全文获取类型
收费全文 | 328篇 |
免费 | 23篇 |
专业分类
林业 | 19篇 |
农学 | 16篇 |
37篇 | |
综合类 | 53篇 |
农作物 | 1篇 |
水产渔业 | 3篇 |
畜牧兽医 | 214篇 |
园艺 | 2篇 |
植物保护 | 6篇 |
出版年
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 6篇 |
2017年 | 3篇 |
2016年 | 11篇 |
2015年 | 9篇 |
2014年 | 5篇 |
2013年 | 11篇 |
2012年 | 7篇 |
2011年 | 8篇 |
2010年 | 9篇 |
2009年 | 9篇 |
2008年 | 17篇 |
2007年 | 9篇 |
2006年 | 24篇 |
2005年 | 12篇 |
2004年 | 11篇 |
2003年 | 16篇 |
2002年 | 14篇 |
2001年 | 9篇 |
2000年 | 14篇 |
1999年 | 11篇 |
1998年 | 14篇 |
1997年 | 12篇 |
1996年 | 7篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1983年 | 4篇 |
1980年 | 4篇 |
1978年 | 3篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1942年 | 2篇 |
1914年 | 2篇 |
1910年 | 2篇 |
1909年 | 4篇 |
1898年 | 2篇 |
排序方式: 共有351条查询结果,搜索用时 140 毫秒
1.
2.
The structure of liquid water is described by three atom pair distribution functions gOO(r), gOH(r), and gHH(r). These functions have now been derived from neutron diffraction data on four mixtures of light and heavy water. They will provide a crucial and sensitive test for proposed models of liquid water. 相似文献
3.
4.
5.
Musser RE Goodband RD Tokach MD Owen KQ Nelssen JL Blum SA Campbell RG Smits R Dritz SS Civis CA 《Journal of animal science》1999,77(12):3296-3303
Sows of differing parities and genetics were used at different locations to determine the effects of feeding added L-carnitine during lactation on sow and litter performance. In Exp. 1, sows (n = 50 PIC C15) were fed a lactation diet (1.0% total lysine, .9% Ca, and .8% P) with or without 50 ppm of added L-carnitine from d 108 of gestation until weaning (d 21). No differences in litter weaning weight, survivability, sow ADFI, or sow weight and last rib fat depth change were observed. Number of pigs born alive in the subsequent farrowing were not different (P>.10). In Exp. 2, parity-three and -four sows (n = 115 Large White cross) were used to determine the effect of feeding 0, 50, 100, or 200 ppm of added L-carnitine during lactation (diet containing .9% total lysine, 1.0% Ca, and .8% P) on sow and litter performance. No improvements in the number of pigs or litter weights at weaning were observed (P>.10). Sows fed added L-carnitine had increased weight loss (linear; P<.04), but no differences (P>.10) were observed in last rib fat depth change or subsequent reproductive performance. In Exp. 3, first-parity sows (n = 107 PIC C15) were fed a diet with or without 50 ppm of added L-carnitine during lactation (diet containing 1.0% total lysine). Sows fed added L-carnitine tended (P<.10) to have fewer stillborn and mummified pigs than controls (.42 vs .81 pigs). No differences were observed for litter weaning weight, survivability, or subsequent farrowing performance. Feeding 50 to 200 ppm of added L-carnitine during lactation had little effect on sow and litter performance. 相似文献
6.
Pregnancy detection in cows by pulse mode ultrasound
Two commercially available pulse mode ultrasound instruments for pregnancy detection in cows were examined by testing 50 pregnant Friesian cows twice weekly. Absolutely reliable results were obtained after d 181 ("Cow-Tone") and d 221 of pregnancy (Preg-Alert 7 respectively. A newly constructed instrument ("HK-Rheintechnik") operating with greater wavelength (0,7 MHz) was tested in a similar fashion on 62 pregnant cows. Zt produced absolutely reliable results from d 135 of pregnancy on, i.e. 46 days sooner than the best of the commercial instruments tested . 相似文献
Two commercially available pulse mode ultrasound instruments for pregnancy detection in cows were examined by testing 50 pregnant Friesian cows twice weekly. Absolutely reliable results were obtained after d 181 ("Cow-Tone") and d 221 of pregnancy (Preg-Alert 7 respectively. A newly constructed instrument ("HK-Rheintechnik") operating with greater wavelength (0,7 MHz) was tested in a similar fashion on 62 pregnant cows. Zt produced absolutely reliable results from d 135 of pregnancy on, i.e. 46 days sooner than the best of the commercial instruments tested . 相似文献
7.
The ant Iridomyrmex pruinosus utilizes 2-heptanone as an alarm pheromone. The activities of 49 ketones and 35 nonketones as alarm pheromones for this species were determined. The molecular shapes of these compounds were assessed by submitting silhouette photographs of their molecular models to a pattern recognition machine. A highly significant correlation exists between molecular shape and alarm activity. 相似文献
8.
9.
10.
Georgieva TM Georgiev IP Ontsouka E Hammon HM Pfaffl MW Blum JW 《Journal of animal science》2003,81(9):2294-2300
The somatotropic axis and insulin are involved in pre- and postnatal development. In pre- and full-term calves (GrP0 and GrN0; born after 277 and 290 d of pregnancy, respectively) and in preterm calves on d 8 of life after being fed for 7 d (GrP8), we studied whether there are differences in the abundance of messenger RNA (mRNA) of IGF-I and IGF-II and of receptors for GH, IGF-I, IGF-II, and insulin among different intestinal sites (duodenum, jejunum, ileum, and colon) and whether there are ontogenetic differences during the perinatal period in intestine and liver. Intestinal site differences (P < 0.05) existed in mRNA levels of IGF-I and IGF-II and receptors for GH, IGF-I, IGF-II, and insulin. Abundance of mRNA of IGF-I and -II and of receptors for IGF-I and GH was highest (P < 0.05) in the colon, abundance of the receptor for IGF-II was comparably high in the colon and ileum, and that of the receptor for insulin was similarly high in colon, ileum, and jejunum. Among GrP0, GrN0, and GrP8 groups, there were differences (P < 0.05) in mRNA levels of IGF-I and IGF-II and of receptors for GH, IGF-I, IGF-II and insulin. Abundance of mRNA of IGF-I and IGF-II and of receptors for GH, IGF-I, IGF-II and insulin was highest (P < 0.05) in GrP0 calves immediately after birth and was primarily seen in the ileum. In liver, the mRNA levels differed (P < 0.05) among groups for IGF-II and receptors for IGF-I, IGF-II, and insulin, and were highest (P < 0.05) for IGF-II in GrP0, for receptors of IGF-I in GrN0, and were higher (P < 0.05) in GrP0 than GrP8 for receptors of IGF-II. In conclusion, mRNA levels of IGF-I and IGF-II and of receptors for GH, IGF-I, IGF-II, and insulin were different at different intestinal sites and in intestine and liver and changed during the perinatal period. 相似文献