全文获取类型
收费全文 | 8224篇 |
免费 | 408篇 |
国内免费 | 9篇 |
专业分类
林业 | 588篇 |
农学 | 275篇 |
基础科学 | 62篇 |
1387篇 | |
综合类 | 1236篇 |
农作物 | 542篇 |
水产渔业 | 649篇 |
畜牧兽医 | 3033篇 |
园艺 | 215篇 |
植物保护 | 654篇 |
出版年
2023年 | 47篇 |
2022年 | 73篇 |
2021年 | 138篇 |
2020年 | 151篇 |
2019年 | 174篇 |
2018年 | 154篇 |
2017年 | 148篇 |
2016年 | 172篇 |
2015年 | 130篇 |
2014年 | 183篇 |
2013年 | 342篇 |
2012年 | 408篇 |
2011年 | 562篇 |
2010年 | 320篇 |
2009年 | 298篇 |
2008年 | 549篇 |
2007年 | 502篇 |
2006年 | 513篇 |
2005年 | 539篇 |
2004年 | 442篇 |
2003年 | 480篇 |
2002年 | 421篇 |
2001年 | 92篇 |
2000年 | 87篇 |
1999年 | 102篇 |
1998年 | 85篇 |
1997年 | 76篇 |
1996年 | 67篇 |
1995年 | 89篇 |
1994年 | 86篇 |
1993年 | 73篇 |
1992年 | 57篇 |
1991年 | 54篇 |
1990年 | 63篇 |
1989年 | 45篇 |
1988年 | 41篇 |
1987年 | 35篇 |
1986年 | 48篇 |
1985年 | 50篇 |
1984年 | 49篇 |
1983年 | 47篇 |
1982年 | 33篇 |
1981年 | 25篇 |
1980年 | 34篇 |
1979年 | 29篇 |
1978年 | 38篇 |
1977年 | 38篇 |
1976年 | 35篇 |
1975年 | 38篇 |
1974年 | 30篇 |
排序方式: 共有8641条查询结果,搜索用时 15 毫秒
151.
152.
153.
Jason E. Anton Kristine L. Vernon Dale E. Kelley John R. Gibbons Glen Birrenkott Chris J. Mortensen 《Journal of Equine Veterinary Science》2014
Our previous research has demonstrated moderate exercise can be detrimental to early pregnancy in the mare, but little work has examined exercise after pregnancy has been detected. We exercised mares (n = 8) 6 days a week for 45 min from Day 16 until Day 80 of gestation. Color Doppler ultrasonography was used to evaluate embryonic vesicle size, fetal length, and uterine blood flow. Blood was sampled every other day to analyze cortisol and progesterone concentrations. Results indicated that exercising pregnant mares (n = 4) led to greater (P < .01) cortisol concentrations 30 min after the exercise period. No overall treatment effect could be detected in progesterone concentrations; however, following Day 60 of gestation, progesterone concentrations were lower (P < .05) in exercised mares. Additionally, progesterone concentrations peaked earlier in exercised mares at Day 52 of gestation compared to peak levels at Day 68 of gestation for control mares. No significant effects were detected in embryonic vesicle size. Fetal length tended (P = .06) to be longer in the conceptus of exercised mares. Uterine blood flow did not differ between groups but increased as pregnancy progressed (P < .001) in both groups. All mares in this study went on to deliver healthy foals and suffered no difficulties during parturition. These results indicated that moderate exercise was not detrimental to mare pregnancy. 相似文献
154.
Yanlong Pei Valeria R. Parreira Kenneth L. Roland Roy Curtiss III John F. Prescott 《Canadian journal of veterinary research》2014,78(1):23-30
Salmonella hold considerable promise as vaccine delivery vectors for heterologous antigens in chickens. Such vaccines have the potential additional benefit of also controlling Salmonella infection in immunized birds. As a way of selecting attenuated strains with optimal immunogenic potential as antigen delivery vectors, this study screened 20 novel Salmonella Typhimurium vaccine strains, differing in mutations associated with delayed antigen synthesis and delayed attenuation, for their efficacy in controlling colonization by virulent Salmonella Typhimurium, as well as for their persistence in the intestine and the spleen. Marked differences were observed between strains in these characteristics, which provide the basis for selection for further study as vaccine vectors. 相似文献
155.
Darabighane Babak Mirzaei Aghjehgheshlagh Farzad Mahdavi Ali Navidshad Bahman Bernard John K. 《Tropical animal health and production》2020,52(5):2359-2369
Tropical Animal Health and Production - Corn gluten feed (CGF) is a co-product of wet milling that can replace energy or fiber ingredients in dairy cow rations. The present meta-analysis examines... 相似文献
156.
Jennifer J D'Agostino Gary West Dawn M Boothe Prashanth K Jayanna Timothy Snider John P Hoover 《Journal of zoo and wildlife medicine》2007,38(1):51-54
Parasitism is common in wild and captive amphibians; however, pharmacologic data are lacking for anthelmintic drugs. This study was developed to determine the plasma pharmacokinetics of selamectin after topical administration in bullfrogs. Thirty-two adult American bullfrogs (Rana catesbeiana) were randomly assigned into eight groups of four with each group representing a different collection time point. Seven groups received selamectin (6 mg/ kg) topically and the remaining group served as the untreated control group. One group of frogs was euthanized and blood samples immediately collected on days 0 (control), 1, 5, 10, 15, 20, 25, and 30. Plasma was analyzed for selamectin using high performance liquid chromatography with fluorescence detection. Individual samples were analyzed, then data were reported as the mean of the four frogs at each time point. A histologic evaluation of the lung, liver, kidney, and skin tissues was performed and none of the frogs showed histologic evidence of toxicity due to selamectin administration. The mean peak plasma concentration was 162.5 +/- 42.3 ng/ml, area under the curve was 2,856 ng day/ml, mean residence time was 12.2 days, and disappearance half-life was 1.87 days. Based on the plasma pharmacokinetics, bullfrogs appear to absorb selamectin very efficiently, concentrations reach high levels in the plasma, and there were no apparent histologic effects from single dose administration. 相似文献
157.
Jessica Siegal-Willott Darryl Heard Naime Sliess Diane Naydan John Roberts 《Journal of zoo and wildlife medicine》2007,38(2):352-356
Microchips are commonly used in companion, research, and zoo animal medicine for easy, reliable, and cost-effective identification with relatively low risk of side effects. This report describes development of a metastatic leiomyosarcoma associated with a microchip in an Egyptian fruit bat (Rousettus aegyptiacus). 相似文献
158.
Bauer JE 《Journal of the American Veterinary Medical Association》2007,231(11):1657-1661
Long-chain omega-3 fatty acids from fish oil and other marine sources appear to be capable of modifying inflammatory and immune responses in dogs. Information is provided on the capacity of dogs to metabolize omega-3 fatty acids and the effects of omega-3 fatty acids on skin and coat, inflammatory responses, and neurologic development in puppies. 相似文献
159.
An e-mail/telephone survey of all active North American residency training programs in veterinary pathology was conducted in September 2005. The purpose of this survey was to determine current numbers of trainees, their program length and type, and salaries; to compare current numbers to five years earlier; and, finally, to gauge interest in expanding current programs. All 41 training institutions contacted responded to the survey. Briefly, the survey found that there are currently 235 veterinary pathology residents, for a mean of 5.7 residents per training program. The number of residents currently in training programs and the number of applicants for these programs has increased compared to five years earlier. There is widespread interest in further expanding capacity in these programs, and the coalition of the American College of Veterinary Pathologists and the Society of Toxicologic Pathology is a well-known source of possible funding for additional residents. This survey report further documents the numbers of combined residency/PhD programs, average starting salaries for new residents, outside sponsorship effects on pathology training programs, and some of the common concerns regarding veterinary pathology training programs voiced by the respondents. While residency training capacity has expanded in the last five years, and there is widespread desire to further expand these training programs, a shortage of veterinary pathologists for future market needs will need to be addressed by increased funding from as yet unspecified sources. 相似文献
160.
Ritter MJ Perry RL Olivier NB Kim SY Dejardin LM 《Journal of the American Animal Hospital Association》2007,43(2):93-98
A novel technique was developed to estimate the caudal medial tibial plateau landmark in the face of osteophytosis to improve accuracy in tibial plateau angle measurements. Using this technique, tibial plateau angles were evaluated in 31 normal dogs before and 8 months after right cranial cruciate ligament transection. There was no significant difference in mean tibial plateau angle before or after induction of osteophytosis. Additionally, it was determined that 90% of dogs had a difference of =2 degrees between right and left tibial plateau angles, which was considered symmetrical. 相似文献