全文获取类型
收费全文 | 10159篇 |
免费 | 234篇 |
国内免费 | 304篇 |
专业分类
电工技术 | 286篇 |
综合类 | 201篇 |
化学工业 | 1327篇 |
金属工艺 | 399篇 |
机械仪表 | 711篇 |
建筑科学 | 53篇 |
矿业工程 | 35篇 |
能源动力 | 420篇 |
轻工业 | 87篇 |
水利工程 | 13篇 |
石油天然气 | 13篇 |
武器工业 | 32篇 |
无线电 | 2660篇 |
一般工业技术 | 3306篇 |
冶金工业 | 63篇 |
原子能技术 | 127篇 |
自动化技术 | 964篇 |
出版年
2024年 | 5篇 |
2023年 | 115篇 |
2022年 | 153篇 |
2021年 | 179篇 |
2020年 | 157篇 |
2019年 | 166篇 |
2018年 | 165篇 |
2017年 | 230篇 |
2016年 | 277篇 |
2015年 | 267篇 |
2014年 | 502篇 |
2013年 | 444篇 |
2012年 | 482篇 |
2011年 | 955篇 |
2010年 | 546篇 |
2009年 | 622篇 |
2008年 | 601篇 |
2007年 | 513篇 |
2006年 | 542篇 |
2005年 | 406篇 |
2004年 | 380篇 |
2003年 | 359篇 |
2002年 | 335篇 |
2001年 | 217篇 |
2000年 | 232篇 |
1999年 | 273篇 |
1998年 | 252篇 |
1997年 | 240篇 |
1996年 | 254篇 |
1995年 | 152篇 |
1994年 | 148篇 |
1993年 | 100篇 |
1992年 | 94篇 |
1991年 | 88篇 |
1990年 | 71篇 |
1989年 | 72篇 |
1988年 | 41篇 |
1987年 | 7篇 |
1986年 | 9篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1976年 | 3篇 |
1975年 | 5篇 |
1974年 | 2篇 |
1973年 | 5篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
The switchable optical properties of Pd-protected RCo2-type Ho0.6Mm0.4Co2 alloy thin films have been investigated in a KOH electrolyte. The reversible optical switching has been carried out simultaneously by measuring transmitted light through the thin film during electrochemical charging–discharging of hydrogen. The dependence of switching speed and cyclic durability of the film on the charging and discharging current density as well as concentration of KOH electrolyte has been studied. In addition, cyclic voltammetric measurements have been performed to examine the hydride formation and decomposition reactions. 相似文献
22.
Xiaojun Xie Yonghong Cheng Hong Wang Qian Wang Xiaolin Chen Caixin Sun 《Ceramics International》2008,34(4):689-693
In the ideal A2B2O6O′ pyrochlore structure, the x-value of O atom position is a variable parameter. In Bi1.5ZnNb1.5−xTaxO7 (BZNT) cubic pyrochlores, the x-values alter with the different compositions of Nb/Ta. In this work, a series of initial models for BZNT were established by analyzing X-ray diffraction data. Then three structure modifying methods, including Rietveld refinement, Rietveld refinement with energy and geometry optimization based on quantum mechanics, were employed to obtain the precise models using Materials Studio. Moreover, the reflectivities of BZNT were computed by quantum mechanical simulation based on the refined models. Comparing the simulation results from different modifying models with the experimental results, it is found that Rietveld refinement with energy optimization is the most accurate method for BZNT pyrochlores. According to the simulation results, the different reflectivities correspond well with various x-values of O atom positions in BZNT pyrochlores. 相似文献
23.
K. Uchiyama T. Shiosaki T. Kosaka A. Kasamatsu M. Echizen 《Ceramics International》2008,34(4):979-983
Advanced sol–gel methods using a secondary solvent addition into (Pb, La)(Zr, Ti)O3 (PLZT) sol–gel solution and a methanol pre-treatment of sapphire substrates are demonstrated. For the secondary solvent addition, the additive affected the crystallinity and electro-optic (EO) property of PLZT films and only methanol addition can improve them. In addition, the methanol pre-treatment is also appeared to be effective to improve film characteristics.
Through these optimizations, epitaxially grown PLZT thin films on r-cut sapphire are obtained and a high Pockels coefficient which is comparable to those of bulk PLZTs is achieved. It is believed that these PLZT thin films are applicable for integrated EO devices and open the door for the future data communication systems. 相似文献
24.
Interfacial hybridization kinetics of oligonucleotides immobilized onto fused silica surfaces 总被引:3,自引:0,他引:3
Jiang Zeng Amer Almadidy James Watterson Ulrich J. Krull 《Sensors and actuators. B, Chemical》2003,90(1-3):68-75
Fused silica optical fibers have been used in an intrinsic mode optical configuration as biosensors for fluorescence based detection of hybridization of nucleic acids. In this work, the kinetics of hybridization of single-stranded oligonucleotides that were covalently immobilized were studied. The probe DNA was dT20, and the target was Fluorescein-labeled non-complementary (dT20) or complementary (dA20) oligonucleotide. Chronofluorimetric monitoring of the adsorption and hybridization processes was used to investigate oligonucleotide films of different density, in different salt concentrations, at temperatures of 25 and 40 °C, with the concentration of the target DNA being 0.005–0.1 μM. Mathematical models based on first- and second-order Langmuir adsorption have been examined to describe both the adsorption and the hybridization processes. Experimental data were processed using the models, and the hybridization kinetics were calculated. Hybridization kinetics on these optical fiber DNA sensors was found to be up to three orders faster than results presented for a number of other experiments using different immobilization chemistries. 相似文献
25.
介绍了间接跃迁的半导体AlP与GaP形成的超晶格,由于零折叠效应,实现了能带由间接带隙向直接带隙的转变,从而增加了带间的光跃迁几率,并推导了该几率的表达式。 相似文献
26.
1IntrodctionThesdV8fltsg6Sofffi1CY0bCfldf山CY0ptlCS6fiS0f8f6lflt6llSltyffiDdU18tlflgsliddCtCCtlflg,simpletechnique,highrellabllltyandlowprice,thereformlcrobendfiberoptlcsensorIswidelyusedtomeasurementofstrain,stressandv比rationetc.Inpractice,thesensltlvltyofsensorIsaveryimportantparameter,andthesensltlvltyofmlcrobendf山eroptlcsensorIsmainlyrelat-6dtofoil0WlflgthY66f8CtofS[‘-:ffilCfob6fldsffiplltlld6:fillffib6yofthlCY0b6fldS6Ct10llSsfldffil-crobendperiod,andmlcrobendperio… 相似文献
27.
155Mb/s时分光交换系统 总被引:1,自引:0,他引:1
本文介绍了国内第一个155Mb/s时分光交换实验系统。系统以新型半导体光器件-半导体光开关门为核心构成,传输速度为155Mb/s。 相似文献
28.
Alena Orlov 《Materials Science and Engineering: A》1996,220(1-2):117-122
The present work studies the collection of experimental data from which Raj and Pharr (Mater. Sci. Eng., 81 (1986) 217) deduced a universal empirical dependence of the subgrain size on the applied stress. In accord with their result and some theoretical predictions the normalized subgrain size ds/b was ssumed to be proportional to G/σ (G is the shear modulus, b the Burgers vector length, σ the applied stress). The evaluated factor of proportionality K1, having the value within the interval from 0.76 to 180 in the inspected data sets, was discussed from the point of view of various factors which can influence the experimental data. 相似文献
29.
薄膜干涉型光学全通滤波器的设计与分析 总被引:1,自引:0,他引:1
设计并分析了用于多信道色谱补偿的薄膜Gires-Tournois干涉仪(GTI)型光学全通滤波(OAPF),讨论了反射镜的膜层结构对器件 的群延迟谱和反射谱的影响,。以及大角度入射引起的偏分离现象和幅度畸变现象,给出了单级和多级串拉OAPF的初步设计结果。 相似文献
30.