全文获取类型
收费全文 | 28994篇 |
免费 | 2685篇 |
国内免费 | 1915篇 |
学科分类
工业技术 | 33594篇 |
出版年
2024年 | 136篇 |
2023年 | 463篇 |
2022年 | 715篇 |
2021年 | 889篇 |
2020年 | 975篇 |
2019年 | 831篇 |
2018年 | 791篇 |
2017年 | 908篇 |
2016年 | 966篇 |
2015年 | 927篇 |
2014年 | 1479篇 |
2013年 | 1832篇 |
2012年 | 1824篇 |
2011年 | 1948篇 |
2010年 | 1516篇 |
2009年 | 1621篇 |
2008年 | 1410篇 |
2007年 | 1832篇 |
2006年 | 1755篇 |
2005年 | 1542篇 |
2004年 | 1336篇 |
2003年 | 1208篇 |
2002年 | 1091篇 |
2001年 | 960篇 |
2000年 | 795篇 |
1999年 | 679篇 |
1998年 | 536篇 |
1997年 | 474篇 |
1996年 | 430篇 |
1995年 | 350篇 |
1994年 | 283篇 |
1993年 | 198篇 |
1992年 | 161篇 |
1991年 | 135篇 |
1990年 | 144篇 |
1989年 | 118篇 |
1988年 | 61篇 |
1987年 | 45篇 |
1986年 | 35篇 |
1985年 | 33篇 |
1984年 | 32篇 |
1983年 | 19篇 |
1982年 | 23篇 |
1981年 | 10篇 |
1980年 | 16篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1964年 | 8篇 |
1956年 | 5篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
吐哈油田部分区块地层压力系数小于0.9,常规水基压井液对储层伤害大,若使用油基压井液成本高,环境污染严重。通过实验优选出了一种低密度水基微泡沫压井液。该压井液具有密度低、泡沫强度高、稳定性好、携砂能力强等优点。现场应用表明,低密度微泡沫压井液稳定时间大于48 h,密度在0.70~0.99 g/cm3之间可调,抗油污染能力强,抗油大于8%,抗温在100℃以上,岩心污染后渗透率恢复值大于80%;并且施工方便,成本低,具有储层保护能力,使用微泡沫压井液的井表皮系数在0.20~2.34之间。 相似文献
4.
Depletion and hillock formation were examined in-situ in a scanning electron microscope (SEM) during electromigration of bamboo
Al interconnect segments. Hillocks formed directly at the anode ends of the segments by epitaxial addition of Al at the bottom
Al/TiN interface. Depletion occurred nonuniformly from the cathode end and stopped once the distance between the leading void
and the hillock reached the critical length for electromigration at the given current density. A modified equation for the
drift velocity is proposed, which includes the effect of nonuniform depletion and predicts that interconnects with nonuniform
depletion are more reliable than those with uniform depletion. 相似文献
5.
6.
7.
3D characterization and analysis of particle shape using X-ray microtomography (XMT) 总被引:2,自引:0,他引:2
C.L. Lin 《Powder Technology》2005,154(1):61-69
8.
Dongchang Sun Liyong Tong 《International journal for numerical methods in engineering》2004,60(11):1911-1932
A novel finite element model is presented for static and dynamic analysis of composite plates integrated with a laminated piezoelectric layer, a host laminated composite plate and an adhesive layer between them. A new adhesive element is developed which includes both peel and shear effects in the adhesive layer based on first‐order shear deformation plate theory. The thin adhesive layer between the piezoelectric layer and the host plate is modelled by assuming that it carries constant shear and peel strains throughout its thickness. In addition, a weighted static shape control scheme for finding the optimal voltage distribution for static shape control is given. By selecting different weighting matrices, a variety of items such as displacements, slopes, curvatures, strains and even generalized forces, can be included in finding the optimal actuating voltage for static shape control. The present model is validated by comparing with those results available in the literature. The numerical results show that the weighted linear least method can give a satisfactory voltage distribution to best match the desired shape. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
9.
O. Khamman 《Materials Letters》2007,61(3):639-643
The solid-state mixed oxide method via a rapid vibro-milling technique is explored in the preparation of single-phase nickel niobate (NiNb2O6) powders. The formation of the NiNb2O6 phase in the calcined powders has been investigated as a function of calcination conditions by TG-DTA and XRD techniques. Morphology, particle size and chemical composition have been determined via a combination of SEM and EDX techniques. It has been found that the minor phases of unreacted NiO and Nb2O5 precursors and the Ni4Nb2O9 phase tend to form together with the columbite NiNb2O6 phase, depending on calcination conditions. More importantly, it is seen that optimization of calcination conditions can lead to a single-phase NiNb2O6 in an orthorhombic phase. 相似文献
10.
Bedich ika Helena Bendov Ivan Macha
《Chemical Engineering and Processing: Process Intensification》2005,44(12):1312-1319
A procedure has been proposed for the estimation of the terminal falling velocity of non-spherical particles moving in a Carreau model fluid in the transition flow region. The procedure is based on a modification of the relationship formerly developed for the fall of spherical particles including the particle dynamic shape factor. The suitability of the proposed procedure has been confirmed by good agreement between experimental and calculated terminal falling velocity data. In the experiments, the terminal falling velocity of short cylinders and rectangular prisms in polymer solutions of different measure of shear thinning and elasticity has been measured. 相似文献