全文获取类型
收费全文 | 20080篇 |
免费 | 1426篇 |
国内免费 | 817篇 |
专业分类
电工技术 | 1074篇 |
技术理论 | 4篇 |
综合类 | 1034篇 |
化学工业 | 3645篇 |
金属工艺 | 904篇 |
机械仪表 | 1198篇 |
建筑科学 | 1357篇 |
矿业工程 | 532篇 |
能源动力 | 553篇 |
轻工业 | 1124篇 |
水利工程 | 297篇 |
石油天然气 | 1137篇 |
武器工业 | 129篇 |
无线电 | 2627篇 |
一般工业技术 | 2647篇 |
冶金工业 | 1046篇 |
原子能技术 | 169篇 |
自动化技术 | 2846篇 |
出版年
2024年 | 70篇 |
2023年 | 319篇 |
2022年 | 549篇 |
2021年 | 789篇 |
2020年 | 560篇 |
2019年 | 519篇 |
2018年 | 577篇 |
2017年 | 599篇 |
2016年 | 557篇 |
2015年 | 693篇 |
2014年 | 902篇 |
2013年 | 1220篇 |
2012年 | 1153篇 |
2011年 | 1281篇 |
2010年 | 1005篇 |
2009年 | 1038篇 |
2008年 | 1028篇 |
2007年 | 979篇 |
2006年 | 1031篇 |
2005年 | 925篇 |
2004年 | 624篇 |
2003年 | 610篇 |
2002年 | 528篇 |
2001年 | 449篇 |
2000年 | 530篇 |
1999年 | 588篇 |
1998年 | 533篇 |
1997年 | 466篇 |
1996年 | 444篇 |
1995年 | 318篇 |
1994年 | 303篇 |
1993年 | 213篇 |
1992年 | 172篇 |
1991年 | 141篇 |
1990年 | 125篇 |
1989年 | 95篇 |
1988年 | 77篇 |
1987年 | 52篇 |
1986年 | 44篇 |
1985年 | 37篇 |
1984年 | 21篇 |
1983年 | 18篇 |
1982年 | 30篇 |
1981年 | 23篇 |
1980年 | 15篇 |
1979年 | 10篇 |
1978年 | 11篇 |
1977年 | 11篇 |
1976年 | 12篇 |
1971年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Jen Hong Tan U. Rajendra Acharya Choo Min Lim K. Thomas Abraham 《Digital Signal Processing》2013,23(3):1022-1031
Feasible clinical application of any automated segmenting methodology demands more than just accuracy. Amendment to the automated delineation is necessary when the algorithm fails, however, integrated solution to such a scenario is largely absent in literature. Hence in this survey we devised an architecture that does both the automated and interactive lung field localizations using a single segmenting engine—random walker algorithm—so that intuitive amendment is only necessary when the automated generated delineation is unsatisfactory. The algorithm proceeds by first extracting 18 intensity profiles running horizontally, each of them equally spacing apart, and in each intensity profile three extreme points denoting the two lungs and the esophagus are determined through profile matching. This done, the algorithm removes profiles that do not intersect with the lung, and the rest of the extreme points are plugged into random walker algorithm to perform segmentation. The achieved accuracy in localization by the above was 0.8875 in terms of overlap measure (the maximum value for this parameter is 1) over 341 images. In the case where unsatisfactory delineation prompts amendment necessary, the user can interactively segment the lung by just a shift on some of the previous-determined points to the desired locations, and random walker algorithm is run again with the amended input. By such a fusion, the benefits of both the automated and interactive segmentation are shared in a single architecture. 相似文献
32.
33.
Learning Image-Text Associations 总被引:2,自引:0,他引:2
Tao Jiang Ah-Hwee Tan 《Knowledge and Data Engineering, IEEE Transactions on》2009,21(2):161-177
Web information fusion can be defined as the problem of collating and tracking information related to specific topics on the World Wide Web. Whereas most existing work on Web information fusion has focused on text-based multidocument summarization, this paper concerns the topic of image and text association, a cornerstone of cross-media Web information fusion. Specifically, we present two learning methods for discovering the underlying associations between images and texts based on small training data sets. The first method based on vague transformation measures the information similarity between the visual features and the textual features through a set of predefined domain-specific information categories. Another method uses a neural network to learn direct mapping between the visual and textual features by automatically and incrementally summarizing the associated features into a set of information templates. Despite their distinct approaches, our experimental results on a terrorist domain document set show that both methods are capable of learning associations between images and texts from a small training data set. 相似文献
34.
主要研究XML中间件的分布式异构数据库的数据分片策略,以便能够并行处理XML查询。为了描述XML数据分片,提出了对象树、子树的概念,将一棵XML数据树分割成对象树和子树,对象树在各个站点上复制,子树标签化后均匀分片到各个站点上。为了实现用户数据分片查询工作量的均衡,对最大树深的子树采用减治法策略,减治法策略后的子树又分配到一个新的站点上。基于这一思想,提出并实现其算法。实验结果证明:在分布式异构数据库的检索、查询和访问中,基于对象树、子树的数据分片算法的性能要比PSPIB算法性能优越。 相似文献
35.
基于光纤环网的隧道火灾监控系统研究 总被引:1,自引:1,他引:0
文章对基于光纤环网的隧道群火灾报警系统进行研究,分析了其优缺点,提出了解决办法,并完成改造,应用于实际. 相似文献
36.
Layered image coding using the DCT pyramid 总被引:2,自引:0,他引:2
A block-based subband image coder that exploits the ability to perform decimation in the discrete cosine transform (DCT) domain to effect a pyramidal data structure is described. The proposed "DCT pyramid" has a distinct feature of improved image rendition properties without the associated blocking artifacts at low bit-rates. 相似文献
37.
38.
39.
A series of bis(hydroxymethyl)-substituted imidazoles, thioimidazoles, and pyrrolizines and related bis(carbamates), linked to either 9-anilinoacridine (intercalating) or 4-(4-quinolinylamino)benzamide (minor groove binding) carriers, were synthesized and evaluated for sequence-specific DNA alkylation and cytotoxicity. The imidazole and thioimidazole analogues were prepared by initial synthesis of [(4-aminophenyl)alkyl]imidazole-, thioimidazole-, or pyrrolizine dicarboxylates, coupling of these with the desired carrier, and reduction to give the required bis(hydroxymethyl) alkylating moiety. The pyrrolizines were the most reactive alkylators, followed by the thioimidazoles, while the imidazoles were unreactive. The pyrrolizines and some of the thioimidazoles cross-linked DNA, as measured by agarose gel electrophoresis. Strand cleavage assays showed that none of the compounds reacted at purine N7 or N3 sites in the gpt region of the plasmid gpt2Eco, but the polymerase stop assay showed patterns of G-alkylation in C-rich regions. The corresponding thioimidazole bis(carbamates) were more selective than the bis(hydroxymethyl) pyrrolizines, with high-intensity bands at 5'-NCCN, 5'-NGCN and 5'-NCGN sequences in the PCR stopping assay ( indicates block sites). The data suggest that these targeted compounds, like the known thioimidazole bis(carbamate) carmethizole, alkylate exclusively at guanine residues via the 2-amino group, with little or no alkylation at N3 and N7 guanine or adenine sites. The cytotoxicities of the compounds correlated broadly with their reactivities, with the bis(hydroxymethyl)imidazoles being the least cytotoxic (IC50s >1 microM; P388 leukemia) and with the intercalator-linked analogues being more cytotoxic than the corresponding minor-groove-targeted ones. This was true also for the more reactive thioimidazole bis(carbamates) (IC50s 0.8 and 11 microM, respectively), but both were more active than the analogous "untargeted" carmethizole (IC50 20 microM). The bis(hydroxymethyl)pyrrolizine analogues were the most cytotoxic, with IC50s as low as 0.03 microM. 相似文献
40.
提出了一种使用4个相机测量变形钢板三维形状的方法;在没有纹理的钢板上画一些点,使用4个相机同时拍摄钢板;利用边缘检测算法找出钢板的边缘,利用特征点提取算法提取出4个图像中钢板上的特征点,并找到4个图像上精确的特征点匹配关系,然后测量出这些特征点的三维点;最后,以这些三维点为种子点向外区域增长,从而得到钢板的三维形状;实验对变形钢板进行三维测量,得到了钢板的精确的三维形状,结果验证了该方法的有效性和可行性。 相似文献