全文获取类型
收费全文 | 239491篇 |
免费 | 6563篇 |
国内免费 | 2640篇 |
专业分类
电工技术 | 5785篇 |
技术理论 | 3篇 |
综合类 | 3222篇 |
化学工业 | 34546篇 |
金属工艺 | 10174篇 |
机械仪表 | 8808篇 |
建筑科学 | 8183篇 |
矿业工程 | 2489篇 |
能源动力 | 6449篇 |
轻工业 | 19116篇 |
水利工程 | 3047篇 |
石油天然气 | 7046篇 |
武器工业 | 351篇 |
无线电 | 28017篇 |
一般工业技术 | 44864篇 |
冶金工业 | 39124篇 |
原子能技术 | 5630篇 |
自动化技术 | 21840篇 |
出版年
2022年 | 1606篇 |
2021年 | 3067篇 |
2020年 | 2390篇 |
2019年 | 2654篇 |
2018年 | 3760篇 |
2017年 | 4016篇 |
2016年 | 4015篇 |
2015年 | 3345篇 |
2014年 | 5113篇 |
2013年 | 11369篇 |
2012年 | 7564篇 |
2011年 | 9822篇 |
2010年 | 8028篇 |
2009年 | 8672篇 |
2008年 | 8802篇 |
2007年 | 8744篇 |
2006年 | 7954篇 |
2005年 | 7200篇 |
2004年 | 6421篇 |
2003年 | 6469篇 |
2002年 | 6186篇 |
2001年 | 6058篇 |
2000年 | 5543篇 |
1999年 | 5817篇 |
1998年 | 12104篇 |
1997年 | 8763篇 |
1996年 | 6988篇 |
1995年 | 5299篇 |
1994年 | 4806篇 |
1993年 | 4480篇 |
1992年 | 3478篇 |
1991年 | 3259篇 |
1990年 | 3002篇 |
1989年 | 3061篇 |
1988年 | 2941篇 |
1987年 | 2453篇 |
1986年 | 2331篇 |
1985年 | 2717篇 |
1984年 | 2487篇 |
1983年 | 2320篇 |
1982年 | 2070篇 |
1981年 | 2189篇 |
1980年 | 2013篇 |
1979年 | 2104篇 |
1978年 | 2095篇 |
1977年 | 2343篇 |
1976年 | 3163篇 |
1975年 | 1814篇 |
1974年 | 1736篇 |
1973年 | 1756篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
2.
Chhipa Mayur Kumar Madhav B. T. P. Suthar Bhuvneshwer Janyani Vijay 《Photonic Network Communications》2022,44(1):30-40
Photonic Network Communications - In the present work, a high-speed optical encoder is proposed based on two-dimensional photonic crystal ring resonator using coupled mode theory and resonance... 相似文献
3.
Sánchez-Vásquez J. D. Portillo-Rodríguez B. Tovar-Martínez E. Reyes-Reyes M. López-Sandoval R. 《Journal of Materials Science: Materials in Electronics》2022,33(18):14910-14926
Journal of Materials Science: Materials in Electronics - Non-volatile organic memory devices were fabricated using polystyrene sulfonate (PSS)?+?nitrogen-doped multi-walled carbon... 相似文献
5.
The present article investigates the influence of Joule heating and chemical reaction on magneto Casson nanofluid phenomena in the occurrence of thermal radiation through a porous inclined stretching sheet. Consideration is extended to heat absorption/generation and viscous dissipation. The governing partial differential equations were transformed into nonlinear ordinary differential equations and numerically solved using the Implicit Finite Difference technique. The article analyses the effect of various physical flow parameters on velocity, heat, and mass transfer distributions. For the various involved parameters, the graphical and numerical outcomes are established. The analysis reveals that the enhancement of the radiation parameter increases the temperature and the chemical reaction parameter decreases the concentration profile. The empirical data presented were compared with previously published findings. 相似文献
6.
We considered the magnetohydrodynamic (MHD) free convective flow of an incompressible electrically conducting viscous fluid past an infinite vertical permeable porous plate with a uniform transverse magnetic field, heat source and chemical reaction in a rotating frame taking Hall current effects into account. The momentum equations for the fluid flow during absorbent medium are controlled by the Brinkman model. Through the undisturbed state, both the plate and fluid are in a rigid body rotation by the uniform angular velocity perpendicular to an infinite vertical plate. The perpendicular surface is subject to the homogeneous invariable suction at a right angle to it and the heat on the surface varies about a non-zero unvarying average whereas the warmth of complimentary flow is invariable. The systematic solutions of the velocity, temperature, and concentration distributions are acquired systematically by utilizing the perturbation method. The velocity expressions consist of steady-state and fluctuating situations. It is revealed that the steady part of the velocity field has a three-layer characteristic while the oscillatory part of the fluid field exhibits a multi-layer characteristic. The influence of various governing flow parameters on the velocity, temperature, and concentration are analyzed graphically. We also discuss computational results for the skin friction, Nusselt number, and Sherwood number in the tabular forms. 相似文献
7.
Journal of Porous Materials - In this work, a trifluoromethanesulfonic acid (TFOH) modified clay (TFOH-Clay) was developed for the removal of trace olefins in heavy naphtha. 5%TFOH-Clay can... 相似文献
8.
Journal of Materials Science - For decades, a wide variety of products have benefitted from the use of flexible PVC, ranging from healthcare to cable to packaging & household items. The... 相似文献
9.
The thermodynamics modeling of a Reiner–Philippoff-type fluid is essential because it is a complex fluid with three distinct probable modifications. This fluid model can be modified to describe a shear-thinning, Newtonian, or shear-thickening fluid under varied viscoelastic conditions. This study constructs a mathematical model that describes a boundary layer flow of a Reiner–Philippoff fluid with nonlinear radiative heat flux and temperature- and concentration-induced buoyancy force. The dynamical model follows the usual conservation laws and is reduced through a nonsimilar group of transformations. The resulting equations are solved using a spectral-based local linearization method, and the accuracy of the numerical results is validated through the grid dependence and convergence tests. Detailed analyses of the effects of specific thermophysical parameters are presented through tables and graphs. The study reveals, among other results, that the buoyancy force, solute and thermal expansion coefficients, and thermal radiation increase the overall wall drag, heat, and mass fluxes. Furthermore, the study shows that amplifying the space and temperature-dependent heat source parameters allows fluid particles to lose their cohesive force and, consequently, maximize flow and heat transfer. 相似文献
10.
Lu Huaiqian Shi Hui Xie Qilong Li Li Xiao Yong Jia Litao Li Debao 《Catalysis Letters》2022,152(11):3347-3353
Catalysis Letters - This study proposed a new facile route to rational creating oxygen-vacancy (Vo)-rich surface of Co3O4 nanosheets by acetic acid leaching. The acid leached Co3O4 nanosheets was... 相似文献