全文获取类型
收费全文 | 1472篇 |
免费 | 50篇 |
国内免费 | 108篇 |
专业分类
林业 | 141篇 |
农学 | 85篇 |
基础科学 | 16篇 |
87篇 | |
综合类 | 812篇 |
农作物 | 79篇 |
水产渔业 | 66篇 |
畜牧兽医 | 202篇 |
园艺 | 59篇 |
植物保护 | 83篇 |
出版年
2024年 | 10篇 |
2023年 | 28篇 |
2022年 | 46篇 |
2021年 | 42篇 |
2020年 | 35篇 |
2019年 | 43篇 |
2018年 | 23篇 |
2017年 | 58篇 |
2016年 | 58篇 |
2015年 | 66篇 |
2014年 | 60篇 |
2013年 | 92篇 |
2012年 | 121篇 |
2011年 | 113篇 |
2010年 | 112篇 |
2009年 | 114篇 |
2008年 | 112篇 |
2007年 | 97篇 |
2006年 | 77篇 |
2005年 | 56篇 |
2004年 | 34篇 |
2003年 | 24篇 |
2002年 | 21篇 |
2001年 | 21篇 |
2000年 | 20篇 |
1999年 | 31篇 |
1998年 | 15篇 |
1997年 | 5篇 |
1996年 | 16篇 |
1995年 | 17篇 |
1994年 | 10篇 |
1993年 | 11篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 13篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1978年 | 1篇 |
排序方式: 共有1630条查询结果,搜索用时 79 毫秒
1.
2.
3.
Pseudomonas fluorescens strain PfG32R, a potential biocontrol agent against soilborne pathogens, frequently loses its antifungal activity and ability
to produce enzymes. To characterize genetically the instability of these bacterial functions, we analyzed gacS and gacA genes of PfG32R and three spontaneous mutants of PfG32R (NR1, NR9, and ASW6), which had lost their ability to produce proteases
and antifungal activities. The gacS and gacA sequences of PfG32R had 77%–89% and 78%–87% homology, respectively, with several known gacS and gacA homologues. All three spontaneous mutants were subjected to complementation analysis. Introduction of clones containing an
intact gacS of PfG32R and another P. fluorescens strain Pf-5 as well as strain tea632 of P. syringae pv. theae complemented all three mutants restoring protease and antifungal activities, indicating a mutation in gacS. In sequencing analysis, the mutants had a deletion or change in amino acids in the conserved sensor kinase domains of GacS.
The three mutants maintained both their antibacterial activity against Ralstonia solanacearum and Clavibacter michiganensis ssp. michiganensis and siderophore production, indicating that they are not controlled by the GacS/GacA system.
The sequences reported in this article have been deposited in the DDBJ database under accession numbers AB219364 and AB219365. 相似文献
4.
吡咯伯克霍尔德氏菌JK-SH007的发酵条件及其对杨树溃疡病的防治效果 总被引:2,自引:0,他引:2
本文研究了拮抗细菌吡咯伯克霍尔德氏菌Burkholderia pyrrocinia菌株JK-SH007产抗菌物质的最佳发酵条件及其对杨树溃疡病的野外防治效果。结果表明,牛肉膏、蛋白胨是发酵培养基中最佳营养物质,有利于菌株JK-SH007抗菌物质的产生;培养基初始pH、培养时间、温度、培养体积、不同牛肉膏、蛋白胨组合等对菌株生长及其抗菌物质的产生有明显的影响,初始pH7、牛肉膏2g、蛋白胨20g、以1/2装液量装液、30℃振荡培养36h可获得较高产量的胞外分泌型抗菌物质;菌株JK-SH007的发酵液对杨树溃疡病的野外防效可达40.54%。 相似文献
5.
用盆栽法对原产于辽宁本溪的野菊(Dendranthema indicum)幼苗在自然干旱胁迫下的生理响应进行了研究。结果表明,渗透调节物可溶性蛋白含量处理期间一直低于对照,后期开始上升并接近对照;可溶性糖与之相反,处理前期急剧上升后期开始下降;丙二醛与相对电导率在处理期间都高于对照,随时间的延长,复水组逐渐接近对照;保护酶系统变化趋势比较一致,都是先上升后下降,最后再上升。本研究认为这种变化前期是植物自我的保护机制,后期的抗氧化酶含量上升可能是植物对环境产生了适应性。综合分析,认为在自然干旱胁迫下野菊有较好的忍耐能力、恢复能力和适应能力,具有较强的抗旱性,可作为良好的园林植物材料应用。 相似文献
6.
REASON FOR PERFORMING STUDY: Tachykinins have profound effects on equine intestinal motility, but the distribution of the neurokinin receptors (NKRs) through which they act is unknown. This study reports the distribution of one of these receptors, the neurokinin-1 receptor (NK1R), in smooth muscle throughout the equine intestinal tract. OBJECTIVES: To quantify the distribution of the NK1R, based upon mRNA expression, in smooth muscle of different regions of the equine intestinal tract. METHODS: Nine regions of the intestinal tract were sampled in 5 mature horses. Total RNA was isolated from smooth muscle and reverse transcribed; NK1R mRNA was then quantified using real-time PCR. RESULTS: NK1R mRNA was found at all levels of the sampled intestinal tract. The smooth muscle of the proximal small intestine and the ventral colon exhibited the highest level of NK1R mRNA expression in the equine intestinal tract. CONCLUSIONS: Tachykinins probably affect intestinal contractility and propulsion in the proximal small intestine and in the ventral colon. 相似文献
7.
柞蚕抗菌肽D基因在酵母中表达的研究 总被引:6,自引:2,他引:6
柞蚕抗菌肽具有广谱杀菌功能,人工合成抗菌肽D基因(122bp)与含α-因子及前导肽序列的穿梭质粒pCLWA2重组,克隆于酵母AB103。在缺亮氨酸的YE培养基中筛选Leu+阳性的转化子。转化子菌株培养扩增后提取重组质粒与抗菌肽基因片段探针作点杂交为阳性,电泳后插入含抗菌肽D基因128bp的区带。在转基因酵母的发酵液中分离上清液,浓缩,对抗菌肽敏感的指示菌E.coliK12D31有明显抑菌效应。证实人工合成柞蚕抗菌肽D基因在酵母中表达。 相似文献
8.
《The Journal of Applied Poultry Research》2009,18(2):143-150
The present study was conducted to investigate the effect of feeding Camelina sativa to layer birds on egg production, egg quality characteristics, egg lipids, and fatty acid and lipid oxidation products. Fifty-eight-week-old ISA Brown Leghorn laying hens (n = 48) were kept in individual cages and were fed a corn- and soybean meal-based diet with added Camelina meal at 0%, (control), 5%, (CAM5), 10% (CAM10), and 15% (CAM15). The experimental diets were fed for a period of 80 d. Hen-day egg production was lowest for CAM15 (P < 0.05). A significant reduction in yolk weight was observed for CAM10 and CAM15 eggs when compared with control eggs (P < 0.05). Yolk weight, as a percentage of egg weight, was lower for CAM10 and CAM15 eggs, whereas albumen weight, as a percentage of egg weight, was higher in CAM10 and CAM15 eggs than in control eggs (P < 0.05). The yolk:albumen ratio was higher in control eggs than in CAM10 and CAM15 eggs (P < 0.05). Egg total fat content was lowest for CAM15 eggs and was 31.5, 31.9, 30.8, and 29.5 for control, CAM5, CAM10, and CAM15 eggs, respectively (P < 0.05). Total n-3 fatty acids constituted 0.32% in control eggs compared with 2.54, 2.69, and 2.99% in CAM5, CAM10, and CAM15 eggs (P < 0.05). An 8-fold increase in docosahexaenoic acid was observed in CAM15 eggs when compared with control eggs (P < 0.05). The n-6:n-3 ratio was 14.8, 5.6, 4.6, and 4.3 for control, CAM5, CAM10, and CAM15 eggs, respectively (P < 0.05). Total saturated fats were lowest for CAM5 and CAM10 eggs. Eggs from the CAM15 regimen had higher TBA-reactive substance values (P < 0.05) than those from the CAM5, CAM10, or control regimen. Camelina meal could be incorporated into poultry rations as a source of energy, protein, and essential n-3 and n-6 fatty acids. However, inclusion of more than 10% Camelina meal in the hen diet may affect egg lipid quality aspects. Therefore, measures for minimizing lipid peroxidation should be used to enhance egg quality and lipid stability. 相似文献
9.
(目的)本文旨在联合使用质量平衡法与差示扫描量热法2种定值方法测定非班太尔对照品的含量。(方法)采用高效液相色谱法测定非班太尔的纯度,采用卡尔费休氏容量滴定法、炽灼残渣检查法、气相色谱法分别测定其水分、灰分和残留溶剂,由质量平衡法公式计算非班太尔对照品的含量;采用差示扫描量热法对非班太尔对照品含量加以佐证。(结果)质量平衡法和差示扫描量热法测定结果经科克伦判定互为等精度,取其算术平均值作为最终定值结果,即非班太尔对照品含量为99.66%。(结论)质量平衡法与差示扫描量热法对非班太尔对照品的定值结果基本一致,2种方法能够更好地保证非班太尔对照品赋值的准确性。 相似文献
10.
山西天然草地主要有毒植物 总被引:5,自引:1,他引:5
山西省天然草地中有毒植物有35科91属148种,其中以亚高山草甸类草地中出现较多,占总产草量的15%-18.1%。文章就山西天然草地上出现数量较多,易引起家畜中毒的植物,从生态分布、有毒成分及对家畜的危害等方面进行了研究,并提出了防除的建议。 相似文献