全文获取类型
收费全文 | 13771篇 |
免费 | 1519篇 |
国内免费 | 939篇 |
专业分类
电工技术 | 340篇 |
技术理论 | 1篇 |
综合类 | 1174篇 |
化学工业 | 1472篇 |
金属工艺 | 274篇 |
机械仪表 | 552篇 |
建筑科学 | 6235篇 |
矿业工程 | 127篇 |
能源动力 | 398篇 |
轻工业 | 181篇 |
水利工程 | 310篇 |
石油天然气 | 313篇 |
武器工业 | 21篇 |
无线电 | 463篇 |
一般工业技术 | 2415篇 |
冶金工业 | 190篇 |
原子能技术 | 82篇 |
自动化技术 | 1681篇 |
出版年
2024年 | 27篇 |
2023年 | 163篇 |
2022年 | 297篇 |
2021年 | 397篇 |
2020年 | 421篇 |
2019年 | 328篇 |
2018年 | 279篇 |
2017年 | 323篇 |
2016年 | 432篇 |
2015年 | 447篇 |
2014年 | 796篇 |
2013年 | 1064篇 |
2012年 | 1605篇 |
2011年 | 1566篇 |
2010年 | 1375篇 |
2009年 | 1413篇 |
2008年 | 786篇 |
2007年 | 1341篇 |
2006年 | 1231篇 |
2005年 | 555篇 |
2004年 | 205篇 |
2003年 | 177篇 |
2002年 | 187篇 |
2001年 | 113篇 |
2000年 | 138篇 |
1999年 | 109篇 |
1998年 | 61篇 |
1997年 | 41篇 |
1996年 | 48篇 |
1995年 | 33篇 |
1994年 | 22篇 |
1993年 | 25篇 |
1992年 | 9篇 |
1991年 | 14篇 |
1990年 | 15篇 |
1989年 | 8篇 |
1988年 | 24篇 |
1987年 | 54篇 |
1986年 | 56篇 |
1985年 | 11篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 12篇 |
1979年 | 18篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
静态EPS及其在建筑工程中的应用 总被引:2,自引:0,他引:2
一级负荷中特别重要的负荷,除由两个电源供电外,尚应增设应急电源。在供电条件比较差的地区,取得第二个电源供给一级负荷有困难时,也需要增设应急备用电源。以往经常用自备柴油发电机组、蓄电池、干电池和镍锦电池应急灯作为应急备用电源。本文通过对目前常用的各种应急电源的分析比较,推荐一种新颖的、静态、无公害、免维护无人值守的、供电质量好、安全可靠的集中供电式EPS装置。 相似文献
22.
23.
《Optical Materials》2005,27(1):99-102
The spin Hamiltonian parameters g∥, g⊥, A∥ and A⊥ for Er3+ ion in LiYF4 are investigated by using the perturbation formulas of these parameters for a 4f11 ion in tetragonal symmetry. In these formulas, the contributions to the spin Hamiltonian parameters from the second-order perturbation terms and the admixtures of different states are considered. The relevant crystal field parameters are calculated from the superposition model and the local structural parameters of the Y3+ site occupied by impurity Er3+. The theoretical optical spectra within 4I15/2 and 4I13/2 states and the spin Hamiltonian parameters obtained in this work are consistent with the observed values. 相似文献
24.
The iterative finite element model, in which an element is used to represent a single particle, is generated to analyze the
global behavior of multiple-material aggregates of materially nonlinear viscoplastic particles. The generalized Maxwell model
is used to define four types of specific nonlinear viscoplastic materials, which are the elasto visco-plastic matter with
linear viscosity, the plasto visco-plastic material with linear viscosity, the elasto visco-plastic media with nonlinear viscosity,
and the plasto visco-plastic media with nonlinear viscosity. The theory and relevant penalty iterative algorithm are developed
to analyze the four representative mixed granular systems consisting of materially nonlinear viscous particles. To verify
precision of stress calculation, solutions of an axis-symmetric radial flow problem are compared with results of the literature
and they are in a great agreement. The results present here provide significant insight into the fundamental behavior of granular
media under compaction conditions, including prediction of the overall aggregates stress-strain response. 相似文献
25.
《Hydrometallurgy》2006,81(3-4):190-196
A ligand-containing porous membrane was prepared by radiation-induced graft polymerization of an epoxy-group-containing monomer of glycidyl methacrylate onto a polyethylene porous hollow-fiber membrane and by subsequent conversion of the epoxy group to an N-methylglucamino (NMG) group at a density of 0.78 mmol/g of the membrane. Sb(V) solution was permeated through the NMG-ligand-containing porous hollow-fiber membrane. Optimum pH for Sb(V) recovery was 3.0. Breakthrough curves of Sb (V) overlapped irrespective of residence times of Sb (V) in the membrane, due to negligible diffusional mass-transfer resistance. Maximum amount of Sb (V) adsorbed was 130 mg/g-membrane, which was equivalent to 1.3 binding molar ratio. Repeated usage of the membrane for adsorption and elution was possible. 相似文献
26.
在前新生代油气资源选区评价中,前志留面之下未变质沉积地层(简称前志留基础层)的分布具有重要的参考价值。从提高纵向分辨率的处理和反演技术的应用入手,结合约束条件,利用大地电磁测深数据反演,揭示前志留面等界面的埋深和分布;同时应用小波分析技术,从磁场中分解出区域磁异常,反演结晶基底的埋深。通过这2个界面埋深的差异来分析前志留基础层的分布 相似文献
27.
首先以 HERMLE C1200 U 为例分析了五轴铣削加工中心的基本结构,然后据此给出了涉及多轴铣削加工中心后置处理角度分配和坐标变换的数学模型,最后介绍了以此数学模型为核心,为UG 软件开发的后置处理软件 UG-HERP1.0的解决方案。 相似文献
28.
Elastic solutions of a cylindrical rod containing periodically distributed inclusions with axisymmetric eigenstrains 总被引:1,自引:0,他引:1
Summary. In this paper, we give the elastic solution for a special type of microstructure – a circular cylindrical rod containing periodically distributed inclusions along its axial direction. Each inclusion has the same uniform axisymmetric transformation strain (eigenstrain). Analytical elastic solutions are obtained for the displacements, stresses and elastic strain energy of the rod. The effects of microstructure and its evolution (growth of inclusions) on the elastic stress and strain fields as well as the strain energy of the rod are quantitatively demonstrated. As a result of such microstructure evolution nominal stress-strain relation with strain softening is derived for a rod under uniaxial tension. 相似文献
29.
叠前地震数据的规则化 总被引:6,自引:1,他引:5
本文通过对动校正前积分法DMO原理的探讨,在借鉴Canning(1996)提出的利用DMO实现三维数据规则化的方法和Biondi(1998)提出的三维叠前地震数据方位角校正方法的基础上,从方位角校正的角度入手,利用DMO和DMO^-1相结合的处理流程对地震数据进行规则化,以得到新的规则的观测系统下具有所需特定方位角的观测数据。此方法可用于解决叠前地震数据道插值、陆上地震勘探中不规则观测数据的规则化和海上地震勘探中的羽状现象校正等问题,可将已有地震观测数据转变为特定观测系统的叠前地震数据,以便于某些处理方法的应用。此方法原理简单并具有广泛的适用性。 相似文献
30.
Prediction of cracking within early-age concrete due to thermal, drying and creep behavior 总被引:2,自引:0,他引:2
To predict potential early-age cracking after concrete placing, a numerical simulation procedure has been completed based on a micromechanical model and empirical formulas on the property development of young concrete. The numerical model could account for the effects of hydration, moisture transport and creep. Environmental influences, such as removal of formworks, curing conditions and variations of surrounding temperature and relative humidity, have been investigated. In calculating stress field with age caused by these synthetic physical-mechanical processes, three-dimensional finite element and finite difference (3D-FE-FD) methods are combined together. 相似文献