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   9763篇
  免费   1629篇
  国内免费   1190篇
电工技术   788篇
技术理论   1篇
综合类   1552篇
化学工业   269篇
金属工艺   133篇
机械仪表   836篇
建筑科学   532篇
矿业工程   227篇
能源动力   164篇
轻工业   290篇
水利工程   204篇
石油天然气   138篇
武器工业   70篇
无线电   1566篇
一般工业技术   896篇
冶金工业   127篇
原子能技术   48篇
自动化技术   4741篇
  2024年   37篇
  2023年   128篇
  2022年   219篇
  2021年   274篇
  2020年   354篇
  2019年   252篇
  2018年   256篇
  2017年   304篇
  2016年   346篇
  2015年   459篇
  2014年   616篇
  2013年   621篇
  2012年   742篇
  2011年   828篇
  2010年   691篇
  2009年   687篇
  2008年   757篇
  2007年   819篇
  2006年   690篇
  2005年   596篇
  2004年   490篇
  2003年   426篇
  2002年   344篇
  2001年   296篇
  2000年   253篇
  1999年   199篇
  1998年   163篇
  1997年   125篇
  1996年   139篇
  1995年   101篇
  1994年   85篇
  1993年   54篇
  1992年   57篇
  1991年   27篇
  1990年   30篇
  1989年   32篇
  1988年   19篇
  1987年   15篇
  1986年   9篇
  1985年   15篇
  1984年   4篇
  1983年   9篇
  1982年   2篇
  1981年   1篇
  1980年   4篇
  1979年   2篇
  1978年   2篇
  1976年   1篇
  1974年   1篇
  1951年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
在简要介绍多变量模糊系统的模糊穴-穴映射(FCM-I)模型的基础上,提出了一种对多变量模糊系统进行分解的方法。此法的核心在于认为任何复杂系统的动态都是由其隐含的稳定子动态和不稳定于动态聚合而成,而系统特性则主要取决于决定性子动态的性质。并介绍了确定系统决定性子动态和基于其上的多变量模糊系统渐近分析方法。  相似文献   
992.
To evaluate the ability of MR T2 mapping (8.5 T) to characterize ex vivo longitudinally, morphologically and quantitatively, alginate-based tissue engineering in a rat model of patellar cartilage chondral focal defect. Calibrated rat patellar cartilage defects (1.3 mm) were created at day 0 (D0) and alginate sponge with (Sp/C+) or without (Sp/C–) autologous chondrocytes were implanted. Animals were sacrificed sequentially at D20, D40 and D60 after surgery and dissected patellae underwent MRI exploration (8.5 T). T2 values were calculated from eight SE images by using nonlinear least-squares curve fitting on a pixel-by-pixel basis (constant repetition time of 1.5 s, eight different echo times: 5.5, 7.5, 10.5, 12.5, 15.0, 20.0, 25.0 and 30.0 ms). On the T2 map, acquired in a transversal plane through the repair zone, global T2 values and zonal variation of T2 values of repair tissue were evaluated versus control group and compared with macroscopic score and histological studies (toluidine blue, sirius red and hematoxylin-eosin). Partial, total and hypertrophic repair patterns were identified. At D40 and D60, Sp/C+ group was characterized by a higher proportion of total repair in comparison to Sp/C– group. At D60, the proportion of hypertrophic repair was two fold in Sp/C– group versus Sp/C+ group. As confirmed morphologically and histologically, the T2 map also permitted the distinction of three types of repair tissue: total, partial and hypertrophic. Total repair tissue was characterized by high T2 values versus normal cartilage (p<0.05). Zonal variation, reflecting the collagen network organization, appeared only at D60 for Sp/C+ group (p<0.05). Hypertrophic tissue, mainly observed at D60, presented high T2 global values without zonal variation with cartilage depth. These results confirm the potency of the MR T2 map (8.5 T) to characterize macroscopically and microscopically the patterns of the scaffold guided-tissue repair of a focal chondral lesion in the rat patella (total, partial and hypertrophic). On T2 map, three parameters (i.e. MRI macroscopic pattern, T2 global values and zonal variation of T2 values) permit to characterize chondral repair tissue, as a virtual biopsy.  相似文献   
993.
A combined strategy to obtain a partial NMR assignment of the neuronal Tau protein is presented. Confronted with the extreme spectral degeneracy that the spectrum of this 441 amino acid long unstructured protein presents, we have introduced a graphical procedure based on residue type-specific product planes. Combining this strategy with the search for pairwise motifs, and combining the spectra of different Tau isoforms and even of peptides derived from the native sequence, we arrive at a partial assignment that is sufficient to map the interactions of Tau with its molecular partners. The obtained assignments equally confirm the absence of regular secondary structure in the isolated protein.  相似文献   
994.
Layered textures for image-based rendering   总被引:1,自引:0,他引:1       下载免费PDF全文
An extension to texture mapping is given in this paper for improving the efficiency of image-based rendering. For a depth image with an orthogonal displacement at each pixel, it is decomposed by the displacement into a series of layered textures (LTs) with each one having the same displacement for all its texels. Meanwhile, some texels of the layered textures are interpolated for obtaining a continuous 3D approximation of the model represented in the depth image. Thus, the plane-to-plane texture mapping can be used to map these layered textures to produce novel views and the advantages can be obtained as follows: accelerating the rendering speed, supporting the 3D surface details and view motion parallax, and avoiding the expensive task of hole-filling in the rendering stage. Experimental results show the new method can produce high-quality images and run faster than many famous image-based rendering techniques.  相似文献   
995.
S K Bhan  K Krishnanunni 《Sadhana》1983,6(4):297-311
Remote sensing is a new emerging field of technological development and has made a very significant impact on the geological surveys and studies. The work done so far in geological remote sensing has indicated the scope, utility and limitations of these modern techniques in different geological problems. The utility of airborne surveys and aerial photography has now been well established whereas satellite remote sensing at present has two main constraints—resolution and lack of stereoscopy. With the developments in sensor technology to provide sensors with improved resolution, more spectral bands and stereoscopy, substantial new results are anticipated in the geological remote sensing from space. Brief overview of applications of remote sensing techniques to geology is discussed in this paper.  相似文献   
996.
赵吉祥  毛军发 《电子学报》2003,31(12):1891-1893
本文推导出了薄衬底共面波导特性参数计算的近似解析表达式,避免了薄衬底保角变换中的"拥挤现象".利用该表达式并结合部分电容法可以计算在导体与衬底之间加薄绝缘层的共面波导的特性参数,分析结果与实验数据相符合.最后还对有薄绝缘层的硅衬底共面波导的损耗因子进行了分析.  相似文献   
997.
逻辑综合中,工艺映射是关键的一步。过去,基于树的映射由于其速度快、算法简洁而被广泛使用。但是,将电路结构划分为树,破坏了电路结构,缩小了映射的解空间。双态覆盖(Binate Covering)能充分利用门级网表的结构特性,使工艺映射后的电路具有更好的性能。  相似文献   
998.
A combination of immuno-electron microscopy and electron energy-loss spectrum-imaging was used to map the distributions of endocrine polypeptide hormones and proteins in mouse pancreatic islet of Langerhans. Tissue was analyzed from control animals and from mice that were heterozygous for the Anx7 gene, which defines a Ca2+/GTP-dependent membrane fusion and ion channel protein. The heterozygous Anx7 (+/-) mouse displays defects in IP3 receptor mediated Ca2+ signaling and insulin secretion. Therefore, information was obtained about the distributions of the hormones insulin and glucagon, as well as the proteins ANX7 and the IP3 receptor. Insulin secretion appears to be defective in the mutants. It was found from immunolabeling experiments that expression of the IP3 receptor is reduced in mutant islets compared to control islets. Subcellular distributions of sulfur and nitrogen obtained by electron energy-loss spectrum-imaging showed that the insulin concentrations of beta granules were essentially the same in control and mutant islets. By contrast, immunogold labeling of mutant islets shows more insulin immunoreactivity in the beta granules. It follows that insulin may be packaged differently in mutant islets, making antigenic determinants more available to the labeling antibody. The increased rate of insulin secretion in the hyperplastic mutant islets can be explained by compensatory increases in islet size, rather than by an increased insulin concentration in the beta cells. The results indicate that reduced ANX7 expression leads to defects in the IP3 receptor expression in the endocrine cells of the mutant mouse. Increased size of the islet or of adrenal medulla may be a compensatory mechanism for secretion defect by individual endocrine cells. Defects in IP3 receptor expression, and documented consequences of a Ca2+ signaling defect, lead to other changes in organelles such as the mitochondrial number in islet beta-cells. The effects and consequences of reduced ANX7 expression on mitochondria are evident in ultrastructural observations.  相似文献   
999.
不同对虾种间共用微卫星DNA引物的研究   总被引:14,自引:0,他引:14  
采用已发表的斑节对虾的30对微卫星引物,对部分微卫星引物在中国对虾、凡纳对虾、日本对虾中的通用性进行了研究。通过所建立的降温PCR(Touchdown PCR)方法对3种对虾的DNA进行PCR扩增,筛选出3对引物在3种对虾中均能产生清晰谱带。根据上述结果适当调整PCR反应体系中各试剂的量及反应条件,达到了理想的结果。利用这3对引物对3种对虾进行遗传标记分析,结果显示,PCR扩增产物条带清晰,特异性强,每对引物在3种对虾间扩增出的特异性片段大小几乎一致。研究表明,3种对虾基因组间存在一定程度的相似性,引物W15-16、W21-22和W45-46可直接应用于中国对虾、凡纳对虾、日本对虾、斑节对虾分子标记的基因组比较作图,也为图谱克隆法提供了新的思路。  相似文献   
1000.
张立  王培太 《电测与仪表》2002,39(11):13-16
随着我国城网改造的逐步升温,配电管理系统(DMS)成为提高配电网运行和管理水平必不可少的手段,而AM/FM/GIS系统是配电系统整体管理水平提高的集中表现之一。本文围绕电力AM/FM/GIS系统的设计、功能规划,接口方案、一体化设计思想等问题进行了深入的探讨。  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