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   326篇
  免费   15篇
林业   23篇
农学   1篇
基础科学   1篇
  26篇
综合类   50篇
农作物   5篇
水产渔业   12篇
畜牧兽医   212篇
园艺   1篇
植物保护   10篇
  2023年   3篇
  2021年   4篇
  2020年   10篇
  2018年   2篇
  2017年   2篇
  2016年   3篇
  2015年   3篇
  2014年   5篇
  2013年   18篇
  2012年   9篇
  2011年   11篇
  2010年   11篇
  2009年   13篇
  2008年   15篇
  2007年   13篇
  2006年   16篇
  2005年   10篇
  2004年   12篇
  2003年   17篇
  2002年   16篇
  2001年   6篇
  2000年   11篇
  1999年   14篇
  1998年   5篇
  1997年   2篇
  1996年   6篇
  1995年   4篇
  1994年   3篇
  1991年   4篇
  1990年   4篇
  1989年   14篇
  1988年   5篇
  1987年   2篇
  1986年   2篇
  1985年   2篇
  1984年   7篇
  1983年   5篇
  1982年   4篇
  1980年   2篇
  1979年   2篇
  1978年   2篇
  1974年   2篇
  1970年   7篇
  1969年   2篇
  1967年   2篇
  1966年   2篇
  1947年   2篇
  1939年   2篇
  1925年   2篇
  1921年   2篇
排序方式: 共有341条查询结果,搜索用时 0 毫秒
161.
OBJECTIVE: To compare results of thoracic radiography, cytologic evaluation of bronchoalveolar lavage (BAL) fluid, and histologic evaluation of biopsy and necropsy specimens in dogs with respiratory tract disease and to determine whether histologic evaluation provides important diagnostic information not attainable by the other methods. DESIGN: Retrospective study. ANIMALS: 16 dogs. PROCEDURE: BAL fluid was classified as normal, neutrophilic, eosinophilic, mononuclear, mixed, neoplastic, or nondiagnostic. Radiographic abnormalities were classified as interstitial, bronchial, bronchointerstitial, or alveolar. Histologic lesions were classified as inflammatory, fibrotic, or neoplastic, and the predominant site of histologic lesions was classified as the alveoli, interstitium, or airway. RESULTS: The predominant radiographic location of lesions correlated with the histologic location in 8 dogs. Of 11 dogs with histologic evidence of inflammatory disease, 8 had inflammatory BAL fluid. Of the 2 dogs with histologic evidence of neoplasia, 1 had BAL fluid suggestive of neoplasia, and the other had BAL fluid consistent with septic purulent inflammation. Two dogs without any histologic abnormalities had mononuclear or nondiagnostic BAL fluid. Two dogs with histologic evidence of fibrosis had mononuclear or mixed inflammatory BAL fluid. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that although thoracic radiography, cytologic evaluation of BAL fluid, and histologic evaluation of lung specimens are complementary, each method has limitations in regard to how well results reflect the underlying disease process in dogs with respiratory tract disease. Lung biopsy should be considered in cases where results of radiography and cytology are nondiagnostic.  相似文献   
162.
Re-introduction is a technique widely used in the conservation of threatened bird species. With advances in aviculture the use of captive-produced individuals as the release stock is becoming more commonplace, and ideally, survival of captive-produced, released individuals should be no different from their wild-bred counterparts. During the late 1980s the Critically Endangered Mauritius kestrel (Falco punctatus) was successfully re-introduced into the Bambous mountain range, Mauritius, some 30 years after its local extinction. Between 1987 and 2001 the developing population was closely monitored enabling us to construct re-sighting histories for 88 released and 284 wild-bred kestrels. We used age-structured models in the survival analysis software program MARK to determine if an individual's origin influenced its subsequent survival. Our analysis indicated no compelling evidence for reduced survival among juvenile captive-reared and released individuals, relative to their wild-bred counterparts, across the majority of cohorts and only limited evidence of a cohort-specific effect. This study illustrates that despite the lack of a formal experimental approach it is still feasible to conduct an assessment of re-introduction outcomes and techniques.  相似文献   
163.
164.
A paired-ion liquid chromatographic (LC) technique coupled with fluorometric detection to determine riboflavin in various food matrices is described. Chromatograms of many foods showed 2 peaks of interest due to presence of riboflavin and flavin mononucleotide (FMN). Relatively high levels of FMN were found in raw beef, corned beef, chicken liver, and canned mushrooms. When riboflavin and FMN contents were summed, LC values were comparable to those obtained by the AOAC standard procedures. The LC technique was sensitive, rapid, and simple, yielding a mean standard deviation of 3.1% which was comparable to the AOAC fluorometric method (3.0%) and better than the AOAC microbiological assay (9.6%). Mean spike recoveries were 91.8% for LC compared to 90.5% and 89.6% for the AOAC fluorometric and microbiological methods, respectively.  相似文献   
165.
The non‐invasive type of implantation in the pig is characterized by the maintenance of a thick glycocalyx coating on the uterine epithelial surface microvilli. Present study investigated the alteration in the sialomucin complex (Muc4) expression during the oestrous cycle and early pregnancy in the pig. Endometrial tissue samples were immunostained with the primary antibody to the Muc4 transmembrane subunit ASGP‐2. Muc4 immunostaining increased in the surface and glandular epithelia between days 5 and 10 of oestrous cycle. Immunostaining continued to increase on day 12 with the greatest intensity of uterine Muc4 immunostaining detected on day 15 of the oestrous cycle and early pregnancy. Endometrial Muc4 expression in cyclic gilts decreased dramatically during early proestrous but continued to remain abundant in the surface and glandular epithelium of pregnant gilts during the period of conceptus attachment to the uterine surface.  相似文献   
166.
167.
Tomographic imaging indicates that slabs of subducted lithosphere can sink deep into Earth's lower mantle. The view that convective flow is stratified at 660-kilometer depth and preserves a relatively pristine lower mantle is therefore not tenable. However, a range of geophysical evidence indicates that compositionally distinct, hence convectively isolated, mantle domains may exist in the bottom 1000 kilometers of the mantle. Survival of these domains, which are perhaps related to local iron enrichment and silicate-to-oxide transformations, implies that mantle convection is more complex than envisaged by conventional end-member flow models.  相似文献   
168.
When African violet leaf explants are cultured in vitro, buds and shoots develop directly from the upper leaf surfaces. Three developmentally different African violet chimeras were cultured, and in each case adventitious shoots that developed into plants had the parent chimera pattern. A multicellular origin of the adventitious buds accounts for these results.  相似文献   
169.
170.
The whole cell soluble antigens of two strains (NCTC 11632 and VPB 3313) of feline Porphyromonas salivosa (macacae) were analyzed by Western blotting using serum taken from 40 domestic cats with various grades of periodontal disease. Nine strongly immunogenic protein bands (66, 52, 42, 29, 27, 23, 22, 21 and 19kDa) were selected from both strains for further study. Both strains showed a significant association between overall periodontal grade and serum responses to the 66 and 21kDa bands with significant responses across both strains to all other bands except the 52kDa band. Similarly, both strains showed a significant association between the total colony forming units and serum responses to the 66 and 42kDa bands with significant responses across both strains to all other bands except the 19kDa band. When sera from 25 of these cats were tested by Western blotting against the isolated fimbriae of VPB 3313, there was a significant association between the grade of response of cats to the 42kDa fimbrial preparation and (1) the total reactivity of the mouth (the sum of the responses to all individual whole cell antigens), (2) the total colony forming units of P. salivosa (macacae) at the premolar site, and (3) to their responsiveness to the 42kDa band in the soluble whole cell antigen preparations. These findings suggest that P. salivosa (macacae) is a strong immunogen in the mouths of cats and those cats with more severe periodontal disease have a greater serum antibody reactivity to various soluble whole cell antigens, specifically including the fimbriae of this organism, than those with less severe periodontal disease. Overall, the findings suggest that this organism may be a contributor to periodontal disease in cats.  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