全文获取类型
收费全文 | 8958篇 |
免费 | 588篇 |
国内免费 | 837篇 |
专业分类
林业 | 1200篇 |
农学 | 829篇 |
基础科学 | 416篇 |
885篇 | |
综合类 | 3818篇 |
农作物 | 479篇 |
水产渔业 | 495篇 |
畜牧兽医 | 1319篇 |
园艺 | 506篇 |
植物保护 | 436篇 |
出版年
2024年 | 68篇 |
2023年 | 170篇 |
2022年 | 241篇 |
2021年 | 361篇 |
2020年 | 319篇 |
2019年 | 392篇 |
2018年 | 217篇 |
2017年 | 361篇 |
2016年 | 463篇 |
2015年 | 359篇 |
2014年 | 474篇 |
2013年 | 584篇 |
2012年 | 712篇 |
2011年 | 708篇 |
2010年 | 534篇 |
2009年 | 597篇 |
2008年 | 453篇 |
2007年 | 456篇 |
2006年 | 438篇 |
2005年 | 381篇 |
2004年 | 281篇 |
2003年 | 244篇 |
2002年 | 228篇 |
2001年 | 193篇 |
2000年 | 190篇 |
1999年 | 134篇 |
1998年 | 120篇 |
1997年 | 92篇 |
1996年 | 88篇 |
1995年 | 69篇 |
1994年 | 76篇 |
1993年 | 72篇 |
1992年 | 58篇 |
1991年 | 61篇 |
1990年 | 51篇 |
1989年 | 46篇 |
1988年 | 32篇 |
1987年 | 16篇 |
1986年 | 13篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1978年 | 1篇 |
1962年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
991.
992.
993.
森林病虫害工程治理是一种新的病虫害管理方式,技术设计应严格按工程治理有关规定进行,要体现依靠科学技术和“预防为主,综合防治”的原则,明确治理目标、任务和效果,注意长、中、短期措施相结合,并将各项工程治理措施落实到各实施年度、小班。 相似文献
994.
自然老化和人工加速老化的杂交油菜种子经过水合—脱水处理以后,其活力和发芽率有显著捉高。主要表现在生理生化指标有明显改善,种子的电导率、糖分浸出量均比对照明显降低,脂肪酸活性显著降低.但脱氢酶活性有所提高.种子的类脂过氧化反应明显减轻。在水合—脱水处理中.以水分个衡—浸泡—脱水处理效果最佳。 相似文献
995.
Sixty-four mares (27 foaling, 37 barren or maiden), mainly Finnhorses, were subjected to treatment with 14.5 h of light and 9.5 h of darkness, starting at the beginning of December. The onset of cycling in non-foaling mares was estimated by weekly serum progesterone determinations. All of the non-foaling mares cycled in the middle of March. They started to cycle on average in the middle of February, 11.1 weeks after the beginning of the trial. There were statistically significant differences in relation to breed (Finnhorses started to cycle 2 weeks later than warm blooded, p less than 0.02) and in relation to age (brood mares with mean age 10 years, started to cycle 10 days later than those 3 years old, p less than 0.03). However, there was no statistical significant relation to previous lactation, although lactating mares lactating up to the previous autumn started to cycle 7 days later than dry mares (p less than 0.15). Artificial insemination of 14 mares in the 2nd oestrus of the year, in March, resulted in 12 foalings in the subsequent year (86%). The following winter, all pregnant mares (N = 27) were exposed to the same kind of light treatment, starting on 1st December. The 1st mare foaled at the end of January. The time from foaling to 1st post partum ovulation was significantly longer (17.0 days) in foalings taking place within 10 weeks from the beginning of the light treatment period, than in foalings occurring after more than 10 weeks of lighting (12.1 days) (p less than 0.01). 相似文献
996.
青蒿素及其衍生物抗寄生虫的研究进展 总被引:3,自引:0,他引:3
本文介绍了青蒿素及其衍生物的基本研究状况和它们抗寄生虫病的研究进展,青蒿素及其衍生物主要的抗寄生虫作用表现为抗疟原虫和抗血吸虫,它们抗弓形虫、卡氏肺孢子虫、犬附红细胞体和球虫的作用也较强,对其进一步的研制和开发具有广阔的前号: 相似文献
997.
998.
几种脱氮除磷污水处理工艺的比较 总被引:2,自引:0,他引:2
本文对几种常见的脱氮除磷污水处理工艺进行了分析和技术经济比较,以便人们在选择和设计污水处理工艺时作为借鉴。 相似文献
999.
Six experiments were carried out in two climatically different regions in south‐east Norway in order to compare different procedures for autumn management and use of regrowth in seed crops of timothy (Phleum pratense L.) cv. Grindstad. The experiments were laid out after seed harvest in mid‐August in crops with a stubble height of 5 cm (two experiments) or 12–15 cm (four experiments). Cutting to 5 cm on 15 September or 15 October, with or without an application of 50 kg N ha?1 immediately after seed harvest, and with or without an additional application of 30 kg N ha?1 after cutting, were compared with an uncut and unfertilized control treatment. As a main effect,autumn cutting increased seed yield in the subsequent year in only one experiment; this was laid out in a 13 cm stubble on a fertile soil near the coast. In the remaining five experiments seed yields were unaffected byautumn management regardless of climate or stubble height. Autumn cutting and N application increased the number of seedheads in two experiments, but this was offset by a drop in other seed yield components. On average for two cutting dates and for plots receiving an application of 50 kg N ha?1 after seed harvest, the dry matter (DM) was 1430 kg ha?1 on an inland site with 12–15 cm stubble, 1400 kg ha?1 on a coastal site with 5 cm stubble and 2460 kg ha?1 for two coastal sites with 12–15 cm stubble. Whereas forage yield and quality were fairly stable from the first to the second cut at the inland site, the yield of DM increased, but the crude protein and energy concentrations decreased from 15 September to 15 October at the coastal sites. It is concluded that the stubble and regrowth in seed crops of timothy cv. Grindstad can be harvested for forage without any effect on seed yield in the next year. 相似文献
1000.
兽用喹诺酮类药物发展动态 总被引:5,自引:2,他引:3
综述了兽用喹诺酮类药物—包括国内外已上市的、尚在开发中的以及人用药可转化为兽用药三个部分的品种,并对在我国尚未上市的兽用喹诺酮类药物的药理作用及用途作了简介。 相似文献