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   372篇
  免费   3篇
电工技术   1篇
化学工业   25篇
机械仪表   1篇
能源动力   7篇
轻工业   4篇
无线电   12篇
一般工业技术   6篇
冶金工业   313篇
自动化技术   6篇
  2022年   2篇
  2020年   4篇
  2019年   2篇
  2018年   1篇
  2017年   2篇
  2016年   2篇
  2013年   3篇
  2012年   1篇
  2009年   3篇
  2008年   5篇
  2007年   1篇
  2006年   1篇
  2005年   3篇
  2004年   1篇
  2002年   2篇
  2001年   1篇
  1999年   18篇
  1998年   96篇
  1997年   53篇
  1996年   32篇
  1995年   25篇
  1994年   11篇
  1993年   23篇
  1992年   3篇
  1991年   7篇
  1990年   7篇
  1989年   7篇
  1988年   7篇
  1987年   8篇
  1986年   2篇
  1985年   5篇
  1984年   2篇
  1983年   1篇
  1982年   1篇
  1981年   3篇
  1980年   3篇
  1978年   2篇
  1977年   4篇
  1976年   21篇
排序方式: 共有375条查询结果,搜索用时 15 毫秒
1.
On the basis of clinical signs and histological findings eight 9-month-old male rusa deer (Cervus timorensis) were diagnosed with sheep associated-malignant catarrhal fever. Following a variable course involving rectal temperatures around 40.5 degrees C, depression, inappetence, diarrhoea, corneal opacity and hypopyon all animals died or were euthanased over a 5-week period. Severe multifocal vasculitis, mainly periglomerular and in the arcuate vessels were consistent histological findings which in the past have been adequate to confirm clinical diagnosis of sheep associated-malignant catarrhal fever. A nested polymerase chain reaction test has been used to detect a sheep associated-malignant catarrhal fever PRC product, 238 base-pairs in size, in DNA extracted from lymphocyte preparations. The result supported the diagnosis of sheep associated-malignant catarrhal fever in these deer.  相似文献   
2.
3.
Since the advent of computed tomography (CT) traumatic intraventricular haemorrhage (IVH) has been diagnosed more often. It has reportedly been associated with a poor prognosis, but pure or solitary IVH is rare, suggesting that other lesions occurring concurrently with it may contribute to the poor outcome. In a series of 65 patients with severe head injury (GCS < or = 8), 14 (22%) had IVH on initial CT. Death rate in these 14 was 21%, not significantly different from that in patients without IVH (14%), although a significantly higher proportion of patients without IVH had a good outcome. These results suggest that mortality is related to other lesions associated with IVH rather than to IVH alone and that the presence of IVH does not necessarily lead to a poor outcome.  相似文献   
4.
We have investigated the role of the gonadal steroids testosterone (T) and progesterone in modulating: (1) the onset and severity of adjuvant-induced arthritis (AA), (2) the response of the hypothalamo-pituitary-adrenal (HPA) axis, and (3) the levels of plasma prolactin and anterior pituitary prolactin messenger ribonucleic acid (mRNA) in the rat. Male rats were castrated (CSX) and received either no T, low T or high T delivered using silastic implants. In a second study experimental groups comprised CSX/AA, CSX/AA + progesterone or CSX/AA + progesterone + T. The time of onset was sooner and the severity of AA was greater in CSX rats. Inflammation was prevented by T replacement. Endogenous plasma T levels were decreased in AA rats. In control animals with AA there was an increase in pro-opiomelanocortin (POMC) mRNA in the anterior pituitary and of plasma corticosterone, and a decrease in corticotrophin-releasing factor (CRF) mRNA. These changes in the HPA axis of AA and CSX/AA rats were reversed by T replacement. These data suggest that T has an important protective effect on the progress and severity of AA. This was reflected by a reversal of the neuroendocrine changes of the HPA axis. Progesterone treatment alone had no effect on the severity of the disease. Prolactin mRNA in the anterior pituitary was decreased in the CSX and in the CSX/AA group but was not altered by AA. Plasma prolactin was raised in AA but T replacement did not reduce these elevated levels despite the absence of disease. Thus, prolactin provides a poor indicator of inflammation, suggesting that it may not be a potent pro-inflammatory compound in AA.  相似文献   
5.
Nasopharyngeal stenosis and oropharyngeal stenosis are rare and challenging problems in the pediatric population. The most common etiology is currently the surgical trauma associated with adenotonsillectomy. Stenosis can vary from a thin band to a complete obstructing cicatrix. Presenting symptoms range from mild hyponasal speech to severe airway obstruction. We present a series of eight children with varying degrees of stenosis and associated symptoms. Choice of treatment varied with the severity of disease. In our series, successful interventions included triamcinolone acetonide injection, lysis of adhesions, rotational and advancement mucosal flaps, and jejunal free flap. Preoperative evaluation and individualized surgical repair are essential for successful treatment.  相似文献   
6.
7.
Neurotransmitter receptor plasticity is an important part of the compensatory processes by which the central nervous system adapts to pathological insult, long-term exposure to drugs or neuronal loss with advanced age. Receptor plasticity can be manifest as changes in the number of receptors (i.e., up- or down-regulation), changes in expression of mRNA for discrete receptor proteins, or alterations in receptor coupling to signal transduction systems. Evidence exists for impaired plasticity of neurons in the aged brain, which results in decreased ability to adjust to changes in their environment. However, such data are highly dependent on the neurotransmitter examined, the stimulus for receptor regulation and the animal model chosen for study. For example, senescent rats show an age-related impairment of muscarinic receptor up- or down-regulation after long-term exposure to cholinergic drugs. Thus, young rats exposed to chronic (three weeks) intracerebroventricular infusions of methylatropine or oxotremorine exhibit compensatory changes in the density of muscarinic receptors in frontal cortex and hypothalamus. In contrast, 3H-QNB binding is unaltered in the same brain regions of identically treated senescent rats. Similar observations of impaired muscarinic receptor plasticity in senescent animals have been confirmed by other investigators. Age-related differences in coupling of brain muscarinic receptors to G-proteins and in muscarinic receptor-stimulated phosphoinositide hydrolysis have also been reported. Interestingly, neuropeptides such as neurotensin, cholecystokinin and VIP can potentiate carbachol-stimulated phosphoinositide hydrolysis in frontal cortex of both young and aged rats. This adds another level at which cholinergic neurotransmission may be modulated in senescent animals. Potential age-related differences in the effects of chronic drug treatments or experimental brain lesions on muscarinic receptor coupling to second messenger systems or on expression of mRNA for particular muscarinic receptors are currently unknown. Hence, it is possible that senescent animals may show additional deficiencies in plasticity of muscarinic receptor mediated signal transduction or expression of muscarinic receptors subtypes.  相似文献   
8.
A series of experiments was conducted under controlled soil moisture and temperature conditions in a growth chamber to examine the effect of a range of nutrient seed coatings on the emergence to wheat (Triticum aestivum L. cv. Kite) and oats (Avena sativa L. cv. Blackbutt) sown in a coarse sandy loam soil. Final emergence of oats was not reduced by a coating containing 10 kg P ha–1 (as monocalcium phosphate [MCP]) whereas the same coating reduced wheat emergence by 15%. The emergence of both wheat and oats was severely reduced by urea coatings (supplying 10 kg N ha–1) to 33 and 13% respectively; this injury was lessened markedly by the inclusion of phenyl phosphorodiamidate (PPD) in the urea coatings at 1% (w/w) (emergence increased to 66 and 56% respectively).Low soil moisture (67% of field capacity [FC]) resulted in almost no emergence of wheat coated with urea (± bentonites of different pH). In soil at FC, the addition of bentonite of pH 5 (B5) to urea coatings permitted greater emergence (54%) than when bentonite of pH 9 (B9) was added (32%) which, in turn, permitted greater emergence than urea coating alone (10%). When PPD and bentonite (B5 or B9) were combined either singly or together with urea in seed coatings, PPD was more effective than either of the bentonites in reducing injury and masked the slight positive effect of B5.Coatings containing various combinations of N and P sources (at 3.6 and at 8 kg ha–1 respectively) all reduced the emergence of wheat compared to raw seed (91% emergence). When applied alone, MCP was least damaging (74%); the combination of MCP with ammonium sulfate (AS) caused somewhat more injury (68%) whilst combination with calcium nitrate (CN) caused most injury (29%). In contrast, CN alone caused relatively little damage (73%) whilst AS alone was more damaging (50%). There was no significant regression found between percentage emergence and either the calculated partial salt index or the pH of the nutrient coatings. Further work is needed to examine the mechanisms of injury due to nutrient seed coatings so that safe but effective formulations can be developed.  相似文献   
9.
Information about place and location is an essential part ofresearch in the humanities. There are many ways that methodsand tools for structuring, visualizing and analysing space,spatial behaviour, and spatial relationships can benefit humanitiesresearch but the use of spatial information in digital scholarshipby humanists remains very limited. The developing role of thestudy of place and location through geographical informationsystems (GIS) and other digital tools is discussed briefly beforeexamining the factors that are inhibiting the use of spatialdata in our research. The influences of current research practiceand the attitudes of scholarly institutions in the humanitiesare examined. This article will explore some of the potentialresearch applications but, possibly more importantly; it willalso examine why that potential is being developed so slowlyand discuss a possible way forward for the community.  相似文献   
10.
Gaucher's disease is a lysosomal storage disease in which cells of the reticuloendothelial system accumulate the lipid glucocerebroside. It is characterized by slowly progressive visceral and osseous involvement. One of the latter manifestations includes lipid infiltration of bone marrow. We monitored the rate of inhaled 133Xe uptake and wash-out over diseased and normal metaphyseal and epiphyseal areas of the knee. Twenty-two patients (15 adults, 7 children) with various degrees of previously diagnosed Gaucher's disease were positioned supine under a gamma-camera interfaced to a computer system. All patients rebreathed 133Xe gas from a closed system for 10 min followed by 14 min of wash-out. Digitized images of the lung, liver, spleen, bony sites and soft tissue were obtained at 1 min intervals during the wash-in and wash-out phases. Counts for each ROI were normalized per 100 pixels and plotted as a function (time). Maximum uptake was also calculated by relating the counts/ROI/100 pixels to the 10 min integrated lung count during equilibrium (the administered "dose"). There was essentially no 133Xe uptake in liver and spleen involved with Gaucher's disease. Monophasic uptake and biphasic wash-out curves were observed in the limited investigative population. Skeletal Gaucher deposits released the 133Xe at a greater rate relative to soft tissue.  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