全文获取类型
收费全文 | 12200篇 |
免费 | 811篇 |
国内免费 | 1362篇 |
专业分类
林业 | 1012篇 |
农学 | 886篇 |
基础科学 | 827篇 |
1506篇 | |
综合类 | 5394篇 |
农作物 | 764篇 |
水产渔业 | 712篇 |
畜牧兽医 | 1608篇 |
园艺 | 929篇 |
植物保护 | 735篇 |
出版年
2024年 | 103篇 |
2023年 | 287篇 |
2022年 | 622篇 |
2021年 | 608篇 |
2020年 | 607篇 |
2019年 | 606篇 |
2018年 | 460篇 |
2017年 | 657篇 |
2016年 | 538篇 |
2015年 | 672篇 |
2014年 | 701篇 |
2013年 | 836篇 |
2012年 | 1120篇 |
2011年 | 1084篇 |
2010年 | 922篇 |
2009年 | 839篇 |
2008年 | 837篇 |
2007年 | 714篇 |
2006年 | 512篇 |
2005年 | 406篇 |
2004年 | 232篇 |
2003年 | 180篇 |
2002年 | 163篇 |
2001年 | 165篇 |
2000年 | 147篇 |
1999年 | 78篇 |
1998年 | 60篇 |
1997年 | 33篇 |
1996年 | 27篇 |
1995年 | 23篇 |
1994年 | 25篇 |
1993年 | 28篇 |
1992年 | 23篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1965年 | 1篇 |
1964年 | 3篇 |
1963年 | 1篇 |
1962年 | 3篇 |
1956年 | 7篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 462 毫秒
111.
112.
通过Rusitec-s体外发酵系统研究不同粒度猫尾草对羔羊体外发酵参数与微生物数量的影响,选取6种不同粒度(1.00、2.36、3.35、4.75、8.00和12.50 mm)的猫尾草作为试验饲粮的纤维来源,按照猫尾草的粒度将试验分为6个处理组,每个处理4个重复,利用Rusitec-s型人工瘤胃模拟装置进行48 h体外发酵,测定养分降解率、发酵参数及发酵液中6种微生物菌群的拷贝数。结果表明:与其他处理组相比,2.36 mm组显著提高了体外中性洗涤纤维降解率(IVNDFD)、丁酸、异丁酸、戊酸、异戊酸摩尔比和溶纤维丁酸弧菌(B. f)数量(P<0.05),且显著降低总产甲烷菌(TMe)数量(P<0.05)。总菌(TB)与氨态氮(NH3-N)浓度、乙酸摩尔比呈正相关(R2=0.84,P=0.038;R2=0.88,P=0.021);B. f数量与丙酸摩尔比呈正相关(R2=0.82,P=0.045),且与pH呈负相关(R2=-0.98,P=0.001);TMe数量与体外粗蛋白质降解率(IVCP... 相似文献
113.
114.
Using non-parameter test and multinomial logit regression, this paper studies the dividend policy and behavior empirically. The results show that the change of the earnings of firms affects their dividend policy. When the EPS of the firms increase, the probability of choosing not to pay cash dividend is maximal, yet when the EPS of the firms decrease, many firms choose not to pay cash dividend or choose to increase DPS, so that the information that the relevant firms have great expectation is transmitted to the market. Furthermore, this paper also finds that the successiveness of the dividend policy of the listed firms in China is not good. 相似文献
115.
116.
In the analysis of cognition of human brain,the fMRI is often used.Corelation is a common method in fMRI data detecting,but its ability should be improved.Based on the Canonical Correlation Analysis(CCA),the temporal correlation and spatial correlation are used together to detect the activated area in the fMRI data.By the application of the method in simulation data and fMRI data,it shows that this method is effective in the detecting. 相似文献
117.
Based on the analysis and study on some existed models for two-dimensional Guillotine Cutting-Stock problem, it is pointed out that some kinds of the models may miss some good cutting patterns,and some may result in inadequate solutions because of only considering the patterns with the smallest waste. A kind of revised two-dimensional cutting-stock models are developed,which transform the two-dimensional problem into the one-dimensional one using the dimension-decreasing heuristic method and whose initial patterns are considered comprehensively. In this kind of models, not only the least waste,but also the other constraints,such as the demands and the relative area of the order plates are considered. 相似文献
118.
According to the graphics characteristics of metallic doors & windows design and based on the research of graphics dimension restriction problems. This paper provides a new method for parameterized design of metallic doors & windows in virtue of expression solution. In this method, the restrictions of graphic elements have been changed into the parameter expressions of sizes and positions of graphic elements. Through the calculation of such expressions, the parameter driven method has been reached. Thus the parameterization of graphics can be easier and quicker than before. It can be used to setup the open parameterized graphics libraries. 相似文献
119.
Two dimensional Optimum Cutting Stock is a NP complicated problem. Each of optimum software gets the cutting results by using proximate and heuristic methods. But different optimum methods and their optimum software may not realize perfect effect according to certain data framework. Furthermore, enterprises can not buy lots of optimum software to choose the most optimized plan. Because of such problems, this paper provides a two dimensional optimum cutting stock method based on Internet and offers the real implementing technique of such method. The experiments, show that this method promotes the general optimum effect of two dimensional optimum cutting stock greatly. 相似文献
120.