全文获取类型
收费全文 | 84470篇 |
免费 | 7088篇 |
国内免费 | 8355篇 |
专业分类
林业 | 9996篇 |
农学 | 12856篇 |
基础科学 | 7162篇 |
13998篇 | |
综合类 | 23438篇 |
农作物 | 4014篇 |
水产渔业 | 5139篇 |
畜牧兽医 | 14653篇 |
园艺 | 2702篇 |
植物保护 | 5955篇 |
出版年
2024年 | 101篇 |
2023年 | 679篇 |
2022年 | 1841篇 |
2021年 | 2914篇 |
2020年 | 3065篇 |
2019年 | 3422篇 |
2018年 | 2602篇 |
2017年 | 3438篇 |
2016年 | 3432篇 |
2015年 | 4204篇 |
2014年 | 4043篇 |
2013年 | 5120篇 |
2012年 | 5353篇 |
2011年 | 5951篇 |
2010年 | 5813篇 |
2009年 | 5162篇 |
2008年 | 4978篇 |
2007年 | 4831篇 |
2006年 | 4607篇 |
2005年 | 4062篇 |
2004年 | 2069篇 |
2003年 | 1799篇 |
2002年 | 1478篇 |
2001年 | 1615篇 |
2000年 | 1866篇 |
1999年 | 2008篇 |
1998年 | 1975篇 |
1997年 | 1650篇 |
1996年 | 1490篇 |
1995年 | 1423篇 |
1994年 | 1229篇 |
1993年 | 1179篇 |
1992年 | 993篇 |
1991年 | 815篇 |
1990年 | 699篇 |
1989年 | 600篇 |
1988年 | 459篇 |
1987年 | 274篇 |
1986年 | 175篇 |
1985年 | 85篇 |
1984年 | 75篇 |
1983年 | 69篇 |
1982年 | 54篇 |
1981年 | 41篇 |
1980年 | 31篇 |
1979年 | 21篇 |
1978年 | 15篇 |
1965年 | 12篇 |
1964年 | 14篇 |
1963年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
为尽快实现上海崇明奶牛布鲁氏菌病和牛结核病(以下简称"两病")区域净化示范区净化目标,通过建立奶牛场"两病"输入性风险评估和内部风险评估模型,结合奶牛场"两病"流行史,构建了上海市规模化奶牛场"两病"风险评估分级体系;应用该体系将奶牛场划分为高、中、低风险场,为实施分类管理策略奠定基础。运用该体系,对上海市崇明区奶牛场每年开展1次"两病"风险评估分级。经过连续3年的风险分级与管理,崇明区奶牛场的"两病"净化效率得到极大提高,并使崇明奶牛"两病"区域净化示范区顺利通过国家验收,表明该体系符合上海市奶牛"两病"净化工作实际。 相似文献
993.
为验证自行研制的A型流感病毒分型基因芯片方法在实际中的应用效果,了解A型流感病毒各亚型在我国不同地区和不同宿主中的分布情况,对我国20个地区、不同宿主源(鸡、鸭、鹌鹑、鸽子、猪、人等)拭子和组织样品共16 852份进行了检测。利用自行研制的A型流感病毒分型基因芯片方法,对样品进行RNA提取、多重不对称RT-PCR扩增、芯片杂交、洗涤和扫描分析;同时将基因芯片检测阳性的样品,用普通RT-PCR扩增后进行序列测定。结果显示:利用该方法检出阳性样品2 582份,总检出率为15.32%(2 582/16 852),共检测到H1N1、H2N9、H3N2、H4N6、H5N1、H7N1、H7N9、H9N2、H10N5、H16N3等10个亚型,且均与阳性样品测序结果一致。结果表明,该方法可准确检测不同地区、不同宿主中的A型流感病毒不同亚型。同时,该方法能在同一张芯片上准确鉴定A型流感病毒的多种亚型,解决了其他常规方法无法检测已发现和可能发生变异的所有亚型的棘手问题,从而为A型流感诊断和分子流行病学监测提供了一种新技术。 相似文献
994.
为了解国内外奶牛疫病预警技术及其应用现状,归纳了奶牛疾病的预警要求,分析了国内外8种疫病预警技术的发展现状及其在奶牛养殖中存在的局限性。一是兽医巡检预警技术:该技术较为成熟,但不能满足大规模养殖牛场迅速、高效预警的需求。二是奶样体细胞数测定技术:可初步诊断隐性乳腺炎,但需要额外细菌培养和检测确诊。三是奶牛群体改良测定技术:以监测生产性能为主,仅可预警奶牛乳腺炎及酮病。四是计步器及发情、反刍项圈预警技术:同时具备发情与反刍监测功能,但仅适用于牛群的发情与反刍监测。五是大数据挖掘技术:在数据库基础上,利用各种模型或算法预测传染病的发生和发展,但预警效率受限。六是智能化体温连续远程监测及预警技术:可预警口蹄疫等重大传染病,但无法完全替代临床诊断,不能监测病原微生物。七是基于AI和群体热成像的奶牛行为分析技术:可以监视记录奶牛行为与温度特征,锁定病畜,但对发病初期无异常行为的牛只无效。八是生物气溶胶激光光谱测量技术:通过检测病原微生物种类和浓度,达到预警疫病的目的,目前主要用于军方监测人类重大疫病。未来的奶牛疫病预警技术需要进一步相互结合、取长补短,充分利用大数据、物联网等新兴技术进行奶牛重大疫病预警诊断。本文为预警监测技术的本地化发展提供了参考。 相似文献
995.
996.
Caihua Kong Kena Liu Qin Wang Rong Fu Huaxin Si Shiyan Sui 《Reproduction in domestic animals》2021,56(11):1413-1424
Oxidative stress can induce apoptosis of granulosa cells and lead to follicular atresia, thereby reducing the number of pigs giving birth. The aim of this study was to investigate the protective effect of Periplaneta americana peptide (PAP) on the apoptosis of the granulosa cells of pig ovaries (PGCs) induced by hydrogen peroxide (H2O2) via FoxO1. PGCs were treated with H2O2 to establish a cell apoptosis model. Cell viability was measured using the cell counting kit-8 (CCK-8) assay, and cell apoptosis was detected using flow cytometry. The malondialdehyde (MDA) level and nitric oxide (NO) content were detected to reflect the oxidative stress. Western blotting, qRT-PCR and overexpression were undertaken to determine the expression of FoxO1 and caspase-3, and immunofluorescence was used to detect FoxO1 in the nucleus and cytoplasm. PGCs were treated with 100 μM H2O2 for 6 hr, which resulted in oxidative damage and apoptosis and an apoptosis rate for PGCs of 32.95%. Next, PGCs were treated with 400 μg/ml PAP for 24 hr to repair the apoptosis induced by H2O2. PAP improved cell viability in H2O2-stimulated PGCs, the increased MDA level and NO content caused by H2O2 stimulation were reversed and the apoptotic rate of PGCs was reduced. The qRT-PCR and Western blotting results indicated that PAP decreased the H2O2-induced apoptosis and the expression of FoxO1 and caspase-3 in PGCs. The effect of PAP was the same following FoxO1 overexpression. FoxO1 was expressed in the nucleus when stimulated by H2O2 or overexpression; however, it migrated to the cytoplasm following PAP treatment. PAP decreased the apoptosis of PGCs induced by H2O2 by regulating FoxO1 expression and nuclear translocation. 相似文献
997.
998.
999.
Seriphidium transiliense, or subshrub sagebrush, is one of the most important forage resources for livestock in many arid lands, but such resources have been threatened by overgrazing for a long time. A 2013 vegetation survey of an original sagebrush rangeland (2400?ha) in the Tianshan Mountains revealed that nearly half of the area once under sagebrush has been replaced by annual species. This is due to the continual and rapid increase in livestock numbers over the past 30?years. Three smaller sites with different grazing scenarios: no grazing (Site N), a decline (Site 1), and an increase (Site 2) in livestock numbers, were selected to monitor recent changes (from 2004 to 2013) in vegetation biomass and the degree of dominance by sagebrush. Supplanting happened at Site 2 but little occurred at Site 1. There were significant differences between Site 2 and Site 1 in standing biomass in Spring and Summer, but no significant differences in Summer between Site 1 and Site N. The supplanting of sagebrush marks the completion of a dynamic process – in which rainfall plays a crucial role – of damage to sagebrush from heavy grazing in drought years and its rehabilitation by light grazing in some good years. Plant biomass loss was greatest when the land was first subjected to heavy grazing. Sagebrush tends to exist as a sole-dominant species rather than a companion species in sagebrush communities. This suggests that sagebrush continued to survive in pockets where grazing pressure had declined. 相似文献
1000.
Seed yield is a major breeding target in tetraploid red clover. We investigated if marker‐assisted parentage analysis can identify progeny plants with two high seed‐yielding parents in tetraploid red clover and if this technique is more advantageous than traditional half‐sib selection. Parentage analysis was successfully performed on the progeny from the 10% highest seed‐yielding genotypes from a second‐cycle family selection trial: 16.0% of progeny were identified with a high seed‐yielding father. However, progeny plants with two high seed‐yielding parents did not produce more seeds than traditionally selected progeny (27.3 g vs. 30.7 g/plant, respectively). The 10% highest seed‐yielding genotypes displayed on average 2% self‐fertilization. Four genotypes were self‐fertile with individual selfing rates up to 20%. Our results discourage the use of marker‐assisted parentage analysis to improve seed yield in tetraploid red clover when the material has been preselected for seed yield. Breeders should be aware that intensive selection for seed yield in tetraploid red clover may inadvertently lead to selection for increased self‐fertility, which may increase inbreeding in the long term. 相似文献