全文获取类型
收费全文 | 38633篇 |
免费 | 2276篇 |
国内免费 | 285篇 |
专业分类
林业 | 1607篇 |
农学 | 1418篇 |
基础科学 | 326篇 |
5547篇 | |
综合类 | 5674篇 |
农作物 | 1493篇 |
水产渔业 | 1831篇 |
畜牧兽医 | 20100篇 |
园艺 | 460篇 |
植物保护 | 2738篇 |
出版年
2021年 | 378篇 |
2020年 | 442篇 |
2019年 | 476篇 |
2018年 | 793篇 |
2017年 | 845篇 |
2016年 | 764篇 |
2015年 | 646篇 |
2014年 | 805篇 |
2013年 | 1852篇 |
2012年 | 1333篇 |
2011年 | 1544篇 |
2010年 | 1069篇 |
2009年 | 1110篇 |
2008年 | 1518篇 |
2007年 | 1352篇 |
2006年 | 1265篇 |
2005年 | 1087篇 |
2004年 | 1054篇 |
2003年 | 1053篇 |
2002年 | 922篇 |
2001年 | 1260篇 |
2000年 | 1248篇 |
1999年 | 929篇 |
1998年 | 387篇 |
1997年 | 422篇 |
1996年 | 342篇 |
1995年 | 392篇 |
1994年 | 341篇 |
1992年 | 660篇 |
1991年 | 783篇 |
1990年 | 686篇 |
1989年 | 722篇 |
1988年 | 662篇 |
1987年 | 629篇 |
1986年 | 671篇 |
1985年 | 599篇 |
1984年 | 465篇 |
1983年 | 413篇 |
1979年 | 554篇 |
1978年 | 434篇 |
1977年 | 361篇 |
1976年 | 366篇 |
1975年 | 398篇 |
1974年 | 460篇 |
1973年 | 475篇 |
1972年 | 451篇 |
1970年 | 367篇 |
1969年 | 403篇 |
1968年 | 358篇 |
1967年 | 359篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Objective To determine ocular distribution and toxicity of a single injection of intravitreal triamcinolone acetonide (TA) in normal horses.
Animals studied Six adult horses, donated to North Carolina State University.
Procedures Six horses were injected intravitreally with either 10, 20, or 40 mg ( n = 2 each) of TA. The opposite eye of each horse was injected with balanced salt solution (BSS). Ocular toxicity was assessed by biomicroscopy, tonometry, indirect ophthalmoscopy, and electroretinogram. Aqueous humor (AH), vitreous humor (VH), and plasma samples were collected. Horses were euthanized 7 or 21 days after injection and eyes enucleated for histopathology. TA concentrations in AH, VH, and plasma were measured by HPLC.
Results Three control eyes and one TA eye developed inflammation after injection or collection of AH. Positive bacterial cultures ( Corynebacterium spp., Staphylococcus spp., and Streptococcus spp.) were obtained from three of these eyes. Other than transient corneal edema in TA injected eyes, which resolved by 7 days after injection, no other changes were observed. TA crystals were visible within the vitreous body. No evidence of TA toxic effect was noted on histopathology. TA was detected in all AH and VH samples from treated eyes following injection. Drug was not detected in the plasma.
Conclusions There was no evidence of overt toxicity from intravitreal TA in normal horses and a single intravitreal injection resulted in TA ocular levels for 21 days. However, the risk for bacterial infections with intravitreal injection or anterior chamber aspirations in horses is high. Use of topical and systemic antibiotics after injection is recommended. 相似文献
Animals studied Six adult horses, donated to North Carolina State University.
Procedures Six horses were injected intravitreally with either 10, 20, or 40 mg ( n = 2 each) of TA. The opposite eye of each horse was injected with balanced salt solution (BSS). Ocular toxicity was assessed by biomicroscopy, tonometry, indirect ophthalmoscopy, and electroretinogram. Aqueous humor (AH), vitreous humor (VH), and plasma samples were collected. Horses were euthanized 7 or 21 days after injection and eyes enucleated for histopathology. TA concentrations in AH, VH, and plasma were measured by HPLC.
Results Three control eyes and one TA eye developed inflammation after injection or collection of AH. Positive bacterial cultures ( Corynebacterium spp., Staphylococcus spp., and Streptococcus spp.) were obtained from three of these eyes. Other than transient corneal edema in TA injected eyes, which resolved by 7 days after injection, no other changes were observed. TA crystals were visible within the vitreous body. No evidence of TA toxic effect was noted on histopathology. TA was detected in all AH and VH samples from treated eyes following injection. Drug was not detected in the plasma.
Conclusions There was no evidence of overt toxicity from intravitreal TA in normal horses and a single intravitreal injection resulted in TA ocular levels for 21 days. However, the risk for bacterial infections with intravitreal injection or anterior chamber aspirations in horses is high. Use of topical and systemic antibiotics after injection is recommended. 相似文献
82.
The diurnal activity patterns of sub-Antarctic fur seals, Arctocephalus tropicalis, were observed at a non- breeding colony site at Gough Island (40°20′S, 9°54′W) during summer. Time budgets of adult males were also studied at idle and breeding colony sites, Levels of activity were highest during the early morning and late afternoon. High ambient temperatures depressed the interaction rate on the dry hauling ground, but activity increased as a result of the movement of heat-stressed seals to and from the sea where favourable conditions for heat loss exist. The fur seals were largely inactive, in particular adult males which spent 93,2% of the time inactive in breeding colonies and 97,9% of Ihe time inactive at idle colony beaches. The daily change in numbers ashore, the relative contribution of the different age and sex classes, their location and distribution on site, and the prevailing weather conditions influence the pattern of interaction and allocation of time to the various activities in A. tropicalis. The predominance of inactivity is considered to be a behavioural thermoregulatory response to limit endogenous heat production as is energy conservation. Both views translate into improved tenure for territorial males, in particular those without access to water for cooling during the breeding season. 相似文献
83.
Cho HS Park NY 《Journal of veterinary medicine. A, Physiology, pathology, clinical medicine》2006,53(9):464-466
An 8-year-old female African wild dog (Lycaon pictus) from a zoo in Gyeonggi province, Republic of Korea presented with a 3.0 x 2.0 x 2.5 cm in size, smooth-surfaced, solitary pedunculated mass protruding into the uterine lumen. Microscopically, the mass was covered with epithelium, contained endometrial gland tissue, and was dilated in the vascularised stroma. Within the mass, there was extensive diffuse haemorrhage with several blood vessels apparently plugged with fibrin. At the base of the mass, the spaces lined with epithelium near the attachment of the stalk were interpreted to be glandular structures. There were segments of cuboidal epithelium found on the surface of the mass, which was similar to the lining the uterus. A diagnosis of an endometrial polyp was made based on the gross and histology findings. This is the first case report of a spontaneous endometrial polyp in an African wild dog. 相似文献
84.
85.
86.
1. Coir dust was evaluated as broiler litter in comparison with sawdust and rice husk using 135 commercial broilers. Forty-five broiler chicks were reared to 42 d on a 50 mm layer of each of these litters. 2. Birds reared on coir dust showed no difference in food consumption, body weight gain, food conversion efficiency production number and survivability in comparison to those reared on saw dust and rice husk. 3. It was concluded that coir dust is suitable as broiler litter when cheaply available. 相似文献
87.
全球禽肉生产和贸易中的沙门菌风险评估与控制 总被引:1,自引:0,他引:1
G.Mead A.M.Lammerding N.Cox M.P.Doyle F.Humbert A.Kulikocskiy A.Panin V.P.do Nascimento M.Wierup 《中国家禽》2011,33(5)
1 禽源沙门菌对公共卫生的影响
在许多国家,沙门菌仍是引发食源性肠道疾病的主要原因.沙门菌通常存在于家畜、家禽中,也可在啮齿类、爬行类和鸟类等野生动物中发现.当农场的禽群感染沙门菌后,通常会有一部分家禽的消化道中携带沙门菌,但并无症状.随后,沙门菌可能会通过粪便污染感染动物屠体. 相似文献
88.
K P Barrie G G Gum D A Samuelson K N Gelatt 《American journal of veterinary research》1985,46(1):89-97
Aqueous humor leaves the anterior chamber through 2 pathways: the trabecular meshwork of the iridocorneal angle and the unconventional uveoscleral route. In the latter route, aqueous humor leaves the anterior chamber, passes caudally through the trabecular meshwork and sclerociliary cleft to enter the supraciliary and suprachoroidal spaces. The fluid is absorbed by the choroidal and scleral circulation. Fluorescein-labeled dextran was slowly infused into the posterior chamber of healthy and glaucomatous Beagles for 30 minutes. The eyes were fixed in a mixture of 70% alcohol and formalin, placed in epoxy resin for histologic evaluation, and examined by fluorescent microscopy. Fluorescence was detected in the healthy dogs throughout the uveoscleral pathway. In the glaucomatous dogs, the uveoscleral outflow was decreased or completely absent. 相似文献
89.
Digestibility of fiber components and reproductive performance of sows fed high levels of alfalfa meal 总被引:4,自引:0,他引:4
Two experiments were conducted with second-parity sows fed either 5 or 50% alfalfa meal diets (Exp. 1) or 5, 50 or 95% alfalfa meal diets (Exp. 2) beginning 30 d after breeding and continuing through lactation, 21 d postpartum. Diets in both experiments were calculated to be equal in crude protein, but different in metabolizable energy content. Feed intake was restricted to 2 kg/d during gestation and ad libitum during lactation. Sows were tethered in metabolism crates 45 d after breeding. Total feces were collected during two 5-d collection periods, 60 and 100 d after breeding. Digestibilities of dry matter, fiber components (neutral detergent fiber, acid detergent fiber, hemicellulose and cellulose), protein and energy were determined in both experiments for all diets and periods of gestation. In both experiments, there was a reduction (P less than .05) in digestibility of dry matter, fiber components, protein and energy with increasing fiber levels for both periods of gestation. In Exp. 1, the decrease in digestibility of dry matter, neutral detergent fiber, acid detergent fiber, cellulose and energy was greater at 100 d gestation than at 60 d in sows fed 50% alfalfa. In Exp. 2, 50 and 95% dietary alfalfa reduced 60-d digestibilities of dry matter, all fiber constituents, energy and protein; these digestibilities were further reduced (P less than .05) at 100 d of gestation. In Exp. 1, weight gains of sows fed 5 and 50% alfalfa diets from breeding to 109 d gestation, were 42 and 18 kg/sow (5 greater than 50% level, P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
90.
Seven wild-caught ball pythons (Python regius), including six gravid females and one male, were obtained from Africa and were housed in a government animal facility in Research Triangle Park, North Carolina. Upon arrival, the snakes were found to be infested with ticks (Aponomma latus), which were manually removed. Four weeks following arrival, vesicular skin lesions began to appear on the snakes. Despite treatment of all affected female snakes with amikacin (5 mg/kg i.m., every 3 days) and cefotaxime (25 mg/kg i.m., every 3 days), the condition progressed and five of the female snakes died 7 wk after arrival. The remaining male and one female improved after an increase in environmental temperature, with ecdysis followed by healing. Physiologic stress, ectoparasites, and shipping may have predisposed the snakes to sepsis. 相似文献