全文获取类型
收费全文 | 6026篇 |
免费 | 475篇 |
国内免费 | 46篇 |
专业分类
电工技术 | 100篇 |
综合类 | 43篇 |
化学工业 | 1323篇 |
金属工艺 | 131篇 |
机械仪表 | 282篇 |
建筑科学 | 238篇 |
矿业工程 | 5篇 |
能源动力 | 258篇 |
轻工业 | 518篇 |
水利工程 | 32篇 |
石油天然气 | 21篇 |
无线电 | 1016篇 |
一般工业技术 | 1182篇 |
冶金工业 | 406篇 |
原子能技术 | 62篇 |
自动化技术 | 930篇 |
出版年
2024年 | 4篇 |
2023年 | 58篇 |
2022年 | 105篇 |
2021年 | 217篇 |
2020年 | 146篇 |
2019年 | 169篇 |
2018年 | 201篇 |
2017年 | 207篇 |
2016年 | 218篇 |
2015年 | 206篇 |
2014年 | 275篇 |
2013年 | 461篇 |
2012年 | 392篇 |
2011年 | 424篇 |
2010年 | 371篇 |
2009年 | 342篇 |
2008年 | 335篇 |
2007年 | 264篇 |
2006年 | 229篇 |
2005年 | 177篇 |
2004年 | 158篇 |
2003年 | 153篇 |
2002年 | 154篇 |
2001年 | 132篇 |
2000年 | 108篇 |
1999年 | 120篇 |
1998年 | 192篇 |
1997年 | 128篇 |
1996年 | 93篇 |
1995年 | 78篇 |
1994年 | 71篇 |
1993年 | 50篇 |
1992年 | 55篇 |
1991年 | 37篇 |
1990年 | 24篇 |
1989年 | 32篇 |
1988年 | 18篇 |
1987年 | 21篇 |
1986年 | 12篇 |
1985年 | 9篇 |
1984年 | 15篇 |
1983年 | 18篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 9篇 |
1976年 | 11篇 |
1970年 | 4篇 |
排序方式: 共有6547条查询结果,搜索用时 15 毫秒
41.
爆破飞石的外弹道研究 总被引:1,自引:0,他引:1
本文利用现代外弹道数学理论,考虑了飞石的反弹作用和空气阻力作用,建立了飞石飞掷的数学物理模型,由此推导出爆破飞石飞掷距离计算公式。 相似文献
42.
Ha J.H. Kim S.W. Seol Y.S. Park H.K. Choi S.H. 《Semiconductor Manufacturing, IEEE Transactions on》1996,9(2):289-291
The plug loading effect occurring during the etchback of tungsten was investigated in a magnetically enhanced reactive ion etcher using SF 6/Ar mixtures. It was found that while the plug loading effect is independent of varying SF6/Ar flow rate ratio and magnetic field intensity, it is reduced under the condition of high selectivity of tungsten relative to TiN which was achieved at high chamber pressure and low RF power. It is proposed that when TiN is used as a glue layer, the W etch rate enhancement in the plug is mainly controlled by a local loading effect. Under the optimized etchback conditions the plug loss was successfully controlled without the tungsten residue left on severe topology 相似文献
43.
Recent advances in control systems analysis and design have implied new uses for the Lyapunov equation of the form AX +XA T+Q =0. Implementation requirements for the incorporation of the use of Lyapunov equations in practical design, however, point out the need for a set of specialized numerical procedures. This special set of numerical procedures must efficiently solve large, sparse Lyapunov equations, solve sets of Lyapunov equations that differ only in the coefficient matrix Q , and provide good low rank estimates of the Lyapunov equation solution X in the case where low rank approximations are applicable. Discussions of the motivations for the solution of these problems and of candidate solution approaches are provided 相似文献
44.
速度密度 10m/s住宅 总被引:4,自引:2,他引:2
本文通过一次参加日本《新建筑》国际住宅竞赛的经历,就未来高密度城市环境中住宅的生存状态进行了探讨。并试图用以速度来定义密度的方式探索当私密性与公共交往之间出现不可调和的矛盾时一种新的解决之道。 相似文献
45.
46.
For a PC-mobile download system which is embedded with streaming download protocol, there are problems that the data cannot be transmitted correctly from the PC to the mobile, or the transmission is unacceptably slow. To solve these problems, we carry out a formal analysis for the protocol with some timing parameters and a given probability of message loss and unordered data using a probabilistic model checking tool PRISM. We introduce a technique to reduce the state space of the system modeling the protocol which is a network of probabilistic timed automata. The experimental results in PRISM give us a clear explanation to the problems, and are helpful in identifying the optimal parameter settings to meet industrial requirements. 相似文献
47.
空气中^131I的取样和测量方法的研究 总被引:5,自引:2,他引:3
本文介绍一种气态和气载~(131)I 取样器。着重介绍了一种指数分布源的效率刻度方法,讨论了与取样有关的一些问题。 相似文献
48.
To synthesize diamond films by microwave plasma enhanced chemical vapor deposition (MPECVD), the methane concentration (CH4/H2)plays a crucial role. It is well-known that there always exists a critical methane concentration (≤0.6%) only below which
a good quality diamond film can be obtained. In this study, however, the phenomena of diamond synthesis resulting from high
carbon concentration conditions were observed. The molten metals, e.g., Ag, Cu, were used as the deposition substrates on
which crystalline diamonds can be achieved from a methane content of CH4/H2≥6% or even from solid carbon sources. These results suggest that there may exist a low methane content boundary layer (<0.6%)
in the proximity of molten metal surface on which suitable species, CH, CH+, Hα and Hβ are composed for the diamond nucleation and growth similar to the condition as in the conventional low methane contents.
The molten metal inclines to dissolve other forms of carbonaceous materials other than diamond, and thus keeps a much higher
steady supply of carbon atoms that enhances the quality as well as the growth rate of the forming diamonds.
Received: 23 June 2001 / Accepted: 23 July 2001 相似文献
49.
50.
Several types of ink are used in web offset printing. However, heatset inks predominate in general commercial work. In these inks, the vehicle consists of resin dissolved in a solvent, and drying takes place mainly by evaporation. In heatset web offset printing, the printed web is passed through dryers, which raise the temperature of the web enough to cause evaporation of the solvent. leaving only the resin to bind the pigment into a film and to the paper.
Since the solvents used in the heatset inks vary in boiling range from approximately 232° C to 316° C, and the solvent selected depends on the printing conditions, it is necessary to determine the vapor pressure values of heatset inks versus web temperatures for drying calculations. The isoteniscope method is limited to only the vapor pressure measurement of liquids. It cannot be used for materials such as heatset inks. To overcome this difficulty, an apparatus was designed and con- structed by TEC Systems for directly measuring the vapor pressure versus temperature of heatset inks from approximately 21°C to 316°C. In this paper, TEC's apparatus, test procedure developed, and typical test results for pure solvents and heatset inks will be described. 相似文献
Since the solvents used in the heatset inks vary in boiling range from approximately 232° C to 316° C, and the solvent selected depends on the printing conditions, it is necessary to determine the vapor pressure values of heatset inks versus web temperatures for drying calculations. The isoteniscope method is limited to only the vapor pressure measurement of liquids. It cannot be used for materials such as heatset inks. To overcome this difficulty, an apparatus was designed and con- structed by TEC Systems for directly measuring the vapor pressure versus temperature of heatset inks from approximately 21°C to 316°C. In this paper, TEC's apparatus, test procedure developed, and typical test results for pure solvents and heatset inks will be described. 相似文献