全文获取类型
收费全文 | 13344篇 |
免费 | 2057篇 |
国内免费 | 1613篇 |
专业分类
电工技术 | 653篇 |
技术理论 | 2篇 |
综合类 | 1157篇 |
化学工业 | 1032篇 |
金属工艺 | 968篇 |
机械仪表 | 1345篇 |
建筑科学 | 948篇 |
矿业工程 | 591篇 |
能源动力 | 392篇 |
轻工业 | 380篇 |
水利工程 | 324篇 |
石油天然气 | 614篇 |
武器工业 | 167篇 |
无线电 | 2399篇 |
一般工业技术 | 1128篇 |
冶金工业 | 500篇 |
原子能技术 | 163篇 |
自动化技术 | 4251篇 |
出版年
2024年 | 46篇 |
2023年 | 290篇 |
2022年 | 585篇 |
2021年 | 712篇 |
2020年 | 790篇 |
2019年 | 598篇 |
2018年 | 619篇 |
2017年 | 704篇 |
2016年 | 840篇 |
2015年 | 981篇 |
2014年 | 1548篇 |
2013年 | 1287篇 |
2012年 | 1447篇 |
2011年 | 1151篇 |
2010年 | 754篇 |
2009年 | 622篇 |
2008年 | 442篇 |
2007年 | 525篇 |
2006年 | 572篇 |
2005年 | 401篇 |
2004年 | 365篇 |
2003年 | 300篇 |
2002年 | 231篇 |
2001年 | 195篇 |
2000年 | 179篇 |
1999年 | 150篇 |
1998年 | 122篇 |
1997年 | 83篇 |
1996年 | 89篇 |
1995年 | 71篇 |
1994年 | 55篇 |
1993年 | 56篇 |
1992年 | 48篇 |
1991年 | 37篇 |
1990年 | 32篇 |
1989年 | 17篇 |
1988年 | 13篇 |
1987年 | 6篇 |
1986年 | 11篇 |
1985年 | 9篇 |
1984年 | 13篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
71.
Mixed reality can overlay and display 3D digital content in the real world, convey abstract concepts to users, and promote the understanding of complex tasks. However, the abstract graphics overlaid on the physical space may cause a certain cognitive load for local users and reduce the efficiency of collaboration. To improve the efficiency of remote collaboration, we conducted an elicitation study on assembly tasks, explored the user needs for collaboration, and defined the design goals of our remote collaboration method. Inspired by the mirror-neuron mechanism, we present an imitative collaboration method that allows local users to imitate the interaction behavior of remote users to complete tasks. We also propose a series of interaction methods for remote users to select, copy, and interact with the local point clouds to facilitate the expression of collaboration intentions. Finally, the results of a user study evaluating our imitative collaboration method on assembly tasks are reported, confirming that our method improves collaboration efficiency while reducing the cognitive load of local users. 相似文献
72.
采用三维激光扫描非接触倾斜测量法,可以高效获取矿仓中精矿产品的物料堆积形态。通过优化精矿盘点扫描测量流程,精准计算出矿仓库存量,提高了精矿盘点数据的准确性、测量的高效性和操作的安全性。 相似文献
73.
Molecular dynamics simulation is employed to study the depletion behaviors of perfluoro-lubricants under scanning laser heating for heat-assisted magnetic recording hard disk drives. A partial lubricant near the substrate is irradiated by the laser beam to mimic nano-scale heat transfer from disk to lubricant. The lubricant surface morphology and thickness profiles are examined to reveal the dynamic depletion behaviors. The localized temperature evolution is also evaluated to illustrate the direction-dependent ridge formation around the depletion zone. In addition, the effects of laser power and film thickness on lubricant depletion are explored. Although evaporation is enhanced significantly at high laser powers or for lubricant with thickness around one monolayer, thermodiffusion is the primary mode of lubricant depletion under scanning laser heating. 相似文献
74.
Shear Plugging and Frictional Behaviour of Composites and Fabrics Under Quasi‐static Loading 下载免费PDF全文
Experimental studies are presented on the shear plugging and frictional behaviour of composites and fabrics under quasi‐static loading. The primary focus is on the effect of specimen thickness on quasi‐static shear plugging behaviour. In the present study, quasi‐static shear plugging and through‐the‐thickness frictional tests are carried out on three types of materials. The materials investigated are 2D plain weave E‐glass/epoxy, 2D plain weave T300 carbon/epoxy and 2D plain weave E‐glass fabric. Typical results on shear plugging strength and frictional behaviour are presented. Effect of specimen thickness on quasi‐static shear plugging behaviour is also investigated. 相似文献
75.
F. Erchiqui 《Drying Technology》2014,32(8):946-959
This article analyzes the influence of frequency, temperature, moisture content, and structural orientation on the applicability of the Beer-Lambert law for various wood species using radio frequency and microwave radiation. To achieve this objective, the study compares the power dissipation computed from Maxwell's equation and Lambert's power law. The wood species considered are white oak (Quercus alba), Douglas fir (Pseudotsuga menziesii), trembling aspen (Populus tremuloides), white birch (Betula paperyfera), yellow birch (Betula alleghaniensis), sugar maple (Acer saccharum), and four commercial hardboards. The dielectric constant and dielectric loss factor are examined as a function of moisture conditions, temperature, frequencies, and the three principal structural orientations. The study involved 3,000 complex dielectric constants. It was found that the radial critical thickness is somewhat smaller than the tangential critical thickness (0.95 times smaller) and the longitudinal critical thickness is significantly smaller than the radial (0.52 times). It was demonstrated that the critical thickness L crit above which the Beer-Lambert law is valid for all of the wood species studied under various conditions obeys the following conditions: log10(L crt) = 0.999 log10(β?1) + 0.4122, where β?1 is the penetration depth (cm). In the case of microwave radiation, the critical thickness can be estimated from L crt = 2.615 β?1 ? 0.0626. Finally, a model is proposed to take into consideration the effect of moisture content with frequency (or with attenuation constant). 相似文献
76.
Aditya Putranto 《Drying Technology》2014,32(2):208-221
The reaction engineering approach (REA) is examined here to investigate its suitability as the local evaporation rate to be used in multiphase drying. For this purpose, REA is first implemented to model the convective drying of materials with various thicknesses. The relative activation energy, as the fingerprint of REA, generated from one size of a material is used to model the convective drying of the same material with different thicknesses. Because the results indicate that REA parameters can model the drying of materials with various thicknesses, REA can be scaled down to describe the local evaporation rate (at the microscale as affected by local composition and temperature). The relative activation energy is used to describe the global drying rate in modeling the local evaporation rate. REA is combined with a system of equations of conservation of heat and mass transfer in order to yield the spatial reaction engineering approach (S-REA) as a nonequilibrium multiphase drying model. By using S-REA, the spatial profiles of moisture content, concentration of water vapor, temperature, and local evaporation rate can be generated, which can assist in comprehending the transport phenomena. 相似文献
77.
输气管道日常管理中缺少对管道内杂质沉积量的预测,使得在实际生产中,输送效率成为确定管道清管周期、评价清管效果的唯一定量指标,具有一定的局限性。为此,根据含杂质沉积管道内流体动力学特点,采用欧拉法建立了输气管道杂质沉积预测模型,以川渝地区输气管线为例,模拟计算了管道内杂质沉积平均厚度、沉积量及含杂质沉积管道当量直径并将一次清管作业实际排污量与模拟结果进行对比,验证了模型。计算得出模拟计算排污量与实际排污量相差47.9m3,并得到了管道输气量和运行压差对杂质沉积量的影响规律:1压差一定时,管道杂质沉积量随输气量增大而降低;2起点压力一定时,管道杂质沉积量随压差增大而增大。 相似文献
78.
通过岩心、试油和分析化验等资料并结合测井资料,对鄂尔多斯盆地B区延长组长8储层进行"四性"关系研究。研究结果表明长8储层岩性主要为浅灰、深灰色细粒—极细粒长石岩屑砂岩或岩屑长石砂岩,成分成熟度较低而结构成熟度较高;储集空间以溶蚀孔隙为主,属于低孔、特低渗储层,岩性、物性的差异控制了储层油气的富集程度。确定了其储层物性下限标准为:孔隙度为7.5%,渗透率为0.15×10-3μm2;电性下限标准为:电阻率为31Ω·m。声波时差为220μs/m;含水饱和度小于等于62%。该研究为以后的油气勘探与开发工作提供了理论依据。 相似文献
79.
80.