全文获取类型
收费全文 | 77523篇 |
免费 | 32497篇 |
国内免费 | 23316篇 |
专业分类
林业 | 9402篇 |
农学 | 6561篇 |
基础科学 | 9434篇 |
35899篇 | |
综合类 | 36918篇 |
农作物 | 7122篇 |
水产渔业 | 6632篇 |
畜牧兽医 | 10590篇 |
园艺 | 3553篇 |
植物保护 | 7225篇 |
出版年
2024年 | 1871篇 |
2023年 | 1520篇 |
2022年 | 2133篇 |
2021年 | 2024篇 |
2020年 | 3582篇 |
2019年 | 6941篇 |
2018年 | 6462篇 |
2017年 | 7467篇 |
2016年 | 8116篇 |
2015年 | 8311篇 |
2014年 | 7195篇 |
2013年 | 7578篇 |
2012年 | 7632篇 |
2011年 | 6761篇 |
2010年 | 5646篇 |
2009年 | 5126篇 |
2008年 | 4329篇 |
2007年 | 4432篇 |
2006年 | 3913篇 |
2005年 | 3397篇 |
2004年 | 2978篇 |
2003年 | 2606篇 |
2002年 | 2341篇 |
2001年 | 1990篇 |
2000年 | 1735篇 |
1999年 | 1593篇 |
1998年 | 1440篇 |
1997年 | 1419篇 |
1996年 | 1268篇 |
1995年 | 1340篇 |
1994年 | 1272篇 |
1993年 | 1000篇 |
1992年 | 998篇 |
1991年 | 837篇 |
1990年 | 648篇 |
1989年 | 638篇 |
1988年 | 555篇 |
1987年 | 407篇 |
1986年 | 409篇 |
1985年 | 218篇 |
1984年 | 199篇 |
1983年 | 196篇 |
1982年 | 195篇 |
1981年 | 232篇 |
1980年 | 193篇 |
1979年 | 150篇 |
1978年 | 130篇 |
1975年 | 109篇 |
1965年 | 137篇 |
1964年 | 140篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
瘦素调控动物生殖活动的研究进展 总被引:4,自引:0,他引:4
瘦素是白色脂肪细胞分泌的一种分子量为16kDa的分泌型蛋白激素,具有调控动物机体能量代谢平衡和体重的生物学作用。此外,作为机体的能量代谢信号,瘦素对动物初情期的启动和正常发情周期的维持 、生殖器官和生殖腺的发育等生殖活动和生殖机能均起着非常重要的调节作用。由于它的受体存在于多种生殖器官上,瘦素可在生殖轴的不同水平对生殖活动予以调节。瘦素在正丘脑水平对于生殖活动的调节可能是其直接作用于GnRH神经元 相似文献
32.
J. Plendl M. Bahramsoltani O. Gemeinhardt H. Hünigen S. Käßmeyer P. Janczyk 《Anatomia, histologia, embryologia》2009,38(5):355-360
Teaching morphology, a fundamental part of medicine curricula is traditionally based on lectures and practical trainings. We introduced peer-assisted learning (PAL) and student expert teams to the courses to give the students the possibility to improve their free speech and self-confidence. We involved students in active preparation of online materials such as labelled e-slides and e-pics . We offered online digital microscopy (ZoomifyTM ) and dissection (CyberPrep) allowing repeating the learned material and studying veterinary morphology outside the dissection theatre. Over 60% of first and third semester students profited from being a peer or being taught by a peer and 50% said the expert teams were an excellent method to learn the topographic anatomy. Almost all students applied ZoomifyTM and CyberPrep and 75% of them found the digital microscopy and dissection to be a helpful or very helpful learning tool. In face of reduced contact hours, these forms of education compensated in part the lost teaching time. We observed improvement of rhetoric and presentation skills and self-confidence. The approaches should therefore find their constant place in the veterinary medicine curricula. 相似文献
33.
A computer program for calculation of doses and prices of injectable medications based on body weight or body surface area 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《Canadian journal of veterinary research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A computer program (CalcAnesth) was developed with Visual Basic for the purpose of calculating the doses and prices of injectable medications on the basis of body weight or body surface area. The drug names, concentrations, and prices are loaded from a drug database. This database is a simple text file, that the user can easily create or modify. The animal names and body weights can be loaded from a similar database. After typing the dose and the units into the user interface, the results will be automatically displayed. The program is able to open and save anesthetic protocols, and export or print the results. This CalcAnesth program can be useful in clinical veterinary anesthesiology and research. The rationale for dosing on the basis of body surface area is also discussed in this article. 相似文献
34.
根据所测定的白色力克斯兔(WR)、哈尔滨白兔(HW)及杂种一代(F_1,?WR×?HW)和回交一代[B_1,?WRX×?F_1,包括分离出的力克斯毛型(B_1R)和正常毛型(B_1N)]的5个血液蛋白多态系统——红细胞酯酶(Es—1、Es—2和Es—3)、前转铁蛋白(Prt)和后白蛋白(Po)的基因频率和基因型新率,比较了群体间的基因分布,估算了各群体内的平均杂合度和群体间的遗传距离,并运用类平均聚类法进行了聚类分析.结果表明,白色力克斯兔和哈尔滨白兔基因分布差异最大.亲缘关系最远;杂种一代和回交一代基因分布差异最小,亲缘关系最近;杂交一代和回交一代与白色力克斯兔亲缘关系较近,与哈尔滨白兔较远;回交一代中B_1N和B_1R间基因分布也存在一定差异.各群体平均杂合度大小为0.5223(HW)、0.4182[B_1,0.4846(B_1N)和0.3223(B_R)]、0.1105(F_1)和0.3946(WR).研究结果表明,利用蛋白多态性探讨家兔品种或品系间亲缘关系以及区分家兔品种或品系是可行的.此外,本文还结合各群体的变异性,对白色力克斯免和哈尔滨白兔的选育进行了探讨. 相似文献
35.
1993~ 1998年 ,我们在猪屠宰加工厂和一些饲养单位的检验和检疫中 ,发现猪有猪伪结核病变 ,并从有病变的脾脏和肠系膜淋巴结等器官分离到细菌 ,经东北农业大学鉴定属于耶新氏杆菌属中的伪结核耶新氏杆菌。所分离的菌株经抗原型鉴定属于 4个不同菌体抗原型。从 4个不同抗原型中 相似文献
36.
N. W. Holfeld B. Schiefer B. R. Boycott 《The Canadian veterinary journal. La revue veterinaire canadienne》1980,21(4):103-105
Nine cases of granulomatous dermatitis in carnivores (eight dogs, one cat) are described. In three cases, in which there were no fungi in hair shafts, nor any other evidence of mycotic infection initially, fungal elements were demonstrated in the granulomas with the aid of special stains (PAS and Grocott). Granulomatous dermatitis in case of dermatophyte infections is thought to be an hypersensitivity reaction and has been reported to occur in a variety of mammals. It is suggested that pyogranulomatous skin reactions and trichogranulomas could be associated with dermatophytes and it is recommended to carry out further laboratory studies in order to detect fungi in such cases. 相似文献
37.
38.
39.
Serological tests as indicators of immunity against Pasteurella multocida infection in sheep.
下载免费PDF全文
![点击此处可从《Canadian journal of veterinary research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Five serological tests, i.e. single tube agglutination, doubling dilution tube agglutination, agar agglutination, passive hemagglutination and passive mouse protection tests were evaluated for their efficacy in predicting the fate of vaccinated and unvaccinated sheep on challenge with an ovine strain of Pasteurella multocida. The passive hemagglutination test predicted the fate of unvaccinated sheep while the agar agglutination test indicated the immune status of vaccinated sheep. 相似文献
40.
I. R. Tizard N. A. Fish J. Harmeson 《The Canadian veterinary journal. La revue veterinaire canadienne》1979,20(5):143-144
Salmonella typhimurium was isolated from nine of 60 wild sparrows trapped in the Guelph area. While this organism was isolated from birds trapped at several different locations, the highest prevalence was in sparrows trapped in close proximity to an animal clinic. The significance of these findings in relation to human and animal salmonellosis is discussed. 相似文献