全文获取类型
收费全文 | 32350篇 |
免费 | 4364篇 |
国内免费 | 2481篇 |
学科分类
工业技术 | 39195篇 |
出版年
2024年 | 155篇 |
2023年 | 530篇 |
2022年 | 1007篇 |
2021年 | 1191篇 |
2020年 | 1276篇 |
2019年 | 1089篇 |
2018年 | 1017篇 |
2017年 | 1313篇 |
2016年 | 1342篇 |
2015年 | 1512篇 |
2014年 | 2086篇 |
2013年 | 2073篇 |
2012年 | 2617篇 |
2011年 | 2824篇 |
2010年 | 1982篇 |
2009年 | 1961篇 |
2008年 | 1895篇 |
2007年 | 2224篇 |
2006年 | 1916篇 |
2005年 | 1601篇 |
2004年 | 1315篇 |
2003年 | 1129篇 |
2002年 | 957篇 |
2001年 | 762篇 |
2000年 | 575篇 |
1999年 | 501篇 |
1998年 | 376篇 |
1997年 | 350篇 |
1996年 | 316篇 |
1995年 | 261篇 |
1994年 | 241篇 |
1993年 | 172篇 |
1992年 | 140篇 |
1991年 | 110篇 |
1990年 | 83篇 |
1989年 | 90篇 |
1988年 | 61篇 |
1987年 | 26篇 |
1986年 | 18篇 |
1985年 | 17篇 |
1984年 | 11篇 |
1983年 | 5篇 |
1982年 | 9篇 |
1981年 | 4篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1961年 | 3篇 |
1959年 | 13篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
A. Benhamida I. Djeran-Maigre H. Dumontet S. Smaoui 《International Journal of Rock Mechanics and Mining Sciences》2005,42(7-8):996-1005
The modelling of hydromechanical behavior of clayey sediments by homogenization theory is described. The rheological model of clays buried in depth requires a three-dimensional approach and laboratory experiments to quantify the model parameters. An iterative process which can be coupled to any homogenization method is used to model the porous media behavior. Hydromechanical compaction results from oedometric experiments are simulated with the proposed model. 相似文献
72.
73.
使用液力偶合器因故障频繁,对高炉稳产、高产造成严重威胁,而且维修费用较高,对偶合器改造后,应用金属迭片挠性联轴器其故障率、维修费用都很低。 相似文献
74.
介绍了研制出其性能达国际先进公司同类产品水平的塑封双列直插式光耦合器的工作原理和提高绝缘耐压的技术难点,从引线框架设计、加工精度控制、内包封材料选型、理想内包封形状控制、塑封气密性的实现、环境条件的完善等方面讨论了提高绝缘耐压的设计和工艺要点。 相似文献
75.
CHENSheng-ping LUKe-cheng LIYi-gang LIJia-fang ZHUJian-ping FENGMing LIJing 《半导体光子学与技术》2004,10(2):122-126
The effects of the variations in fiber length, fiber mirror reflectance on efficiency and output power are experimentally investigated for erbium-doped double pass backward superfluorescent fiber sources (SFSs). The influence of fiber length on mean wavelength stability (MWS) has also been demonstrated. By incorporating a short section of un-pumped erbium-doped fiber (EDF) at the output port, the pump power dependent on MWS becomes independent of pumped EDF length. This is a novel phenomenon that hasn‘t been reported up to now,and should be helpful to SFS fabrication and theory analysis. By using a fiber Michelson interferometer as spectrum slicing component,a multi-wavelength fiber source (MWFS) with ~20 channels (from 1542nm to 1559nm) is got. The MWFS has a channel spacing of ~0. 8 nm which satisfies ITUstandard. The intensity fluctuation among channels is less than 0.5dB,and the extinction ratio of all channels is above 14dB. This kind of MWFS should be useful to wavelength division multiplexing systems. 相似文献
76.
Dong Sun Author Vitae 《Automatica》2003,39(6):997-1005
A new control approach to position synchronization of multiple motion axes is developed, by incorporating cross-coupling technology into adaptive control architecture. The control strategy is to stabilize position tracking of each axis while synchronizing its motion with other axes’ motions so that differential position errors amongst axes converge to zero. The proposed adaptive controller and parameter estimator employ coupling control by feeding back position errors and differential position errors, and have been realized to guarantee asymptotic convergence to zero of both position and synchronization errors. Simulations conducted on a multi-axis motion control system demonstrate the effectiveness of the method. 相似文献
77.
Compared to other fields of engineering, in mechanical engineering, the Discrete Element Method (DEM) is not yet a well known
method. Nevertheless, there is a variety of simulation problems where the method has obvious advantages due to its meshless
nature. For problems where several free bodies can collide and break after having been largely deformed, the DEM is the method
of choice. Neighborhood search and collision detection between bodies as well as the separation of large solids into smaller
particles are naturally incorporated in the method. The main DEM algorithm consists of a relatively simple loop that basically
contains the three substeps contact detection, force computation and integration. However, there exists a large variety of
different algorithms to choose the substeps to compose the optimal method for a given problem. In this contribution, we describe
the dynamics of particle systems together with appropriate numerical integration schemes and give an overview over different
types of particle interactions that can be composed to adapt the method to fit to a given simulation problem. Surface triangulations
are used to model complicated, non-convex bodies in contact with particle systems. The capabilities of the method are finally
demonstrated by means of application examples.
Commemorative Contribution. 相似文献
78.
官泓 《有色冶金设计与研究》2003,24(3):49-51
阐述水厂设计中对水厂规模、水源地、净水厂位置及净水工艺的确定过程,根据原水的特点,通过分析对无阀滤池进行改良。 相似文献
79.
岩体渗透率与应力关系是进行岩体渗流应力耦合分析的基础。基于龙滩水电站边坡岩体渗流压水试验结果和边坡岩体岩性及物理力学性质,对岩体渗透系数和地应力进行了分析计算,给出了边坡岩体渗透率随应力变化的关系式,为进行边坡岩体渗流一应力耦合分析提供了可靠数据。 相似文献
80.
研究了热传导方程的通解,进而提出激光热源形成的微观机理和热源形成过程的三个理论计算式。对激光热效应的应用具有指导意义。 相似文献