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   1730篇
  免费   99篇
林业   72篇
农学   22篇
基础科学   17篇
  218篇
综合类   337篇
农作物   50篇
水产渔业   45篇
畜牧兽医   935篇
园艺   33篇
植物保护   100篇
  2021年   14篇
  2020年   28篇
  2019年   21篇
  2018年   24篇
  2017年   25篇
  2016年   41篇
  2015年   18篇
  2014年   28篇
  2013年   59篇
  2012年   61篇
  2011年   75篇
  2010年   42篇
  2009年   33篇
  2008年   70篇
  2007年   68篇
  2006年   55篇
  2005年   52篇
  2004年   61篇
  2003年   63篇
  2002年   59篇
  2001年   53篇
  2000年   45篇
  1999年   37篇
  1998年   23篇
  1997年   27篇
  1996年   18篇
  1994年   14篇
  1993年   17篇
  1992年   24篇
  1991年   23篇
  1990年   31篇
  1989年   46篇
  1988年   36篇
  1987年   37篇
  1986年   37篇
  1985年   20篇
  1984年   20篇
  1983年   23篇
  1982年   15篇
  1979年   19篇
  1978年   17篇
  1977年   16篇
  1976年   18篇
  1974年   17篇
  1973年   21篇
  1972年   23篇
  1970年   19篇
  1969年   18篇
  1968年   16篇
  1967年   13篇
排序方式: 共有1829条查询结果,搜索用时 0 毫秒
41.
A 10-year-old female neutered cross-breed dog presented with a 4-month history of chronic intermittent diarrhoea and vomiting. Abdominal ultrasound showed dilated loops of small intestine and a suspected faecolith. Exploratory surgery revealed a caecal impaction and a typhlectomy was performed. Histopathological examination of caecal and full thickness small intestine sections demonstrated atrophy of smooth muscle fibres as well as an influx of plasma cells, lymphocytes and macrophages, and mild lymphoplasmacytic and eosinophilic enteritis. This combination of caecal impaction and chronic intestinal pseudo-obstruction has not been reported previously in the dog.  相似文献   
42.
Pruritus is a common complaint in equine medicine. While pruritus in most horses is due to ectoparasites (midges, flies, mites) or environmental allergens (pollens, barn dust, moulds, etc.), other causes such as staphylococcal or fungal infections, vasculitis, and internal organ dysfunction should not be overlooked. In a rational approach to the pruritic horse, history and physical examination become very important as a guide to choosing diagnostic tests.  相似文献   
43.
Insulin-like growth factor binding protein-3 (IGFBP-3) suppresses proliferation of numerous cell types, including myogenic cells, via both insulin-like growth factor (IGF)-dependent and IGF-independent mechanisms; however, the mechanism of IGF-independent suppression of proliferation is not clearly defined. In nonmuscle cells, binding of IGFBP-3 to the low-density lipoprotein receptor-related protein-1 (LRP-1)/activated α(2)M receptor is reportedly required for IGFBP-3 to inhibit proliferation. These findings suggest that binding to this receptor also may be required for IGFBP-3 to suppress proliferation of cultured myogenic cells. To investigate the role of the LRP-1 receptor in suppression of myogenic cell proliferation by IGFBP-3, we have examined the effect of receptor-associated protein, an LRP-1 receptor antagonist, on recombinant porcine (rp)IGFBP-3 inhibition of L6 myogenic cell proliferation. Treatment with receptor-associated protein results in a 37% decrease (P < 0.05) in the ability of rpIGFBP-3 to inhibit L6-cell proliferation. In L6 cells subjected to LRP-1 small interfering RNA treatment for 48 h (LRP-1 silenced), LRP-1 mRNA levels were reduced by greater than 80% compared with control cultures treated with nonsense small interfering RNA (mock silenced). In addition, the 85-kDa transmembrane subunit of LRP-1 was undetectable in Western immunoblots of total protein lysates from LRP-1-silenced cells. Even though LRP-1 mRNA and protein levels were dramatically reduced in LRP-1-silenced L6 cells compared with mock-silenced controls, rpIGFPB-3 suppressed proliferation rate to the same extent in both LRP-1-silenced and mock-silenced cultures. Our results strongly suggest that, in contrast to data obtained for nonmuscle cell lines, the LRP-1 receptor is not required for IGFBP-3 to suppress proliferation of L6 myogenic cells.  相似文献   
44.
45.
Sympathetic denervation in a 20-year-old, gray, Thorough-bred-Percheron gelding was manifested by cutaneous hyperthermia and sweating over the right side of the body, demarcated by a line from the withers to the elbow and extending cranially. There was cutaneous hyperthermia over the right side of the head, but other signs of Horner's syndrome (sweating, ptosis, miosis, enophthalmos) were not present. The pattern of cutaneous hyperthermia and sweating was consistent with sympathetic denervation localized to the cervicothoracic ganglion, and thoracic radiographs revealed increased density in the craniodorsal thorax. Cytologic evaluation of a sample of pleural effusion revealed mesothelial cells containing melanin and cells suggestive of melanocytes or melanoblasts. Treatment with oral cimetidine and intrapleural cisplatin was not successful. A necropsy was not performed, but the clinical findings supported a diagnosis of thoracic melanoma involving the cervicothoracic ganglion.  相似文献   
46.
This study reports data obtained from per-rectal 99mTc-pertechnetate portal scintigraphy in normal cats. It examines the effects of chemical restraint and the methods employed in defining regions of interest (ROIs) on the shunt index derived from this data. Six normal cats were used for the study; all six were chemically restrained for imaging using propofol and later four of them were manually restrained for comparison. Portal blood flow was studied and the mean shunt index was found to be 5.9%± 3.9 when ROIs were operator defined and 9.2%± 4.4 when ROIs were defined using an isocontour program. In cats that were restrained using propofol and operator defined ROIs, the mean value for the time between detection of radioactivity in the liver and in the heart was 14 ± 1 seconds.  相似文献   
47.
A radiological assessment of 35 canine nasal tumours using an objective scoring system was carried out and related to patient survival. The scoring system demonstrated significant increases in disease-free interval and survival for dogs with scores of less than 12 compared to those with scores of 1 2 or above.  相似文献   
48.
The structure of the shell of the egg of Trichuris trichiura was examined using light microscopy as well as scanning and transmission electron microscopy. The results confirmed its three-layered structure and provided evidence that the cores of the polar plugs, which could be seen to be extensions of the shell's middle layer, could be lost en bloc, either mechanically or chemically, and in this way probably provided an exit for the first stage larva at hatching.  相似文献   
49.
Prepubic tube cystostomy was performed in 10 dogs and one cat. Indications include urinary bypass following urethral trauma or surgery (six cases), following surgery for prostatic abscesses or cysts (four cases) and bladder atony secondary to urethral obstruction (one case). Tubes were left in situ for a minimum of seven days. All patients returned to normal micturition following tube removal. Urine leakage occurred for up to four days after tube removal by which time the stoma was granulating. Nosocomial infection was a consistent finding, but was controlled with antibiotic treatment following tube removal. Tube cystostomy was considered an effective means for diverting irritant urine from healing epithelium and thereby minimising the risk of urethral cicatrisation. It may also be indicated in the management of urinary retention as an alternative to repeated urethral catheterisation. This study indicates that tube cystostomy is readily performed, with few unexpected or serious complications.  相似文献   
50.
A visual analog scale and a numeric scoring scale were designed for the assessment of dynamic intraoperative mesenteric portovenography in the dog and cat. Two independent observers evaluated both scoring scales for reproducibility (differences between observers) and repeatability (within-observer differences) in the assessment of 60 trial portovenograms. Agreement (interchangeability) of both scales was evaluated by comparing the scores obtained in the assessment of 200 portovenograms obtained from 100 dogs and cats. There was no statistical difference between the two observers when scoring the same portovenogram for either the visual analog scale (p = .730, reproducibility coefficient = 17.85 units) or the numeric scoring scale (scores identical, reproducibility coefficient = 0). There was no statistical difference, for either of the observers, when the same portovenogram was assessed on two separate occasions using the visual analog scale (observer 1, p = .35, repeatability coefficient = 17.93 units; observer 2, p = .42, repeatability coefficient = 8.27 units) or the numeric scoring scale (scores given by both observers were identical, repeatability coefficient = 0 for both observers). The results of comparison between the visual analog scale and numeric scoring scale confirmed that the two scoring systems were not directly interchangeable. Although both scoring systems demonstrated good reproducibility and repeatability, the numeric scoring scale possessed a number of inherent deficiencies that suggested it was not the method of choice for the assessment of the subjective data obtained from dynamic intraoperative mesenteric portovenography.  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