全文获取类型
收费全文 | 2580篇 |
免费 | 158篇 |
国内免费 | 193篇 |
专业分类
林业 | 154篇 |
农学 | 195篇 |
基础科学 | 253篇 |
230篇 | |
综合类 | 1044篇 |
农作物 | 105篇 |
水产渔业 | 197篇 |
畜牧兽医 | 546篇 |
园艺 | 109篇 |
植物保护 | 98篇 |
出版年
2024年 | 27篇 |
2023年 | 64篇 |
2022年 | 88篇 |
2021年 | 109篇 |
2020年 | 116篇 |
2019年 | 112篇 |
2018年 | 76篇 |
2017年 | 120篇 |
2016年 | 136篇 |
2015年 | 110篇 |
2014年 | 158篇 |
2013年 | 141篇 |
2012年 | 199篇 |
2011年 | 229篇 |
2010年 | 119篇 |
2009年 | 139篇 |
2008年 | 113篇 |
2007年 | 152篇 |
2006年 | 116篇 |
2005年 | 96篇 |
2004年 | 72篇 |
2003年 | 75篇 |
2002年 | 51篇 |
2001年 | 55篇 |
2000年 | 49篇 |
1999年 | 37篇 |
1998年 | 39篇 |
1997年 | 21篇 |
1996年 | 29篇 |
1995年 | 15篇 |
1994年 | 16篇 |
1993年 | 11篇 |
1992年 | 7篇 |
1991年 | 12篇 |
1990年 | 4篇 |
1989年 | 12篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
排序方式: 共有2931条查询结果,搜索用时 15 毫秒
61.
应用RT-PCR方法对南京、上海和合肥猪源隐孢子虫卵囊SSU rRNA部分序列进行扩增,产物测序后提交GenBank,收录号为DQ855266、DQ855267;用BLAST和DNAStar软件与GenBank参考序列进行比较,分析其同源性,绘制系统发育进化树,结合卵囊形态学观察和对小鼠、大鼠、兔、山羊和鸡的传染性试验确定隐孢子虫种类或基因型。结果表明,3地区猪源隐孢子虫分离株与微小隐孢子虫(C.parvum)同源性达94%~100%,与C.parvummouse型有99.8%~100%的同源性,并处于进化树的同一分支。因此,3地区猪源隐孢子虫是C.parvummouse型,提示猪和鼠之间存在交叉传播的可能。 相似文献
62.
Zirui Zhou Jie Zhang Xianlian Zhang Shilan Mo Xian Tan Lixia Wang Jianzhong Li Yali Li Xueqin Ding Xianyong Liu Xingqun Ma Huansheng Yang Yulong Yin 《Journal of animal physiology and animal nutrition》2019,103(5):1530-1537
Weaning process widely affects the small intestinal structure and function in piglets, while the responses of large intestine to weaning stress are still obscure. The purpose of this study was to determine the developmental changes (i.e., short chain fatty acids (SCFAs) concentrations, growth parameters, crypt‐related indices and antioxidant capacity) in colon of piglet during weaning. Forty piglets were weaned at day 21 and euthanized to collect colonic tissues and digesta samples on day 0, 1, 3, 7 and 14 post‐weaning (n = 8). Piglet growth performance was improved (p < .001) on day 7 and 14 post‐weaning. The concentrations of acetate, propionate, butyrate, valerate, isobutyrate, isovalerate and total SCFAs were higher (p < .001) during the late post‐weaning period. The mRNA abundances of SCFAs transporters were greater (p < .001) on day 7 and 14. The absolute and relative weights, absolute length and perimeter of colon were greater (p < .001) on day 7 and 14. Similarly, post‐weaning increases (p < .001) in colonic crypt depth and Ki67 positive cells numbers per crypt were observed during the same period. Colonic crypt fission indices decreased (p < .01), while total crypt numbers increased (p < .001) on day 14 after weaning. Moreover, total SCFAs concentration was significantly associated with colonic growth parameters and Ki67 cells/crypt (p < .001). In addition, catalase content was decreased on day 3, 7, and 14, whereas, the concentrations of total superoxide dismutase (T‐SOD) and manganese‐containing superoxide dismutase (MnSOD) were higher (p < .05) on day 1 and 3 post‐weaning. These results showed that weaning process has a significant effect on colonic growth and development, which might be associated with the change of SCFAs concentrations in colon. 相似文献
63.
64.
65.
66.
67.
Trichoderma Biocontrol of Colletotrichum acutatum and Botrytis cinerea and Survival in Strawberry 总被引:1,自引:2,他引:1
Stanley Freeman Dror Minz Inna Kolesnik Olga Barbul Aida Zveibil Marcel Maymon Yehuda Nitzani Benny Kirshner Dalia Rav-David Alon Bilu Arnon Dag Sharoni Shafir Yigal Elad 《European journal of plant pathology / European Foundation for Plant Pathology》2004,110(4):361-370
Trichoderma isolates are known for their ability to control plant pathogens. It has been shown that various isolates of Trichoderma, including T. harzianum isolate T-39 from the commercial biological control product TRICHODEX, were effective in controlling anthracnose (Colletotrichum acutatum) and grey mould (Botrytis cinerea) in strawberry, under controlled and greenhouse conditions. Three selected Trichoderma strains, namely T-39, T-161 and T-166, were evaluated in large-scale experiments using different timing application and dosage rates for reduction of strawberry anthracnose and grey mould. All possible combinations of single, double or triple mixtures of Trichoderma strains, applied at 0.4% and 0.8% concentrations, and at 7 or 10 day intervals, resulted in reduction of anthracnose severity; the higher concentration (0.8%) was superior in control whether used with single isolates or as a result of combined application of two isolates, each at 0.4%. Only a few treatments resulted in significant control of grey mould. Isolates T-39 applied at 0.4% at 2 day intervals, T-166 at 0.4%, or T-161 combined with T-39 at 0.4% were as effective as the chemical fungicide fenhexamide. The survival dynamics of populations of the Trichoderma isolates (T-39, T-105, T-161 and T-166) applied separately was determined by dilution plating and isolates in the mixtures calculated according to the polymerase chain reaction (PCR) using repeat motif primers. The biocontrol isolates were identified to the respective species T. harzianum (T-39), T. hamatum (T-105), T. atroviride (T-161) and T. longibrachiatum (T-166), according to internal transcribed spacer sequence analysis. 相似文献
68.
Mariner转座子与小菜蛾抗性关系的研究 总被引:1,自引:1,他引:1
以抗溴氰菊酯、杀虫双、杀螟丹小菜蛾种群及其敏感品系为研究对象,借助聚合酶链式反应(PCR)、载体筛选、琼脂糖凝胶电泳等实验技术,检测了小菜蛾4个品系的Mariner转座子的存在及其与抗性的关系。结果表明,在抗溴氰菊酯、杀虫双、杀螟丹以及敏感品系的小菜蛾中都存在两种大约500 bp的Mariner转座子片断,初次证明在小菜蛾4个品系中均含有两种Mariner转座子,并发现一种新的转座子基因片断,但是没有发现Mariner转座子与抗性之间存在直接的联系。研究结果将为利用Mariner转座子标签法在小菜蛾中分离定位基因、转化外源基因、转基因昆虫防治害虫等研究提供理论基础。 相似文献
69.
Rosypal AC Troy GC Duncan RB Zajac AM Lindsay DS 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2005,19(6):802-809
Eight female beagles were infected with 1 x 10(7) (low dose, LD) or 2 x 10(8) (high dose, HD) promastigotes of a North American isolate of Leishmania infantum infantum (LIVT-1 strain) isolated from naturally infected Virginia Foxhounds. Two female beagles served as negative controls and 2 male beagles chronically infected (> 3 years) with Leishmania infantum chagasi were positive controls. Bone marrow (BM) and lymph node (LN) aspirates were collected every 6-8 weeks for cytologic evaluation, parasite culture, and polymerase chain reaction (PCR). Serum samples were collected monthly for determination of serologic responses by indirect fluorescent antibody test (IFAT) and diagnostic rK39 antigen. Cultures of BM and LN aspirates and cytology evaluation were consistently positive in positive control dogs during the course of study. Negative control dogs were negative on BM and LN cultures and on cytologic evaluation of aspirates. Amastigotes were present on cytological examination of BM aspirates in 2 experimentally infected dogs. Cultures of LN aspirates were positive on 22 samples, whereas BM cultures were positive on 12 samples for all dogs. IFA titers ranged from 0 to 1 :400 in experimentally infected dogs during the course of the study. Recombinant K39 immunoassay tests were consistently positive in positive control dogs and in the HD dogs by approximately 8 weeks after infection. BM PCR products were identified more consistently in the HD dogs compared with the LD dogs. Kappa statistics indicated PCR correlated better with cultures and cytology than did IFAT or the rK39 immunoassay results in the experimentally infected dogs. 相似文献
70.