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   266篇
  免费   5篇
  国内免费   2篇
电工技术   2篇
综合类   2篇
化学工业   19篇
金属工艺   3篇
机械仪表   4篇
建筑科学   4篇
能源动力   1篇
轻工业   17篇
石油天然气   9篇
无线电   21篇
一般工业技术   17篇
冶金工业   160篇
原子能技术   4篇
自动化技术   10篇
  2023年   3篇
  2022年   9篇
  2021年   6篇
  2020年   2篇
  2019年   3篇
  2018年   3篇
  2017年   2篇
  2016年   6篇
  2015年   3篇
  2014年   5篇
  2013年   2篇
  2012年   5篇
  2011年   4篇
  2010年   2篇
  2009年   6篇
  2008年   1篇
  2007年   2篇
  2006年   7篇
  2005年   1篇
  2003年   5篇
  2002年   1篇
  2001年   2篇
  2000年   2篇
  1999年   5篇
  1998年   53篇
  1997年   28篇
  1996年   24篇
  1995年   10篇
  1994年   10篇
  1993年   9篇
  1992年   3篇
  1991年   4篇
  1990年   4篇
  1989年   3篇
  1988年   5篇
  1987年   2篇
  1986年   2篇
  1981年   2篇
  1980年   1篇
  1977年   5篇
  1976年   20篇
  1975年   1篇
排序方式: 共有273条查询结果,搜索用时 15 毫秒
1.
2.
Two once-daily electroconvulsive shocks (ECS) produced retrograde amnesia in rats trained on a Hebb-Williams maze; Verapamil (12.5 mg/kg, i.p.) or felodipine (10 mg/kg, p.o.) administered half an hour before each ECS attenuated this ECS-induced amnesia. Hence, these drugs may hold promise for the containment of amnesia induced by electroconvulsive therapy (ECT). Speculatively, one or more of several mechanisms may be involved: cerebral vasodilatation, enhancement of cholinergic tone, and inhibition of calcium-mediated impairment of neuronal function. These drugs may also act by attenuating the systolic surge in blood pressure during ECT, thereby decreasing edema due to cerebral hyperperfusion, as well as decreasing the possible transfer of potentially neurotoxic macromolecules through a putative breach in the blood-brain barrier.  相似文献   
3.
Homozygous and hemizygous deletions of 9p21 are the earliest and most common genetic alteration in bladder cancer. The identification of two cell cycle regulators, CDKN2 and CDKN2B, that map to the common region of deletion has prompted the hypothesis that they are critical tumor suppressor genes in this malignancy. However, controversy as to whether these genes are the only or even the most important target in bladder cancer oncogenesis remains. To more clearly determine the effect of these 9p21 alterations, we mapped the homozygous deletions and performed a detailed mutational and expression analysis for CDKN2, CDKN2B and a closely linked gene, methylthioadenoside phosphorylase (MTAP), in 16 established bladder cancer cell lines. Nine of the 16 lines exhibit large (30 to > 2000 kb) homozygous deletions on 9p21. All deletions include at least one exon of CDKN2, eight of nine include CDKN2B, and six of nine include MTAP. MTAP function correlates with the genomic deletions. SSCP and sequence analysis does not reveal any inactivating point mutations of CDKN2 or of CDKN2B in any of the cell lines without homozygous deletions, and all express the CDKN2 and the CDKN2B mRNA as well as the encoded p16 protein. The p16 protein levels vary widely and are correlated with absent pRb expression. We conclude that the 9p21 deletions in bladder cancer usually inactivate the CDKN2. CDKN2B, and MTAP genes but that CDKN2 is the most common target. Other mechanisms for inactivating this gene in bladder cancer appear to be uncommon.  相似文献   
4.
5.
Fifty-eight new anonymous simple sequence repeats (SSR) were generated and mapped to various rat chromosomes. Among them two genes (rat homologs for human cadherin-14 and mouse fibroblast growth factor-related protein) were mapped on Chromosomes (Chrs) 2 and 11 respectively. The majority of markers were generated from a small insert genomic library specific to Chr 11, 13, 14, and 15. Twenty new markers were mapped to Chr 13, which is known to contain a blood pressure quantitative trait locus (QTL). Several approaches to obtain microsatellite markers are described. The protocols and newly generated markers should be useful for ongoing rat genome project.  相似文献   
6.
A favourable effect of sanatorium treatment on the key body functions was found in children with thyroid hyperplasia consequent to environmental pollution due to Chernobyl accident. It is emphasized that balneofactors in the above children should be used in sparing regimens.  相似文献   
7.
Some mechanical and electrical properties of the BPDA/ODA/PDA polyimide film prepared on mylar followed by various cure schedules have been studied. It has been found by FTIR that the imidization reaches its maximum after a 200°C cure schedule for this polyimide. However, the optimum condition of curing is a 350°C cure schedule. Following this cure schedule, one can obtained a polymide film with good mechanical and electrical properties. © 1993 John Wiley & Sons, Inc.  相似文献   
8.
本文通过介绍数字信号处理器(DSP)的特点和应用,指出了在高等院校学生实验中引入数字信号处理器的必要性,并且给出了基于数字信号处理器的实验系统构建。  相似文献   
9.
The harsh melt-spinning and annealing processes of high saturation magnetization nanocrystalline softmagnetic alloys are the biggest obstacles for their industrialization. Here, we proposed a novel strategy to enlarge the processing window by annealing the partially crystallized precursor ribbons via a heterostructured crystallization process. The heterostructured evolution of Fe84.75Si2B9P3C0.5Cu0.75(at.%)alloy ribbons with different spinning rate were studied in detail, to demonstrate the gradient nucleation and grain refinement mechanisms. The nanocrystalline alloys made with industrially acceptable spinning rate of 25-30 m/s and normal annealing process exhibit excellent magnetic properties and fine nanostructure. The small quenched-in crystals/clusters in the free surface of the low spinning rate ribbons will not grow to coarse grains, because of the competitive grain growth and shielding effect of metalloid elements rich interlayer with a high stability. Avoiding the precipitation of quenched-in coarse grains in precursor ribbons is thus a new criterion for the composition and process design, which is more convenient than the former one with respect to the homogenous crystallization mechanism, and enable us to produce high performance nanocrystalline soft-magnetic alloys. This strategy is also suitable for improving the compositional adjustability, impurity tolerance, and enlarging the window of melt temperature,which is an important reference for the future development of composition and process.  相似文献   
10.
The most frequent cause of death by cancer worldwide is lung cancer, and the 5-year survival rate is still very poor for patients with advanced stage. Understanding the crosstalk between the signaling pathways that are involved in disease, especially in metastasis, is crucial to developing new targeted therapies. Toll-like receptors (TLRs) are master regulators of the immune responses, and their dysregulation in lung cancer is linked to immune escape and promotes tumor malignancy by facilitating angiogenesis and proliferation. On the other hand, over-activation of the WNT signaling pathway has been reported in lung cancer and is also associated with tumor metastasis via induction of Epithelial-to-mesenchymal-transition (EMT)-like processes. An interaction between both TLRs and the WNT pathway was discovered recently as it was found that the TLR pathway can be activated by WNT ligands in the tumor microenvironment; however, the implications of such interactions in the context of lung cancer have not been discussed yet. Here, we offer an overview of the interaction of TLR-WNT in the lung and its potential implications and role in the oncogenic process.  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