全文获取类型
收费全文 | 15560篇 |
免费 | 1207篇 |
国内免费 | 779篇 |
专业分类
电工技术 | 1013篇 |
综合类 | 1152篇 |
化学工业 | 1723篇 |
金属工艺 | 2102篇 |
机械仪表 | 2700篇 |
建筑科学 | 707篇 |
矿业工程 | 447篇 |
能源动力 | 470篇 |
轻工业 | 929篇 |
水利工程 | 238篇 |
石油天然气 | 398篇 |
武器工业 | 161篇 |
无线电 | 1033篇 |
一般工业技术 | 2031篇 |
冶金工业 | 1809篇 |
原子能技术 | 79篇 |
自动化技术 | 554篇 |
出版年
2024年 | 80篇 |
2023年 | 225篇 |
2022年 | 371篇 |
2021年 | 404篇 |
2020年 | 520篇 |
2019年 | 395篇 |
2018年 | 411篇 |
2017年 | 486篇 |
2016年 | 518篇 |
2015年 | 573篇 |
2014年 | 946篇 |
2013年 | 1081篇 |
2012年 | 1045篇 |
2011年 | 1101篇 |
2010年 | 794篇 |
2009年 | 870篇 |
2008年 | 745篇 |
2007年 | 1024篇 |
2006年 | 948篇 |
2005年 | 757篇 |
2004年 | 617篇 |
2003年 | 564篇 |
2002年 | 510篇 |
2001年 | 428篇 |
2000年 | 368篇 |
1999年 | 290篇 |
1998年 | 288篇 |
1997年 | 234篇 |
1996年 | 209篇 |
1995年 | 163篇 |
1994年 | 135篇 |
1993年 | 85篇 |
1992年 | 89篇 |
1991年 | 65篇 |
1990年 | 51篇 |
1989年 | 33篇 |
1988年 | 35篇 |
1987年 | 18篇 |
1986年 | 9篇 |
1985年 | 12篇 |
1984年 | 14篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1977年 | 4篇 |
1966年 | 2篇 |
1965年 | 1篇 |
1959年 | 3篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
硬粒子对聚合物材料表面的冲击摩擦研究 总被引:3,自引:3,他引:0
冲击摩擦为接触面切向与法向冲量之比。用聚合物材料试件与弹簧钢片组成振动测试系统 ,硬粒子以一定入射角冲击试件水平面引起系统振动 ,接触冲量通过振幅反映出来 ,记录初始振幅值而计算出一个冲击过程的冲击摩擦因数。结果表明 ,当入射角α在 2 5°-60°变化时 ,冲击摩擦因数f从 0 .5降至 0 .2左右。文章同时分析讨论了摩擦对聚合物表面接触强度的影响。 相似文献
72.
共聚物水凝胶的合成及其溶胀性能研究 总被引:3,自引:1,他引:2
以过氧化二苯甲酰(BPO)为引发剂,合成了N-乙烯基吡咯烷酮(NVP)-甲基丙烯酸肛羟乙酯(HEMA)-甲基丙烯酸丁酯(BMA)共聚物水凝胶,可作为软性角膜接触镜材料。探讨了不同比例的NVP、HEMA、BMA对材料溶胀性能的影响。 相似文献
73.
This paper presents some results from a totally new and powerful fusion between automated, digital photoelastic techniques and mathematical analysis of a crack experiencing closure. In essence, real-time photoelastic stress field data is acquired and fitted to a Muskhelishvili complex potential model of a loaded crack experiencing closure. The fit entails optimisation of multiple variables via a memetic algorithm, which combines a genetic algorithm and a local search. From observations made in this work, it is proposed that the plastic enclave around a crack tip will shield the crack from the full influence of the applied stress field. Furthermore, the effects of this ‘back stress’ are overcome by the applied tensile load in a way that, often, cannot be readily correlated with crack contact length, wake contact force, or with compliance. 相似文献
74.
The metal contact method of rapid freezing is greatly improved by irradiating the specimen with microwaves at 2.45 GHz for a short period of time (50 ms), while pushing the specimen onto the surface of the copper block cooled by liquid N2. The microwave irradiation, together with two technical improvements (a light-mass plunger and a recently developed β-gel shock absorber) for preventing bounce, produces a good freezing zone for squid retina, with high reproducibility for each experimental trial, extending from the contact surface to a depth of about 15 μm, which is comparable to the depth obtained by the metal contact method using liquid He in the absence of microwave irradiation. A good freezing zone was also experimentally demonstrated in specimens of rat liver and heart muscle. Microwave irradiation does not have appreciable effects on the ultrastructure of squid retina. The mechanism underlying the improvement in the rapid freezing under the microwave irradiation is discussed. 相似文献
75.
Woo-Seok Cheong 《Journal of Electronic Materials》2003,32(4):249-253
For the lowest resistance, it is required to have the epitaxial silicon contact between the silicon plug and the substrate
and good step coverage at the high aspect-ratio contact holes, simultaneously. In this work, a double polysilicon (DPS) deposition
technique was proposed for the requirements. The first, thin silicon layer is deposited in a single-wafer process chamber
with an in-situ H2-RTP (rapid thermal process) treatment for the epitaxial contact, and the second silicon layer is formed in a batch-type furnace
for good step coverage. From chain resistance, Kelvin Rc, and current-voltage (I–V) measurement, the DPS process meets both low resistance and good uniformity, so that it suggests
a breakthrough in the small-sized, semiconductor device application. 相似文献
76.
77.
汽车侧倾稳定性的动态仿真(一) --数学模型的建立 总被引:1,自引:0,他引:1
本文通过对独立悬架和非独立悬架侧倾运动特性的分析并结合采用已有的轮胎力学模型,建立了反映独立悬架和非独立悬架侧倾运动特性的数学模型。在此基础上,根据汽车侧倾时悬挂质量对前后悬架的力和力矩作用来组合前后悬架,我们得到了双轴汽车在稳态转向时侧倾运动的数学模型。通过组合不同的前后悬架,这个数学模型可以反映各种悬架配置的双轴汽车。它主要是针对汽车进行稳态转向时的侧倾情况,考虑了汽车的结构参数、惯性参数以及悬架、轮胎的柔性形变对汽车侧倾运动特性和抗侧翻能力的影响。它可以用来计算一定横向加速度下汽车的侧倾反应和轮胎的载荷变化,也可以用来计算一辆确定的汽车在保持侧倾稳定性的前提下所能达到的最大横向加速度,还可以用来分析各项参数对汽车侧倾稳定性的影响。 相似文献
78.
79.
Schottky diodes were built on different polycrystalline diamond films grown by Microwave Plasma and Hot Filament Chemical Vapor Deposition and their electrical properties were studied. The barrier height increased with the diamond film quality and the corresponding ideality factor decreased. Even though the lower-quality HFCVD film displayed poor rectifying properties, it was found to be much less sensitive to variations in the operating conditions (air vs. vacuum). The activation energies of the films depend on morphological parameters, as preferable grain size or orientation. The bulk conduction also depends on the quality of the deposited films, changing from ohmic to trap-free or shallow trap SCLC and SCLC with an exponential distribution of traps. The hypothesis of using the electrical measurements as an indicator for film quality has been discussed. 相似文献
80.
M. M. I. HAMMOUDA I. G. EL-BATANONY H. E. M. SALLAM 《Fatigue & Fracture of Engineering Materials & Structures》2003,26(7):627-639
An understanding into the macro kinetic and kinematic behaviour of fretted surfaces is provided. Making use of a modified version of a previously developed in‐house two‐dimensional elastic–plastic finite element analysis numerically simulates flat contact pad fretting fatigue tests. Basic macro mechanics concepts are adopted to idealise two bodies with rough contact surfaces and loaded at two different sites with arbitrary axial loading profiles. A time scale factor is devised to recognise the earliest candidate out of the events possibly accommodated at each loading increment. The present analysis utilises a relevant experimental set up developed in the Structural Integrity Research Institute of the University of Sheffield as an application. Computational results accurate to within 1.2% and corresponding to one contact pad span and six constant normal loads acting individually with four amplitudes of two sinusoidal axial load cycles are presented. The present computations include (1) the development of the global and local normal and tangential reactions and relative sliding displacement acting along the fretting surfaces and (2) contact pad deformation, generated stress fields and plasticity development within the neighbouring region of the fretted area. 相似文献