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   375篇
  免费   18篇
林业   19篇
农学   8篇
  105篇
综合类   46篇
农作物   30篇
水产渔业   46篇
畜牧兽医   104篇
园艺   7篇
植物保护   28篇
  2023年   2篇
  2022年   2篇
  2021年   6篇
  2020年   6篇
  2019年   8篇
  2018年   9篇
  2017年   8篇
  2016年   9篇
  2015年   5篇
  2014年   10篇
  2013年   24篇
  2012年   33篇
  2011年   34篇
  2010年   17篇
  2009年   8篇
  2008年   26篇
  2007年   38篇
  2006年   26篇
  2005年   10篇
  2004年   11篇
  2003年   8篇
  2002年   9篇
  2001年   9篇
  2000年   5篇
  1999年   3篇
  1998年   3篇
  1997年   3篇
  1994年   2篇
  1992年   6篇
  1991年   3篇
  1990年   2篇
  1989年   4篇
  1987年   2篇
  1985年   2篇
  1980年   3篇
  1979年   4篇
  1978年   2篇
  1974年   3篇
  1973年   2篇
  1972年   2篇
  1971年   3篇
  1969年   1篇
  1968年   1篇
  1966年   1篇
  1965年   1篇
  1964年   3篇
  1963年   2篇
  1945年   1篇
  1930年   2篇
  1929年   1篇
排序方式: 共有393条查询结果,搜索用时 31 毫秒
51.
A Bayesian population modelling tool integrating separable virtual population analysis, per‐recruit models and age‐structured demographic analysis was developed for the bigeye thresher Alopias superciliosus (Lowe) population in an area subset of the western North Pacific. The mortality rates for years 1989–2016 were estimated, various biological reference points and associated risks of decline were also estimated, and alternative harvest strategies for the stock were evaluated. Estimates of the posterior mean of fishing mortality for bigeye thresher shark suggest fishing pressure has been high in recent years (2011–2016). The estimated population growth rate (λ) (without fishing) obtained from age‐structured demographic model was relatively low (λ = 1.01 per year; 95% confidence intervals of 1.00 and 1.03 per year). Risk analyses revealed that only low levels of fishing pressure (10% of the current fishing pressure) over a wide range of ages could maintain a relatively low risk of population decline for bigeye threshers. Sensitivity testing indicated that the model is robust to prior specification. The developed framework could be used as an assessment tool to evaluate the risk of decline for other widely distributed pelagic shark species where insufficient catch and effort data are available.  相似文献   
52.
Proximate compositions of dorsal, ventral, leg, and tail cuts of farmed spectacled caiman (Caiman crocodilus) were determined. The water, protein, fat, and ash contents of muscle were 77–78%, 19–23%, 0.3–1.2%, and 1.0%, respectively. The dominant nucleotide-related compound in the tissues was inosine monophosphate (IMP) (68.6–84.9%). The predominant free amino acids (FAAs) in the muscle of spectacled caiman were taurine (Tau), glycine (Gly), alanine (Ala), and histidine (His), along with a dipeptide of anserine (Ans) (80–183 mg/100 g) and carnosine (Car) (35–103 mg/100 g) being detected in each sample. The major fatty acid composition included palmitic (16:0), oleic (18:1 cis-9), linoleic (18:2n-6), and stearic (C18:0) acids. The amount of docosahexaenoic acid (4.27–8.76%) was higher than that of eicosapentaenoic acid (0.99–2.24%). The ratio of polyunsaturated fatty acid/saturated fatty acid in spectacled caiman (0.83–1.19) was higher than that in other commonly consumed meat. Meat from the spectacled caiman can be characterized as a valuable food for human consumption in terms of these nutritional features.  相似文献   
53.
Dihydroaustrasulfone alcohol is the synthetic precursor of austrasulfone, which is a marine natural product, isolated from the Taiwanese soft coral Cladiella australis. Dihydroaustrasulfone alcohol has anti-inflammatory, neuroprotective, antitumor and anti-atherogenic properties. Although dihydroaustrasulfone alcohol has been shown to inhibit neointima formation, its effect on human vascular smooth muscle cells (VSMCs) has not been elucidated. We examined the effects and the mechanisms of action of dihydroaustrasulfone alcohol on proliferation, migration and phenotypic modulation of human aortic smooth muscle cells (HASMCs). Dihydroaustrasulfone alcohol significantly inhibited proliferation, DNA synthesis and migration of HASMCs, without inducing cell death. Dihydroaustrasulfone alcohol also inhibited platelet-derived growth factor (PDGF)-induced expression of cyclin-dependent kinases (CDK) 2, CDK4, cyclin D1 and cyclin E. In addition, dihydroaustrasulfone alcohol inhibited PDGF-induced phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), whereas it had no effect on the phosphorylation of phosphatidylinositol 3-kinase (PI3K)/(Akt). Moreover, treatment with PD98059, a highly selective ERK inhibitor, blocked PDGF-induced upregulation of cyclin D1 and cyclin E and downregulation of p27kip1. Furthermore, dihydroaustrasulfone alcohol also inhibits VSMC synthetic phenotype formation induced by PDGF. For in vivo studies, dihydroaustrasulfone alcohol decreased smooth muscle cell proliferation in a rat model of restenosis induced by balloon injury. Immunohistochemical staining showed that dihydroaustrasulfone alcohol noticeably decreased the expression of proliferating cell nuclear antigen (PCNA) and altered VSMC phenotype from a synthetic to contractile state. Our findings provide important insights into the mechanisms underlying the vasoprotective actions of dihydroaustrasulfone alcohol and suggest that it may be a useful therapeutic agent for the treatment of vascular occlusive disease.  相似文献   
54.
Disease outbreaks occurred during 2007–2013 in Taiwan with 2.5–10% mortality among the cage cultured cobia, Rachycentron canadum (L.), characterized by the presence of polyserositis, pericarditis and peritonitis. The micro‐organisms isolated from internal organs were Gram‐positive cocci. The isolates were confirmed as Streptococcus dysgalactiae by a polymerase chain reaction assay that yielded the expected specific 259 bp amplicon. Additionally, partial sequence of the 16S–23S rDNA intergenic spacer region of the GCS strain isolates from fish was also compared and produced 100% sequence identity with S. dysgalactiae (GenBank accession number AB252398 ). The genetic characterization was then determined by pulsed‐field gel electrophoresis (PFGE) analysis. Based on PFGE, the Apa I or Sma I digestion patterns of chromosomal DNA of these isolates were grouped into three main clusters. Taiwanese strains were divided into two clusters, and the tet(M) gene was detected in cluster 1 (pulsotypes: A1–A2 and S1–S3), but not in cluster 2 strains (pulsotypes: A3–A4 and S4–S5). Three Japanese strains from amberjack, Seriola dumerili (Risso), were grouped into cluster 3 (pulsotypes: A5–A7 and S6–S8) and displayed no mortality to cobia in the challenge experiment. Conversely, Taiwanese strains from cobia and snubnose pompano, Trachinotus blochii (L.), displayed a mortality rate of 50–87.5% in cobia.  相似文献   
55.
Sinulariolide, an isolated compound from the soft coral Sinularia flexibilis, possesses the anti-proliferative, anti-migratory and apoptosis-inducing activities against the TSGH bladder carcinoma cell. The anti-tumor effects of sinulariolide were determined by 3-(4,5-cimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay, cell migration assay and flow cytometry, respectively. Sinulariolide inhibited the growth and migration of bladder carcinoma cells in a dose-dependent manner, as well as induced both early and late apoptosis as determined by the flow cytometer. Also, the sinulariolide-induced apoptosis is related to the mitochondrial-mediated apoptosis via caspase-dependent pathways, elucidated by the loss of mitochondrial membrane potential, release of cytochrome C, activation of caspase-3/-9, Bax and Bad, as well as suppression of Bcl-2/Bcl-xL/Mcl-1. Detection of the PARP-1 cleaved product suggested the partial involvement of caspase-independent pathways. Moreover, inhibition of p38MAPK activity leads to the rescue of the cell cytotoxicity of sinulariolide-treated TSGH cells, indicating that the p38MAPK pathway is also involved in the sinulariolide-induced cell apoptosis. Altogether, these results suggest that sinulariolide induces apoptosis against bladder cancer cells through mitochondrial-related and p38MAPK pathways.  相似文献   
56.
ABSTRACT

Vibrio parahaemolyticus is a human pathogen frequently found in seafood. Once the seafood is contaminated by V. parahaemolyticus, it can become a vehicle for foodborne illness. The conventional culture methods for detection of V. parahaemolyticus are time-consuming and cannot differentiate pathogenic strains from nonpathogenic ones. In this study, a multiplex polymerase chain reaction (PCR) technique was investigated for detecting tdh, chiA, and toxR of V. parahaemolyticus. The sensitivity of the multiplex PCR was determined by testing 28 strains of V. parahaemolyticus, 15 non-V. parahaemolyticus strains, and fresh seafood spiked with cells of V. parahaemolyticus. All the strains were analyzed for production of thermostable direct hemolysin (TDH) and chitinase. This study showed that both the chiA and toxR are excellent markers for detecting V. parahaemolyticus strains, and a multiplex PCR targeting chiA and tdh genes can be applied to simultaneously detect environmental and pathogenic V. parahaemolyticus.  相似文献   
57.
Seven species of cultivated and edible seaweeds found in Southern Taiwan—including Enteromorpha intestinalis, Monostorma nitidum, Ulva lactuca, Dictyopteris undulata, Sargassum hemiphyllum var. chinense, Laurencia intermedia, and Porphyra dentate—were used to determine their antioxidant activity by different extraction methods. All seaweeds were extracted using water at 90°C, sterilization at 121°C, homogenization, or enzymatic hydrolysis. Extracts were evaluated for their free radical-scavenging capacity using 1,1-diphenyl-2-pricrylhydrazyl (DPPH), their reducing power, and their superoxide anion scavenging activity. The DPPH-scavenging capacity of S. hemiphyllum var. chinense extracts produced by sterilization (98.59%), homogenization (94.72%), and carbohydrate-degrading enzyme treatment was higher than that of protease extracts, except for U. lactuca. The reducing power of S. hemiphyllum var. chinense water extracts and M. nitidum Viscozyme extracts was better than that of a commercial antioxidant. S. hemiphyllum var. chinense exhibited higher superoxide anion scavenging activity than the other species. The results demonstrate that different extracts of some of the seaweeds showed remarkable antioxidant activity in different assays. The results also provide important information for the marine food industry and suggest that seaweed might be a valuable source of natural antioxidants.  相似文献   
58.
To produce a thermostable and neutral phytase (phy) of Bacillus subtilis E20 in Escherichia coli HMS174 and evaluate its efficiency in improving growth performance. The phy C of B. subtilis E20 was expressed in E. coli HMS 174, and then the 42‐kDa recombinant phy C was purified by Ni‐NAT and analysed by SDS–PAGE. The recombinant phy C had optimal ranges of pH of 6 ~ 7 and temperature of 50 ~ 60 °C. A thermostability analysis showed that the enzyme is a thermostable phytase, and around 33% of residual activity was detected after being incubated at 90 ~ 100 °C for 10 min. The recombinant phy C‐pretreated soybean meal for feed preparation improved white shrimp, Litopenaeus vannamei, growth and feed efficiency. Overall, the neutral and thermostable phy C is suitable for aquafeed, and it is able to improve the nutritional utilization, resulting in enhanced shrimp growth and reduced feed costs.  相似文献   
59.
Twenty-four isolates of Chilli veinal mottle virus (ChiVMV) from China, India, Indonesia, Taiwan and Thailand were analysed to determine their genetic relatedness. Pathogenicity of virus isolates was confirmed by induction of systemic mosaic and/or necrotic ringspot symptoms on Capsicum annuum after mechanical inoculation. The 3' terminal sequences of the viral genomic RNA were determined. The coat protein (CP) coding regions ranged from 858 to 864 nucleotides and the 3' untranslated regions (3'UTR) from 275 to 289 nucleotides in length. All isolates had the inverted repeat sequence GUGGNNNCCAC in the 3'UTR. The DAG motif, conserved in aphid-transmitted potyviruses, was observed in all isolates. All 24 isolates were considered as belonging to ChiVMV because of their high CP amino acid and nucleotide identity (more than 94·8 and 89·5%, respectively) with the reported ChiVMV isolates including the pepper vein banding virus (PVBV), the chilli vein-banding mottle virus (CVbMV) and the CVbMV Chiengmai isolate (CVbMV-CM1). Based on phylogenetic analysis, ChiVMV isolates including all 24 isolates tested, PVBV, CVbMV and CVbMV-CM1 can be classified into three groups. In addition, a conserved region of 204 amino acids with more than 90·2% identity was identified in the C terminal of the CP gene of ChiVMV and Pepper veinal mottle virus (PVMV), and may explain the serological cross reaction between these two viruses. The conserved region may also provide useful information for developing transgenic resistance to both ChiVMV and PVMV.  相似文献   
60.
A multiplex polymerase chain reaction (m-PCR) technique was developed as a rapid and accurate diagnostic tool for identifying five major Gram-negative bacilli -Vibrio vulnificus, V. parahaemolyticus, Aeromonas hydrophila, Chryseobacterium meningosepticum and Edwardsiella tarda- that cause major diseases in cultured aquatic animals in Taiwan. The expected amplicons for V. vulnificus, V. parahaemolyticus, A. hydrophila, C. meningosepticum and E. tarda were 410, 368, 685, 180 and 230bp, respectively. The assay was shown to be specific for the target pathogens. The sensitivities of detection were estimated to be 20.5fg~200pg of genomic DNA or 10(2) ~10(4) colony-forming units (cfu) of bacterial isolates when adopted as PCR templates. The m-PCR was capable of simultaneously amplifying target fragments from bacterial genome DNA mixed with the DNA extracted from viscera and tissues taken from fish without affecting the performance of the method.  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