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   10630篇
  免费   838篇
  国内免费   4篇
  11472篇
  2024年   5篇
  2023年   60篇
  2022年   174篇
  2021年   264篇
  2020年   152篇
  2019年   206篇
  2018年   252篇
  2017年   236篇
  2016年   327篇
  2015年   557篇
  2014年   605篇
  2013年   780篇
  2012年   981篇
  2011年   894篇
  2010年   596篇
  2009年   509篇
  2008年   666篇
  2007年   725篇
  2006年   665篇
  2005年   545篇
  2004年   544篇
  2003年   445篇
  2002年   433篇
  2001年   75篇
  2000年   58篇
  1999年   78篇
  1998年   93篇
  1997年   73篇
  1996年   58篇
  1995年   59篇
  1994年   30篇
  1993年   51篇
  1992年   32篇
  1991年   32篇
  1990年   19篇
  1989年   14篇
  1988年   15篇
  1987年   7篇
  1986年   11篇
  1985年   18篇
  1984年   16篇
  1983年   13篇
  1982年   17篇
  1981年   10篇
  1980年   10篇
  1979年   9篇
  1977年   9篇
  1976年   7篇
  1975年   5篇
  1974年   7篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.

Background  

Patients with acquired brain damage (ABD) have suffered a brain lesion that interrupts vital development in the physical, psychological and social spheres. Stroke and traumatic brain injury (TBI) are the two main causes. The objectives of this study were to estimate the incidence and prevalence of ABD in the population of the Basque Country and Navarre in 2008, to calculate the associated cost of the care required and finally to assess the loss in health-related quality of life.  相似文献   
12.
13.
Outside their cellular environments, hemoglobin (Hb) and myoglobin (Mb) are known to wreak oxidative damage. Using haptoglobin (Hp) and hemopexin (Hx) the body defends itself against cell-free Hb, yet mechanisms of protection against oxidative harm from Mb are unclear. Mb may be implicated in oxidative damage both within the myocyte and in circulation following rhabdomyolysis. Data from the literature correlate rhabdomyolysis with the induction of Heme Oxygenase-1 (HO-1), suggesting that either the enzyme or its reaction products are involved in oxidative protection. We hypothesized that carbon monoxide (CO), a product, might attenuate Mb damage, especially since CO is a specific ligand for heme iron. Low density lipoprotein (LDL) was chosen as a substrate in circulation and myosin (My) as a myocyte component. Using oxidation targets, LDL and My, the study compared the antioxidant potential of CO in Mb-mediated oxidation with the antioxidant potential of Hp in Hb-mediated oxidation. The main cause of LDL oxidation by Hb was found to be hemin which readily transfers from Hb to LDL. Hp prevented heme transfer by sequestering hemin within the Hp-Hb complex. Hemin barely transferred from Mb to LDL, and oxidation appeared to stem from heme iron redox in the intact Mb. My underwent oxidative crosslinking by Mb both in air and under N2. These reactions were fully arrested by CO. The data are interpreted to suit several circumstances, some physiological, such as high muscle activity, and some pathological, such as rhabdomyolysis, ischemia/reperfusion and skeletal muscle disuse atrophy. It appear that CO from HO-1 attenuates damage by temporarily binding to deoxy-Mb, until free oxygen exchanges with CO to restore the equilibrium.  相似文献   
14.

Purpose

Ischemic stroke has shown to induce platelet and endothelial microparticle shedding, but whether stroke induces microparticle shedding from additional blood and vascular compartment cells is unclear. Neural precursor cells have been shown to replace dying neurons at sites of brain injury; however, if neural precursor cell activation is associated to microparticle shedding, and whether this activation is maintained at long term and associates to stroke type and severity remains unknown. We analyzed neural precursor cells and blood and vascular compartment cells microparticle shedding after an acute ischemic stroke.

Methods

Forty-four patients were included in the study within the first 48h after the onset of stroke. The cerebral lesion size was evaluated at 3–7 days of the stroke. Circulating microparticles from neural precursor cells and blood and vascular compartment cells (platelets, endothelial cells, erythrocytes, leukocytes, lymphocytes, monocytes and smooth muscle cells) were analyzed by flow cytometry at the onset of stroke and at 7 and 90 days. Forty-four age-matched high cardiovascular risk subjects without documented vascular disease were used as controls.

Results

Compared to high cardiovascular risk controls, patients showed higher number of neural precursor cell- and all blood and vascular compartment cell-derived microparticles at the onset of stroke, and after 7 and 90 days. At 90 days, neural precursor cell-derived microparticles decreased and smooth muscle cell-derived microparticles increased compared to levels at the onset of stroke, but only in those patients with the highest stroke-induced cerebral lesions.

Conclusions

Stroke increases blood and vascular compartment cell and neural precursor cell microparticle shedding, an effect that is chronically maintained up to 90 days after the ischemic event. These results show that stroke induces a generalized blood and vascular cell activation and the initiation of neuronal cell repair process after stroke. Larger cerebral lesions associate with deeper vessel injury affecting vascular smooth muscle cells.  相似文献   
15.
Number representations change through education, although it is currently unclear whether and how language could impact the magnitude representation that we share with other species. The most prominent view is that language does not play any role in modulating the core numeric representation involved in the contrast of quantities. Nevertheless, possible cultural hints on the numerical magnitude representation are currently on discussion focus. In fact, the acquisition of number words provides linguistic input that the quantity system may not ignore. Bilingualism offers a window to the study of this question, especially in bilinguals where the two number wording systems imply also two different numerical systems, such as in Basque-Spanish bilinguals. The present study evidences linguistic prints in the core number representational system through the analysis of EEG oscillatory activity during a simple number comparison task. Gamma band synchronization appears when Basque-Spanish bilinguals compare pairs of Arabic numbers linked through the Basque base-20 wording system, but it does not if the pairs are related through the base-10 system. Crucially, this gamma activity, originated in a left fronto-parietal network, only appears in bilinguals who learned math in Basque and not in equivalent proficiency bilinguals who learned math in Spanish. Thus, this neural index reflected in gamma band synchrony appears to be triggered by early learning experience with the base-20 numerical associations in Basque number words.  相似文献   
16.
17.
18.
19.
Summary 2-Phenylethanol and 2-phenylethylacetate important aroma components are obtained in substantial amounts whenHansenula anomala CBS 110 andKloeckera saturnus CBS 5761 are grown with L-phenylalanine as sole nitrogen source. Up to 2 g/L of mixtures of alcohol and ester are obtained. While in the first microorganism the alcohol predominates, in the second the acetate is formed almost exclusively. Experiments with 1-13C-d-Glucose show complete incorporation of the label into the methyl group of the acetate.  相似文献   
20.
Photodynamic therapy (PDT) leads to production of reactive oxygen species (ROS) and cell destruction due to oxidative stress. We used photodynamic effect of photosensitizer radachlorin to unravel the effect of photo-induced oxidative stress on the calcium signal and lipid peroxidation in primary culture of cortical neurons and astrocytes using live cell imaging. We have found that irradiation in presence of 200 nM of radachlorin induces calcium signal in primary neurons and astrocytes. Photo-induced neuronal calcium signal depends on internal calcium stores as it was still observed in calcium-free medium and could be blocked by depletion of endoplasmic reticulum (ER) stores with inhibitor of sarco-endoplasmic reticulum Ca2+ ATPase (SERCA) thapsigargin. Both inhibitors of phospholipase C activity U73122 and water-soluble analogue of vitamin E Trolox suppressed calcium response activated by PDT. We have also observed that the photodynamic effect of radachlorin induces lipid peroxidation in neurons and astrocytes. This data demonstrate that lipid peroxidation induced by PDT in neurons and astrocytes leads to activation of phospholipase C that results in production of inositol 1,4,5-trisphosphate (IP3).  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