全文获取类型
收费全文 | 82397篇 |
免费 | 18928篇 |
国内免费 | 28997篇 |
专业分类
林业 | 9152篇 |
农学 | 8781篇 |
基础科学 | 9149篇 |
35380篇 | |
综合类 | 34596篇 |
农作物 | 6946篇 |
水产渔业 | 6446篇 |
畜牧兽医 | 9744篇 |
园艺 | 3147篇 |
植物保护 | 6981篇 |
出版年
2024年 | 931篇 |
2023年 | 1186篇 |
2022年 | 1701篇 |
2021年 | 1748篇 |
2020年 | 3303篇 |
2019年 | 6673篇 |
2018年 | 6288篇 |
2017年 | 7230篇 |
2016年 | 7942篇 |
2015年 | 8175篇 |
2014年 | 7229篇 |
2013年 | 7702篇 |
2012年 | 7715篇 |
2011年 | 6835篇 |
2010年 | 5733篇 |
2009年 | 5214篇 |
2008年 | 4088篇 |
2007年 | 4215篇 |
2006年 | 3674篇 |
2005年 | 3325篇 |
2004年 | 2914篇 |
2003年 | 2604篇 |
2002年 | 2364篇 |
2001年 | 1987篇 |
2000年 | 1737篇 |
1999年 | 1679篇 |
1998年 | 1528篇 |
1997年 | 1471篇 |
1996年 | 1286篇 |
1995年 | 1334篇 |
1994年 | 1342篇 |
1993年 | 1036篇 |
1992年 | 1070篇 |
1991年 | 872篇 |
1990年 | 688篇 |
1989年 | 660篇 |
1988年 | 577篇 |
1987年 | 419篇 |
1986年 | 423篇 |
1985年 | 216篇 |
1984年 | 205篇 |
1983年 | 191篇 |
1982年 | 196篇 |
1981年 | 237篇 |
1980年 | 193篇 |
1979年 | 153篇 |
1978年 | 131篇 |
1975年 | 109篇 |
1965年 | 139篇 |
1964年 | 144篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
141.
142.
Chaiyan Kasorndorkbua Brad J. Thacker Patrick G. Halbur Denis K. Guenette Ryan M. Buitenwerf Ryan L. Royer Xiang-Jin Meng 《Canadian journal of veterinary research》2003,67(4):303-306
To determine the effect of swine hepatitis E virus (HEV) infection on pregnant gilts, their fetuses, and offspring, 12 gilts were intravenously inoculated with swine HEV. Six gilts, who were not inoculated, served as controls. All inoculated gilts became actively infected and shed HEV in feces, but vertical transmission was not detected in the fetuses. There was no evidence of clinical disease in the gilts or their offspring. Mild multifocal lymphohistiocytic hepatitis was observed in 4 of 12 inoculated gilts. There was no significant effect of swine HEV on fetal size, fetal viability, or offspring birth weight or weight gain. The offspring acquired anti-HEV colostral antibodies but remained seronegative after the antibodies waned by 71 days of age. Swine HEV infection induced subclinical hepatitis in pregnant gilts, but had no effect on the gilts' reproductive performance, or the fetuses or offspring. Fulminant hepatitis associated with HEV infection was not reproduced in gilts. 相似文献
143.
Expression of β2-integrin on monocytes and blood polymorphonuclear leukocytes in the periparturient period in dairy cows
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)
Araceli Diez-Fraile Luc Duchateau Evelyne Meyer Christian Burvenich 《Canadian journal of veterinary research》2003,67(3):235-238
The hypothesis that an altered expression of CD11/CD18 on bovine circulating monocytes, polymorphonuclear leukocytes (PMN), or both, contributes to an increased mastitis susceptibility in periparturient cows was tested. Expression of CD18 and CD11a, -b, -c on bovine monocytes and PMN were assessed in 8 Friesian-Holstein cows by flow cytometry from 2 wk before calving to 5 wk after calving. Minor changes in adhesion molecule expression levels were detected throughout the experimental period. Compared with PMN, monocytes exhibited an expression level that was similar for CD18, higher for CD11a and CD11c, but lower for CD11b. Differences in density may reflect the relative importance of these adhesion molecules on both leukocyte types. In this study, the decreased number of milk resident macrophages and PMN observed during the periparturient period could not be attributed to changes of CD11/CD18 levels on circulating leukocytes. 相似文献
144.
145.
146.
研究结果表明,由性状果实最大周长,果实体积,门茄显蕾期,单株产量等性状构成的选择指数较好;进一步进行遗传相关分析结果认为,应用选择指数时应注意果实体积这个性状,单株产量是一个重要的辅助性状,门茄显蕾期是一个限制性因子。应用选择指数对品种评价结果认为,早熟性较好的品种有:天津早茄、西安绿茄、二民、七叶茄、白线茄和汉中荷包。 相似文献
147.
1987~1992年连续6年研究结果表明,白跗平腹小蜂Anastatusalbitarsis对马尾松毛虫Dendrolimuspunctatus、柳杉毛虫Dendrolimuslatipennis、水青蛾Actiasseteneningpoana等13种主要森林害虫卵有较明显的抑制作用。在林间,该蜂对马尾松毛虫第1、2代卵的自然抑制力分别力16.55%和22.29%,对柳杉毛虫越冬代卵的自然抑制力为23.45%;对水青蛾第1、2代卵的抑制力分别力5.49%和2.63%;在林间,人为释放白跗平腹小蜂对第1代马尾松毛虫卵的校正抑制力为33.5%,在室内12.3~28℃范围内,每头雌峰对马尾松毛虫、水青蛾和柞蚕剖腹卵的日破坏数(寄生数)分别力15、18和26粒,一生破坏数分别为56、91和208粒。即使虫卵即将孵化,该峰同样亦能寄生,并羽化出正常的子代白跗平腹小蜂。 相似文献
148.
S Rosendal P L Frandsen J P Nielsen R Gallily 《Canadian journal of veterinary research》1995,59(2):154-156
Pasteurella multocida toxin (PMT) is the major virulence factor in Progressive Atrophic Rhinitis of swine. Other workers' previous findings that PMT was mitogenic for 3T3 fibroblasts, were confirmed in the present study. In addition, PMT stimulated 3T3 cells to release IL-6, but IL-1 alpha or TNF alpha were not detected in fibroblast supernatants sampled 24, 48, or 72 h after stimulation. In view of the role of IL-6 in osteoclastic bone resorption, these findings provide a new working hypothesis for investigations into the molecular pathogenesis of this important disease. 相似文献
149.
Comparison of dot blot hybridization, polymerase chain reaction, and virus isolation for detection of bovine herpesvirus-1 (BHV-1) in artificially infected bovine semen. 总被引:2,自引:0,他引:2
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)
Bovine semen samples spiked with bovine herpesvirus 1 (BHV-1) were used to compare dot blot hybridization, polymerase chain reaction (PCR), and virus isolation for detection of BHV-1 in bovine semen. The PCR amplification used primers targeting the BHV-1 thymidine kinase gene and a nucleic acid releasing cocktail (GeneReleaser); the PCR product was used as the DNA probe in dot blot hybridization; virus isolation was done in primary bovine fetal testis (BFT) cell cultures. Semen diluted 1:20 in tissue culture medium had the least cytotoxicity and inhibition of viral cytopathic effects in BFT cells, allowing detection of 1 TCID50/100 microL of BHV-1 suspension by virus isolation. The presence of foreign DNA such as bovine sperm DNA or salmon sperm DNA increased the sensitivity of dot blot hybridization in detecting BHV-1, allowing detection of 20,000 TCID50/100 microL of neat semen. The inhibition of PCR amplification of BHV-1 DNA in bovine semen was eliminated by diluting the samples 1:20 in tissue culture medium. The best PCR amplification was obtained when semen was diluted 1:20 and when a reaction buffer of pH 9.0, with 1.0 mM MgCl2 was used. Under these conditions, the PCR followed by ethidium bromide staining of agarose gels could detect 1 TCID20/100 microL of sample, whereas PCR followed by Southern blot hybridization could detect 0.01 TCID50/100 microL of sample.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
150.
用全薯块吸头刺伤接种法测定时,较理想的测定条件为:每接种点接种0.1ml浓度为10~2~10~5CFU/ml菌悬液,随后在21±5℃~31±5℃(依所用菌株而定)下保持2~3天,以接种点腐烂斑的最大直径作记载标准。用新鲜薯片法测定时,除接种浓度为10~2~10~3CFU/ml,保持时间为1~2天及以侵染限值作评价标准外,其余条件和全薯块吸头刺伤接种法相同。当用皮孔浸渍法接种时,薯块在10_6CFU/ml菌悬液中浸5分钟,然后使薯块表面保持连续水膜,3~5天后测量薯块表面腐烂面积。上述3种方法都必须有20个以上重复,并使用大小一致、无伤无病的成熟薯块。 相似文献