全文获取类型
收费全文 | 10253篇 |
免费 | 921篇 |
国内免费 | 361篇 |
专业分类
电工技术 | 200篇 |
综合类 | 775篇 |
化学工业 | 480篇 |
金属工艺 | 809篇 |
机械仪表 | 1285篇 |
建筑科学 | 1189篇 |
矿业工程 | 1510篇 |
能源动力 | 266篇 |
轻工业 | 104篇 |
水利工程 | 335篇 |
石油天然气 | 1506篇 |
武器工业 | 102篇 |
无线电 | 733篇 |
一般工业技术 | 1283篇 |
冶金工业 | 435篇 |
原子能技术 | 73篇 |
自动化技术 | 450篇 |
出版年
2024年 | 19篇 |
2023年 | 129篇 |
2022年 | 286篇 |
2021年 | 263篇 |
2020年 | 299篇 |
2019年 | 232篇 |
2018年 | 220篇 |
2017年 | 282篇 |
2016年 | 339篇 |
2015年 | 359篇 |
2014年 | 611篇 |
2013年 | 499篇 |
2012年 | 794篇 |
2011年 | 753篇 |
2010年 | 534篇 |
2009年 | 566篇 |
2008年 | 453篇 |
2007年 | 639篇 |
2006年 | 585篇 |
2005年 | 536篇 |
2004年 | 457篇 |
2003年 | 444篇 |
2002年 | 380篇 |
2001年 | 373篇 |
2000年 | 287篇 |
1999年 | 247篇 |
1998年 | 228篇 |
1997年 | 160篇 |
1996年 | 136篇 |
1995年 | 111篇 |
1994年 | 96篇 |
1993年 | 40篇 |
1992年 | 44篇 |
1991年 | 23篇 |
1990年 | 28篇 |
1989年 | 32篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1985年 | 2篇 |
1984年 | 7篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
2.
3.
4.
针对高河矿奥灰水文观测孔空水管锈蚀断裂漏水严重的问题,分析了存在的问题,制定了钻孔涌水封堵技术方案及相应的注浆施工工艺,并进行了为期7天的井下试验。封堵注浆压力达到6 MPa,使用注浆水泥50 t,水泥浆液凝固良好,注浆阀门打开后无出水现象。 相似文献
5.
针对古城煤矿S1303综采工作面切眼的地质构造与施工条件,提出了大断面切眼采用“锚网索+π型梁棚+预注浆”联合支护方案,有效地控制了大断面切眼留顶煤施工期间的支护难题,保障了S1303综采面切眼能够满足设计要求和如期完成施工,为同类条件下的切眼施工提供了一定参考。 相似文献
6.
To realize ultimately efficient signal processing, it is necessary to replace electrical signal processing circuits with optical ones. The optical micro-resonator, which localizes light at a certain spot, is an essential component in optical signal processing. Single-crystal calcium fluoride (CaF2) is the most suitable material for a highly efficient optical micro-resonator. The CaF2 resonator can only be manufactured by ultra-precision machining processes, because its crystal anisotropy does not allow the application of chemical etching. However, the optical micro-resonator's performance depends definitely on the surface integrity.This study investigated the relationship between surface quality after ultra-precision machining and crystal anisotropy. Firstly, crack initiation was investigated on the (1 0 0), (1 1 0), and (1 1 1) planes using the micro-Vickers hardness test. Secondly, brittle-ductile transition was investigated by orthogonal cutting tests. Finally, cutting performance of cylindrical turning was evaluated, which could be a suitable method for manufacturing the CaF2 resonator. The most difficult point in cylindrical turning of CaF2 is that the crystalline plane and cutting direction vary continuously. In order to manufacture the CaF2 optical micro-resonator more efficiently, analysis was conducted on crack initiation and surface quality of all crystallographic orientations from the perspective of slip system and cleavage. 相似文献
7.
This work is devoted to the stress–strain state of isotropic double curved shell with defect system. The construction is weakened by two non-through thickness (internal) cracks of different length and by a circular hole located between cracks. In this study we use the line-spring model. Within the framework of this model cracks are modeled as mathematical cuts of shell’s middle surface. This leads to a two-dimensional problem. The problem is reduced to a system of eight boundary integral equations. To ensure the uniqueness of solution an additional equation is added. In the numerical solution of the problem special quadrature formulas for singular integrals of Cauchy type and the finite difference method are applied. The influence of defects on each other for double curved shell has been investigated. The given theoretical results can be used for the calculation of structural elements with holes, cracks on the strength and fracture toughness in various branches of engineering. 相似文献
8.
M1080B无心外圆磨床砂轮及导轮宽度较窄,磨削轴承套圈外圆时,磨削效率低,托板架调整较为繁琐、皮带打滑、磨损较为严重。针对上述问题,提出了相应的解决办法,提高了磨削效率。 相似文献
9.
AbstractGeneralized thermoelastic interactions due to three-phase-lag time-nonlocal heat transfer in a Kelvin-Voigt type infinitely extended visco-thermoelastic continuum with cylindrical cavity has been investigated. The two-temperature generalized thermoelasticity theory has also been taken into account. The problem has been solved in the domain of Laplace on the assumption that the surface of the cavity is free from traction and is subjected to a smooth and time-dependent-heating effect. Laplace inversion of the transformed solutions has been carried out numerically. The obtained numerical data for different considerations are plotted in graphs to study the effects of time-nonlocal parameter, two-temperature parameter and visco-thermoelastic relaxation parameter on different thermoelastic quantities of physical interest. 相似文献
10.
套管屈服强度直接影响套管抗挤压性能,套管在加工孔过程中可能诱发孔眼附近材料发生金属相变,导致套管屈服强度不再均匀分布,进而影响套管抗挤压强度。在相同工况下,对比了P110完整套管和机加工孔套管的抗挤压强度,以此为参照组分析了相变区域面积和相变区域屈服强度对机加工孔套管抗挤压强度的影响。结果表明,机加工孔会改变材料屈服强度,进而影响套管抗挤压性能。随金属相变区域屈服强度减小,机加工孔套管抗挤压强度减弱;当金属相变区域屈服强度增大时,机加工孔套管抗挤压强度增强。且机加工孔套管相变区域面积对机加工孔套管抗挤压强度的影响随相变区域屈服强度增加而逐渐削弱。 相似文献