全文获取类型
收费全文 | 3757篇 |
免费 | 231篇 |
国内免费 | 170篇 |
专业分类
林业 | 662篇 |
农学 | 457篇 |
基础科学 | 18篇 |
284篇 | |
综合类 | 1433篇 |
农作物 | 264篇 |
水产渔业 | 1篇 |
畜牧兽医 | 90篇 |
园艺 | 312篇 |
植物保护 | 637篇 |
出版年
2024年 | 12篇 |
2023年 | 51篇 |
2022年 | 92篇 |
2021年 | 107篇 |
2020年 | 116篇 |
2019年 | 146篇 |
2018年 | 108篇 |
2017年 | 142篇 |
2016年 | 153篇 |
2015年 | 117篇 |
2014年 | 155篇 |
2013年 | 237篇 |
2012年 | 252篇 |
2011年 | 244篇 |
2010年 | 206篇 |
2009年 | 188篇 |
2008年 | 222篇 |
2007年 | 188篇 |
2006年 | 169篇 |
2005年 | 126篇 |
2004年 | 143篇 |
2003年 | 118篇 |
2002年 | 88篇 |
2001年 | 100篇 |
2000年 | 81篇 |
1999年 | 62篇 |
1998年 | 55篇 |
1997年 | 63篇 |
1996年 | 75篇 |
1995年 | 62篇 |
1994年 | 48篇 |
1993年 | 38篇 |
1992年 | 34篇 |
1991年 | 39篇 |
1990年 | 33篇 |
1989年 | 29篇 |
1988年 | 22篇 |
1987年 | 13篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1962年 | 1篇 |
1955年 | 6篇 |
排序方式: 共有4158条查询结果,搜索用时 15 毫秒
1.
2.
海拔梯度对台江方竹发笋节律的影响研究 总被引:1,自引:0,他引:1
通过原产地对合江方竹不同海拔梯度发笋节律的观察和研究,得出其开始发笋期、停止发笋期及发笋数都随着海拔梯度的变化有显著或极显著的差异,海拔越高,发笋越早,停止发笋期也越早,平均发笋量3300株/667m^2。其发笋期可以划分为开始期、高峰期和停止期阶段。在海拔l200In以L开始发笋期出现在9月中旬,停止生长期出现在10月上旬;1000m以一卜开始发笋期、停止生长期分别出现在9月下旬和10月底以后;随着海拔高度平均每降低100m,开始发笋期推迟2—3d,停止发笋期随着海拔高度平均每降低100m推迟3—4d。数学模型(以9月13日为第一天),发笋开始期为K=31.333-0.02383H海拔,停止发笋期为T=64.867-0.03217H海拔;合江方竹在不同海拔梯度的发笋性状可以划分成900m以下和900m以上两类,其中900m以下具有“笋期晚发笋多(晚多)”特性;900m以上具有“笋期早发笋少(早少)”特性。 相似文献
3.
4.
松材线虫病入侵陕西的风险分析 总被引:1,自引:0,他引:1
松材线虫病自1982年在我国发现后,扩散和危害呈逐年扩大和加重趋势,严重影响了我国生态安全和经济发展。本文通过对松材线虫病定量的风险分析,得出风险值R=2.775,表明松材线虫病对陕西省而言属于特别危险的林业有害生物,应加强监测、检疫和除治管理,防止传入陕西省并造成扩散危害。 相似文献
5.
6.
7.
采用专门设计的生物材料试验机测定了茶树新梢的折断力、断裂挠度和弹性模量等力学指标,初步探明了新梢节位(嫩度)、截面积、品种和空气温、湿度对这些指标的影响。结果表明折断式采摘机构能有效地实现选择性采茶,可克服切割式采茶机“一刀切”的弊端。此外,作者根据大量的测试数据,提出了折断式采摘器的基本工作参数。 相似文献
8.
Although agronomically interesting, selection of creeping-rootedness inlucerne, that is, the ability to form adventitious shoots on horizontal,spreading roots, remains difficult because of the complex and still unclear geneticcontrol of this character, coupled with the possible occurrence of external factorsthat affect unpredictably its expression. Two experiments were undertaken onprogenies of creeping-rooted plants, to verify previous findings and inferences,and test novel hypotheses, concerning the effect of various plant factors on theexpression of creeping-rootedness. The ultimate aim was to provide information onthe most appropriate germplasm, procedures, or indirect selection criteria, that wouldimprove the efficiency of breeding for this character. The factors here examinedincluded genotype, age, kind of progeny, vigour, spreading ability, and undergroundmorphology. Some genotypes appeared to be good donors of the character, whereasothers did not. The proportion of creeping-rooted plants increased in allcases with the plant age. Selfing consistently depressed the expression ofthe character compared with clonal propagation or crossing. It is suggestedthat the effect of age and selfing on the penetrance of creeping-rootedness ismediated through their effect on plant vigour. Both aerial and root vigour showedindeed an effect per se on the presence of the character. Beside thevigour, possible indirect selection criteria were identified in the frequenciesof swollen zones and latent stem primordia on horizontal roots. Proportion ofcreeping-rooted plants in progenies after one year of growth appeared as a simple anduseful criterion to predict future trends. Consistent with previous conclusions, theresults provided evidence that a combination of family and individualselection may enhance the character expression. 相似文献
9.
I. Bouwen D. Z. Maat 《European journal of plant pathology / European Foundation for Plant Pathology》1992,98(2):141-156
Two viruses, detected frequently in the Netherlands in pelargonium, were identified by serology and test plant reactions. Antisera were prepared and an ELISA procedure was developed to detect the viruses in pelargonium.One of the viruses, PFBV-N, proved to be pelargonium flower-break virus. With the antiserum to PFBV-N, it could be detected reliably throughout the year inPelargonium zonale Springtime Irene.The other virus, PLPV-N, was serologically closely related to pelargonium line pattern virus (PLPV) and to pelargonium ring pattern virus (PRPV), as were an old virus isolate from Saturnus, collected in the Netherlands in 1971 (L128), and PLPV isolates from Yugoslavia (PLPV-Y) and Denmark (PLPV-D). There were only minor differences in host-plant reactions between the virus isolates. Based on these tests, PLPV and PRPV are considered as isolates of the same virus, for which, for practical reasons, the name pelargonium line pattern virus is proposed.PLPV could be reliably detected by ELISA inP. zonale Springtime Irene and Amanda throughout the year with only a few exceptions. InPelargonium peltatum Tavira, however, reslts were erratic due to uneven distribution of virus in the plant. Best results were obtained when petioles of fully expanded leaves were tested. 相似文献
10.