全文获取类型
收费全文 | 169227篇 |
免费 | 22257篇 |
国内免费 | 33421篇 |
专业分类
林业 | 18794篇 |
农学 | 22042篇 |
基础科学 | 15689篇 |
43407篇 | |
综合类 | 64367篇 |
农作物 | 11500篇 |
水产渔业 | 9021篇 |
畜牧兽医 | 22080篇 |
园艺 | 6382篇 |
植物保护 | 11623篇 |
出版年
2024年 | 1265篇 |
2023年 | 2305篇 |
2022年 | 4816篇 |
2021年 | 5703篇 |
2020年 | 6677篇 |
2019年 | 9398篇 |
2018年 | 8105篇 |
2017年 | 10062篇 |
2016年 | 10006篇 |
2015年 | 11116篇 |
2014年 | 10484篇 |
2013年 | 12021篇 |
2012年 | 13274篇 |
2011年 | 12842篇 |
2010年 | 11493篇 |
2009年 | 10384篇 |
2008年 | 8990篇 |
2007年 | 9373篇 |
2006年 | 8498篇 |
2005年 | 7597篇 |
2004年 | 4636篇 |
2003年 | 4032篇 |
2002年 | 3466篇 |
2001年 | 3253篇 |
2000年 | 3395篇 |
1999年 | 3636篇 |
1998年 | 3299篇 |
1997年 | 2937篇 |
1996年 | 2685篇 |
1995年 | 2709篇 |
1994年 | 2462篇 |
1993年 | 2107篇 |
1992年 | 1975篇 |
1991年 | 1622篇 |
1990年 | 1356篇 |
1989年 | 1117篇 |
1988年 | 942篇 |
1987年 | 693篇 |
1986年 | 523篇 |
1985年 | 263篇 |
1984年 | 245篇 |
1983年 | 231篇 |
1982年 | 218篇 |
1981年 | 268篇 |
1980年 | 206篇 |
1979年 | 157篇 |
1978年 | 132篇 |
1975年 | 109篇 |
1965年 | 139篇 |
1964年 | 142篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
前期研究中通过对秀珍菇经低温诱导后不同发育阶段样本进行转录组测序及差异表达基因分析发现,ID为Cluster-6377.64510的基因(命名为PpFBD1)在原基形成前期的样本中高表达。为进一步了解分析其表达特性及功能,根据转录组测序结果设计特异性引物,利用RT-PCR技术从秀珍菇中克隆获得了该基因的cDNA全长。该基因由342个核苷酸组成,编码一个由113个氨基酸组成的蛋白,蛋白相对分子质量约11 ku。进化树分析显示,PpFBD1编码蛋白与糙皮侧耳hydrophobin1编码的疏水蛋白亲缘关系最近。Gene Ontology功能分析表明,PpFBD1主要参与真菌类细胞壁的合成。荧光定量RT-PCR检测显示,该基因在菌丝体经低温诱导后恢复至室温阶段(原基形成前期)表达量最高,这表明其可能参与调控秀珍菇原基形成过程。本研究结果为阐明秀珍菇原基形成机制提供参考。 相似文献
53.
54.
Fang Chen Hao Zhang Na Zhao Xuehai Yang Encun Du Shaowen Huang Wanzheng Guo Wei Zhang Jintao Wei 《Animal Science Journal》2021,92(1):e13619
Heat stress in poultry is deleterious to productive performance. Chlorogenic acid (CGA) exerts antibacterial, anti-inflammatory, and antioxidant properties. This study was conducted to evaluate the effects of dietary supplemental CGA on the intestinal health and cecal microbiota composition of young hens challenged with acute heat stress. 100-day-old Hy-line brown pullets were randomly divided into four groups. The control group (C) and heat stress group (HS) received a basal diet. HS + CGA300 group and HS + CGA600 group received a basal diet supplemented with 300- and 600-mg/kg CGA, respectively, for 2 weeks before heat stress exposure. Pullets of HS, HS + CGA300, and HS + CGA600 group were exposed to 38°C for 4 h while the control group was maintained at 25°C. In this study, dietary CGA supplementation had effect on mitigate the decreased T-AOC and T-SOD activities and the increasing of IL-1β and TNFα induced by acute heat stress. Dietary supplementation with 600 mg/kg CGA had better effect on increasing the relative abundance of beneficial bacterial genera, such as Rikenellaceae RC9_gut_group, Ruminococcaceae UCG-005, and Christensenellaceae R-7_group, and deceasing bacteria genera involved in inflammation, such as Sutterella species. Therefore, CGA can ameliorate acute heat stress damage through suppressing inflammation and improved antioxidant capacity and cecal microbiota composition. 相似文献
55.
56.
57.
聚丙烯酰胺凝胶电泳法鉴定禽呼肠孤病毒 总被引:1,自引:0,他引:1
从感染禽呼肠孤病毒的细胞中,以SDS和酚提取病毒核酸,通过聚丙烯酰胺凝胶电泳(PAGE)法将分节段的核酸分开,经银染色显示,呈3-3-1-3分布,此法可用于禽呼肠孤病毒的快速检测、鉴定。同样方法未能使传染性法氏囊病毒核酸显示。 相似文献
58.
本文考虑一类耗散非线性波动方程的初边值问题。用半(?)方法和先验估计论证了该问题小初值下在时间大范围的可解性、唯一性;并用凸性方法证明了(?)当条件下该问题的解在有限时间内发生爆破现象。 相似文献
59.
阐述了某工程由于施工原因,导致预应力混凝土工字形屋面梁强度不足的预制构件的检验鉴定过程和方法。采用回弹法推定混凝土实际强度;通过静载试验测试构件的实际挠度、抗裂和承载能力。分析了导致混凝土强度不足的原因。 相似文献
60.
Evaluation of abomasal outflow diversion as an experimental model of hypochloremic, hypokalemic metabolic alkalosis in lactating cows. 下载免费PDF全文
J L Ward D F Smith S L Fubini D M Deuel-Aromando 《Canadian journal of veterinary research》1994,58(1):13-19
Four adult, lactating dairy cows were subjected to diversion (loss) of gastric contents through a T-shaped cannula placed in the cranial part of the duodenum just distal to the pylorus. Diversion was continued for 10 to 12 hours, at which point the cows were very weak and depressed. The volume of effluent during this period ranged from 37.3 to 46.8 L, with the largest volume being produced during the first four hours. All cows became dehydrated, with mean packed cell volume and total plasma protein concentration increasing 30% and 19.6%, respectively, but with only a slight increase in plasma creatinine concentration. Plasma Cl- concentrations decreased from a mean of 97.3 mEq/L at the beginning of diversion to a mean of 87.2 mEq/L at eight hours. This was followed by a plateau or slight increase in concentrations over the final hours of diversion. Plasma K+ concentration followed a similar pattern, decreasing from a mean of 3.9 mEq/L to a mean of 2.94 mEq/L at six hours, followed by increasing values until termination of diversion. No changes in plasma Na+ concentration were noted, except for a mild decrease in one cow. Plasma calcium concentrations decreased significantly, reaching 6.6 +/- 0.6 mEq/L at the end of diversion. Venous pH, plasma HCO3- concentration, and plasma base excess concentration increased during the first four to eight hours of diversion, followed by a gradual decline. Although a mild hypochloremic metabolic alkalosis resulted from diversion of abomasal outflow in all cows, substantiated by a mild increase in plasma strong ion difference, the changes observed were not as great as expected.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献