全文获取类型
收费全文 | 202篇 |
免费 | 6篇 |
专业分类
林业 | 23篇 |
农学 | 2篇 |
10篇 | |
综合类 | 40篇 |
农作物 | 1篇 |
水产渔业 | 11篇 |
畜牧兽医 | 111篇 |
园艺 | 3篇 |
植物保护 | 7篇 |
出版年
2023年 | 2篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2018年 | 2篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2014年 | 2篇 |
2013年 | 3篇 |
2012年 | 9篇 |
2011年 | 5篇 |
2010年 | 3篇 |
2009年 | 3篇 |
2008年 | 7篇 |
2007年 | 10篇 |
2006年 | 7篇 |
2005年 | 6篇 |
2004年 | 6篇 |
2003年 | 2篇 |
2001年 | 5篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 8篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 16篇 |
1987年 | 13篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 6篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1974年 | 2篇 |
1972年 | 2篇 |
1958年 | 2篇 |
1955年 | 2篇 |
1953年 | 2篇 |
1931年 | 1篇 |
1919年 | 1篇 |
1903年 | 1篇 |
1902年 | 1篇 |
1900年 | 2篇 |
1899年 | 1篇 |
1895年 | 1篇 |
1893年 | 2篇 |
1892年 | 3篇 |
1884年 | 2篇 |
1883年 | 1篇 |
排序方式: 共有208条查询结果,搜索用时 187 毫秒
141.
Paul A. Sandifer Addison L. Lawrence Susan G. Harris George W. Chamberlain Alvin D. Stokes William A. Bray 《Aquaculture (Amsterdam, Netherlands)》1984,41(2):181-187
Electrical stimulation (4–6 V AC) applied near the male gonopores at the base of the fifth pereopods caused expulsion of the spermatophore in Penaeus setiferus, P. stylirostris, and P. vannamei. For healthy animals, some degree of spermatophore expulsion occurred in 80% of the attempts. Complete expulsion of one or both spermatophores occurred in only 47% (29–65%, depending on species). Shrimp with melanized terminal ampullae generally did not expel a spermatophore following electrical stimulation. The technique needs further refinement for routine use with penaeids. 相似文献
142.
Intensification of Shrimp Culture in Earthen Ponds in South Carolina: Progress and Prospects 总被引:1,自引:0,他引:1
Paul A. Sandier J. Stephen Hopiuns Alvin D. Stokes 《Journal of the World Aquaculture Society》1988,19(4):218-226
Experiments on the intensive cultivation of Pacific white shrimp, Penueus vunnumei, in ponds in South Carolina were begun in 1985 at the Waddell Mariculture Center. A preliminary study involved two 0.1 ha ponds stocked at an average of 43 postlarvae/m2, with management practices based on those used in Taiwan for intensive pond culture of Penueus monodon. Harvest yields averaged 6,757 kg/ha for one crop, demonstrating the technical feasibility of such intensive culture of P. vannumei. In 1986, 2.5 ha of ponds at the Waddell Center (six ponds totaling 2.0 ha at 40 postlarvae/m2 and two totaling 0.5 ha at 60/m2) yielded a total of 13,606 kg (5,442 ke/hn). These results were obtained even though aeration and water exchange rates were substanthlly reduced and South Carolina experienced its worst heat wave and drought. This served as a pilot-sde, proof-ofconcept test. Tank studies in 1985 and 1986 showed little effect of stocking density on shrimp growth rate at densities of 20–100 animals/m2. This was confirmed in ponds in 1987 when no differences in growth rates were observed at densities of 20–100 postlarvae/m2. Harvest biomass increased directly with stocking density in all trials, reaching a maximum of 12,680 kg/ha/crop at 100 shrimp/m2 in 1987. Initial attempts to intensify production in the nascent South Carolina shrimp farming industry occurred in 1986, when approximately 32 ha of private ponds were stocked at densities of 10–32 postlarvae/m2. Farm harvests increased with stocking density, with maximum yield of 3,656 kg/ ha/crop. This trend toward intensification in the private sector is continuing, and in 1987 maximum harvests from private ponds were 5,050 kg/ha from a 0.3 ha pond and 4,625 kg/ha from a 1.5 ha pond. Prospects for further implementation of intensive culture in the private sector appear excellent, with yields of ≥ 10,000 kg/ha/crop expected from private farms within the next few years. 相似文献
143.
Alyce L. Marks Silke Hecht Jennifer E. Stokes Gordon A. Conklin Katherine H. Deanna 《Veterinary radiology & ultrasound》2014,55(3):286-291
Gadoxetate disodium (Gd‐EOB‐DTPA; gadolinium‐ethoxybenzyl‐diethylene triamine penta‐acetic acid) is a newly developed paramagnetic contrast agent reported to have a high specificity for the hepatobiliary system in humans. The purpose of this prospective study was to describe effects of Gd‐EOB‐DTPA contrast administration on MRI characteristics of the liver in eight clinically healthy dogs. Precontrast dorsal and transverse T1‐weighted spin echo, T2‐weighted fast spin echo, and transverse T1‐weighted 3D gradient echo (VIBE; volume‐interpolated body examination) pulse sequences were acquired for each dog. Dogs were assigned to four groups based on contrast dose administered (0.0125 mmol/kg or 0.025 mmol/kg), and pulse sequences acquired after contrast administration (T1‐weighted spin echo and T1‐weighted 3D gradient echo). Liver signal intensity ratios were calculated and compared between the two contrast dose groups and two postcontrast pulse sequence groups using ANOVA. No adverse effects of contrast administration were observed. All dogs exhibited homogeneous contrast enhancement of the liver with no statistical difference in enhancement between the two different contrast doses. Contrast enhancement in all dogs peaked between 1 and 10 min after intravenous injection. There was a significant difference in mean signal intensity ratios between sequences (P = 0.035) but not between doses (P = 0.421). Postcontrast signal intensities of the liver parenchyma were significantly higher for the T1‐weighted 3D gradient echo images when compared to the T1‐weighted spin echo sequences. Findings indicated that Gd‐EOB‐DTPA contrast administration is safe in healthy dogs and causes homogeneous enhancement of the liver that is more pronounced in T1‐weighted 3D gradient echo MRI pulse sequences. 相似文献
144.
Gretchen L. Stokes Leandro Castello Thiago A. Petersen Steven J. Cooke Michael Power Jansen Zuanon Eduardo G. Martins 《水产资源保护:海洋与淡水生态系统》2021,31(6):1257-1268
- Arapaima (Arapaima sp.) are highly overexploited fish endemic to the Amazon basin. Because the fish are obligate air-breathers, it is possible to use surface-breathing events to count individuals visually for population censuses important for conservation, yet uncertainties remain about body size and environmental influences on air-breathing intervals, and thus count accuracy.
- This study examined relationships between breathing intervals and environmental parameters (e.g. water temperature and transparency) and body size for radio-tagged arapaima (n = 12) in an upland river-floodplain (Lake Ayapuá, Amazonas, Brazil). Generalized additive mixed models were used to evaluate environmental, size, and behavioural correlates of breathing intervals.
- Temperature was the most influential predictor of air-breathing intervals, followed by body size. The shortest breathing intervals were associated with consecutive ‘aggressive’ breaths while the longest breathing intervals had consecutive ‘calm’ breaths. Type of breath, size, and temperature predictors revealed that breathing intervals ranged from 4 to 46 min and were not significantly different among life stages ( = 15.9 min for sub-adults and adults (>1 m); = 14.8 min for juveniles (<1 m)).
- Whereas the current population census method uses fish counts in 20-min intervals, this study found that 15% of observed breaths, and two thirds of fish, took longer than 20 min to breathe. These findings were obtained in relatively cool-water environments, so it is recommended that future population census methods consider water temperature (e.g. extend intervals used for counts in cooler waters), which may improve the accuracy of census counts and thus further enhance arapaima conservation efforts.
- This study demonstrated an effective method in which fundamental biological information is used to inform and improve population census methods for an imperilled fish in a region where traditional stock assessment is ineffective. Similar approaches for adaptive stock assessments could be applied to improve conservation of other air-breathing fishes (e.g. lungfishes) globally.
145.
The immune response to dietary antigens and its influence on disease susceptibility in farm animals 总被引:5,自引:0,他引:5
C R Stokes B G Miller M Bailey A D Wilson F J Bourne 《Veterinary immunology and immunopathology》1987,17(1-4):413-423
Transient hypersensitivity reactions of the intestinal immune system to dietary antigens result in increases in enterocyte turnover and villous atrophy. These changes occur in the intestine of the post weaned piglet and precede the proliferation of E. coli and the development of post-weaning diarrhea. We therefore postulated that a transient cell mediated immune response to dietary antigens may increase susceptibility to disease. The interaction of dietary and microbial antigens upon the gut immune system has been investigated in mice and pigs and it has been shown that both exert powerful regulatory effects upon each other. 相似文献
146.
Creep feeding and post weaning diarrhoea in piglets 总被引:3,自引:0,他引:3
147.
Henry CJ Tyler JW McEntee MC Stokol T Rogers KS Chun R Garrett LD McCaw DL Higginbotham ML Flessland KA Stokes PK 《American journal of veterinary research》2003,64(8):1017-1020
OBJECTIVE: To evaluate the veterinary version of the bladder tumor antigen (V-BTA) test as a screening test for transitional cell carcinoma (TCC) of the lower urinary tract of dogs. ANIMALS: 229 client-owned dogs. PROCEDURE: Urine samples from dogs were shipped overnight to a single laboratory to facilitate testing within 48 hours of collection by use of the V-BTA rapid latex agglutination urine dipstick test. Groups of dogs included the following: 1) dogs with TCC of the lower urinary tract, 2) healthy control dogs, 3) unhealthy control dogs with non-TCC urinary tract disease, and 4) unhealthy control dogs without urinary tract disease. Test sensitivity and specificity were calculated by use of standard methods. Logistic models were developed to assess the effect of disease status, test conditions, urine composition, and signalment on the performance of the V-BTA test. RESULTS: A total of 229 urine samples were analyzed, including 48 from dogs with suspected (n = 3) or confirmed (45) TCC. Test sensitivities were 88, 87, and 85% for all dogs with (suspected and confirmed) TCC, dogs with confirmed TCC at any site, and dogs with confirmed TCC of the urinary bladder, respectively. Test specificities were 84, 41, and 86% for healthy control dogs, unhealthy control dogs with non-TCC urinary tract disease, and unhealthy control dogs without urinary tract disease, respectively. The test performed slightly better on centrifuged urine samples than on uncentrifuged urine samples. CONCLUSIONS AND CLINICAL RELEVANCE: Our results indicate that the V-BTA test is useful in screening for urinary tract TCC in dogs. 相似文献
148.
When 47 pigs were dosed orally with cultures of Treponema hyodysenteriae, 44 (94 per cent) developed swine dysentery. Of those which recovered and were rechallenged, nine of 21 (43 per cent) showed clinical signs, as did one of 10 (10 per cent) challenged on a third occasion. Clinical disease was associated with development of specific IgG, IgA and IgM antibodies in serum and the local production of IgA in gut mucosal tissues. The appearance of antibody was not directly related to protection but rather indicated either prolonged exposure (in the case of serum IgG) or recent exposure to T hyodysenteriae (for secretory IgA). Infection also resulted in the appearance of IgG and IgA memory cells in gut-associated lymphoid tissue. However, these studies indicated that humoral immunity alone is not responsible for the onset of a protective response to T hyodysenteriae in the colon. 相似文献
149.
Faleiros RR Stokes AM Eades SC Kim DY Paulsen DB Moore RM 《American journal of veterinary research》2004,65(5):578-585
OBJECTIVE: To determine and compare the number, type, location, and distribution of apoptotic epidermal cells in the laminae of clinically normal horses and horses with laminitis. SAMPLE POPULATION: Formalin-fixed samples of digital lamellar tissue from 47 horses (including clinically normal horses [controls; n = 7], horses with acute [4] and chronic [7] naturally acquired laminitis, and horses with black walnut extract-induced [11] or carbohydrate overload-induced [18] laminitis). PROCEDURE: Blocks of paraffin-embedded lamellar tissues were stained for DNA fragmentation with the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) technique. Differential immunohistochemical staining for caspases 3 and 14 were used to confirm apoptosis. RESULTS: The number of TUNEL-positive epidermal cells per 0.1 mm of primary laminae was significantly greater in the acute laminitis group than in the other groups. In the acute laminitis group, there were 17 and 1,025 times as many TUNEL-positive basal layer cells and keratinocytes, respectively, compared with the control group. Apoptosis of TUNEL-positive basal layer cells was confirmed by results of caspase 3 immunohistochemical staining. The TUNEL-positive keratinocytes did not stain for caspases 3 or 14. CONCLUSIONS AND CLINICAL RELEVANCE: The large number of apoptotic basal layer cells detected in the lamellar tissue of horses with acute naturally acquired laminitis suggests that apoptosis may be important in the development of acute laminitis. The role of the large number of TUNEL-positive keratinocytes detected in the interface of primary and secondary epidermal laminae of horses with acute laminitis remains to be elucidated. 相似文献
150.