全文获取类型
收费全文 | 112356篇 |
免费 | 10815篇 |
国内免费 | 6475篇 |
专业分类
电工技术 | 9142篇 |
技术理论 | 4篇 |
综合类 | 9909篇 |
化学工业 | 19192篇 |
金属工艺 | 10973篇 |
机械仪表 | 5790篇 |
建筑科学 | 8804篇 |
矿业工程 | 3289篇 |
能源动力 | 5778篇 |
轻工业 | 6695篇 |
水利工程 | 2469篇 |
石油天然气 | 7373篇 |
武器工业 | 943篇 |
无线电 | 10519篇 |
一般工业技术 | 12160篇 |
冶金工业 | 8014篇 |
原子能技术 | 1793篇 |
自动化技术 | 6799篇 |
出版年
2024年 | 491篇 |
2023年 | 1559篇 |
2022年 | 2882篇 |
2021年 | 3468篇 |
2020年 | 3737篇 |
2019年 | 3146篇 |
2018年 | 2987篇 |
2017年 | 3804篇 |
2016年 | 4164篇 |
2015年 | 4372篇 |
2014年 | 6764篇 |
2013年 | 6979篇 |
2012年 | 8409篇 |
2011年 | 8961篇 |
2010年 | 6245篇 |
2009年 | 6344篇 |
2008年 | 5728篇 |
2007年 | 7270篇 |
2006年 | 6738篇 |
2005年 | 5642篇 |
2004年 | 4880篇 |
2003年 | 4347篇 |
2002年 | 3546篇 |
2001年 | 3150篇 |
2000年 | 2592篇 |
1999年 | 2084篇 |
1998年 | 1569篇 |
1997年 | 1389篇 |
1996年 | 1236篇 |
1995年 | 989篇 |
1994年 | 885篇 |
1993年 | 620篇 |
1992年 | 577篇 |
1991年 | 492篇 |
1990年 | 383篇 |
1989年 | 273篇 |
1988年 | 216篇 |
1987年 | 130篇 |
1986年 | 110篇 |
1985年 | 99篇 |
1984年 | 101篇 |
1983年 | 70篇 |
1982年 | 53篇 |
1981年 | 25篇 |
1980年 | 38篇 |
1979年 | 27篇 |
1977年 | 10篇 |
1975年 | 6篇 |
1959年 | 18篇 |
1951年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
E.F. Thacher 《Energy Conversion and Management》1985,25(4):519-525
With the object of evaluating its importance to thermoelectric generator design, heat loss is introduced into the standard thermoelectric generator design theory. The theory for both the constant hot and cold junction temperatures model and the constant heat input model are so modified. The modification is first order and, therefore, is limited to small leg heat-transfer coefficients. Numerical results using representative properties show that significant differences can exist between the optimum geometry and performance of a generator idealized as lossless and those of a generator designed by the modified theory. The largest differences occur with the constant heat input model. 相似文献
52.
Research has continued in the field sidechain liquid crystal polymers over recent years, but it is becoming clearer that this research is being directed away from the traditional technology areas of electro-optic devices and researchers are developing new and exciting applications for this novel state of matter. 相似文献
53.
易损/危险品物流监测智能微系统 总被引:1,自引:0,他引:1
一种基于数据采集、射频识别的信息采集系统,可以采集存储物流过程中超过阈值的振动、湿度以及温度,并记录对应的时间,然后通过无线通信向外发送记录的数据。本系统由三部分组成,包括基于加速度传感器、温/湿度传感器的数据采集模块、基于RFID的无线通信模块及报警模块。本系统不仅可为易损邮寄物品保驾护航,还可对流通中的危险品状态进行实时监测,能应用于多种恶劣环境,实时将报警消息发送至运输人员手中,及时发现问题,提高运输效率,有效地降低运输货品的破损率和危险品的事故率。 相似文献
54.
模拟集成温度传感器设计 总被引:1,自引:0,他引:1
介绍了一种模拟集成温度传感器的电路设计。该电路利用双极性晶体管基极-发射极结压降与热力学温度T成比例的关系来实现温度的测量,并在6μm双极工艺线上投片成功。该电路在常温25℃下输出298.2μA的电流,在-55℃~150℃的工作温度范围内的误差不超过±3℃,非线性度误差不超过±0.4℃。 相似文献
55.
56.
High cycle fatigue behaviour of Ti–6Al–4V alloy was studied at 623 K and 723 K. Fatigue strength decreased at elevated temperatures compared with at ambient temperature. In the short life regime, fatigue strength was lower at 723 K than at 623 K, but in the long life regime it was nearly the same at both temperatures. At elevated temperatures, cracks were generated earlier at applied stresses below the fatigue limit at ambient temperature, indicating lowered crack initiation resistance. Small cracks grew faster at elevated temperatures than at ambient temperature, which became more noticeable with increasing temperature. After allowing for the elastic modulus, small cracks still grew faster at elevated temperatures. 相似文献
57.
A programmed temperature technique has been developed for the measurement of the self-diffusion coefficients of additives in polymers. This has been applied to the diffusion of three dialkylphthalate plasticizers in poly(vinyl chloride). Values of the self-diffusion coefficients and the calculated activation energies obtained in this way have been compared with values previously obtained from measurements at constant temperature. It has been shown that the programmed temperature technique gives a very rapid method for the estimation of the activation energy of self-diffusion. 相似文献
58.
M. Rahman 《化学,工程师,技术》1975,47(17):729-729
59.
Viscosity data over a temperature range of 37-115°C and a pressure range of 0-10 MPa gauge are presented for a Cold Lake bitumen sample. These data show that the compression of Cold Lake bitumen results in a significant increase in its viscosity. Results are compared with those from a similar study on an Athabasca bitumen sample. Also presented are two correlations for the effects of pressure and temperature on the viscosity of Cold Lake bitumen. 相似文献
60.
Cheng-Liang Chang Hsuan Chang Yuan-Cheng Chang 《Journal of the Chinese Institute of Chemical Engineers》2007
A hybrid mathematic model for pervaporation is proposed which incorporates the concepts of solution-diffusion model and pore model. The model allows performance prediction as well as the establishment of the internal concentration and pressure profiles within the membrane. The model parameters specific to the particular membrane and mixture system are determined using liquid sorption and pervaporation experimental data. The model is experimentally examined using ethanol–water mixtures and poly(dimethyl siloxane)–poly(vinyldiene fluoride) (PDMS–PVDF) composite membranes. The characteristics of flux and separation factor predicted using the model are in fair agreement with the experimental data under various feed concentrations and downstream pressures for different membrane arrangements, including single-layer, reverse single-layer and double-layer PDMS–PVDF composite membranes. Internal profiles of pressure, concentration and component mole fraction can be established using the model. Concentration polarization phenomena for ethanol and water are located at membrane interfaces and vapor–liquid interfaces, respectively. Performances of several different membrane designs are compared using the model. 相似文献