全文获取类型
收费全文 | 43082篇 |
免费 | 4158篇 |
国内免费 | 2450篇 |
专业分类
电工技术 | 1916篇 |
技术理论 | 2篇 |
综合类 | 3042篇 |
化学工业 | 10000篇 |
金属工艺 | 1535篇 |
机械仪表 | 2375篇 |
建筑科学 | 2169篇 |
矿业工程 | 1120篇 |
能源动力 | 1359篇 |
轻工业 | 6747篇 |
水利工程 | 1686篇 |
石油天然气 | 2266篇 |
武器工业 | 355篇 |
无线电 | 3636篇 |
一般工业技术 | 4537篇 |
冶金工业 | 1867篇 |
原子能技术 | 1048篇 |
自动化技术 | 4030篇 |
出版年
2024年 | 193篇 |
2023年 | 653篇 |
2022年 | 1060篇 |
2021年 | 1445篇 |
2020年 | 1564篇 |
2019年 | 1536篇 |
2018年 | 1409篇 |
2017年 | 1623篇 |
2016年 | 1783篇 |
2015年 | 1719篇 |
2014年 | 2612篇 |
2013年 | 2903篇 |
2012年 | 3193篇 |
2011年 | 3166篇 |
2010年 | 2241篇 |
2009年 | 2324篇 |
2008年 | 2059篇 |
2007年 | 2554篇 |
2006年 | 2362篇 |
2005年 | 2032篇 |
2004年 | 1653篇 |
2003年 | 1519篇 |
2002年 | 1308篇 |
2001年 | 1110篇 |
2000年 | 969篇 |
1999年 | 865篇 |
1998年 | 662篇 |
1997年 | 570篇 |
1996年 | 426篇 |
1995年 | 415篇 |
1994年 | 313篇 |
1993年 | 276篇 |
1992年 | 241篇 |
1991年 | 148篇 |
1990年 | 114篇 |
1989年 | 101篇 |
1988年 | 90篇 |
1987年 | 54篇 |
1986年 | 50篇 |
1985年 | 63篇 |
1984年 | 54篇 |
1983年 | 37篇 |
1982年 | 30篇 |
1981年 | 26篇 |
1980年 | 28篇 |
1979年 | 12篇 |
1978年 | 11篇 |
1976年 | 10篇 |
1964年 | 20篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
L. Gao P. Hrter Ch. Linsmeier J. Gstttner R. Emling D. Schmitt-Landsiedel 《Materials Science in Semiconductor Processing》2004,7(4-6):331
Deposition of Ag films by direct liquid injection-metal organic chemical vapor deposition (DLI-MOCVD) was chosen because this preparation method allows precise control of precursor flow and prevents early decomposition of the precursor as compared to the bubbler-delivery. Silver(I)-2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octanedionato-triethylphosphine [Ag(fod)(PEt3)] as the precursor for Ag CVD was studied, which is liquid at 30 °C. Ag films were grown on different substrates of SiO2/Si and TiN/Si. Argon and nitrogen/hydrogen carrier gas was used in a cold wall reactor at a pressure of 50–500 Pa with deposition temperature ranging between 220 °C and 350 °C. Ag films deposited on a TiN/Si diffusion barrier layer have favorable properties over films deposited on SiO2/Si substrate. At lower temperature (220 °C), film growth is essentially reaction-limited on SiO2 substrate. Significant dependence of the surface morphology on the deposition conditions exists in our experiments. According to XPS analysis pure Ag films are deposited by DLI-MOCVD at 250 °C by using argon as carrier gas. 相似文献
2.
Gas/liquid mass transfer has been investigated using a stirred vessel gas/liquid contactor using non‐Newtonian media and carbon dioxide as absorbent and gas phase, respectively. The volumetric mass transfer coefficients at different operational variables have been determined. Non‐Newtonian media (liquid phase) were prepared as aqueous solutions of sodium carboxymethyl cellulose salt. The influence of the rheological properties, polymer concentration, stirring rate, and gas flow rate on mass transfer was studied for these liquid phases. Kinematic viscosity and density experimental data were used to calculate the average molecular weight corresponding to the polymer employed. The Ostwald model has been used to fit the rheological behavior of aqueous solutions of the polymer employed as absorbent phase. Reasonably good agreement was found between the predictions of the proposed models and the experimental data of mass transfer coefficients. 相似文献
3.
Dynamics of liquid-filled spacecraft 总被引:1,自引:0,他引:1
A method is presented for simulating coupled liquid-solid dynamics. An important example of a coupled liquid-solid system is a satellite carrying fuel. The dynamics of the satellite and the onboard fuel influence each other, which may lead to satellite motion that is uncontrollable. For better understanding of the complex dynamics of coupled systems, a numerical model is developed. The model consists of two parts. The first part that solves the liquid motion is only briefly discussed here. The focus in this paper is on the way in which the dynamics of the liquid and the solid body are coupled. For this, the governing equations are presented in which terms appear that represent the force and torque on the solid body due to the sloshing liquid. The governing equations are rewritten such that the discrete approximation of these equations can be integrated in a stable manner for arbitrary liquid/solid mass ratios. Results are presented demonstrating the stability of the present model. A grid-refinement study and a time-step analysis are performed. Finally, the flat-spin motion of a satellite, partially filled with liquid, that flew in 1992 as part of the Wet Satellite Model experiment is studied. Results from the simulation are compared with the actual flight data. 相似文献
4.
Thanapalan Murugesan G. S. Venkat Rathnam S. Panduranga Rao P. Gangadhar Rao 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,63(3):290-294
In the present study of gas–liquid contactors, mean residence/contact time was calculated from knowledge of superficial velocity and the gas phase hold-up, for various gas rates and impeller geometry and speeds, and compared with values obtained from RTD measurements. A new correlation, involving Flow Number, Froude Number, system geometry and the physical properties, is proposed. This uses the authors data and those available in literature. 相似文献
5.
本文对芝麻营养保健成分的提取进行了系统的研究。确定了芝麻营养原液的制取工艺。为充分发挥芝麻的营养保健作用开辟了新的途径。 相似文献
6.
超细Fe3O4粒子表面包覆酞菁钴性质研究 总被引:3,自引:1,他引:2
本文研究了合成载氧体的金属有机化学液相淀积法制造工艺,所得产物经TEM、XPS、Moss-bauer谱和B-H仪等手段,研究了它的结构和磁性能。实验表明,酞青钴以薄层形式包覆在Fe_3O_4的表面,封闭了Fe_3O_4的表面孔洞,稳定了Fe_3O_4的物相,增强了磁性能。 相似文献
7.
将薄膜电容真空计的测量室接于被测密闭容器,静态真空室接于一个比较容器,即组成一台压差式漏率测试仪。首先使两容器压力平衡,真空计读数为零。当被测容器存在漏孔时,真空计薄膜两侧形成压差,真空计指示读数,继而计算出该容器的漏率。应用商品真空计在抽真空测试时,检测的最小可测漏率达10-4~10-5Pa·L/s;而在充压测试时,因受气体温度变化的影响,灵敏度会降低几个量级。该仪器有可能具备寻找漏孔位置和确定漏孔漏率的功能。 相似文献
8.
Banded textures produced in a thermotropic liquid crystal polymer by shearing between glass slides are examined by using both transmission electron and polarized light microscopy. The periodic variation in director orientation about the shear axis, as measured by light microscopy, is shown to be distinctly different from that indicated by electron diffraction. Measurements of birefringence and observation of Zernicke phase contrast indicate periodic variations in optical properties of the polymer, in step with the bands. Such effects are accounted for in terms of a synchronous rotation of the planar aromatic groups about the molecular chain axes. Evidence for an out-of-plane component of molecular orientation is also presented. 相似文献
9.
摩擦强度对薄膜表面形态的作用:原子力显微镜下的观察 总被引:2,自引:2,他引:0
展示了摩擦强度对聚酰亚胺薄膜表面形态的影响,原子力显微图像显示,机械摩擦会使聚酰亚胺薄膜表面上形成微沟槽,这些沟槽的表面具有丰富的表面精细构造。原子显微图像还揭示了机械摩擦可以改变被磨擦聚酰亚胺膜的表面形态。 相似文献
10.
In this paper, the test results of liquid injection impact on the performance of new alternative refrigerant mixtures such as: R-410A, R-507, R-407C and R-404A are discussed, analysed and presented. The test results were obtained using an air-source heat pump set-up with enhanced surface tubing under various liquid injection ratios. Performance tests were conducted according to the ARI/ASHRAE standards. The performance data demonstrated that as liquid injection ratio increases, compressor head pressure and discharge temperature decrease. This has a positive effect in protecting the compressor. The effect of liquid injection on mixture behaviour varies from one mixture to another depending upon the mixture's composition. Furthermore, liquid injection appears to have a significant influence on R-410A behaviour compared to the other mixtures in question. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献