全文获取类型
收费全文 | 23028篇 |
免费 | 1061篇 |
国内免费 | 2674篇 |
专业分类
林业 | 2843篇 |
农学 | 3491篇 |
基础科学 | 1902篇 |
4109篇 | |
综合类 | 6548篇 |
农作物 | 1310篇 |
水产渔业 | 871篇 |
畜牧兽医 | 3282篇 |
园艺 | 708篇 |
植物保护 | 1699篇 |
出版年
2024年 | 47篇 |
2023年 | 211篇 |
2022年 | 525篇 |
2021年 | 863篇 |
2020年 | 787篇 |
2019年 | 754篇 |
2018年 | 540篇 |
2017年 | 766篇 |
2016年 | 749篇 |
2015年 | 1003篇 |
2014年 | 918篇 |
2013年 | 1167篇 |
2012年 | 1389篇 |
2011年 | 1440篇 |
2010年 | 1423篇 |
2009年 | 1343篇 |
2008年 | 1254篇 |
2007年 | 1384篇 |
2006年 | 1286篇 |
2005年 | 1098篇 |
2004年 | 537篇 |
2003年 | 494篇 |
2002年 | 407篇 |
2001年 | 434篇 |
2000年 | 545篇 |
1999年 | 688篇 |
1998年 | 615篇 |
1997年 | 532篇 |
1996年 | 518篇 |
1995年 | 508篇 |
1994年 | 465篇 |
1993年 | 414篇 |
1992年 | 388篇 |
1991年 | 302篇 |
1990年 | 249篇 |
1989年 | 208篇 |
1988年 | 164篇 |
1987年 | 91篇 |
1986年 | 63篇 |
1985年 | 32篇 |
1984年 | 16篇 |
1983年 | 34篇 |
1982年 | 18篇 |
1981年 | 23篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1974年 | 9篇 |
1965年 | 6篇 |
1964年 | 6篇 |
1963年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
不同的干燥工艺对荷花蜂花粉功能成分的影响 总被引:1,自引:0,他引:1
探讨了5种干燥工艺对荷花蜂花粉功能成分的影响。微波干燥的干燥效率最高,60%火力处理540s可使水分从31.41%降到6.42%;干燥方式对荷花蜂花粉蛋白质影响较小;微波干燥后总黄酮提取率最高,为13.20mg/g;真空冷冻干燥后维生素C和过氧化氢酶含量最高,分别为48.89mg/100g和29.86mg/g·min。总的来说,真空冷冻干燥对荷花蜂花粉的功能成分影响最小;常压恒温干燥对功能成分影响较小、工艺简单、对设备要求低,宜于大规模应用于实际生产中。 相似文献
94.
Jiang YN Wu CY Huang CY Chu HP Ke MW Kung MS Li KY Wang CH Li SH Wang Y Ju YT 《Journal of animal science》2008,86(10):2461-2470
The Lanyu pig is an indigenous breed from the Lanyu Islet, which is southeast of Taiwan. Two herds of Lanyu pigs were introduced from the Lanyu Islet into Taiwan in 1975 and 1980. The current population of conserved Lanyu pigs consists of only 44 animals with unknown genetic lineage. The Lanyu pig possesses a distinct maternal genetic lineage remote from Asian and European pigs. The present study aimed to understand the phylogenetic relationship among conserved Lanyu, Asian, and European type pigs based on the cytochrome b coding gene, to ascertain the maternal lineage and genetic diversity within the conserved Lanyu pigs, and to address whether genetic introgression from exotic or Formosan wild pigs had occurred in the conserved Lanyu pigs. Entire mitochondrial genomes of both types of Lanyu pig comprised 2 ribosomal RNA, 22 transfer RNA, and 13 protein-coding genes. Only 2 haplotypes of the mitochondrial DNA (mtDNA) control region and cytochrome b were identified in the conserved Lanyu pig herds. When maximum likelihood trees were constructed, the Type I Lanyu mitochondrial genes formed a unique clade with a large pairwise distance of both cytochrome b and the control region from Asian and European type breeds, Formosan wild pigs, and exotic breeds. Significant loss of genetic diversity of mtDNA within the conserved Lanyu pigs was demonstrated by low haplotype and nucleotide diversities, supported by Fu and Li's D* neutrality test (1.44055; P < 0.05). The mtDNA control region sequences of extant pigs in the Lanyu Islet, however, showed high haplotype and nucleotide diversity, and clustered with exotic pigs. These results indicate no maternal lineage mtD-NA gene introgression from Formosan wild pigs and introduced exotic pigs to conserved Type I Lanyu pigs, and a severe loss of heterozygosity of mtDNA in conserved Lanyu pigs. The remaining extant pigs on the Lanyu Islet have been introgressed with exotic breeds. Strategies for future conservation of native Lanyu pigs are now even more urgent and important. 相似文献
95.
文章从山羊养殖历史、生物学特性、自然社会、经济效益、生态环保、市场消费及国外养殖进展等方面进行研究,认为我国南方农区山羊饲养应回归放牧养羊,可以实现社会生态经济的可持续发展。同时提出放牧养殖的标准化建设思路。 相似文献
96.
为了观察黄芪注射液对正常犬和二尖瓣关闭不全病理模型 (MR)犬的变时作用 ,并探讨其机制 ,在异氟烷吸入麻醉下 ,对正常及外科方法制作的犬亚急性二尖瓣关闭不全模型 (术后 5 0天后 )一次性静脉推注含生药 2 g/ m L的黄芪注射液 1 .2 5 m L/ kg,通过体表心电图测定心率和 PQ、QRS、RR、QT,并计算 QTC(QT/ RR)间期。在正常犬 ,开始注射黄芪注射液后 ,心率出现先减少后恢复再持续减少和显著变化。 MR模型犬开始注射液后 ,心率出现先升高后恢复再持续升高的显著变化。 MR模型犬的心率减慢变化与 RR、PQ、QT、QTc呈高度显著负相关 (P<0 .0 1 )。表明黄芪注射液对正常比格犬 ,具有加快心率的正性变时作用。对二尖瓣闭锁不全 (MR)模型犬具有减缓心率的负性变时作用。黄芪注射液的变时作用似与机体的机能状态有关 ,呈现双向调节作用。 相似文献
97.
Immune and bone properties of chicks consuming corn contaminated with a Fusarium that induces dyschondroplasia 总被引:1,自引:0,他引:1
A study was conducted to contrast the dyschondroplasia-inducing capability of several species of Fusarium with that of the natural fungi found in poultry diets and litter. Day-old broiler chicks were fed pure corn cultures of specific fungal isolates for 3 weeks. Humoral immunity to sheep red blood cells (SRBC), body weight, valgus and varus leg deformities, incidence of dyschondroplasia, and mechanical properties of the tibiotarsi were examined. F. equiseti #15 was the only fungal isolate to induce dyschondroplasia to any significant degree, which confirmed previous work in Minnesota. This isolate also suppressed growth rate and humoral immunity, although dyschondroplasia sometimes did occur without associated immunosuppression and growth depression. Bone strength of the tibiotarsal diaphysis was normal, and gross lesions of valgus and varus leg deformities did not appear to be related to the incidence of dyschondroplasia in the 3-week-old chicks. 相似文献
98.
99.
Zhang Q Li D Liu X Liu Z Cai X Wu G Qi S Yang S Yan X Shang Y He J Ma J Li J Ma W Han R Liu X Zhang J Xie Q Zhang Z 《Research in veterinary science》2008,85(2):368-371
This study was carried out to investigate the biological characteristics of the foot-and-mouth disease (FMD) virus strain Asia-1 China/2005, which is responsible for the 2005 epidemic in China. The result showed that this strain is not host restricted, and could not only cause FMD in cattle and sheep but also in pigs by either inoculation or direct contact. 相似文献
100.