全文获取类型
收费全文 | 551篇 |
免费 | 78篇 |
国内免费 | 20篇 |
专业分类
林业 | 14篇 |
农学 | 113篇 |
基础科学 | 11篇 |
15篇 | |
综合类 | 108篇 |
农作物 | 19篇 |
水产渔业 | 2篇 |
畜牧兽医 | 345篇 |
园艺 | 16篇 |
植物保护 | 6篇 |
出版年
2024年 | 1篇 |
2023年 | 19篇 |
2022年 | 19篇 |
2021年 | 20篇 |
2020年 | 45篇 |
2019年 | 27篇 |
2018年 | 21篇 |
2017年 | 22篇 |
2016年 | 28篇 |
2015年 | 30篇 |
2014年 | 31篇 |
2013年 | 33篇 |
2012年 | 33篇 |
2011年 | 32篇 |
2010年 | 24篇 |
2009年 | 17篇 |
2008年 | 24篇 |
2007年 | 25篇 |
2006年 | 14篇 |
2005年 | 16篇 |
2004年 | 10篇 |
2003年 | 10篇 |
2002年 | 7篇 |
2001年 | 8篇 |
2000年 | 8篇 |
1999年 | 13篇 |
1998年 | 6篇 |
1997年 | 8篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 12篇 |
1992年 | 16篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1976年 | 1篇 |
排序方式: 共有649条查询结果,搜索用时 15 毫秒
1.
2.
Selective muscarinic receptor antagonists were used to identify muscarinic receptor subtypes in equine trachealis strips. The M1 receptor antagonist pirenzepine (10–7 mol/L to 3 × 10–5 mol/L) and the M3 receptor antagonist 4-diphenylacetoxy-N-methylpiperidine (4-DAMP, 10–9 mol/L to 3 × 10–7 mol/L3) dose dependently inhibited the contractile responses to electrical field stimulation (EFS) and exogenous acetylcholine (ACh). Schild plots yielded a pA2 value for pirenzepine vs ACh of 6.75 ± 0.09, which is consistent with the affinity for M2 or M3 receptors, and a pA2 value for 4-DAMP vs ACh of 8.47 ± 0.09, which is in agreement with the affinity for M3 receptors. The M2 receptor antagonist gallamine (10–5 mol/L and 10–4 mol/L) did not affect the response of trachealis to exogenous ACh and low-frequency EFS (0.1–2 Hz) but decreased the responses to high-frequency EFS (4–16 Hz). These results suggest that the muscarinic receptors mediating contractions induced by ACh in equine tracheal smooth muscle are of the M3 subtype. The lack of an increase in the response to EFS following gallamine suggests that functional prejunctional inhibitory M2 receptors are not present on the cholinergic nerves innervating equine tracheal smooth muscle. 相似文献
3.
提出了在烟草育种中应用轮回选择方法的必要性,综述了轮回选择改良群体的理论与方法和轮回选择在烟草育种中的应用效果,同时探讨了轮回选择在烟草群体改良中的应用特点和方法。 相似文献
4.
5.
6.
Tamas D. Ambrisko Arnon Gal Jesus N. Sarol Ashley Mitek Christina Braun 《Veterinary anaesthesia and analgesia》2021,48(2):205-212
ObjectiveTo evaluate the influence of reservoir bag types, volumes and previous use on the peak pressures (Pmax) and the times to develop 30 cmH2O pressure (P30) within a nonrebreathing system with a closed adjustable pressure-limiting (APL) valve.Study designIn vitro study using three-way factorial design with repeated measure on one factor.SubjectsA total of 75 new anesthesia reservoir bags (five types, three volumes, five bags from each type × volume). The bag types were reusable latex (RL), disposable latex (DL) and three disposable neoprene (DN-1, DN-2 and DN-3).MethodsEach bag was tested three times (treatments): new, after prestretching and 1 week later. The bags were attached to a Bain system and anesthesia machine with closed APL valve and patient port with O2 flow 2 L minute–1 until Pmax was reached. The Pmax and time to reach P30 values were determined from recorded pressure traces. General linear mixed model analysis was used to examine the effects of bag type, volume and treatment. One-sided 95% upper prediction limits of Pmax were calculated to test the null hypothesis that predicted Pmax of new bags would be ≥ 50 cmH2O for each factor combination.ResultsRL bags were the least and DN-3 bags were the most compliant. Prestretching increased compliance in all bag types. Smaller bags of RL, DL and DN-1 were less compliant than larger ones. The predicted Pmax values were < 50 cmH2O only for DN-3 bags after prestretching. The time to reach P30 was critically low when using 0.5 L bags (median 17 seconds).Conclusions and clinical relevanceTo minimize the risk of barotrauma, highly compliant reservoir bags (e.g. DN-3) are recommended and reusable bags should be avoided. Bags should be prestretched before first use, 0.5 L bags should be avoided and fresh gas flow minimized. 相似文献
7.
8.
9.
10.