首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   16241篇
  免费   854篇
  国内免费   1597篇
林业   1386篇
农学   1595篇
基础科学   878篇
  2129篇
综合类   6271篇
农作物   1119篇
水产渔业   738篇
畜牧兽医   2612篇
园艺   1048篇
植物保护   916篇
  2024年   105篇
  2023年   327篇
  2022年   681篇
  2021年   839篇
  2020年   672篇
  2019年   665篇
  2018年   493篇
  2017年   706篇
  2016年   588篇
  2015年   786篇
  2014年   797篇
  2013年   929篇
  2012年   1316篇
  2011年   1373篇
  2010年   1237篇
  2009年   1007篇
  2008年   1073篇
  2007年   1012篇
  2006年   877篇
  2005年   679篇
  2004年   397篇
  2003年   289篇
  2002年   319篇
  2001年   245篇
  2000年   222篇
  1999年   192篇
  1998年   131篇
  1997年   102篇
  1996年   108篇
  1995年   94篇
  1994年   72篇
  1993年   90篇
  1992年   60篇
  1991年   39篇
  1990年   38篇
  1989年   29篇
  1988年   25篇
  1987年   14篇
  1986年   10篇
  1984年   4篇
  1983年   5篇
  1981年   6篇
  1979年   4篇
  1978年   3篇
  1976年   3篇
  1971年   3篇
  1970年   3篇
  1962年   3篇
  1956年   4篇
  1955年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
采用聚丙烯酰胺凝胶垂直平板电泳法对19只蓝马鸡和15只藏马鸡血清淀粉酶和血清酯酶同工酶酶谱进行了研究。结果发现:(1)蓝马鸡和藏马鸡血清淀粉酶有AMY1,AMY2,AMY3三种同工酶,其中AMY1和AMY2存在多态性;(2)两种马鸡的血清酯酶均存在ES1,ES2和ES3三种同工酶;蓝马鸡的ES1同工酶存在显现酶活性的ES1A(36.8%)和不显现酶活性的ES10(63.2%)2种表型,而藏马鸡全部为ES10型。  相似文献   
32.
针对牙齿组织形态学研究的难点,选择适宜固定液,用EDTA-2Na进行脱钙,完成了牙齿组织石蜡切片的制作。通过确定染色程序及各种染料的最佳作用时间,分别利用Masson三色染色法、传统的苏木精和伊红(HE)染色法对牙齿组织切片进行了染色观察。染色结果表明,与HE染色法相比,Masson三色染色更能使牙齿的各主要成分以不同颜色显现出来,色彩对比鲜明,亮丽润眼,为牙齿组织生理及病理组织形态学研究奠定了基础。针对机体中硬组织的相似特性,该试验方法可以在骨骼、软骨等硬组织的形态学研究中参考、改进并推广使用。  相似文献   
33.
防御素是生物界广泛存在的一类具微生物抗性的低分子肽,由于其抗菌谱最广,具有很高的应用潜力。本文概述了鸡β-防御素的分子结构、抗菌活性、基因表达调控的研究进展,并展望了其在畜牧业中的应用前景。  相似文献   
34.
为评估湖南省某生猪批发市场猪群疫病的发生风险,找出可能的风险因素,便于提出针对性预防措施,采用自行设计的调查问卷,结合访谈和现场调查,对27户经营户进行了调查,并将调查结果和调运数据相结合进行了疫病传播风险定性评估。结果显示:该市场疫病传入的可能性"高",内部传播的可能性"中等",疫病传出的可能性"高"。生猪调运频次多、数量大,经纪人行为复杂,运输车辆清洗消毒不彻底是可能的风险因素。评估结果提示,应尽量减少经纪人行为影响,重点加强对运输车辆的清洗消毒。  相似文献   
35.
An 8-year-old Shih-tzu dog was presented with a 2-week history of cough and nasal discharge. Upon presentation, the dog had constant open-mouth breathing with stertor and blood-tinged mucopurulent nasal discharge. Oral examination revealed a missing right mandibular second premolar tooth and severe periodontal disease. Computed tomography showed a radiodense, retropharyngeal foreign body. The foreign body was removed using caudal rhinoscopy. The foreign body was the right mandibular second premolar covered by thick calculus.  相似文献   
36.
Newcastle disease virus (NDV) causes significant economic losses to the poultry industry in Southeast Asia. In the present study, 12 field isolates of NDV were recovered from dead village chickens in Vietnam between 2007 and 2012, and were characterized. All the field isolates were classified as velogenic. Based on the sequence analysis of the F variable region, two distinct genetic groups (Vietnam genetic groups G1 and G2) were recognized. Phylogenetic analysis revealed that all the 12 field isolates fell into the class II genotype VII cluster. Ten of the field isolates, classified as Vietnam genetic group G1, were closely related to VIIh viruses that had been isolated from Indonesia, Malaysia, and Cambodia since the mid-2000s, while the other two field isolates, of Vietnam genetic group G2, clustered with VIId viruses, which were predominantly circulating in China and Far East Asia. Our results indicate that genotype VII viruses, especially VIIh viruses, are predominantly responsible for the recent epizootic of the disease in Vietnam.  相似文献   
37.
The endometrium of sheep consists of plenty of raised intercaruncular areas (IC). In order to better understand aglandular areas called caruncular (C), and intensely glandular the endometrium involved mechanisms of implantation, we used LC-MS/MS technique to profile the proteome of ovine endometrial C areas and IC areas separately during the peri-implantation period, and then compared the proteomic profiles between these two areas. We successfully detected 1740 and 1813 proteins in C areas and IC areas respectively. By comparing the proteome of these two areas, we found 170 differentially expressed proteins (DEPs) (P 〈 0.05), functional bioinformatics analysis showed these DEPs were mainly involved in growth and remodeling of endometrial tissue, cell adhesion and protein transport, and so on Our study, for the first time, provided a proteomic reference for elucidating the differences between C and IC areas, as an integrated function unit respectively, during the peri-implantation period. The results could help us to better understand the implantation in the ewes. In addition, we established a relatively detailed protein database of ovine endometrium, which provide a unique reference for further studies.  相似文献   
38.
Avian rotaviruses were isolated from turkeys with enteritis using MA 104 cell line. MA 104 cells were suitable for primary isolation and propagation of avian rotaviruses. Trypsin appeared essential for the enhancement of infectivity and the occurrence of cytopathic effect (CPE). Serum neutralization (SN), electron microscopy (EM), and analysis of genomic RNA were done to identify and confirm the identity of rotaviruses. Electrophoretic migration patterns of genomic RNA from avian rotaviruses were examined, and they were compared with those from mammalian rotaviruses. The migration patterns differed between these groups.  相似文献   
39.
A 16-year-old, castrated, male English cocker spaniel dog was presented due to generalized alopecia. Routine clinical pathology, endocrine and abdominal ultrasonography results were consistent with a diagnosis of pituitary-dependent hyperadrenocorticism. The adenohypophyseal lesion was clearly visualized on both 3 T and 7 T magnetic resonance imaging (MRI) of the pituitary gland. Although biochemical and MRI findings were consistent with a functional pituitary microtumor, a pituitary lesion was not detected using 18F-fluorodeoxyglucose positron emission tomography (FDG-PET). This report firstly describes the application of high-resolution FDG-PET to a spontaneous pituitary microtumor in a dog.  相似文献   
40.
This study was conducted to determine whether serum adipokine concentrations differed between healthy dogs and dogs with diabetes mellitus (DM). To accomplish this, 19 dogs with newly diagnosed DM were compared to 20 otherwise healthy dogs. The serum concentrations of visfatin, leptin, IL-1β, IL-6, IL-18, and TNF-α were significantly higher in diabetic dogs than in healthy dogs, whereas the serum adiponectin concentrations were lower in diabetic dogs. However, there were no significant differences in the IL-10 and resistin levels between groups. The serum leptin concentrations in diabetic dogs with and without concurrent disorders differed significantly. Treatment with insulin induced a significant decrease in IL-6 in diabetic dogs without concurrent disorders. These results show that the clinical diabetic state of dogs could modulate the circulating visfatin and adiponectin concentrations directly, while upregulation of leptin was probably a result of concurrent disorders rather than an effect of persistent hyperglycemia as a result of DM.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号