全文获取类型
收费全文 | 621篇 |
免费 | 25篇 |
国内免费 | 43篇 |
专业分类
林业 | 57篇 |
农学 | 39篇 |
基础科学 | 17篇 |
85篇 | |
综合类 | 192篇 |
农作物 | 25篇 |
水产渔业 | 19篇 |
畜牧兽医 | 163篇 |
园艺 | 28篇 |
植物保护 | 64篇 |
出版年
2024年 | 3篇 |
2023年 | 13篇 |
2022年 | 27篇 |
2021年 | 24篇 |
2020年 | 30篇 |
2019年 | 32篇 |
2018年 | 18篇 |
2017年 | 30篇 |
2016年 | 9篇 |
2015年 | 22篇 |
2014年 | 28篇 |
2013年 | 22篇 |
2012年 | 47篇 |
2011年 | 47篇 |
2010年 | 49篇 |
2009年 | 41篇 |
2008年 | 44篇 |
2007年 | 39篇 |
2006年 | 42篇 |
2005年 | 26篇 |
2004年 | 14篇 |
2003年 | 11篇 |
2002年 | 17篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 9篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1975年 | 2篇 |
1972年 | 1篇 |
1970年 | 3篇 |
1969年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有689条查询结果,搜索用时 15 毫秒
11.
12.
应用吸管法进行风沙土机械组成分析的实验研究 总被引:2,自引:0,他引:2
土壤机械组成分析就是指土壤粒径分析,即测定组成土壤的不同直径颗粒的含量。通过机械组成分析可以定量地了解土壤质地的粗细、理化性状、肥力状况及土壤的发育情况。经过从毛乌素沙地、腾格里沙漠和浑善达克沙地等几个区域采样实验,探讨了用吸管法测定风沙土机械组成的实验控制。结果显示:在司托克斯原理指导下的吸管法测定风沙土机械组成的实验中,传统吸管法的10cm深抽样条件下粉粒与黏粒段不能正常测定。8cm深抽样条件下,振荡分散1h有20%的样在粉粒与黏粒段的测定结果有悖实际,煮沸分散1h与煮沸分散10min两种测定结果在砂、粉、黏三段内的变异系数较大。经对比分析,在用吸管法测定风沙土机械组成实验中,以煮沸分散1h,抽样深8cm的实验效果良好。 相似文献
13.
14.
不同种植方式对冬小麦花后干物质积累与分配特征及产量的影响 总被引:7,自引:0,他引:7
为探索不同种植方式对冬小麦干物质积累、转运与分配特征及产量的影响,选用大穗型小麦品种农大1108为试验材料,研究在大田生产中主要的4种种植方式(穴播、撒播、窄幅条播和宽幅条播)对冬小麦花后各器官干物质积累、分配及产量的影响。结果表明,4种种植方式下花后各器官的干物质积累量变化趋势基本一致,且均表现为窄幅条播显著高于其他3组处理;窄幅条播主要通过提高花后干物质同化量及其对籽粒的贡献率而获得高产;与宽幅条播相比,窄幅条播花后营养器官干物质积累量及干物质在籽粒中的积累量分别增加45.59%和19.44%;与穴播和撒播相比,窄幅条播产量分别提高17.25%和11.39%;花后干物质对籽粒的贡献率表现为穴播最高,达到80.26%。不同种植方式对冬小麦籽粒的灌浆速率影响不大,表现为各处理间千粒重差异不显著。 相似文献
15.
16.
ZHAO Ya-jun XU Chang-qing SHI Sa SUN Hong-li WANG Ning LI Bao-xin WANG Ling YANG Bao-feng Rui Wang 《园艺学报》2005,21(10):1938-1941
AIM: To study the effect of extrogenous low concentration polyamine on cardiomyocyte calcium overload caused by anoxia and reoxygenation. METHODS: Enzymatically isolated rat ventricular myocytes were perfused with normal Tyrode solution for 8 min, then change to anoxia solution for 32 min, at last back to normal Tyrode solution perfusion for 8 min to establish the cardiomyocyte model of anoxia and reoxygenation. Spermine was added extracellularly to the bath before anoxia and spermine, spermidine or putrescine was added extracellularly after reoxygenation. Intracellular calcium fluorescence intensity (FI) was measured continuously by laser scan confocal microscope (LSCM). RESULTS: In the unstimulated state, exogenous spermine (1 mol/L) did not change resting [Ca2+]i in the rat cardiomyocytes. Adding spermine before anoxia antagonized the [Ca2+]i elevating caused by anoxia/reoxygenation. Adding spermine after reoxygenation also lowed the enhanced [Ca2+]i caused by reoxygenation. Considering the potency of two conditions, the former was more efficacious than the later. Spermidine and putrescine also lowed the enhanced [Ca2+]i caused by reoxygenation, but they were less efficacious than spermine. CONCLUSIONS: The results indicate that spermine given before anoxia or after reoxygenation, antagonized or lowed the cardiomyocytes calcium overload caused by anoxia/reoxygenation, but the later was weaker than the former. The order of potency of the polyamine lighten cardiomyocytes calcium overload caused by anoxia/reoxygenation was spermine>spermindine>putrescine. 相似文献
17.
The aim of this research was to observe the effects of cyclophosphamide and its uroprotective agents, mesna and hyperbaric oxygen (HBO), on the motility of urinary bladder muscle in guinea pigs. In the experimental groups, mesna and cyclophosphamide were intraperitoneally injected at a dose of 21.5 mg/kg and 68.1 mg/kg, respectively. For the combination of mesna and cyclophosphamide, one dose of mesna was injected 20 min before cyclophosphamide administration and three additional injections of mesna were repeated every three hours. A total of 8 HBO exposures were performed at 2.8 ATA for 90 min twice daily for another experimental group. In the HBO and cyclophosphamide combined group 5 HBO exposures were given prophylactically before cyclophosphamide. The combination of mesna, HBO and cyclophosphamide was administered by the same procedure. The contractions obtained in response to acetylcholine (ACh, 10(-4) M) in the control group were reduced using cyclophosphamide and HBO individually, but not by mesna. However, the contractions belonging to the various combinations of these three agents were not different from those seen in the control group. On the other hand, the combinations of cyclophosphamide, mesna and HBO showed higher responses to ACh than the groups in which cyclophosphamide and HBO were used individually, while the responses elicited by the cyclophosphamide and HBO combination were greater than those seen in the group treated with HBO only. 相似文献
18.
This study was designed to investigate the presence of leptospiral antigens in kidney and liver of naturally infected cattle using an immunoperoxidase (IP) staining and Levaditi's staining methods. A total of 39 cattle suspected from leptospirosis were examined histologically and immunohistochemically for the presence of leptospiral antigens. The leptospiral antigens were detected in 16 out of 39 cases (seven kidneys, three livers, and six kidneys and livers) when IP staining method was used, whereas leptospiral antigens were detected in 6 out of 39 cases (four kidneys and two livers) when Levaditi's staining method was used. This study ascertained that IP staining was more sensitive method than Levaditi's staining method for demonstrating the presence of leptospirosis in cattle. 相似文献
19.
Passive protection of dogs against clinical disease due to Canine parvovirus-2 by specific antibody from chicken egg yolk 总被引:4,自引:0,他引:4
下载免费PDF全文
![点击此处可从《Canadian journal of veterinary research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Sa Van Nguyen Kouji Umeda Hideaki Yokoyama Yukinobu Tohya Yoshikatsu Kodama 《Canadian journal of veterinary research》2006,70(1):62-64
The protective effect of immunoglobulins derived from chicken egg yolk (IgY) against infection by Canine parvovirus 2 (CPV-2) was evaluated in 10 beagle dogs orally challenged with a strain of the virus. The 2-mo-old dogs were divided into 3 groups and treated with powders containing CPV-2 IgY or normal egg yolk for 7 d after the challenge. The 4 dogs receiving normal egg yolk (control group) demonstrated mild symptoms typical of CPV-2 infection, such as vomiting, diarrhea, and weight loss. No symptoms were observed by 16 d after challenge in the 3 dogs receiving 2 g of IgY powder. Of the 3 dogs receiving 0.5 g of IgY powder, 2 had clinical CPV-2 disease; however, the manifestations were less severe than in the control group. Furthermore, the IgY-treated groups had significantly greater weight gain and shorter duration of virus shedding than the control group. These results indicate that IgY is useful in protecting dogs from CPV-2-induced clinical disease. 相似文献
20.