全文获取类型
收费全文 | 104篇 |
免费 | 6篇 |
专业分类
林业 | 2篇 |
9篇 | |
综合类 | 11篇 |
农作物 | 4篇 |
水产渔业 | 5篇 |
畜牧兽医 | 72篇 |
植物保护 | 7篇 |
出版年
2021年 | 1篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2015年 | 2篇 |
2014年 | 2篇 |
2013年 | 12篇 |
2012年 | 3篇 |
2011年 | 2篇 |
2010年 | 4篇 |
2009年 | 1篇 |
2008年 | 3篇 |
2007年 | 3篇 |
2006年 | 4篇 |
2005年 | 2篇 |
2003年 | 2篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1973年 | 3篇 |
1966年 | 1篇 |
1963年 | 1篇 |
1959年 | 1篇 |
1957年 | 5篇 |
1956年 | 1篇 |
1955年 | 1篇 |
1954年 | 2篇 |
1951年 | 1篇 |
1950年 | 1篇 |
排序方式: 共有110条查询结果,搜索用时 31 毫秒
41.
AIM: To determine the effects of liveweight (LW) and use of teaser rams prior to mating on both the mating performance and pregnancy rate of ewe hoggets. METHODS: Romney hoggets (n=841) were weighed and randomly assigned to one of two treatment groups; either exposed to seven harnessed, vasectomised (teaser) rams for 17 days prior to the breeding period (n=283); or not exposed to teaser rams (unteased, n=558). Harnessed Perendale rams were then introduced for two oestrous cycles. Using crayon marks, hoggets were identified as having been mated during the first 17 days only, during the second 17 days only, during both periods, or not mated. All mated hoggets were then scanned for pregnancy using ultrasound, 48 days after the end of the breeding period, and identified as being either non-pregnant, or as single-, twinor triplet-bearing. RESULTS: Hoggets mated in either the first 17 days only or in both the first and second 17-day periods were heavier than those mated in the second period only (p<0.001). Those mated in the first or second 17-day period only, and those mated in both periods were all heavier prior to mating than those not mated at all (p<0.001). Twin-bearing hoggets were heavier than both their single-bearing and non-pregnant counterparts (p<0.001). A greater proportion of the teased hoggets were mated in the first 17 days only compared with unteased hoggets (62.6 vs 32.1%; p<0.001). In contrast, more of the unteased hoggets were marked in the second 17-day period only (p<0.001). A greater proportion of mated, unteased hoggets were found to be non-pregnant in comparison to their teased counterparts (17.8 vs 11.2%; p=0.02). CONCLUSIONS: Heavier hoggets at breeding were more likely to be mated in the first 17 days of the breeding period and more likely to be twin-bearing. Use of teaser rams for 17 days prior to the breeding period increased the proportion of hoggets mated in the first 17 days, increased conception rates, and thus increased the proportion of pregnant hoggets. These results indicate that farmers should utilise teasers for 17 days prior to commencement of the breeding period and avoid mating hoggets that weigh below 36 kg. 相似文献
42.
Abstract AIM: To determine the effect of age and prior use of mature rams at a given ram-to-ewe ratio, and the effect of body condition on breeding performance and pregnancy rate of ewe hoggets. METHODS: Ewe hoggets (n=733) aged 7–8 months were weighed and their body condition scored, then randomly assigned to one of three treatment groups (Day 0) and joined with either four two-tooth rams (20 months of age) not used previously (n=244; Two-tooth), four mixed-aged mature rams that had not been used earlier in the season (n=244; Mature-fresh), or four mixed-aged mature rams that had been used with mature ewes immediately prior to joining with hoggets (n=245; Mature-used). The breeding period was 34 days. Ewe hoggets were identified as having been marked during the first 17 days only, during both 17-day periods, during the second 17 days only, or not marked. Hoggets were re-weighed on Day 34, and pregnancy status determined using ultrasound on Day 92. The breeding soundness of the rams was assessed on Days ?34 and ?1. RESULTS: Semen samples obtained from the rams did not differ significantly in any of the parameters measured (p>0.05). Ewe hoggets joined with Mature-fresh rams were less likely (p<0.05) to be marked in the second 17 days of breeding only than those joined with either Two-tooth or Mature-used rams. No other breeding parameters were affected by breeding group (p>0.05). Hoggets marked in the first 17 days only were heavier (p<0.05) at Day 0 than those marked in the second 17 days only or not marked. Hoggets diagnosed as twin-bearing were heavier (p<0.05) than non-pregnant or single-bearing hoggets. Those hoggets marked in the first 17 days only had a greater (p<0.05) body condition score (BCS) than those marked in the second 17 days only or not marked at all. These differences were no longer apparent after correction for liveweight (LW).Correction for LW at Day 0 or change in LW during the breeding period did not affect the results for breeding performance. CONCLUSIONS: Under the conditions of this study, two-tooth rams and mature rams that had been used previously were just as suitable as mature rams that had not been used previously for breeding with ewe hoggets. Further studies are warranted to verify this result. The re-use of rams without reducing breeding performance would reduce breeding costs and may make breeding hoggets a more viable option for farmers. The BCS of ewe hoggets affected breeding performance, and can thus be used to identify those animals most suitable for breeding. 相似文献
43.
Sensitivity of boreal forest carbon balance to soil thaw 总被引:6,自引:0,他引:6
ML Goulden SC Wofsy JW Harden SE Trumbore PM Crill ST Gower T Fries BC Daube S Fan DJ Sutton A Bazzaz JW Munger 《Science (New York, N.Y.)》1998,279(5348):214-217
We used eddy covariance; gas-exchange chambers; radiocarbon analysis; wood, moss, and soil inventories; and laboratory incubations to measure the carbon balance of a 120-year-old black spruce forest in Manitoba, Canada. The site lost 0.3 +/- 0.5 metric ton of carbon per hectare per year (ton C ha-1 year-1) from 1994 to 1997, with a gain of 0.6 +/- 0.2 ton C ha-1 year-1 in moss and wood offset by a loss of 0.8 +/- 0.5 ton C ha-1 year-1 from the soil. The soil remained frozen most of the year, and the decomposition of organic matter in the soil increased 10-fold upon thawing. The stability of the soil carbon pool ( approximately 150 tons C ha-1) appears sensitive to the depth and duration of thaw, and climatic changes that promote thaw are likely to cause a net efflux of carbon dioxide from the site. 相似文献
44.
V. E. V. ST. OMER F. K. MOHAMMAD 《Journal of veterinary pharmacology and therapeutics》1984,7(4):277-281
The effects of N-acetylcysteine (NAC) on the pharmacokinetic parameters of acetaminophen (AP) in adult female beagles were studied. Each of eight dogs received a single i.v. injection of 150 mg/kg of AP as a 5% solution in a vehicle of 40% aqueous propylene glycol at 0 h. Each of four AP-treated dogs (Group I) received an oral dose of 140 mg/kg NAC as a 20% aqueous solution at 0 h, and 70 mg/kg at 30 min and 1 h post-AP administration. Four dogs (Group II) served as controls and received isotonic saline orally. Mild signs of AP toxicosis seen in both groups within 2-3 h of AP administration including depression, weakness, recumbency and methaemoglobinaemia. Relative to Group II, treatment with NAC (Group I) enhanced the elimination of AP from the body as indicated by the decreased plasma half-life (t1/2 = 1.06 h for Group I v. 1.78 h for Group II) and a higher elimination rate constant (beta = 0.67/h for Group I v. 0.40/h for Group II). Changes in the area under plasma concentration curve data (AUC = 0.39 mg.h/ml for Group I v. 0.65 mg.h/ml for Group II) were associated with a 61% increase in total body clearance of AP in Group I. The apparent volume of drug distribution Vdarea was not affected. 相似文献
45.
46.
47.
48.
Peter Cookson 《Arid Land Research and Management》2013,27(2):155-169
The inhibition of soil urease activity by the accumulation of soluble salts in a coastal region of the Sultanate of Oman susceptible to salinization was investigated . Soil transects around six individual date palms (Phoenix dactylifera L.) growing on commercially managed farms were intensively sampled and assayed for soil urease activity . Activities ranged from 0 . 10 to 39 . 85 mu g NH + 4 released g 1 soil h 1 at 37 C . Soil collected from within 70 cm of the palms h ad a higher urease activity than soil from a distance 1 . 5 m . Multiple regression analysis showed that more than 75 % of the variance in soil urease activity was accounted for by soil physi cochemical properties , except in sandy soils low in organic carbon ( C ). The soil properties most closely associated with urease activity were soil organic C , salinity , and texture . A scattergram of urease activity against salinity showed high variabil ity in activity at low salinities ( 0 . 5 dS m 1 in 1 :5 soil to water extracts ) and severe inhibition at salinity values 12 dS m 1. In nonsaline soils , variation in urease activity was closely associated with variations in organic C and clay con tents , whereas at saline conditions , only soil salinity was significantly associated with urease activity . 相似文献
49.
Background
Stomata respond to vapour pressure deficit (D) – when D increases, stomata begin to close. Closure is the result of a decline in guard cell turgor, but the link between D and turgor is poorly understood. We describe a model for stomatal responses to increasing D based upon cellular water relations. The model also incorporates impacts of increasing levels of water stress upon stomatal responses to increasing D. 相似文献50.