全文获取类型
收费全文 | 4942篇 |
免费 | 372篇 |
国内免费 | 4篇 |
专业分类
林业 | 84篇 |
农学 | 67篇 |
基础科学 | 14篇 |
277篇 | |
综合类 | 472篇 |
农作物 | 73篇 |
水产渔业 | 114篇 |
畜牧兽医 | 4046篇 |
园艺 | 41篇 |
植物保护 | 130篇 |
出版年
2023年 | 70篇 |
2021年 | 31篇 |
2020年 | 125篇 |
2019年 | 42篇 |
2018年 | 95篇 |
2017年 | 104篇 |
2016年 | 93篇 |
2015年 | 95篇 |
2014年 | 157篇 |
2013年 | 210篇 |
2012年 | 172篇 |
2011年 | 186篇 |
2010年 | 142篇 |
2009年 | 154篇 |
2008年 | 182篇 |
2007年 | 135篇 |
2006年 | 122篇 |
2005年 | 116篇 |
2004年 | 145篇 |
2003年 | 152篇 |
2002年 | 140篇 |
2001年 | 139篇 |
2000年 | 120篇 |
1999年 | 125篇 |
1998年 | 125篇 |
1997年 | 117篇 |
1996年 | 98篇 |
1995年 | 97篇 |
1994年 | 88篇 |
1993年 | 111篇 |
1992年 | 164篇 |
1991年 | 138篇 |
1990年 | 144篇 |
1989年 | 104篇 |
1988年 | 120篇 |
1987年 | 118篇 |
1986年 | 87篇 |
1985年 | 101篇 |
1984年 | 67篇 |
1983年 | 77篇 |
1982年 | 35篇 |
1979年 | 34篇 |
1977年 | 20篇 |
1976年 | 24篇 |
1975年 | 22篇 |
1973年 | 31篇 |
1972年 | 22篇 |
1971年 | 20篇 |
1969年 | 24篇 |
1967年 | 17篇 |
排序方式: 共有5318条查询结果,搜索用时 109 毫秒
911.
912.
913.
914.
da Cunha Karina Patrícia Vieira do Nascimento Clístenes Williams Araújo 《Water, air, and soil pollution》2009,199(1-4):323-341
Water, Air, & Soil Pollution - The southern sector of the Guadiana River basin (GRB) drains the central-western part of the Iberian Pyrite Belt, an area with many polymetallic sulfide deposits... 相似文献
915.
Ecological and hydrological models applied over regional domains generally require the input of spatial meteorological time series. We investigate the potential improvements to space–time regionalisations of sparse meteorological data sets when including information on temporal correlations between successive measurements of minimum temperature (Tmin), maximum temperature (Tmax) and precipitation (P) from 112 stations across Central Oregon. We compared a number of increasingly complex geostatistical models based on Kriging with a baseline inverse distance weighting algorithm. We varied the number of interpolation data used in both space and time and assessed the impact on interpolation skill. Furthermore, we assessed the error and bias reduction resulting from aggregating estimates over increasingly large temporal supports. We hypothesised that incorporating temporal information would decrease errors, and that error and bias would be reduced when considering estimates aggregated over longer time periods. We found that, contrary to our expectations, incorporation of information on temporal autocorrelation decreased interpolation skill by ~5% for Tmin and Tmax. However, inclusion of temporal autocorrelation improved results for P by ~10%. Increasing the temporal aggregation of estimates was shown to decrease error by up to 50% and bias by up to 30% (daily vs. annual support). These results indicate that instantaneous error may be diluted for phase lagged or integrating elements of the state vector, such as soil moisture, when implementing such surfaces in modelling applications. Results were more successful for temperature than precipitation (daily % error for jack-knife estimates of Tmin = 52, Tmax = 13, P = 97), reflecting the stochastic nature of precipitation, and problems with non-linearity for the Kriging algorithm. 相似文献
916.
Lisa J. Thompson DVM ; Ravi Seshadri DVM DACVECC DAVBP Marc R. Raffe DVM MS DACVA DACVECC 《Journal of Veterinary Emergency and Critical Care》2009,19(2):165-173
Objective – Describe clinical characteristics and outcomes associated with canine patients undergoing surgical intervention for treatment of acute pancreatitis.
Design – Retrospective outcome study from 2001 to 2007.
Animals – Thirty-seven dogs.
Interventions – None.
Measurements and Main Results – The following data were collected for dogs who underwent surgical intervention in the course of treatment for severe acute pancreatitis: preoperative clinicopathologic and physical data, ultrasonographic findings, surgical procedure detail, histopathologic findings, and transfusion requirements. The survival rate was 80.8% in dogs with extrahepatic biliary obstruction, 64.3% in dogs undergoing necrosectomy, and 40.6% with pancreatic abscess. Overall survival was 63.6%. Surgical complications included intraoperative and postoperative hemorrhage in 12 dogs, postoperative development of diabetes mellitus in 3 dogs, exocrine pancreatic insufficiency in 1 dog, and bacterial peritonitis in 2 dogs.
Conclusion – Surgical intervention and aggressive postoperative care may be pursued in select dogs with severe acute pancreatitis. In dogs with extrahepatic biliary obstruction secondary to acute pancreatitis, surgical intervention may be associated with a good prognosis whereas dogs with pancreatic abscess formation may have a more guarded prognosis. 相似文献
Design – Retrospective outcome study from 2001 to 2007.
Animals – Thirty-seven dogs.
Interventions – None.
Measurements and Main Results – The following data were collected for dogs who underwent surgical intervention in the course of treatment for severe acute pancreatitis: preoperative clinicopathologic and physical data, ultrasonographic findings, surgical procedure detail, histopathologic findings, and transfusion requirements. The survival rate was 80.8% in dogs with extrahepatic biliary obstruction, 64.3% in dogs undergoing necrosectomy, and 40.6% with pancreatic abscess. Overall survival was 63.6%. Surgical complications included intraoperative and postoperative hemorrhage in 12 dogs, postoperative development of diabetes mellitus in 3 dogs, exocrine pancreatic insufficiency in 1 dog, and bacterial peritonitis in 2 dogs.
Conclusion – Surgical intervention and aggressive postoperative care may be pursued in select dogs with severe acute pancreatitis. In dogs with extrahepatic biliary obstruction secondary to acute pancreatitis, surgical intervention may be associated with a good prognosis whereas dogs with pancreatic abscess formation may have a more guarded prognosis. 相似文献
917.
Lonny B. Pace DVM Richard S. Vetter MS 《Journal of Veterinary Emergency and Critical Care》2009,19(4):329-336
Objective – To provide a comprehensive review of relevant literature regarding the brown recluse spider (BRS) and to define those criteria that must be satisfied before making a diagnosis of brown recluse envenomation.
Etiology – The complex venom of the BRS contains sphingomyelinase D, which is capable of producing all the clinical signs in the human and some animal models.
Diagnosis – There is no current commercially available test. In humans there are many proposed guidelines to achieve a definitive diagnosis; however, there are no established guidelines for veterinary patients.
Therapy – Currently, no consensus exists for treatment of BRS envenomation other than supportive care, which includes rest, thorough cleaning of the site, ice, compression, and elevation.
Prognosis – Prognosis varies based on severity of clinical signs and response to supportive care. 相似文献
Etiology – The complex venom of the BRS contains sphingomyelinase D, which is capable of producing all the clinical signs in the human and some animal models.
Diagnosis – There is no current commercially available test. In humans there are many proposed guidelines to achieve a definitive diagnosis; however, there are no established guidelines for veterinary patients.
Therapy – Currently, no consensus exists for treatment of BRS envenomation other than supportive care, which includes rest, thorough cleaning of the site, ice, compression, and elevation.
Prognosis – Prognosis varies based on severity of clinical signs and response to supportive care. 相似文献
918.
Lynel J. Tocci DVM MTSBB Patty J. Ewing DVM MS DACVP 《Journal of Veterinary Emergency and Critical Care》2009,19(1):66-73
Objectives – To review the principles and available technology for pretransfusion testing in veterinary medicine and discuss the indications and importance of test performance before RBC transfusion.
Data Sources – Current human and veterinary medical literature: original research articles and scientific reviews.
Summary – Indications for RBC transfusion in veterinary medicine include severe anemia or tissue hypoxia resulting from blood loss, decreased erythrocyte production, and hemolyzing conditions such as immune-mediated anemia and neonatal isoerythrolysis. Proper blood sample collection, handling, and identification are imperative for high-quality pretransfusion testing. Point-of-care blood typing methods including both typing cards and rapid gel agglutination are readily available for some species. Following blood typing, crossmatching is performed on one or more donor units of appropriate blood type. As an alternative to technically demanding tube crossmatching methods, a point-of-care gel agglutination method has recently become available for use in dogs and cats. Crossmatching reduces the risk of hemolytic transfusion reactions but does not completely eliminate the risk of other types of transfusion reactions in veterinary patients, and for this reason, all transfusion reactions should be appropriately documented and investigated.
Conclusion – The administration of blood products is a resource-intensive function of veterinary medicine and optimizing patient safety in transfusion medicine is multifaceted. Adverse reactions can be life threatening. Appropriate donor screening and collection combined with pretransfusion testing decreases the occurrence of incompatible transfusion reactions. 相似文献
Data Sources – Current human and veterinary medical literature: original research articles and scientific reviews.
Summary – Indications for RBC transfusion in veterinary medicine include severe anemia or tissue hypoxia resulting from blood loss, decreased erythrocyte production, and hemolyzing conditions such as immune-mediated anemia and neonatal isoerythrolysis. Proper blood sample collection, handling, and identification are imperative for high-quality pretransfusion testing. Point-of-care blood typing methods including both typing cards and rapid gel agglutination are readily available for some species. Following blood typing, crossmatching is performed on one or more donor units of appropriate blood type. As an alternative to technically demanding tube crossmatching methods, a point-of-care gel agglutination method has recently become available for use in dogs and cats. Crossmatching reduces the risk of hemolytic transfusion reactions but does not completely eliminate the risk of other types of transfusion reactions in veterinary patients, and for this reason, all transfusion reactions should be appropriately documented and investigated.
Conclusion – The administration of blood products is a resource-intensive function of veterinary medicine and optimizing patient safety in transfusion medicine is multifaceted. Adverse reactions can be life threatening. Appropriate donor screening and collection combined with pretransfusion testing decreases the occurrence of incompatible transfusion reactions. 相似文献
919.
Piedad N Henao‐Guerrero DVM MS Diplomate ACVA Rose McMurphy DVM Diplomate ACVA ACVECC Butch KuKanich DVM PhD Diplomate ACVCP Dave S Hodgson DVM Diplomate ACVA 《Veterinary anaesthesia and analgesia》2009,36(2):133-143
ObjectiveTo assess the effect of morphine on the bispectral index (BIS) in dogs during isoflurane anesthesia maintained at a constant end–tidal concentration.Study designProspective, randomized, experimental trial.AnimalsEight adult Beagle dogs, weighing between 7.1 and 9.8 kg.MethodsAnesthesia was induced with isoflurane via a face mask. Dog's tracheas were intubated and anesthesia maintained with isoflurane at a constant end–tidal concentration (e′Iso) of 1.81% for a 30–minute equilibration period. Pulmonary ventilation was controlled to normocapnia. After equilibration, baseline values were recorded prior to intravenous administration of morphine sulfate (0.5 mg kg?1) (MT) or an equal volume of saline (CT). Measurements for heart rate, systolic, diastolic and mean arterial pressure (SAP, DAP and MAP) were recorded at 10, 20, 30, 45, 60, 75, 90, 105 and 120 minutes after treatment. Bispectral index was recorded every 10 seconds for 3 minutes for each time measurement. Venous blood samples were collected at baseline, 10, 20, 30, 45, 60 and 120 minutes for determination of morphine serum concentrations. Anesthesia was discontinued after the last measurement and dogs were allowed to recover.ResultsBaseline BIS for MT and CT at 1.81%e′Iso were 63 ± 10 and 58 ± 9, respectively. Bispectral index in MT was 4–8% lower at 20, 75, 90 and 105 minutes compared with CT. There were no differences in BIS between baseline and any subsequent measurement within either MT or CT. Heart rate, SAP, MAP, and DAP decreased after morphine administration.Conclusion and clinical relevanceIntravenous administration of 0.5 mg kg?1 morphine sulfate did not cause clinically significant changes in the BIS of unstimulated dogs during isoflurane anesthesia at an e′Iso of 1.81%. 相似文献
920.
Mohammad Reza Seddighi DVM MS PhD Christine M Egger DVM MVSc Diplomate ACVA Barton W Rohrbach† VMD MPH Diplomate ACVPM Sherry K Cox† PhD & Thomas J Doherty‡ MVB MSc & Diplomate ACVA 《Veterinary anaesthesia and analgesia》2009,36(4):334-340
ObjectiveTo evaluate the effect of tramadol on sevoflurane minimum alveolar concentration (MACSEVO) in dogs. It was hypothesized that tramadol would dose-dependently decrease MACSEVO.Study designRandomized crossover experimental study.AnimalsSix healthy, adult female mixed-breed dogs (24.2 ± 2.6 kg).MethodsEach dog was studied on two occasions with a 7-day washout period. Anesthesia was induced using sevoflurane delivered via a mask. Baseline MAC (MACB) was determined starting 45 minutes after tracheal intubation. A noxious stimulus (50 V, 50 Hz, 10 ms) was applied subcutaneously over the mid-humeral area. If purposeful movement occurred, the end-tidal sevoflurane was increased by 0.1%; otherwise, it was decreased by 0.1%, and the stimulus was re-applied after a 20-minute equilibration. After MACB determination, dogs randomly received a tramadol loading dose of either 1.5 mg kg?1 followed by a continuous rate infusion (CRI) of 1.3 mg kg?1 hour?1 (T1) or 3 mg kg?1 followed by a 2.6 mg kg?1 hour?1 CRI (T2). Post-treatment MAC determination (MACT) began 45 minutes after starting the CRI. Data were analyzed using a mixed model anova to determine the effect of treatment on percentage change in baseline MACSEVO (p < 0.05).ResultsThe MACB values were 1.80 ± 0.3 and 1.75 ± 0.2 for T1 and T2, respectively, and did not differ significantly. MACT decreased by 26 ± 8% for T1 and 36 ± 12% for T2. However, there was no statistically significant difference in the decrease between the two treatments.Conclusion and clinical relevanceTramadol significantly reduced MACSEVO but this was not dose dependent at the doses studied. 相似文献