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   437篇
  免费   20篇
林业   97篇
农学   9篇
基础科学   1篇
  64篇
综合类   37篇
农作物   9篇
水产渔业   10篇
畜牧兽医   217篇
园艺   3篇
植物保护   10篇
  2019年   5篇
  2018年   7篇
  2017年   4篇
  2016年   8篇
  2015年   4篇
  2014年   9篇
  2013年   24篇
  2012年   13篇
  2011年   22篇
  2010年   10篇
  2009年   8篇
  2008年   17篇
  2007年   22篇
  2006年   11篇
  2005年   15篇
  2004年   27篇
  2003年   17篇
  2002年   17篇
  2001年   11篇
  2000年   9篇
  1999年   5篇
  1998年   4篇
  1997年   9篇
  1996年   5篇
  1995年   4篇
  1992年   5篇
  1991年   5篇
  1990年   7篇
  1989年   7篇
  1988年   7篇
  1987年   7篇
  1986年   7篇
  1983年   3篇
  1981年   4篇
  1980年   3篇
  1979年   3篇
  1978年   3篇
  1976年   3篇
  1972年   4篇
  1971年   11篇
  1970年   6篇
  1969年   4篇
  1967年   4篇
  1966年   4篇
  1965年   6篇
  1961年   3篇
  1960年   4篇
  1956年   3篇
  1932年   4篇
  1911年   6篇
排序方式: 共有457条查询结果,搜索用时 78 毫秒
121.
Background: As veterinary medicine has become more sophisticated, with greater numbers of veterinary patients receiving intensive care, more patients with an acute respiratory distress (ARDS)‐like syndrome have been recognized. Methods: A consensus definition meeting was held for the purpose of developing veterinary‐specific definitions for acute lung injury (ALI) and ARDS. Results/conclusions: Three clinically based definitions for acute lung injury and acute respiratory distress‐like syndromes occurring in veterinary patients were described. Neonatal equine respiratory distress syndrome (NERDS) was defined separately due to the specific requirement for primary developmental surfactant dysfunction and lack of an inflammatory component. Five diagnostic criteria categories were established for Veterinary ALI/ARDS (Vet ALI/ARDS) with 4 required and a fifth highly recommended criteria. A strong consensus was reached that onset of respiratory distress must have been acute and that known risk factors must be present. Additional criteria included evidence of pulmonary capillary leak with no evidence of increased pulmonary capillary pressure, evidence of inefficient gas exchange and, finally, evidence of inflammation. Some features of ALI/ARDS in the neonatal horse were recognized as unique, therefore, equine neonatal ALI/ARDS (EqNALI/EqNARDS) was similarly defined but with a graded gas exchange inefficiency table to allow for normal developmental changes in gas exchange. Use of these definitions in planning prospective studies of these problems in veterinary patients should allow for more direct comparisons of studies and clinical trials, with a larger goal of improving outcome in veterinary patients.  相似文献   
122.
Objective: To describe and compare the patient population, treatment, and outcome in dogs with septic peritonitis from 2 time periods at the same institution. Design: Retrospective study. Setting: The Matthew J. Ryan Veterinary Hospital at the University of Pennsylvania. Animals: Dogs treated surgically for septic peritonitis between 1988–1993 and 1999–2003. Interventions: None. Measurements: Preoperative physical and clinicopathologic data, surgical findings, anesthetic parameters, treatment, and outcome. Main results: No significant difference in survival among dogs treated surgically for septic peritonitis between 1988 and 1993 (21/33 [64%]) and 1999–2003 (29/51 [57%]) was detected. The patient populations of the two time periods were similar. Changes in treatment between the study periods reflected availability of new antibiotics and synthetic colloids, as well as greater attention to pain management and ulcer prevention. Duration of hospitalization was not significantly different between the two time periods, but the daily cost adjusted to 2005 dollars was higher in 1999–2003. Potential prognostic indicators were compared between survivors and non‐survivors after combining the data from both time periods, and although several parameters reached statistical significance, of greatest clinical significance were the higher blood pressure and preoperative serum albumin in survivors. Conclusions: Although new treatments were added to the supportive care of dogs with septic peritonitis, survival did not change sufficiently to detect a significant difference between the time periods evaluated. Identifying reliable prognostic indicators for septic peritonitis remains a challenge, but hypotension and decreased preoperative serum albumin were associated with non‐survival in this group of dogs.  相似文献   
123.
In a prospective study we compared the EEG variables total amplitude (TA), 80% spectral edge frequency (SEF-80), the ratio of fractional amplitudes distributed into the BETA and DELTA frequency band (BETA/DELTA-ratio), and differences in arteriovenous oxygen content (AVD02), obtained from horses anaesthetized with either halothane (H; n=4) or isoflurane (I; n=4) in oxygen. All horses underwent orthopaedic procedures. After premedication with xylazine (0.88 mg/kg IV), anaesthesia was induced with diazepam (0.033 mg/kg IV) and ketamine (2.2 mg/kg IV). During anaesthesia horses were ventilated using IPPV. EEG variables and AVD02 were recorded at equal levels of surgical anaesthesia (stage III/1–2), as determined by clinical signs and a dominant delta activity in the EEG power spectrum. PaC02was kept between 35 mmHg and 45 mmHg, PaO2above 100 mmHg, and mean arterial blood pressure (MAP) was adjusted to at least 80 mmHg. The average body temperature was 35.4 ± 1.1°C (H) and 35.6 ± 0.7°C (I), respectively. In horses anaesthetized with I, TA was significantly higher (P<01) (I: 3533 ± 70 γV; H: 235.9 ± 63.4 γV), whereas SEF-80 (I: 10.7 ± 0.7 Hz; H: 12.4 ± 0.7 Hz) and BETA/DELTA-ratio (I: 035 ± 0.06; H: 0.53 ± 0.12) were significantly lower (P<01) compared with H. We also observed significantly lower (P<05) AVD02 values with I (1.5 ± 0.5 Vol%) than with H (2.0 ± 1.2 Vol%). Since a depression in cerebral activity during anaesthesia is characterized by a decrease in EEG frequency content and a concomitant increase in EEG amplitude, the authors conclude that at equal levels of surgical anaesthesia, isoflurane exerts a more pronounced depression in cerebral electrical and metabolic activity in horses.  相似文献   
124.
125.
126.
127.
Zusammenfassung In Fortsetzung früherer Untersuchungen wurden weitere 104 Pflanzenarten aus 24 Familien der einheimischen Flora und des Gaterslebener Sortiments nach einem Standardverfahren orientierend auf vorkommende Alkaloide, Saponine, Sterine und weitere Triterpenoide geprüft.
Summary In continuation of earlier described investigations 104 further plant species from 24 families of the indigenous flora and of the sortiment in Gatersleben have been studied preliminarily for occurring alkaloids, saponins, sterols and other triterpenoids using a standard procedure.

am ¶rt;au . 104 24 «», «», «» «».


I. Mitteilung: Aurich und Mitarb. (1965).  相似文献   
128.
Zusammenfassung Von 51 überprüften stickstoffhaltigen Steroiden mit bzw ohne 5-Doppelbindung (Solanum-Steroidalkaloide, N-haltige Cholestan- und Pregnan-Derivate) gaben lediglich 3 eine positive Liebermann-Burchard-Reaktion: N-Acetyltomatidadien, N-Acetyl-solasodien und Dihydrosolasodin A. Auch eine Anzahl 5-ungesättigter Steroidsapogenine und stickstofffreier Pregnan-Derivate zeigte eine nur schwache Farbreaktion.
Summary To obtain information about the value and limitations of the Liebermann-Burchard reaction 51 nitrogenous steroids with or without 5 double bond have been tested. Only 3 of them show a positive colour reaction: the N-acetyl derivatives of tomatidadiene and solasodiene as well as the dihydrosolasodine A. Also some 5-unsaturated steroidal sapogenins and nitrogen-free pregnane derivatives produce colours of only slight intensity.

am ¶rt;u 51 5- ( Solanum, ) 3 -: N--, N-- . 5 - .


XXXVII. Mitteil.: Schreiber, K., 1964. — Liebigs Ann. Chem.674, 168–175.  相似文献   
129.
Rundschau     
Ohne Zusammenfassung  相似文献   
130.
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