全文获取类型
| 收费全文 | 46520篇 |
| 免费 | 2307篇 |
| 国内免费 | 276篇 |
专业分类
| 林业 | 2924篇 |
| 农学 | 2103篇 |
| 基础科学 | 435篇 |
| 7530篇 | |
| 综合类 | 6405篇 |
| 农作物 | 2129篇 |
| 水产渔业 | 2229篇 |
| 畜牧兽医 | 20635篇 |
| 园艺 | 1129篇 |
| 植物保护 | 3584篇 |
出版年
| 2021年 | 357篇 |
| 2020年 | 423篇 |
| 2019年 | 469篇 |
| 2018年 | 1903篇 |
| 2017年 | 1980篇 |
| 2016年 | 1222篇 |
| 2015年 | 657篇 |
| 2014年 | 783篇 |
| 2013年 | 1828篇 |
| 2012年 | 1676篇 |
| 2011年 | 2542篇 |
| 2010年 | 2189篇 |
| 2009年 | 2046篇 |
| 2008年 | 2203篇 |
| 2007年 | 2354篇 |
| 2006年 | 1255篇 |
| 2005年 | 1154篇 |
| 2004年 | 1082篇 |
| 2003年 | 1105篇 |
| 2002年 | 957篇 |
| 2001年 | 1248篇 |
| 2000年 | 1251篇 |
| 1999年 | 927篇 |
| 1998年 | 387篇 |
| 1997年 | 418篇 |
| 1996年 | 341篇 |
| 1995年 | 392篇 |
| 1994年 | 341篇 |
| 1992年 | 691篇 |
| 1991年 | 780篇 |
| 1990年 | 686篇 |
| 1989年 | 740篇 |
| 1988年 | 682篇 |
| 1987年 | 625篇 |
| 1986年 | 666篇 |
| 1985年 | 591篇 |
| 1984年 | 462篇 |
| 1983年 | 412篇 |
| 1979年 | 553篇 |
| 1978年 | 431篇 |
| 1977年 | 374篇 |
| 1976年 | 365篇 |
| 1975年 | 396篇 |
| 1974年 | 459篇 |
| 1973年 | 474篇 |
| 1972年 | 448篇 |
| 1970年 | 366篇 |
| 1969年 | 403篇 |
| 1968年 | 377篇 |
| 1967年 | 367篇 |
排序方式： 共有10000条查询结果，搜索用时 15 毫秒
91.
Abstract. Experiments were started in 1967 to investigate the effects of soil mixing on fen peat soil. Peaty topsoil was mixed with mineral subsoil to a maximum depth of 80 cm at two sites, one with a clay subsoil, the other sand. Mixing was done on a commercial scale with a range of implements. After initial increases, yields of arable crops on both mixed soils were subsequently similar to those on unmixed soil. Residual herbicide activity was enhanced on mixed soils, and evidence of peat conservation was obtained at one site. The practice has not been taken up commercially because of the high capital cost of mixing and lack of serious problems which had been predicted following peat wastage. 相似文献
92.
93.
94.
Distribution of Cytochrome P450-side Chain Cleavage in the Theca Interna Layers of Bovine Small Antral and Cystic Follicles 总被引：1，自引：0，他引：1
Cystic follicle is anovulatory follicular structure that is caused by an endocrine imbalance. The activity of cytochrome P450‐side chain cleavage (P450scc) is essential for the initiation of steroidogenesis in the follicle. The present study was designed to compare the frequency of cells containing P450scc between healthy and atretic small antral follicles, and among several types (I, II and III, classified based on the presence of granulosa layer) of cystic follicles. Paraffin sections of healthy (2–5 mm in diameter), atretic (2–5 mm) and cystic follicles (>25 mm) were immunohistochemically stained with rabbit polyclonal antibody to bovine P450scc. The P450scc‐positive cells were counted in four different regions of the follicles from the apical to the basal side. In small antral follicles and cystic follicles, P450scc‐positive cells were localized in the theca interna layers but not granulosa layers. The P450scc‐positive cell populations decreased in the late atretic follicles compared with the early and advanced atretic follicles at all the regions of follicle. Type III cystic follicles showed significantly lower frequencies of P450scc‐positive cells than those in the types I and II cystic follicles. These results suggest that in both small and cystic follicles in cows, total loss of granulosa cells may be associated with the reduction of frequency of P450scc‐positive cells in theca interna layer. 相似文献
95.
96.
97.
98.
Do Thi Thanh HUONG Vidya JAYASANKAR Safiah JASMANI Hisako SAIDO-SAKANAKA Andrew J. WIGGINTON Marcy N. WILDER 《Fisheries Science》2004,70(3):518-520
99.
100.