全文获取类型
收费全文 | 56481篇 |
免费 | 5046篇 |
国内免费 | 2645篇 |
专业分类
电工技术 | 3396篇 |
技术理论 | 5篇 |
综合类 | 4162篇 |
化学工业 | 9324篇 |
金属工艺 | 3458篇 |
机械仪表 | 3713篇 |
建筑科学 | 4516篇 |
矿业工程 | 1641篇 |
能源动力 | 1593篇 |
轻工业 | 4072篇 |
水利工程 | 1096篇 |
石油天然气 | 3328篇 |
武器工业 | 484篇 |
无线电 | 6200篇 |
一般工业技术 | 6521篇 |
冶金工业 | 2515篇 |
原子能技术 | 562篇 |
自动化技术 | 7586篇 |
出版年
2024年 | 278篇 |
2023年 | 959篇 |
2022年 | 1649篇 |
2021年 | 2324篇 |
2020年 | 1818篇 |
2019年 | 1509篇 |
2018年 | 1643篇 |
2017年 | 1773篇 |
2016年 | 1548篇 |
2015年 | 2289篇 |
2014年 | 2643篇 |
2013年 | 3125篇 |
2012年 | 3441篇 |
2011年 | 3736篇 |
2010年 | 3318篇 |
2009年 | 3245篇 |
2008年 | 3207篇 |
2007年 | 3050篇 |
2006年 | 3228篇 |
2005年 | 2703篇 |
2004年 | 1920篇 |
2003年 | 1969篇 |
2002年 | 2281篇 |
2001年 | 1957篇 |
2000年 | 1421篇 |
1999年 | 1497篇 |
1998年 | 1069篇 |
1997年 | 878篇 |
1996年 | 818篇 |
1995年 | 714篇 |
1994年 | 537篇 |
1993年 | 413篇 |
1992年 | 322篇 |
1991年 | 201篇 |
1990年 | 177篇 |
1989年 | 140篇 |
1988年 | 104篇 |
1987年 | 78篇 |
1986年 | 37篇 |
1985年 | 40篇 |
1984年 | 23篇 |
1983年 | 21篇 |
1982年 | 17篇 |
1981年 | 13篇 |
1980年 | 22篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1959年 | 1篇 |
1953年 | 1篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
小剂量辐射对肿瘤细胞K_(562)及肿瘤病人天然杀伤细胞(NK)活性的影响 总被引:2,自引:0,他引:2
已知小剂量辐射可增强机体免疫功能。从对高本底地区的调查发现,该地区居民肿瘤死亡率及某些肿瘤发病率有所降低(1)。NK细胞能直接杀伤肿瘤细胞,在肿瘤免疫中起着重要的作用。本文观察小剂量辐射对肿瘤病人和正常人外周血淋巴细胞NK活性的相对效应以及对人红白血病细胞(K(562)细胞)的影响,以期从体外买验来探索较小剂量辐射对肿瘤治疗的影响 相似文献
2.
本文提出新型布线算法,集李氏迷宫法与线搜索法的长处为一体,以饱和带法进行动态排序,以线搜索法确定借孔位置,然后用李氏法进行单层布线,获得最佳路径,从而达到线型好,布通率高的效果。 相似文献
3.
4.
Xiang‐Dan Li Zhen‐Xin Zhong Sang‐Hoon Han Seung Hee Lee Myong‐Hoon Lee 《Polymer International》2005,54(2):406-411
From chloromethylated polyimide, a useful starting material for modification of aromatic polyimides, a thermocurable transparent polyimide having acrylate side groups was prepared. In the presence of 1,8‐diazabicyclo[5,4,0]undec‐7‐ene, chloromethylated polyimide was esterified with acrylic acid to synthesize poly(imide methylene acrylate). The polymer was soluble in organic solvent, which makes it possible to prepare a planar film by spin coating. The polymer film became insoluble after thermal treatment at 230 °C for 30 min. Optical transparency of the film at 400 nm (for 1 µm thickness) was higher than 98 % and not affected by further heating at 230 °C for 250 min. Adhesion properties measured by the ASTM D3359‐B method ranged from 4B to 5B. Preliminary results of planarization testing showed a high degree of planarization (DOP) value (>0.53). These properties demonstrate that poly(imide methylene acrylate) could be utilized as a thermocurable transparent material in fabricating display devices such as TFT‐LCD. Copyright © 2004 Society of Chemical Industry 相似文献
5.
In this paper, we present efficient VLSI architectures for full-search block-matching motion estimation (BMME) algorithm. Given a search range, we partition it into sub-search arrays called tiles. By fully exploiting data dependency within a tile, efficient VLSI architectures can be obtained. Using the proposed VLSI architectures, all the block-matchings in a tile can be processed in parallel. All the tiles within a search range can be processed serially or concurrently depending on various requirements. With the consideration of processing speed, hardware cost, and I/O bandwidth, the optimal tile size for a specific video application is analyzed. By partitioning a search range into tiles with appropriate size, flexible VLSI designs with different throughput can be obtained. In this way, cost effective VLSI designs for a wide range of video applications, from H.261 to HDTV, can be achieved. 相似文献
6.
7.
This paper deals with the trajectory planning problem for redundant manipulators. A genetic algorithm (GA) using a floating point representation is proposed to search for the optimal end-effector trajectory for a redundant manipulator. An evaluation function is defined based on multiple criteria, including the total displacement of the end-effector, the total angular displacement of all the joints, as well as the uniformity of Cartesian and joint space velocities. These criteria result in minimized, smooth end-effector motions. Simulations are carried out for path planning in free space and in a workspace with obstacles. Results demonstrate the effectiveness and capability of the proposed method in generating optimized collision-free trajectories. 相似文献
8.
G Charpentier S Belloncik G Ducros D Fontenille L Tian JM Quiot 《Canadian Metallurgical Quarterly》1995,32(6):793-800
The objectives of this study were to develop sex-, age-, and body size-specific nomograms and partition values for upper and lower limits of M-mode echocardiographic aortic root measurements derived from a large population-based cohort. The study sample consisted of 1433 male and 1816 female participants in the Framingham Heart Study and Framingham Offspring Study who were normotensive and free of clinically apparent heart disease at the baseline examination. Aortic root measurements were obtained by M-mode echocardiography by a leading-edge to leading-edge technique. The relations of age and measures of body size with aortic root dimensions were evaluated with sex-specific correlations and multiple stepwise linear regression analyses. Age was the most important determinant of aortic root size in both men and women in the multivariable regression models. Models with age and body surface area yielded R2 values of 0.214 in men and 0.222 in women. Models with age and height yielded lower R2 values of 0.136 in men and 0.181 in women. Thus aortic root dimensions vary widely with the age, sex, and body size of individuals. Sex-specific reference nomograms of aortic root dimensions in relation to age and body size (body surface area or height) are presented to facilitate the detection of abnormalities of aortic root size. 相似文献
9.
Summary We consider a circular cylindrical membrane subjected to longitudinal extension and twist. The associated equilibrium deformation is considered to be axisymmetric and the analysis is based on a direct two-dimensional formulation. Wrinkling of the membrane is taken into account in an approximate way by introducing arelaxed strain energy function derived from the neo-Hookean strain energy for isotropic elastic solids. Analytical formulae for wrinkled parts of the membrane are used to corroborate the results of a numerical treatment of the full boundary value problem.Dedicated to the memory of A. C. Pipkin 相似文献
10.
In order to investigate the galvanic anodic protection (GAP) of ferrous metals (such as 410, 304 and 316 stainless steels) in acid solutions by doped polyaniline (PANi), separate doped PANi powder-pressed electrodes with different surface areas (the area ratio of the PANi electrode to stainless steel is between 1:1 and 1:2) have been prepared. These were coupled with ferrous metal in the following solutions: 5 M sulphuric acid, 5 M phosphoric acid and industrial phosphoric acid (containing 5 M phosphoric acid and 0.05% chloride ion) to construct a galvanic cell, in which PANi is cathode while ferrous metal is anode. The results indicate that a PANi electrode with sufficient area can provide corrosion protection to stainless steel in these acidic solutions. A pilot scale coupling experiment was carried out. The results indicate that PANi is a promising material as an electrode for the anodic protection of ferrous metals in acidic solutions in industrial situations. 相似文献