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   87篇
  免费   7篇
林业   2篇
  4篇
综合类   28篇
农作物   3篇
畜牧兽医   51篇
植物保护   6篇
  2020年   2篇
  2019年   1篇
  2018年   3篇
  2017年   4篇
  2015年   2篇
  2014年   5篇
  2013年   1篇
  2009年   4篇
  2008年   6篇
  2007年   5篇
  2005年   1篇
  2004年   1篇
  2003年   3篇
  2002年   3篇
  2000年   4篇
  1999年   5篇
  1998年   3篇
  1997年   2篇
  1996年   3篇
  1995年   3篇
  1992年   1篇
  1991年   1篇
  1988年   1篇
  1987年   1篇
  1986年   1篇
  1985年   2篇
  1984年   1篇
  1983年   3篇
  1982年   1篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1972年   1篇
  1970年   1篇
  1969年   2篇
  1968年   2篇
  1958年   1篇
  1955年   1篇
  1920年   1篇
  1916年   1篇
  1915年   1篇
  1914年   2篇
  1908年   1篇
  1907年   1篇
  1906年   1篇
  1904年   1篇
  1897年   1篇
排序方式: 共有94条查询结果,搜索用时 3 毫秒
1.
OBJECTIVE: To validate a new food-frequency questionnaire (FFQ) for measuring the intake of fruit, vegetables and tea reported by women participating in the Norwegian Mother and Child Cohort Study (MoBa). DESIGN: Intake of fruits, vegetables and tea estimated by the FFQ was compared with urinary flavonoid excretion, plasma carotenoid concentration and intake measured by a 4-day weighed food diary (FD). The triangular method was applied to calculate FFQ validity coefficients using two independent biomarkers. SETTING AND SUBJECTS: One hundred and nineteen women participating in MoBa. RESULTS: The FFQ estimate of fruit intake was significantly correlated with urine phloretin (r = 0.33), citrus fruit/juice with urine hesperetin (r = 0.44), cooked vegetables with plasma alpha-carotene (r = 0.37), and tea with urine kaempferol (r = 0.41) (P < 0.01 for all). On average, 60% of the participants fell into the same or adjacent quintiles when classified by FFQ and biomarkers. Significant correlations between the FFQ and FD were found for fruit (r = 0.39), vegetables (r = 0.34), juices (r = 0.50) and tea (r = 0.53). The FFQ validity coefficient was 0.65 for citrus fruit/juice and 0.59 for cooked vegetables as calculated by the triangular method. CONCLUSIONS: The validation study shows that the MoBa FFQ can be used to estimate fruit, juice, vegetable and tea intake in pregnant Norwegian women, and to rank individuals within the distribution.  相似文献   
2.
2008年上半年,我国的白羽肉鸡市场还是国外引进品种一统天下。在引种数量上,全国共有9家企业先后从国外引进祖代肉种鸡34.16万套。在品种方面,爱拔益加(AA+)的市场份额仍然保持第一,达到50.1%,罗斯308(Ross)和科宝(Cobb)分别占据第二和第三位,市场份额分别占到31.0%和18.9%。  相似文献   
3.
Serum cortisol response was assessed in 8 captive cheetahs, of varying ages, after the intravenous administration of 500 microg of tetracosactide (Synacthen Depot, Novartis, Kempton Park) while maintained under general anaesthesia. In addition, 8 cheetahs were anaesthetised and given an equal volume of saline in order to establish baseline cortisol concentrations at similar stages of anaesthesia. A significant difference in the median cortisol concentration measured over time was found following ACTH administration in the ACTH group (P < 0.001). There was no difference between the median cortisol concentrations in the ACTH group at time-points 120, 150 and 180 min after ACTH stimulation (P = 0.867). Thus it appears appropriate to collect serum 120 to 180 min after tetracosactide administration to assess maximal stimulation of the adrenal in the cheetah. No statistically significant rise was seen in the anaesthetised control group following the injection of saline (P = 0.238).  相似文献   
4.
5.
An estimated 300,000 cases of Lyme disease occur in the United States annually. Disseminated Lyme disease may result in carditis, arthritis, facial palsy or meningitis, sometimes requiring hospitalization. We describe the epidemiology and cost of Lyme disease‐related hospitalizations. We analysed 2005–2014 data from the Truven Health Analytics MarketScan Commercial Claims and Encounters Databases to identify inpatient records associated with Lyme disease based on International Classification of Diseases, Ninth Revision, Clinical Modification (ICD‐9‐CM) codes. We estimated the annual number and median cost of Lyme disease‐related hospitalizations in the United States in persons under 65 years of age. Costs were adjusted to reflect 2016 dollars. Of 20,983,165 admission records contained in the inpatient databases during the study period, 2,823 (0.01%) met inclusion criteria for Lyme disease‐related hospitalizations. Over half of the identified records contained an ICD‐9‐CM code for meningitis (n = 614), carditis (n = 429), facial palsy (n = 400) or arthritis (n = 377). Nearly 60% of hospitalized patients were male. The median cost per Lyme disease‐related hospitalization was $11,688 (range: $140–$323,613). The manifestation with the highest median cost per stay was carditis ($17,461), followed by meningitis ($15,177), arthritis ($13,012) and facial palsy ($10,491). Median cost was highest among the 15‐ to 19‐year‐old age group ($12,991). Admissions occurring in January had the highest median cost ($13,777) for all study years. Based on extrapolation to the U.S. population, we estimate that 2,196 Lyme disease‐related hospitalizations in persons under 65 years of age occur annually with an estimated annual cost of $25,826,237. Lyme disease is usually treated in an outpatient setting; however, some patients with Lyme disease require hospitalization, underscoring the need for effective prevention methods to mitigate these serious cases. Information from this analysis can aid economic evaluations of interventions that prevent infection and advances in disease detection.  相似文献   
6.
The objective was to study the use of ultrasound as a complementary test in the breeding soundness evaluation in male pigs and study the pattern of echogenicity of the testicular parenchyma in boars of different racial groups. Twenty‐six adult boars from four different racial groups were used, 10 from the Piau breed (group 1), four from the commercial and finishing group (group 2), six Pietrain breed (group 3) and six from the Duroc breed (group 4). All animals were evaluated for breeding soundness evaluation and the ultrasound examination of the testicles. The groups of animals that were evaluated showed no difference in the main semen parameters that were evaluated, except for the sperm volume, concentration of the ejaculated sperm and the supravital staining; the lowest figures were for the animals from the Piau breed (group 1). In relation to the testicular biometrics, Duroc animals (group 4) had a greater scrotal width compared to the other groups. But when we assessed the intensity of pixels of the testicles, there was a difference between groups. The groups 2 (finishing animals), 3 (Pietrain) and 4 had no difference between themselves. Group 3 had greater pixel intensity in relation to group 1. Of the 26 animals studied, five showed an abnormality during ultrasound evaluation, like hydrocele, hyperechoic mass in the testicular parenchyma, cyst in the head of the epididymis and the presence of fluid in the head and tail of the epididymis. The various animal groups studied did not differ in the principal reproductive parameters evaluated, showing that despite the great variability of reproductive traits between breeds and within the same breed, the breeding soundness evaluation, the more complete it is, is essential for the selection of breeders and the ultrasonography of the reproductive system becomes an important addition in this examination.  相似文献   
7.
ObjectiveTo measure the extradural pressures in goats before and after extradural injection, and to investigate the occurrence of extradural pressure waves.Study designProspective experimental trial.AnimalsNine healthy adult goats weighing 59.4 ± 6.4 kg, scheduled for stifle arthroscopy.MethodsThe goats were pre–medicated with midazolam and anaesthesia was induced with propofol and maintained with sevoflurane. The goats were placed in lateral recumbency and extradural puncture was performed via the lumbosacral space. Correct placement of the needle was assessed by lack of resistance to the injection of saline. The needle was connected to an electronic pressure transducer to record extradural pressure. Measurements were taken before and after extradural injection of methadone (0.1 mg kg?1, diluted to a total volume of 0.2 mL kg?1) and 10 minutes later. Contrast medium was injected and correct extradural needle placement confirmed by radiography.ResultsLack of resistance to injection of saline occurred in all goats, but there were no pressure waves observed before injection in any animal. Radiography indicated incorrect needle placement in four animals and one had pressure waves synchronous with the arterial pulse after methadone injection. Correct needle placement was confirmed in the remaining five animals which exhibited pressure waves after extradural methadone injection. In the five goats with successful needle placement the baseline extradural pressure ranged from 0.4 to 2.5 kPa (3–19 mmHg), increasing to 4.4–39.9 kPa (33–300 mmHg) after injection. Ten minutes after injection, extradural pressure remained elevated and ranged from 2.5 to 17.3 kPa (19–130 mmHg).Conclusions and clinical relevanceExtradural pressure waves were not useful to confirm correct extradural needle placement in laterally recumbent goats. The presence of such waves after injection of 0.2 mL kg?1 may be indicative of correct placement but even here we saw one of nine animals with extradural pressure waves where we failed to confirm correct needle placement. Extradural pressure increases after extradural injection.  相似文献   
8.
The compounds referred to in the title have been investigated for fungicidal, insecticidal and acaricidal activities in laboratory and greenhouse tests. Several representatives of this class of compounds were active against powdery mildew on apple, cucumber, and barley, and against aphids and spider mites, both when applied to the leaves and when added to the nutrient solutions of test plants. Treatment of leaf halves resulted in protection of the entire leaves. A striking difference in pesticidal activity was observed between two series of isomers. Representatives of the series with the phosphoryl group in the 1-position showed much greater pesticidal activities than their corresponding isomers with the phosphoryl group in the 2-position. The optimum activity within the two homologous series (R-H, CH3 ... C6H13) was determined: generally the lower homologues (R-H, CH3, C2H5 and i-C3H7) showed the greatest pesticidal activity in the systemic tests. After leaf-application the influence of the length of R was less pronounced or even reversed.Samenvatting De in de titel genoemde stoffen zijn onderzocht op fungicide, insecticide en acaricide werking in laboratorium en kasproeven. Verscheidene vertegenwoordigers van dit type verbindingen waren werkzaam tegen echte meeldauw van appel, komkommer en gerst, en tegen bladluizen en spint, dit zowel na toepassing op de bladeren als na toevoeging aan de voedingsoplossingen van proefplanten. Behandeling van bladhelften resulteerde in bescherming van de gehele bladeren. Een opvallend verschil werd waargenomen tussen de werking van twee reeksen isomeren. Vertegenwoordigers van de reeks met de fosforylgroep op de 1-plaats waren veel werkzamer dan hun isomeren met de fosforylgroep op de 2-plaats. Het optimum binnen de twee homologe reeksen (R-H, CH3 ... C6H13) werd bepaald: in het algemeen waren de lagere homologen (R-H, CH3; C2H5 en i-C3H7) het werkzaamst in de systemische proeven. Na een preventieve bladbespuiting was de invloed van de lengte van R minder uitgesproken of zelfs omgekeerd.  相似文献   
9.
1. Mule ducks were produced by naturally mating Muscovy drakes and Khaki Campbell ducks. 2. Semen was collected from 6-month-old mule drakes via an artificial vagina. The fluid was clear without any spermatozoa or spermatids. 3. Testes from 27-week-old mule drakes were smaller in size than those of Khaki Campbell drakes but heavier than Muscovy males of the same age. Histological sections of these testes revealed that spermatogenesis was not complete. 4. Testosterone concentration in the mule drakes was higher than in Muscovy males but similar to Khaki Campbell drakes. 5. Mule drakes have strong sexual drives as a result of high concentrations of testosterone, but, because spermatogenesis is incomplete, their semen had no sperm.  相似文献   
10.
We present a simple model of the dynamics of heartwater that we use to explore and better understand various aspects of this disease. We adapted the Ross-Macdonald model for malaria epidemiology so that we could consider both host and vector populations, and evaluate the interactions between the two. We then use two more biologically detailed models to examine heartwater epidemiology. The first includes a carrier state and host mortality, and the second includes density dependence. The results from all three models indicate that a stable equilibrium with high disease levels is probably the standard situation for heartwater (R0 between 5.7 and 22.4). More than 80% of cattle become infected with heartwater if only 12% of infected tick bites produce an infection in cattle, if tick burdens are as low as only five ticks per host per day, or if tick lifespans are as short as 7 d. A host recovery rate of 30 d results in over 50% of the cattle becoming infected with heartwater. Our analyses indicate that it is quite difficult to prevent the establishment and maintenance of high levels of heartwater in a herd, thereby supporting previous suggestions that any attempts at controlling this disease through stringent tick control regimens are not warranted.  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