greater in rye + blend than in other cover crops in 2001 but was 1.15–2.24 Mg C ha−1 greater in rye than in blend and rye + blend in 2002. In dryland cotton, PCM at 50–150 mm was greater in June 2001 and 2002 than in January 2003 but MBC at 0–150 mm was greater in January 2003 than in June 2001. In irrigated cotton, SOC at 0–150 mm was greater with rye + blend than with crimson clover and at 0–50 mm was greater in March than in December 2002. The PCM at 0–50 and 0–150 mm was greater with blend and crimson clover than with rye in April 2001 and was greater with crimson clover than with rye and rye + blend in March 2002. The MBC at 0–50 mm was greater with rye than with blend and crimson clover in April 2001 and was greater with rye, blend, and rye + blend than with crimson clover in March 2002. As a result, PCM decreased by 21–24 g CO2–C ha−1 d−1 but MBC increased by 90–224 g CO2–C ha−1 d−1 from June 2001 to January 2003 in dryland cotton. In irrigated cotton, SOC decreased by 0.1–1.1 kg C ha−1 d−1, and PCM decreased by 10 g CO2–C ha−1 d−1 with rye to 79 g CO2–C ha−1 d−1 with blend, but MBC increased by 13 g CO2–C ha−1 d−1 with blend to 120 g CO2–C ha−1 d−1 with crimson clover from April 2001 to December 2002. Soil active C fractions varied between seasons due to differences in temperature, water content, and substrate availability in dryland cotton, regardless of cover crops. In irrigated cotton, increase in crop C input with legume + nonlegume treatment increased soil C storage and microbial biomass but lower C/N ratio of legume cover crops increased C mineralization and microbial activities in the spring. 相似文献
106.
Mason DJ O'Grady M Woods JP McDonell WN 《American journal of veterinary research》2002,63(7):1048-1052
OBJECTIVES: To assess the effect of increasing serum lithium concentrations on lithium dilution cardiac output (LiDCO) determination and to determine the ability to predict the serum lithium concentration from the cumulative lithium chloride dosage. ANIMALS: 10 dogs (7 males, 3 females). PROCEDURE: Cardiac output (CO) was determined in anesthetized dogs by measuring LiDCO and thermodilution cardiac output (TDCO). The effect of the serum lithium concentration on LiDCO was assessed by observing the agreement between TDCO and LiDCO at various serum lithium concentrations. Also, cumulative lithium chloride dosage was compared with the corresponding serum lithium concentrations. RESULTS: 44 paired observations were used. The linear regression analysis for the effect of the serum lithium concentration on the agreement between TDCO and LiDCO revealed a slope of -1.530 (95% confidence interval [CI], -2.388 to -0.671) and a y-intercept of 0.011 (r2 = 0.235). The linear regression analysis for the effect of the cumulative lithium chloride dosage on the serum lithium concentration revealed a slope of 2.291 (95% CI, 2.153 to 2.429) and a y-intercept of 0.008 (r2 = 0.969). CONCLUSIONS AND CLINICAL RELEVANCE: The LiDCO measurement increased slightly as the serum lithium concentration increased. This error was not clinically relevant and was minimal at a serum lithium concentration of 0.1 mmol/L and modest at a concentration of 0.4 mmol/L. The serum lithium concentration can be reliably predicted from the cumulative lithium dosage if lithium chloride is administered often within a short period. 相似文献
107.
Curtis Plowgian Joseph M. Blondeau Matthew Levinson Wayne Rosenkrantz 《Veterinary dermatology》2019,30(6):481-e142
108.
Thomas P. Howard Brendan Fahy Fiona Leigh Phil Howell Wayne Powell Andy Greenland Kay Trafford Alison M. Smith 《Journal of Cereal Science》2014
The effects on barley starch and grain properties of four starch synthesis mutations were studied during the introgression of the mutations from diverse backgrounds into an elite variety. The lys5f (ADPglucose transporter), wax (granule-bound starch synthase), isa1 (debranching enzyme isoamylase 1) and sex6 (starch synthase IIa) mutations were introgressed into NFC Tipple to give mutant and wild-type BC2F4 families with different genomic contributions of the donor parent. Comparison of starch and grain properties between the donor parents, the BC2F4 families and NFC Tipple allowed the effects of the mutations to be distinguished from genetic background effects. The wax and sex6 mutations had marked effects on starch properties regardless of genetic background. The sex6 mutation conditioned low grain weight and starch content, but the wax mutation did not. The lys5 mutation conditioned low grain weight and starch content, but exceptionally high β-glucan contents. The isa1 mutation promotes synthesis of soluble α-glucan (phytoglycogen). Its introgression into NFC Tipple increased grain weight and total α-glucan content relative to the donor parent, but reduced the ratio of phytoglycogen to starch. This study shows that introgression of mutations into a common, commercial background provides new insights that could not be gained from the donor parent. 相似文献
109.
Long‐term environmental sustainability and community acceptance of the shrimp farming industry in Australia requires on‐going development of efficient cost‐effective effluent treatment options. In this study, we aimed to evaluate the effectiveness of a shrimp farm treatment system containing finfish and vertical artificial substrates (VAS). This was achieved by (1) quantifying the individual and collective effects of grey mullet (Mugil cephalus L.) and VASs on water and sediment quality, and (2) comparing the retention of N in treatment systems with and without the presence of finfish (M. cephalus and the siganid Siganus nebulosus (Quoy & Gaimard)), where light was selectively removed. Artificial substrates were found to significantly improve the settlement of particulate material, regardless of the presence of finfish. Mullet actively resuspended settled solids and reduced the production of nitrate when artificial substrates were absent. However, appreciable nitrification was observed when mullet were present together with artificial substrates. The total quantity of N retained by the mullet was found to be 1.8– 2.4% of the incoming pond effluent N. It was estimated that only 21% of the pond effluent N was available for mullet consumption. When S. nebulosus was added, total finfish N retention increased from 1.8% to 3.9%, N retention by mullet also improved (78±16 to 132±21‐mg N day?1 before and after siganid addition respectively). Presence of filamentous macroalgae (Enteromorpha spp.) was found to improve the removal of N from pond effluent relative to treatments where light was excluded. Denitrification was also a significant sink for N (up to 24% N removed). Despite the absence of algal productivity and greater availability of nitrate, denitrification was not higher in treatments where light was excluded. Mullet were found to have no effect on the rates of denitrification but significantly reduced macroalgal growth on the surface of the water. When mullet were absent, excessive macroalgal growth led to reduced dissolved oxygen concentrations and nitrification. This study concludes that the culture of mullet alone in shrimp farm effluent treatment systems does not result in significant retention of N but can contribute to the control of macroalgal biomass. To improve N retention and removal, further work should focus on polyculturing a range of species and also on improving denitrification. 相似文献
110.
Angela R Mays Michael L Looper Benjamin C Williamson Kenneth P Coffey Wayne K Coblentz Glen E Aiken Charles F Rosenkrans Jr 《畜牧与生物技术杂志(英文版)》2013,4(1):20