全文获取类型
收费全文 | 39320篇 |
免费 | 4073篇 |
国内免费 | 1909篇 |
专业分类
电工技术 | 2495篇 |
综合类 | 3052篇 |
化学工业 | 6650篇 |
金属工艺 | 2020篇 |
机械仪表 | 2487篇 |
建筑科学 | 2704篇 |
矿业工程 | 1321篇 |
能源动力 | 1075篇 |
轻工业 | 3648篇 |
水利工程 | 890篇 |
石油天然气 | 2133篇 |
武器工业 | 338篇 |
无线电 | 4478篇 |
一般工业技术 | 4452篇 |
冶金工业 | 1643篇 |
原子能技术 | 460篇 |
自动化技术 | 5456篇 |
出版年
2024年 | 230篇 |
2023年 | 838篇 |
2022年 | 1581篇 |
2021年 | 2201篇 |
2020年 | 1693篇 |
2019年 | 1314篇 |
2018年 | 1360篇 |
2017年 | 1585篇 |
2016年 | 1342篇 |
2015年 | 1851篇 |
2014年 | 2285篇 |
2013年 | 2604篇 |
2012年 | 2885篇 |
2011年 | 3028篇 |
2010年 | 2658篇 |
2009年 | 2441篇 |
2008年 | 2332篇 |
2007年 | 2125篇 |
2006年 | 1995篇 |
2005年 | 1662篇 |
2004年 | 1151篇 |
2003年 | 858篇 |
2002年 | 774篇 |
2001年 | 618篇 |
2000年 | 626篇 |
1999年 | 613篇 |
1998年 | 487篇 |
1997年 | 422篇 |
1996年 | 402篇 |
1995年 | 320篇 |
1994年 | 243篇 |
1993年 | 189篇 |
1992年 | 151篇 |
1991年 | 117篇 |
1990年 | 63篇 |
1989年 | 68篇 |
1988年 | 65篇 |
1987年 | 26篇 |
1986年 | 28篇 |
1985年 | 18篇 |
1984年 | 11篇 |
1983年 | 8篇 |
1982年 | 9篇 |
1981年 | 2篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1959年 | 1篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Qiang Xia Tao Feng Xiaowei Lou Ying Wang Yangying Sun Daodong Pan Jinxuan Cao 《International Journal of Food Science & Technology》2020,55(2):669-680
As a decisive attribute, flavour could be influenced by HP treatments through multiple physical and chemical pathways within the high pressure (HP)-assisted meat curing process. This investigation aimed to identify the major pathway influencing volatile flavour patterns of two representative vinasse-cured duck (VCD) products with HP treatments (150–300 MPa/15 min), including wet and dry types, by employing headspace fingerprinting as an untargeted approach. Results suggested that HP treatments greatly lowered moisture contents and increased Warner-Bratzler shear force and thiobarbituric acid reactive substances of the cured samples. According to multivariate models, the volatile flavour patterns of the HP-processed VCD could be clearly separated from the unprocessed samples, but the VCD pressurised at different intensities represented similar volatile fingerprinting, which was validated by e-nose analysis. The discriminant analysis (OPLS-DA) model outlined vinasse-derived ethanol, acetic acid, 3-methyl-1-butanol, 2-methyl-1-butanol, phenethyl alcohol and 2-methyl-3-octanone as the major discriminant aromas across the unpressurised and pressurised samples. 相似文献
22.
23.
Video transmission over IEEE 802.11e wireless networks still shows poor performance for large bandwidth demand and frequently changed environments. Thus, several enhancements of IEEE 802.11e were proposed. On the other hand, big frames and simultaneous sending of adjacent frames always cause packet dropping for buffer overflow. In the past, we proposed an IEEE 802.11e enhancement named DFAA and a content aware mechanism to solve the above problems. The motivation of this paper is to find a proper way to integrate these two mechanisms. A DFAA enhancement (DFAA-E) is proposed to make up the insufficiency of content aware mechanism. Experiments results show that the combination of DFAA-E and content aware mechanism improves the video decoded quality greatly. And its performance can be further enhanced by selecting the suitable settings of certain parameters. 相似文献
24.
Minghuan Wang Xia Chen Wenjun Tong Jiajie Wang Xindi Wang 《The International Journal of Advanced Manufacturing Technology》2020,107(1):157-166
Microdimples as a typical surface texture has been widely used for improving the properties in tribology and heat transfer fields. Ultrasonically assisted 相似文献
25.
The flame front deformation instability of low-velocity filtration combustion within an inert packed bed is studied based on the initial preheating non-uniformity. Based on the experimental phenomena, an initial thermal perturbation model is numerically proposed so as to predict the deformation behaviors of the flame front instabilities. The numerical prediction indicates that the assumption of an initial thermal perturbation is a feasible explanation as the cause of the flame front inclination instability. As the initial thermal perturbation increases, the phenomena of the flame front break and shrinking instabilities could easily occur at high filtration velocity or low equivalence ratio. Moreover, the evolutions of the flame front break rate and the shrinking rate are quantitatively analyzed. 相似文献
26.
27.
In colloidal suspensions of silica, particles undergo constant collisions. By controlling various parameters, the repulsive barrier can be reduced, thereby substantially increasing the number of collision‐induced dimerization events. Xia and co‐workers report on p. 1627 that the dimers could be arrested and then permanently fixed by introducing a small amount of fresh tetraethylorthosilicate into the colloidal suspension, with monodisperse dimer yields of up to 50 %. This yield could be increased to 80 % by centrifugation in a density gradient medium. When fresh tetraethylorthosilicate is introduced into a colloidal suspension of silica spheres, it hydrolyzes and condenses in situ to arrest and fix the dimers resulting from constant collisions between the spheres. By optimizing the experimental parameters (including the length of aging time) and the diameter of the silica spheres, as well as the concentrations of counterions, water, and ammonia, it is possible to routinely produce monodisperse dimers with a yield as high as 50 %. When combined with centrifugation using a density gradient medium, the yield of such dimers could be further increased to 80 %. It is believed that this method will provide a simple and versatile approach to the high‐volume production of dimers from spherical colloids composed of different materials. These dimers may find widespread use in a range of applications such as fabrication of photonic crystals and fundamental studies related to colloidal science. 相似文献
28.
含硫化氢气井钻井过程中的腐蚀因素与防护研究 总被引:1,自引:0,他引:1
在含硫气井的钻井过程中对于HRC大于22的钻具钢材除了腐蚀疲劳之外,在pH值小于9的环境中会发生硫化物应力腐蚀破裂,这种破坏比腐蚀疲劳更突然、更快,使钻杆大量损坏。含硫气井在钻井过程中,由于湿硫化氢的出现,常常会出现油管、套管、钻井设备、钻井仪器以及对支持保护管柱的水泥环柱等腐蚀和损坏问题,为此,阐述了湿硫化氢的腐蚀特点、机理,归纳总结了影响腐蚀的因素,综述了如何在这些方面防止其腐蚀,使损失减小,为指导油管、套管防腐工程实践提供了依据。建议在钻井过程中采用碱性钻井液,其pH值可到9或更高(至pH值12),以减缓或防止钻井过程中电化学从硫化物应力腐蚀破裂;含硫气井用的钻杆应该间歇使用。钻杆停用堆置时间可使其放氢,使钻杆恢复韧性,防止硫化物应力腐蚀断裂。 相似文献
29.
浅谈如何有效学习计算机软件知识 总被引:1,自引:0,他引:1
黄霞 《湖南工业职业技术学院学报》2003,3(2):79-80
计算机软件知识的学习并不是完全线性的,而是不断循环往复、迭代的过程。本对如何深入、广泛、有效地学习计算机软件知识做出了一些探讨。 相似文献
30.
Image registration by "Super-curves" 总被引:4,自引:0,他引:4
Minghui Xia Bede Liu 《IEEE transactions on image processing》2004,13(5):720-732
We solve the 2-D affine image registration problem by curve matching and alignment. Our approach starts with a super-curve, which is formed by superimposing two affine related curves in one coordinate system. We use B-spline fusion technique to find a single B-spline approximation of the super-curve and a registration between the two curves simultaneously. This approach achieves superior accuracy and efficiency in curve matching and alignment. We then address the occlusion problem by finding partial match between the curves segmented using inflections and cusps, which are affine invariant. The combination of edge detection and curve alignment lead to accurate image registration. 相似文献