全文获取类型
收费全文 | 1573篇 |
免费 | 97篇 |
国内免费 | 1篇 |
专业分类
林业 | 142篇 |
农学 | 220篇 |
基础科学 | 23篇 |
302篇 | |
综合类 | 47篇 |
农作物 | 88篇 |
水产渔业 | 46篇 |
畜牧兽医 | 607篇 |
园艺 | 67篇 |
植物保护 | 129篇 |
出版年
2023年 | 14篇 |
2022年 | 22篇 |
2021年 | 32篇 |
2020年 | 35篇 |
2019年 | 26篇 |
2018年 | 74篇 |
2017年 | 64篇 |
2016年 | 74篇 |
2015年 | 41篇 |
2014年 | 47篇 |
2013年 | 124篇 |
2012年 | 60篇 |
2011年 | 77篇 |
2010年 | 57篇 |
2009年 | 50篇 |
2008年 | 69篇 |
2007年 | 56篇 |
2006年 | 46篇 |
2005年 | 40篇 |
2004年 | 36篇 |
2003年 | 45篇 |
2002年 | 43篇 |
2001年 | 32篇 |
2000年 | 26篇 |
1999年 | 31篇 |
1998年 | 17篇 |
1997年 | 10篇 |
1996年 | 18篇 |
1995年 | 15篇 |
1994年 | 11篇 |
1993年 | 15篇 |
1992年 | 19篇 |
1991年 | 20篇 |
1990年 | 31篇 |
1989年 | 21篇 |
1988年 | 16篇 |
1987年 | 20篇 |
1986年 | 17篇 |
1985年 | 17篇 |
1984年 | 11篇 |
1983年 | 12篇 |
1982年 | 14篇 |
1981年 | 17篇 |
1980年 | 14篇 |
1979年 | 21篇 |
1978年 | 15篇 |
1977年 | 11篇 |
1970年 | 8篇 |
1969年 | 14篇 |
1968年 | 12篇 |
排序方式: 共有1671条查询结果,搜索用时 359 毫秒
1.
2.
3.
4.
Computed Tomographic Angiography of the Pancreas in Cats with Chronic Diabetes Mellitus Compared to Normal Cats 下载免费PDF全文
S. Secrest A. Sharma A. Bugbee 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2018,32(3):962-966
Background
Diabetes mellitus (DM) is a common endocrinopathy in cats. No known diagnostic test or patient characteristic at the time of diagnosis can predict likely disease course, unlike in people in whom computed tomographic angiography (CTA) is used. No published data exist regarding the CTA appearance of the pancreas in cats with DM, and thus, it is unknown what if any CTA variables should be further assessed for associations with pancreatic endocrine function.Hypothesis/Objectives
A significant difference in pancreatic attenuation, volume, and size will be identified between normal cats and those with chronic DM on CTA.Animals
Ten healthy control cats and 15 cats with naturally occurring DM present for >12 months.Methods
Prospective cross‐sectional study comparing pancreatic attenuation, enhancement pattern, size, volume, pancreatic volume‐to‐body weight ratio (V:BW), pancreatic arterial: portal phase ratio (A:P), time‐to‐arterial enhancement, and time‐to‐peak portal enhancement on CTA between sedated healthy control cats and those with chronic DM.Results
The pancreas in cats with chronic DM was significantly larger, had higher volume, higher V:BW, and shorter time‐to‐peak portal enhancement on CTA when compared to normal cats.Conclusions and Clinical Importance
Peak portal enhancement time, pancreatic size, pancreatic volume, and V:BW can be used to differentiate normal sedated cats from those with chronic DM by CTA. These variables warrant further investigation to identify possible associations with endocrine function. 相似文献5.
A survey of northern Victorian dairy farmers to investigate dairy calf management: colostrum feeding and management 下载免费PDF全文
Objectives
To describe colostrum management practices carried out in northern Victorian dairy herds and to identify weaknesses in these areas that may affect calf health and welfare by comparing the results with the current industry recommendationsMethods
A questionnaire to obtain information about colostrum management and calf‐rearing practices was sent to commercial dairy farming clients of Rochester Veterinary Practice between June and September 2013. The questionnaire consisted of a general herd overview and colostrum harvesting practices.Results
The response rate was 39% (58/150). Many dairy producers were not meeting the current industry recommendations in the following areas: (1) time of removal calf from the dam, (2) relying on calf suckling colostrum from the dam to achieve adequate passive transfer, (3) failing to supplement calves with colostrum, (4) feeding inadequate volumes of colostrum, (5) delayed colostrum harvesting, (6) pooling of colostrum, (7) failing to objectively assess colostrum quality or relying on visual assessment and (8) storing colostrum for a prolonged periods of time at ambient temperatures.Conclusion
The results from this survey highlight the need for greater awareness of industry standards for colostrum management and feeding hygiene.6.
7.
8.
9.
S. Shanmugam K. H. Kjaer C.‐O. Ottosen E. Rosenqvist D. Kumari Sharma B. Wollenweber 《Journal of Agronomy and Crop Science》2013,199(5):340-350
This study analysed the alleviating effect of elevated CO2 on stress‐induced decreases in photosynthesis and changes in carbohydrate metabolism in two wheat cultivars (Triticum aestivum L.) of different origin. The plants were grown in ambient (400 μl l?1) and elevated (800 μl l?1) CO2 with a day/night temperature of 15/10 °C. At the growth stages of tillering, booting and anthesis, the plants were subjected to heat stress of 40 °C for three continuous days. Photosynthetic parameters, maximum quantum efficiency of photosystem II (PSII) photochemistry (Fv/Fm) and contents of pigments and carbohydrates in leaves were analysed before and during the stress treatments as well as after 1 day of recovery. Heat stress reduced PN and Fv/Fm in both wheat cultivars, but plants grown in elevated CO2 maintained higher PN and Fv/Fm in comparison with plants grown in ambient CO2. Heat stress reduced leaf chlorophyll contents and increased leaf sucrose contents in both cultivars grown at ambient and elevated CO2. The content of hexoses in the leaves increased mainly in the tolerant cultivar in response to the combination of elevated CO2 and heat stress. The results show that heat stress tolerance in wheat is related to cultivar origin, the phenological stage of the plants and can be alleviated by elevated CO2. This confirms the complex interrelation between environmental factors and genotypic traits that influence crop performance under various climatic stresses. 相似文献
10.
Identification of internal control genes in milk‐derived mammary epithelial cells during lactation cycle of Indian zebu cow 下载免费PDF全文