全文获取类型
收费全文 | 2295篇 |
免费 | 202篇 |
国内免费 | 96篇 |
专业分类
电工技术 | 136篇 |
综合类 | 291篇 |
化学工业 | 322篇 |
金属工艺 | 51篇 |
机械仪表 | 117篇 |
建筑科学 | 295篇 |
矿业工程 | 55篇 |
能源动力 | 104篇 |
轻工业 | 195篇 |
水利工程 | 65篇 |
石油天然气 | 76篇 |
武器工业 | 12篇 |
无线电 | 50篇 |
一般工业技术 | 682篇 |
冶金工业 | 25篇 |
原子能技术 | 8篇 |
自动化技术 | 109篇 |
出版年
2024年 | 6篇 |
2023年 | 21篇 |
2022年 | 37篇 |
2021年 | 50篇 |
2020年 | 47篇 |
2019年 | 53篇 |
2018年 | 55篇 |
2017年 | 93篇 |
2016年 | 90篇 |
2015年 | 82篇 |
2014年 | 99篇 |
2013年 | 135篇 |
2012年 | 120篇 |
2011年 | 124篇 |
2010年 | 85篇 |
2009年 | 127篇 |
2008年 | 146篇 |
2007年 | 141篇 |
2006年 | 146篇 |
2005年 | 137篇 |
2004年 | 116篇 |
2003年 | 100篇 |
2002年 | 83篇 |
2001年 | 69篇 |
2000年 | 75篇 |
1999年 | 65篇 |
1998年 | 37篇 |
1997年 | 48篇 |
1996年 | 44篇 |
1995年 | 21篇 |
1994年 | 24篇 |
1993年 | 18篇 |
1992年 | 18篇 |
1991年 | 13篇 |
1990年 | 20篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 10篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1980年 | 1篇 |
排序方式: 共有2593条查询结果,搜索用时 15 毫秒
41.
对芦荟纤维与粘胶纤维的拉伸性质、摩擦和抱合性质、卷曲弹性、耐热性和热稳定性进行了测试与分析。结果表明:芦荟纤维的断裂强度比粘胶高,芦荟纤维的断裂伸长率比粘胶低;芦荟纤维粘胶的静摩擦因数小于粘胶纤维的静摩擦因数;粘胶纤维间的抱合力比芦荟纤维间的抱合力大,但芦荟纤维的平滑性比粘胶纤维要好。粘胶纤维的卷曲数、卷曲率、卷曲弹性回复率和残留卷曲率均小于芦荟纤维。 相似文献
42.
大位移非线性弹性理论的广义变分原理 总被引:6,自引:0,他引:6
何吉欢 《中国矿业大学学报》1999,28(2):136-138,148
应用半反推法(凑合反推法)推导了大位移非线性弹性理论中的二类及三类独立变量的广义变分原理,由于半反推法不用拉氏乘子,所以可以避免由于拉氏乘子引起的临界变分现象,结果证明Hu-Washizu为分原理只是二类独立变量的变发原理。 相似文献
43.
Amir Reza Ghanei Mohammadi 《先进材料力学与结构力学》2017,24(6):469-481
In this article, an analytical study of elastic P- and SV-wave scattering by a circular nanofiber is presented. The nanofiber is assumed to be surrounded by an inhomogeneous interphase layer, and Gurtin–Murdoch's model of surface elasticity is utilized to study the surface/interface effects in the regions between the fiber and interphase and also interphase and matrix. The simultaneous effects of surface elasticity and interphase inhomogeneity are considered here; by taking the inhomogeneous interphase to be composed of several sublayers, a transfer matrix approach is used to find the unknown field variables and, consequently, the scattering cross sections. The results indicate that considering the effects of surface elasticity and interphase inhomogeneity has a considerable impact on the calculated scattering cross sections. 相似文献
44.
Yoshiro Suzuki 《International journal for numerical methods in engineering》2014,98(10):703-720
A new finite heterogeneous element consisting of sliced microstructures (FHES) is applied in a multi?scale technique. The FHES represents a heterogeneous material with microscopic constituents without homogenization or microscopic finite element analysis. A representative volume element extracted from a heterogeneous structure is thinly sliced. Each slice is modeled as a combined spring to calculate properties of the FHES. Each FHES has the same number of nodes as an ordinary finite element, and the macroscopic analysis cost is the same as that for ordinary finite element analysis. However, the FHES retains information about the microscopic material layout (i.e., the distribution of a material's property) in itself that is lost during homogenization. In the proposed approach, materials are not homogenized. The FHES does not have a constant (homogenized) material property and can ‘change stiffness’ depending on its deformation behavior. This reduces error due to coarse?graining and allows us to calculate the macroscopic deformation behavior with sufficient accuracy even if a large gradient of strain is generated in the macroscopic field. The novelty of the research is the development of rational heterogeneous finite elements. The paper presents the theory behind the FHES and its practical application to a linear elastic problem. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
45.
爆振对衬砌损伤特性影响的室内试验研究 总被引:2,自引:1,他引:2
本文根据一隧洞施工现场的实测爆振波特性,就爆振波对隧洞衬砌的浇筑时间、衬砌混凝土受振后的强度降低问题进行了室内爆振模拟试验,并应用损伤力学理论对试验结果作出了合理解释;对工程上所关心的安全爆速、衬砌的安全距离及合理衬砌时间等重要参数都给出了明确解答。 相似文献
46.
余弦分布压力下矩形薄板的屈曲 总被引:1,自引:0,他引:1
针对不同支承条件,两对边受半余弦非线性分布压力下弹性矩形薄板的屈曲问题,进行了分析研究。对于只产生对称变形的矩形薄板,基于辛弹性力学的平面矩形域理论,给出了精确的面内应力分布。运用Galerkin法分析计算了半余弦分布压力下矩形薄板的屈曲载荷。根据各种不同支承矩形薄板弯曲的位移边界条件,借助于符号运算软件Maple,编写了相应的用户计算程序。对九种不同支承组合下的弹性矩形薄板进行了计算,得到了不同长宽比矩形薄板的屈曲载荷系数。通过与已有文献结果的比较表明,该文求解方法是有效和精确的。基于所给出的结果,可望为解决矩形薄板在非线性分布载荷下的屈曲分析提供一种新的研究方法。 相似文献
47.
A structural experimental technique to characterize the viscoelastic behavior of concrete under restrained deformations 下载免费PDF全文
An innovative variable restraint frame is proposed to characterize the viscoelastic behavior of concrete under tensile stresses induced by restraints to shrinkage deformations (mainly due to drying). Two concrete specimens with the same cross section are used, subjected to equal thermal and moisture conditions: one is made of plain concrete, to assess the “free” deformations due to shrinkage and temperature; the other is reinforced with two steel threaded rods, which induce a manually controlled axial restraint to shrinkage. The restrained specimen is installed on a reaction frame, being stretched in force control mode. The concrete and the rods are instrumented with strain gauges and temperature sensors, which allow separation of the different components of concrete strains with the aid of equations based on equilibrium and compatibility conditions. This permits identifying the elastic and tensile creep concrete strains, as well as the concrete tensile stresses induced by the restrained shrinkage. The device also allows assessing the concrete modulus of elasticity during the test and remains operational even upon concrete cracking, features of great interest for the intended material characterization. 相似文献
48.
Aditya M. Vora 《Frontiers of Materials Science in China》2007,1(4):366-378
The vibrational dynamics of three Ca-based non-crystalline alloys viz. Ca70Mg30, Ca70Zn30 and Ca60Al40 have been studied at room temperature in terms of the phonon eigen frequencies of longitudinal and transverse modes, employing
three theoretical formulations given by Hubbard-Beeby (HB), Takeno-Goda (TG) and Bhatia-Singh (BS). Five local field correction
functions viz. Hartree (H), Taylor (T), Ichimaru-Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) are used for the first
time in the present investigation to study the screening influence on the aforesaid properties. The pseudo-alloy-atom (PAA)
model is applied for the first time instead of Vegard’s Law. Long wavelength limits of the phonon modes are used to investigate
the elastic and thermal properties of the system. The low temperature specific heat is also calculated from the elastic limit
of the phonon dispersion curves (PDCs). The present findings of the PDCs of Ca70Mg30 glass are found in fair agreement with available theoretical and experimental data. 相似文献
49.
50.
A framework for damage mechanics of concrete is applied to simulate the nonlinear elastic deformation behavior of concrete using finite element method (FEM). A rather simple isotropic damage model containing essentially no adjustable parameters is shown to produce results in remarkably good agreement with sample experimental data: the damage law requires only the fracture energy to be defined completely. The model is achieved by introducing a damage surface that is similar to the yield function in the conventional theory of plasticity. A special form of damage surfaces is constructed to illustrate the application of the model. A new damage criterion, defined as an equivalent strain norm, is proposed, in order to take into consideration the asymmetric behavior of concrete. For verifying the FEM program including the model, deformations predicted by this model are compared with both the experimental ones for the concrete structural model and the ones calculated without application of the continuum damage mechanics.__________Translated from Problemy Prochnosti, No. 3, pp. 57 – 74, May – June, 2005. 相似文献