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   871篇
  免费   37篇
电工技术   2篇
化学工业   168篇
金属工艺   10篇
机械仪表   8篇
建筑科学   36篇
矿业工程   9篇
能源动力   27篇
轻工业   145篇
水利工程   10篇
石油天然气   7篇
无线电   39篇
一般工业技术   113篇
冶金工业   255篇
原子能技术   4篇
自动化技术   75篇
  2023年   4篇
  2022年   12篇
  2021年   23篇
  2020年   13篇
  2019年   20篇
  2018年   11篇
  2017年   18篇
  2016年   21篇
  2015年   16篇
  2014年   27篇
  2013年   43篇
  2012年   32篇
  2011年   49篇
  2010年   35篇
  2009年   56篇
  2008年   45篇
  2007年   31篇
  2006年   28篇
  2005年   33篇
  2004年   31篇
  2003年   38篇
  2002年   27篇
  2001年   17篇
  2000年   19篇
  1999年   13篇
  1998年   6篇
  1997年   19篇
  1996年   12篇
  1995年   14篇
  1994年   14篇
  1993年   20篇
  1992年   16篇
  1990年   7篇
  1989年   15篇
  1988年   13篇
  1987年   11篇
  1986年   8篇
  1985年   10篇
  1984年   4篇
  1983年   7篇
  1982年   8篇
  1981年   5篇
  1980年   5篇
  1979年   5篇
  1978年   9篇
  1977年   5篇
  1976年   7篇
  1975年   5篇
  1974年   3篇
  1964年   3篇
排序方式: 共有908条查询结果,搜索用时 31 毫秒
31.
An association between varicella zoster virus (VZV) and multiple sclerosis (MS) has been reported in Mexican populations. The aim of this study was to compare the response of T cells from MS patients, during relapse and remission, to in vitro stimulation with VZV, adenovirus (AV) and Epstein–Barr virus (EBV). Proliferation and cytokine secretion of T cells from 29 relapsing-remitting MS patients and 38 healthy controls (HC) were analyzed by flow cytometry after stimulating with VZV, AV or EBV. IgG and IgM levels against VZV and EBV were quantified using Enzyme-Linked Immunosorbent Assay. Relapsing MS patients showed a higher percentage of responding CD4+ and CD8+ T cells against VZV compared to AV. In HC and remitting MS patients, proliferation of CD4+ T cells was higher when stimulated with VZV as compared to EBV. Moreover, T cells isolated from remitting patients secreted predominantly Th1 cytokines when cell cultures were stimulated with VZV. Finally, high concentration of anti-VZV IgG was found in sera from patients and controls. The results support previous studies of an VZV-MS association in the particular population studied and provide additional information about the possible role of this virus in the pathogenesis of MS.  相似文献   
32.
HIV-Associated neurocognitive disorder (HAND) is one of the major concerns since it persists in 40% of this population. Nowadays, HAND neuropathogenesis is considered to be caused by the infected cells that cross the brain–blood barrier and produce viral proteins that can be secreted and internalized into neurons leading to disruption of cellular processes. The evidence points to viral proteins such as Tat as the causal agent for neuronal alteration and thus HAND. The hallmarks in Tat-induced neurodegeneration are endoplasmic reticulum stress and mitochondrial dysfunction. Sirtuins (SIRTs) are NAD+-dependent deacetylases involved in mitochondria biogenesis, unfolded protein response, and intrinsic apoptosis pathway. Tat interaction with these deacetylases causes inhibition of SIRT1 and SIRT3. Studies revealed that SIRTs activation promotes neuroprotection in neurodegenerative diseases such Alzheimer’s and Parkinson’s disease. Therefore, this review focuses on Tat-induced neurotoxicity mechanisms that involve SIRTs as key regulators and their modulation as a therapeutic strategy for tackling HAND and thereby improving the quality of life of people living with HIV.  相似文献   
33.
1. Background The use of engineering tools, design, research, and thinking to create environments and capabilities whereby individuals who are currently under-e...  相似文献   
34.
The operation of the mid-wave infrared (MWIR) HgCdTe cylindrical electron injection avalanche photodiode (e-APD) is described. The measured gain and excess noise factor are related to the collection region fill factor. A two-dimensional diffusion model calculates the time-dependent response and steady-state pixel point spread function for cylindrical diodes, and predicts bandwidths near 1 GHz for small geometries. A 2 μm diameter spot scan system was developed for point spread function and crosstalk measurements at 80 K. An electron diffusion length of 13.4 μm was extracted from spot scan data. Bandwidth data are shown that indicate bandwidths in excess of 300 MHz for small unit cells geometries. Dark current data, at high gain levels, indicate an effective gain normalized dark density count as low as 1000 counts/μs/cm2 at an APD gain of 444. A junction doping profile was determined from capacitance–voltage data. Spectral response data shows a gain-independent characteristic.  相似文献   
35.
对CIO们而言,制订一个灵活的继任者计划,帮助公司培养未来IT领导人。直接关乎自己职业宏图的拓展。毕竟,在没有得到一个足够优秀的人才来接替你的工作之前,CEO怎么会将你调任到其他新岗位呢?  相似文献   
36.
Canadian photographer Richard Harrington has been recognised since the 1950s for his photographs of the Arctic, and specifically for portraits of the Padleimiut taken at a hunting camp in 1950 during a winter of acute shortages. Three were selected for Edward Steichen’s The Family of Man (1955). Of that group, two focused on motherhood through depictions of childbirth and maternal love; the latter is sometimes referred to as ‘Canada’s Madonna and Child’, making a timeless secular icon from the representation of a crisis. Harrington was a documentary photographer who made his living as a freelance photojournalist specialising in human interest stories and travel features for magazines and newspapers. On assignment in British Columbia for the Hudson’s Bay Company magazine The Beaver, he photographed a First Nations mother and child, an image entitled ‘Madonna of the Peace’. This photograph later graced the cover of a Roman Catholic missionary magazine, Pôle et Tropiques. This article draws parallels between Harrington’s photographs of Indigenous mothers and children and Dorothea Lange’s Migrant Mother, using Harrington’s diaries and community-based research to reconstruct the lives of his subjects, and considering the sacrifice of knowledge to iconicity.  相似文献   
37.
Synthesis of nano photocatalysts, LaFeO3 with orthorhombic perovskite structure by sol–gel auto-combustion method was demonstrated. The samples were characterized by PXRD, SEM, HRTEM, XPS and optical absorption studies. Photocatalytic water decomposition over LaFeO3 nanoparticles activated at various temperatures without any co-catalyst were investigated under visible light irradiation (λ >> 420 nm). Highest amount of H2 and O2 evolved in 180 min over the LaFeO3 activated at 500 °C was recorded to be 1290 μmol and 640 μmol, respectively having apparent quantum efficiency (AQE) 8.07%. The pronounced activity of nano LaFeO3 samples towards water decomposition was consistent with BET-surface area and particle size analyses.  相似文献   
38.
Peter Wambura  Martha Verghese 《LWT》2011,44(10):2173-2179
While the efficacy of PUV-light on microbial inactivation is well documented, its effect on product quality is not well studied. Thus the effect of PUV-light on color, texture and oxidative stability of ham was evaluated. Samples of 100 g raw ham (~5 mm thick) were treated for 60, 90 and 120 s in a UV-light system. Another 100 g of untreated sample was used as a control. The distance from the lamp central axis was varied at 4.5, 8.3 and 14.6 cm. Results showed that the oxidative stability of the control, 4.5 cm/60 s, 4.5 cm/90 s, 4.5 cm/120 s, 8.3 cm/60 s, 8.3 cm/90 s, 8.3 cm/120 s, 14.6 cm/60 s, 14.6 cm/90 s, and 14.6 cm/120 s sample decreased by 21, 67, 53, 54, 39, 71, 75, 56, 58, and 55% respectively after 14 days of storage. Oxidative stability reduction was higher as treatment time was prolonged, but decreased with increased distance from the lamp. Overall, the color and texture of the samples were inversely affected by treatment time and distance of the sample from the lamp. Although PUV-light has a potential to decontaminate food products, this study demonstrated that quality of the product is concurrently compromised.  相似文献   
39.
The role of docosahexaenoic acid in retinal function   总被引:3,自引:0,他引:3  
An important role for docosahexaenoic acid (DHA) within the retina is suggested by its high levels and active conservation in this tissue. Animals raised on n-3-deficient diets have large reductions in retinal DHA levels that are associated with altered retinal function as assessed by the electroretinogram (ERG). Despite two decades of research in this field, little is known about the mechanisms underlying altered retinal function in n-3-deficient animals. The focus of this review is on recent research that has sought to elucidate the role of DHA in retinal function, particularly within the rod photoreceptor outer segments where DHA is found at its highest concentration. An overview is also given of human infant studies that have examined whether a neonatal dietary supply of DHA is required for the normal development of retinal function.  相似文献   
40.
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