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   405篇
  免费   26篇
林业   18篇
农学   8篇
基础科学   1篇
  39篇
综合类   34篇
农作物   14篇
水产渔业   10篇
畜牧兽医   253篇
园艺   2篇
植物保护   52篇
  2022年   4篇
  2021年   7篇
  2020年   7篇
  2019年   8篇
  2018年   13篇
  2017年   10篇
  2016年   6篇
  2015年   13篇
  2014年   12篇
  2013年   18篇
  2012年   18篇
  2011年   15篇
  2010年   10篇
  2009年   9篇
  2008年   16篇
  2007年   15篇
  2006年   26篇
  2005年   24篇
  2004年   19篇
  2003年   20篇
  2002年   16篇
  2001年   25篇
  2000年   20篇
  1999年   19篇
  1998年   12篇
  1997年   4篇
  1996年   3篇
  1995年   2篇
  1994年   4篇
  1992年   10篇
  1991年   10篇
  1990年   4篇
  1989年   2篇
  1988年   1篇
  1987年   3篇
  1986年   1篇
  1985年   2篇
  1984年   2篇
  1983年   2篇
  1982年   3篇
  1980年   2篇
  1978年   1篇
  1977年   3篇
  1976年   2篇
  1975年   2篇
  1974年   1篇
  1971年   1篇
  1969年   1篇
  1966年   1篇
  1964年   1篇
排序方式: 共有431条查询结果,搜索用时 15 毫秒
71.
Blooms of toxic dinoflagellates of the genus Ostreopsis, which is known as a producer of palytoxin (PTX) analogs, may pose a threat to human health in tropical, subtropical, and temperate regions around the world. In the present study, we established a suitable culture method for Ostreopsis spp. isolated from Japanese coastal waters and characterized their growth potential using the method to discuss their bloom dynamics. Each clonal strain of Ostreopsis cf. ovata, Ostreopsis sp.?1, Ostreopsis sp.?5, and Ostreopsis sp.?6 was incubated in 25?×?150?mm test tubes with a flat bottom containing various kinds of medium. Since Ostreopsis spp. strains grew well in IMK and/or f/2 media, we selected these media for cultivation of all the Ostreopsis spp. isolates. Growth rates of O. cf. ovata (0.834?divisions/day), Ostreopsis sp.?1 (0.619?divisions/day), and Ostreopsis sp.?6 (1.04?divisions/day) that produce PTX analogs significantly differed (p?<?0.05) respectively and are clearly higher than those of other reported epiphytic dinoflagellate Gambierdiscus toxicus, Prorocentrum lima, and Coolia monotis cultures, which suggest that these species have ecological advantages to predominate through the algal succession in Japanese coastal waters, resulting in a potential risk to human health in this region.  相似文献   
72.
Cardiopulmonary and sedative effects of intravenous or epidural methadone were compared. Six beagles were randomly assigned to group MIV (methadone 0.5 mg/kg IV + NaCl 0.9% epidurally) or MEP (methadone 0.5 mg/kg epidurally + NaCl 0.9% IV). Cardiopulmonary, blood gas and sedation were assessed at time (T) 0, 15, 30, 60, 120, 240 and 480 min after drug administration. Compared to T0, heart rate decreased at T15–T120 in MIV (< .001) and T15–T240 in MEP (< .05); mean arterial pressure was reduced at T15–T60 in MEP (< .01); respiratory rate was higher at T15 and T30 in both groups (< .05); pH was lower at T15–T120 in MIV (< .01) and T15, T30 and T120 in MEP (< .05); PaCO2 was higher at T15–T60 in MIV (< .01) and T15, T30 and T120 in MEP (< .01); sedation scores were higher at T15 and T30 in MIV and T15–T60 in MEP (< .05). At T120 and T240, sedation score was higher in group MEP compared with group MIV (< .01) In conclusion, cardiopulmonary and sedative effects of identical methadone doses are similar when administered IV or epidurally to conscious healthy dogs.  相似文献   
73.
Pulsating aurora, a spectacular emission that appears as blinking of the upper atmosphere in the polar regions, is known to be excited by modulated, downward-streaming electrons. Despite its distinctive feature, identifying the driver of the electron precipitation has been a long-standing problem. Using coordinated satellite and ground-based all-sky imager observations from the THEMIS mission, we provide direct evidence that a naturally occurring electromagnetic wave, lower-band chorus, can drive pulsating aurora. Because the waves at a given equatorial location in space correlate with a single pulsating auroral patch in the upper atmosphere, our findings can also be used to constrain magnetic field models with much higher accuracy than has previously been possible.  相似文献   
74.
75.
The germicidal activity of pyroligneous acid (PA) against a picornavirus, encephalomyocarditis virus (EMCV), was analyzed, and the component responsible for its disinfectant activity was identified. Bamboo PA (BPA) inactivated EMCV, but neutralization of BPA abolished this activity. Using liquid-liquid phase extraction and silica gel column chromatography, the hydrophobic active fraction of BPA was separated and its 12 major components were identified. The active fraction was reconstructed by mixing synthetic chemicals at the determined concentrations, and a subtraction series of one chemical from the complete mixture was prepared. An in vitro virus assay demonstrated that phenol was the sole germicidal component, and acetic acid augmented the phenol's inactivating activity resulting in >5-log decrease in EMCV infectivity. Considering the low environmental risk of PA, these findings suggest that BPA is a potentially useful agent for preventing viral epidemics in agricultural and human environments.  相似文献   
76.
Soil solarization practice, in which soil is covered with plastic mulch film and exposed to high temperature prior to crop cultivation, is expected to be an effective method for reducing weeds and pathogenic microorganisms without using agricultural chemicals. Although the production of nitrous oxide (N2O), a major greenhouse gas, is enhanced in fertilized soil covered with plastic mulch films, its transport route to the atmosphere has not been sufficiently elucidated to date. In this study, we investigated the N2O evolution from plastic-mulch-film-covered agricultural soil. In a horticultural field where ridge soil was covered with a plastic mulch film after fertilization, we observed significant N2O flux from the soil surface of the unfertilized furrow between the ridges, indicating the horizontal diffusion of N2O from the ridge soil covered with the mulch film to the adjacent furrow soil surface. On the other hand, the measurement of the permeance (permeation coefficient) of the plastic mulch film for gaseous N2O by laboratory experiment revealed that N2O gradually permeated the mulch film; the permeance increased exponentially with an increase in ambient temperature, indicating possible N2O emission by permeation through the mulch film under field conditions. In winter, the amount of N2O emission by permeation through the mulch film was estimated to be lower than that emitted from the furrow soil surface, and it was lower than that in summer. On the other hand, it was estimated to be much higher in summer owing to the higher permeance of the film at high temperatures.  相似文献   
77.
78.
This study attempted to establish a culture model to recreate the milk production pathway in bovine mammary epithelial cells (BMECs). BMECs were isolated from Holstein cows (nonlactating, nonpregnant, and parous) and were stored by cryopreservation. To separate the apical and basolateral compartments, BMECs were cultured on a cell culture insert with a collagen gel in the presence of bovine pituitary extract and dexamethasone to induce milk production and tight junction (TJ) formation. The culture model showed the secretion of the major milk components, such as β‐casein, lactose, and triglyceride, and formed less‐permeable TJs in BMECs. Moreover, the TJs were distinctly separated from the apical and basolateral membranes. Glucose transporter‐1, which transports glucose into the cytoplasm through the basolateral membrane, localized in the lateral membrane of BMECs. Toll‐like receptor‐4, which binds to lipopolysaccharide in the alveolar lumen in mastitis, localized in the apical membrane. Beta‐casein was mainly localized near the Golgi apparatus and the apical membrane. Moreover, milk components were almost secreted into the upper chamber of the cell culture insert. These findings indicate that this model has clear cell polarity as well as in vivo and is effective to study of milk production and the blood–milk barrier in lactating BMECs.  相似文献   
79.
80.
The ascomycete Cistella japonica was cultured on potato dextrose agar medium (PDA) for inoculation into Chamaecyparis obtusa, enabling the development of an inoculation method suitable for use in a breeding programme aimed at selecting for families of Ch. obtusa resistant to resinous stem canker. Using PDA to generate the inoculum resolved the problems encountered with the previously used mixed medium of rice bran and wheat bran, including unfavourable characteristics, uncertain growth of Ci. japonica mycelia, and a complex culturing operation. The inoculation test induced resin exudation similar to that observed in natural infections, and reproduced clonal differences with regard to damage severity.  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