全文获取类型
收费全文 | 844篇 |
免费 | 62篇 |
国内免费 | 132篇 |
专业分类
林业 | 110篇 |
农学 | 115篇 |
基础科学 | 27篇 |
160篇 | |
综合类 | 303篇 |
农作物 | 24篇 |
水产渔业 | 96篇 |
畜牧兽医 | 139篇 |
园艺 | 23篇 |
植物保护 | 41篇 |
出版年
2024年 | 2篇 |
2023年 | 11篇 |
2022年 | 32篇 |
2021年 | 33篇 |
2020年 | 39篇 |
2019年 | 31篇 |
2018年 | 26篇 |
2017年 | 52篇 |
2016年 | 46篇 |
2015年 | 39篇 |
2014年 | 58篇 |
2013年 | 54篇 |
2012年 | 61篇 |
2011年 | 55篇 |
2010年 | 40篇 |
2009年 | 56篇 |
2008年 | 57篇 |
2007年 | 40篇 |
2006年 | 33篇 |
2005年 | 33篇 |
2004年 | 23篇 |
2003年 | 25篇 |
2002年 | 24篇 |
2001年 | 23篇 |
2000年 | 18篇 |
1999年 | 14篇 |
1998年 | 15篇 |
1997年 | 12篇 |
1996年 | 13篇 |
1995年 | 7篇 |
1994年 | 16篇 |
1993年 | 13篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 3篇 |
1980年 | 2篇 |
1979年 | 1篇 |
排序方式: 共有1038条查询结果,搜索用时 15 毫秒
71.
72.
73.
Masayuki?Takahashi Takeshi?Yamamoto Sanae?Kato Kunihiko?KonnoEmail author 《Fisheries Science》2005,71(3):662-671
ABSTRACT: The effect of salt concentration on the thermal denaturation profile of myosin in walleye pollack and carp myofibrils was compared by studying the subfragment-1 (S-1) and rod denaturation rates upon heating. Species-specific denaturation mode observed at 0.1 M KCl was no longer detected when samples were heated above 0.5 M KCl, where S-1 and rod denaturation rates were identical to each other. As the heating of the chymotryptic digest of myofibril formed practically no rod aggregates, S-1 denaturation in a form of myosin was the rate limiting step for rod aggregate formation. As the aggregate formation by rod was remarkably suppressed by lowering the temperature, the free movement of myosin tail upon heating was suggested to play an important role in the rod aggregate formation in a high salt medium. 相似文献
74.
茄子冷冻干燥冻结过程模型的建立与求解 总被引:3,自引:3,他引:0
该文以茄子球形样本为对象,研究果蔬物料冷冻干燥中预冻模型的建立及求解方法。通过能量衡算建立了果蔬冻结过程的非稳态数学模型,依据冻结过程试验参数,给出了冻结过程中物料液相区和固相区温度变化所满足的定解问题。采用“欧拉向后差分格式”数值计算方法,对冻结模型进行了数值求解,得出了茄子在冻结过程中冻结界面的移动规律和冻结时间。试验结果表明,所建模型能够准确地描述茄子的冻结过程,采用的数值解法是可行的。该文研究方法及结果为果蔬物料冷冻干燥预冻结过程模型的建立与求解提供了参考,并为果蔬冷冻干燥预冻结过程的优化控制提供了科学依据。 相似文献
75.
76.
The post-thaw motility and the acrosome integrity of semen from 4 boars frozen with a programmable freezing machine, in mini (0.25 ml) and maxi (5 ml) plastic straws and in 10 x 5 cm Teflon FEP-plastic bags (0.12 mm thick, 5 ml), were compared. The freezing of the semen was monitored by way of thermo-couples placed in the straws and the bags. Three freezing programmes were used, namely A: from +5 degrees C, at a rate of 3 degrees C/min, to -6 degrees C, held for 1 min at -6 degrees C, and followed by a cooling rate of 20 degrees C/min to -100 degrees C; B: a similar curve except that there was no holding time at -6 degrees C and that the cooling rate was 30 degrees C/min, and C: from +5 degrees C to -100 degrees C, with a cooling rate of 35 degrees C/min, followed by storage in liquid N2. Despite the freezing curve assayed, both the mini-straws and the bags depicted much shorter freezing point plateaus as compared to the maxi-straws. Post-thaw sperm motility as well as the amount of normal apical ridges were equally significantly higher when semen was frozen in mini-straws or in bags than in maxi-straws. Significant differences in these post-thawing parameters were obtained between the freezing curves used. The stepwise freezing procedure A appeared as the best alternative for boar semen, considering this in vitro evaluation. 相似文献
77.
78.
79.
80.