全文获取类型
收费全文 | 2186篇 |
免费 | 107篇 |
专业分类
林业 | 59篇 |
农学 | 52篇 |
基础科学 | 5篇 |
251篇 | |
综合类 | 490篇 |
农作物 | 54篇 |
水产渔业 | 98篇 |
畜牧兽医 | 1177篇 |
园艺 | 23篇 |
植物保护 | 84篇 |
出版年
2021年 | 23篇 |
2020年 | 27篇 |
2019年 | 32篇 |
2018年 | 26篇 |
2017年 | 22篇 |
2016年 | 21篇 |
2015年 | 28篇 |
2014年 | 36篇 |
2013年 | 79篇 |
2012年 | 56篇 |
2011年 | 98篇 |
2010年 | 42篇 |
2009年 | 42篇 |
2008年 | 77篇 |
2007年 | 59篇 |
2006年 | 78篇 |
2005年 | 63篇 |
2004年 | 75篇 |
2003年 | 63篇 |
2002年 | 50篇 |
2001年 | 47篇 |
2000年 | 63篇 |
1999年 | 48篇 |
1998年 | 20篇 |
1997年 | 22篇 |
1994年 | 35篇 |
1993年 | 52篇 |
1992年 | 49篇 |
1991年 | 55篇 |
1990年 | 56篇 |
1989年 | 55篇 |
1988年 | 48篇 |
1987年 | 39篇 |
1986年 | 54篇 |
1985年 | 40篇 |
1984年 | 29篇 |
1983年 | 28篇 |
1982年 | 21篇 |
1981年 | 30篇 |
1979年 | 38篇 |
1978年 | 23篇 |
1977年 | 18篇 |
1976年 | 17篇 |
1975年 | 25篇 |
1974年 | 19篇 |
1973年 | 26篇 |
1972年 | 29篇 |
1971年 | 37篇 |
1970年 | 26篇 |
1969年 | 30篇 |
排序方式: 共有2293条查询结果,搜索用时 10 毫秒
71.
Measures of maternal productivity and reproduction of Hereford (HH), Angus-Hereford (AH), 25% Simmental-75% Hereford (1S3H), 50% Simmental-50% Hereford (1S1H) and 75% Simmental-25% Hereford (3S1H) dams were studied. Half of each dam breed group was bred to Tartentaise and half to Charolais sires to produce 706 calves at weaning from 930 exposures to breeding in a Montana range environment. Data were analyzed according to a model that included the fixed effects of year, dam breed group, dam age, calf sex, calf sire breed, plus appropriate two-way interactions, linear partial regression on calf birth date and random effects of sire within dam breed group (maternal grandsire of the calf) and sire within calf sire breed. Calf sex interacted with calf sire breed for several traits, but interactions were due to changes of magnitude of differences between sexes. There were no significant interactions of dam breed group with other main effects for calf growth traits, except for the interaction with calf sire breed for some calf growth traits. This interaction was due to a change in magnitude; it suggested that larger sire breeds should be matched to larger dam breeds with greater potential for milk production. The only significant interaction for traits that included reproduction of the dam was dam breed group X age of dam. Ranking of dam breed groups depended on age at measurement. Differences among dam breed groups were significant for most traits. Calf weaning weights for HH, AH, 1S3H, 1S1H and 3S1H dams were 211, 223, 227, 237 and 243 kg, respectively; calf weaning weights per cow exposed were 157, 163, 179, 189 and 169 kg; calf weaning weights per unit of dam weight were .40, .41, .43, .44 and .42, respectively. Thus, dam breed groups that weaned the largest calves were not necessarily the most productive under Montana range conditions. 相似文献
72.
Anderson DC 《New Zealand veterinary journal》1985,33(5):61-65
Information on disease incidence and herd wastage was collected from 36 farms supplying the Rangitaiki Plains Dairy Company over a two-year period from June 1981 to May 1983. These herds contained 7050 milking cows and 1460 yearlings. Although 33.5% of calves horn were reared, only 21.7% entered the herd. The average wastage rate over the two seasons was 22.6%. This included a 2.5% death-rate. Main reasons for culling were infertility (6.3%), low production (3.7%) and mastitis (2.3%). Only 0.8% of cows died or were culled because of bloat and 0.4% from each of facial eczema and metabolic diseases. Treatments were administered by farmers or veterinarians to 18.8% of the cows for mastitis, to 3.9% for metabolic diseases and to 3.6% for lameness. In total, 34.6% of cows received treatment for disease. Wide differences were noted in the proportion of cases of different diseases for which veterinarians were consulted. These ranged from 83.6% for scours to 3.8% for mastitis. As well as confirming or quantifying the relative importance of various diseases and causes of wastage, the survey highlighted the problems in collecting reliable data from herd owners on the events in their herds. 相似文献
73.
74.
The mean serum folate concentrations of Large White sows were compared between one group of 13 animals, 43–80 days pregnant and another group of 9 animals at weaning when the litters were 28–30 days old. The mean concentration was higher in sows at weaning (p<0.05) and the lowest levels were found in sows no more than 51 days pregnant (p<0.05). 相似文献
75.
While the use of external skeletal fixation was once associated with substantial postoperative morbidity, clinical and experimental studies have led to technological advances and modifications in application techniques that have greatly improved the results obtained with this treatment modality. The past decade saw numerous advances in external skeletal fixator implants, components and instrumentation, including improvements in fixation pin design, and the development of new linear external skeletal fixation systems and economical circular external skeletal fixation systems specifically engineered for use in dogs and cats. In addition, a greater understanding of fixator biomechanics and the pathobiology of the bone-fixation pin interface have improved fixator application practices. This article reviews many of the more significant recent advances in external skeletal fixation. 相似文献
76.
77.
Segmental atresia of the transverse colon was observed at necropsy in a neonatal foal. The dorsal and ventral components of the large colon were fused, and ended blindly. The small colon was collapsed and completely closed at its cranial end. The right and left dorsal and ventral colons were fused into one blind-ended tube. Histologically, eosinophilic intranuclear inclusion bodies demonstrative of Equine Rhinopneumonitis were present in the thymus. 相似文献
78.
V J Polzin D L Anderson G B Anderson R H BonDurant J E Butler R L Pashen M C Penedo J D Rowe 《Journal of animal science》1987,65(1):325-330
Embryos were surgically flushed from goats and sheep on d 6 and 7, respectively, following the first day of estrus (d 0). After enzymatic removal of the zonae pellucidae, inner cell masses were isolated from caprine blastocysts by immunosurgery. The intact inner cell masses were injected into ovine blastocysts with the aid of a micromanipulator. Twenty-two manipulated blastocysts were surgically transferred into 12 ovine recipients. Nine ewes gave birth to a total of 13 young (59% embryo survival). Ten were classified by serum electrophoretic assays or karyotypes as lambs, one as a kid, and two as interspecific chimeras. 相似文献
79.
Stacy L Anderson Tanya Duke‐Novakovski Baljit Singh 《Veterinary anaesthesia and analgesia》2014,41(2):113-126
ObjectiveTo review the immune response to anesthesia including mechanical ventilation, inhaled anesthetic gases, and injectable anesthetics and sedatives.Study designReview.Methods and databasesMultiple literature searches were performed using PubMed and Google Scholar from spring 2012 through fall 2013. Relevant anesthetic and immune terms were used to search databases without year published or species constraints. The online database for Veterinary Anaesthesia and Analgesia and the Journal of Veterinary Emergency and Critical Care were searched by issue starting in 2000 for relevant articles.ConclusionRecent research data indicate that commonly used volatile anesthetic agents, such as isoflurane and sevoflurane, may have a protective effect on vital organs. With the lung as the target organ, protection using an appropriate anesthetic protocol may be possible during direct pulmonary insults, including mechanical ventilation, and during systemic disease processes, such as endotoxemia, generalized sepsis, and ischemia-reperfusion injury. 相似文献
80.