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   325篇
  免费   18篇
林业   20篇
农学   3篇
基础科学   2篇
  47篇
综合类   39篇
农作物   10篇
水产渔业   10篇
畜牧兽医   192篇
园艺   4篇
植物保护   16篇
  2023年   2篇
  2022年   2篇
  2021年   9篇
  2020年   4篇
  2019年   12篇
  2018年   6篇
  2017年   9篇
  2016年   4篇
  2015年   3篇
  2014年   6篇
  2013年   16篇
  2012年   17篇
  2011年   18篇
  2010年   14篇
  2009年   7篇
  2008年   26篇
  2007年   26篇
  2006年   19篇
  2005年   16篇
  2004年   17篇
  2003年   16篇
  2002年   20篇
  2001年   9篇
  2000年   2篇
  1999年   4篇
  1998年   2篇
  1997年   3篇
  1996年   1篇
  1995年   3篇
  1994年   1篇
  1993年   3篇
  1992年   6篇
  1991年   6篇
  1990年   9篇
  1989年   2篇
  1988年   1篇
  1987年   3篇
  1986年   3篇
  1985年   2篇
  1984年   2篇
  1983年   2篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1977年   2篇
  1971年   1篇
  1970年   1篇
  1963年   1篇
  1960年   1篇
  1947年   1篇
排序方式: 共有343条查询结果,搜索用时 15 毫秒
1.
A 13-year-old neutered female Yorkshire terrier presented with a history of progressive episodic weakness and disorientation of 4 months duration. Physical and neurologic examinations were normal at presentation. Abdominal ultrasound revealed a mass involving the right adrenal gland. Standard planar scintigraphy was performed at 4, 18, and 24 hours after intravenous injection 185 MBq (5mCi) of 123I-labeled metaiodobenzylguanidine (123I-MIBG). An area of focal intense uptake was identified in the area of the right adrenal gland. A pheochromocytoma was confirmed histologically after surgical excision.  相似文献   
2.
3.
The use of plant water status indicators such as midday stem water potential (Ψstem) and maximum daily trunk shrinkage (MDS) in irrigation scheduling requires the definition of a reference or threshold value, beyond which irrigation is necessary. These reference values are generally obtained by comparing the seasonal variation of plant water status with the environmental conditions under non-limiting soil water availability. In the present study an alternative approach is presented based on the plant’s response to water deficit. A drought experiment was carried out on two apple cultivars (Malus domestica Borkh. ‘Mutsu’ and ‘Cox Orange’) in which both indicators (Ψstem and MDS) were related to several plant physiological responses. Sap flow rates, maximum net photosynthesis rates and daily radial stem growth (DRSG) (derived from continuous stem diameter variation measurements) were considered in the assessment of the approach. Depending on the chosen plant response in relationship with Ψstem or MDS, the obtained reference values varied between −1.04 and −1.46 MPa for Ψstem and between 0.17 and 0.28 mm for MDS. In both cultivars, the approach based on maximum photosynthesis rates resulted in less negative Ψstem values and smaller MDS values, compared to the approaches with sap flow and daily radial stem growth. In the well-irrigated apple trees, day-to-day variations in midday Ψstem and MDS were related to the evaporative demand. These variations were more substantial for MDS than for midday Ψstem.  相似文献   
4.
In a previous study we showed that feeding fish meal significantly increased muscle long chain n-3 fatty acids (FA) and hot carcass weight. In this study we compared the effect of fish meal and fish oil on increasing muscle long-chain FA. We also investigated whether the increase in carcass weight was due to the effect of dietary enrichment of muscle long-chain n-3 FA on muscle membrane phospholipids and(or) to rumen by-pass protein provided by fish meal. Forty crossbred ([Merino x Border Leicester] x Poll Dorset) wether lambs between 26 and 33 kg BW were randomly assigned to one of five treatments: 1) basal diet of oaten:lucerne chaff (Basal); 2) Basal + fish meal (9% DM) = FM; 3) Basal + fish oil (1.5% DM) with protected sunflower meal (9% DM ) = FOSMP; 4) Basal + fish oil (1.5% DM) = FO; or 5) Basal + protected sunflower meal (10.5% DM) = SMP. Daily intake of ME (9.60 - 10.5 MJ ME/d) and CP (150 to 168 g/d) in all treatments was kept similar by varying the ratio of oaten:lucerne chaff and by feeding the animals at 90% ad libitum intake. Blood samples were collected at the start of the experiment and on the day (d 42) prior to slaughter. Lambs were then slaughtered at a commercial abattoir. At 24 h postmortem carcass traits were measured and longissimus thoracis muscle taken for analysis of FA of phospholipid and triglyceride fractions. Lambs fed FO and FOSMP showed a marked increase in muscle longchain n-3 FA (P < 0.001) and a reduction in magnitude of the rise in insulin concentration (P < 0.001) after feeding compared with lambs fed Basal and SMP diets. Lambs in FM had a moderate increase (P < 0.001) in muscle long-chain n-3 FA content. Compared with Basal diet, both plasma total cholesterol (P < 0.02) and high-density lipoprotein cholesterol (P < 0.001) levels were greater in SMP and less in FO and FOSMP treatments. The i.m. fat content was reduced (P < 0.05) in FM and FO treatments, but carcass weight was increased only with fish meal (P < 0.03). Adding SMP to FO produced muscle with an intermediate level of i.m. fat, whereas muscle long-chain n-3 FA, i.m. fat, and insulin concentration were unchanged with SMP treatment. These results indicate that an increase in carcass weight in FM may be due to the supply of ruminally undegraded protein. They also suggest that fish oil along with fish meal can increase long-chain n-3 FA content in phospholipid of muscle membrane. This may be associated with reduced i.m. fat content and altered insulin action and lipoprotein metabolism.  相似文献   
5.
6.
Objective: To report a case of femoral artery thrombosis and its medical management in a young dog. Case summary: A 13‐week‐old, female Boxer puppy presented with hind limb paralysis after an abdominal crush injury. A left femoral artery thrombus was identified on ultrasound. No spinal trauma was visualized in imaging studies. Clinical management of arterial thrombosis in a 13‐week‐old puppy with streptokinase and dalteparin therapy is described. New or unique information provided: This paper describes an unusual presentation of arterial thrombosis. The medical management with streptokinase and dalteparin is also out of the ordinary. Images that document the development of compensatory circulation around the thrombosed vessel are included. Additionally, this paper also documents the altered development that occurred in this immature dog after the thrombotic event.  相似文献   
7.
New evidence is presented to support the contention that the amoeba/cyst colonies isolated from surface-sterilized Spongospora subterranea f.sp. subterranea -infected potato tubers and spore balls have a saprophytic phase but are contaminants and not S. subterranea. Amoebae isolated from infected tissues and spore balls formed colonies associated with bacteria on 1% water agar at 18°C and encysted after 5–7 days. These cysts were morphologically distinct from the resting spores of S. subterranea and were formed singly or in a layer, unlike the spore ball (cystosorus) of S. subterranea . Amoebae, cysts and mixtures of amoebae and cysts in primary, secondary and tertiary subcultures failed to infect tomato roots. PCR amplification of DNA from amoebae, cysts and spore balls using the S. subterranea -specific primer pair SsF/R generated a 434-bp product from S. subterranea spore balls only and not from amoebae or cysts. When an amoeba/cyst-specific primer pair AmF/R was designed and used for PCR amplification, a single 411-bp product was generated from DNA of amoebae and cysts, but not from DNA of S. subterranea spore balls. These results are discussed in relation to earlier reports claiming the successful isolation of S. subterranea and other plasmodiophorids in vitro .  相似文献   
8.
The diagnostic test for Tritrichomonas foetus in bulls is microscopic examination of cultured preputial samples. Trichomonads other than T. foetus can be present in a preputial sample. Both a staining technique and a polymerase chain reaction assay were useful in differentiating between T. foetus and another trichomonad observed in samples from virgin bulls.  相似文献   
9.
10.
Type I interferons (IFN) are important mediators of the host defense against viral infections in mammals. In humans multiple subtypes of IFN-alpha exist, most of which possess antiviral activity. Little is known about the type I IFN genes in cats and the role they may play in feline immunological responses to viruses. We have isolated cDNAs encoding five feline IFN-alpha (feIFN) subtypes that share from 95 to 99% amino acid sequence identity. FeIFN-alpha5 has five additional amino acids inserted at position 139, which are not present in the other four subtypes. Sequence identity of the feIFN proteins encoded by the five clones compared to human IFN-alpha2 is approximately 60%. Unlike most of the human subtypes, each of the five feline IFN sequences has an N-glycosylation recognition site. Expression of all five feIFN-alpha subtypes in Chinese hamster ovary (CHO) cells was confirmed by Western blot analysis, and all resulting proteins were glycosylated. The antiviral activity of each feIFN-alpha subtype produced in transiently transfected CHO cell cultures was tested in vitro. In addition, subtype feIFN-alpha6 was expressed in the yeast, Pichia pastoris. The resulting secreted mature recombinant protein was purified and demonstrated significant antiviral activity and induction of 2',5'-oligoadenylate synthetase activity in vitro.  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