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   490篇
  免费   14篇
林业   33篇
农学   14篇
基础科学   1篇
  74篇
综合类   15篇
农作物   23篇
水产渔业   47篇
畜牧兽医   266篇
园艺   2篇
植物保护   29篇
  2023年   1篇
  2022年   11篇
  2021年   15篇
  2020年   5篇
  2019年   8篇
  2018年   6篇
  2017年   9篇
  2016年   15篇
  2015年   19篇
  2014年   28篇
  2013年   39篇
  2012年   38篇
  2011年   47篇
  2010年   13篇
  2009年   18篇
  2008年   29篇
  2007年   37篇
  2006年   19篇
  2005年   33篇
  2004年   26篇
  2003年   29篇
  2002年   31篇
  2001年   11篇
  2000年   2篇
  1999年   5篇
  1998年   3篇
  1997年   1篇
  1993年   2篇
  1992年   1篇
  1979年   1篇
  1971年   1篇
  1968年   1篇
排序方式: 共有504条查询结果,搜索用时 15 毫秒
101.
Innate immune responses are vital for pathogen defense but can result in septic shock when excessive. A key mediator of septic shock is tumor necrosis factor-α (TNFα), which is shed from the plasma membrane after cleavage by the TNFα convertase (TACE). We report that the rhomboid family member iRhom2 interacted with TACE and regulated TNFα shedding. iRhom2 was critical for TACE maturation and trafficking to the cell surface in hematopoietic cells. Gene-targeted iRhom2-deficient mice showed reduced serum TNFα in response to lipopolysaccharide (LPS) and could survive a lethal LPS dose. Furthermore, iRhom2-deficient mice failed to control the replication of Listeria monocytogenes. Our study has identified iRhom2 as a regulator of innate immunity that may be an important target for modulating sepsis and pathogen defense.  相似文献   
102.
Strigolactones are a class of bioactive natural metabolites produced by plant roots and released into the rhizosphere. They were discovered as signals indispensable for the induction of germination of seeds of root parasitic weeds, but since then, interestingly, many other biological, physiological and ecological roles have been described. This has suddenly provoked huge scientific interest in these compounds within different research fields. In this short perspective the attention is focused mainly on the ongoing and future research aimed at deciphering the biological roles of strigolactones that could positively affect, more or less directly, the management of parasitic weeds.  相似文献   
103.
Somatic cell nuclear transfer (SCNT) has been exploited in efforts to clone and propagate valuable animal lineages. However, in many instances, recipient oocytes are obtained from sources independent of donor cell populations. As such, influences of potential nuclear-cytoplasmic incompatibility, post SCNT, are largely unknown. In the present study, alterations in mitochondrial protein levels were investigated in adult SCNT pigs produced by microinjection of Meishan pig fetus fibroblast cells into enucleated matured oocytes (maternal Landrace genetic background). Mitochondrial fractions were prepared from liver samples by mechanical homogenization and differential centrifugation. Liver mitochondria were then subjected to two-dimensional difference gel electrophoresis (2-D DIGE). Protein expression changes were confirmed with a volume ratio greater than 2 fold (P<0.05). 2-D DIGE analysis further revealed differential expression of three proteins between the Meishan (n=3) and Landrace (n=3) breeds. Differential expression patterns of 16 proteins were detected in SCNT pig liver tissue (n=3) when compared with Meishan control samples. However, none of the 16 proteins correlated with the three differentially expressed Meishan and Landrace liver mitochondrial proteins. In summary, alteration of mitochondrial protein expression levels was observed in adult SCNT pigs that did not reflect the breed difference of the recipient oocytes. Comparative proteomic analysis represents an important tool for further studies on SCNT animals.  相似文献   
104.
Antioxidant and oxidative stress effects of prooxidants are generally dose-dependent, and these effects depend on the prooxidant species and cell type. However, the cellular response to oxidant challenge is a complicated interplay of events involving cellular expression of phase II detoxification enzymes and cellular metal metabolism. This study demonstrates the effect of tert-butylhydroquinone (t-BHQ)-induced oxidative stress on MDCK cells. Cell toxicity tests were carried out using the crystal violet (CV) assay with the following prooxidants: t-BHQ, diethyl maleate (DEM), hydrogen peroxide (H(2)O(2)), diquat (DQ) and β-naphthoflavone (β-NF). Except for β-NF, these prooxidants showed dose-dependent cytotoxicity besides the most potent t-BHQ cytotoxicity. Only t-BHQ and DEM caused significant time-dependent expression of ferritin protein as an antioxidant, which segregates Fe(2+), causing the Fenton reaction. t-BHQ and DEM increased formation of lipid peroxidation, but DQ showed a tendency to decrease lipid peroxidation levels. In XTT assay, even when substantial cell death was observed in the CV assay, t-BHQ appeared to increase cell viability by enhancing XTT reduction, likely through the production of NADPH. Although curcumin, which induces cytoprotective phase II enzymes and chelates metal irons, decreased cell viability, it inhibited t-BHQ cytotoxicity. These results indicate that t-BHQ exhibits strong cytotoxicity against MDCK cells, an effect mitigated by curcumin, and that t-BHQ-induced oxidative stress activates the pentose phosphate pathway.  相似文献   
105.
Growth hormone (GH) secretion regularity and the effects of lighting condition and GH‐releasing hormone (GHRH) on GH release were determined in steers. First, steers were kept under 12:12 L : D conditions (light: 06.00–18.00 hours). The animals were then subjected to a 1‐h advancement in lighting on/off conditions (05.00 and 17.00 hours, respectively). Blood was sampled for 24 h at 1‐h interval on the seventh day of each condition. Second, GHRH was injected intravenously (IV) at 12.00 and 00.00 hours under 12:12 L : D and blood was sampled at 15‐min interval for 4‐h (1 h before and 3 h after the injection). Plasma GH concentrations were measured by a radioimmunoassay. Periodicity of GH secretory profile was calculated by power spectrum analysis using the maximum entropy method. Plasma GH concentrations showed a characteristic pattern consisting of four distinct peaks. Mean periodicity of GH secretory profile was 5.7 h, and it was not altered by any change in lighting conditions. IV injection of GHRH increased GH secretion during the day and night. The increase in GH secretory volume after GHRH injection during the night was equal to that during the day. The present results suggest that GH secreted from the anterior pituitary have regularity in steers.  相似文献   
106.
Biliary sludge in dogs is dismissed commonly as an incidental finding. On the other hand, gallbladder mucocele is reported increasingly in dogs and can lead to biliary obstruction or gallbladder rupture. Cholestasis is suspected to play a role in development of sludge and mucoceles, though there are no data in dogs to support this. We investigated gallbladder emptying, a key factor in biliary flow, in dogs with mobile sludge, immobile sludge, or gallbladder mucocele and in healthy controls. Gallbladder ejection fraction estimated by ultrasonography was used as the index of gallbladder emptying. The ejection fraction at 60 min after eating was significantly decreased in all three abnormal groups. Moreover, all dogs with sludge or a mucocele had gallbladder distension. These changes were the greatest in the mucocele group. Thus, biliary stasis occurs not only in dogs with gallbladder mucocele but also in dogs with biliary sludge. Cholestasis may play a role in the pathogenesis or progression of these diseases in dogs.  相似文献   
107.
Nucleotide sequences of ribosomal internal transcribed spacer (ITS1) and mitochondrial NADH dehydrogenase I (NDI) gene were analyzed to genetically characterize aspermic Fasciola forms in Korea. From the difference in ITS1 sequences, Korean flukes were divided into 3 haplotypes represented by Kor1, Kor2 and Kor1/2, which had nucleotides identical to F. hepatica, F. gigantica and those overlapped between the two species, respectively. NDI sequences also showed that Korean flukes could be classified into 3 distinct haplotypes (Kor1: F. hepatica-type, Kor2a and Kor2b: F. gigantica-type). The sequences of Kor1 and Kor2a were 100% identical to those of the haplotypes Fsp1and Fsp2, respectively, which are major Fasciola forms in Japan. These findings strongly suggest that aspermic Fasciola forms in Korea and Japan originated from same ancestors and have recently spread throughout both countries.  相似文献   
108.
Leaves of tomato and barley were inoculated with conidia of Blumeria graminis f. sp. hordei race 1 (R1) or Oidium neolycopersici (KTP-01) to observe cytological responses in search of resistance to powdery mildew. Both conidia formed appressoria at similar rates on tomato or barley leaves, indicating that no resistance was expressed during the prepenetration stage of these fungi. On R1-inoculated tomato leaves, appressoria penetrated the papillae, but subsequent haustorium formation was inhibited by hypersensitive necrosis in the invaded epidermal cells. On the other hand, KTP-01 (pathogenic to tomato leaves) successfully developed functional haustoria in epidermal cells to elongate secondary hyphae, although the hyphal elongation from some conidia was later suppressed by delayed hypersensitive necrosis in some haustorium-harboring epidermal cells. Thus, the present study indicated that the resistance of tomato to powdery mildew fungi was associated with a hypersensitive response in invaded epidermal cells but not the prevention of fungal penetration through host papilla.  相似文献   
109.
Fungi inhabiting Japanese pear were isolated from internal tissues of cv. Nijisseiki, and culture filtrates (CFs) of 100 isolates were evaluated for their inhibitory activity against infection by Alternaria alternata Japanese pear pathotype. CFs of 11 isolates inhibited lesion formation on the pear by the pathogen. Among these isolates, CFs of five isolates inhibited spore germination. CFs of the six other isolates inhibited appressorial formation, infection hypha formation, AK-toxin production, or a combination of these actions. Analysis of sequence homology in the rDNA ITS1 regions of these isolates showed that most isolates had high homology with some fungal endophytes.  相似文献   
110.
Puumala (PUU) virus and PUU-related viruses are difficult to isolate in cell culture. To determine whether animal inoculation would be a better alternative for virus recovery, the Sotkamo strain of PUU virus was inoculated into several animal species. Newborn Mongolian gerbils (MGs), mice, and rats were infected with the Sotkamo strain by intracerebral (ic), intraperitoneal (ip), and subcutaneous (sc) inoculation. Antibodies to PUU appeared in MGs at 30 days post-infection (dpi), and in mice and rats at 15 dpi. Interestingly, virus appeared at 7 dpi in lung and brain of MGs inoculated via ic and ip routes. Virus was detected in all tested tissues of MGs at 15 dpi, with a peak level of 1.36 x 10 (5) focus forming units (FFU)/g in brain tissue. The virus titer declined with the onset of the antibody response and became undetectable by 75 dpi, when the antibody titer reached the maximum level. The appearance of the virus in mice and rats was delayed as compared to MGs, and the virus titer was apparently lower, at approximately 4 to 8 x 10(3) FFU/g, at 15 dpi. In addition, lung homogenates of antibody-positive Clethrionomys (C.) rufocanus (captured in Tobetsu, Hokkaido, Japan) were inoculated into MGs by the ic route. PUU-related viral RNA was detected at 16 dpi in the brains of MG inoculated with the lung homogenate, and antibodies were detected at 45 dpi. These findings indicate that newborn MG inoculation is an efficient method to recover PUU and PUU-related viruses.  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