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   114156篇
  免费   6196篇
  国内免费   63篇
林业   5441篇
农学   3587篇
基础科学   648篇
  13420篇
综合类   20608篇
农作物   4392篇
水产渔业   5368篇
畜牧兽医   58184篇
园艺   1307篇
植物保护   7460篇
  2018年   1477篇
  2017年   1668篇
  2016年   1528篇
  2015年   1335篇
  2014年   1645篇
  2013年   4121篇
  2012年   3091篇
  2011年   3576篇
  2010年   2380篇
  2009年   2442篇
  2008年   3574篇
  2007年   3510篇
  2006年   3243篇
  2005年   3101篇
  2004年   2898篇
  2003年   3028篇
  2002年   2830篇
  2001年   3388篇
  2000年   3346篇
  1999年   2685篇
  1998年   1084篇
  1997年   1156篇
  1996年   1048篇
  1995年   1286篇
  1994年   1111篇
  1993年   1127篇
  1992年   2214篇
  1991年   2332篇
  1990年   2288篇
  1989年   2302篇
  1988年   2177篇
  1987年   2173篇
  1986年   2255篇
  1985年   2157篇
  1984年   1829篇
  1983年   1599篇
  1982年   1099篇
  1979年   1669篇
  1978年   1325篇
  1977年   1220篇
  1976年   1169篇
  1975年   1245篇
  1974年   1606篇
  1973年   1555篇
  1972年   1556篇
  1971年   1495篇
  1970年   1420篇
  1969年   1382篇
  1968年   1142篇
  1967年   1267篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Canine angiostrongylosis was diagnosed in a whippet with typical signs of respiratory and circulatory distress. Subclinical Angiostrongylus vasorum infections were also demonstrated in two other whippets belonging to the same owner. All three dogs were given standard anthelmintic levamisole treatment combined with corticosteroids. Two days after initiation of treatment, one of the subclinically infected dogs developed severe hypovolaemic shock that required intravenous fluid therapy and corticosteriods to save its life. The shock is believed to have been caused by an anaphylactic reaction triggered by the rapid release of a large amount of worm antigen in the blood due to the rapid death of adult worms by levamisole. Thus, dog owners should be instructed to monitor dogs undergoing levamisole treatment against A vasorum. Alternatives to levamisole treatment of canine angiostrongylosis should be considered.  相似文献   
992.
Six healthy mares ranging in age from 6 to 12 years and weighing from 415 to 540 kg were used to determine the rectal bioavailability of ketoprofen. For the rectal administration, three different formulations, each containing 1 g of ketoprofen, were administered in a fatty and a hydrophilic suppository base and as a liquid suspension. An average elimination half-life of 1.3 h (±1.2) was found. The average value for the total plasma clearance ( Cl T) was 131.9 mL/min.kg (range 95-183.5). The volume of distribution V d(area) was 255 mL/kg and the mean residence time (MRT)P = 0.05; Friedman test). Despite the low rectal bioavailability obtained in this study, there was some evidence for the clinical effectiveness of the rectal formulations.  相似文献   
993.
1. Associations between body weight and rectal temperature were observed in female turkeys.

2. Turkeys with lower weights between 13 and 30 d of age tended to have higher temperatures.

3. Turkeys with lower weights at 7 d exhibited depressed body temperatures.

4. Higher or lower body temperatures may be associated with poorer performance depending on the time of appearance.  相似文献   

994.
Clinical pathologic alterations in horses during a water deprivation test   总被引:1,自引:0,他引:1  
A 72-hour water deprivation test was performed in 12 horses to determine clinical pathologic changes. Reference values for electrolyte (X) clearance, expressed as a percentage of creatinine clearance (CLCR; %CLCRX), were also determined. A comparison was made between urine concentration measurement techniques. Results of %CLCRX determination in 12 horses before water deprivation were 0.034 +/- 0.095 %CLCRNa, 42.4 +/- 9.8 %CLCRK, 0.352 +/- 0.190 %CLCRCl, and 0.710 +/- 0.250 %CLCRP. During water deprivation, there was individual variation for electrolyte clearances, but Na excretion increased significantly (P less than 0.01) at 24 and 48 hours. After 48 hours' water deprivation, %CLCRNa decreased significantly, but was still greater than the initial clearance. Plasma protein was a better indicator of water deprivation (dehydration) in the horse than was PCV. Electrolyte concentrations in serum and urine were determined. Little significant (P less than 0.01) change in acid-base values was noticed after 72 hours' water deprivation. Urine osmolality (as determined by osmometry) was compared with sp gr (determined by refractometry) in determining urine concentration. Initially, sp gr correlated well with urine osmolality determinations, but this correlation decreased after 48 hours.  相似文献   
995.
996.
997.
Diaphragmatic hernia. Analysis of fifty-six cases in dogs and cats   总被引:1,自引:0,他引:1  
A review of fifty-six cases of diaphragmatic hernia in the dog and cat is presented. These were admitted to the University of Glasgow Veterinary School between January 1972 and August 1978. Fifty-three of these cases were treated surgically but only twenty-nine survived to be discharged from the hospital. The reasons for the low survival rate are discussed in detail.  相似文献   
998.
Reference is made to work undertaken by Stehle (1983) on rapid semiquantitative determination of urinary protein in pigs for slaughter to identify premortal strain and stress, with additional studies being conducted into the suitability of the method. The investigations performed for this study covered urinary protein samples from 59 living and 762 slaughtered pigs. The Biophan E paper strip test was applied to groups of animals, and, when compared to high-accuracy laboratory determination of urinary protein, it provided sufficiently accurate information on the presence of stress-related proteinuria. Its accuracy, however, proved to be insufficient, when individual animals were examined. The number of clearly stressed slaughter pigs was unexpectedly high, although the same animals had been rated clinically inconspicuous prior to slaughter. Brief rest period resulted in significant rise of stress. The Biophan E paper strip test was found to be suitable for instantaneous determination of stress and strain on pigs for slaughter.  相似文献   
999.
Beef cows were used to determine if suckling influences release of LH via endogenous opioids at 28 +/- 4 d after parturition. Cows of similar weight and body condition (6.8 +/- .1, 1 = emaciated, 9 = obese) were assigned randomly to five groups (n = 6 to 7): 1) control-suckled/saline (suckled 15 min every 6 hr for 48 hr); 2) control-suckled/naloxone; 3) calf-removal/saline (calf removal for 52 hr); 4) calf-removal/naloxone; and 5) control-suckled/GnRH (Gonadotropin-Releasing Hormone). At 0 hr, saline was administered to all cows. This treatment was continued at 6 hr intervals for 24 hr. Either naloxone (0.5 mg/kg), GnRH (40 ng/kg) or saline was administered to cows in their respective groups every 6 hr during the ensuing 24-hr period in calf-removal groups, or immediately preceding each suckling episode in the control-suckled groups. Blood samples for analysis of luteinizing hormone (LH) were collected at 15-min intervals for 1 hr prior to and 3 hr after treatment at 0, 24, 36 and 48 hr. Cows were observed for estrus twice daily. All cows in the control-suckled/GnRH group released LH (P less than .05) in response to exogenous GnRH, indicating the presence of releasable quantities of the gonadotropin. Mean concentrations of LH were not effected (P greater than .05) by the control-suckled regime. However, calf-removal alone, or in combination with naloxone, increased (P less than .05) mean concentrations of LH by 48 hr.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
1000.
Attempts to reproduce in calves the arthropathy associated with Brucella abortus strain 19 (S19) vaccination by direct intra-articular injection of S19 or virulent Brucella cells were unsuccessful. Intra-articular injection of rabbits and a calf with immune complexes isolated from the synovial fluid of a field case produced clinical and histological signs of arthropathy accompanied by the development of rheumatoid factor.  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