全文获取类型
收费全文 | 97042篇 |
免费 | 4713篇 |
国内免费 | 10029篇 |
专业分类
林业 | 10491篇 |
农学 | 13030篇 |
基础科学 | 7956篇 |
14395篇 | |
综合类 | 33169篇 |
农作物 | 5426篇 |
水产渔业 | 3944篇 |
畜牧兽医 | 13640篇 |
园艺 | 3776篇 |
植物保护 | 5957篇 |
出版年
2024年 | 401篇 |
2023年 | 1167篇 |
2022年 | 2997篇 |
2021年 | 3895篇 |
2020年 | 3539篇 |
2019年 | 3590篇 |
2018年 | 2510篇 |
2017年 | 3725篇 |
2016年 | 3283篇 |
2015年 | 4538篇 |
2014年 | 4399篇 |
2013年 | 5327篇 |
2012年 | 6638篇 |
2011年 | 7304篇 |
2010年 | 6734篇 |
2009年 | 6141篇 |
2008年 | 5892篇 |
2007年 | 5666篇 |
2006年 | 5059篇 |
2005年 | 4521篇 |
2004年 | 2256篇 |
2003年 | 1924篇 |
2002年 | 1920篇 |
2001年 | 1874篇 |
2000年 | 1953篇 |
1999年 | 2077篇 |
1998年 | 1751篇 |
1997年 | 1464篇 |
1996年 | 1333篇 |
1995年 | 1268篇 |
1994年 | 1208篇 |
1993年 | 1104篇 |
1992年 | 955篇 |
1991年 | 821篇 |
1990年 | 685篇 |
1989年 | 548篇 |
1988年 | 394篇 |
1987年 | 259篇 |
1986年 | 139篇 |
1985年 | 104篇 |
1984年 | 72篇 |
1983年 | 57篇 |
1982年 | 52篇 |
1981年 | 41篇 |
1980年 | 32篇 |
1979年 | 22篇 |
1978年 | 16篇 |
1977年 | 14篇 |
1965年 | 13篇 |
1964年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
1.
农产品物流模式已成为决定我国农业经济整体水平的重要因素,我国农产品物流发展缓慢始终是我国农业可持续发展的瓶颈。当前在国际市场上已经形成了3种典型的农产品物流模式,其成功的管理模式与经验都值得我国借鉴与学习。该文主要分析国内外农产品物流模式,针对我国当前国情,建议建立起中国式的农产品物流组织。 相似文献
2.
Impact of grassland contract policy on soil organic carbon losses from alpine grassland on the Qinghai–Tibetan Plateau 下载免费PDF全文
J. Cao Y. Gong E. T. Yeh N. M. Holden J. F. Adamowski R. C. Deo M. Liu J. Zhou J. Zhang W. Zhang S. Zhang D. Sheng S. Yang X. Xu M. Li Q. Feng 《Soil Use and Management》2017,33(4):663-671
Carbon storage in the soils on the Qinghai–Tibetan Plateau plays a very important role in the global carbon budget. In the 1990s, a policy of contracting collective grasslands to smaller units was implemented, resulting in a change from the traditional collective grassland management to two new management patterns: a multi‐household management pattern (MMP: grassland shared by several households without enclosures) and a single‐household management pattern (SMP: grassland enclosed and used by only one household). In 2016, 50 MMP and 54 SMP winter pastures on the Qinghai–Tibetan Plateau were sampled to assess the differences in soil organic carbon (SOC) between the two management patterns. Results showed that average SOC was significantly greater under MMP than under SMP, with an estimated 0.41 Mg C/ha/yr lost due to SMP following the new grassland contract. Based on the government's grassland policy, four grassland utilization scenarios were developed for both summer and winter pastures. We found that if the grassland were managed under SMP, likely C losses ranged between 0.31 × 107 and 6.15 × 107 Mg C/yr across the Qinghai–Tibetan Plateau relative to MMP, which more closely resembles pre‐1990s grassland management. Previous estimates of C losses have only considered land use change (with cover change) and ignored the impacts driven by land management pattern changes (without cover change). The new data suggest that C losses from the Qinghai–Tibetan Plateau are greater than previously estimated, and therefore that the grassland contract policy should be reviewed and SMP households should be encouraged to reunite into the MMP. These findings have potential implications for land management strategies not only on the Qinghai–Tibetan Plateau but also other grazing regions globally where such practices may exist. 相似文献
3.
针对当前传统人工晾晒海贝柱效率低下、容易造成污染等问题。设计了海贝柱自动晾晒机械,采用阶梯式晾晒生产线对湿海贝柱分级晾晒,多条晾晒生产线分时、高效的工作,机器上方设有遮板以保证晾晒作业不被污染而且不受天气条件的影响。整机采用stm32单片机、传感器等技术实现自动化作业,机器控制系统监测到生产线发生故障或海贝柱出现堆积时会立即停止工作以便于检查故障、减少损失。试验结果表明:机械晾晒不会造成海贝柱内的营养成分的流失,机械晾晒海贝柱的干基含水率达到30%仅需12h,机械晾晒海贝柱能节省大量的干燥时间,显著的提高了晾晒效率,避免了人工晾晒过程导致的二次污染和损失。该研究为海贝柱自动晾晒机械的研制提供了技术参考。 相似文献
4.
聚丙烯酰胺凝胶电泳法鉴定禽呼肠孤病毒 总被引:1,自引:0,他引:1
从感染禽呼肠孤病毒的细胞中,以SDS和酚提取病毒核酸,通过聚丙烯酰胺凝胶电泳(PAGE)法将分节段的核酸分开,经银染色显示,呈3-3-1-3分布,此法可用于禽呼肠孤病毒的快速检测、鉴定。同样方法未能使传染性法氏囊病毒核酸显示。 相似文献
5.
6.
Indices of the tomato seedling quality maintenance level after production before field planting were studied through simulated experiments, small--scale operation, indoor analyses and measurements, and field observation. The results showed that under simulated shipping and storage conditions, seedling quality change following different durations (days) of shipping and storage was correlated significantly or even very significantly with certain physiological and morphological indices. With various measured indices following different periods of shipping and storage treatment subjected to multinomial successive regressive correlation analysis, the principal factors influencing seedling quality maintenance level are identified to be chlorophyll content→dry short weight→ leaf freshness index in order of their importance. Significance analysis with multinomial fitted equation indicated that correlations between any one of above three factors and the growth index after field planting reached very significant difference level. 相似文献
7.
8.
W W Chan K Y Chen H Liu L S Wu J H Lin 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2001,63(10):1057-1062
Since the International Society of Veterinary Acupuncture (IVAS) was founded in 1974, acupuncture (AP) has received greater acceptance by veterinary professionals throughout the world. This article introduces some important animal diseases that respond well to AP therapy. These include resuscitation of small animals, treatment of anoestrous gilts and sows, bovine reproductive disease, canine vertebral problems and equine backpain, etc. Conventional medicine considers these to be difficult cases to treat. Veterinarians have become more aware of the benefits of AP especially for those diseases, thanks to the efforts of experienced practitioners and scientists, and the many published reports on veterinary AP that have introduced some good indications for AP therapy in veterinary practice. Possible mechanisms behind the effectiveness of AP are discussed. This article aims to introduce veterinarians to good indications for AP to initiate their interest in the practice of AP. Although this is a rapidly expanding field, a long march must begin with one step. We wish this article to be the shoes for such a march. For more information on veterinary AP, contact IVAS , P.O. Box 1478, Longmont, CO.. 80502, USA (http://www.ivas.org), or your national veterinary acupuncture society (http://www.komvet.at/ ivadkom/vapsocs.htm). 相似文献
9.
10.