全文获取类型
收费全文 | 97378篇 |
免费 | 10956篇 |
国内免费 | 7254篇 |
专业分类
电工技术 | 7681篇 |
技术理论 | 1篇 |
综合类 | 9217篇 |
化学工业 | 13306篇 |
金属工艺 | 6525篇 |
机械仪表 | 6820篇 |
建筑科学 | 6915篇 |
矿业工程 | 3534篇 |
能源动力 | 2610篇 |
轻工业 | 10855篇 |
水利工程 | 2738篇 |
石油天然气 | 3728篇 |
武器工业 | 1291篇 |
无线电 | 10636篇 |
一般工业技术 | 9567篇 |
冶金工业 | 3832篇 |
原子能技术 | 1374篇 |
自动化技术 | 14958篇 |
出版年
2024年 | 611篇 |
2023年 | 1618篇 |
2022年 | 3635篇 |
2021年 | 4560篇 |
2020年 | 3431篇 |
2019年 | 2649篇 |
2018年 | 2916篇 |
2017年 | 3205篇 |
2016年 | 2970篇 |
2015年 | 4445篇 |
2014年 | 5512篇 |
2013年 | 6512篇 |
2012年 | 7819篇 |
2011年 | 8463篇 |
2010年 | 7751篇 |
2009年 | 7481篇 |
2008年 | 7433篇 |
2007年 | 7118篇 |
2006年 | 6164篇 |
2005年 | 5094篇 |
2004年 | 3692篇 |
2003年 | 2667篇 |
2002年 | 2500篇 |
2001年 | 2177篇 |
2000年 | 1668篇 |
1999年 | 962篇 |
1998年 | 458篇 |
1997年 | 378篇 |
1996年 | 317篇 |
1995年 | 249篇 |
1994年 | 209篇 |
1993年 | 186篇 |
1992年 | 134篇 |
1991年 | 110篇 |
1990年 | 81篇 |
1989年 | 77篇 |
1988年 | 52篇 |
1987年 | 42篇 |
1986年 | 39篇 |
1985年 | 18篇 |
1984年 | 17篇 |
1983年 | 15篇 |
1982年 | 19篇 |
1981年 | 10篇 |
1980年 | 20篇 |
1979年 | 24篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1976年 | 13篇 |
1959年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
对调质状态800MPa低合金高强度钢及其焊接接头进行了系列温度的断裂韧性测试,讨论不同焊接方法对焊接接头断裂韧性的影响。发现板材的轧制方向对断裂韧性影响显著,LT方向试件的断裂韧性远超过TL方向试件的断裂韧性。在-60℃以上,母材处于上平台延性断裂范畴。在-80℃,裂纹扩展过程中有延脆断裂模式的转变。焊条电弧焊焊缝的断裂韧性与气体保护焊焊缝的断裂韧性相当。尽管常温下焊缝金属的断裂韧性甚至优于母材,但随着试验温度的降低,焊缝金属的断裂韧性迅速下降。在-20℃已发生断裂模式转变,这在结构服役时要引起重视。本研究为大型工程机械的断裂安全评定奠定了基础。 相似文献
82.
The 5Cu40Zn55Al and 15Cu20Zn65Al alloys were prepared in the AI-Zn-Cu system, There exist the metastable phases ε and θ in the two alloys after homogenization treatment and furnace cooling, respectively. It is shown that the particles are refined from 3 mm to less than 10 μm after hammering the two alloys but there are still metastable phases. This means that the phase constituents of the two alloys have no changes by the deformation, which is different from that by balling. The phase constituents are not changed at room temperature by hammering, which is dependent on the deformation mechanism of hammering. 相似文献
83.
串联法氧化铝生产中的合流脱硅 总被引:1,自引:1,他引:1
合流脱硅是简化联合法生产流程、降低能耗的有效措施。因此。国内外业界做了大量卓有成效的工作。串联法的工艺特点,更宜于采用合流脱硅。试验结果表明,串联法采用常压合流脱硅流程可以达到所需要的硅量指数。文中还对合流脱硅的硅量指数、合流点、合流脱硅温度、赤泥种子和添加石灰乳等问题进行了讨论。 相似文献
84.
The Cd−Zn system has been thermodynamically reassessed with the CALPHAD method by combining more recent experimental data,
in particular the activities of zinc in the liquid phase. A good agreement is obtained between the calculated and experimental
thermodynamic parameters as well asphase boundaries. 相似文献
85.
This paper presents a class of dual–primal proximal point algorithms (PPAs) for extended convex programming with linear constraints. By choosing appropriate proximal regularization matrices, the application of the general PPA to the equivalent variational inequality of the extended convex programming with linear constraints can result in easy proximal subproblems. In theory, the sequence generated by the general PPA may fail to converge since the proximal regularization matrix is asymmetric sometimes. So we construct descent directions derived from the solution obtained by the general PPA. Different step lengths and descent directions are chosen with the negligible additional computational load. The global convergence of the new algorithms is proved easily based on the fact that the sequences generated are Fejér monotone. Furthermore, we provide a simple proof for the O(1/t) convergence rate of these algorithms. 相似文献
86.
核反应堆中需要实时精确地计算堆芯和增殖材料的有效共振积分或群截面来实现反应堆的安全控制。整个计算过程因为涉及大量的积分运算和庞大的核素截面数据,采用常规的计算方法,计算时耗相当大。基于统一计算设备架构(CUDA)平台,利用图形处理器(GPU)的计算能力,对整个计算过程进行并行化分解,多线程同时运算,大幅度提升计算速度,降低时耗。实验结果表明,在GPU上并行计算所得结果与原始数据没有明显差异,且加速效果显著。 相似文献
87.
Peng Geng Min Huang Shuaiqi Liu Jun Feng Peina Bao 《Multimedia Tools and Applications》2016,75(17):10583-10593
The curvelet transform can represent images at both different scales and different directions. Ripplet transform, as a higher dimensional generalization of the curvelet transform, provides a new tight frame with sparse representation for images with discontinuities along C2 curves. However, the ripplet transform is lack of translation invariance, which causes the pseudo-Gibbs phenomenon on the edges of image. In this paper, the cycle spinning method is adopted to suppress the pseudo-Gibbs phenomena in the multifocus image fusion. On the other hand, a modified sum-modified-laplacian rule based on the threshold is proposed to make the decision map to select the ripplet coefficient. Several experiments are executed to compare the presented approach with other methods based on the curvelet, sharp frequency localized contourlet transform and shearlet transform. The experiments demonstrate that the presented fusion algorithm outperforms these image fusion works. 相似文献
88.
89.
90.
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