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   410篇
  免费   22篇
林业   51篇
农学   3篇
基础科学   1篇
  83篇
综合类   29篇
农作物   25篇
水产渔业   18篇
畜牧兽医   191篇
园艺   7篇
植物保护   24篇
  2023年   4篇
  2022年   9篇
  2021年   15篇
  2020年   13篇
  2019年   15篇
  2018年   12篇
  2017年   20篇
  2016年   16篇
  2015年   13篇
  2014年   16篇
  2013年   12篇
  2012年   30篇
  2011年   35篇
  2010年   21篇
  2009年   20篇
  2008年   23篇
  2007年   26篇
  2006年   21篇
  2005年   14篇
  2004年   12篇
  2003年   8篇
  2002年   9篇
  2001年   5篇
  2000年   4篇
  1999年   3篇
  1998年   3篇
  1996年   3篇
  1995年   2篇
  1993年   3篇
  1991年   2篇
  1989年   3篇
  1987年   4篇
  1981年   1篇
  1977年   1篇
  1976年   1篇
  1972年   1篇
  1969年   1篇
  1957年   1篇
  1947年   1篇
  1945年   2篇
  1941年   1篇
  1940年   1篇
  1938年   1篇
  1936年   1篇
  1934年   5篇
  1933年   3篇
  1932年   1篇
  1930年   3篇
  1929年   3篇
  1922年   1篇
排序方式: 共有432条查询结果,搜索用时 15 毫秒
401.
Clinical, ultrasonographic, radiographic and pathological findings of a chondrosarcoma diagnosed in an 8-year-old Simmental cow are reported. The primary site was located in the cartilage of the right scapula at the angulus cranialis. The tumour had already spread to the lungs at the time of diagnosis. This is the first report of a bovine scapula chondrosarcoma.  相似文献   
402.
OBJECTIVE: To evaluate the neuromuscular blocking and chronotropic effects of rocuronium bromide in cats anaesthetized for surgery. STUDY DESIGN: Prospective clinical trial. ANIMALS: Twenty-two healthy cats of mixed breed presented for ovariectomy (n = 13) or castration (n = 9). Mean body mass (+/-SD) was 3.6 +/- 0.65 kg and mean age was 10.25 +/- 2.63 months. METHODS: Anaesthesia was induced with intravenous (IV) midazolam (0.3 mg kg(-1)), ketamine (3 mg kg(-1)) and butorphanol (0.4 mg kg(-1)). Tracheal intubation was performed and anaesthesia was maintained with isoflurane delivered in 100% oxygen. Neuromuscular function was monitored using acceleromyography applied at the ulnar nerve. This was stimulated by using the train-of-four (TOF) stimulus pattern (2 Hz) delivered every 15 seconds. The first train was made to establish baseline values for the first twitch (T1) and the TOF-ratio (T4:T1). Rocuronium (0.6 mg kg(-1) IV) was given and the following periods were recorded beginning at the end of injection: (1) lag time (LT) - to the first signs of T1 depression; (2) onset time (OT) - to the total ablation of T1; (3) duration of action (T1(25)) - to 25% recovery of the baseline value for T1; (4) T1(50)- to 50% baseline T1 restoration; (5) to TOF-ratios of 0.7 and 0.9. The time taken for T1 to recover from 75% to 25% depression (T1(25-75)) was also recorded. Heart rate (HR) was taken every minute for 15 minutes, beginning 5 minutes before rocuronium was injected. RESULTS: Rocuronium (0.6 mg kg(-1)) had a mean LT of 15.0 +/- 0 seconds, OT of 46 +/- 11 seconds and T1(25) of 13.2 +/- 2.7 minutes. The mean time for TOF 0.7 and 0.9 was 17.3 +/- 5.4 and 20.7 +/- 5.4 minutes respectively. The mean T1(25-75) was 4.8 +/- 2.4 minutes. No significant changes in HR were observed at any of the time intervals recorded. CONCLUSION: Rocuronium is an effective nondepolarizing muscle relaxant in the cat under the clinical conditions of this study. It has a rapid onset, a short duration of action and did not cause significant changes in HR.  相似文献   
403.
Objective— To describe anesthetic management of endoscopic electrosurgical removal of a bronchial carcinoma, partially blocking the right main stem bronchus in a Cocker Spaniel.
Study Design— Clinical case report.
Animals— Dog with a bronchial carcinoma.
Methods— To allow sufficient space for the endoscope and to avoid an oxygen-rich gas mixture in the trachea, which carries the risk of an airway fire when electrocautery is used, a 1 lumen endobronchial tube (EBT) was inserted into the left main stem bronchus. One-lung ventilation (OLV) started with a volume-controlled ventilator was switched to pressure-controlled ventilation in combination with positive end-expiratory pressure (PEEP).
Results— Resection of the bronchial carcinoma was successful. The dog was hypercapnic throughout the procedure and a high alveolar-arterial oxygen gradient was measured.
Conclusion— An EBT may be a feasible and safe option to provide OLV for bronchoscopic electrocautery with a closed thoracic cavity in dogs.
Clinical Relevance— EBT intubation for OLV should be considered as part of the anesthetic management of airway diseases treated with bronchoscopic electrocautery.  相似文献   
404.

Objective

To describe the cardiorespiratory effects of a change in table position in anaesthetized horses.

Study design

Prospective, crossover, randomized, experimental study.

Animals

Six adult horses (mean body weight 621 ± 59 kg, aged 13 ± 4 years).

Methods

The horses were anaesthetized twice in dorsal recumbency. They were either placed in the Trendelenburg position (head down; HD) followed by reverse Trendelenburg position (head up; HU) or in reverse order. Every position was maintained for 90 minutes. The order of positions was randomly assigned at initial anaesthesia. Extensive cardiorespiratory monitoring was performed. Statistical analysis consisted of a mixed model with horses as random effect and time, position, section of anaesthesia and interaction between those as fixed effects (p < 0.05).

Results

When HU was applied during the first section of anaesthesia, PaO2, (p = 0.012), oxygen saturation (SaO2, p < 0.01) and oxygen content (CaO2, p < 0.01) were significantly higher, while venous admixture (Q˙s/Q˙t, p < 0.01), mean arterial (p = 0.039), right atrial (p < 0.01) and mean pulmonary arterial pressure (p < 0.01) were lower than in HD. After changing from HU to HD, PaO2 and SaO2 remained higher and Q˙s/Q˙t lower compared to the inverse order. Independent of the order, in the HD position Q˙s/Q˙t (p = 0.019) increased while PaO2 (p < 0.01), SaO2 (p = 0.011), CaO2 (p < 0.01), venous PO2 (Pv¯O2; p = 0.019), venous saturation (p = 0.004) and venous oxygen content (p = 0.010) decreased over time. No significant differences were found for cardiac output, oxygen delivery, oxygen consumption and dobutamine requirement between the two positions.

Conclusions and clinical relevance

Gas exchange is better preserved in HU compared to HD, especially if applied from the start of the anaesthesia.  相似文献   
405.
Stillbirth and neonatal mortality are substantial problems in captive bottlenose dolphins (Tursiops truncatus). The cause of these problems often is unknown. We report a case of Escherichia coli septicemia in a male 3-day-old bottlenose dolphin calf. Lesions included omphalitis, synovitis, and hepatic necrosis associated with the presence of Gram-negative bacilli. E. coli was isolated in pure culture from multiple organs. A serum gammaglobulin level of 1.5 g/L indicated a lack of maternally acquired immunity. The observed failure to nurse may have resulted from brain injury due to perinatal asphyxia. Evidence for perinatal asphyxia was the diffuse presence of a moderate amount of meconium in the lungs.  相似文献   
406.
  1. Freshwater mussels (Order Unionida) are highly threatened. Interspecific competition for food sources with invasive alien species is considered to be one of the factors responsible for their decline because successful invaders are expected to have wider trophic niches and more flexible feeding strategies than their native counterparts.
  2. In this study, carbon (δ13C: 13C/12C) and nitrogen (δ15N: 15N/14N) stable isotopes were used to investigate the trophic niche overlap between the native freshwater mussel species, Anodonta anatina, Potomida littoralis, and Unio delphinus, and the invasive bivalve Corbicula fluminea living in sympatry in the Tua basin (south-west Europe).
  3. The species presenting the widest trophic niches were C. fluminea and A. anatina, which indicate that they have broader diets than U. delphinus and P. littoralis. Nonetheless, all the species assimilated microphytobenthos, sediment organic matter, and detritus derived from vascular plants, although with interspecific variability in the assimilated proportions of each source. The trophic niche of the invasive species overlapped with the trophic niche of all the native species, with the extent varying between sites and according to the species.
  4. From the three native species analysed, Potomida littoralis may be at a higher risk for competition for food with C. fluminea in the Tua basin, if food sources become limited, because this native mussel presented the narrowest trophic niche across sites and the highest probability of overlapping with the trophic niche of C. fluminea.
  5. Given the global widespread distribution of C. fluminea, the implementation of management measures devoted to the control or even eradication of this invasive alien species should be a conservation priority given its potential for competition with highly threatened native freshwater mussels.
  相似文献   
407.
An improvement in the procedure for investigation of organic acids and a new derivatization method, amenable to gas chromatographic-mass spectrometric detection of alcohols, are presented. The latter is based on the formation of phenacetyl esters. The simultaneous application of the two methods also allows data to be obtained on some volatile neutrals present in complex natural aqueous fluids. Application to wine and cider vinegars allowed detection of a number of previously unreported components, among which are interesting partially esterified polycarboxylic esters.  相似文献   
408.
Anatomical variations can be frequently found in the lymphatic system, which is also true for the shape and course of the thoracic duct (ductus thoracicus), the biggest lymph vessel in the body. From 2012 to 2019, the thoracic duct was successfully dissected in 43 dog carcasses that were used in the anatomy course at the Faculty of Veterinary Medicine, University of Zagreb. The thoracic duct originated from the cranial border of the cisterna chyli as one lymph vessel in 36 dogs (83.7%), as two vessels in six dogs (14%) and as three vessels in one dog (2.3%). We divided the observed thoracic duct variations into six groups according to their anatomical similarities. Considering the specific embryonic development, we can conclude that all observed variations are the result of minor deviations from the standard ontogenesis. However, the importance of thoracic duct variations is significant in surgical procedures done in the thoracic cavity to prevent or cure the chylothorax. Since this research showed variations in 39 out of 43 dogs (90.7%) throughout the whole course of the thoracic duct, great care must be taken while performing the ligation or embolization of the thoracic duct.  相似文献   
409.
ObjectiveTo measure the dead space of various syringe volumes and brands and a range of needles gauges commonly used in clinical practice, and to compare the results to the International Organization for Standardization (ISO) standard 7886-1:2018.Study designProspective observational study.MethodsSyringes of five brands and seven volumes: 1, 2.5, 5, 10, 20, 30, and 60 mL, 10 of each, 10 1 mL low dead space syringes and 10 23, 21 and 18 gauge needles were analysed. Syringe dead space was estimated by weighing each syringe, drawing up and expelling its rated volume of water for injection and re-weighing the syringe. The difference in mass between the two measurements was calculated and converted to a volume based on the density of water. The dead space of the needles was estimated using a similar technique: each needle was attached to a 1 mL syringe of known dead space. A Mettler electronic balance was used for the measurements. Mean dead space was calculated for each syringe volume and needle gauge. Data were compared to the ISO standard.ResultsSyringe dead space for 1 and 2.5 mL was less than 0.07 mL. For 5 mL syringes four of five brands, and for 10 mL syringes one of five brands failed to comply with the ISO; the dead space was greater than 0.075 and 0.1 mL, respectively. For the 20, 30, 60 mL syringes the dead space was less than 0.2 mL. Needle dead space was 0.05 mL for 23 and 21 gauge, and 0.07 mL for 18 gauge, similar in order of magnitude to syringe dead space.ConclusionsThe dead space of syringes differs between brands, and some do not meet the ISO standard. When calculating the amount of drug lost due to dead space, both that of the syringe and needle used should be considered.  相似文献   
410.
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