全文获取类型
收费全文 | 508篇 |
免费 | 27篇 |
专业分类
林业 | 25篇 |
农学 | 9篇 |
基础科学 | 2篇 |
48篇 | |
综合类 | 148篇 |
农作物 | 10篇 |
水产渔业 | 23篇 |
畜牧兽医 | 241篇 |
园艺 | 11篇 |
植物保护 | 18篇 |
出版年
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 5篇 |
2015年 | 4篇 |
2013年 | 12篇 |
2012年 | 14篇 |
2011年 | 14篇 |
2010年 | 8篇 |
2009年 | 10篇 |
2008年 | 15篇 |
2007年 | 21篇 |
2006年 | 15篇 |
2005年 | 13篇 |
2004年 | 10篇 |
2003年 | 14篇 |
2002年 | 10篇 |
2001年 | 14篇 |
2000年 | 21篇 |
1999年 | 14篇 |
1998年 | 8篇 |
1997年 | 8篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 16篇 |
1990年 | 19篇 |
1989年 | 13篇 |
1988年 | 6篇 |
1987年 | 18篇 |
1986年 | 13篇 |
1985年 | 8篇 |
1984年 | 7篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1976年 | 9篇 |
1975年 | 8篇 |
1974年 | 7篇 |
1973年 | 4篇 |
1972年 | 5篇 |
1971年 | 9篇 |
1970年 | 7篇 |
1969年 | 6篇 |
1968年 | 5篇 |
1967年 | 11篇 |
1966年 | 6篇 |
1965年 | 4篇 |
1907年 | 3篇 |
排序方式: 共有535条查询结果,搜索用时 0 毫秒
1.
2.
Landscape metrics with ecotones: pattern under uncertainty 总被引:1,自引:0,他引:1
3.
4.
Presentation,clinical pathological and post‐mortem findings in three related Scottish terriers with ligneous membranitis 下载免费PDF全文
S. L. Mason C. Fisher L. Ressel N. X. Bommer L. M. Buckley T. Nuttall 《The Journal of small animal practice》2016,57(5):271-276
Ligneous conjunctivitis and gingivitis were diagnosed in three related Scottish terrier dogs presented for investigation of severe conjunctivitis and respiratory signs. Hypoplasminogenaemia was confirmed in one of the three affected dogs. Supportive treatment was not effective, and the dogs died or were euthanased because of the disease. Post‐mortem analysis of two of the dogs revealed multiple abnormalities including severe proliferative fibrinous lesions affecting the conjunctiva, gingiva, trachea, larynx and epicardium and multiple fibrous adhesions throughout the thoracic and abdominal cavities. One dog had internal hydrocephalus and lacked a cerebellar vermis. Ligneous membranitis was confirmed on histopathology. This is a rare condition in dogs but an important differential diagnosis for severe conjunctivitis and gingivitis. 相似文献
5.
6.
Eastern grey squirrels (Sciurus carolinensis) and North American red squirrels (Tamiasciurus hudsonicus) were studied among wooded patches within an agricultural mosaic. Fifteen sites south of Ottawa, Canada, with differing landscape and local features were censused using tracking boards placed in a woods or wooded fencerow. Regression analyses of landscape compositional and physiognomic variables within a 1-km radius isolated the best predictors of grey and red squirrel abundance and activity. Grey squirrels were found in both small woods and fencerows in farm landscapes but were not found in large woods. A polynomial regression of wooded patch size explained 79% of the variance in grey squirrel abundance. Grey squirrel activity was correlated with the percent cover of soybeans in the landscape. Red squirrels were found in fencerows, small and large woods; activity was correlated with the percent cover of both woods and corn crop in the surrounding landscape. These results indicate that distributions of both species are influenced by multiple landscape elements, but that grey squirrels may rely on fragmented agricultural landscapes whereas red squirrels make more use of both native woodland and altered landscapes. 相似文献
7.
8.
AIM: The aim of this study was to evaluate the potential of variations in stock crate design (especially ventilation) and stocking density on road transport vehicles for reducing the risk of environmental stress for lambs during long-haul transport in hot weather. METHODS: In Experiment 1, lambs were transported on vehicles fitted with either a newer-design aluminium crate comprising a three-deck truck and four-deck trailer, or an older-design, more open, steel crate of a three-deck truck and three-deck trailer. In Experiment 2, lambs were transported on newer-design vehicles at either standard stocking density (0.20 m2 per 35 kg lamb) or at a 20% lower density (0.26 m2 per 35 kg lamb). In each experiment, each journey was replicated twice and consisted of travel periods and stationary periods designed to emulate conditions associated with an inter-island ferry crossing. Air ammonia concentrations and temperature and humidity were monitored within six pens on each vehicle, and the temperature-humidity index (THI) was calculated. RESULTS: Ammonia concentrations were variable and generally 50 ppm, and did not vary significantly with treatment. The THI increased when the vehicles were stationary, especially under conditions designed to emulate an enclosed ferry deck. The ambient temperature during Experiment 1 was moderate (up to 21 degrees C), and THI was slightly lower in the older-design crate. High ambient temperatures (up to 33 degrees C) were present during Experiment 2, and THI was significantly lower at the lower stock density. During a 3-h stationary period, the peak THI at standard stocking density was 91.0, compared with 84.9 for the low density treatment (p<0.001). CONCLUSIONS: For standard road transport vehicles used for long-haul transport of lambs, lowered loading density may be of considerable benefit in alleviating conditions that increase the risk of lamb deaths during inter-island transport on hot days. 相似文献
9.
Objective To determine the effectiveness of a topical anaesthetic formulation (Tri-Solfen) with or without the administration of a non-steroidal anti-inflammatory drug (carprofen) on the pain and distress response associated with ring or surgical castration of ram lambs.
Procedures Merino ram lambs (n = 78) were allocated to 10 treatment groups: 4 groups of knife-castrated lambs and 4 groups of ring-castrated lambs received carprofen (4 mg/kg SC) and Tri-Solfen; 2 control groups (sham) received carprofen at 0 or 4 mg/kg SC. Measurements included plasma cortisol and haptoglobin concentrations, haematology, and behaviour, including posture.
Results Knife-castrated lambs had higher peak cortisol and integrated cortisol responses for the first 6 h after treatment and greater concentration s of circulating acute phase proteins than ring-castrated lambs, both of which were significantly different from the sham controls. Tri-Solfen applied to the knife castration wound significantly reduced both the peak plasma cortisol concentration and the integrated cortisol response for the first 6 h and improved lying behaviour in the first 12 h. Carprofen reduced the cortisol response to knife castration at 30 min, but elevated the cortisol responses at 24 and 48 h. Carprofen nearly halved the number of acute pain behaviours associated with ring castration. There were no significant additive or synergistic effects from combining the analgesic treatments. Tri-Solfen applied to the tail wound provided no detectible benefits during ring castration + tail docking.
Conclusions The physiological and behavioural responses suggest that ring castration has less impact on the lamb than knife castration. The specific analgesic treatments can provide modest amelioration of the pain and discomfort associated with castration. Alternative doses or application methods may enhance their efficacy. 相似文献
Procedures Merino ram lambs (n = 78) were allocated to 10 treatment groups: 4 groups of knife-castrated lambs and 4 groups of ring-castrated lambs received carprofen (4 mg/kg SC) and Tri-Solfen; 2 control groups (sham) received carprofen at 0 or 4 mg/kg SC. Measurements included plasma cortisol and haptoglobin concentrations, haematology, and behaviour, including posture.
Results Knife-castrated lambs had higher peak cortisol and integrated cortisol responses for the first 6 h after treatment and greater concentration s of circulating acute phase proteins than ring-castrated lambs, both of which were significantly different from the sham controls. Tri-Solfen applied to the knife castration wound significantly reduced both the peak plasma cortisol concentration and the integrated cortisol response for the first 6 h and improved lying behaviour in the first 12 h. Carprofen reduced the cortisol response to knife castration at 30 min, but elevated the cortisol responses at 24 and 48 h. Carprofen nearly halved the number of acute pain behaviours associated with ring castration. There were no significant additive or synergistic effects from combining the analgesic treatments. Tri-Solfen applied to the tail wound provided no detectible benefits during ring castration + tail docking.
Conclusions The physiological and behavioural responses suggest that ring castration has less impact on the lamb than knife castration. The specific analgesic treatments can provide modest amelioration of the pain and discomfort associated with castration. Alternative doses or application methods may enhance their efficacy. 相似文献
10.
Thomas G. Nyland DVM Brett M. Kantrowitz DVM †Paul Fisher Harvey J. Olander DVM PHD‡ William J. Hornof DVM MS 《Veterinary radiology & ultrasound》1989,30(4):174-180
Canine kidney measurements were obtained in vivo using ultrasound before and after anesthesia and were compared with direct caliper measurements at laparotomy. Following excision, the kidney dimensions were also measured ultrasonically in a water bath and the results were used to calculate kidney -volume by a modified parallel planimetric method and three variations of a prolate ellipsoid method. The calculated volume was compared with actual kidney volume determined by volume displacement. All methods were found to underestimate actual volume so that a linear correction of ultrasonically calculated volume was required to predict actual volume. The modified parallel planimetric method and a prolate ellipsoid method using height and width determinations cranial and caudal to the renal pelvis were the best models. The prolate ellipsoid model was chosen for subsequent kidney volume calculations because of its simplicity. The noninvasive calculation of kidney volume using ultrasound was sufficiently accurate to be clinically useful, particularly when serially evaluating kidney size changes in the same dog. 相似文献