全文获取类型
收费全文 | 23012篇 |
免费 | 1142篇 |
国内免费 | 2635篇 |
专业分类
林业 | 2859篇 |
农学 | 3525篇 |
基础科学 | 1904篇 |
4097篇 | |
综合类 | 6468篇 |
农作物 | 1296篇 |
水产渔业 | 886篇 |
畜牧兽医 | 3313篇 |
园艺 | 729篇 |
植物保护 | 1712篇 |
出版年
2024年 | 41篇 |
2023年 | 205篇 |
2022年 | 508篇 |
2021年 | 855篇 |
2020年 | 776篇 |
2019年 | 736篇 |
2018年 | 533篇 |
2017年 | 755篇 |
2016年 | 732篇 |
2015年 | 998篇 |
2014年 | 918篇 |
2013年 | 1176篇 |
2012年 | 1403篇 |
2011年 | 1449篇 |
2010年 | 1436篇 |
2009年 | 1363篇 |
2008年 | 1261篇 |
2007年 | 1401篇 |
2006年 | 1293篇 |
2005年 | 1110篇 |
2004年 | 539篇 |
2003年 | 501篇 |
2002年 | 415篇 |
2001年 | 433篇 |
2000年 | 548篇 |
1999年 | 690篇 |
1998年 | 619篇 |
1997年 | 533篇 |
1996年 | 517篇 |
1995年 | 510篇 |
1994年 | 466篇 |
1993年 | 414篇 |
1992年 | 387篇 |
1991年 | 301篇 |
1990年 | 247篇 |
1989年 | 207篇 |
1988年 | 165篇 |
1987年 | 91篇 |
1986年 | 63篇 |
1985年 | 32篇 |
1984年 | 16篇 |
1983年 | 34篇 |
1982年 | 18篇 |
1981年 | 23篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1974年 | 9篇 |
1965年 | 6篇 |
1964年 | 6篇 |
1963年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
201.
202.
203.
前桥摆转转向式四驱底盘可直接转入下一畦作业,提高了小地块工作行程率,在地头宽度小于等于1个作业宽度时,更有利于机耕过程中的转向操作。为此,通过ADAMS软件仿真,以最小地头宽度为目标对底盘结构参数进行了优化。仿真结果表明,底盘在作业过程中从一畦进入地头直接转入相邻的下一畦时,后内侧轮基本上不吃入上一畦,最小地头宽度与长宽比成反比。在底盘转向时行走轮不干涉后悬挂农具的前提下,底盘最小的理论长宽比应为0.5:1。但由于底盘长宽比受行走轮直径、轮宽及重心的影响,底盘的合理长宽比值范围需趋近于理论长宽比。当机具作业宽幅大于等于机具轮宽时,可直接做倒U形转向;否则采用"4"和歪梨形组合掉头转向,实现地头宽度等于1个作业幅宽的转向。 相似文献
204.
205.
206.
207.
208.
Effects of dietary lysozyme levels on growth performance,intestinal morphology,non‐specific immunity and mRNA expression in weanling piglets 下载免费PDF全文
Jiatao Zhu Xiaoxue Pang Zhengfeng Fang Yan Lin Lianqiang Che Shengyu Xu Jian Li Yiming Huang Xiang Su De Wu 《Animal Science Journal》2016,87(3):411-418
The aim of the present study was to determine the effect of dietary lysozyme levels on growth performance, gut health and non‐specific immunity of weanling piglets. A total of 150 weanling piglets were allocated to six treatments. The piglets were fed the same basel diet supplemented with 0, 30, 60, 90 and 120 mg/kg lysozyme as well as antibiotics for 28 days. From day 14 to day 28 of dietary treatment, piglets fed 90 mg/kg lysozyme had greater average daily gain than piglets fed control diet. During the whole experimental period, piglets fed 120 mg/kg lysozyme tended to have greater average daily gain than piglets fed control diet. Compared with piglets fed control diet, piglets fed diets containing antibiotics and 90 mg/kg lysozyme had greater villus height to crypt depth ratio in duodenum and jejunum. Additionally, dietary supplementation of 60 and 90 mg/kg lysozyme as well as antibiotics enhanced the phagocytic activity of peritoneal macrophages in piglets. In conclusion, dietary lysozyme can accelerate the growth of weanling piglets by improving gut health and non‐specific immunity and supplementing 90 mg/kg lysozyme is as effective as antibiotics (20 mg/kg colistin sulphate + 50 mg/kg kitasamycin) in improving the growth performance of weanling piglets. 相似文献
209.
The distributions of Chinese yak breeds in response to climate change over the past 50 years 下载免费PDF全文
Jianguo Wu 《Animal Science Journal》2016,87(7):947-958
The effects of prior climate change on yak breed distributions are uncertain. Here, we measured changes in the distributions of 12 yak breeds over the past 50 years in China and examined whether the changes could be attributed to climate change. Long‐term records of yak breed distribution, grey relational analysis, fuzzy sets classification techniques and attribution methods were used. Over the past 50 years, the distributions of several yak breeds have changed in multiple directions, mainly shifting northward or westward, and most of these changes are related to the thermal index. Driven by climate change over the past years, the suitable range and the distribution centers of certain yak breeds have changed with fluctuation and have mainly shifted northward, eastward or southward. The consistency of observed versus predicted changes in distribution boundaries or distribution centers is higher for certain yak breeds. Changes in the eastern distribution boundary of two yak breeds over the past 50 years can be attributed to climate change. 相似文献
210.
Rearing conditions affected responses of weaned pigs to organic acids showing a positive effect on digestibility,microflora and immunity 下载免费PDF全文
Yalin Zhang Yumo Song Xiaoling Zhang Yan Lin Lianqiang Che Shengyu Xu De. Wu Bai Xue Zhengfeng Fang 《Animal Science Journal》2016,87(10):1267-1280
Three experiments were conducted to assess the response of weaned pigs to organic acid SF3, which contains 34% calcium formate, 16% calcium lactate, 7% citric acid and 13% medium chain fatty acids. Dietary treatments had no effect on growth performance of piglets (21‐day weaning) fed the commercial prestart diet for 1 week before receiving the experimental diets supplemented with SF3 at 0, 3 or 5 g/kg diet (Exp. 1), whereas diarrhea frequency averaged across a week was decreased by SF3 supplementation (5 g/kg diet) in piglets fed the experimental diets immediately after weaning (Exp. 2). In Exp. 3, piglets (28‐day weaning) were fed the control (containing pure colistin sulfate and enramycin, respectively, at 20 mg/kg diet) for 1 week and then were fed the control or SF3‐supplemented (5 g/kg diet) diet for 2 weeks. The SF3‐fed piglets had greater apparent ileal digestibility of calcium and dry matter, while also demonstrating greater overall gross energy, up‐regulated jejunal expression of sodium‐glucose cotransporter‐1 and transforming growth factor‐β, down‐regulated jejunal expression of tumor necrosis factor (TNF)‐α, higher ileal Lactobacillus, with lower total bacteria content, lower plasma TNF‐α but higher IgG levels than the control‐fed piglets. Collectively, SF3 consumption improved diarrhea resistance of weaned pigs by improving nutrient digestibility, piglet immunity and intestinal bacteria profile. © 2016 Japanese Society of Animal Science 相似文献