全文获取类型
收费全文 | 168590篇 |
免费 | 9258篇 |
国内免费 | 100篇 |
专业分类
林业 | 7574篇 |
农学 | 5590篇 |
基础科学 | 1000篇 |
21149篇 | |
综合类 | 26798篇 |
农作物 | 6373篇 |
水产渔业 | 8448篇 |
畜牧兽医 | 87936篇 |
园艺 | 2159篇 |
植物保护 | 10921篇 |
出版年
2019年 | 1655篇 |
2018年 | 2580篇 |
2017年 | 2867篇 |
2016年 | 2647篇 |
2015年 | 2327篇 |
2014年 | 2854篇 |
2013年 | 6775篇 |
2012年 | 5124篇 |
2011年 | 6036篇 |
2010年 | 4087篇 |
2009年 | 4177篇 |
2008年 | 6039篇 |
2007年 | 5830篇 |
2006年 | 5514篇 |
2005年 | 5090篇 |
2004年 | 4869篇 |
2003年 | 4909篇 |
2002年 | 4546篇 |
2001年 | 5615篇 |
2000年 | 5436篇 |
1999年 | 4400篇 |
1998年 | 1750篇 |
1997年 | 1745篇 |
1996年 | 1628篇 |
1995年 | 1928篇 |
1994年 | 1636篇 |
1993年 | 1670篇 |
1992年 | 3337篇 |
1991年 | 3452篇 |
1990年 | 3432篇 |
1989年 | 3488篇 |
1988年 | 3158篇 |
1987年 | 3177篇 |
1986年 | 3146篇 |
1985年 | 2983篇 |
1984年 | 2447篇 |
1983年 | 2178篇 |
1982年 | 1479篇 |
1979年 | 2108篇 |
1978年 | 1692篇 |
1977年 | 1490篇 |
1976年 | 1451篇 |
1975年 | 1524篇 |
1974年 | 1882篇 |
1973年 | 1890篇 |
1972年 | 1881篇 |
1971年 | 1703篇 |
1970年 | 1712篇 |
1969年 | 1605篇 |
1967年 | 1404篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
A. Bhogal A. Bhogal M.A. Shepherd D.J. Hatch L. Brown S.C. Jarvis 《Soil Use and Management》2001,17(3):163-172
Abstract. The ability of two nitrogen cycle models, of contrasting complexity, to predict N mineralization from a range of grassland soils in the UK, was evaluated. These were NCYCLE, a simple mass balance model of the N cycle in UK grasslands, and CENTURY, a more complex model simulating long-term C, N, P & S dynamics in grassland ecosystems. The models were tested using field measurements of net N mineralization from a range of grassland soils (differing in soil type, history & management practice), obtained over a 2 year period using a soil core incubation technique. This method was considered to measure the total net release of mineral N from the soil organic matter over a specified time, including N which may have been recycled several times. NCYCLE consistently under-estimated mineralization rates at all sites. By contrast, there was some correlation between CENTURY predictions of net N mineralization and field measurements. This may have reflected the different abilities of the two models to simulate N recycling. Neither model, however, was able to predict adequately the effect of cultivation and reseeding on net N mineralization. 相似文献
12.
13.
14.
15.
16.
17.
18.
19.
20.
Gia Klauss Gheorge M Constantinescu 《Veterinary Clinics of North America: Small Animal Practice》2004,34(3):777-800
The parasympathetic and sympathetic divisions of the autonomic nervous system are involved in homeostatic control of a wide variety of ocular functions, including accommodation, pupillomotor control, lacrimation, eyelid position, and aqueous humor production. Familiarity with the functional anatomy of the autonomic nervous system is paramount to the understanding and application of the large number of autonomic drugs used in veterinary ophthalmology. The cholinergic and adrenergic agents discussed in this article are commonly employed to facilitate routine ophthalmic examination, in the diagnosis of autonomic dysfunction, and in the treatment of a variety of ocular diseases. 相似文献