全文获取类型
收费全文 | 27186篇 |
免费 | 1831篇 |
国内免费 | 133篇 |
专业分类
电工技术 | 418篇 |
技术理论 | 1篇 |
综合类 | 116篇 |
化学工业 | 6386篇 |
金属工艺 | 1093篇 |
机械仪表 | 1676篇 |
建筑科学 | 561篇 |
矿业工程 | 60篇 |
能源动力 | 1146篇 |
轻工业 | 2263篇 |
水利工程 | 127篇 |
石油天然气 | 134篇 |
武器工业 | 10篇 |
无线电 | 4438篇 |
一般工业技术 | 5658篇 |
冶金工业 | 1745篇 |
原子能技术 | 354篇 |
自动化技术 | 2964篇 |
出版年
2024年 | 22篇 |
2023年 | 337篇 |
2022年 | 486篇 |
2021年 | 881篇 |
2020年 | 640篇 |
2019年 | 651篇 |
2018年 | 879篇 |
2017年 | 838篇 |
2016年 | 975篇 |
2015年 | 799篇 |
2014年 | 1250篇 |
2013年 | 1759篇 |
2012年 | 1851篇 |
2011年 | 2200篇 |
2010年 | 1677篇 |
2009年 | 1675篇 |
2008年 | 1547篇 |
2007年 | 1149篇 |
2006年 | 1015篇 |
2005年 | 916篇 |
2004年 | 833篇 |
2003年 | 751篇 |
2002年 | 722篇 |
2001年 | 634篇 |
2000年 | 543篇 |
1999年 | 555篇 |
1998年 | 797篇 |
1997年 | 497篇 |
1996年 | 482篇 |
1995年 | 314篇 |
1994年 | 224篇 |
1993年 | 178篇 |
1992年 | 139篇 |
1991年 | 132篇 |
1990年 | 93篇 |
1989年 | 113篇 |
1988年 | 85篇 |
1987年 | 71篇 |
1986年 | 58篇 |
1985年 | 51篇 |
1984年 | 44篇 |
1983年 | 35篇 |
1982年 | 35篇 |
1981年 | 31篇 |
1980年 | 31篇 |
1979年 | 18篇 |
1977年 | 24篇 |
1976年 | 34篇 |
1975年 | 17篇 |
1974年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
RM Bionta G Blewitt CB Bratton D Casper A Ciocio R Claus M Crouch ST Dye S Errede GW Foster W Gajewski KS Ganezer M Goldhaber TJ Haines TW Jones D Kielczewska WR Kropp JG Learned JM LoSecco J Matthews HS Park LR Price F Reines J Schulz S Seidel E Shumard D Sinclair HW Sobel JL Stone L Sulak R Svoboda G Thornton van der Velde JC C Wuest 《Canadian Metallurgical Quarterly》1987,36(1):30-36
112.
Jong Whan Lee Dong Hee Kwon Jeong Suk Kim Duck Whan Kim Myung Chang Kang Bok Kyu Lim 《Journal of Mechanical Science and Technology》2007,21(2):244-250
This paper presents an investigation on the characteristics of damaged layer in micro-machining by using the ultrahigh-speed
air spindle. The damaged layer in metal cutting is derived from plastic deformation and transformation of metal structure.
In this study, micro-cutting force, surface roughness, and plastic deformation layer according to the variation of machining
conditions were investigated by experiments. The damaged layer was measured using optical microscope for the samples prepared
by metallographic techniques. Its scale was dependent on cutting process parameters, especially feed per tooth. According
to experimental results, it was verified that the thickness of damaged layer was increased with increasing of feed per tooth
and cutting depth, also thickness of damaged layer was reduced in down-milling compared to upmilling during micro-endmilling
operation. 相似文献
113.
Characterisation of a BioFET for detection of albumin in a mixture of human urine is presented. To avoid electrolyte effect of the urine, it was measured in PBS (phosphate buffer saline) at a fixed pH after albumin binding. The drain current was modulated by the albumin bound to the anti-albumin immobilised on the gate surface of the BioFET. The current variation ratio was likely to be proportional to the concentration of the albumin in the range 50-250 mg/1. The results show the feasibility of the BioFET as a urinary albumin sensor. 相似文献
114.
115.
Sang C. Park 《The Visual computer》2003,19(1):38-49
A sweeping operation called polygonal extrusion is defined to improve the modeling power of CSG-based modeling. It is assumed that a 2D cross-sectional polygon (sweeping
polygon) moves in space while its containing plane is kept orthogonal to the tangent direction of the trajectory curve, a planar
polygonal chain having no self-intersections. The objective of the paper is to compute the boundary of the swept volume of
the sweeping polygon as a set of polygons (or triangles). The most significant challenge to accomplishing this objective is
the problem of trimming the swept volume. To solve the trimming problem, 2D-curve offsetting methods are employed. Two algorithms
are presented for polygonal extrusion that are based on different offsetting methods, the Voronoi diagram and PWID offset.
The proposed algorithms have been implemented and tested with various examples.
Published online: 28 January 2003 相似文献
116.
Jong Min Kim Donghee Lee Sang Lyul Min Chong Sang Kim 《Information Processing Letters》2003,85(2):93-97
A new dynamic buffer allocation strategy based on the notion of marginal gains is presented for the buffer cache that is used by the operating system to store frequently accessed disk blocks in main memory, and the performance of the proposed strategy is compared with those of previous allocation strategies. In the proposed strategy, marginal gain values are predicted by exploiting functions that approximate the expected number of buffer hits per unit time. Experimental results from both trace-driven simulation and an actual implementation in the FreeBSD operating system show that the proposed strategy accurately predicts the marginal gain values for various workloads resulting in significantly improved buffer hit ratios. 相似文献
117.
Joon C. Park Author Vitae Author Vitae 《Computer aided design》2003,35(9):807-812
Presented in this paper is a topology reconstruction algorithm from a set of unorganized trimmed surfaces. Error-prone small geometric elements are handled to give proper topological information. It gives complete topology to topologically complete models, and it is also tolerant to incomplete models. The proposed algorithm is vertex-based in that clues for topological information are searched from the set of vertices first, not from that of edges. 相似文献
118.
Effects of austenitizing treatment temperatures on aqueous corrosion properties of martensitic stainless steels were investigated by electrochemical tests (potentiodynamic test, potentiostatic test and electrochemical impedance spectroscopy), and surface analyses (optical microscopy and XRD). The results of potentiodynamic test revealed that the breakdown potential increased with the increased austenitizing temperature, indicating increased relative resistance to initiation of localized corrosion. EIS measurements showed that MSS3 (1030 °C) exhibits larger polarization resistance value than MSS1 (970 °C) and MSS2 (1000 °C) at passive and breakdown states. This was caused by decreasing the amount of Cr-rich M23C6 carbide which acts as preferential sites for pitting corrosion. 相似文献
119.
Yoon Carolyn; Feinberg Fred; Hu Ping; Gutchess Angela Hall; Hedden Trey; Chen Hiu-Ying Mary; Jing Qicheng; Cui Yao; Park Denise C. 《Canadian Metallurgical Quarterly》2004,19(3):379
Understanding how aging influences cognition across different cultures has been hindered by a lack of standardized, cross-referenced verbal stimuli. This study introduces a database of such item-level stimuli for both younger and older adults, in China and the United States, and makes 3 distinct contributions. First, the authors specify which item categories generalize across age and/or cultural groups, rigorously quantifying differences among them. Second, they introduce novel, powerful methods to measure between-group differences in freely generated ranked data, the rank-ordered logit model and Hellinger Affinity. Finally, a broad archive of tested, cross-linguistic stimuli is now freely available to researchers: data, similarity measures, and all stimulus materials for 105 categories and 4 culture-by-age groups, comprising over 10,000 fully translated unique item responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
120.
In this paper, we propose an efficient design method for area optimization in a digital filter. The conventional methods to reduce the number of adders in a filter have the problem of a long critical path delay caused by the deep logic depth of the filter due to adder sharing. Furthermore, there is such a disadvantage that they use the transposed direct form (TDF) filter which needs more registers than those of the direct form (DF) filter. In this paper, we present a hybrid structure of a TDF and DF based on the flattened coefficients method so that it can reduce the number of flip‐flops and full‐adders without additional critical path delay. We also propose a resource sharing method and sharing‐pattern searching algorithm to reduce the number of adders without deepening the logic depth. Simulation results show that the proposed structure can save the number of adders and registers by 22 and 26%, respectively, compared to the best one used in the past. 相似文献