全文获取类型
收费全文 | 1105篇 |
免费 | 156篇 |
专业分类
林业 | 54篇 |
农学 | 11篇 |
基础科学 | 5篇 |
126篇 | |
综合类 | 196篇 |
农作物 | 30篇 |
水产渔业 | 53篇 |
畜牧兽医 | 709篇 |
园艺 | 20篇 |
植物保护 | 57篇 |
出版年
2021年 | 17篇 |
2020年 | 13篇 |
2019年 | 21篇 |
2018年 | 14篇 |
2017年 | 22篇 |
2016年 | 14篇 |
2015年 | 20篇 |
2014年 | 11篇 |
2013年 | 53篇 |
2012年 | 46篇 |
2011年 | 53篇 |
2010年 | 29篇 |
2009年 | 32篇 |
2008年 | 51篇 |
2007年 | 49篇 |
2006年 | 40篇 |
2005年 | 27篇 |
2004年 | 39篇 |
2003年 | 34篇 |
2002年 | 27篇 |
2001年 | 25篇 |
2000年 | 23篇 |
1999年 | 27篇 |
1998年 | 16篇 |
1997年 | 15篇 |
1996年 | 26篇 |
1991年 | 17篇 |
1990年 | 12篇 |
1989年 | 24篇 |
1988年 | 15篇 |
1987年 | 15篇 |
1986年 | 11篇 |
1985年 | 15篇 |
1983年 | 11篇 |
1982年 | 11篇 |
1981年 | 14篇 |
1978年 | 13篇 |
1977年 | 10篇 |
1976年 | 19篇 |
1975年 | 11篇 |
1974年 | 17篇 |
1973年 | 13篇 |
1972年 | 20篇 |
1971年 | 15篇 |
1970年 | 11篇 |
1969年 | 10篇 |
1967年 | 10篇 |
1966年 | 17篇 |
1939年 | 15篇 |
1938年 | 10篇 |
排序方式: 共有1261条查询结果,搜索用时 15 毫秒
961.
The daily requirement for calcium and phosphorus by giraffes to sustain the growth and maintenance of their skeletons is large. The source of sufficient calcium is browse. The source of necessary phosphorus is obscure, but it could be osteophagia, a frequently observed behaviour in giraffes. We have assessed whether bone ingested as a result of osteophagia can be digested in the rumen. Bone samples from cancellous (cervical vertebrae) and dense bones (metacarpal shaft) were immersed in the rumens of five sheep, for a period of up to 30 days, and the effect compared to immersion in distilled water and in artificial saliva for 30 days. Distilled water had no effect on the bones. Dense bone samples were softened by exposure to the saliva and rumen fluid, but did not lose either calcium or phosphorus. In saliva and rumen fluid the cancellous bone samples also softened, and their mass and volume decreased as a result of exposure to saliva, but in neither fluid did they lose significant amounts of calcium and phosphorus. We conclude that although saliva and rumen fluid can soften ingested bones, there is an insignificant digestion of bones in the rumen. 相似文献
962.
Pritchard GC Scholes SF Foster AP Mitchell ES Lawes J Ibata G Banks M 《The Veterinary record》2008,163(3):86-89
Outbreaks of ulcerative vulvitis and balanitis occurred in three commercial sheep flocks in England and Wales. Between 29 and 44 per cent of the ewes were affected; most of the lesions resolved in three weeks. Pathogens such as mycoplasmas, which have previously been associated with these conditions, were not detected despite using improved laboratory techniques. In one of the flocks, ovine herpesvirus type 2 was detected by pcr in the blood of two acutely affected ewes, from the vulval ulcers of one of them, and from the penis of an affected ram. 相似文献
963.
964.
K. Keven Williams Mitchell D. McCartney Rebecca L. Rice Martin B. Wax Joseph W. Hiddemen 《Veterinary ophthalmology》2008,11(5):327-334
Purpose These studies examined corneal healing rates, Type‐IV collagen and zonula occludens membrane‐associated protein (ZO‐1) expression, as well as aqueous PGE2 and IL‐1β concentrations in pigmented rabbits treated with either moxifloxacin 0.5%, gatifloxacin 0.3% or BSS® following anterior keratectomy. Methods Anterior keratectomy surgery was followed by topical administration with commercial ophthalmic formulations of either moxifloxacin or gatifloxacin or BSS® (TID for 96 h). Images of the fluorescein‐stained healing corneas were analyzed for wound area. At 48 or 96 h following surgery, aqueous humor samples were collected and analyzed for the inflammatory mediators PGE2 and IL‐1β using an ELISA. The corneas were subsequently evaluated using both scanning and transmission electron microscopy. In a second parallel study, corneas were evaluated at both 48 and 96 h for Type‐IV collagen and ZO‐1 expression using immunohistochemistry. Results Fluorescein‐stained corneal images at 96 h postsurgery demonstrated that 90% ± 8% re‐epithelialization for moxifloxacin, 81% ± 14% for gatifloxacin, and 88 ± 6% for BSS® (P > 0.05). PGE2 levels in the aqueous humor of fluoroquinolone treated eyes were reduced at 48 h compared to BSS® treated eyes. IL‐1β was undetectable in all samples. No differences in Type‐IV collagen or ZO‐1 expression were observed between any treatment groups. There were no differences between groups in histological appearance or in ultrastructural healing processes. Conclusions These studies demonstrated that the commercial ophthalmic formulations of moxifloxacin and gatifloxacin were similar to each other in their effects on the levels of aqueous humor PGE2 and rates of corneal wound re‐epithelialization. 相似文献
965.
DuVernoy TS Mitchell KC Myers RA Walinski LW Tinsley MO 《Zoonoses and public health》2008,55(8-10):431-435
This article is the first to describe the clinical picture and potential human health impact of laboratory-confirmed rabies infection in a pet Vietnamese pot-bellied pig in Maryland. Although cases of confirmed rabies infection have been infrequently reported in pet or agricultural during the past 10 years in the United States, exposure to rabies-positive animals remains a public health concern particularly for veterinarians, pet owners and other animal caretakers. It is important that individuals who are in a high-risk rabies exposure group remain vigilant to this potential public health threat in all mammal species. 相似文献
966.
967.
Objectives— To compare monotonic biomechanical properties and fatigue life of a 5.5 mm broad limited‐contact dynamic compression plate (5.5‐LC‐DCP) fixation with a 4.5 mm broad LC‐DCP (4.5‐LC‐DCP) fixation to repair osteotomized equine third metacarpal (MC3) bones. Study Design— In vitro biomechanical testing of paired cadaveric equine MC3 with a mid‐diaphyseal osteotomy, stabilized by 1 of 2 methods for fracture fixation. Sample Population— Adult equine cadaveric MC3 bones (n=18 pair). Methods— MC3 were divided into 3 test groups (6 pairs each) for: (1) 4‐point bending single cycle to failure testing; (2) 4‐point bending cyclic fatigue testing; and (3) torsional single cycle to failure testing. The 8‐hole, 5.5 mm broad LC‐DCP (5.5‐LC‐DCP) was applied to the dorsal surface of 1 randomly selected bone from each pair. One 8‐hole, 4.5 mm broad LC‐DCP (4.5‐LC‐DCP) was applied dorsally to the contralateral bone from each pair. Plates and screws were applied using standard ASIF techniques. All MC3 bones had mid‐diaphyseal osteotomies. Mean test variable values for each method were compared using a paired t–test within each group. Significance was set at P<.05. Results— Mean yield load, yield bending moment, composite rigidity, failure load and failure bending moment under 4‐point bending, single cycle to failure, of the 5.5‐LC‐DCP fixation were significantly greater (P<.024) than those of the 4.5‐LC‐DCP fixation. Mean cycles to failure for 4‐point bending was significantly (P<.05) greater for the 4.5‐LC‐DCP fixation compared with the 5.5‐LC‐DCP fixation. Mean yield load, mean composite rigidity, and mean failure load in torsion for the 5.5‐LC‐DCP fixation was not significantly different (P>.05) than those with the 4.5‐LC‐DCP fixation. Conclusion— 5.5‐LC‐DCP fixation was superior to 4.5‐LC‐DCP fixation in resisting the static overload forces under palmarodorsal 4‐point bending. There was no significant difference between 5.5‐LC‐DCP fixation and 4.5‐LC‐DCP fixation in resisting static overload forces under torsion; however, the 5.5‐LC‐DCP offers significantly less stability (80% of that of the 4.5‐LC‐DCP) in cyclic fatigue testing. Clinical Relevance— The results of this in vitro study may provide information to aid in the selection of a biological plate for long bone fracture repair in horses. 相似文献
968.
Mark A Mitchell Orlando Diaz-Figueroa 《Veterinary Clinics of North America: Exotic Animal Practice》2004,7(1):123-140
Our understanding into the healing response of reptile wounds is in its infancy. To date, many of the methods we have used have been adopted from human, mammalian, or avian species, with varying success. Future research should focus on the development of methods to improve our management of contaminated wounds, minimize the negative inflammatory responses occurring in a wound, and shorten wound-healing time. 相似文献
969.
Mitchell V Palmer W Ray Waters Diana L Whipple Ralph E Slaughter Stephen L Jones 《Journal of veterinary diagnostic investigation》2004,16(1):17-21
Tuberculosis due to Mycobacterium bovis in captive Cervidae was identified as an important disease in the United States in 1990 and prompted the addition of captive Cervidae to the USDA Uniform Methods and Rules for eradication of bovine tuberculosis. As well, M. bovis infection was identified in free-ranging white-tailed deer in northeast Michigan in 1995. Tuberculosis in both captive and free-ranging Cervidae represents a serious challenge to the eradication of M. bovis infection from the United States. Currently, the only approved antemortem tests for tuberculosis in Cervidae are the intradermal tuberculin skin test and the blood tuberculosis test (BTB). At present, the BTB is not available in North America. Tuberculin skin testing of Cervidae is time-consuming and involves repeated animal handling and risk of injury to animals and humans. This study evaluated the potential of a new blood-based assay for tuberculosis in Cervidae that would decrease animal handling, stress, and losses due to injury. In addition, a blood-based assay could provide a more rapid diagnosis. Twenty 6-9-month-old white-tailed deer, male and female, were experimentally inoculated by instillation of 300 colony-forming units of M. bovis in the tonsillar crypts. Seven, age-matched uninfected deer served as controls. Blood was collected on days 90, 126, 158, 180, 210, 238, 263, and 307 after inoculation and was analyzed for the production of interferon-gamma (IFN-gamma) in response to incubation with M. bovis purified protein derivative (PPDb), M. avium PPDa, pokeweed mitogen (PWM), or media alone. Production of IFN-gamma in response to PPDb was significantly greater (P < 0.05) at all time points in samples from M. bovis-infected deer as compared with uninfected control deer, whereas IFN-gamma production to PWM did not differ significantly between infected and control deer. Measurement of IFN-gamma production to PPDb may serve as a useful assay for the antemortem diagnosis of tuberculosis in Cervidae. 相似文献
970.