全文获取类型
收费全文 | 92807篇 |
免费 | 9081篇 |
国内免费 | 5130篇 |
专业分类
电工技术 | 5598篇 |
技术理论 | 3篇 |
综合类 | 6406篇 |
化学工业 | 15249篇 |
金属工艺 | 5400篇 |
机械仪表 | 6060篇 |
建筑科学 | 6466篇 |
矿业工程 | 2598篇 |
能源动力 | 2410篇 |
轻工业 | 8271篇 |
水利工程 | 1770篇 |
石油天然气 | 4454篇 |
武器工业 | 801篇 |
无线电 | 11005篇 |
一般工业技术 | 11394篇 |
冶金工业 | 4425篇 |
原子能技术 | 1068篇 |
自动化技术 | 13640篇 |
出版年
2024年 | 514篇 |
2023年 | 1655篇 |
2022年 | 3059篇 |
2021年 | 4173篇 |
2020年 | 3089篇 |
2019年 | 2755篇 |
2018年 | 3032篇 |
2017年 | 3165篇 |
2016年 | 3004篇 |
2015年 | 4030篇 |
2014年 | 4927篇 |
2013年 | 5941篇 |
2012年 | 6487篇 |
2011年 | 7301篇 |
2010年 | 6247篇 |
2009年 | 6125篇 |
2008年 | 5992篇 |
2007年 | 5511篇 |
2006年 | 5334篇 |
2005年 | 4341篇 |
2004年 | 3130篇 |
2003年 | 2580篇 |
2002年 | 2425篇 |
2001年 | 2081篇 |
2000年 | 1777篇 |
1999年 | 1622篇 |
1998年 | 1217篇 |
1997年 | 1031篇 |
1996年 | 893篇 |
1995年 | 730篇 |
1994年 | 579篇 |
1993年 | 418篇 |
1992年 | 336篇 |
1991年 | 299篇 |
1990年 | 229篇 |
1989年 | 206篇 |
1988年 | 140篇 |
1987年 | 122篇 |
1986年 | 82篇 |
1985年 | 63篇 |
1984年 | 48篇 |
1983年 | 48篇 |
1982年 | 44篇 |
1981年 | 25篇 |
1980年 | 33篇 |
1979年 | 28篇 |
1978年 | 24篇 |
1977年 | 18篇 |
1976年 | 31篇 |
1975年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
94.
Bing Q. Han Farghalli A. Mohamed Enrique J. Lavernia 《Metallurgical and Materials Transactions A》2003,34(1):71-83
In the present study, the mechanical properties of Fe processed via severe plastic deformation (equal-channel angular pressing (ECAP)) at room temperature were investigated for the first time.
The grain size of annealed Fe, with an initial grain size of about 200 μm, was reduced drastically during ECAP. After eight passes, the grain size reaches 200 to 400 nm, as documented by means of
transmission electron microscopy (TEM). The value of microhardness during pressing increases 3 times over that of the starting
material after the first pass and increases slightly during subsequent pressing for higher-purity Fe. Examination of the value
of microhardness after eight passes as a function of post-ECAP annealing temperature shows a transition from recovery to recrystallization,
an observation that resembles the behavior reported for heavily deformed metals and alloys. The tensile and compression behaviors
were examined. In tension, a drop in the engineering stress-engineering strain curve beyond maximum load was observed both
in the annealed Fe and the ECAP Fe. This drop is related to the neck deformation. The fracture surface, examined by scanning
electron microscopy (SEM), shows vein patterns, which is different from the dimples found on the fracture surface of annealed
Fe. In compression, an initial strain-hardening region followed by a no-strain-hardening region was observed in the ECAP Fe.
The yield strength in tension of the ECAP Fe was observed to be higher than that in compression. The strengthening mechanisms
and softening behavior are discussed. 相似文献
95.
H. Tsukamoto T.D. Boone J. Han J.M. Woodall 《Photonics Technology Letters, IEEE》2005,17(7):1411-1413
We present a novel optical switching technique utilizing emission packet positioning of semiconductor heterostructure. A modulation-doped p-AlGaAs-GaAs heterostructure is employed to control spontaneous emission packet positioning with electric fields. Emission packets generated by optical input signals are brought over 150 /spl mu/m with electric fields, so the output fibers can detect the emission intensity as signals. The first-order analysis indicates that the drift velocity of minority electrons in GaAs limits the detectable maximum data rate and nanoseconds timescale signal routing operation at 20 Gb/s is possible at an electron drift velocity of 2/spl times/10/sup 7/ cm/s. 相似文献
96.
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
97.
采用SE 3 0为固定液进行色谱柱分离 ,用外标定量法测定泥土中的微量六氯环戊二烯 ,结果最小检知量为 0 .18× 10 - 6 ,相关系数为 0 .99992。 相似文献
98.
V. S. Bessmertnyi N. I. Min’ko P. S. Dyumina V. P. Krokhin S. V. Semenenko M. A. Lipko 《Glass and Ceramics》2005,62(11-12):386-387
A technology for the synthesis of synthetic minerals (using the example of spinels) using a low-temperature plasma flame is developed. The diagnostic properties of spinels are identified. 相似文献
99.
浅析包装中色彩运用的文化原则 总被引:1,自引:0,他引:1
从某种程度上讲,包装是对产品的一种定位和阐释。心理学有关研究表明,人的视觉器官,在观察物体时,最初的20秒内色彩感觉占80%,而形体感觉占20%:两分钟后色彩占60%,形体占40%;5分钟后各占一半,并且这种状态将继续保持。可见,包装给人的印象多么迅速、深刻、持久。国外学者曾有过一项研究,发现由广告媒体招徕的顾客中,有33%的人在销售现场会选择包装吸引人的品牌,包装重要性不言而喻。可以说,包装的素材、形式和色彩等因素综合在一起,将产品引伸至一个深层的文化氛围。 相似文献
100.