全文获取类型
收费全文 | 85346篇 |
免费 | 6918篇 |
国内免费 | 7420篇 |
专业分类
林业 | 10064篇 |
农学 | 11690篇 |
基础科学 | 7214篇 |
13600篇 | |
综合类 | 28536篇 |
农作物 | 4708篇 |
水产渔业 | 3008篇 |
畜牧兽医 | 11806篇 |
园艺 | 3534篇 |
植物保护 | 5524篇 |
出版年
2025年 | 15篇 |
2024年 | 1112篇 |
2023年 | 1357篇 |
2022年 | 2476篇 |
2021年 | 3433篇 |
2020年 | 3170篇 |
2019年 | 3057篇 |
2018年 | 2217篇 |
2017年 | 3099篇 |
2016年 | 2885篇 |
2015年 | 3929篇 |
2014年 | 3779篇 |
2013年 | 4494篇 |
2012年 | 5553篇 |
2011年 | 5941篇 |
2010年 | 5892篇 |
2009年 | 5396篇 |
2008年 | 4993篇 |
2007年 | 5128篇 |
2006年 | 4771篇 |
2005年 | 4207篇 |
2004年 | 2042篇 |
2003年 | 1928篇 |
2002年 | 1666篇 |
2001年 | 1679篇 |
2000年 | 1732篇 |
1999年 | 1945篇 |
1998年 | 1694篇 |
1997年 | 1527篇 |
1996年 | 1387篇 |
1995年 | 1254篇 |
1994年 | 1064篇 |
1993年 | 1090篇 |
1992年 | 851篇 |
1991年 | 719篇 |
1990年 | 605篇 |
1989年 | 486篇 |
1988年 | 366篇 |
1987年 | 229篇 |
1986年 | 127篇 |
1985年 | 66篇 |
1984年 | 45篇 |
1983年 | 40篇 |
1982年 | 49篇 |
1981年 | 48篇 |
1980年 | 32篇 |
1979年 | 14篇 |
1965年 | 15篇 |
1964年 | 11篇 |
1963年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
32.
鹿花盘水溶性成分的药理活性与临床应用 总被引:13,自引:1,他引:13
采用分子筛方法制备的鹿花盘水溶性成分及多肽具有明显地抑制戊酸雌二醇所致的乳腺增生,其作用强度较丙酸睾丸素125 m g/kg 强。此外,还有较显著地促进巨噬细胞的吞噬功能和增加 T 淋巴细胞的增殖能力,抑制 M A- 737 乳腺癌的生长,改善乳腺癌小鼠 T 淋巴细胞的衰竭。通过急性、亚急性、过敏性等安全性试验检查证明,鹿花盘水溶性成分无任何毒副作用,进一步通过146 例乳腺增生患者的临床疗效观察,其有效率达8355 % ,是一种很有前途的妇女保健产品。 相似文献
33.
A. A. Roess A. M. McCollum K. Gruszynski H. Zhao W. Davidson N. Lafon T. Engelmeyer B. Moyer C. Godfrey H. Kilpatrick A. Labonte J. Murphy D. S. Carroll Y. Li I. K. Damon 《Zoonoses and public health》2013,60(8):543-548
In 2008, two deer hunters in Virginia and Connecticut were infected with a unique strain of pseudocowpox virus, a parapoxvirus. To estimate the prevalence of this virus, and in an attempt to define the reservoir, Parapoxvirus surveillance was undertaken between November 2009 and January 2010. 125 samples from four ruminant species (cows, goat, sheep and white‐tailed deer) were collected in Virginia, and nine samples from white‐tailed deer were collected in Connecticut. We found no evidence that the parapoxvirus species that infected the deer hunters is circulating among domesticated ruminants or white‐tailed deer. However, parapoxvirus DNA of a different parapoxvirus species, bovine papular stomatitis virus (BPSV), was detected in 31 samples obtained from asymptomatic cattle in Virginia. Parapoxvirus DNA–positive cattle originated from the same counties indicating probable transmission among animals. Molecular analysis identified BPSV as the parapoxvirus affecting animals. Asymptomatic parapoxvirus infections in livestock, particularly young animals, may be common, and further investigation will inform our knowledge of virus transmission. 相似文献
34.
Jianpeng Gao Mingxing Tian Yanqing Bao Peng Li Jiameng Liu Chan Ding Shaohui Wang Tao Li Shengqing Yu 《Veterinary research》2016,47(1)
Brucellosis, caused by a facultative intracellular pathogen Brucella, is one of the most prevalent zoonosis worldwide. Host infection relies on several uncanonical virulence factors. A recent research hotpot is the links between carbon metabolism and bacterial virulence. In this study, we found that a carbon metabolism-related pyruvate kinase (Pyk) encoded by pyk gene (locus tag BAB_RS24320) was associated with Brucella virulence. Determination of bacterial growth curves and resistance to environmental stress factors showed that Pyk plays an important role in B. abortus growth, especially under the conditions of nutrition deprivation, and resistance to oxidative stress. Additionally, cell infection assay showed that Pyk is necessary for B. abortus survival and evading fusion with lysosomes within RAW264.7 cells. Moreover, animal experiments exhibited that the Pyk deletion significantly reduced B. abortus virulence in a mouse infection model. Our results elucidated the role of the Pyk in B. abortus virulence and provided information for further investigation of Brucella virulence associated carbon metabolism. 相似文献
35.
Xin-Yan Han Qi-Chun Huang Wei-Fen Li Jun-Fang Jiang Zi-Rong Xu 《Livestock Science》2008,119(1-3):216-220
The objective of this study was to investigate toxic effects of aflatoxin B1(AFB1) on growth performance, organs, hepatic enzyme activities, apparent digestibility of nutrients and digestive enzyme activities in ducks. Ninety 1-day-old Cherry Valley commercial ducks were designed to three treatment groups with three replicates of ten birds each. Group I (control) was fed conventional feed free of AFB1, group II or III was fed the diets containing 20 μg/kg or 40 μg/kg AFB1-contaminated rice respectively. The feeding trial lasted 6 weeks. The results were that decreased body weight gain and feed intake, increased feed to gain ratio and selected organ weights (liver, kidney and pancreas) were observed in AFB1-treated groups. The activities of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were significantly increased in AFB1-contamined groups. The apparent digestibility of crude protein (CP) was significantly lower while activities of digestive enzyme from duodenum contents including protease, chymotrypsin, trypsin and amylase were increased in AFB1-treated group. These results indicated that AFB1 of feed could decrease growth performance and apparent digestibility of nutrients, change digestive enzyme activities of duodenum contents in duck. 相似文献
36.
37.
天祝县牧区开发示范工程项目草地围栏建设及其综合效益 总被引:3,自引:0,他引:3
天祝县牧区开地示范工程项目1995年由农业部和国家计委审批立项,1996年全面启动建设,该项目以良种繁育,疫病防治,草地建设,技术服务四大体系为主体建设内容,并于1998年8月通过验收,围栏是草地建设体系的主要建设内容,在突出生产性,公益性,基础性建设原则的基础上,自1996年以来累计建成4000hm^2建成后,经综合改良,使草地植被得以迅速恢复,平均增产鲜草1653kg/hm^2,年创经济效益3 相似文献
38.
39.
40.
由于世界范围内大豆供应充足,而国内养殖业陷入低谷,导致下游豆粕需求始终未见明显提升,2006年以来的国内豆粕市场持续振荡走低,市场纷纷看空。进入8月份后,豆粕现货价格表现出了明显的抗跌特征,整体振荡,涨跌幅度均不大。尽管日前美国农业部8月份的供需报告中将全球大豆库存由 相似文献