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   669篇
  免费   16篇
  国内免费   2篇
林业   65篇
农学   19篇
  58篇
综合类   41篇
农作物   26篇
水产渔业   59篇
畜牧兽医   369篇
园艺   6篇
植物保护   44篇
  2022年   9篇
  2021年   11篇
  2020年   7篇
  2019年   8篇
  2018年   9篇
  2017年   11篇
  2016年   15篇
  2015年   21篇
  2014年   15篇
  2013年   26篇
  2012年   34篇
  2011年   37篇
  2010年   23篇
  2009年   22篇
  2008年   45篇
  2007年   53篇
  2006年   34篇
  2005年   37篇
  2004年   23篇
  2003年   24篇
  2002年   23篇
  2001年   13篇
  2000年   16篇
  1999年   5篇
  1998年   12篇
  1997年   3篇
  1994年   3篇
  1992年   12篇
  1991年   9篇
  1990年   11篇
  1989年   14篇
  1988年   7篇
  1987年   13篇
  1986年   9篇
  1985年   7篇
  1984年   6篇
  1983年   2篇
  1982年   3篇
  1981年   4篇
  1980年   4篇
  1979年   8篇
  1978年   5篇
  1977年   3篇
  1976年   3篇
  1975年   2篇
  1973年   4篇
  1972年   2篇
  1971年   3篇
  1970年   2篇
  1967年   2篇
排序方式: 共有687条查询结果,搜索用时 0 毫秒
681.
Adenosine triphosphate (ATP)-sensitive potassium (K(ATP)) channels are activated by various metabolic stresses, including hypoxia. The substantia nigra pars reticulata (SNr), the area with the highest expression of K(ATP) channels in the brain, plays a pivotal role in the control of seizures. Mutant mice lacking the Kir6.2 subunit of K(ATP) channels [knockout (KO) mice] were susceptible to generalized seizures after brief hypoxia. In normal mice, SNr neuron activity was inactivated during hypoxia by the opening of the postsynaptic K(ATP) channels, whereas in KO mice, the activity of these neurons was enhanced. K(ATP) channels exert a depressant effect on SNr neuronal activity during hypoxia and may be involved in the nigral protection mechanism against generalized seizures.  相似文献   
682.
The objective of this study was to investigate the influence of fatty acid-free bovine serum albumin (BSA) or fetal calf serum (FCS) on the re-expansion of biopsied blastocysts and post-warm viability of subsequently vitrified embryos. Firstly, blastocysts produced in vitro were biopsied at Day 7 and cultured to allow repair in TCM199 with 0.3% BSA or 5% FCS for 24 h. The re-expansion rates and mean total numbers of cells of the re-expanded embryos after the repair culture with BSA were almost the same as that with FCS. Secondly, after biopsied embryos were similarly cultured for repair with BSA or FCS, re-expanded embryos were selected for vitrification. After warming and exposure to 0.5 M sucrose with 20% FCS in mPBS, the embryos were cultured in TCM199 with 5% FCS for 24 h. The re-expansion rate and mean total number of cells in re-expanded blastocysts in the BSA treatment group (97.4 +/- 2.9% and 106 +/- 42) was significantly higher than that in the FCS treatment group (51.6 +/- 9.1% and 61 +/- 38), respectively (P<0.05 and P<0.01). In conclusion, both FCS and BSA supplementation can be useful for repairing cultures of bovine biopsied blastocysts; but, compared with BSA supplementation, FCS supplementation during repair culture reduces the post-warm viability of biopsied and subsequently vitrified embryos.  相似文献   
683.
Measles virus (MeV) vaccine strain, AIK-C, is temperature sensitive (ts), which is thought to be associated with attenuation of virus pathogenicity. In this study, replication and antibody response were examined in cotton rats using viruses carrying different forms of the P gene, which is responsible for the ts phenotype of strain AIK-C and its parental Edmonston strain. When cotton rats were inoculated intranasally, ts viruses neither replicated in lungs, nor reproducibly generated an antibody response. When inoculated intramusculary (i.m.), however, ts strains raised an antibody titer in all animals. This response was not observed when ultraviolet-inactivated virus was used. ts virus, inoculated i.m., was recovered from cotton rat drainage lymph nodes. These results suggest that ts virus, inoculated i.m., could replicate in the cotton rat, presumably at the superficial lymph node, and induce an antibody response. Therefore, cotton rats can serve as a small-animal model for investigating immune responses to safer ts vaccine, as well as recombinant vaccine using AIK-C as a vector for protection against other infectious agents.  相似文献   
684.
685.
This article reports the concentration and composition of the isomers of cis-icosenoic acid (20:1) in the fatty acids of various species of Japanese marine animals. The main purpose of this study is to reveal the distribution of a positional isomer, cis-7-20:1 (c7-20:1), in marine animals. Because this isomer overlaps with the c9-20:1 isomer in gas chromatography (GC) on the commonly used polar capillary columns, less information is available on its occurrence and distribution. In this study, the monounsaturated fatty acids isolated by argentation thin-layer chromatography were analyzed by GC using a highly polar capillary column, SLB-IL111 (100 m long), with the highest polarity among the commercially available GC columns. A clear separation between the c7-20:1 and c9-20:1 isomers enabled the analysis of all the isomers of 20:1 present in marine animals. The results confirmed that the c7 isomer was a minor component in the 20:1 in the pelagic fish, which is rich in the c9 and/or c11 isomers as reported previously. In contrast, the c7 isomer was one of the major isomers in flatfish, shellfish, crabs, and brittle stars. In these samples, the c13 isomer also occurred at higher concentrations rather than the c9 isomer. Because such a specific pattern of the 20:1 positional isomers was generally observed in both benthic fish and its dietary animals, the c7 isomer in the benthic fish probably originated from its diet. These marine animals are used as food in Japan, and therefore the c7-20:1 isomer is consumed by humans.  相似文献   
686.
To understand the causes and to control harmful blooms of the giant Nomura??s jellyfish Nemopilema nomurai, it is essential to study the seed population (benthic polyps) and its environment. To locate the habitat of polyps, the first step is to find ephyrae shortly after detachment from polyps. We found five ephyrae of N. nomurai of 1?C2?mm diameter for the first time from plankton samples collected at two sites, one specimen in the northwestern East China Sea (32°12.3??N, 123°12??E) and the other four specimens in the Yellow Sea (34°05.8??N, 121°50.0??E), on 22 and 26 May 2011. From the developmental state and water temperature of ca. 16?°C at the sampling stations, the collected ephyrae were estimated to have detached from polyps in early May of the year. Considering the increase of water temperature which induces strobilation and the direction of transport in the northwestern East China Sea and in the Yellow Sea, the locality of the seed polyps of the present specimens is probably the sea-floor close to the Changjiang River mouth and along the coast of Jiangsu Province.  相似文献   
687.
Tula virus (TULV) and Puumala virus (PUUV) are hantaviruses carried by the bank vole (Myodes glareolus) and European common vole (Microtus arvalis), respectively. PUUV is a causative agent of hemorrhagic fever with renal syndrome (HFRS), while TULV is thought to be apathogenic to humans. The N-terminal regions of the N proteins from TULV and PUUV were expressed and applied as enzyme-linked immunosorbent assay (ELISA) antigens. Colonized Japanese grass voles (Microtus montebelli) and BALB/c mice were used for experimental inoculation of the vole-borne hantaviruses TULV and PUUV. Voles and mice showed significant antibody production toward both viruses, but these antisera showed little cross-reactivity between TULV and PUUV in the immunofluorescence antibody assay and ELISA. In contrast, sera from patients with HFRS caused by PUUV exhibited high cross-reactivity against the TULV antigen, and sera from a natural rodent reservoir showed moderate cross-reactivity against the heterologous antigen, indicating that the antigenic cross-reactivity between TULV and PUUV differs in sera from rodents and humans.  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