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   248篇
  免费   17篇
林业   5篇
农学   2篇
  10篇
综合类   49篇
农作物   8篇
水产渔业   4篇
畜牧兽医   176篇
植物保护   11篇
  2020年   3篇
  2019年   4篇
  2018年   9篇
  2017年   7篇
  2016年   6篇
  2015年   3篇
  2014年   6篇
  2013年   10篇
  2012年   6篇
  2011年   5篇
  2010年   15篇
  2009年   20篇
  2008年   10篇
  2007年   11篇
  2006年   4篇
  2005年   2篇
  2004年   7篇
  2003年   3篇
  2002年   3篇
  2001年   6篇
  2000年   3篇
  1999年   6篇
  1998年   17篇
  1997年   8篇
  1996年   14篇
  1995年   7篇
  1994年   4篇
  1993年   4篇
  1992年   8篇
  1991年   10篇
  1990年   9篇
  1989年   3篇
  1988年   2篇
  1987年   1篇
  1984年   1篇
  1982年   3篇
  1981年   2篇
  1980年   1篇
  1979年   3篇
  1977年   2篇
  1976年   1篇
  1975年   2篇
  1974年   4篇
  1972年   2篇
  1964年   1篇
  1962年   1篇
  1961年   1篇
  1960年   1篇
  1959年   1篇
  1954年   2篇
排序方式: 共有265条查询结果,搜索用时 15 毫秒
61.
An 8-year-old terrier cross and a 10-year-old German Shorthaired Pointer presented to the University Veterinary Centre, Sydney, for investigation of long-standing tenesmus and dyschezia. Both patients had an annular adenocarcinoma at the colorectal junction. Exploratory laparotomy was performed and the affected large intestinal segment was removed by resection and anastomosis. In both dogs, the caudal mesenteric artery was intimately associated with the mass, necessitating its ligation and transection. Postoperatively, there was no evidence of anastomosis breakdown in either case and both animals recovered well from surgery. The dogs were euthanased 8 and 10 months, respectively, after surgery because of clinical signs relating to metastatic disease.  相似文献   
62.
Objective— To investigate the use of computed tomography (CT) arthrography in cadaveric canine stifles with particular emphasis on the diagnosis of meniscal injury.
Study Design— Prospective cadaver study.
Sample Population— Pelvic limbs from adult Beagles (n=10).
Methods— After survey CT scan of each stifle oriented in the dorsal plane, positive contrast stifle CT arthrogram (CTA) was performed using the same slice orientation. Each stifle was then randomly allocated into 1 of 2 treatment groups: group A—arthrotomy, cranial cruciate ligament (CCL) transection and simulated injury to the caudal horn of the medial meniscus; group B—arthrotomy and CCL transection only. CT scan was repeated as before and post-arthrotomy images were interpreted by a radiologist unaware of treatment grouping.
Results— The cranial and caudal cruciate ligaments, medial and lateral menisci, menisco-femoral ligament, and long digital extensor tendon were all identifiable on CTA images. CTA was 90% sensitive and 100% specific for diagnosing simulated caudal horn meniscal injury.
Conclusions— Stifle CTA enables identification of intra-articular structures within the stifle and is a reliable method for identifying simulated meniscal injuries in a cadaver model.
Clinical Relevance— CTA imaging of the canine stifle has potential clinical value for detection of meniscal injury.  相似文献   
63.
陶冶  贾复 《水产科学》1999,18(6):30-33
根据目前拖网渔船在节能方面的需要,采用导管螺旋桨以改善渔船的推进性能,并对导管螺旋桨的设计和具体应用的优的缺点作初步的探讨。  相似文献   
64.
65.
Data from the Global Oscillation Network Group (GONG) project and other helioseismic experiments provide a test for models of stellar interiors and for the thermodynamic and radiative properties, on which the models depend, of matter under the extreme conditions found in the sun. Current models are in agreement with the helioseismic inferences, which suggests, for example, that the disagreement between the predicted and observed fluxes of neutrinos from the sun is not caused by errors in the models. However, the GONG data reveal subtle errors in the models, such as an excess in sound speed just beneath the convection zone. These discrepancies indicate effects that have so far not been correctly accounted for; for example, it is plausible that the sound-speed differences reflect weak mixing in stellar interiors, of potential importance to the overall evolution of stars and ultimately to estimates of the age of the galaxy based on stellar evolution calculations.  相似文献   
66.
Atmospheric general circulation models used for climate simulation and weather forecasting require the fluxes of radiation, heat, water vapor, and momentum across the land-atmosphere interface to be specified. These fluxes are calculated by submodels called land surface parameterizations. Over the last 20 years, these parameterizations have evolved from simple, unrealistic schemes into credible representations of the global soil-vegetation-atmosphere transfer system as advances in plant physiological and hydrological research, advances in satellite data interpretation, and the results of large-scale field experiments have been exploited. Some modern schemes incorporate biogeochemical and ecological knowledge and, when coupled with advanced climate and ocean models, will be capable of modeling the biological and physical responses of the Earth system to global change, for example, increasing atmospheric carbon dioxide.  相似文献   
67.
This paper reports the synthesis and the biological activity of novel tetrahydronaphthalenes with substitution of functional groups at each position of the aromatic ring and substitution of various alkyl groups at the 1-position of the non-aromatic ring. These compounds exhibited pre-emergent herbicidal activity which was determined by the orientation and type of functional groups on the aromatic ring with the 1,1-dimethyl substitution on the non-aromatic ring. The activity tended to be highest for nitro or methyl at the 5- and 7-positions with an amino or ester group at the 6-position and a dimethyl substitution at the 1-position.  相似文献   
68.
69.
The clinical, pathological and biochemical findings of a study of 30 Poll Hereford, Hereford, Poll Hereford cross or Hereford cross calves affected with branched chain ketoacid dehydrogenase (BCKAD) complex deficiency or maple syrup urine disease (MSUD) are presented. In breeding studies, 6 of 21 calves from obligate heterozygote matings were affected with MSUD, suggesting the disease is inherited in an autosomal recessive manner. Calves were clinically affected from birth, but there were variations in the subsequent course of progressive deterioration of central nervous system function. Concentrations of the branched chain amino acids and keto acids were elevated in pre-suckle plasma and cerebellar water content was higher in affected calves. Activity of BCKAD complex was minimal in fibroblasts cultured from an affected calf. Spongiform encephalopathy and elevated ratios of the branched to straight chain amino acids in formalin fixed cerebral tissue were found in a stillborn foetus and a 3-month-old Hereford calf. These findings suggest the disease occurs prenatally and that a delayed form may exist.  相似文献   
70.
Walnuts are a valuable crop the sale and export potential of which may be severely limited by contamination with aflatoxins, metabolites produced on infection with Aspergillus flavus. The effect of a series of four naphthoquinones [1,4-naphthoquinone (1); juglone (5-hydroxy-1,4-naphthoquinone) (2); 2-methyl-1, 4-naphthoquinone (3); and, plumbagin (5-hydroxy-2-methyl-1, 4-naphthoquinone) (4)] (Figure 1), which occur in walnut husks, on fungal viability and aflatoxigenesis was studied in vitro. The quinones delayed germination of the fungus and were capable of completely inhibiting growth at higher concentrations. Their effect on aflatoxin levels was highly dependent on the concentration of individual naphthoquinones in the media. At higher concentrations, aflatoxin production was decreased or completely inhibited, but at lower concentrations there was a stimulatory effect on aflatoxin biosynthesis, with a >3-fold increase at 20 ppm of 3. Structural features associated with decreased fungal viability and greatest effect on aflatoxigenesis are the presence of a 5-hydroxyl or 2-methyl substituent, but there is no significant additive effect when both of these substituents are present.  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