全文获取类型
收费全文 | 33980篇 |
免费 | 2300篇 |
国内免费 | 1683篇 |
专业分类
电工技术 | 1346篇 |
技术理论 | 1篇 |
综合类 | 1731篇 |
化学工业 | 12609篇 |
金属工艺 | 1758篇 |
机械仪表 | 961篇 |
建筑科学 | 1086篇 |
矿业工程 | 420篇 |
能源动力 | 715篇 |
轻工业 | 4986篇 |
水利工程 | 377篇 |
石油天然气 | 2069篇 |
武器工业 | 250篇 |
无线电 | 2695篇 |
一般工业技术 | 2571篇 |
冶金工业 | 897篇 |
原子能技术 | 505篇 |
自动化技术 | 2986篇 |
出版年
2024年 | 386篇 |
2023年 | 624篇 |
2022年 | 2248篇 |
2021年 | 2283篇 |
2020年 | 967篇 |
2019年 | 948篇 |
2018年 | 838篇 |
2017年 | 993篇 |
2016年 | 1135篇 |
2015年 | 1206篇 |
2014年 | 1614篇 |
2013年 | 1816篇 |
2012年 | 2038篇 |
2011年 | 2422篇 |
2010年 | 1682篇 |
2009年 | 1880篇 |
2008年 | 1747篇 |
2007年 | 1868篇 |
2006年 | 1746篇 |
2005年 | 1406篇 |
2004年 | 1189篇 |
2003年 | 1033篇 |
2002年 | 887篇 |
2001年 | 708篇 |
2000年 | 599篇 |
1999年 | 555篇 |
1998年 | 422篇 |
1997年 | 398篇 |
1996年 | 378篇 |
1995年 | 355篇 |
1994年 | 308篇 |
1993年 | 205篇 |
1992年 | 174篇 |
1991年 | 147篇 |
1990年 | 133篇 |
1989年 | 101篇 |
1988年 | 78篇 |
1987年 | 49篇 |
1986年 | 71篇 |
1985年 | 46篇 |
1984年 | 48篇 |
1983年 | 31篇 |
1982年 | 36篇 |
1981年 | 30篇 |
1980年 | 32篇 |
1979年 | 34篇 |
1978年 | 14篇 |
1977年 | 11篇 |
1976年 | 10篇 |
1975年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
本文对生产高纯度丁烯-1的Alphabntol工艺进行了技术经济评价,认为该工艺条件简单、反应条件温和,而且投资少,所以很适合事在发展中国家应用。 相似文献
32.
Santosh D. Wanjale 《Polymer》2006,47(18):6414-6421
Poly(1-butene)/MWCNT nanocomposites were prepared by simple melt processing technique. Crystallization, crystal-to-crystal phase transformation and spherulitic morphology were studied using differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and optical microscopy (OM). The non-isothermal crystallization exhibited higher values of Zt derived from Avrami theory and lower values of F(T) obtained from Avrami-Ozawa analysis, while the isothermal crystallization revealed a significant increase in crystallization temperatures and lower crystallization half times compared to pristine PB. The observed changes in the crystallization kinetics were ascribed to the enhanced nucleation of PB in the presence of MWCNT. The nucleating activity calculated from the non-isothermal crystallization data revealed that the MWCNTs provide an active surface for the nucleation of PB. The optical micrographs exhibited significantly smaller crystallites with disordered morphology for the nanocomposites compared to the well defined spherulitic morphology for pristine PB. The rate of phase transformation from kinetically favored tetragonal to thermodynamically stable hexagonal form was noticeably enhanced as evidenced by the reduction in the half time for phase transformation from 58 h to 25 h for PB reinforced with 7% MWCNT. 相似文献
33.
设计一种TDM over IP的技术系统。该系统用FPGA将E1数据包通过串并转换到千兆以太网数据包,经IP网传输到终端设备,再通过并串转换将以太网数据包转换成E1数据包完成传输。经过软件和硬件测试验证了此系统在千兆以太网上传输的可行性,系统没有出现误码,固有输出抖动是0.55UI,最大峰值抖动指标均满足ITU-G.823标准要求。 相似文献
34.
35.
针对TV-L1分解模型在进行图像分解时所得到的结构部分有阶梯效应的问题,本文提出一种改进的图像分解模型即GJTV-L1模型。该模型首先得到结构部分的切向量场,由切向量场可得到结构部分的法向量场,然后拟合法向量场得到重构图像,即结构部分。通过仿真实验,验证了GJTV-L1模型和算法的合理性及有效性。 相似文献
36.
RADIOIMMUNOTOXICOLOGICALEFFECTOFENRICHEDURANIUMONCENTRALANDPERIPHERALIMMUNECELLSANDTHEPROTECTIVEACTIONOFIL-1ANDIL-2¥ZhuShoupe... 相似文献
37.
Seungae Lee Jahyun Koo Seung-Kyun Kang Gayoung Park Yung Jong Lee Yu-Yu Chen Seon Ah Lim Kyung-Mi Lee John A. Rogers 《Materials Today》2018,21(3):207-215
Biologically and environmentally resorbable electronic devices support application possibilities that cannot be addressed with conventional technologies. This paper presents highly conductive, water-soluble composites that can be printed to form contacts, interconnects, antennas, and other important features that are essential to nearly all systems of this type. An optimized material formulation involves in situ polymerization to yield a polyanhydride containing a dispersion of molybdenum microparticles at appropriate concentrations. Comparisons of essential physical and electrical properties of these materials to those of composites formed with other polymers and other metal microparticles reveal the relevant considerations. Various functional demonstrations of screen-printed test structures and devices illustrate the suitability of these conductive inks for use in water-soluble electronic devices. A key advantage of the material introduced here compared to alternatives is its ability to maintain conductance over significant periods of time while immersed in relevant aqueous solutions. Studies involving live animal models establish the biocompatibility. 相似文献
38.
Ferromagnetic and perovskite-like thin films (<1m) of La1–xCaxMnO3+ have been routinely prepared by heat treatment of an amorphous La–Ca–Mn precursor. The precursor was electrodeposited cathodically in the absence of oxygen and water onto polished silver substrates from a nonaqueous solution of the components' nitrates. Analysis by X-ray diffraction and SQUID magnetometry shows these materials exhibit the appropriate structural and magnetic phases indicative of colossal magnetoresistance. 相似文献
39.
40.
In this paper, we investigate an inexact hybrid projection-proximal method for solving a class of generalized mixed variational inequalities in Hilbert spaces. We construct a general inexact hybrid projection-proximal point algorithm, in which an inexact relaxed proximal point step is followed by a suitable orthogonal projection onto a hyperplane. Under some suitable conditions concerned with the pseudomonotone set-valued mapping T, the nonsmooth convex function f and the step size λk, we prove the convergence of the inexact hybrid projection-proximal point algorithm for solving generalized mixed variational inequalities in Hilbert spaces. 相似文献