全文获取类型
收费全文 | 165647篇 |
免费 | 68533篇 |
国内免费 | 46066篇 |
专业分类
电工技术 | 27105篇 |
综合类 | 20307篇 |
化学工业 | 20508篇 |
金属工艺 | 24303篇 |
机械仪表 | 5286篇 |
建筑科学 | 10734篇 |
矿业工程 | 12570篇 |
能源动力 | 7832篇 |
轻工业 | 19241篇 |
水利工程 | 6962篇 |
石油天然气 | 11589篇 |
武器工业 | 3491篇 |
无线电 | 27883篇 |
一般工业技术 | 27419篇 |
冶金工业 | 5742篇 |
原子能技术 | 1085篇 |
自动化技术 | 48189篇 |
出版年
2024年 | 2419篇 |
2023年 | 4091篇 |
2022年 | 4296篇 |
2021年 | 4752篇 |
2020年 | 8083篇 |
2019年 | 17672篇 |
2018年 | 19074篇 |
2017年 | 20373篇 |
2016年 | 20139篇 |
2015年 | 18829篇 |
2014年 | 17277篇 |
2013年 | 16245篇 |
2012年 | 15376篇 |
2011年 | 11566篇 |
2010年 | 10565篇 |
2009年 | 7604篇 |
2008年 | 5648篇 |
2007年 | 5161篇 |
2006年 | 4210篇 |
2005年 | 4017篇 |
2004年 | 7125篇 |
2003年 | 5802篇 |
2002年 | 5521篇 |
2001年 | 4830篇 |
2000年 | 4433篇 |
1999年 | 4204篇 |
1998年 | 3827篇 |
1997年 | 3434篇 |
1996年 | 3309篇 |
1995年 | 3381篇 |
1994年 | 2790篇 |
1993年 | 2599篇 |
1992年 | 2536篇 |
1991年 | 1839篇 |
1990年 | 1436篇 |
1989年 | 1347篇 |
1988年 | 1024篇 |
1987年 | 295篇 |
1986年 | 256篇 |
1985年 | 193篇 |
1984年 | 129篇 |
1982年 | 139篇 |
1981年 | 144篇 |
1978年 | 97篇 |
1976年 | 225篇 |
1975年 | 203篇 |
1972年 | 235篇 |
1971年 | 127篇 |
1969年 | 97篇 |
1960年 | 205篇 |
排序方式: 共有10000条查询结果,搜索用时 866 毫秒
961.
通过对铸造湿型小件产品缺陷典型实例的原因分析,从型砂的选择及配制、造型工艺、浇注工艺等方面提出控制缺陷产生的工艺方法。 相似文献
962.
963.
964.
Sajan D. George Rajesh Komban K. G. K. Warrier P. Radhakrishnan V. P. N. Nampoori C. P. G. Vallabhan 《International Journal of Thermophysics》2007,28(1):123-132
The laser induced non-destructive photoacoustic technique has been employed to measure the thermal diffusivity of lanthanum
phosphate ceramics prepared by the sol–gel route. The thermal diffusivity value was evaluated by knowing the transition frequency
between the thermally thin to thermally thick region from the log–log plot of photoacoustic amplitude versus chopping frequency.
Analysis of the data was carried out on the basis of the one-dimensional model of Rosencwaig and Gersho. The present investigation
reveals that the sintering temperature has great influence on the propagation of heat carriers and hence on the thermal diffusivity
value. The results were interpreted in terms of variations in porosity with sintering temperature as well as with changes
in grain size. 相似文献
965.
We present an analysis of a stochastic model of the vascular endothelial growth factor (VEGF) receptor. This analysis addresses the contribution of ligand-binding-induced oligomerization, activation of src-homology 2 domain-carrying kinases and receptor internalization in the overall behaviour of the VEGF/VEGF receptor (VEGFR) system. The analysis is based upon a generalization of a Wentzel-Kramers-Brillouin (WKB) approximation of the solution of the corresponding master equation. We predict that tumour-mediated overexpression of VEGFRs in the endothelial cells (ECs) of tumour-engulfed vessels leads to an increased sensitivity of the ECs to low concentrations of VEGF, thus endowing the tumour with increased resistance to anti-angiogenic treatment. 相似文献
966.
We have calculated thermal conductivity of alumina nanofluids (with water and ethylene glycol as base fluids) using temperature
as well as concentration-dependent viscosity, η. The temperature profile of η is obtained using Gaussian fit to the available experimental data. In the model, the interfacial resistance effects are incorporated
through a phenomenological parameter α. The micro-convection of the alumina nanoparticle (diameter less than 100 nm) is included through Reynolds and Prandtl numbers.
The model is further improved by explicitly incorporating the thermal conductivity of the nanolayer surrounding the nanoparticles.
Using this improved model, thermal conductivity of copper nanofluid is calculated. These calculations capture the particle
concentration-dependent thermal conductivity and predict the dependence of the thermal conductivity on the size of the nanoparticle.
These studies are significant to understand the underlying processes of heat transport in nanofluids and are crucial to design
superior coolants of next generation. 相似文献
967.
A mild thermal treatment of wood leads to improved macroscopic properties (dimensional stabilization and resistance against fungal degradation). The chemical modifications induced by the thermal treatment were investigated by means of DRIFT spectroscopy on wood blocks in order to explain the new macroscopic properties on a molecular level. The formation of new ether linkage was observed in addition to the well-known acidic hydrolysis reactions of wood. Fungal attack was found to take place even after thermal degradation of pentosanes by a standard oxidative way. A competition between depolymerization and condensation reactions was observed. 相似文献
968.
969.
970.