全文获取类型
收费全文 | 178篇 |
免费 | 8篇 |
国内免费 | 1篇 |
专业分类
农学 | 7篇 |
基础科学 | 2篇 |
22篇 | |
综合类 | 41篇 |
农作物 | 8篇 |
水产渔业 | 6篇 |
畜牧兽医 | 88篇 |
园艺 | 1篇 |
植物保护 | 12篇 |
出版年
2021年 | 2篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 2篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 2篇 |
2012年 | 9篇 |
2011年 | 9篇 |
2010年 | 6篇 |
2009年 | 4篇 |
2008年 | 6篇 |
2007年 | 3篇 |
2006年 | 7篇 |
2005年 | 5篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 8篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1996年 | 2篇 |
1994年 | 3篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1970年 | 2篇 |
1969年 | 4篇 |
1968年 | 3篇 |
1947年 | 1篇 |
1942年 | 1篇 |
1940年 | 1篇 |
1939年 | 1篇 |
1937年 | 1篇 |
1936年 | 1篇 |
1905年 | 1篇 |
1893年 | 1篇 |
1887年 | 1篇 |
排序方式: 共有187条查询结果,搜索用时 904 毫秒
101.
102.
Fred C. Brewer N. Sydney Moïse Bruce G. Kornreich Abraham J. Bezuidenhout 《Journal of Veterinary Cardiology》2012,14(1):293-300
The pulmonary veins were identified from the silicone endocast heart models of 19 dogs. Although variation in the number of the more peripheral veins on each specimen existed, all of the casts had a consistency with regards to the most proximal coalescence of the pulmonary veins as they entered the body of the left atrium. That is, the confluence of the veins formed three ostia at the atrial entry point that consisted of 1) right cranial and right middle pulmonary lobe veins; 2) right caudal, accessory, and left caudal pulmonary lobe veins; and 3) both the left cranial and left caudal pulmonary lobe veins of the left cranial lung lobe. The location of these structures identified by the 3-dimensional endocasts were then used to assist in the identification of the pulmonary veins using computed tomography of 2 dogs. Slices were made that approximated those commonly performed during echocardiographic examination. Understanding which pulmonary veins are seen by echocardiography in the different imaging planes will permit prospective evaluations of pulmonary vein size and abnormal flow patterns. 相似文献
103.
The emblematic minnows of the North American Great Plains: A synthesis of threats and conservation opportunities
下载免费PDF全文
![点击此处可从《Fish and Fisheries》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Thomas A Worthington Anthony A Echelle Joshuah S Perkin Robert Mollenhauer Nicole Farless Joseph J Dyer Daniel Logue Shannon K Brewer 《Fish and Fisheries》2018,19(2):271-307
Anthropogenic changes to the Great Plains rivers of North America have had a large, negative effect on a reproductive guild of pelagic‐broadcast spawning (PBS) cyprinid fishes. The group is phylogenetically diverse, with multiple origins of the PBS mode. However, because of incomplete life‐history information, PBS designation often relies only on habitat and egg characteristics. We identified 17 known or candidate PBS fishes and systematically synthesized the literature on their biology and ecology in relation to major threats to persistence. Research output on an individual species was unrelated to conservation status, but positively correlated with breadth of distribution. The PBS species have opportunistic life‐history strategies and are typically short‐lived (generally 1–3 years) fishes. Many PBS species have truncated ranges showing declines in both distribution and abundance, especially those endemic to the Rio Grande catchment. Fundamental habitat associations are unknown for many species, particularly regarding seasonal shifts and early life stages. Critical thermal tolerances have been quantified for five PBS species and are generally >35°C. Turbidity and salinity changes are linked to responses at multiple life stages, but information is lacking on interactions between water quality and quantity. Hydrologic alteration appears to be a primary threat to PBS species, through complex interactions with landscape fragmentation, and habitat change. We highlight areas where scientific and management communities are lacking information and underline areas of potential conservation gain. 相似文献
104.
105.
106.
Several observations suggested that enhanced mixed function oxidase (MFO) activity was one of several factors contributing to permethrin and dichlorvos resistance in the mushroom pest, Lycoriella mali (Fitch) (Diptera: Sciaridae). This was investigated using the mixed function oxidase inhibitor, piperonyl butoxide (PBO), in topical application bioassays with reference and field-selected resistant strains. At the LD50, strains of resistant colonies (AV1, AV2, TK1) used in this study were 41-(AV1), 34-(AV2), and 62-fold (TK1) resistant to permethrin, relative to the reference strain (ONT9). Permethrin in the reference strain was only synergized 2- (ONT9) and 4- (ONT13) at the LD50. Synergist ratios for resistant strains were 12 (AV1), 34 (AV2) and 94 (TK1) at the LD50. Moderate dichlorvos resistance was twice documented in the AV strain. Resistance ratios of 37 (AV4) and 52 (AV9) were observed at the LD50, relative to the reference strain (ONT10). Dichlorvos was synergized only 2-fold at the LD50 in the reference strain (ONT10). However, PBO abolished dichlorvos resistance in the AV9 strain. The effectiveness of PBO in these studies indicated that enhanced MFO activity was present in resistant L. mali from southeastern Pennsylvania. Resistance to DDT (54-fold at the LD50) was also documented. Other factors, such as an altered target site (kdr), may also have contributed to control failures with permethrin. 相似文献
107.
108.
D.M. Brewer S. Cerda‐Gonzalez C.W. Dewey D. Boothe K. Van Horne 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2015,29(2):603-606
Background
Few medications are available for parental administration to animals with seizures. Rectal administration of medications is often used if the animal cannot be administered oral medications.Hypothesis/Objectives
To determine the pharmacokinetic differences in zonisamide when administered rectally in either of 2 vehicles and PO to dogs.Animals
Eight healthy research dogs.Methods
Randomized cross‐over design. Zonisamide, 10 mg/kg, was administered rectally in polyethylene glycol (PEG‐R), rectally in water (H2O‐R), and as an oral capsule. Plasma zonisamide concentrations were measured until 72 hours after administration. Zonisamide was quantitated by HPLC and plasma concentration versus time curve data was analyzed by using noncompartmental modeling.Results
Mean maximum plasma zonisamide concentrations (μg/mL) were significantly higher after oral administration (11.56 ± 4.04) compared to H2O‐R (5.00 ± 1.83) (P = .004). Disappearance half‐life (hours) and mean time to maximum concentration (hours) were not significantly different between methods of administration. Mean relative bioavailability of PEG‐R (85 ± 69%) was significantly higher than that of H2O‐R (53 ± 37%) (P = .039). Dogs tolerated all dosing forms with no evidence of adverse effects.Conclusions and Clinical Importance
The vehicle in which zonisamide is dissolved influences rectal bioavailability, with PEG preferred to H2O‐R. Because of the prolonged time to maximum concentration, rectal administration of zonisamide should not be used to treat status epilepticus in dogs. A dose higher than what was used in this study might be necessary, if currently recommended minimum therapeutic concentrations (10 μg/mL) are to be achieved with a single‐dose administration. 相似文献109.
Brewer PS James JM Calkins CR Rasby RM Klopfenstein TJ Anderson RV 《Journal of animal science》2007,85(5):1239-1246
A 2-yr experiment was conducted to compare carcass characteristics and meat palatability attributes of steers ((3/4) British, (1/4) Continental) finished postweaning as calves or yearlings. Calves and yearlings of the same contemporary group were designated to a finishing system at weaning. Calves (n = 73) were finished in the feedlot (191 d) on a high-concentrate diet. Yearlings (n = 84) grazed crop residues after weaning, followed by spring and summer pasture grazing, and concluded with a short finishing period (91 d) in the feedlot. All steers were fed to a constant, fat thickness endpoint of 1 cm. The M. longissimus lumborum steaks from each production system were aged for 7, 14, or 21 d for Warner-Bratzler shear force determination and for 7 or 14 d for in-house sensory panel evaluation. Insoluble, percent soluble, and total collagen were determined. Yearlings produced heavier (P < 0.001) carcasses with larger (P < 0.001) LM areas and lower (P < 0.001) marbling scores and quality grades. Calves possessed greater amounts of total collagen (P < 0.001), with a significantly greater percentage of soluble collagen compared with yearlings (39.72 vs. 24.38%). Calves produced steaks with lower (P < 0.001) shear force values and greater (P < 0.001) sensory ratings for flavor. The USDA Choice steaks from the calves were more (P < 0.001) tender and more (P < 0.050) palatable than Choice steaks from yearlings, and USDA Select steaks from calves were rated more tender (P < 0.001), juicy (P = 0.012), and desirable (P < 0.001) than Select steaks from yearlings. As expected, increasing aging time from 7- to 14- to 21-d produced steaks with lower (P < 0.001) shear force values, regardless of the production system. Risk probabilities showed 1.24% of the steaks from calf-finished steers and 21.22% of steaks from yearling-finished steers to be tough. Sensory rating probabilities showed the steaks from the calves were most likely to be desirable for tenderness, whereas steaks from the yearlings were most likely to be undesirable for tenderness, juiciness, flavor, and overall acceptability. Thus, calf-finished steers produce carcasses superior in quality and palatability compared with those from yearling-finished steers. However, yearling-finished steers can produce tender beef with extended aging. 相似文献