全文获取类型
收费全文 | 56249篇 |
免费 | 2234篇 |
国内免费 | 5348篇 |
专业分类
林业 | 6627篇 |
农学 | 8292篇 |
基础科学 | 4639篇 |
9068篇 | |
综合类 | 14307篇 |
农作物 | 2988篇 |
水产渔业 | 2288篇 |
畜牧兽医 | 10109篇 |
园艺 | 1702篇 |
植物保护 | 3811篇 |
出版年
2024年 | 131篇 |
2023年 | 455篇 |
2022年 | 1282篇 |
2021年 | 1982篇 |
2020年 | 1720篇 |
2019年 | 1797篇 |
2018年 | 1335篇 |
2017年 | 1832篇 |
2016年 | 1824篇 |
2015年 | 2494篇 |
2014年 | 2273篇 |
2013年 | 2718篇 |
2012年 | 3449篇 |
2011年 | 3587篇 |
2010年 | 3187篇 |
2009年 | 2951篇 |
2008年 | 2735篇 |
2007年 | 2720篇 |
2006年 | 2655篇 |
2005年 | 3356篇 |
2004年 | 1799篇 |
2003年 | 1405篇 |
2002年 | 898篇 |
2001年 | 955篇 |
2000年 | 1038篇 |
1999年 | 1488篇 |
1998年 | 1202篇 |
1997年 | 1012篇 |
1996年 | 943篇 |
1995年 | 875篇 |
1994年 | 871篇 |
1993年 | 773篇 |
1992年 | 829篇 |
1991年 | 726篇 |
1990年 | 653篇 |
1989年 | 537篇 |
1988年 | 431篇 |
1987年 | 301篇 |
1986年 | 235篇 |
1985年 | 192篇 |
1984年 | 141篇 |
1983年 | 119篇 |
1979年 | 143篇 |
1975年 | 139篇 |
1974年 | 135篇 |
1973年 | 119篇 |
1972年 | 141篇 |
1971年 | 121篇 |
1968年 | 119篇 |
1967年 | 126篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
针对制造业加工现场的环境特点,分析了微机控制系统的干扰来源和途径,介绍了实用的抗干扰措施。实践证明:这些软硬件抗干扰措施的综合运用,使自动化加工中微机控制系统的稳定性得到了较大的提高。 相似文献
22.
We compared the results of the ACTH stimulation tests with measurements of alkaline phosphatase and serum cholesterol during Lysodren therapy in 23 dogs with pituitary-dependent hyperadrenocorticism. The ACTH stimulation test proved to be a very sensitive parameter, by which the extent of Lysodren under- or overdosage could be reliably estimated. On the other hand, regulation of the individual Lysodren requirement was not possible by measuring AP and serum cholesterol only. However, it is highly probable that those two parameters can be used to evaluate the general state of metabolism, and they appear to be of prognostic value when greatly elevated. 相似文献
23.
对24例成黄牛的前肢脚部动脉采用解剖,铸型和动脉造影等方法进行研究。结果:1。中国黄牛前脚部掌侧动脉主干为正中动脉,指掌侧第Ⅱ总动脉,在近指节骨远端指掌侧第Ⅲ总动脉分为第Ⅲ,Ⅳ指掌侧固有轴动脉,经远指节骨轴孔入骨质管。2.指掌侧第Ⅲ总动脉在掌骨远端分出拽第Ⅱ总动脉,在近指节骨远端指掌侧第Ⅲ总动脉,分出背侧支和掌侧支,后者分别与指掌侧第Ⅱ,Ⅳ总动脉吻合形居近指节深弓,在掌侧支稍下方,指掌侧第2,Ⅳ指 相似文献
24.
利用犬温热,细小病毒性肠炎,犬传染性肝炎,狂犬病等弱毒株,以香菇多糖和动物的核糖,多肽做为免疫增强剂,对异源动物羊,猪,犊牛,家兔进行了免疫应答,筛选出了猪做为异源免疫动物。在免疫增强剂的参与下,完成了多次免疫应答,达到了理想的免疫球蛋白(IgG),通过试验摸清了该制剂的免疫程序,确定了生产工艺,经重复性试验,稳定性试验及含量测定,以及临床应用试验和现志应用试验均达以了预期效果,该制剂经冷冻干燥后 相似文献
25.
The technique of cystocentesis in dogs and cats was studied. The indications and contraindications of this method are discussed, using illustrations. 相似文献
26.
G Breves R Zitnan B Schr?der C Winckler H Hagemeister K Failing J Voigt 《Archives of Animal Nutrition》2002,56(5):371-377
In a previous study we found a positive correlation between early weaning in calves and morphological parameters which were indicative of ruminal development, i.e. the length and width of the papillae. The objective of the present study was to determine to what extent this observation could be reflected by modulations of absorptive and secretory functions of the rumen mucosa. For this purpose the short-circuit currents (Isc) as a measure of electrogenic net ion fluxes and the transepithelial conductances (G(T)) as a measure of the overall tissue permeability were measured in vitro applying the Ussing-chamber technique. Simultaneously, the unidirectional flux rates of sodium and chloride across rumen wall epithelia were determined in the absence of electrochemical gradients. Under these conditions, significant positive net flux rates (Jnet) clearly indicate active mechanisms for electrolyte absorption. For the experiments 12 male Holstein calves 7 d of age were assigned to three groups of 4 animals each: milk group (I, slaughtered after 6 weeks of age), late weaning group (II, slaughtered after 9 weeks of age) and early weaning group (II, weaned after 6 weeks of age and slaughtered after 9 weeks of age). Whereas G(T) values remained unaffected by different age and feeding, Isc values were significantly affected by early weaning but were not influenced by age. Irrespective of weaning time active absorption of Na+ tended to be higher by about 60% in 9 weeks old animals. Active absorption of chloride was significantly increased in milk fed 9 weeke old calves and this effect was further stimulated by early weaning. In conclusion, the data show an increasing active Na+ absorption with age in calf rumen that could not be influenced by early weaning. Similarly, active Cl- absorption was initially increased during postnatal development and this effect could be stimulated further by early weaning. 相似文献
27.
鹌鹑遗传资源开发与产业展望 总被引:6,自引:0,他引:6
目前,全世界鹌鹑的饲养量达10亿只上,我国饲养量近2亿只.从数量上讲,鹌鹑在家禽行业占次要地位,但是在一些国家,鹌鹑产业正产生着重要的影响,并且鹌鹑作为一种模型动物已得到了较为广泛的应用. 相似文献
28.
29.
30.