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   433篇
  免费   16篇
  国内免费   1篇
林业   25篇
农学   4篇
基础科学   1篇
  119篇
综合类   17篇
农作物   37篇
水产渔业   16篇
畜牧兽医   202篇
园艺   10篇
植物保护   19篇
  2024年   2篇
  2023年   4篇
  2022年   9篇
  2021年   17篇
  2020年   12篇
  2019年   28篇
  2018年   18篇
  2017年   12篇
  2016年   18篇
  2015年   15篇
  2014年   18篇
  2013年   24篇
  2012年   32篇
  2011年   35篇
  2010年   15篇
  2009年   14篇
  2008年   31篇
  2007年   24篇
  2006年   24篇
  2005年   22篇
  2004年   27篇
  2003年   17篇
  2002年   15篇
  2001年   1篇
  1998年   1篇
  1996年   1篇
  1995年   1篇
  1994年   1篇
  1993年   4篇
  1991年   2篇
  1990年   1篇
  1989年   1篇
  1988年   2篇
  1984年   1篇
  1983年   1篇
排序方式: 共有450条查询结果,搜索用时 15 毫秒
81.
82.
Lions (Panthera leo) are an endangered species threatened by illegal hunting, habitat loss, and infectious diseases. Little is known about the tick-borne pathogens that infect lions and could contribute to population declines. The objective of this study was to characterize Rickettsia spp., Anaplasma phagocytophilum, and Coxiella burnetii infections in 10 lions from the Fasano Safari Park in Italy by serology, polymerase chain reaction, and sequence analysis. Although animals did not show clinical signs of tick-borne diseases, evidence of infection with C. burnetii, spotted fever group Rickettsia sp., and A. phagocytophilum were found in 50%, 20%, and 10% of the lions, respectively. One of the lions tested positive for all three pathogens. This study is the first report of molecular evidence of infection with C. burnetii, Rickettsia sp., and A. phagocytophilum in lions and provides evidence that these felids become infected and serve as hosts for tick-transmitted bacteria.  相似文献   
83.
A case of leishmaniosis in domestic cats (Felis catus domesticus) is described. The subject showed a nodular lesion on the eyelid. The diagnosis was achieved by serological, parasitological, and light and electron microscopic investigations. By molecular techniques the aetiological agent was identified as belonging to Leishmania infantum, the species implicated in human and canine leishmaniosis in southern Europe. A preliminary study on the prevalence of asymptomatic feline leishmaniosis, performed in the areas where the infected cat was identified, revealed a low seroprevalence of infection: only 1 (0.9%) of the 110 cat sera examined by indirect fluorescent antibody test was positive for anti-Leishmania antibodies. Because clinical signs in feline leishmaniosis are unspecific and similar to those observed in other diseases commonly found in this species, leishmaniosis must be added to the differential diagnosis by feline veterinary practitioners and adequate serologic and histopathologic investigations must be performed in endemic areas.  相似文献   
84.
Infrared spectra of material captured from comet 81P/Wild 2 by the Stardust spacecraft reveal indigenous aliphatic hydrocarbons similar to those in interplanetary dust particles thought to be derived from comets, but with longer chain lengths than those observed in the diffuse interstellar medium. Similarly, the Stardust samples contain abundant amorphous silicates in addition to crystalline silicates such as olivine and pyroxene. The presence of crystalline silicates in Wild 2 is consistent with mixing of solar system and interstellar matter. No hydrous silicates or carbonate minerals were detected, which suggests a lack of aqueous processing of Wild 2 dust.  相似文献   
85.
Carbon and nitrogen mineralisation of leather meal fertilisers were studied in two soils characterised by different respiration activity. Both C and N mineralisation were highest in the most active soil, and when leather meal was added as a powder rather than as 2- to 4- and 4- to 6-mm particles. Fast and slow soluble N pools were determined after extraction with cold water and with hot buffer, respectively. The N remaining after the second extraction with hot buffer was named slow-release N. The percentage of slow-release N rose as the size of the applied leather meal particles increased, whereas fast soluble N was highest in the coarsest (4-6 mm) fertiliser.  相似文献   
86.
During a six-month period a region of Northern Sardinia was monitored to check the presence of mycobacterial infections in wild boars. Forty-eight serum and 229 biopsy samples were collected from different animals and examined by both traditional diagnostic techniques (culture, bacterioscopic and molecular tests) and enzyme-linked immunosorbent assay (ELISA). The latter was used to determine the antibody response against both methylated and nonmethylated Heparin-Binding Haemagglutinin (HBHA) protein. Nine mycobacterial strains were isolated: three M. avium ssp. paratuberculosis (Map), three M. avium, one M. interjectum and two M. scrofulaceum strains. By PCR, only one animal was positive for M. bovis, whereas 10 animals were positive for Map. Out of the 48 sera tested, 19 showed a good humoral response to methylated HBHA and 17 to nonmethylated HBHA. Our data provide new information on the prevalence of mycobacterial infection among wild boars in Northern Sardinia and suggest that a more effective program should be developed to monitor mycobacterial infections in the wild animal population.  相似文献   
87.
We describe a case of proximal mandibular nerve block with ropivacaine, using electrolocation, for perioperative pain management in a geriatric dog undergoing rostral mandibulectomy. The patient did not require intraoperative analgesia or analgesic supplementation for 8 h after the end of the surgery.  相似文献   
88.

Background

Porcine circovirus type 2 (PCV2) has been associated with several disease complexes, including reproductive failure. The aim of this study was to identify the subtypes of PCV2 that are associated with reproductive failure in pigs from the State of São Paulo, Brazil and to investigate co-infections with other infectious organisms.

Findings

Samples of 168 aborted foetuses or mummified foetuses from five farrow-to-finish swine farms known to be infected with PCV2 and located in the State of São Paulo were tested for PCV2 by polymerase chain reaction (PCR). Positive samples were additionally tested for porcine parvovirus (PPV), Leptospira spp. and Brucella spp. by PCR. PCV2 was detected in 18 of the samples (10.7%). PPV, Brucella spp. and Leptospira spp were found in 2, 10 and 0 cases, respectively. Eleven PCV2 strains were sequenced and determined to be either genotype 2a (n = 1) or 2b (n = 10).

Conclusions

The findings indicate that the frequency of PCV2 infections in aborted porcine foetuses from the State of São Paulo is rather low (10.7%) and that co-infection with other pathogens is common and may be involved in PCV2 associated reproductive failure. No repeatable, characteristic amino acid motifs for regions of the PCV2 capsid protein seemed to be associated with abortion in sows.  相似文献   
89.
The phenolic fraction of virgin olive oil influences both its quality and oxidative stability. One of the principal threats of the quality of olive fruit is the olive fly ( Bactrocera oleae) as it alters the chemical composition. The attack of this olive pest has been studied in order to evaluate its influence on the quality of virgin olive oil (free acidity, peroxide value, fatty acid composition, water content, oxidative stability, phenols, and antioxidant power of phenolic fraction). The study was performed using several virgin olive oils obtained from olives with different degrees of fly infestation. They were acquired in different Italian industrial mills from the Abruzzo region. Qualitative and quantitative analyses of phenolic profiles were performed by capillary electrophoresis-diode array detection, and electrochemical evaluation of the antioxidant power of the phenolic fraction was also carried out. These analyses demonstrated that the degree of fly attack was positively correlated with free acidity ( r = 0.77, p < 0.05) and oxidized products ( r = 0.58, p < 0.05), and negatively related to the oxidative stability index ( r = -0.54, p < 0.05) and phenolic content ( r = -0.50, p < 0.05), mainly with secoiridoid compounds. However, it has been confirmed that the phenolic fraction of olive oil depends on several parameters and that a clear correlation does not exist between the percentages of fly attack and phenolic content.  相似文献   
90.
A number of virus elimination protocols have been developed to obtain healthy plants but their success rates have been variable due to the strong virus–host relationship, treatment performances and experimental condition. An in vitro collection of plants of Vitis berlandieri × Vitis riparia Kober 5BB single-infected by Grapevine vitivirus A (GVA), Grapevine fanleaf nepovirus (GFLV), Grapevine fleck maculavirus (GFkV), Grapevine leafroll ampelovirus 1 (GLRaV-1) and Grapevine leafroll ampelovirus 3 (GLRaV-3) was established to carry out thermotherapy treatments. The experimental system allowed to control the effects of host genotype by using the same genetic background, and the environmental condition such as relative humidity, soil and temperature conditions. Trials were conducted in a growth chamber set at 37 ± 0.5 °C for 48 days using in vitro cultures for all infections. ELISA and RT-PCR were used to check sanitary conditions. Results showed complete eradication of GFLV and no effect against GFkV. Different sanitation rates were obtained for other phloematic viruses: 70.2% for GVA, 25.1% for GFLaV-1 and 24.7% for GLRaV-3. The results on phloematic viruses showed a gradient of elimination efficiency which could not be completely explained with the location of viral particles that seems to be only one of the several factors affecting virus susceptibility to heat stress. Moreover, the advantages of this experimental system provide the opportunity to obtain a greater understanding of the thermotherapeutic effects on phloematic 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