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   6854篇
  免费   3篇
电工技术   5篇
化学工业   82篇
金属工艺   6篇
机械仪表   17篇
建筑科学   15篇
能源动力   5篇
轻工业   40篇
水利工程   10篇
石油天然气   3篇
无线电   23篇
一般工业技术   32篇
冶金工业   6550篇
原子能技术   2篇
自动化技术   67篇
  2021年   4篇
  2019年   3篇
  2016年   2篇
  2015年   4篇
  2014年   8篇
  2013年   13篇
  2012年   15篇
  2011年   12篇
  2010年   9篇
  2009年   11篇
  2008年   13篇
  2007年   13篇
  2006年   12篇
  2005年   12篇
  2004年   13篇
  2003年   22篇
  2002年   10篇
  2001年   13篇
  2000年   8篇
  1999年   170篇
  1998年   1954篇
  1997年   1155篇
  1996年   764篇
  1995年   393篇
  1994年   362篇
  1993年   398篇
  1992年   54篇
  1991年   107篇
  1990年   105篇
  1989年   91篇
  1988年   103篇
  1987年   88篇
  1986年   80篇
  1985年   66篇
  1984年   3篇
  1983年   13篇
  1982年   32篇
  1981年   50篇
  1980年   61篇
  1978年   29篇
  1977年   185篇
  1976年   355篇
  1975年   14篇
  1973年   4篇
  1972年   2篇
  1970年   2篇
  1968年   2篇
  1967年   2篇
  1955年   4篇
  1954年   3篇
排序方式: 共有6857条查询结果,搜索用时 15 毫秒
81.
82.
This paper reports on the production of tumor necrosis factor (TNF) and granulocyte macrophage colony-stimulating factor (GM-CSF) by cultured mononuclear adherent cells derived from bone marrow of 25 patients affected by myelodysplastic syndrome (MDS) of different FAB subtypes. Mean production of GM-CSF was much lower than in controls, without significant differences among different subtypes. Mean production of TNF was similar in MDS patients and in controls, but noteworthy differences were observed between patients with RA, RAEB and RAEB-t and patients with RARS and CMML. Growth of bone marrow granulocyte macrophage and erythroid progenitors did not correlate with TNF and GM-CSF production, although in MDS subtypes with higher GM-CSF levels, colony growth was slightly higher than in subtypes with lower GM-CSF production.  相似文献   
83.
Breast implants     
We describe the case - to our knowledge unique - of an 8-year-old boy who presented with acute onset of lower cranial nerve palsy and tetraparesis caused by a hematoma in a dorsal exophytic pilocytic astrocytoma of the medulla oblongata. The boy showed near-complete recovery after neurosurgical management in two stages: first, emergency evacuation of the hematoma with tumor biopsy, and second, complete tumor removal 5 months after the initial event. Intraoperative electrophysiological monitoring techniques for the lower cranial nerves are of value in preserving their functional integrity. Ultrasonography is helpful in assessing the extent of tumor removal. Although the pathological diagnosis of a pilocytic astrocytoma would not justify radiotherapy, local field radiotherapy was added mainly because of the unexpectedly rapid tumor progression during the interval between the two surgical procedures. The literature on brainstem and tumor hematoma in children is reviewed.  相似文献   
84.
1. PD 81,723 has been shown to enhance binding of adenosine to A1 receptors by stabilizing G protein-receptor coupling ('allosteric enhancement'). Evidence has been provided that in the perfused hearts and isolated atria PD 81,723 causes a sensitization to adenosine via this mechanism. 2. We have studied the effect of PD 81,723 in guinea-pig isolated atrial myocytes by use of whole-cell measurement of the muscarinic K+ current (I[K(ACh)]) activated by different Gi-coupled receptors (A1, M2, sphingolipid). PD 81,273 caused inhibition of I[K(ACh)] (IC50 approximately 5 microM) activated by either of the three receptors. Receptor-independent I[K(ACh)] in cells loaded with GTP-gamma-S and background I[K(ACh)], which contributes to the resting conductance of atrial myocytes, were equally sensitive to PD 81,723. At no combination of concentrations of adenosine and PD 81,723 could an enhancing effect be detected. 3. The compound was active from the outside only. Loading of the cells with PD 81,723 (50 microM) via the patch pipette did not affect either I[K(ACh)] or its sensitivity to adenosine. We suggest that PD 81,723 acts as an inhibitor of inward rectifying K+ channels; this is supported by the finding that ventricular I(K1), which shares a large degree of homology with the proteins (GIRK1/GIRK4) forming I[K(ACh)] but is not G protein-gated, was also blocked by this compound. 4. It is concluded that the functional effects of PD 81,723 described in the literature are not mediated by the A1 adenosine receptor-Gi-I[K(ACh)] pathway.  相似文献   
85.
Acute, monophasic experimental allergic encephalomyelitis (EAE) in the Lewis rat shows pathological similarities to the human disease multiple sclerosis (MS). Rats that recover from EAE are essentially resistant to disease reinduction, unlike MS in which relapses are frequently associated with common bacterial and viral infections. As macrophage-derived interleukin (IL)-12 is a critical component of innate resistance to bacterial infection and appears to directly activate encephalitogenic T cells in vivo, the ability of this cytokine to reinduce paralysis in EAE was examined. Paralytic disease was exacerbated by intraperitoneal IL-12 administration and could be reinduced up to 1 week after recovery from the primary clinical episode. Concomitant with worsening of initial clinical signs and relapse was an increase in the ratio of macrophages to T cells in brain stem perivascular cuffs and the expression of inducible nitric oxide synthase in cells with both macrophage and microglial morphology. These findings suggest that IL-12 may contribute to macrophage-mediated disease exacerbation and relapse in patients with MS.  相似文献   
86.
87.
Host immunity to Epstein-Barr Virus Patterns of Epstein-Barr Virus latent gene expression in EBV posttransplantation lymphoproliferative disorders Cytokines network in posttransplantation lymphoproliferative disorders associated with EBV Lymphomagenesis and EBV Morphology and clonality of posttransplantation lymphoproliferative disorders associated with EBV Treatment of posttransplantation lymphoproliferative disorders associated with EBV.  相似文献   
88.
89.
90.
In recent years fracture fixation in the horse has changed significantly. New devices, mainly adapted from the human field, have been successfully introduced into large animal surgery. Examples of such implants include the DCS/DHS implant system, the self-tapping screw, the cannulated screw, and the pinless external fixator. However, new devices have also been developed exclusively for equine fracture management, including the interlocking intramedullary nail and the external skeletal fixation device. With these devices the surgeon has more options for repairing fractures in horses. Nevertheless, many problems are still unsolved. Indications exist that during the next few years new, exciting fracture fixation systems will be developed, providing further advancements in the quest for the ideal implant for horses. However, the development stages of these devices are such that mentioning the possibilities here is premature.  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