全文获取类型
收费全文 | 25887篇 |
免费 | 1009篇 |
国内免费 | 1934篇 |
专业分类
林业 | 3253篇 |
农学 | 3094篇 |
基础科学 | 1631篇 |
4026篇 | |
综合类 | 5514篇 |
农作物 | 1407篇 |
水产渔业 | 1231篇 |
畜牧兽医 | 6048篇 |
园艺 | 742篇 |
植物保护 | 1884篇 |
出版年
2023年 | 206篇 |
2022年 | 494篇 |
2021年 | 691篇 |
2020年 | 663篇 |
2019年 | 594篇 |
2018年 | 531篇 |
2017年 | 804篇 |
2016年 | 774篇 |
2015年 | 1009篇 |
2014年 | 948篇 |
2013年 | 1057篇 |
2012年 | 1457篇 |
2011年 | 1416篇 |
2010年 | 1174篇 |
2009年 | 1131篇 |
2008年 | 1081篇 |
2007年 | 1085篇 |
2006年 | 1090篇 |
2005年 | 1763篇 |
2004年 | 1097篇 |
2003年 | 848篇 |
2002年 | 414篇 |
2001年 | 498篇 |
2000年 | 458篇 |
1999年 | 716篇 |
1998年 | 514篇 |
1997年 | 461篇 |
1996年 | 455篇 |
1995年 | 388篇 |
1994年 | 338篇 |
1993年 | 309篇 |
1992年 | 408篇 |
1991年 | 410篇 |
1990年 | 360篇 |
1989年 | 311篇 |
1988年 | 296篇 |
1987年 | 190篇 |
1986年 | 188篇 |
1985年 | 146篇 |
1984年 | 110篇 |
1979年 | 137篇 |
1975年 | 137篇 |
1974年 | 129篇 |
1973年 | 116篇 |
1972年 | 138篇 |
1971年 | 118篇 |
1969年 | 102篇 |
1968年 | 113篇 |
1967年 | 125篇 |
1966年 | 102篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
为提高我省湿地保护管理工作者的业务水平,应广大湿地保护管理人员的要求,根据省厅2008年工作计划的安排,组织了这次湿地保护管理考察学习。通过考察学习,使参与湿地保护管理的工作人员对湿地有了充分的认识,学习新疆林业厅在各湿地保护区工作中的经验,将学到的经验在陕西各地进行推广,推动湿地保护管理工作迈上新的台阶。 相似文献
33.
34.
We report on an outbreak of enzootic abortion in a herd of goats with high losses caused by mixed infection with Coxiella burnetii and Chlamydia psittaci. Both agents could be detected by microscopic investigation of smears from afterbirths by Giménez staining and by a capture enzyme-linked immunofluorescence assay (Capture ELIFA). Additionally, Coxiella burnetii was isolated from the same tissues in BGM cell cultures. Serological investigations with CF, indirect ELIFA, and IF tests revealed high antibody titers against both agents in most animals. Coxiella antigen was still detected 91 days later in milk samples of two infected goats by Capture ELIFA. 相似文献
35.
以17β-雌二醇-6-人血清白蛋白对新西兰公兔进行主动免疫,用RIA检测抗体滴度和17β-雌二醇及睾酮浓度,并检测睾丸重量和间质细胞面积。结果,试验组各兔均不同程度地产生了17β-雌二醇抗体,其血浆17β-雌二醇浓度极显著地低于对照组〔(20.3±21.6)ng/L,(167.7±49.6)ng/L,P<0.001〕,睾酮浓度极显著地高于对照组〔(7.3±7.1)μg/L,(0.52±0.29)μg/L,P<0.01〕。每侧睾丸重量和间质细胞面积均极显著地大于对照组〔(3.94±0.93)g和(252.25±85.78)μm2,(2.98±0.72)g和(161.79±36.45)μm2,P<0.01和P<0.001〕。提示17β-雌二醇主动免疫可望成为提高雄性动物生育力的有效途径之一 相似文献
36.
The influence of an eradication programme for lice on the prevalence of light flecks and spots on cattle hides was studied in 33 dairy cattle herds during a period of two and a half years. Lice were eradicated from the main group of herds after 9 to 12 months and the quality of the hides before and after treatment was compared. Hides from slaughtered animals were collected during the study period, tanned and examined with special emphasis on the occurrence of the grain damage light flecks and spots. The prevalence of hides without light flecks and spots increased from 24.2% before treatment to 61.6% after treatment. The prevalence of hides free from the damage increased significantly in all examined anatomical regions. The improvement in hide quality was most marked in the shoulders and neck region which corresponded to the major predilection site of cattle lice. The prevalence of hides with light flecks and spots started to decrease in the first period (2-40 days) after eradication. The changes after treatment suggested that most healing process took place over a period of about 4 months. The eradication programme eliminated the seasonal variation in the prevalence of light flecks and spots which was present before treatment. 相似文献
37.
T Kokkonen A Tsehai Tesfa M Tuori S Yrj?nen L Syrj?l?-Qvist 《Archives of Animal Nutrition》2002,56(3):213-227
Twenty-one multiparous dairy cows were fed concentrates containing three levels (119, 154 and 191 g/kg DM) of crude protein (CP) during the first ten weeks of lactation. Part of the grain and molassed sugar beat pulp was substituted with 0% (RSM0), 15% (RSM15) or 30% (RSM30) repeseed meal. Wilted grass silage was fed ad libitum after calving. The average response between RSM0 and RSM15 was +1.66 kg milk/d per percentage unit change in concentrate CP content. No further response occurred between RSM15 and RSM30. The positive effect of RSM inclusion was seen throughout the experimental period and was associated with increased plasma non esterified fatty acids (NEFA) and decreased plasma insulin concentration one week after calving, and higher efficiency of metabolisable energy utilisation for milk production. Digestibility of the diet remained unaffected. Milk and plasma urea tended to increase with RSM30 indicating excessive supply of rumen degradable protein. Because of the limited potential of cows to compensate for a deficit in feed protein supply by mobilising tissue protein, a substantial milk yield response can be achieved with a moderate level of protein supplementation during early lactation. 相似文献
38.
银杏幼苗叶片转化酶活性及其动力学 总被引:4,自引:0,他引:4
采用波钦诺克XH法研究了田间和室内栽培的银杏幼苗叶片转化酶的活性及其动力学性质。结果表明:银杏幼苗叶片转化酶在pH值5.0、温度55℃时活性最强;该酶的米氏常数为3.7×10-2mol·L-1;室内盆栽的银杏幼苗叶片转化酶的活性显著高于田间栽培的同龄银杏幼苗叶片转化酶的活性。 相似文献
39.
研究不同有机物浸提液对铁皮石斛试管苗生长的影响。在相同的培养条件下,以8种含有不同有机物的培养基培养试管苗,60d后对试管苗的各种性状进行记录统计,并与对照(没加有机物提取液)进行比较分析。结果不同的有机物浸提液对试管苗的影响效果不一样。壮苗以加入白萝卜提取液、CH和CM为佳,生根以加入香蕉提取液为佳,要提高繁殖系数以不加有机物为佳。 相似文献
40.