全文获取类型
收费全文 | 790篇 |
免费 | 52篇 |
国内免费 | 3篇 |
专业分类
林业 | 13篇 |
农学 | 7篇 |
基础科学 | 1篇 |
67篇 | |
综合类 | 105篇 |
农作物 | 28篇 |
水产渔业 | 22篇 |
畜牧兽医 | 547篇 |
园艺 | 6篇 |
植物保护 | 49篇 |
出版年
2023年 | 8篇 |
2021年 | 8篇 |
2020年 | 12篇 |
2019年 | 13篇 |
2018年 | 17篇 |
2017年 | 15篇 |
2016年 | 20篇 |
2015年 | 6篇 |
2014年 | 29篇 |
2013年 | 38篇 |
2012年 | 29篇 |
2011年 | 44篇 |
2010年 | 20篇 |
2009年 | 30篇 |
2008年 | 26篇 |
2007年 | 35篇 |
2006年 | 33篇 |
2005年 | 25篇 |
2004年 | 19篇 |
2003年 | 27篇 |
2002年 | 25篇 |
2001年 | 30篇 |
2000年 | 25篇 |
1999年 | 24篇 |
1998年 | 16篇 |
1997年 | 16篇 |
1996年 | 17篇 |
1995年 | 14篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 19篇 |
1991年 | 10篇 |
1990年 | 10篇 |
1989年 | 22篇 |
1988年 | 9篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1983年 | 5篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1972年 | 7篇 |
1971年 | 5篇 |
1970年 | 7篇 |
1969年 | 7篇 |
1968年 | 10篇 |
1967年 | 4篇 |
1966年 | 3篇 |
1934年 | 4篇 |
排序方式: 共有845条查询结果,搜索用时 15 毫秒
111.
112.
113.
114.
115.
116.
Uterus didelphys is a rare congenital abnormality of the reproductive tract. Although it occurs in various species, there are no published reports describing pregnancy outcome in association with this abnormality. Herein we describe a case of successful unilateral singleton pregnancy in a ewe incidentally found to have uterus didelphys during the course of a biomedical research study. The pregnancy was established using assisted reproductive techniques and interrupted in late gestation, at which point the abnormality was identified. Serial ultrasound assessment of foetal biometry revealed a normal foetal growth trajectory. Despite a 45% reduction in placentome number, total placentome weight was near normal secondary to compensatory placentome growth and development. To our knowledge, this is the first detailed report of normal foetal growth in an animal with uterus didelphys and illustrates the ability of the ovine placenta to adapt to a reduced number of placentomes and maintain foetal nutrient supply. 相似文献
117.
GU-PCM2型控温式相变蓄冷冷藏车设计与空载性能试验 总被引:2,自引:2,他引:0
现有蓄冷冷藏车蓄冷装置多位于车厢顶部,存在重心偏高、不可控温等问题,基于此,该文设计了一款集相变蓄冷单元、车载制冷系统、隔热车厢、送风系统等于一体的GU-PCM2型蓄冷冷藏车。该蓄冷车将蓄冷装置独立设置于车厢前端并保温,系统利用夜间低谷电进行充冷,可在-25~10℃之间根据需要调控车厢温度。对蓄冷冷藏车厢设定温度为0和-18℃的2种工况进行空载温度场仿真与测试。结果表明,车厢内各测温点的模拟温度与实测温度均方根误差分别为0.7和0.8℃,最大绝对误差分别为1.1和1.2℃。冷藏车可有效控温10 h以上,车厢平均温度分别在1.1~2.9℃和-14.8~-16.9℃之间,波动范围为1.8和2.1℃,温度不均匀度系数在1.0以内。控温式蓄冷冷藏车与传统蓄冷车的对比试验结果表明,其平均温度波动值降低48.7%,温度绝对不均匀度系数降低50%以上,车厢质心较顶置式蓄冷车下降25.9%。研究结果可为蓄冷冷藏车的进一步优化设计与应用提供参考。 相似文献
118.
Mokwe-Ozonzeadi Ngozi Foster Ian Valsami-Jones Eugenia McEldowney Sharron 《Journal of Soils and Sediments》2019,19(2):946-963
Journal of Soils and Sediments - This study aims to identify a suitable sediment compartment for sediment quality monitoring by: (a) studying the concentration of trace metals (Cd, Cu, Ni, Pb and... 相似文献
119.
C Almiñana MA Gil C Cuello I Caballero J Roca JM Vazquez EA Martinez 《Reproduction in domestic animals》2008,43(6):747-752
The present study was designed to evaluate three different in vitro fertilization (IVF) systems: a straw‐IVF system with 10 min of coincubation, a straw‐IVF system with 6‐h coincubation and the microdrop‐IVF system with 6‐h coincubation (the traditional IVF system used routinely in most of IVF laboratories) in an attempt to reduce polyspermic penetration ( Experiment 1 ). When the straw‐IVF system was tested in combination with two coincubation times, the use of 10 min of coincubation significantly increased (p < 0.001) the penetration rate and the efficiency of fertilization (67.7 ± 6.4% vs 31.9 ± 6.5% and 41.5 ± 2.5% vs 17.6 ± 2.5% for 10 min and 6 h, respectively), while there were no significant differences in the incidence of monospermy between both systems (64.3 ± 5.1% and 67.7 ± 3.4%, for 10 min and 6 h, respectively). The penetration rate in the 6‐h microdrop‐IVF system was higher (93.8 ± 3.6%; p < 0.001) compared with the 10‐min straw‐IVF system (67.7 ± 6.4%), however, monospermy was severely reduced (25.0 ± 4.3% vs 67.7 ± 3.4%, for the 6‐h microdrop‐IVF system and 10‐min straw‐IVF system, respectively). The efficiency of the IVF showed similar values between microdrop and 6‐h straw‐IVF systems, but efficiency was significantly improved (p < 0.05) when the 10‐min straw‐IVF system was used. Experiment 2 was designed to compare porcine in vitro embryo production in two IVF systems, the 6‐h microdrop‐IVF system (1000 sperm per oocyte) and 10‐min straw‐IVF system (30 000 sperm per oocyte). The blastocyst formation rates tended (p = 0.06) to be higher when the 10‐min straw‐IVF system was used compared with the 6‐h microdrop‐IVF system. In addition, the number of total cells per blastocyst increased significantly (p < 0.05) in the 10‐min straw‐IVF system. These results showed that the 10‐min straw‐IVF system is an effective way to decrease polyspermic penetration, and improve the efficiency of fertilization and the quality of blastocysts in terms of cell number per embryo. 相似文献
120.