全文获取类型
收费全文 | 7290篇 |
免费 | 396篇 |
国内免费 | 947篇 |
专业分类
林业 | 834篇 |
农学 | 991篇 |
基础科学 | 626篇 |
1109篇 | |
综合类 | 2615篇 |
农作物 | 405篇 |
水产渔业 | 304篇 |
畜牧兽医 | 1002篇 |
园艺 | 336篇 |
植物保护 | 411篇 |
出版年
2024年 | 50篇 |
2023年 | 153篇 |
2022年 | 373篇 |
2021年 | 422篇 |
2020年 | 431篇 |
2019年 | 415篇 |
2018年 | 248篇 |
2017年 | 390篇 |
2016年 | 305篇 |
2015年 | 447篇 |
2014年 | 408篇 |
2013年 | 434篇 |
2012年 | 532篇 |
2011年 | 508篇 |
2010年 | 480篇 |
2009年 | 395篇 |
2008年 | 363篇 |
2007年 | 312篇 |
2006年 | 322篇 |
2005年 | 263篇 |
2004年 | 133篇 |
2003年 | 121篇 |
2002年 | 101篇 |
2001年 | 109篇 |
2000年 | 127篇 |
1999年 | 116篇 |
1998年 | 109篇 |
1997年 | 82篇 |
1996年 | 68篇 |
1995年 | 79篇 |
1994年 | 61篇 |
1993年 | 61篇 |
1992年 | 44篇 |
1991年 | 44篇 |
1990年 | 29篇 |
1989年 | 21篇 |
1988年 | 24篇 |
1987年 | 8篇 |
1986年 | 11篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1962年 | 1篇 |
1956年 | 4篇 |
1955年 | 2篇 |
排序方式: 共有8633条查询结果,搜索用时 15 毫秒
991.
为建立微滴式数字PCR(droplet digital PCR,ddPCR)定量检测鸡毒支原体(Mycoplasma gallisepticum,MG)方法,以MG的mgpc基因序列为目的序列,在其保守区域内设计合成了1对特异性引物和1条探针,通过各反应条件优化,建立了检测MG的ddPCR方法,并测定了建立方法的特异性、敏感性以及重复性。结果显示:建立方法的最佳引物浓度为20 μmol/μL,探针浓度为10 μmol/μL,退火温度为55 ℃;该方法只检出MG,没有检出鸡滑液囊支原体、禽衣阿华支原体、禽流感病毒、鸡新城疫病毒、鸡传染性支气管炎病毒、鸡传染性喉气管炎病毒、禽脑脊髓炎病毒、禽偏肺炎病毒、禽呼肠孤病毒、鸡沙门氏菌和鸡大肠杆菌,且相互间没有交叉反应;本方法最低检测MG重组质粒标准品的检测限为3.9拷贝/μL。重组质粒标准品浓度在3.9~41 025拷贝/μL范围内,绘制的ddPCR绝对定量曲线与测得值呈良好的线性关系(R2 = 0.999);3次重复检测试验结果的变异系数均小于5%。对采集的60份病鸡喉拭子、气囊拭子及肺样品进行MG检测,结果ddPCR方法的阳性检出率(15.0%)高于荧光定量PCR方法(13.3%)。结果表明,本研究建立的ddPCR方法定量检测MG特异性强,灵敏度高,重复性好,为绝对定量检测MG提供了技术手段。 相似文献
992.
993.
大学生网络成瘾不仅影响学习,而且影响身心健康。学校、家庭和社会应通力协作,共同营造和谐的社会文化氛围。 相似文献
994.
病死畜禽无害化处理工作事关养殖业安全、公共卫生安全和生态环境安全。河南省2013年实施病死畜禽无害化集中处理体系建设以来,已建成病死畜禽无害化集中处理场100个,日均处理能力1350t,病死畜禽收集点1990个,在政策扶持、机制创新、资金支持、执法监督等方面积累了丰富经验,创设了病死猪无害化处理与保险勘查理赔相挂钩的联动机制——“河南模式”,但也存在体系规划不合理、建设标准不高、政策不完善等问题。本文结合实际,提出制定法律法规、完善扶持政策、加强科技研发、加强宣传引导等建议,以期为深入推进病死畜禽无害化集中处理体系建设提供借鉴。 相似文献
995.
选取货值金额计算有争议的兽药违法典型案例,对货值金额计算的价格及数量确定依据条例条款分析审议,提出货值金额按标价计算等价格确定方法、已售数量争议的界定方法等数值确定方案的建议,以期为兽药规范执法提供参考。 相似文献
996.
ZHOU Longfei MENG Ran YU Xing LIAO Yigui HUANG Zehua Lü Zhengang XU Binyuan YANG Guodong PENG Shaobing XU Le 《水稻科学》2023,30(3):247-260
Pre-harvest yield prediction of ratoon rice is critical for guiding crop interventions in precision agriculture.However,the unique agronomic practice(i.e.,varied stubble height treatment) in rice ratooning could lead to inconsistent rice phenology,which had a significant impact on yield prediction of ratoon rice.Multi-temporal unmanned aerial vehicle(UAV)-based remote sensing can likely monitor ratoon rice productivity and reflect maximum yield potential across growing seasons for improving the ... 相似文献
997.
为探究2,6-二叔丁基-4-甲基苯酚(2,6-di-tert-butyl-4-methylphenol,BHT)对苹果采后灰霉病的防效和防病机制,采用平板法和刺伤接种法测定了BHT对灰霉病菌Botrytis cinerea的抑制作用及果实内防御酶活性和丙二醛含量的影响。结果表明,0.1 mmol/L BHT对苹果灰霉病的防效最佳,处理苹果后间隔48~96 h接种灰霉病菌,其防效可达68.59%~73.55%,其次为0.2、1.0 mmol/L BHT处理,但防效均低于52.94%。0.1 mmol/L BHT处理对灰霉病菌菌丝生长和分生孢子萌发无显著抑制作用,但可显著增强果实内超氧化物歧化酶、过氧化物酶和过氧化氢酶的活性以及总抗氧化能力,其峰值是对照的1.82~5.28倍,且均显著高于单独接种灰霉病菌的处理。此外,单独接种灰霉病菌的苹果果实内丙二醛含量快速升高,最大增幅达251.49%,而BHT处理后丙二醛含量变幅较小,最大增幅仅为83.95%。表明BHT可通过增强苹果果实内防御酶活性水平和总抗氧化能力来降低丙二醛的积累,从而提高果实对灰霉病的抗性。 相似文献
998.
AIM: To investigate the role of cytokeratin 8 (CK8) on the change of intercellular permeability of intestinal epithelial cells induced by corticotropin-releasing factor (CRF). METHODS: The expression levels of CRF receptor 1 (CRFR1) and CRFR2 on human colon adenocarcinoma HT29 cell surface were determined by immunofluorescence staining. After treatment with 100 nmol/L CRF for 72 h, the translocation of FITC-labelled dextran was measured in a Transwell chamber. The structural changes of tight junctions were observed under transmission electron microscope. The expression levels of CK8, and tight junction proteins ZO-1 and occludin were determined by Western blot. The activity of protein kinase C (PKC) was detected by ELISA. Furthermore, the effects of CRF on intestinal epithelial permeability were examined in CK8-silencing HT29 cells, which were constructed by infection with sh-CK8 lentivirus. RESULTS: CRF treatment increased the permeability of FITC-labelled dextran (P<0.05), caused the opening of tight junctions, and induced increased fluorescence intensity of CK8. The expression levels of occludin and ZO-1 were down-regulated (P<0.05). PKC activity was decreased at 1 h after CRF treatment (P<0.05). CRF-induced increase in the permeability and down-regulation of occludin were not blocked by CK8 silencing. Nevertheless,CK8 silencing blocked the effects of CRF regarding the decrease in the expression levels of ZO-1 and the increase in PKC activity (P<0.05). CONCLUSION: CK8 may be involved in CRF-induced increase in intestinal epithelial permeability by inhibiting the activity of PKC, and there may be other signaling pathways involved. 相似文献
999.
Rapid detection of SNPs in candidate genes regulating the growth of orange‐spotted grouper,Epinephelus coioides (Hamilton, 1822), using semiconductor sequencing 下载免费PDF全文
Liang Guo Junhong Xia Sen Yang Mingming Li Xinghan Chen Haoran Lin Zining Meng 《Aquaculture Research》2017,48(2):494-504
Orange‐spotted grouper (Epinephelus coioides) is one of the most important marine food species in Southeast Asia and China and has been cultured for decades. In this study, we fully utilized the limited capacity of semiconductor sequencing, the high efficiency of long‐range PCR for target enrichment and a non‐indexed pooling strategy to screen single‐nucleotide polymorphisms (SNPs) in a breeding population of orange‐spotted grouper. Forty‐one genomic DNA fragments, with a total length of approximately 180 kb, including 22 candidate genes that control growth, and from a DNA pool of 20 heaviest and 22 lightest individuals of the sampled population were successfully sequenced using an Ion Torrent Personal Genome Machine. 3 503 466 clear reads were produced with a length of 192 ± 56 bp, 86.8% of which were mapped to the reference with an average coverage depth of 2567‐fold and physical coverage of 98.8%. Finally, 1623 high‐quality SNPs were adopted. Compared with Sanger sequencing of three random common regions, the sensitivity and specificity of our approach were 39.4% and 100.0% respectively. A mutation located at the third position of the previously labelled start codon of growth hormone receptor type 1 invalidated the start codon. Furthermore, comparison of the frequencies of genotypes and alleles of this site between the two extreme groups, prediction of signal peptide and identification of conservative mRNA sequences suggested that the functional start codon is likely located at the position of another downstream in‐frame ATG in the mutant. These detected SNP markers will provide important tools for the selective breeding of orange‐spotted grouper. 相似文献
1000.
对抗性番茄材料‘Hawaii 7996’分别接种强致病力青枯菌(RsH)和中等致病力青枯菌(RsM)后,利用双向电泳技术找到了两个差异表达蛋白质--谷胱甘肽S转移酶L3和Remorin 1蛋白。在利用携带八氢番茄红素脱氢酶基因PDS的TRV重组病毒载体通过叶片浸润法证明VIGS体系可行后,进一步利用该技术沉默上述两个蛋白质的对应基因GST-L3和Rem-1,并用半定量RT-PCR检测沉默效果。结果表明,分别沉默GST-L3和Rem-1的番茄植株抗性减弱,在接种中等致病力青枯菌(RsM)后青枯病发病率和病情指数都明显高于对照植株,说明基因GST-L3和Rem-1与番茄对青枯病的抗性相关。 相似文献