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   2832篇
  免费   342篇
  国内免费   27篇
林业   7篇
农学   4篇
  15篇
综合类   89篇
农作物   3篇
畜牧兽医   3078篇
园艺   2篇
植物保护   3篇
  2024年   2篇
  2023年   48篇
  2022年   42篇
  2021年   119篇
  2020年   143篇
  2019年   150篇
  2018年   123篇
  2017年   143篇
  2016年   86篇
  2015年   115篇
  2014年   148篇
  2013年   145篇
  2012年   122篇
  2011年   103篇
  2010年   122篇
  2009年   131篇
  2008年   144篇
  2007年   152篇
  2006年   118篇
  2005年   145篇
  2004年   114篇
  2003年   79篇
  2002年   70篇
  2001年   75篇
  2000年   50篇
  1999年   66篇
  1998年   62篇
  1997年   38篇
  1996年   48篇
  1995年   25篇
  1994年   35篇
  1993年   23篇
  1992年   19篇
  1991年   14篇
  1990年   25篇
  1989年   18篇
  1988年   15篇
  1987年   5篇
  1986年   15篇
  1985年   8篇
  1984年   17篇
  1983年   17篇
  1982年   13篇
  1981年   13篇
  1980年   23篇
  1979年   6篇
  1976年   3篇
  1974年   1篇
  1973年   1篇
  1956年   1篇
排序方式: 共有3201条查询结果,搜索用时 15 毫秒
971.
8例犬间隔1个月分别施行2次腹部手术,第1次采用硬膜外阻滞(试验组,n=8),第2次采用硫喷妥钠静脉麻醉(对照组,n=8)。分别于麻醉前(T0)、麻醉后(T1)、切开腹壁时(T2)、手术30min(T3)、手术完毕时(T4)、手术后24h(T5)、手术后48h(T6)7个时间静脉采血,采用放射免疫法测定血浆皮质醇、白细胞介素-2浓度,采用比色法测定血糖浓度。结果:(1)对照组血浆皮质醇浓度平均值显著高于试验组(P<0·05),尤其在T3、T4时显著高于试验组(P<0·05)。对照组在T3、T4时血浆皮质醇浓度显著高于T0(P<0·05),而试验组各时间与T0比较均无显著差异(P>0·05);(2)对照组血浆白细胞介素-2浓度平均值极显著低于试验组(P<0·01),尤其在T1、T2、T5和T6时显著低于试验组。对照组在T5时、试验组在T3、T4时其血浆白细胞介素-2浓度均显著低于T0;(3)对照组血糖浓度平均值显著高于试验组,尤其在T4时显著高于试验组。对照组在T3、T4、T5和T6时、试验组则在T4时其血糖浓度均显著高于T0。结论:硬膜外阻滞组与硫喷妥钠静脉麻醉比较,硬膜外阻滞能够更有效缓解犬腹部手术的应激反应。  相似文献   
972.
孕激素诱导的生长激素与犬的乳腺肿瘤   总被引:1,自引:0,他引:1  
乳腺肿瘤是犬的最常见的肿瘤,约占母犬肿瘤总数的一半;乳腺肿瘤约有一半是恶性肿瘤,发生转移的比率很高。犬乳腺肿瘤的发病原因还不很明确,它的形成都受哪些因子调节还未完全确定。孕激素能够诱导乳腺组织生成并蓄积生长激素,使乳腺增生,最终导致犬乳腺肿瘤的形成。在此过程中,雌激素受体、孕激素受体、生长激素结合蛋白和生长激素受体在乳腺癌的形成、发展中起关键作用。从内分泌的角度对犬乳腺肿瘤发病机理作了简单综述,以期为激素治疗乳腺肿瘤提供一些理论依据。  相似文献   
973.
用家兔皮肤毒性试验测得三线镰刀菌污染玉米中T—2毒素的含量约为1.8g/kg试验灵敏度为0.08μg.此霉玉米经提取纯化后得白色针状结晶,根据毒素结晶的熔点、C、H元素含量、红外光谱、质谱碎片峰及1H核磁共振谱确证为T-2毒素,纯度为95.84%.毒素对锦鲤鱼苗72、96、120的LD_(50)分别为0.0847±0.0034ppm,0.0760±0.0053ppm,0.0705±0.0036ppm.每天连续口服毒素0.5~1mg/kg体重,可引起犬的出血性综合征,表现为呕吐、便血,尸检见肠道出血坏死,且充满大量的血液;组织学检查表明,肠粘膜广泛的出血坏死,牌小体萎缩和数量减少,骨髓造血细胞消失.将毒素给小鼠连续灌胃(2mg/kg体重),可引起骨髓核细胞数下降,但停毒后,逐渐恢复到正常水平.  相似文献   
974.
This paper describes the electrocardiographic, echocardiographic (two-dimensional, M-mode, contrast and Doppler) and non-selective angiocardiographic features in a 3 year old female Beagle with dilated coronary sinus due to persistent left cranial vena cava. Negative P waves in leads III and aVR and a positive P wave in lead aVL were seen. Echocardiographically, a hipoechoic circular structure was seen between the left atrium and the pericardium in the area where the coronary sinus is located. A velocity pattern with two peaks was obtained, one systolic with velocity = 0.44 ± 0.05 m/sec and the other diastolic with velocity = 0.27 ± 0.01 m/sec. By M-mode echocardiography, at level of the aorta and the left atrium, a linear structure was identified between the left atrium and the pericardium; this structure was characterized by phasic movements of the anterior wall during the cardiac cycle. Following a left cephalic vein injection of saline, bubbles were seen within the coronary sinus; when saline was injected into the right cephalic vein, bubbles were also seen within the coronary sinus and right atrium and ventricle. Non-selective angiocardiography confirmed a dilated coronary sinus with persistent left cranial vena cava. The right cranial vena cava was absent. The dog was clinically normal and the unusual vessel was an incidental finding.  相似文献   
975.
Chronic Nasal Disease in the Dog: Its Radiographic Diagnosis   总被引:1,自引:0,他引:1  
The radiographic signs of 40 dogs with chronic nasal disease were tabulated and compared with the definitive diagnoses. Erosion of the vomer bone and/or an external mass were present in 16 of 18 dogs that had nasal tumors. Areas of radiolucency in the nasal cavity were present in 8 of 15 dogs that had nasal fungal disease. Radiographic examination did not provide a highly reliable diagnosis for all dogs with chronic nasal disease.  相似文献   
976.
A 6-year-old male Saint Bernard dog was examined because of a firm nonpainful tail-base mass. Radiographs revealed an expansile heterogeneous bony mass of the sixth coccygeal vertebra. The tail was amputated. The histologic diagnosis was coccygeal vertebral chondrosarcoma. Chondrosarcomas account for ten to eleven percent of all skeletal tumors and occur commonly in the flat bones in large-breed dogs. Radiographically chondrosarcomas appear predominantly osteolytic but may contain mottled mineralized densities. In the dog described here the radiographic signs were typical of a malignant cartilaginous tumor: cortical destruction, mottled mineralized densities, ill-defined margins, and continued but relatively slow growth. However, there was no periosteal reaction and the chondrosarcoma was at an unusual site.  相似文献   
977.
The incidence of pancreatic degenerative atrophy (PDA) was investigated in 59 German shepherd dogs from two kindred. The male progenitors were the same in both kindred. In the four litters of the first kindred the incidence of PDA was 24 % (10 dogs out of 41), and there was at least one affected dog in each litter. When one of the litter bitches, later affected with PDA, was mated with one of the obligate carriers of PDA, one of the resultant seven offspring has so far been found to suffer from PDA. In the second kindred when a PDA-affected bitch and a clinically healthy male (heterozygote) were mated, two of the resultant six offspring were found to suffer from PDA.These results indicate that PDA is a disease inherited as an autosomal recessive trait, although the possibility of dominant inheritance with incomplete penetrance cannot be excluded.  相似文献   
978.
A 9-year-old female spayed mixed-breed dog was presented with a ten-week history of vomiting. A survey abdominal radiograph showed a soft tissue mass on the lesser curvature of the stomach and an adjacent thickened greater curvature. A barium contrast study confirmed the presence of this mass. The radiographic diagnosis was gastric tumor. Radiographic signs of gastric neoplasia include soft tissue masses or thickening of the stomach wall, delayed gastric emptying, immobility of portions of the stomach wall, and residual stomach-wall staining by barium. Necropsy revealed a gastric lymphosarcoma that had infiltrated the entire circumference of the pyloric antrum. The most common gastric malignancy in the dog is adenocarcinoma. Gastric lymphosarcoma is considered rare.  相似文献   
979.
Cinefluorography and videoflurography were used to record and analyze the functional swallowing deficits of nine dogs with spontaneous oropharyngeal swallowing problems. Based on the clinical and radiographic signs observed in one dog with experimentally induced bilateral hypoglossal palsy and comparison with cinefluorograms of normal dogs, the nine spontaneous dysphagias were divided into five oral dysphagias and four pharyngeal dysphagias. Dogs with oral dysphagias had problems with tongue control and in prehending and transporting food and fluid to the oropharynx. On cinefluorograms, a poor closure of the oral egress led to the loss of contrast medium from the mouth, and a weak tongue-thrust action caused retention of contrast medium in the oropharynx. The clinical and radiographic signs could be duplicated by hypoglossal neurectomy. In contrast to the pharyngeal dysphagias, aspiration pneumonia was noticeably absent in oral dysphagias. The dogs with pharyngeal dysphagia had severe difficulties in transporting the food from the oropharynx to the laryngopharynx owing to a poor contractility of the pharyngeal muscles. The latter resulted in contrast medium retention in the pharynx and laryngotracheal aspiration. The need was stressed for a careful differentiation between oral and pharyngeal dysphagias on one hand, and cricopharyngeal dysphagias on the other hand. In oral dysphagias, cricopharyngeal myotomy appeared of no use. In pharyngeal dysphagias, cricopharyngeal myotomy severely aggravated the clinical signs by causing a cricopharyngeal chalasia.  相似文献   
980.
Emphysematous cholecystitis not associated with diabetes mellitus was diagnosed in three dogs. All three dogs were examined because of vomiting. Neutrophilia, elevated serum alkaline phosphatase, and normal serum glucose were present in each animal. A gas-filled gallbladder and pericholecystic gas were seen radiographically in all three dogs; a cholecystolith was present in one dog. A cholecystectomy was performed on two dogs. Cultures of bacteria from these two bladders revealed Clostridium sp. One of these dogs was euthanized because of acute renal tubular necrosis that was diagnosed after ten days of treatment with gentamicin. The second dog recovered without incident. The third dog was treated successfully with antibiotics.  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