全文获取类型
收费全文 | 8404篇 |
免费 | 603篇 |
国内免费 | 550篇 |
专业分类
林业 | 914篇 |
农学 | 505篇 |
基础科学 | 163篇 |
568篇 | |
综合类 | 3224篇 |
农作物 | 497篇 |
水产渔业 | 426篇 |
畜牧兽医 | 1121篇 |
园艺 | 227篇 |
植物保护 | 1912篇 |
出版年
2024年 | 61篇 |
2023年 | 192篇 |
2022年 | 338篇 |
2021年 | 321篇 |
2020年 | 333篇 |
2019年 | 368篇 |
2018年 | 257篇 |
2017年 | 310篇 |
2016年 | 333篇 |
2015年 | 324篇 |
2014年 | 472篇 |
2013年 | 436篇 |
2012年 | 606篇 |
2011年 | 569篇 |
2010年 | 454篇 |
2009年 | 463篇 |
2008年 | 401篇 |
2007年 | 473篇 |
2006年 | 456篇 |
2005年 | 355篇 |
2004年 | 312篇 |
2003年 | 238篇 |
2002年 | 248篇 |
2001年 | 181篇 |
2000年 | 161篇 |
1999年 | 135篇 |
1998年 | 108篇 |
1997年 | 95篇 |
1996年 | 94篇 |
1995年 | 83篇 |
1994年 | 49篇 |
1993年 | 67篇 |
1992年 | 52篇 |
1991年 | 54篇 |
1990年 | 44篇 |
1989年 | 35篇 |
1988年 | 31篇 |
1987年 | 17篇 |
1986年 | 8篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1956年 | 1篇 |
1955年 | 3篇 |
排序方式: 共有9557条查询结果,搜索用时 0 毫秒
991.
992.
对采自呼和浩特市和包头市郊区黄萎病的5个菌株,通过茄茎柱、杏干培养基和30℃下生长的观察,确定呼、包郊区茄黄萎病菌均属大丽菊轮枝菌(Verticillium dahliae Kleb)。对其生物学特性研究证明:菌丝生长最低温度为5℃,适温范围为22.5~25.0℃,以22.5℃生长最适,最高生长温度为33℃。孢子萌发适温为25.0℃。菌丝在 pH4~9范围内均可生长,以 pH6生长最适。菌丝碳源营养中甘露醇、葡萄糖和可溶性淀粉生长最适。初侵来源试验表明:土壤、病残体中的微菌核、厚垣孢子和休眠菌丝体是呼、包两市茄黄萎病的初侵来源。种子不是初侵染来源。 相似文献
993.
B. Ehesten 《Acta veterinaria Scandinavica》1994,35(4):427
A-scan ultrasonography was performed in 40 healthy Samoyeds aged 2–5 years. Mydriasis and cycloplegia were induced in all dogs and 25 of the dogs were also sedated prior to the ultrasound examination. Five consecutive A-scans were taken on each eye and the intrasubject variance (measurement error) and true intersubject variance (true biological variation) were computed. The true biological variation was found to be of the same magnitude in both sedated and unsedated dogs, whereas the measurement errors were considerably larger in the group of unsedated dogs compared to the sedated ones. Magnitudes of the measurement errors for the anterior chamber depth and length of the vitreous body in the unsedated group were unacceptable. The sizes of the measurement errors in the sedated dogs were all within an acceptable range. 相似文献
994.
995.
Sudhir U. Meshram 《European journal of plant pathology / European Foundation for Plant Pathology》1984,90(3):127-132
Isolates ofAzotobacter chroococcum were found to be promising for the control of infestation of potato plants withRhizoctonia solani. Inoculation with an isolate ofVerticillium biguttatum in combination with isolates ofA. chroococcum effectively protected sprouts, stems and stolons against infestation withR. solani. The effect of inoculation varied with soil temperature.No sclerotia were formed on potatoes harvested from soil in pots inoculated with isolates ofA. chroococcum plusV. biguttatum under glasshouse conditions; the yield increased significantly over the control.Samenvatting Enkele isolaten vanAzotobacter chroococcum bleken sterk antagonistisch ten opzichte vanRhizoctonia solani en leken goed bruikbaar voor een biologische bestrijding van deze ziekteverwekker van de aardappel.Beënting van de grond metVerticillium biguttatum enA. chroococcum gaf — in potproeven — een effective bescherming van spruiten, stengels en stolonen tegen aantasting doorR. solani.De vorming van sclerotiën bleef achterwege op knollen die gevormd waren in grond die was beënt metA. chroococcum plusV. biguttatum. De opbrengst uit behandelde grond was hoger dan die uit onbehandelde.De effectiviteit van de behandeling is afhankelijk van de temperatuur. 相似文献
996.
The latent periods of Visna virus and of progressive pneumonia virus were demonstrated by one-cycle growth studies to end 14–16 hr after infection of sheep choroid plexus cell cultures. Maedi virus was demonstrated to have a 14–18-hr latent period. 相似文献
997.
冯惠琴 《山东农业大学学报(自然科学版)》1988,(4)
异形眼蕈蚊(Phyxia scabiei Hopk.)雌成虫无翅,头胸部不发达,腹部粗大,多爬行或跳跃,雄成虫具有一对翅。寄主复杂,以为害生姜等块茎,块根类蔬菜为主,自然条件下在原寄主田以幼虫越冬,菜窖内无越冬期。成虫不取食,有趋光性,幼虫行隐蔽式生活,常在寄主表皮下取食,易引起局部腐烂,抗逆力强,在4~35℃及腐烂的寄主条件下均能生存,各代历期随温度的升高而缩短。 相似文献
998.
De Clercq P Bonte M Van Speybroeck K Bolckmans K Deforce K 《Pest management science》2005,61(11):1129-1132
Due to growing criticism over the use of non-indigenous coccinellids, the two-spot ladybird, Adalia bipunctata (L.), has enjoyed increasing attention for aphid biocontrol in Europe. In the current study, eggs of the Mediterranean flour moth, Ephestia kuehniella Zeller, whether or not supplemented with bee pollen, were evaluated as a factitious food for larvae and adults of A. bipunctata. The predator showed slower larval development and lower survival when reared on live pea aphids, Acyrthosiphon pisum (Harris), than on E. kuehniella eggs. Survival on gamma-irradiated eggs of E. kuehniella was superior to that on frozen flour moth eggs, but other developmental characteristics were similar. Adults of A. bipunctata reared on Ac. pisum were only half as fecund as those offered irradiated or frozen E. kuehniella eggs, but egg hatch was markedly better on live aphids than on flour moth eggs (61 versus 20-27%, respectively). However, when a diet of flour moth eggs was supplemented with frozen moist bee pollen, egg hatch of A. bipunctata was equally as good as on live aphids. Supplementing flour moth eggs with dry pollen did not yield satisfactory results. Only 10% of larvae reached adulthood on moist bee pollen alone and resulting adults weighed less than half as much as those obtained on flour moth eggs. Our findings indicate that A. bipunctata is able to compensate for a suboptimal diet of animal prey by supplementary feeding on flower pollen. It is concluded that pollinivory may be a crucial trait for both the rearing of this natural enemy and its use in biological control programmes. 相似文献
999.
Simontacchi C Perez de Altamirano T Marinelli L Angeletti R Gabai G 《Veterinary research communications》2004,28(6):467-477
The aim of this work was to investigate the secretion of dehydroepiandrosterone (DHEA), testosterone (T), dihydrotestosterone (DHT) and oestradiol (E) as biological markers in response to illegal administration of testosterone, 19-nortestosterone (N) and oestradiol, either alone or in combination. Twenty male Friesian calves (age 13-14 months) were allotted to a control group (n = 5), and five experimental groups (n = 3) each. Each experimental animal was repeatedly injected with one of the following hormonal treatments: E, T, N, T+E and N+E. Circulating DHEA, T, DHT and E were determined by radioimmunoassay. The administration of T alone did not induce any variation in plasma DHEA, T, DHT and E, which were similar to those in the control group. In contrast, DHEA, T and DHT were on average significantly lower in the T+E and N-treated groups (p < 0.01), whereas the administration of N+E resulted in the reduction of plasma T and DHT without any modification of plasma DHEA. The administration of E alone or in combination increased circulating levels of E but did not affect androgen plasma profiles. The results indicate that plasma levels of T do not permit detection of illegal treatments because plasma androgens always remained within the physiological range. Illegal E treatment could be detected in blood samples when they were collected at least every 20 days. 相似文献
1000.