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   170篇
  免费   10篇
林业   16篇
农学   4篇
基础科学   1篇
  24篇
综合类   24篇
农作物   8篇
水产渔业   8篇
畜牧兽医   81篇
园艺   2篇
植物保护   12篇
  2022年   2篇
  2021年   4篇
  2020年   6篇
  2019年   6篇
  2018年   4篇
  2017年   6篇
  2016年   4篇
  2015年   4篇
  2014年   9篇
  2013年   9篇
  2012年   13篇
  2011年   18篇
  2010年   6篇
  2009年   7篇
  2008年   5篇
  2007年   3篇
  2006年   8篇
  2005年   5篇
  2004年   7篇
  2003年   4篇
  2002年   7篇
  2001年   1篇
  2000年   1篇
  1999年   4篇
  1998年   1篇
  1996年   1篇
  1995年   1篇
  1993年   2篇
  1991年   3篇
  1990年   3篇
  1989年   3篇
  1988年   2篇
  1987年   1篇
  1981年   1篇
  1980年   1篇
  1978年   2篇
  1974年   1篇
  1972年   1篇
  1971年   1篇
  1968年   3篇
  1967年   2篇
  1966年   3篇
  1926年   2篇
  1925年   3篇
排序方式: 共有180条查询结果,搜索用时 31 毫秒
1.
2.
3.
Hypertrophic scarring and poor intrinsic axon growth capacity constitute major obstacles for spinal cord repair. These processes are tightly regulated by microtubule dynamics. Here, moderate microtubule stabilization decreased scar formation after spinal cord injury in rodents through various cellular mechanisms, including dampening of transforming growth factor-β signaling. It prevented accumulation of chondroitin sulfate proteoglycans and rendered the lesion site permissive for axon regeneration of growth-competent sensory neurons. Microtubule stabilization also promoted growth of central nervous system axons of the Raphe-spinal tract and led to functional improvement. Thus, microtubule stabilization reduces fibrotic scarring and enhances the capacity of axons to grow.  相似文献   
4.
Ohne Zusammenfassung Vgl. Gilmer, Paul M., Derris as a Parasticide. Nineteenth Report, State Entomologist of Minnesota, 1922.  相似文献   
5.
The aim of the study was to describe and evaluate competitiveness of Estonian spice-cured sprat products in Estonia and Thailand. Sample A was saltiest, Sample B had lowest overall spiciness, and Sample C had highest pepper flavor and sour taste intensity. The main drivers of consumer acceptance for the spice-cured sprat products were different: flavor and appearance in Estonia and appearance and odor in Thailand. In Estonia, one cluster of consumers liked the traditional (Sample A) and lightly spiced (Sample B) sprat products, while the other cluster liked the traditional (Sample A) and the marinated (Sample C) sprat products. In Thailand, all samples scored low, but manual clustering indicated that marinated (Sample C) sprat products are most acceptable. The current study showed that spice-cured sprat products in general can be accepted by Thai consumers, especially as part of meals, if further flavor development is carried out with the products.  相似文献   
6.
During the period 2000–03, local potato cultivars in Estonia, Latvia, Lithuania, Poland and Denmark were tested for foliar resistance to Phytophthora infestans (late blight) in an international field trial network. Four standard cultivars were included in the trials: Sava, Oleva, Danva and Kuras. Primary disease-assessment data were entered into a common database, and parameters from the disease progress curves were calculated and made available on interactive web pages. A regression model, using relative area under disease progress curve (RAUDPC) values for cv. Oleva as a reference, was developed for the estimation of 1–9 scale values, where 1 = most susceptible. Standard deviations for the estimated 1–9 scale values and a nonparametric rank stability analysis of RAUDPC were used to evaluate the stability of resistance of the cultivars. Overall, the results showed stability of resistance for cvs Sava, Oleva and Danva, but not for Kuras. Use of the Internet-based Web-Blight service in this study facilitated comparison of results among countries for the level and stability of resistance. The estimated 1–9 scale values were similar to, or slightly lower than, those from official cultivar lists or from the European Cultivated Potato Database, especially for the more resistant cultivars. Possible reasons for discrepancies from different sources and locations are discussed. It is concluded that RAUPDC and the derived 1–9 scale values are useful for ranking cultivars for resistance to P. infestans , but this information is not detailed enough for use in a decision support system for late blight control.  相似文献   
7.
Panosteitis, an idiopathic bone disease of young dogs, was investigated in the light of a new, empirically based hypothesis governing its pathogenesis. Extensive clinical observations suggest a close relationship between the incidence of this disease and the commercialization of various protein-rich, high-calorie dog foods. The theory of an "osseous compartment syndrome" provides a hypothetical pathogenesis, which corroborates this findings. An excessive accumulation of protein causes intraosseous edema due to its osmotic effects. Because bone is a rigid compartment, this leads to an increase in intramedullary pressure and compression of blood vessels. Subsequent osseous ischemia leads to a deficient metabolic state (decreased oxygenation, inadequate influx of nutritive substances, local acidosis, decreased removal of metabolites, disruption of local biochemical processes, etc.), and a vicious circle is created due to the resulting local inflammation. The disease is aggravated by increased metabolism due to excessive physical activity. Within the context of a pilot study, clinical, radiographic, scintigraphic and thermographic examinations and a therapeutic trial with benzopyron were carried out. In addition, more modern investigative tools, including osteomyelography, magnetic resonance tomography and intraosseous pressure measurements were used to provide objective data concerning the pathogenesis of panosteitis. In most cases, clinical remission was seen within days of monotherapy with the proteolytic substance, benzopyron (Cumartrin). This finding appears to corroborate our hypothesis.  相似文献   
8.
The spatial distribution of endemic bovine tuberculosis (TB) in Argentine cattle herds was described using recorded information on the detection of TB-like lesions in cattle slaughtered between March 1995 and 1997 at 126 slaughterhouses with federal inspection. Approximately, 47% (9472396 cattle) of the estimated total number of cattle slaughtered in Argentina during this period was included in the study. Information on the number of cattle per source herd consigned to slaughter, number of cattle with TB-like lesions per herd and the geographical location of counties from which cattle originated was used to investigate spatial clustering of TB. Overall, no evidence of clustering of TB prevalence by county was detected (Moran's autocorrelation statistic I=0.009, P=0.089). However, first- (Cuzick and Edwards' test statistic, T(k)=87, P=0.036) and second-order (T(k)=170, P=0.038) nearest-neighbor case-counties (TB prevalence>median prevalence of all counties, 6.7%) were clustered. Using the spatial scan test based on a Bernoulli model, the most-likely cluster (P=0.001) identified during the study period included 5793 cases of TB (5.2 per 1000 km(2)) in five counties. This cluster coincided with Santa Fe Province, which contains 21% of all dairy cows in Argentina and accounts for 34% of the country's milk production. Several secondary clusters of TB-also located in dairy districts-were identified. Study results demonstrate that bovine TB is clustered in Argentina, and these clusters coincide with dairy cattle production. Identification of clustering can assist efforts to eradicate bovine TB from Argentina. Further spatial investigations need to focus on the reasons why TB is clustered in Argentina. In particular, the relationship between TB clustering and management practices-such as grazing density and production systems-need to be described to assist in the development of disease-control programs. The use of spatial statistics and geographical information systems could meet these needs.  相似文献   
9.
Transmission of bovine tuberculosis was quantified in three dairy herds located in south Santa Fe Province, Argentina. Using estimates of Mycobacterium bovis transmission (β) and a Reed–Frost simulation model, the prevalence of tuberculosis infection in the study herds over time was investigated. The Reed–Frost model was modified by incorporating randomness in both β and the incubation period () of M. bovis. The mean estimated herd β was 2.2 infective contacts per year and did not differ significantly between the study herds. Modeling as Poisson distributed (mean 24 months) best fit the observed prevalences. Infection was predicted by the model either to spread quickly (<10 years) within a herd and reach a high prevalence (>50%), or to persist at a low prevalence (<5–10%). The model was robust, predictions were realistic and the mean β estimated was consistent with previous studies of bovine tuberculosis.  相似文献   
10.
We have examined the effect of Pen, an aqueous extract of the dry mycelium of Penicillium chrysogenum, on plant–pathogen interactions. Pen controlled a broad range of pathogens on several crop plants under greenhouse and field conditions. Pen protected grapevine from downy and powdery mildew (caused by Plasmopara viticola and Uncinula necator), tomato from early blight (caused by Phytophthora infestans), onion from downy mildew (Peronospora destructor) and apple trees from apple scab (caused by Venturia inaequalis) to a similar extent as fungicides such as copper and sulphur or well-known inducers such as benzothiadiazole or β-aminobutyric acid. Pen had no major direct fungicidal effect and is thus supposed to protect plants by activating their defense mechanisms. The raw material for extraction of Pen was available in constant quality, a prerequisite for commercial application. Under certain conditions, Pen caused phytotoxic side effects. The symptoms mostly consisted of small necrotic spots or, more rarely, of larger necrotic areas. The development of the symptoms was dependent on several parameters, including concentration of Pen, the number of applications, the persistence on the plant tissue, the plant species and variety and environmental conditions. In grapevine, a partially purified fraction of Pen was much less toxic than the crude Pen extract, but protected the plants to a similar extent against P. viticola. Our data show that Pen has interesting and unique properties as a plant protection agent, but more research is needed to further reduce its phytotoxic side effects.  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