全文获取类型
收费全文 | 7024篇 |
免费 | 1853篇 |
国内免费 | 127篇 |
专业分类
林业 | 746篇 |
农学 | 694篇 |
基础科学 | 316篇 |
871篇 | |
综合类 | 3757篇 |
农作物 | 473篇 |
水产渔业 | 196篇 |
畜牧兽医 | 962篇 |
园艺 | 248篇 |
植物保护 | 741篇 |
出版年
2025年 | 118篇 |
2024年 | 207篇 |
2023年 | 211篇 |
2022年 | 261篇 |
2021年 | 292篇 |
2020年 | 291篇 |
2019年 | 368篇 |
2018年 | 222篇 |
2017年 | 332篇 |
2016年 | 361篇 |
2015年 | 341篇 |
2014年 | 478篇 |
2013年 | 424篇 |
2012年 | 605篇 |
2011年 | 512篇 |
2010年 | 453篇 |
2009年 | 435篇 |
2008年 | 362篇 |
2007年 | 407篇 |
2006年 | 291篇 |
2005年 | 248篇 |
2004年 | 185篇 |
2003年 | 221篇 |
2002年 | 149篇 |
2001年 | 155篇 |
2000年 | 138篇 |
1999年 | 99篇 |
1998年 | 116篇 |
1997年 | 109篇 |
1996年 | 101篇 |
1995年 | 107篇 |
1994年 | 70篇 |
1993年 | 63篇 |
1992年 | 50篇 |
1991年 | 48篇 |
1990年 | 45篇 |
1989年 | 50篇 |
1988年 | 26篇 |
1987年 | 24篇 |
1986年 | 8篇 |
1985年 | 4篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 6篇 |
1956年 | 1篇 |
排序方式: 共有9004条查询结果,搜索用时 15 毫秒
41.
指出了检测仪器设备在检定/校准期间内必须进行期间核查,以确保检测仪器设备处于良好的正常状态,从而保证检测数据的准确可靠.依据JJG 694-2009《原子吸收分光光度计检定规程》,对单位实验室在用的火焰石墨炉一体化原子吸收分光光度计进行了期间核查.核查内容包括测量线性R,检出限,测量重复性,线性误差和准确性,各项核查结... 相似文献
42.
介绍由可编程控制器PLC控制的跳汰机风阀控制系统,详细叙述了风阀自动控制的思想,以及各种跳汰参数的调整方法。 相似文献
43.
Chromosomal location of a gene (Rkn-mnl) for resistance to the root-knot nematode transferred into wheat from Aegilops variabilis 总被引:1,自引:0,他引:1
Root-knot nematode is a significant root-parasite of common wheat. A dominant gene Rkn-mnl for resistance was transferred into wheat from Acgilops variabilis. This gene was shown to be on chromosome 3B. Further analysis indicated that it is on the long arm of this chromosome and independent of the centromere. 相似文献
44.
青杨叶锈病是土默特地区杨树发生的一种重要病害。病原为落叶松-杨栅锈菌。该病菌[0][Ⅰ]阶段专主寄生在落叶松上,[Ⅱ][Ⅲ]阶段寄生在青杨上。该病在土默特地区8~9月开始发病,病害发生比较严重,幼林发病较成林早、重;林内发病较林外重。 相似文献
45.
缀叶丛螟危害南酸枣的发生规律及防治措施 总被引:1,自引:0,他引:1
对缀叶丛螟的形态特征、生活史、生活习性进行观察,并采取室内及林间防治这2种试验方法研究防治措施。结果表明:室内试验选用10%天王星1000倍、90%杀虫单1000倍、20%杀灭菊酯1000倍液效果较好;林间防治应在第1代、第2代幼虫盛发期选用20%杀灭菊酯2000倍、10%天王星2000倍、90%杀虫单1000倍,对3~4龄幼虫进行防治,效果达91%以上,可在大面积爆发时防治应用. 相似文献
46.
Valéria Carpentieri-Pípolo Leones Alves de Almeida Romeu Afonso de Souza Kiihl Ciro Antonio Rosolem 《Euphytica》2000,112(2):203-209
The long juvenile period characteristic (LJP), which delays flowering under short day conditions, has been identified in soybean
cultivars (Glycine max L. Merrill). This characteristic may be especially important as it increases the range of adaptation of soybean in low latitudes
and gives greater flexibility for sowing periods within the same latitude. The inheritance of the long juvenile period was
studied in the BR80-6778 soybean line to provide knowledge to support the development of cultivars adapted to short day conditions.
Cultivars with classic flowering, Paraná, Bossier, Bragg and Davis, which flower early under short day conditions, were also
used as parents in single crosses. They were crossed among themselves and with the genotypes with LJP, BR80-6778 and MG/BR
22 (Garimpo). The study was carried out under short day conditions (early sowings) in greenhouses and in the field at Embrapa
National Soybean Research Center, Londrina, PR. Flowering was assessed daily. The results indicated that the BR89-6778 line
shares a pair of alleles with the Paraná cultivar, and when associated with the cc allele retards flowering under short day conditions. The following genotype constitutions were attributed to the cultivars:
Paraná (aaBBCC), Bossier (AabbCC), and BR80-6778 (aaBBcc). The combination of the genes aabb and aabbcc has a pronounced effect on the manifestation of the trait.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
47.
本文通过对9条分布均匀、相对较窄的不同疏透度(透光疏透度,下同)(0.13~0.33)的树木林带和不同疏透度(0.00~0.80)风障组合的野外风速观测,确定了树木林带和风障的最适疏透度分别为0.25和0.13。基于林带结构(疏透度)与风速降低的关系,确定了林带主带间距离的主要参数,即,林带结构系数(δ)和以主害风为代表的小气候参数(Lrp)。另外,通过对林带树木的野外调查,应用树木解析技术确定林带成林高(H0)。因此,树木林带的主带间距可以通过林带结构系数、希望降低风速的比例和树木生长模型来确定。本文以杨树林带为例,具体确定了杨树林带的主带间距。该研究结果不仅适于树木林带的设计,同时适于其它生物材料或人工风障的设计。图4表5参40。 相似文献
48.
49.
E. M. Van Hees-Boukema J. C. Zadoks 《European journal of plant pathology / European Foundation for Plant Pathology》1986,92(2):71-80
Urediospores ofPuccinia recondita f.sp.tritici were applied to wheat seedlings. Inoculated plants were placed in a growth chamber to expose the spores to dry periods from zero to nine days at near-optimal temperatures (ca 18 °C). The dry period was followed by a wet period varying from 2 to 24 hours for germination of spores and infection of plants. Infection results were subjected to analysis of variance. The main effects dry period, wet period, and temperature were highly significant. The dry period×wet period interaction was significant. The interaction implied that the effects of post-detachment, ripening of germinable spores appeared in their resulting infectivity. There were two forms of post-detachment ripening, a slow ripening during the dry period and a faster ripening during the wet period. The two forms of ripening showed a non-additive compensatory interaction. The effect of post-detachment ripening on infectivity of germinated spores was more pronounced at 15 than, at 18 or 20 °C; the effect was strongest during the first day of the dry period. At dry periods of over 6 days, infectivity of germinated spores decreased, especially at the higher temperatures. Prolonged exposure, of spores to a dry period apparently damages the spores even though they are still able to germinate.Samenvatting Uredosporen van de bruine roest van tarwe (Puccinia recondita f.sp.tritici) werden over het eerste blad van tarwekiemplanten verstoven. De aldus geïnoculeerde planten werden in een klimaatkamer geplaatst bij ca. 18 °C om de sporen bloot te stellen aan droge perioden van 0 tot 9 dagen. De droge perioden werden gevolgd door natte perioden van 2 tot 24 uur om de sporen te laten kiemen en de planten te infecteren. Na de natte periode werden de planten bij verschillende temperature geplaatst om de latente periode en de vorming van sporenhoopjes te bepalen. De hoofdeffecten op de vorming van sporenhoopjes waren zeer significant: duur van de droge periode, duur van de natte periode en temperatuur. Twee vormen van sporenrijping werden gevonden bij rijping vnn sporen, die los op het blad lagen (rijping, buiten de sporenhoopjes), een langzame rijping tijdens de droge periode en een snelle rijping tijdens de natte periode. Deze twee vormen van rijping vertoonden statistische interactie met enige wederzijdse compensatie. Het effect van deze sporenrijping (buiten de sporenhoopjes) op de infectiviteit van gekiemde sporen was bij 15 °C duidelijker dan bij 18 en 20 °C; het effect was het sterkst tijdens de eerste dag van de droge periode. Bij droge periodes langer dan 6 dagen daalde de infectiviteit, vooral bij de hogere temperaturen. 相似文献
50.
旱农区不同种植模式作物最佳补灌时期和适宜补灌量研究 总被引:17,自引:3,他引:17
The effect of supplementary
irrigation with catchment rainfall on crop yield increment and its water use efficiency
was studied on upland field with different cropping patterns to make full use of the
natural rainfall. The results showed that the crop yield and water use efficiency was
increased significantly after 45 mm~90 mm supplementary irrigation, as compared with no
irrigation. The optimum total amounts of supplementary irrigation for all three cropping
patterns were 90 mm. The optimum amounts and periods of irrigation for mono-cultured wheat
were 8mm before sowing and 82 mm at its boot stage, those for film-covered mono-cultured
were 90mm at its big horn stage, and those for multipled cropping wheat and film-covered
corn were 4mm before wheat sowing and 19 mm both at jointing and boot stages, and 24 mm
both at jointing and big horn stages of corn. The results were suitable for northern
upland fields. 相似文献