全文获取类型
收费全文 | 101594篇 |
免费 | 8386篇 |
国内免费 | 5385篇 |
专业分类
电工技术 | 6042篇 |
技术理论 | 1篇 |
综合类 | 6552篇 |
化学工业 | 12190篇 |
金属工艺 | 4597篇 |
机械仪表 | 4778篇 |
建筑科学 | 5139篇 |
矿业工程 | 2620篇 |
能源动力 | 1822篇 |
轻工业 | 8852篇 |
水利工程 | 2698篇 |
石油天然气 | 2519篇 |
武器工业 | 852篇 |
无线电 | 8279篇 |
一般工业技术 | 8301篇 |
冶金工业 | 23865篇 |
原子能技术 | 1551篇 |
自动化技术 | 14707篇 |
出版年
2024年 | 392篇 |
2023年 | 1162篇 |
2022年 | 2469篇 |
2021年 | 3069篇 |
2020年 | 2201篇 |
2019年 | 1586篇 |
2018年 | 2038篇 |
2017年 | 2397篇 |
2016年 | 2611篇 |
2015年 | 3388篇 |
2014年 | 3643篇 |
2013年 | 4177篇 |
2012年 | 6840篇 |
2011年 | 7342篇 |
2010年 | 5484篇 |
2009年 | 5518篇 |
2008年 | 5334篇 |
2007年 | 5268篇 |
2006年 | 4531篇 |
2005年 | 6607篇 |
2004年 | 5042篇 |
2003年 | 3878篇 |
2002年 | 2820篇 |
2001年 | 2630篇 |
2000年 | 1483篇 |
1999年 | 1142篇 |
1998年 | 6296篇 |
1997年 | 3935篇 |
1996年 | 2605篇 |
1995年 | 1542篇 |
1994年 | 1133篇 |
1993年 | 1180篇 |
1992年 | 297篇 |
1991年 | 345篇 |
1990年 | 342篇 |
1989年 | 317篇 |
1988年 | 310篇 |
1987年 | 242篇 |
1986年 | 217篇 |
1985年 | 177篇 |
1984年 | 73篇 |
1983年 | 93篇 |
1982年 | 132篇 |
1981年 | 188篇 |
1980年 | 202篇 |
1979年 | 67篇 |
1978年 | 98篇 |
1977年 | 608篇 |
1976年 | 1319篇 |
1975年 | 98篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
贴片机脱机编程的快捷方法 总被引:7,自引:4,他引:3
SMT生产线中的大多数加工设备均为数控设备。它们编程所需要的大多数特征数据均可从CAD设计系统中得到。文章介绍了如何从CAD设计系统中导出X、Y坐标数据,并转换成贴片数据的方法和思路,以期引起更多的同行加入到这方面的研究中。 相似文献
32.
33.
Jean-Fran?ois Blais Nathalie Meunier Guy Mercier Patrick Drogui Rajeshwar Dayal Tyagi 《Canadian Metallurgical Quarterly》2004,130(5):516-525
This research is related to a preindustrial pilot scale study of the performance of the simultaneous sewage sludge digestion and metal leaching (SSDML) process for decontamination and stabilization of sewage sludge. Ten batch tests were carried out in two 4?m3 bioreactors under various conditions of operation. Results indicated that the addition of 1.0 to 1.5?g?S0/L, which is the equivalent of approximately 30 to 50?kg?S0 per tons dry sludge, is sufficient to obtain conditions of acidity (pH<2.5) and oxido-reduction potential greater than 500 mV necessary for an effective solubilization of toxic metals. The final average of metal solubilization in the output sludge during the SSDML process varied in the following ranges: 25–78% Cd, 9–32% Cr, 48–100% Cu, 77–99% Mn, 15–53% Ni, 12–47% Pb, and 66–100% Zn. The N, P, and K contents were also preserved in the decontaminated sludge. Moreover, the use of low concentrations of elemental sulfur makes it possible to obtain decontaminated sludge with a low total sulfur content (1.4–1.5% S) compatible with agricultural use. The suspended solids removal calculated for the SSDML process was slightly lower, (2.5±0.4)% volatile suspended solids per day, than those reached using standard aerobic digestion. Finally, the SSDML process was found to be effective in removing bad odors and in the destruction (99–100%) of indicator bacteria. 相似文献
34.
35.
Branislav Radjenovi? Jae Koo Lee Marija Radmilovi?-Radjenovi? 《Computer Physics Communications》2006,174(2):127-132
Level set method [S. Osher, J. Sethian, J. Comput. Phys. 79 (1988) 12] is a highly robust and accurate computational technique for tracking moving interfaces in various application domains. It originates from the idea to view the moving front as a particular level set of a higher dimensional function, so the topological merging and breaking, sharp gradients and cusps can form naturally, and the effects of curvature can be easily incorporated. The resulting equations, describing interface surface evolution, are of Hamilton-Jacobi type and they are solved using techniques developed for hyperbolic equations. In this paper we describe an extension of the sparse field method for solving level set equations in the case of non-convex Hamiltonians, which are common in the simulations of the profile surface evolution during plasma etching and deposition processes. Sparse field method itself, developed by Whitaker [R. Whitaker, Internat. J. Comput. Vision 29 (3) (1998) 203] and broadly used in image processing community, is an alternative to the usual combination of narrow band and fast marching procedures for the computationally effective solving of level set equations. The developed procedure is applied to the simulations of 3D feature profile surface evolution during plasma etching process, that include the effects of ion enhanced chemical etching and physical sputtering, which are the primary causes of the Hamiltonian non-convexity. 相似文献
36.
On the effect of spatial variances in historical rainfall time series to CSO performance evaluation.
Historical, high-resolution rain series are the backbone of modern combined sewer overflow (CSO) structure design. These rain series are the input to the computational estimation of the performance of the measures with respect to CSO pollution abatement. However, those historical precipitation measurements are available at only a few locations. Frequently rain series have to be used from gauging stations at a significant distance. In order to judge and to compensate for this influence an estimate between rain characteristics and combined sewer outflow (CSO) performance indicators would be useful. In this paper such correlations have been sought for a collection of 37 rain series covering large areas of Europe. It was found that the mean annual rain volume can explain most of the variances for the performance indicators Number of overflows and CSO volume. For explaining the spatial differences in the efficiency of the CSO structure another rain characteristic, i.e. the maximum event with a return period of one year, is to be used. 相似文献
37.
碳纳米管膜的场致发射电流密度仅由它表面的宏观电场决定,无论其表面形状是平的还是半球状的。对于理想的平行板电极系统,其表面电场强度均匀(UId),发射电流密度、总电流与发射面积成正比:对于半球一平面电极系统半球形的阴极存在一个宏观场增强因子ks,一个与两极距离和球半径之比(d/r)相关的函数,其表面的平均场强为ks U/d。对于d/r=0,ks=1,d≥r的情况,ks接近于常数。对于10〈d/r〈100的情况,存在一个经验的表达式:ks=1+0.15d/s=0.005(d/r)^2。在引入ks后,不同作者给出的平面电极系统和半球一平面电极系统碳纳米管膜的场致发射电流I与宏观表面电场强度E的关系都可以近似用-经验公式描述:I=a(E-Eo)^b,a,b为常数。该经验公式可为稳定生产的CNT膜片应用产品设计提供方便。 相似文献
38.
PLC这门课传统的实验方法是采用“平面型”的模块模仿生产流程,实验效果不理想。而采取教学仪器公司生产的仿真模块,具有“立体感”强的特点,实验效果好,但价格贵。针对这一情况,作者开发了几种价格低廉的仿真模块用于教学,取得了很好的效果,值得推广。本文介绍其中的4层电梯仿真模块的设计与实现。 相似文献
39.
40.