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   282篇
  免费   8篇
林业   16篇
农学   9篇
基础科学   1篇
  82篇
综合类   18篇
农作物   6篇
水产渔业   12篇
畜牧兽医   124篇
园艺   6篇
植物保护   16篇
  2023年   2篇
  2022年   1篇
  2021年   1篇
  2020年   6篇
  2019年   7篇
  2018年   6篇
  2017年   4篇
  2016年   5篇
  2015年   7篇
  2014年   9篇
  2013年   19篇
  2012年   14篇
  2011年   28篇
  2010年   9篇
  2009年   9篇
  2008年   25篇
  2007年   15篇
  2006年   14篇
  2005年   21篇
  2004年   21篇
  2003年   15篇
  2002年   11篇
  2001年   5篇
  1999年   3篇
  1998年   2篇
  1997年   2篇
  1996年   2篇
  1994年   2篇
  1993年   3篇
  1992年   3篇
  1991年   1篇
  1990年   2篇
  1989年   1篇
  1988年   1篇
  1986年   1篇
  1985年   2篇
  1980年   3篇
  1979年   1篇
  1978年   1篇
  1972年   1篇
  1961年   2篇
  1959年   1篇
  1958年   1篇
  1956年   1篇
排序方式: 共有290条查询结果,搜索用时 232 毫秒
281.
Fructosamine   总被引:3,自引:0,他引:3  
Fructosamines are glycated serum proteins that, depending on their life span, reflect glycemic control over the previous 2 to 3 weeks. The nitroblue tetrazolium reduction method adapted to autoanalysis appeared to be a practical means to assay fructosamine quickly, economically, and accurately. The upper limit of the reference range is 374 μmol/L in dogs (95% percentile) and 340 μmol/L in cats (95% percentile). Newly diagnosed diabetic dogs and cats that had not undergone previous insulin therapy had significantly higher fructosamine concentrations than nondiabetic animals. In diabetic dogs that were receiving insulin therapy, the fructosamine test reflected the glycemic state far more accurately than did individual blood glucose measurements. Animals with satisfactory metabolic control revealed fructosamine concentrations within the reference range, whereas fructosamine concentrations above 400 μmol/L indicated insufficient metabolic control. On the basis of fructosamine concentrations, cats with a transitory hyperglycemia and cats with diabetes mellitus were differentiated. The fructosamine test is a valuable parameter for the diagnosis and metabolic control of diabetes mellitus in dogs and cats.  相似文献   
282.
Bovine leukemia virus (BLV) induces a persistent infection in the B-cells causing polyclonal expansion of B-cells in one-third of infected cattle and lymphosarcoma in less than 5% of infected cattle. While BLV is difficult to detect in vivo, it is readily produced by cultured lymphocytes and is diminished when supplemented by bovine plasma. This phenomenon is attributed to a poorly characterized plasma blocking factor (PBF). We assessed the effects of bovine plasma on cell viability and BLV p24 expression, and the effects of purified PBF on protein synthesis and gene expression of short-term cultures of bovine lymphocytes. The addition of 25% plasma or semi-purified PBF to cultures had no significant effect on cell viability but caused significant decreases in BLV p24 production and significantly increased de novo protein synthesis. Utilizing a human microarray, the RNA messages of 83 genes involved in cell division, cell metabolism, and gene regulation were up-regulated.  相似文献   
283.
284.
The pathomechanism in human pemphigus vulgaris (PV) has recently been described to rely on generalized c-Myc upregulation in skin and oral mucosa followed by hyperproliferation. Here we assessed whether dogs suffering from PV present the same pathological changes as described for human patients with PV. Using immunofluorescence analysis on patients' biopsy samples, we observed marked nuclear c-Myc accumulation in all layers of the epidermis and oral mucosa in all (3/3) dogs analysed. In addition, c-Myc upregulation was accompanied by an increased number of proliferating Ki67-positive cells. These molecular changes were further paralleled by deregulated expression of wound healing and terminal differentiation markers as observed in human PV. Together these findings suggest a common pathomechanism for both species which is of particular relevance in the light of the recently discussed novel therapeutic strategies aiming at targeting PV antibody-induced signalling cascades.  相似文献   
285.
OBJECTIVE: Recombinant feline interferon omega (rFeIFN-omega), a type I IFN, may have the potential to limit virus replication and associated clinical signs when administered early on in the course of feline herpesvirus type 1 (FHV-1) infection and reactivation, respectively. The effect of rFeIFN-omega pretreatment on the course of subsequent FHV-1 infection in cats was investigated. ANIMALS STUDIED: Nine SPF cats were divided into an IFN group (n = 5) and a control-group (n = 4). PROCEDURES: The IFN group was pretreated for 2 days with 10 000 units rFeIFN-omega twice a day topically into both eyes and 20 000 units rFeIFN-omega once a day orally, whereas the control group was mock-treated. Subsequently all cats were infected with FHV-1. Samples for FHV-1 DNA detection and quantitation, virus isolation, and titration of FHV-1 antibodies were collected. Clinical and ocular signs were recorded and scored. RESULTS: Courses of median individual clinical and ocular scores and virus load did not differ significantly between both groups using anova for repeated measurements. Analysis (anova) of each individual ocular parameter revealed significantly high scores for epithelial keratitis (P = 0.016) in the IFN group compared to the control group. Periods of virus shedding did not differ significantly between both groups using the Wilcoxon rank sum test. CONCLUSIONS: Results indicated a lack of beneficial effects of rFeIFN-omega pretreatment in the course of primary FHV-1 infection in cats.  相似文献   
286.
蔬菜中铅镉铜锌含量的影响因素研究   总被引:48,自引:13,他引:48  
用通过大田调查的方法,研究了影响蔬菜中Pb、Cd、Cu、Zn含量的因素。结果表明:(1)蔬菜对Pb、Cd、Cu、Zn的富集可分为高富集、中富集和低富集,针对不同的土壤污染程度,可以选择不同富集系数的蔬菜种植;(2)提高土壤pH值,有助于降低蔬菜中Pb、Cd、Cu、Zn的含量;调节土壤阳离子交换量、有机质含量和粘粒含量应注意适度,过高会导致相反的结果;(3)土壤Pb、Cd、Cu、Zn之间的相互关系较为复杂,Cu与Zn之间具有相互的拮抗作用,Cu对Pb的吸收具有促进作用。  相似文献   
287.

The multicolored Asian ladybeetle, Harmonia axyridis Pallas (Col, Coccinellidae), is recognized as one of the most invasive insects in the world. It has reduced the native coccinellids populations in several areas, and it is considered a threat for biodiversity at large. A significant trait, favoring its invasiveness and its dominance over indigenous ladybeetles, is intraguild predation (IGP). IGP has advantageous adaptive value for individuals: removing competitors and potential predators, and providing an alternative nutritive resource when main resources are scarce. IGP can be affected by several factors, but little is known about the effect of pesticides on this behavior. Previous research demonstrated that the invasive Asian ladybeetle is highly susceptible to the reduced-risk insecticide novaluron, a chitin synthesis inhibitor, whereas the North American indigenous competitor, Coleomegilla maculata DeGeer (Col, Coccinellidae), is not. Our study explores the adaptive value of IGP for each of the two coccinellids after preying on each other’s larvae, which were previously treated with insecticide. Our first hypothesis is that the invasive ladybeetle, susceptible to the insecticide, should lose the adaptive value of IGP. Our second hypothesis is that the adaptive value of IGP for the invasive predator will recover over time, because of neutralization of the insecticide by the intraguild prey. The results confirm both hypotheses and show that an insecticide can completely remove the adaptive value of IGP for the invader, while the adaptive value of IGP does not change for the indigenous ladybeetle. Moreover, the study demonstrates that if the intraguild prey (non-susceptible to the insecticide) undergoes molt after being exposed to the insecticide, the adaptive value for the intraguild predator is restored.

  相似文献   
288.
Changes in potato starch quality during growth   总被引:2,自引:0,他引:2  
Summary Potato starch quality parameters (amylose concentration, glucose-6-phosphate content and granule size) were analyzed in relation to the harvesting date and tuber size of four cultivars. A significant increase in the glucose-6-phosphate content and granule size of starch was observed during tuber growth, whereas the amylose concentration was constant. Granule size increased markedly, whereas glucose-6-phosphate content showed slightly increasing values with increasing tuber size. Amylose concentration showed no correlation with tuber size. We conclude that the changes in the granule size, glucose-6-phosphate and amylose content of potato starch during growth are independent of each other.  相似文献   
289.
As the interface between hippocampus and neocortex, the entorhinal cortex is likely to play a pivotal role in memory. To determine how information is represented in this area, we measured spatial modulation of neural activity in layers of medial entorhinal cortex projecting to the hippocampus. Close to the postrhinal-entorhinal border, entorhinal neurons had stable and discrete multipeaked place fields, predicting the rat's location as accurately as place cells in the hippocampus. Precise positional modulation was not observed more ventromedially in the entorhinal cortex or upstream in the postrhinal cortex, suggesting that sensory input is transformed into durable allocentric spatial representations internally in the dorsocaudal medial entorhinal cortex.  相似文献   
290.
In 2006, bluetongue (BT) virus serotype 8 emerged in northern Europe and numerous ruminants were affected in the following year. Infertility in males is one of the consequences of BT, although its severity and duration after natural infection has not been documented. In this report, the impact of BT-8 on clinical signs and semen quality of naturally infected rams is described through a longitudinal study of two Belgian ram populations (n = 12 and n = 24) and a cross sectional study in a further ram population (n = 43).Macroscopic semen characteristics, semen concentration, motility, percentage of living and dead spermatozoa were assessed in 167 semen samples collected on 1–6 occasions from 79 BT-8 infected rams within 5–138 days after onset of clinical disease. These were compared with healthy control animals. Significant changes in all variables were observed after natural BT-8 infection. Total recovery occurred around 85 days after clinical disease in animals undergoing a close follow-up of semen quality. Good correspondence between the results of the longitudinal and cross sectional studies suggests that semen quality of BT-8 affected rams reached normal references values 63–138 days after clinical diagnosis of BT. In addition, semen concentration seems to be a sound epidemiological indicator of ram semen quality.  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