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   293篇
  免费   21篇
林业   21篇
农学   8篇
基础科学   1篇
  79篇
综合类   19篇
农作物   24篇
水产渔业   41篇
畜牧兽医   95篇
园艺   3篇
植物保护   23篇
  2023年   2篇
  2022年   4篇
  2021年   10篇
  2020年   14篇
  2019年   19篇
  2018年   16篇
  2017年   8篇
  2016年   11篇
  2015年   12篇
  2014年   12篇
  2013年   13篇
  2012年   20篇
  2011年   29篇
  2010年   10篇
  2009年   8篇
  2008年   20篇
  2007年   18篇
  2006年   14篇
  2005年   16篇
  2004年   9篇
  2003年   6篇
  2002年   3篇
  2001年   3篇
  2000年   2篇
  1999年   5篇
  1998年   7篇
  1997年   2篇
  1995年   5篇
  1994年   1篇
  1991年   2篇
  1990年   1篇
  1987年   2篇
  1986年   2篇
  1985年   1篇
  1983年   2篇
  1982年   2篇
  1981年   1篇
  1980年   1篇
  1958年   1篇
排序方式: 共有314条查询结果,搜索用时 31 毫秒
291.
We studied the viability and infectiousness of aged Echinococcus granulosus eggs by in vivo evaluation in ovines. Our results demonstrated that after 41 months of ageing of the eggs under environmental conditions of an inferior arid climate (Patagonia, Argentina), they were still able to produce infection in 4/4 ovines challenged with 1200 eggs per ovine. In the ovines experimentally infected with these aged eggs, the occurrence of hepatic and pulmonary cysts was determined by necropsy, histologic and genetic studies. The eggs were found in a semi-senescent stage, thus keeping their capacity to generate an infection in the intermediary ovine host.  相似文献   
292.
Sixteen dogs in which canine leishmaniasis (CL) was diagnosed by positive identification of Leishmania amastigotes in bone marrow samples were treated with a mixture of amphotericin B (AmB) desoxycholate in soybean oil. To prevent the toxicity of AmB, dogs were pretreated with saline (50 mL/kg) and mannitol (2 g/kg). Dogs were treated twice weekly with an increasing dosage of amphotericin (0.8-2.5 mg/kg) for between 8 and 10 sessions. Transient adverse effects (anorexia, vomiting, or both) appeared in 81% of the dogs during therapy. At the end of the course, all dogs were clinically cured, with no parasites observed in bone marrow smears. Six of the 16 dogs (38%) were positive by polymerase chain reaction (PCR) in bone marrow samples at some stage of their follow-up, but only 2 were positive at the first test after treatment, which was performed within 5 months after the end of the therapy. The other 4 dogs were initially negative and became PCR-positive at subsequent examinations. Three of these 6 dogs also experienced a clinical relapse. Four dogs had at least 3 consecutive negative PCR tests during a minimum period of 18 months and were clinically cured. The results of the present study indicate that despite having a high initial effectiveness in the treatment of CL, relapses can occur with the described protocol. Also, a single negative PCR result in a recently treated dog cannot be interpreted as a complete cure.  相似文献   
293.
294.
The advanced very high resolution radiometer (AVHRR) is an operational, high-quality, crosstrack, line-scanning multispectral radiometer. Its data at 1.1 km maximum spatial resolution, 2800 km swath width and five spectral bands have widespread applications in meteorology, oceanography, climatology, agriculture, hydrology, forestry and many other disciplines. Two AVHRR are maintained in continuous operational mode, borne by two National Oceanic and Atmospheric Administration (NOAA) polar orbiting satellites. Particularly valuable is the fact that this operational system provides imagery of all parts of the globe at least four times daily, large portions of which are archived centrally in several data centers around the world. Historical data are available back to 1985.

As a remote sensing system, the NOAA/TIROS-N satellites are arguably one of the most successful and extensively used components of the US space program. Through the direct-broadcast system, environmental data from the AVHRR and other sensors have been made available around the world to properly equipped users of all nations. The data are broadcast in two modes, automatic picture transmission (APT, low-cost, low-resolution, two-channel data) and high resolution picture transmission (HRPT, full resolution, all channels and other sensor data).

The purpose of this paper is to briefly describe the system, outlining its limitations and capabilities, to help potential new users keep their expectations within realistic levels. There are five categories of limitations on the utility of the AVHRR data for Earth surface applications: (1) spatial resolution and its space-time variability; (2) atmospheric effects on measurements; (3) no in-flight calibration of visible and near-infrared sensors; (4) special problems with the mid-infrared sensor; (5) the wide spectral sensitivity bands of the data channels.  相似文献   

295.
296.
An indirect enzyme-linked immunosorbent assay (ELISA) was developed for differentiation of animals infected with foot-and-mouth disease virus (FMDV) from vaccinated animals. The test was based on a highly pure and concentrated preparation of recombinant 3AB1 protein obtained by expression in a prokaryotic system, protein separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and electro elution. Experimental- and field-serum samples from naive, vaccinated, and infected cattle were tested for anti3AB1 antibody using the ELISA. A cutoff level was set at 35% of the maximum absorbance obtained with a positive control serum (FMDV-infected animal, 21 days postinfection [dpi]). This assay could detect antibodies from sera of animals experimentally infected by contact (n = 118) with a sensitivity of 97.5%. The specificity was 100%, based on negative test results obtained on 109 sera from naive animals. Remarkably, all sera from animals vaccinated either once (n = 102) or twice (n = 30) were negative. In addition, this 3AB1-ELISA could detect seroconversion at 7 dpi in animals inoculated intradermolingually. This assay constitutes an important tool for the rapid detection of FMDV outbreaks in a vaccinated population. In addition, it presents a reliable, economical, and simple method for testing large numbers of serum samples.  相似文献   
297.
Tropical Animal Health and Production - The aim of the present study was to develop and evaluate an equation to predict body weight (BW) using hip width (HW) in Pelibuey ewe lambs and ewes. Five...  相似文献   
298.
299.
ObjectivesTo describe dye distribution and spinal nerve involvement after a simulated erector spinae plane (ESP) block performed on fresh equine cadavers.Study designExperimental cadaver study.AnimalsA group of 11 adult equine cadavers.MethodsThe spinal region surrounding the sixteenth thoracic vertebra (Th16) of one cadaver was removed and underwent magnetic resonance imaging. In 10 adult equine cadavers [body weight, 549 ± 58 kg (mean ± standard deviation)], 0.2 mL kg–1 of a 50:1 2% lidocaine/dye solution was injected bilaterally (n = 20 injections) into the fascial plane between the transverse process of Th16 and the erector spinae muscles. An in-plane ultrasound-guided technique with a convex transducer was used to guide injection. Dissection was performed immediately following injection. The craniocaudal and lateral extent of dye distribution was measured (cm) and the number of vertebral bodies involved were counted (n = 20). Abdominal and thoracic cavities as well as the epidural space were also examined for presence of dye (yes/no) (n = 20). Further dissection was performed to evaluate if staining of the dorsal and ventral rami of the spinal nerves and sympathetic chain occurred (n = 14).ResultsThe thoracolumbar fascia was stained in 17/20 (85%) injections and three injections terminated intramuscularly. Multisegmental staining of the dorsal rami was observed in the 14 injections in which staining was evaluated. Ventral rami staining was observed in 3/14 injections where staining was evaluated. Epidural migration was observed in 4/20 (20%) injections. No evidence of dye was found in the thoracic and abdominal cavities or on the sympathetic chain.Conclusions and clinical relevanceThe ESP block may prove beneficial to desensitize structures innervated by the dorsal rami of the thoracic spinal nerves. Further investigation is necessary to evaluate complications caused by epidural contamination.  相似文献   
300.
Tubers of 11 clones ofSolanum tuberosum subsp.andigena (andigena) and 12 cultivars ofS. tuberosum subsp.tuberosum (tuberosum) were inoculated with water suspensions (5.5 × 104 5.5 × 105, 5.5 × 106 CFU/ml) ofErwinia chrysanthemi. Tubers were inoculated immediately after harvest and after 6 and 16 wk of storage at 4 and 23°C. Tuber rot incidence in andigena and tuberosum increased as inoculum concentration increased. Based on tuber rot severity, clones of andigena were classified as resistant, intermediate, or susceptible and cultivars of tuberosum were classified as intermediate or susceptible. Rot severity increased in all tubers stored at 4°C and in tubers of tuberosum stored at 23°C; rot did not increase in tubers of andigena stored at 23°C. Electrolyte leakage (EL), total sugars (TS), reducing sugars (RS), non-reducing sugars (NRS) and dry matter (DM) were determined in non-inoculated tubers. There was a significant positive correlation between the rate of EL, concentration of RS and tuber rot in andigena and tuberosum. Tuber rot and DM were negatively correlated in tubers of andigena; but they were not correlated in tuberosum. Clones of andigena with low EL, TS, RS, and high DM were resistant to tuber rot, and the incidence of tuber rot in these clones was much less influenced by temperature and length of storage. The influence of temperature and length of storage on susceptibility toE. chrysanthemi may be explained by increased cell membrane permeability; increased leakage of accumulated sugars in potatoes stored at 4°C could favor bacterial proliferation resulting in more disease.  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