全文获取类型
收费全文 | 17749篇 |
免费 | 1151篇 |
国内免费 | 1183篇 |
专业分类
林业 | 1226篇 |
农学 | 1399篇 |
基础科学 | 890篇 |
2773篇 | |
综合类 | 5429篇 |
农作物 | 1400篇 |
水产渔业 | 1110篇 |
畜牧兽医 | 4027篇 |
园艺 | 704篇 |
植物保护 | 1125篇 |
出版年
2024年 | 84篇 |
2023年 | 257篇 |
2022年 | 613篇 |
2021年 | 714篇 |
2020年 | 652篇 |
2019年 | 666篇 |
2018年 | 634篇 |
2017年 | 794篇 |
2016年 | 644篇 |
2015年 | 818篇 |
2014年 | 831篇 |
2013年 | 1091篇 |
2012年 | 1439篇 |
2011年 | 1445篇 |
2010年 | 1202篇 |
2009年 | 1151篇 |
2008年 | 1187篇 |
2007年 | 1044篇 |
2006年 | 874篇 |
2005年 | 728篇 |
2004年 | 515篇 |
2003年 | 420篇 |
2002年 | 406篇 |
2001年 | 286篇 |
2000年 | 268篇 |
1999年 | 193篇 |
1998年 | 72篇 |
1997年 | 55篇 |
1996年 | 65篇 |
1995年 | 67篇 |
1994年 | 45篇 |
1993年 | 50篇 |
1992年 | 48篇 |
1991年 | 41篇 |
1990年 | 47篇 |
1989年 | 54篇 |
1988年 | 43篇 |
1987年 | 51篇 |
1986年 | 31篇 |
1985年 | 39篇 |
1984年 | 33篇 |
1983年 | 32篇 |
1982年 | 19篇 |
1981年 | 20篇 |
1978年 | 24篇 |
1977年 | 22篇 |
1976年 | 30篇 |
1974年 | 20篇 |
1973年 | 26篇 |
1972年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
秦勃 《安徽农业大学学报》2008,(2):102-104
从语境关系顺应、语言结构顺应、动态顺应、意识程度四个方面对礼貌现象的考察说明礼貌具有顺应性。礼貌的顺应性是指在交际活动中, 处于不同心理状态的交际者根据语境变化选择适宜的礼貌策略来表达自己的思想。忽视礼貌的顺应性是礼貌原则存在不足之处的根本原因。 相似文献
992.
993.
994.
In this experiment, seedlings of six indica rice varieties, Nannongxian 2, Changsizhan, Qigui, Zhong 86-44, Zao-xiang 1, and Zhongyu 1 were used. Each of them were transplanted into the Kimura nutrient solution containing 1, 3 , and 10 mg/L K+ , respectively. Plant samples were collected at 3, 5, and 8 leaf stage (Trifoliate stage, Pentafoliate stage, and Octofoliate stage), respectively. 相似文献
995.
996.
Changes in the concentrations of B, Ca, Fe, K, Mg, Mn, Na, P, S, Sr and Zn in the liquid phase in sheep rumen were determined to obtain information on their rate of disappearance from the soluble pool after feeding. Sheep were fed alfalfa (Medicago sativa) hay hourly. The concentration of infused Cr(III)-EDTA into the rumen (over a period of 4 d) was used to establish steady-state conditions, after which feeding was stopped and the rapidly changing elemental concentrations in 30,000 x g ruminal supernatant fluid were determined by plasma emission spectrometry. The concentrations of all elements, apart from Fe, Na and P, decreased in a first-order manner over 5 h after feeding. For one sheep, these concentrations (microM) were: B, 199 to 126; Cr, 184 to 111; Ca, 4,150 to 1,130; K, 51,000 to 28,800; Mn, 11 to 4.2; Mg, 4,190 to 1,810 and Zn, 14 to 7.8. For S, first-order decay was observed over only the 0- to 2-h period (2230 microM to 865 microM). Phosphorus increased from 10.4 to 13.1 mM over the 5-h period, whereas Na remained constant (85 mM); this was attributed to saliva input. Mean half-lives for B (8.8 h), K (7.5 h) and Zn (5.3 h) were similar to those of Cr (6.3 +/- .3 h), the water flow marker. Mean half-lives of Ca (2.6 h), Mg (4.0 h), Mn (3.3 h), Sr (3.3 h) and S (1.8 h) were shorter (P less than .01) than that of the Cr marker.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
997.
A L Bertone G L Cockerell R E Lee T S Stashak 《American journal of veterinary research》1990,51(9):1471-1475
Light microscopy, morphometry, and scanning electron microscopy were used to examine the mucosal morphologic features of 7 intestinal specimens (3 from the small intestine; 4 from the large intestine) from each of 8 horses 1 year after sham operation (group 1; n = 3) or extensive large-colon resection (group 2; n = 5). Qualitative light microscopic examination did not reveal differences between groups, but morphometry revealed significantly (P less than 0.05) greater intercrypt area and distance in horses with colon resection and this was most pronounced in the cecum and remaining right ventral and dorsal colon. Crypt area and depth were similar for horses with colon resection and sham operation (P greater than 0.05). Qualitative evaluation of the scanning electron micrographs revealed more prominent crypt orifices in the large intestine of horses with colon resection. The larger intercrypt distance in the colon of horses with resection was not an obvious feature of the qualitative evaluation of the surface with scanning electron microscopy. Small intestinal morphologic features were variable and significant differences were not detected between horses with sham operation and colon resection. Horses adapted to extensive large-colon resection within 1 year by increasing the absorptive (intercrypt) surface area of the remaining large intestine. 相似文献
998.
999.
探讨了Markov转移矩阵和GM(1,1)灰色模型预测陕西森林火灾趋势的方法。并预测2000年前,森林火灾基本处于B级稳定状态,最小级A出现于1998年,最大级C可能出现于2000年。 相似文献
1000.