全文获取类型
收费全文 | 1643篇 |
免费 | 68篇 |
国内免费 | 82篇 |
专业分类
林业 | 277篇 |
农学 | 100篇 |
基础科学 | 99篇 |
200篇 | |
综合类 | 796篇 |
农作物 | 70篇 |
水产渔业 | 27篇 |
畜牧兽医 | 145篇 |
园艺 | 36篇 |
植物保护 | 43篇 |
出版年
2024年 | 11篇 |
2023年 | 26篇 |
2022年 | 34篇 |
2021年 | 42篇 |
2020年 | 40篇 |
2019年 | 47篇 |
2018年 | 29篇 |
2017年 | 37篇 |
2016年 | 74篇 |
2015年 | 47篇 |
2014年 | 86篇 |
2013年 | 90篇 |
2012年 | 127篇 |
2011年 | 119篇 |
2010年 | 94篇 |
2009年 | 86篇 |
2008年 | 87篇 |
2007年 | 96篇 |
2006年 | 99篇 |
2005年 | 78篇 |
2004年 | 59篇 |
2003年 | 47篇 |
2002年 | 42篇 |
2001年 | 40篇 |
2000年 | 38篇 |
1999年 | 33篇 |
1998年 | 27篇 |
1997年 | 20篇 |
1996年 | 20篇 |
1995年 | 28篇 |
1994年 | 22篇 |
1993年 | 17篇 |
1992年 | 18篇 |
1991年 | 10篇 |
1990年 | 11篇 |
1989年 | 5篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1984年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有1793条查询结果,搜索用时 15 毫秒
1.
2.
3.
以ArcGIS 10.2.2浮动版为平台,结合实例阐述在宗地结构中用宗地编辑器分割宗地,从宗地结构中导出图层,将图层和从宗地结构中导出的图层加载到ArcMap内容列表中,在ArcMap内容列表中用裁剪面工具捕捉导出图层的端点、折点分割图层,实现林地面积精确分割。认为该方法在林业工作中是一种实用的方法。 相似文献
4.
栾嘉 《四川畜牧兽医学院学报》2008,(2):194-196
高素质的青年编辑人才是科技期刊发展的关键力量,其中创新素质起着举足轻重的作用。青年编辑在成长过程中,应该以正确理解科技期刊中的创新性和科技期刊编辑的刨新素质为前提,不断提高人文修养、注重知识的广度和深度、加强自身专业修养、加强主观能动性,从而达到提高创新素质的目的。 相似文献
5.
草地农业信息资源数据库利用Java技术和Web方式实现,分析了用户需求和系统优势,阐明了数据库的设计思路、结构及系统实现方法。 相似文献
6.
科学、艺术等文化现象是人类符号活动的结果.普通编辑学的确立与发展应以符号世界为论域,编辑理论建设应充分重视对符号学研究成果及方法的借鉴。结构主义是认识论主体的认识模式,是编辑学术(艺术)把关的钥匙。科技编辑的学术把关和和文艺编辑的艺术把关可分为不同层面,符号本质是这两大类编辑的共同点,由此两者相融合;同时,两类编辑理论建设对人类文化成果的吸纳也各有侧重。 相似文献
7.
C.‐C. Gelfert M. Passfeld A. Löptien N. Montag W. Baumgartner R. Staufenbiel 《The Veterinary quarterly》2013,33(4):130-139
Summary This study was initiated to investigate the influence of a daily dose of anionic salts (AS) above the valid upper limit at present on metabolism of dairy cows. Eleven non‐pregnant and non‐lactating Holstein‐Friesian crossbred cows with a permanent rumen cannula were used in a study with a controlled feeding design. The initial daily dose was 2500 meq/day, which resulted in a Dietary Cation Anion Difference (DCAD) of ‐211 meq/kg dry matter. Every seven days, the daily dose was raised by 500 meq. If a cow stopped eating, the application of AS was stopped and these cows were monitored over the next seven days. On day 30 another batch of hay, having the same DCAD but higher concentrations of minerals and energy, was fed. Blood and urine samples were taken to monitor acid‐base balance and calcium concentrations. Acid‐base balance was strongly influenced by AS. Blood pH dropped steadily and reached values around 7.23. Urine pH dropped quickly below 6 and remained at that level regardless of the increased dosage of AS. Net acid base excretion (NABE) fell continuously with the increase of the dosage of AS and reached values below ‐200 mmol/l. Calcium concentrations in the serum were nearly stable, but those in urine increased sharply and remained on an elevated level with increasing doses of AS. A few days before the individual cow's refusal of feed intake, calcium excretion in urine decreased. The majority of cows stopped eating while consuming a diet containing 3500 to 4000 meq AS except two animals who consumed up to 6000 meq/day AS but they received the better hay in the second half of the treatment period. In this time pH in blood increased slowly. NABE remained stable on a low level at ‐100 mmol/l. The results showed that with an increasing amount of AS fed the risk of clinical acidosis increased. The decreasing urine concentrations of calcium indicate a breakdown of the compensation capability of the single cow. Besides the dose of AS fed, the quality of the feed stuff might be another factor concerning the tolerance of cows against AS. 相似文献
8.
西吉县在肉牛基地建设区,大力推广畜牧科技,促进了养牛产业的提升和发展。本文对重点推广的技术有细管冻精直把式输精技术、玉米秸秆青贮技术、尿素氨化秸秆技术、紫花苜蓿种植技术和肉牛短期育肥技术等的具体做法进行了论述。 相似文献
9.
10.
Sidley JA Atkins CE Keene BW DeFrancesco TC 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2002,16(5):541-546
Percutaneous balloon pericardiotomy (PBP) has been performed in people and in a small number of dogs as a treatment for recurrent pericardial effusion with tamponade (PET). We performed this technique on 6 dogs with recurrent PET (5 with heart base tumors and 1 with no identifiable mass). Under general anesthesia and fluoroscopic guidance, a balloon-dilating catheter (diameters 14-20 mm) was introduced percutaneously at the 5th intercostal space through a sheath-introducing catheter, positioned across the parietal pericardium, and inflated 3 times. No dog experienced serious complications. The procedure was considered successful in 4 of 6 dogs. One dog is still alive without recurrence of PET 1 year after the procedure. Three dogs died of unrelated disease without recurrence of PET 5. 19, and 32 months after the procedure. The procedure was not beneficial in 1 dog that was euthanized 9 weeks later because of recurrence of pleural and abdominal effusion thought to be secondary to PET. One dog may have temporarily benefited but developed symptomatic PET 6 months after PBP. PBP appears to be a safe, economical, and potentially effective palliative treatment for recurrent PET and is a reasonable, less invasive alternative to surgery for dogs with recurrent PET, especially effusions caused by heart base tumors and possibly idiopathic pericardial effusion. Premature closure of the stoma is a potential cause for long-term failure and was thought to have been responsible for the recurrence of clinical signs in 2 dogs. 相似文献