全文获取类型
收费全文 | 515篇 |
免费 | 22篇 |
国内免费 | 1篇 |
专业分类
林业 | 58篇 |
农学 | 11篇 |
基础科学 | 3篇 |
177篇 | |
综合类 | 47篇 |
农作物 | 18篇 |
水产渔业 | 48篇 |
畜牧兽医 | 127篇 |
园艺 | 19篇 |
植物保护 | 30篇 |
出版年
2023年 | 5篇 |
2022年 | 5篇 |
2021年 | 3篇 |
2020年 | 13篇 |
2019年 | 12篇 |
2018年 | 10篇 |
2017年 | 14篇 |
2016年 | 12篇 |
2015年 | 12篇 |
2014年 | 18篇 |
2013年 | 36篇 |
2012年 | 33篇 |
2011年 | 34篇 |
2010年 | 25篇 |
2009年 | 15篇 |
2008年 | 38篇 |
2007年 | 33篇 |
2006年 | 24篇 |
2005年 | 34篇 |
2004年 | 27篇 |
2003年 | 30篇 |
2002年 | 15篇 |
2001年 | 16篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 1篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1976年 | 3篇 |
1975年 | 5篇 |
1972年 | 1篇 |
1969年 | 3篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1966年 | 2篇 |
1965年 | 3篇 |
1964年 | 2篇 |
1963年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有538条查询结果,搜索用时 46 毫秒
1.
Uptake of I131-labelled triiodothyronine by erythrocytes (EU test) as a test of thyroid function has been studied in cattle. The normal EU value for 141 Swedish Red-and-white cows was 6.99 ± 0.95 (range 4.45–10.23) at an incubation time of one hour. Statistically significantly higher values were obtained for newly-calved cows. The EU values for calves are significantly higher but by 12 to 18 months of age decline to the same level as for older cows.The principle of the test is described and the results obtained compared with those for human beings. The EU test is suitable for screening thyroid function for large groups of animals and for studying associations between thyroid activity and different production qualities. 相似文献
2.
Robert J. Diaz Lars Johan Hansson Rutger Rosenberg Paul C. Gapcynski Michael A. Unger 《Water, air, and soil pollution》1993,66(3-4):251-266
It is possible to rapidly detect the presence of high concentrations of sediment associated hydrocarbons using a sediment profile camera and simultaneously evaluate the general sedimentological and biological character of a contaminated area. In sediments that were heavily contaminated with hydrocarbons from spills and chronic long-term additions the presence of hydrocarbons was seen about 50% of the time in the sediment profile images as unique features, ‘H spots’. The presence of these features was related to the concentration of hydrocarbons in the sediment. In highly contaminated muddy sediments ‘H spots’ were found in images collected at stations that had from 270 to 610 ppt total hydrocarbons. Sedimentological and biological information obtained from the sediment profile images confirmed the impacted nature of Elizabeth River sediments. Sediment profile imaging provide a means of obtaining an overall evaluation of the quality of a habitat and impacts on that habitat from pollution related environmental disturbances. While qualitative, an advantage of sediment profile image data is that they can be evaluated in less than a day and used to quickly locate inclusions of hydrocarbons in the sediments for further quantitative chemical or biological sampling, or mapping of heavily contaminated areas. 相似文献
3.
The objective of this experiment was to evaluate the effect of feeding different levels of enset corm as a supplement to sheep fed Rhodes grass hay. Thirty local yearling rams with a mean (±SD) body weight of 16.97 (±1.13) kg were used. Six sheep were allocated to each of the five treatments in a completely randomized design. The treatments were hay ad libitum and 129 g dry matter (DM) corm (T1), 188 g DM corm (T2), 248 g DM corm (T3), 100 g DM noug (T4) cake, and hay alone (T5). One hundred grams of noug seedcake was supplemented for all treatments except T5. Total DM and organic matter (OM) intakes of sheep in T1, T2, and T3 were the highest (P?<?0.05) compared with sheep in other treatments, while sheep in T5 consumed the lowest DM and OM. The total crude protein (CP) intakes of sheep in T3 and T2 were greater (P?<?0.05) than the other treatments, while sheep in T5 consumed the lowest CP. The apparent DM and OM digestibility coefficients of T1, T2, and T3 diets were higher (P?<?0.05) compared with T5. The lowest (P?<?0.05) CP digestibility was in T5, whereas the digestibility among the supplemented groups was similar (P?>?0.05). The daily body weight gain for T1, T2, and T3 diets was greater (P?<?0.05) than that of T5. The feed conversion efficiency for T1 and T2 was higher (P?<?0.05) than T5, while T4 had an intermediate value. The highest (P?<?0.05) nitrogen retention was in sheep fed T3 diet, while the lowest was in those fed T5. It is concluded that farmers can supplement enset corm at 129 g DM/day as an alternative energy source to improve the productivity of sheep for small-scale farmers under enset-livestock production systems. 相似文献
4.
A survey was conducted between April and July 2007 to generate information on dry season feeding management and livestock
poisoning in the southern rangelands of Ethiopia. A total of 119 pastoralists were interviewed using a semi-structured questionnaire.
Moreover, additional information was obtained through informal discussions. The study revealed that pastoralists have rich
knowledge of natural resource management and utilization and employ various strategies such as migration, collection of grasses
and pods, and cutting branches to overcome feed scarcity during dry/drought periods. Migration of livestock and people to
areas with better grazing is the widely used strategy. However, the implementation of this strategy is diminishing as a result
of changes such as bush encroachment, expansion of settlements, and crop cultivation in dry-season grazing lands. The respondents
also indicated the presence of poisonous plants in the rangeland, and about 20 such plants were identified by the respondents.
Various species and classes of livestock are reported to be affected by toxic plants particularly in the dry and early rainy
seasons when feed is in short supply. A more extensive survey is required to document all poisonous plants in the rangelands
and to identify the major toxic principles in the different species. Future development interventions should consider the
prevailing constraints and potentials of the rangelands with active participation of the pastoralists. 相似文献
5.
Hazewinkel HA van den Brom WE Theyse LF Pollmeier M Hanson PD 《Research in veterinary science》2008,84(1):74-79
A randomized, placebo-controlled, four-period cross-over laboratory study involving eight dogs was conducted to confirm the effective analgesic dose of firocoxib, a selective COX-2 inhibitor, in a synovitis model of arthritis. Firocoxib was compared to vedaprofen and carprofen, and the effect, defined as a change in weight bearing measured via peak ground reaction, was evaluated at treatment dose levels. A lameness score on a five point scale was also assigned to the affected limb. Peak vertical ground reaction force was considered to be the most relevant measurement in this study. The firocoxib treatment group performed significantly better than placebo at the 3 h post-treatment time point and significantly better than placebo and carprofen at the 7 h post-treatment time point. Improvement in lameness score was also significantly better in the dogs treated with firocoxib than placebo and carprofen at both the 3 and 7 h post-treatment time points. 相似文献
6.
The entire dog population of Hanoveranian Scenthounds registered since the foundation of the kennel club Hirschmann in the year 1894 was analysed for the development of the inbreeding and relationship coefficient and the contribution of Hanoveranian Scenthound population of foreign countries. The analyses were performed using all available pedigree information. In the history, the breeding of the Hanoveranian Scenthound was difficult because of the low number of breeding dogs which was additionally reduced during World War I and II. The mean coefficient of inbreeding of the entire German population was 6.35%. From 1950 to 1990, the mean coefficient of inbreeding increased from 8.3% to 9.7%. In the birth years from 1990 to 2002, the mean coefficient of inbreeding decreased slightly to 9.2%. The rates of inbreeding decreased since 1950. For the last 8 generations the increase of the coefficients of inbreeding per generation was 0.71%. The mean degree of relationship of the entire population was 7.17%, whereby values higher than 75% were found. Gene contributions of 8 other European stud books for the Hanoveranian Scenthound could be found in the German population. Hereby, the Austrian Hanoveranian Scenthounds had the largest impact on the German population with 24.4%. The proportion of genes from the German stud book amounted to 67%. 相似文献
7.
Grell SN Tjørnehøj K Larsen LE Heegaard PM 《Veterinary immunology and immunopathology》2005,103(3-4):235-245
Bovine respiratory syncytial virus (BRSV) has been identified worldwide as an important pathogen associated with acute respiratory disease in calves. An infection model has been developed reflecting accurately the clinical course and the development of pathological signs during a natural BRSV-infection. In the experiments described in the present study, calves were infected at 13-21 weeks of age and reinfected 14 weeks later. Blood samples from the entire infection period were analysed for acute phase protein (haptoglobin) by ELISA and for expression (mRNA level in peripheral blood mononuclear cells) of the cytokines interleukin-2 (IL-2), interleukin-4 (IL-4), interleukin-6 (IL-6) and interferon-gamma (IFNgamma) by quantitative real-time reverse transcribed polymerase chain reaction (RT-PCR). IFNgamma, interleukin-6 and haptoglobin were markedly induced together with development of clinical signs in response to the first infection with BRSV. The IFNgamma response was biphasic, with an early peak at day 1-3 post infection (p.i.) and a later increase between day 5 and 8 p.i. Reinfection also resulted in an induction of IFNgamma, but without induction of clinical signs, IL-6 and haptoglobin. These results indicate that early mediators connected with the innate responses are induced on a first encounter with the pathogen, but not on a second encounter (reinfection) where the adaptive immune system may act as the first line defence. 相似文献
8.
9.
10.
Bergadano A Andersen OK Arendt-Nielsen L Theurillat R Thormann W Spadavecchia C 《Veterinary journal (London, England : 1997)》2009,182(2):252-260
This study quantitatively investigated the analgesic action of a low-dose constant-rate-infusion (CRI) of racemic ketamine (as a 0.5 mg kg−1 bolus and at a dose rate of 10 μg kg−1 min−1) in conscious dogs using a nociceptive withdrawal reflex (NWR) and with enantioselective measurement of plasma levels of ketamine and norketamine. Withdrawal reflexes evoked by transcutaneous single and repeated electrical stimulation (10 pulses, 5 Hz) of the digital plantar nerve were recorded from the biceps femoris muscle using surface electromyography.Ketamine did not affect NWR thresholds or the recruitment curves after a single nociceptive stimulation. Temporal summation (as evaluated by repeated stimuli) and the evoked behavioural response scores were however reduced compared to baseline demonstrating the antinociceptive activity of ketamine correlated with the peak plasma concentrations. Thereafter the plasma levels at pseudo-steady-state did not modulate temporal summation. Based on these experimental findings low-dose ketamine CRI cannot be recommended for use as a sole analgesic in the dog. 相似文献