全文获取类型
收费全文 | 7015篇 |
免费 | 329篇 |
国内免费 | 836篇 |
专业分类
林业 | 917篇 |
农学 | 1147篇 |
基础科学 | 538篇 |
1234篇 | |
综合类 | 1967篇 |
农作物 | 420篇 |
水产渔业 | 330篇 |
畜牧兽医 | 872篇 |
园艺 | 237篇 |
植物保护 | 518篇 |
出版年
2024年 | 17篇 |
2023年 | 45篇 |
2022年 | 190篇 |
2021年 | 277篇 |
2020年 | 258篇 |
2019年 | 267篇 |
2018年 | 187篇 |
2017年 | 246篇 |
2016年 | 218篇 |
2015年 | 300篇 |
2014年 | 277篇 |
2013年 | 353篇 |
2012年 | 426篇 |
2011年 | 443篇 |
2010年 | 425篇 |
2009年 | 422篇 |
2008年 | 371篇 |
2007年 | 368篇 |
2006年 | 421篇 |
2005年 | 414篇 |
2004年 | 204篇 |
2003年 | 150篇 |
2002年 | 117篇 |
2001年 | 133篇 |
2000年 | 159篇 |
1999年 | 214篇 |
1998年 | 168篇 |
1997年 | 154篇 |
1996年 | 129篇 |
1995年 | 116篇 |
1994年 | 106篇 |
1993年 | 106篇 |
1992年 | 104篇 |
1991年 | 70篇 |
1990年 | 79篇 |
1989年 | 75篇 |
1988年 | 54篇 |
1987年 | 38篇 |
1986年 | 24篇 |
1985年 | 16篇 |
1984年 | 10篇 |
1983年 | 5篇 |
1982年 | 12篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 2篇 |
排序方式: 共有8180条查询结果,搜索用时 15 毫秒
21.
22.
Relationship between oocyte maturation and fertilization on zygotic diversity in swine 总被引:1,自引:0,他引:1
Two experiments were conducted to examine how oocyte maturation and fertilization influence zygotic diversity in swine. In the first experiment, the distribution of oocyte maturation was compared to that of zygotic development. Oocytes were aspirated from follicles of 31 gilts and classified into stages of meiosis. Zygotes were flushed from oviducts of 19 additional gilts and classified into stages of meiosis and fertilization. The second experiment examined whether the time from ovulation to fertilization was constant among all oocytes. To test this premise, four to six oocytes from follicles of 10 mated gilts were aspirated just before or during ovulation, stained and transferred back into the oviducts of these same gilts. Zygotes were recovered 10 h later to determine whether the first oocytes ovulated were the more developed zygotes and, conversely, whether the last oocytes to be ovulated represented the lesser developed contemporaries. The skewed (P less than .05) distribution of oocyte maturation was similar to that of zygotic development. Regression of the frequency distribution describing early oocyte maturation resulted in a line with a slope (.59) that was similar to the slope (.58) of the regressed distribution of zygotic development. Likewise, the order of ovulation and order of subsequent stages of zygotic development were similar. These data suggest that variation in zygotic development in swine was due to variability in oogenesis; the time from ovulation to fertilization appeared to be constant. 相似文献
23.
通过日光温室试验,研究磁化水灌溉对番茄幼苗期和开花期生长性状与生理特性的影响,为磁化水灌溉在蔬菜生产中的应用提供依据。试验设置2个处理:磁化水灌溉、普通水灌溉(CK)。试验结果表明:与普通水灌溉相比,磁化水灌溉处理的番茄植株株高增长15%、茎粗增长8.2%;磁化水灌溉处理后的幼苗期番茄叶片SOD、POD和CAT活性分别增长22%、44.4%、18.4%,开花期番茄叶片SOD、POD、CAT活性分别增长15.8%、21.5%、48.3%;磁化水灌溉处理后的开花期番茄根系活力增长56%。磁化水灌溉能有效提升番茄生长性能、酶活性和根系活力,可为绿色、无公害蔬菜生产技术的应用提供参考。 相似文献
24.
25.
26.
建设动物隔离场所是根据《中华人民共和国动物防疫法》及相关法律法规和政策要求,为预防和控制外埠动物疫病传入,构建动物及动物产品无疫安全控制技术保障平台,加速构建和谐都市的必然选择。本文从必要性、功能定位、建设方案、运行模式和注意事项等方面论述首都动物隔离场所的建设思路。 相似文献
27.
交播技术在园林草坪养护中的应用研究 总被引:9,自引:6,他引:9
在过渡气候带的园林绿地,进行了暖季型草坪秋季交播多年生黑麦草籽的应用试验,结果表明:交播技术可用于马尼拉、狗牙根和矮生百慕大等暖季型草坪上,交播时间宜在10月底前进行,交播种子用量多年生黑麦草以20-30g/m^2为宜。 相似文献
28.
Yu-Xiong Lai Bao-Lei Jin Yu Xu Li-jie Huang Run-Qing Huang Yong Zhang Jimmy Kwang Jian-Guo He Jun-Feng Xie 《Veterinary immunology and immunopathology》2014,157(1-2):87-96
Betanodaviruses are the causative agents of viral nervous necrosis (VNN), a serious disease of cultured marine fish worldwide. Virus-like particles (VLPs) are one of the good novel vaccine candidates to control this disease. Until now, betanodavirus vaccine studies mainly focused on the humoral immune response and mortality after virus challenge. However, little is known about the activation of genes responsible for cellular and innate immunity by vaccines. In the present study, VLPs of orange-spotted grouper nervous necrosis virus (OGNNV) were produced in prokaryotes and their ability to enter Asian sea bass cells was the same as native virus, suggesting that they possess a similar structure to OGNNV. VLPs immunogenicity was then determined by intramuscularly vaccinating Epinephelus coioides at different concentrations (1.5 or 15 μg g?1 fish body weight, FBW) and immunizing frequencies (administration once, twice and thrice). A single vaccination with the dosage of 1.5 μg g?1 FBW is enough to provoke high titer antibodies (average 3 fold higher than that of negative control) with strong neutralizing antibody titer as early as 1 week post immunization. Furthermore, quantitative PCR analysis revealed that eleven genes associated with humoral, cellular and innate immunities were up-regulated in the liver, spleen and head kidney at 12 h post immunization, correlating with the early antibody response. In conclusion, we demonstrated that VLP vaccination induced humoral immune responses and activated genes associated with cellular and innate immunity against betanodavirus infection in orange-spotted grouper. 相似文献
29.
台湾控制禽流感的措施主要有3个方面,第一,对鸡、鸭、鹅以及候鸟进行禽流感主动和被动的监测,这个工作有6个单位参与,4所大学和2个研究所,即台湾动物健康研究所、台湾动物科技研究所、台湾大学、嘉义大学、中兴大学、屏东大学;第二、注重交流,官员、禽流感专家以及养殖户经常通过会议或讲座进行交流;第三,加强生物安全或扑杀,台湾野鸟协会每年都要采集2 000~3 000个粪便样本来监测候鸟中禽流感病毒的存在情况. 相似文献
30.