全文获取类型
收费全文 | 19497篇 |
免费 | 1810篇 |
国内免费 | 1262篇 |
专业分类
电工技术 | 726篇 |
综合类 | 2829篇 |
化学工业 | 4286篇 |
金属工艺 | 2146篇 |
机械仪表 | 815篇 |
建筑科学 | 1227篇 |
矿业工程 | 596篇 |
能源动力 | 676篇 |
轻工业 | 917篇 |
水利工程 | 383篇 |
石油天然气 | 852篇 |
武器工业 | 113篇 |
无线电 | 1003篇 |
一般工业技术 | 2744篇 |
冶金工业 | 1287篇 |
原子能技术 | 229篇 |
自动化技术 | 1740篇 |
出版年
2024年 | 57篇 |
2023年 | 223篇 |
2022年 | 365篇 |
2021年 | 529篇 |
2020年 | 565篇 |
2019年 | 522篇 |
2018年 | 454篇 |
2017年 | 597篇 |
2016年 | 649篇 |
2015年 | 673篇 |
2014年 | 1042篇 |
2013年 | 1202篇 |
2012年 | 1409篇 |
2011年 | 1438篇 |
2010年 | 1037篇 |
2009年 | 1126篇 |
2008年 | 1031篇 |
2007年 | 1226篇 |
2006年 | 1194篇 |
2005年 | 1055篇 |
2004年 | 913篇 |
2003年 | 823篇 |
2002年 | 686篇 |
2001年 | 547篇 |
2000年 | 491篇 |
1999年 | 430篇 |
1998年 | 324篇 |
1997年 | 309篇 |
1996年 | 273篇 |
1995年 | 252篇 |
1994年 | 248篇 |
1993年 | 168篇 |
1992年 | 151篇 |
1991年 | 136篇 |
1990年 | 110篇 |
1989年 | 86篇 |
1988年 | 66篇 |
1987年 | 39篇 |
1986年 | 19篇 |
1985年 | 19篇 |
1984年 | 20篇 |
1983年 | 14篇 |
1982年 | 20篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 9篇 |
1976年 | 2篇 |
1960年 | 1篇 |
1959年 | 2篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
We have investigated the dynamic behavior of a nonionic micellar solution of tetra-ethylene glycoln-decylether (C10 E4) in water near its critical point in the presence of shear. The non-Newtonian behavior of the viscosity can be represented by * = [ 1 +a(S4)=]2, where* is the viscosity in the absence of shear,S is the shear rate. 4 is the lifetime of the critical Iluctuations,a is a system-dependent constant, and = 0.02 In addition, we have found that, before attaining a steady state, the sheared mixture undergoing phase separation shows significant shear-dependent rheological effects due to the presence of concentration domains.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24. 1994, Boulder, Colorado, U.S.A. 相似文献
82.
Designing Metallic and Insulating Nanocrystal Heterostructures to Fabricate Highly Sensitive and Solution Processed Strain Gauges for Wearable Sensors 下载免费PDF全文
Woo Seok Lee Seung‐Wook Lee Hyungmok Joh Mingi Seong Haneun Kim Min Su Kang Ki‐Hyun Cho Yun‐Mo Sung Soong Ju Oh 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(47)
All‐solution processed, high‐performance wearable strain sensors are demonstrated using heterostructure nanocrystal (NC) solids. By incorporating insulating artificial atoms of CdSe quantum dot NCs into metallic artificial atoms of Au NC thin film matrix, metal–insulator heterostructures are designed. This hybrid structure results in a shift close to the percolation threshold, modifying the charge transport mechanism and enhancing sensitivity in accordance with the site percolation theory. The number of electrical pathways is also manipulated by creating nanocracks to further increase its sensitivity, inspired from the bond percolation theory. The combination of the two strategies achieves gauge factor up to 5045, the highest sensitivity recorded among NC‐based strain gauges. These strain sensors show high reliability, durability, frequency stability, and negligible hysteresis. The fundamental charge transport behavior of these NC solids is investigated and the combined site and bond percolation theory is developed to illuminate the origin of their enhanced sensitivity. Finally, all NC‐based and solution‐processed strain gauge sensor arrays are fabricated, which effectively measure the motion of each finger joint, the pulse of heart rate, and the movement of vocal cords of human. This work provides a pathway for designing low‐cost and high‐performance electronic skin or wearable devices. 相似文献
83.
在满足机构许用压力角条件下,采用0.618法最优确定盘状摆动凸轮机械的最小基圆半径。 相似文献
84.
文章基于验证和解决信息设备内存储器存在的信息安全泄漏隐患,提出了内存储器信息泄漏概念并对内存储器存在信息泄漏的原因做了介绍。实测发现现有内存储器存在信息泄漏状况,基于此,该文提出了基于公共信息网和文件型恶意代码窃取的内存储器信息泄漏方式并完成了实测过程,文章结论对于信息安全保密领域的内存储器信息泄漏隐患防护具有重要意义,尤其适用于安全隔离和信息交换等信息系统领域,具有较广泛的应用前景和重大的社会意义。 相似文献
85.
宋杰鹏 《数字社区&智能家居》2011,(19)
遗传算法是一种有效的解决最优化问题的方法,在解决复杂的全局优化问题方面,遗传算法已得到了成功的应用。对遗传算法的基本步骤进行总结,通过最优化问题求解实例描述了遗传算法的具体运行过程,包括产生初始染色体、染色体评价、选择、交叉、变异等。分别应用VC和VB两种语言进行编程实现,结果表明,VC语言在运算效率和结果优度方面均比VB语言要好。 相似文献
86.
Jung Hyeon Bae Gun Hee Kim Woong Hee Jeong Hyun Jae Kim 《Journal of the Society for Information Display》2011,19(5):404-409
Abstract— Non‐volatile memory effects of an all‐solution‐processed oxide thin‐film transistor (TFT) with ZnO nanoparticles (NPs) as the charge‐trapping layer are reported. The device was fabricated by using a soluble MgInZnO active channel on a ZrHfOx gate dielectric. ZnO NPs were used as the charge‐trapping site at the gate‐insulator—channel interface, and Al was used for source and drain electrodes. Transfer characteristics of the device showed a large clockwise hysteresis, which can be used to demonstrate its memory function due to electron trapping in the ZnO NP charge‐trapping layer. This memory effect has the potential to be utilized as a memory application on displays and disposable electronics. 相似文献
87.
We present a second-order analytic solution to the nonlinear depth-integrated shallow water equations for free-surface oscillatory wind-driven flow in an idealized lake. Expressing the solution as an asymptotic expansion in the dimensionless wave amplitude (ζ/h), which is considered to be a small parameter, enables simplification of the governing equations and permits the use of a perturbation approach to solve them.This analytic solution provides a benchmark for testing numerical models. In particular, the main merit of this solution is that it accounts for advective effects, which are typically omitted from analytic solutions of two-dimensional free surface flow. In order to retain these effects in an analytic solution, we restrict our attention to forcing from a monochromatic wind stress, consider a constant depth rectangular lake, and simplify the governing equations by omitting the Coriolis and eddy viscosity terms and using a linearised friction factor. As such, the analytic solution is of limited use for considering real world problems. Due to the complexity of the analytic solution computer code for this solution is available online.Our solution is valid for cases where changes in the water surface level are small compared with the depth of the lake, and the advective terms in the momentum equations are small compared with acceleration terms. We examine the validity of these assumptions for three test cases, and compare the second-order analytic solution to numerical results to verify an existing hydrodynamic model. 相似文献
88.
数独基于规则的逐步枚举算法设计 总被引:1,自引:0,他引:1
给出了数独(Sudoku)的6条性质,并在此基础上提出了6条推理规则,然后结合空格填写的一个一组,两个一组及更多个一组的枚举算法,在枚举中进行推理.使推理和枚举结合起来,对有唯一解的数独问题,其求解速度比回溯法快得多,同时也能完成许多数独软件无法进行推理计算的数独难题.用两个数独难题进行验证,表明该方法十分有效. 相似文献
89.
提出了一种基于非线性参数估计的水下定位系统传感器安装误差标定技术.水下定位系统由声学传感器,GPS和船体姿态传感器组成,各传感器的坐标系并不能完全重合,需要对传感器之间的误差标定后进行修正才能够获得高精度的定位效果.已有的标定方法多基于高斯-牛顿迭代法,而当非线性系统模型线性化带来较大误差时,常规的基于高斯-牛顿迭代法的标定方法已无法达到高精度的要求,而非线性模型参数估的直接解法则掺人了三阶量,有效减小线性化的模型误差,提高了各传感器安装误差的标定精度.海试数据处理表明:定位精度可由1 m提高到0.7 m. 相似文献
90.
Mathematical model of vertical electrical sounding by using resistivity method is studied. The model leads to an inverse problem of determination of the unknown leading coefficient (conductivity) of the elliptic equation in R2 in a slab. The direct problem is obtained in the form of mixed BVP in axisymmetric cylindrical coordinates. The additional (available measured) data is given on the upper boundary of the slab, in the form of tangential derivative. Due to ill-conditionedness of the considered inverse problem the logarithmic transformation is applied to the unknown coefficient and the inverse problem is studied as a minimization problem for the cost functional, with respect to the reflection coefficient. The Conjugate Gradient method (CGM) is applied for the numerical solution of this problem. Computational experiments were performed with noise free and random noisy data. 相似文献