全文获取类型
收费全文 | 10374篇 |
免费 | 768篇 |
国内免费 | 654篇 |
专业分类
林业 | 1210篇 |
农学 | 590篇 |
基础科学 | 115篇 |
606篇 | |
综合类 | 5211篇 |
农作物 | 183篇 |
水产渔业 | 1166篇 |
畜牧兽医 | 1520篇 |
园艺 | 1022篇 |
植物保护 | 173篇 |
出版年
2024年 | 66篇 |
2023年 | 142篇 |
2022年 | 210篇 |
2021年 | 272篇 |
2020年 | 294篇 |
2019年 | 353篇 |
2018年 | 200篇 |
2017年 | 342篇 |
2016年 | 406篇 |
2015年 | 334篇 |
2014年 | 498篇 |
2013年 | 541篇 |
2012年 | 781篇 |
2011年 | 806篇 |
2010年 | 620篇 |
2009年 | 652篇 |
2008年 | 623篇 |
2007年 | 640篇 |
2006年 | 557篇 |
2005年 | 480篇 |
2004年 | 407篇 |
2003年 | 338篇 |
2002年 | 262篇 |
2001年 | 274篇 |
2000年 | 247篇 |
1999年 | 196篇 |
1998年 | 178篇 |
1997年 | 141篇 |
1996年 | 166篇 |
1995年 | 163篇 |
1994年 | 124篇 |
1993年 | 107篇 |
1992年 | 101篇 |
1991年 | 86篇 |
1990年 | 69篇 |
1989年 | 51篇 |
1988年 | 34篇 |
1987年 | 14篇 |
1986年 | 9篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1956年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
972.
挖坑机造林使用效果分析 总被引:1,自引:0,他引:1
童庆辉 《林业机械与木工设备》2011,39(9)
分析了BFW490型背负式挖坑机在福建省三明市梅列区陈大镇林场挖坑造林的使用效果。结果表明:利用挖坑机造林能够大幅度提高工作效率,当挖坑直径为200mm(以下简称1200)和300ram(以下简称1300)时的工效分别是人工挖坑处理(以下简称CKJL)的5.40倍和4.78倍。每667m^2(亩)植树造林单挖坑环节1200、J300处理比CKR分别节省1.38和1.36工日;投入成本j200、j300仅为CKR的40.4%和44.4%,72004300可以减少投入成本55.75元和52.01元。不同处理造林10年生生长量存在差异,挖坑采用j200、j300处理与CKR处理相比平均胸径分别提高了2.4%和4.8%;平均树高分别提高了3.8%和1.3%;蓄积量都提高了12.9%。在闽西北山地使用挖坑机造林是一条切实可行的造林新途径。 相似文献
973.
974.
中国森林公园旅游发展效率的比较与分析 总被引:3,自引:0,他引:3
借助数据包络分析方法(DEA),利用2003-2008年的数据,对我国森林公园发展效率进行研究,为我国森林公园旅游资源的优化配置和运行效率的提高提供参考依据.测算技术效率、纯技术效率、规模效率以及Malmquist全要素生产率(TFP),比较中国31个省区间和东、中、西三大区域间的效率及TFP增长率.结果显示:省区间比较,上海、浙江等地区的效率最高,贵州、山西等地区的TFP增长率最高;三大区域间比较,东部地区的效率最高,中部地区的TFP增长率最大,西部地区的效率和TFP增长率都最低.最后,从要素投入、旅游吸引力、地方经济发展水平等几个方面对影响效率大小及其差异的原因进行理论上的探讨,提出继续加大对中西部地区资金扶持、对森林公园进行技术指导和人员培训等提高效率的对策. 相似文献
975.
6,7-Dimethylesculetin (D), geniposide (G) and rhein (R) are the three major active ingredients of Yin-Chen-Hao-Tang (YCHT), a famous Chinese herbal formula, which has been shown to be clinically effective for treating hepatic injury (HI) syndrome. The present study was conducted to investigate the therapeutic and synergistic effects of COC (combination of D, G and R) on HI rats by combining pharmacokinetic with biochemical analysis strategy. Plasma was analyzed by using reversed-phase high performance liquid chromatography (RP-HPLC). Principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) models were built to evaluate the therapeutic and synergistic effects of COC at the biochemical level. Here, we report that the COC combination could increase the plasma level, slow elimination rate, exert a more robust therapeutic effect than any one or two of the three individual compounds by hitting multiple targets in a rat model of HI. Overall, this beneficially accounts for the popular view that traditional Chinese medicine (TCM) formula usually takes multi-component to exert their therapeutic effects. We suggest that dissecting the mode of action of clinically effective formula to be capable of producing a sufficient effect at low doses. 相似文献
976.
Shuang-Huang-Lian (SHL), a traditional Chinese formula containing Lonicerae japonicae flos (LJF), Scutellariae radix (SR) and Forsythiae fructus (FF), is commonly used to treat acute upper respiratory tract infection, acute bronchitis and light pneumonia. Forsythoside A is one of the main active ingredients in Forsythiae fructus, a key herb in SHL. In the present study, effects of different compositions in SHL on the intestinal absorption of forsythoside A were investigated. The observations from in situ intestinal circulation model showed that A/%(h− 1) of forsythoside A in FF + LSF, FF + SR and SHL were all reduced greatly compared with that in FF. However, in pharmacokinetics study, Cmax and AUC0 → 1440 of forsythoside A all increased and T1/2 prolonged in SHL, FF + LJF and FF + SR compared with FF. The results indicated that the different compositions of SHL decreased absorption but increased bioavailability of forsythoside A, which may be related to its metabolism inhibited in intestine or liver. 相似文献
977.
Invasive plants are one of the greatest threats to endangered insect species and a major threat to Lepidoptera in eastern North America. We investigated the effects of the invasive shrub Chinese privet (Ligustrum sinense) and two methods (mulching or hand-felling) of removing it from riparian forests on butterfly communities and compared them to untreated, heavily invaded control plots and to “desired future condition” forests that never had extensive privet cover. Privet mulching resulted in nearly twice as many butterflies as privet felling and both treatments had more butterflies two years after privet removal than untreated control plots. Butterfly communities on control plots differed from those on the two treatments and the desired future condition forests. A number of forest characteristics were evaluated but only herbaceous plant cover (excluding privet) was positively correlated with butterfly abundance, diversity and evenness. The Carolina satyr, Hermeuptychia sosybius, was the best indicator of forests where privet had never invaded. Removing Chinese privet from riparian forests in the southeastern United States greatly improved forest habitats for butterflies and evidence suggests that butterfly communities in other temperate forests could benefit from removal of extensive shrub layers dominated by a single species. 相似文献
978.
以中国古典园林的分类为基点,分析古典园林的特点,总结了中国古典园林的设计手法,提出将其造园手法运用于现代园林的方法和措施,为我国现代园林设计提供一定的理论帮助和参考依据. 相似文献
979.
中国唐代以来的多数本草著作,均认定《神农本草经》中的彼子和《名医别录》中的榧实,与《唐本草》中的榧子为同物。现代中药学论著考订其原植物为今红豆杉科榧树(榧子)Torreya grandis Fort.ex Lindl.。殊误。经全面考证后确认,彼子是今三尖杉科三尖杉属Cephalotaxus Sieb.et Zucc.植物,榧实是红豆杉科红豆杉属Taxus L.植物,后世本草中的榧子与它们并非同物。 相似文献
980.
荸荠秆枯菌(CylindrosporiumeleocharidisLentz)生长发育温度8~35℃,最适于菌丝体生长、产孢的温度为25~30℃,20~28℃孢子萌芽率较高。致死温度46℃10min。病菌在RH75%以上生长良好,其产孢量则随湿度升高而增加。RH81%以上孢子可以发芽,饱和湿度再加水滴时发芽率最高。PH4.50~9.13均较适于病菌生长,产孢量则以在PH6.94~9.13时较多,PH4.20~7.60较适宜孢子发芽。连续黑光灯照射有促进孢子形成和菌丝体旺盛生长的作用。此菌对多种单糖、双糖和多糖都能利用,以蜜二糖、麦芽糖、葡萄糖等产孢量较多。适于病菌生长和产孢的氮源是甘氨酸、DL-α-氨基丙酸和氨基乙酸,脲素较差。 相似文献