全文获取类型
收费全文 | 45800篇 |
免费 | 1402篇 |
国内免费 | 3019篇 |
专业分类
林业 | 2051篇 |
农学 | 3280篇 |
基础科学 | 1640篇 |
2521篇 | |
综合类 | 19019篇 |
农作物 | 2277篇 |
水产渔业 | 1921篇 |
畜牧兽医 | 14016篇 |
园艺 | 2357篇 |
植物保护 | 1139篇 |
出版年
2024年 | 279篇 |
2023年 | 1195篇 |
2022年 | 1045篇 |
2021年 | 1219篇 |
2020年 | 1223篇 |
2019年 | 1516篇 |
2018年 | 768篇 |
2017年 | 1264篇 |
2016年 | 1548篇 |
2015年 | 1603篇 |
2014年 | 2097篇 |
2013年 | 2058篇 |
2012年 | 2937篇 |
2011年 | 2999篇 |
2010年 | 2741篇 |
2009年 | 2886篇 |
2008年 | 3001篇 |
2007年 | 2683篇 |
2006年 | 2420篇 |
2005年 | 2311篇 |
2004年 | 1627篇 |
2003年 | 1461篇 |
2002年 | 1150篇 |
2001年 | 1116篇 |
2000年 | 863篇 |
1999年 | 722篇 |
1998年 | 623篇 |
1997年 | 549篇 |
1996年 | 544篇 |
1995年 | 465篇 |
1994年 | 496篇 |
1993年 | 517篇 |
1992年 | 550篇 |
1991年 | 508篇 |
1990年 | 432篇 |
1989年 | 443篇 |
1988年 | 106篇 |
1987年 | 70篇 |
1986年 | 45篇 |
1985年 | 21篇 |
1984年 | 10篇 |
1983年 | 15篇 |
1982年 | 14篇 |
1981年 | 7篇 |
1980年 | 13篇 |
1965年 | 5篇 |
1958年 | 9篇 |
1957年 | 13篇 |
1955年 | 7篇 |
1953年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 453 毫秒
991.
德州驴是优秀的皮肉兼用驴,包括“三粉驴”和“乌头驴”两个品系,但是关于德州驴的研究较少。为了向驴产业提供可靠的德州驴生产性能数据,该研究以40头三粉驴和9头乌头驴为研究对象,系统研究了德州驴的体尺性状、屠宰性能、脏器系数及胸腰椎数等性状特点。结果表明,三粉驴的屠宰率为54.02%,净肉率为42.43%,净皮率为8.12%;乌头驴的屠宰率为53.71%,净肉率为40.32%,净皮率为9.41%。表明三粉驴更适合于向肉用驴品系进行培育,乌头驴更适合于向皮用驴品系进行培育。与乌头驴相比,三粉驴的肝脏系数较高,并且小肠、盲肠显著较长(P<0.01),说明三粉驴具有更加优良的消化及代谢能力,可能是其具有更优异产肉性能的原因之一。调查发现,德州驴群体内存在胸腰椎数的变异,胸椎数为17~19个,腰椎数为5~6个;胸椎数与腰椎数存在不同形式的组合,18胸椎5腰椎占比为73.47%,18胸椎6腰椎占比为12.24%,19胸椎5腰椎占比为2.04%,17胸椎6腰椎占比为12.24%。统计发现,多一个胸椎或者腰椎可使驴皮产量增加。该试验结果可为德州驴产业健康可持续发展提供重要理论支撑,为品种及新品系培育提供数据支持。 相似文献
992.
乳痈,现代兽医学叫做乳房炎,是由各种原因引起的乳腺的炎症,多具有单乳区或多乳区乳房硬、肿、热、痛,乳汁减少或停止,乳汁变性,体温升高,食欲不振等典型症状,失治或误治易引起乳房的脓肿,脓肿溃破后,则常经久不愈,严重的影响母畜及幼畜的生长发育。一、对乳痈病因病机的认识乳痈虽多外症,但是本病的发生与发展与母畜有机体、外界自然环境关系极为密切。因为畜体各个脏腑、器官与体表、腠理之间,通过经络的作用,互相联系成一个整体,脏腑之问的生理活动,彼此问互相凋节维持机体内在环境保持平衡。 相似文献
993.
通过山东晨鸣纸业5m剥皮鼓鼓壳的埋弧自动焊焊接实践,分析了冬季施工时大型厚壁筒体的焊接特点,并采取了相应的焊接工艺措施,取得了良好效果,为大型厚壁筒体的焊接积累了经验. 相似文献
994.
番茄果实中LeERF1、LeERF2基因的克隆及序列分析 总被引:3,自引:0,他引:3
乙烯反应元件结合蛋白属于植物特有的一个转录因子家族,这个家族保守的DNA结合域称为ERF结构域。根据对番茄(Lycopersicon esculentum)和其它植物物种中EREBP基因家族的同源性比较,在保守区(ERF区域)设计合成一对简并引物,通过RT-PCR扩增得到一个114bp的片段,用此片段作探针筛选番茄cDNA文库(粉红期),得到两个基因LeERF1和LeERF2。通过BLAST工具在GenBank中搜索表明,LeERF1和LeERF2基因属于EREBP家族,LeERF1与EREBP-4和DDTFR10/A在氨基酸水平上的序列相似性为35%,LeERF2与EREBP-3和p65在氨基酸水平上的序列相似性为46%,是新的基因。LeERF1和LeERF2的核酸序列在GenBank发表,登录号分别为AY077626和AY275554。 相似文献
995.
利用啤酒糟中的残糖和碳水化合物,适量补充氮源和菜籽粕,采用微生物固态发酵方法生产菌体蛋白饲料。试验结果表明:产品比发酵前粗蛋白提高10%以上,粗纤维降解率达10%以上,16种氨基酸总和占粗蛋白总量的比例达到了82%以上。试验证明啤酒糟为主要原料生产菌体蛋白饲料对有效利用啤酒糟资源和开发饲料蛋白具有重要的意义。 相似文献
996.
997.
Bactericidal/permeability-increasing protein (BPI) has a strong effect on sterilization (mainly for G- bacteria),neutralizing the activity of lipopolysaccharide (LPS) and enhancing the phagocytosis of mononuclear cells and neutrophils to pathogenic bacteria.The biological functions of BPI have been researched widely in recent years,which is known as "super antibiotic" and has been explored by many scholars as a candidate gene for resistance.This author summarized the research progress and application prospect of the BPI gene in the pig resistant breeding by introducing the structure,biological function of BPI gene and its relationship with the resistance,which was aimed to provide theoretical references and basis for the function research of pig BPI gene and its practical application in resistance breeding in future. 相似文献
998.
ZHANG Hai ZHOU Bi-jun YANG Zhong-cheng LIAO Mei WANG Kai-gong WEN Ming CHENG Zhen-tao WANG Wei FENG Xu-fang 《中国畜牧兽医》2016,43(11):2834-2843
In order to study and analyze L1 gene of bovine papillomavirus(BPV)in Guizhou province,the L1 gene of BPV-GZ01 strain was amplified,cloned and sequenced using bioinformatic softwares and methods,and the secondary structure,tertiary structure,B-cell preponderant epitope,conserved domains analysis, transmembrane domain and signal peptide of L1 gene were predicted.The results showed that the length of L1 gene was 1 494 bp,encoding 497 amino acids.The L1 gene of BPV-GZ01 strain shared an amino acid identities of 98.6%,99.4%,98.4%,94.4% and 91.3%,and a nucleotide identities of 99.1%,99.8%,99.4%,87.6% and 82.8% with those of BPV2,BPV2-SW01,BPV2-AKS01,BPV13 and BPV1 strains,respectively.The results of phylogenetic tree analysis indicated that there was a close relationship between BPV-GZ01 and BPV2-SW01 strains.The prediction of secondary structure of L1 protein indicated that the random coil,extended strand and alphahelix took a higher percentage.The L1 protein was supposed contain 6 potential antigen epitopes.And no transmembrane domains and no signal peptide were found.The tertiary structure of L1 protein was curved spiral structure.These results provided a theoretical basis for immunologic diagnosis and further research of nucleic acid vaccine of BPV. 相似文献
999.
GUO Yuan LIU Zong-zheng LIU Le MENG Fan-hua ZHANG Yan-ru ZHOU Huan-min LIU Chun-xia 《中国畜牧兽医》2016,43(11):3011-3018
In order to obtain the cloned sheep using bone marrow mesenchymal stem cells(BMSCs)as the donor cells,the BMSCs of sheep were chosen and reconstructed embryos were built to transfer.10 published microsatellite markers were chosen,and the DNA samples from clone sheep,donor cells and surrogate ewes were amplified,and the relationship of father-son(RCP)was analyzed using the Quantity One for genotyping.The results showed that the reconstructed embryos were successfully built for electric fusion using sheep BMSCs as nuclear donor,and making nuclear transplantation into enucleated mature oocytes of which the fusion rate was 80.62%.20 surrogate ewe were chosen to be implanted with the reconstructed embryos at morula stage by implant surgery,and 5 lambs were born and only 3 were survived.The genotype of cloned sheep was in line with the dornor cell and the RCP were more than 99.999%.In conclusion,the first clone sheep were obtained successfully by using BMSCs as a nuclear donor in this experiment. 相似文献
1000.
The experiment was conducted to discuss the difference of binding time of green fluorescent protein B.melitensis M5 (GFP-M5) and B.abortus S19 (GFP-S19) infecting the mouse macrophagocyte (RAW264.7),lysosome,endoplasmic reticulum and golgi body in the initial stage and compare the binding rate of GFP-M5,GFP-S19 with organelle in different timeline,respectively,by confocal laser scanning microscope (CLSM) and flow cytometry.The result showed that GFP-M5 and GFP-S19 were successfully constructed.The intracellular survival ability of Brucella M5,Brucella S19,GFP-M5 and GFP-S19 were not obvisouly affected after infecting RAW264.7.GFP-M5 and GFP-S19 could enter the macrophagocyte in 30 mins,and in 2 h the Brucella could reach lysosome,endoplasmic reticulum and golgi body.In addition,the binding time for two attenuated vaccine did not show differences in 1,2,3 and 4 h.The content of GFP+ cell produced by RAW264.7 infected by GFP-M5 and GFP-S19 did not show significant differences (P>0.05).Therefore,the two strains did not have significant differences in the invasion ability in the initial stage of infecting host cell. 相似文献