全文获取类型
收费全文 | 21380篇 |
免费 | 1072篇 |
国内免费 | 1933篇 |
专业分类
林业 | 2337篇 |
农学 | 2349篇 |
基础科学 | 1220篇 |
2861篇 | |
综合类 | 7567篇 |
农作物 | 1573篇 |
水产渔业 | 975篇 |
畜牧兽医 | 3217篇 |
园艺 | 995篇 |
植物保护 | 1291篇 |
出版年
2024年 | 104篇 |
2023年 | 306篇 |
2022年 | 679篇 |
2021年 | 808篇 |
2020年 | 784篇 |
2019年 | 790篇 |
2018年 | 554篇 |
2017年 | 841篇 |
2016年 | 703篇 |
2015年 | 924篇 |
2014年 | 930篇 |
2013年 | 1141篇 |
2012年 | 1542篇 |
2011年 | 1589篇 |
2010年 | 1466篇 |
2009年 | 1351篇 |
2008年 | 1380篇 |
2007年 | 1234篇 |
2006年 | 1158篇 |
2005年 | 945篇 |
2004年 | 484篇 |
2003年 | 409篇 |
2002年 | 397篇 |
2001年 | 356篇 |
2000年 | 386篇 |
1999年 | 433篇 |
1998年 | 335篇 |
1997年 | 295篇 |
1996年 | 281篇 |
1995年 | 262篇 |
1994年 | 242篇 |
1993年 | 233篇 |
1992年 | 196篇 |
1991年 | 156篇 |
1990年 | 147篇 |
1989年 | 133篇 |
1988年 | 99篇 |
1987年 | 79篇 |
1986年 | 46篇 |
1985年 | 30篇 |
1984年 | 30篇 |
1983年 | 21篇 |
1982年 | 19篇 |
1981年 | 14篇 |
1980年 | 13篇 |
1979年 | 10篇 |
1974年 | 7篇 |
1965年 | 8篇 |
1964年 | 8篇 |
1956年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
192.
文章根据培养基类型、细胞分裂素浓度及生长素浓度的不同采用L9(3)4正交设计对笃丝越橘组织培养的增殖生长进行试验。 相似文献
193.
194.
牛皮蝇蛆是危害我国畜牧业发展最为严重的寄生虫病之一。本试验将已感染牛皮蝇蛆的171头肉牛为对象,随机分成5组。将"伊维菌素"注射液分别以高、中、低三种剂量对不同组别的肉牛进行颈部皮下注射治疗和观察,同时注射等体积生理盐水作为阴性对照组,饲喂"虫克星"粉剂作为阳性对照组进行对比试验。结果显示,0.2 mg/kg体重(中剂量组)为"伊维菌素"皮下注射的最佳剂量,对皮蝇蛆的治愈率达97.82%(45/46),而以0.2 mg/kg体重口服"虫克星"粉剂的对照组治愈率达60.71%(17/28),且统计分析差异显著(P0.05)。试验表明,中等剂量的"伊维菌素"注射液对牛皮蝇蛆的防治安全可靠且效果显著,为临床治疗肉牛皮蝇蛆提供理论参考。 相似文献
195.
196.
The test was aimed at determining the effects of adding MOS to diets with different concentrate to forage ratios on ruminal fermentation of sheep in vitro.The 4×6 two-factor experimental design was chosen.There were 4 diets with different concentrate to forage ratios(20:80, 30:70, 40:60 and 50:50) and added to 6 dosages MOS(0, 0.4%, 0.8%, 1.2%, 1.6% and 2.0%), respectively.The method of gas production in vitro was used to measure the total gas and CH4 production, IVDMD, IVCPD and IVOMD after cultured for 3, 6, 9, 12 and 24 h.The results showed that the gas(except 12 and 24 h) and CH4 production(except 9 h) were not impacted by the two factors(P>0.05).The IVDMD, IVCPD and IVOMD were significantly affected by concentrate to forage ratios(P<0.05), while the IVCPD at 24 h was significantly affected by MOS(P<0.05).Meanwhile, all the indexes were not influenced by the interaction of two factors(P>0.05).The IVDMD and IVOMD increased with the rising of concentrate approximately, while the IVCPD decreased with the rising of MOS roughly.The biggest associative effect was gained in 30:70 concentrate to forage diet when adding 1.2% MOS. 相似文献
197.
选取12个指标,通过主成分分析和聚类分析法综合评估了浙江省11个地级市的经济发展水平,把11个市分为3类,在此基础上提出建议,为浙江省的区域经济发展提供借鉴。 相似文献
198.
目前关于猪疾病的相关研究国内外已不少,其中猪内脏病变的研究也很深入,但是关于屠宰生猪肺脏眼观病变的研究还相对较少。鉴于屠宰生猪肺脏检疫在生猪屠宰检疫工作中的重要性,通过对福州地区某生猪屠宰场大量屠宰生猪肺脏眼观病变的观察,然后进行分类统计,从而了解该地区屠宰生猪肺脏大致病变类型与数量,为该地区疫病的分析起辅助作用,也为屠宰场的脏器检疫工作提供技术支持。 相似文献
199.
Xinliang Dong Bhupinder Pal Singh Guitong Li Qimei Lin Xiaorong Zhao 《Soil Use and Management》2019,35(3):466-477
Biochar application can improve soil properties, such as increasing soil organic carbon content, soil pH and water content. These properties are important to soil dissolved organic carbon (DOC); however, the effects of biochar on DOC concentration and composition have received little research attention, especially several years after biochar application under field conditions. This study was conducted in a long‐term experimental field where the biochar was only applied once in 2009. The purpose of the study was to investigate the effect of different biochar application rates (0, 30, 60 and 90 t ha?1) on the dynamics of soil water content, DOC concentration and DOC compositions (reducing sugar, soluble phenol and aromatics) over nine samplings during a 12‐month period in 2014. Our results showed that soil water content and DOC concentration varied from 7.1% to 14.5% and 59 to 230 mg C kg?1 soil during the 12 months, respectively. However, the biochar application rates did not significantly (p > 0.05) affect soil water content, DOC concentration and DOC composition at the same sampling period. The DOC concentration across the biochar treatments was positively correlated to soil water content. Moreover, the DOC composition (reducing sugar, soluble phenol or aromatics) and their concentrations were positively correlated to the total DOC concentration. In addition, biochar did not affect soil bulk density, pH, saturated hydraulic conductivity and crop yields. The results indicated that some benefits of biochar to soil may not persist 5 years after the application of biochar under a field condition. 相似文献
200.