全文获取类型
收费全文 | 30184篇 |
免费 | 2618篇 |
国内免费 | 1098篇 |
专业分类
电工技术 | 1352篇 |
技术理论 | 5篇 |
综合类 | 1583篇 |
化学工业 | 5696篇 |
金属工艺 | 1950篇 |
机械仪表 | 1678篇 |
建筑科学 | 2104篇 |
矿业工程 | 823篇 |
能源动力 | 967篇 |
轻工业 | 2282篇 |
水利工程 | 464篇 |
石油天然气 | 1866篇 |
武器工业 | 163篇 |
无线电 | 2916篇 |
一般工业技术 | 4180篇 |
冶金工业 | 1631篇 |
原子能技术 | 319篇 |
自动化技术 | 3921篇 |
出版年
2024年 | 135篇 |
2023年 | 569篇 |
2022年 | 872篇 |
2021年 | 1212篇 |
2020年 | 1040篇 |
2019年 | 887篇 |
2018年 | 1054篇 |
2017年 | 1148篇 |
2016年 | 1033篇 |
2015年 | 1227篇 |
2014年 | 1508篇 |
2013年 | 2161篇 |
2012年 | 1908篇 |
2011年 | 1970篇 |
2010年 | 1710篇 |
2009年 | 1586篇 |
2008年 | 1453篇 |
2007年 | 1369篇 |
2006年 | 1396篇 |
2005年 | 1205篇 |
2004年 | 832篇 |
2003年 | 871篇 |
2002年 | 921篇 |
2001年 | 766篇 |
2000年 | 672篇 |
1999年 | 738篇 |
1998年 | 645篇 |
1997年 | 467篇 |
1996年 | 452篇 |
1995年 | 376篇 |
1994年 | 310篇 |
1993年 | 230篇 |
1992年 | 185篇 |
1991年 | 139篇 |
1990年 | 107篇 |
1989年 | 64篇 |
1988年 | 77篇 |
1987年 | 55篇 |
1986年 | 49篇 |
1985年 | 53篇 |
1984年 | 59篇 |
1983年 | 41篇 |
1982年 | 35篇 |
1981年 | 33篇 |
1980年 | 32篇 |
1979年 | 26篇 |
1976年 | 24篇 |
1975年 | 22篇 |
1974年 | 22篇 |
1973年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
H. L. Du S. R. Rose Z. D. Xiang P. K. Datta X. Y. Li 《Materialwissenschaft und Werkstofftechnik》2003,34(4):421-426
The oxidation/sulphidation behaviour of a Ti‐46.7Al‐1.9W‐0.5Si alloy with a TiAl3 diffusion coating was studied in an environment of H2/H2S/H2O at 850oC. The kinetic results demonstrate that the TiAl3 coating significantly increased the high temperature corrosion resistance of Ti‐46.7Al‐1.9W‐0.5Si. The SEM, EDX, XRD and TEM analysis reveals that the formation of an Al2O3 scale on the surface of the TiAl3‐coated sample was responsible for the enhancement of the corroison resistance. The Ti‐46.7Al‐1.9W‐0.5Si alloy was also modified by Nb ion implantation. The Nb ion implanted and as received sampels were subjected to cyclic oxidation in an open air at 800oC. The Nb ion implantation not only increased the oxidation resistance but also substantially improved the adhesion of scale to the substrate. 相似文献
42.
文章设计了一种电子现金系统,关键是对安全性、效率、成本等进行综合考虑。从这些方面入手,论文分析了三种典型的电子现金系统—D.Chaum方案、S.Brands方案和T.okamoto方案。然后,结合匿名通信协议,提出如何更好地满足顾客利用公开网络进行安全通信的需求。 相似文献
43.
Polymer networks in which poly(propylene imine) dendrimers (Astramol?) are connected to each other by linear polytetrahydrofuran (polyTHF) segments, were prepared by two methods. The first method was a one‐step procedure in which bifunctionally living polyTHF, obtained by initiation of the THF polymerization with trifluoromethane sulfonic anhydride (triflic anhydride), was reacted with an amino‐dendrimer. This reaction was very fast but did not allow formation of the end products. The second method was a two‐step procedure. In a first step, living polyTHF, prepared with acryloyloxybutyl triflate as initiator, was grafted on an amino‐dendrimer, to form a star‐like, acrylate‐terminated polyTHF multi‐macromonomer with the dendrimer as core. In a second step, networks were obtained by Michael addition between the acrylate end‐groups and unreacted amino‐groups of the dendrimer. This cross‐linking reaction occurred spontaneously upon heating of the solution of the multi‐macromonomer with gelation times varying from a few minutes to a few hours, depending on the temperature and the composition of the prepolymers. With this method it was possible to prepare networks in the form of coatings or films. © 2003 Society of Chemical Industry 相似文献
44.
An optimization model for placement of wavelength converters to minimize blocking probability in WDM networks 总被引:7,自引:0,他引:7
Suixiang Gao Xiaohua Jia Chuanhe Huang Ding-Zhu Du 《Lightwave Technology, Journal of》2003,21(3):684-694
The introduction of wavelength converters in wavelength division multiplexing (WDM) networks can reduce the blocking probabilities of calls. In this paper, we study the problem of placing a given number of converters in a general topology WDM network such that the overall system blocking probability is minimized. The original contributions of this work are the following: 1) formulation of success probability in a network as a polynomial function of the locations of converters; 2) proposal of an optimization model of the converter placement problem as the minimization of a polynomial function of 0-1 variables under a linear constraint, so that standard optimization tools can be employed to solve the problem; and 3) design of a search algorithm that can efficiently find the optimal solution to the converter placement problem. Experiments have been conducted to demonstrate the effectiveness of the proposed model and the efficiency of the algorithm. 相似文献
45.
I. Budić-Leto T. Lovrić J. Gajdoš Kljusurić I. Pezo U. Vrhovšek 《European Food Research and Technology》2006,222(3-4):397-402
Identification of anthocyanins in the wine made of the Croatian autochthonous grape variety of Babić (Vitis vinifera L.) was carried out and their profile was determined by means of high-performance liquid chromatography with diode array
and mass spectrometric detection. Dependence of anthocyanins content and profile on maceration treatment conditions was investigated.
Statistically significant differences of anthocyanins concentration in wines Babić produced by various maceration treatments
were confirmed by the use of multivariate analysis of variances. The investigation results indicated that the maceration temperature
exerts higher influence on anthocyanins concentration than the duration of maceration. In addition, on the basis of anthocyanin
composition and using different multivariate statistical analyses, differentiation of wines Babić according to maceration
treatments was procured. 相似文献
46.
47.
48.
49.
对菱镁矿在固体燃料燃烧过程中的固硫特性进行了理论研究,所得结论对进一步将菱镁矿作为固体燃料燃烧过程中的固硫剂具有非常重要的意义。 相似文献
50.
Norton NBD 200 silicon nitride ceramics were implanted with sodium to a dose of 7.0×1015cm-2 at 72 keV (1 at% peak sodium content at 100 nm). The sodium-implanted samples were further implanted with aluminium to 7.3×1015cm-2 at 87 keV (1 at% peak aluminium content at 100 nm). The implanted and unimplanted samples were oxidized in 1 atm dry oxygen
at 1100 and 1300°C for 2–6 h. Profilometry and scanning electron microscopy measurements indicated that sodium implantation
led to up to a two-fold increase in the oxidation rate of silicon nitride. The sodium effect was effectively neutralized when
aluminium was co-implanted. The opposite effects of sodium and aluminium on the oxidation resistance of silicon nitride can
be attributed to their different roles in modifying the structure and properties of the oxide formed.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献