全文获取类型
收费全文 | 15492篇 |
免费 | 1478篇 |
国内免费 | 674篇 |
专业分类
电工技术 | 903篇 |
技术理论 | 1篇 |
综合类 | 1008篇 |
化学工业 | 2802篇 |
金属工艺 | 865篇 |
机械仪表 | 1015篇 |
建筑科学 | 1095篇 |
矿业工程 | 448篇 |
能源动力 | 419篇 |
轻工业 | 1048篇 |
水利工程 | 299篇 |
石油天然气 | 774篇 |
武器工业 | 112篇 |
无线电 | 1755篇 |
一般工业技术 | 2145篇 |
冶金工业 | 708篇 |
原子能技术 | 168篇 |
自动化技术 | 2079篇 |
出版年
2024年 | 89篇 |
2023年 | 302篇 |
2022年 | 478篇 |
2021年 | 666篇 |
2020年 | 577篇 |
2019年 | 424篇 |
2018年 | 501篇 |
2017年 | 545篇 |
2016年 | 454篇 |
2015年 | 621篇 |
2014年 | 807篇 |
2013年 | 954篇 |
2012年 | 948篇 |
2011年 | 948篇 |
2010年 | 899篇 |
2009年 | 811篇 |
2008年 | 748篇 |
2007年 | 795篇 |
2006年 | 811篇 |
2005年 | 651篇 |
2004年 | 459篇 |
2003年 | 497篇 |
2002年 | 566篇 |
2001年 | 454篇 |
2000年 | 380篇 |
1999年 | 385篇 |
1998年 | 341篇 |
1997年 | 290篇 |
1996年 | 256篇 |
1995年 | 202篇 |
1994年 | 168篇 |
1993年 | 118篇 |
1992年 | 102篇 |
1991年 | 83篇 |
1990年 | 64篇 |
1989年 | 49篇 |
1988年 | 46篇 |
1987年 | 25篇 |
1986年 | 31篇 |
1985年 | 10篇 |
1984年 | 16篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1981年 | 11篇 |
1980年 | 14篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 8篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
The technique which is described combines the advantages of the techniques formerly proposed in the literature in each stage of the preparation of transmission electron microscopy (TEM) specimens including a single metal-ceramic interface. It allows easy handling of the thin foils in spite of their brittleness. Preferential thinning of the softer material in the two-phase foil is prevented, and both sides of the interface are thinned down to comparable thicknesses. The nickel-alumina bicrystal interface observed in TEM is neat and free from any reaction layer. This method is easily adaptable to other metal-ceramic systems. 相似文献
82.
In this paper we present a Multi-Element generalized Polynomial Chaos (ME-gPC) method to deal with stochastic inputs with arbitrary probability measures. Based on the decomposition of the random space of the stochastic inputs, we construct numerically a set of orthogonal polynomials with respect to a conditional probability density function (PDF) in each element and subsequently implement generalized Polynomial Chaos (gPC) locally. Numerical examples show that ME-gPC exhibits both p- and h-convergence for arbitrary probability measures 相似文献
83.
84.
Summary Cyclic tris(ethylene terephthalate) (CTET) was separated from oligomeric extract of poly(ethylene terephthalate) by the conventional solvent separation method. The structure of CTET was characterized by differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy. It is shown that the double melting behavior of meltcrystallized CTET is attributed to the morphological change created by heat-treatment. The effect of the morphological change on the crystal structure of CTET was also examined. 相似文献
85.
Outdoor log storage without protection can change the mechanical and chemical properties of wood due to infection by various fungi. To understand how outdoor log storage affects the wood and, subsequently, the strandboard quality, two piles of aspen logs were set up outside and stored for a period of four months (July to November). One of the piles was treated with a biological solution to prevent fungal growth. The other one was stored without treatment. Both piles contained non-debarked and partially debarked logs. Evaluation of sap stain development indicated that all logs had been colonized by staining fungi with average stain coverage of 9.37 to 57.18% and maximum stain penetration of 3.58 to 7.27 cm over the log cross section. The variation of fungal colonization depended on log treatment and bark condition. The most effective way to prevent stain growth was the combination of biological treatment and partial debarking. A series of strandboard was prepared from fresh and aged aspen logs. All boards made from stored logs were statistically comparable to or superior to the control boards made from fresh aspen logs. The boards made from treated/partially debarked and untreated/non-debarked logs were statistically comparable to each other except for wet MOR. In addition, these two board types were statistically stronger than other boards made from treated/non-debarked and untreated/partially debarked logs in terms of IB and water resistance. Some individual stained strands were observed on the finished board surface. Less staining was found in the boards prepared from biologically treated and partially debarked logs, compared with those made from other stored logs. 相似文献
86.
本文简要介绍了ER流体现象及其力学和电学性能,给出了描述ER流体行为的一般理论,提出了ER流体应用中目前存在的主要问题。 相似文献
87.
ARCGIS环境下基于DEM的流域特征提取 总被引:10,自引:0,他引:10
研究选取位于陕西省延安城南12 km处的万花乡向阳沟小流域。采用1∶10000大比例尺的比例尺5 m分辨率的DEM作为基本的地形数据,应用ESR I公司开发的ARCG IS地理信息系统软件进行流域特征的提取。经分析得到了研究区域河网特征以及研究区其它常用的流域特征信息,与实际河流水系特征基本吻合,认为应用DEM划分的流域结果是合理的。 相似文献
88.
89.
万程欣,EXPLO-500T型拖拉机式地震钻机.物探装备,2006,16(4):314-316
EXPLO—500T型拖拉机式地震钻机采用大马力拖拉机底盘、全液压控制,结构紧凑、操作简单、可靠性强、钻井效率高,特别适合林带、丘陵地区施工。 相似文献
90.
Facile synthesis of ordered nanocrystalline alumina thin films with tunable mesopore structures 总被引:1,自引:0,他引:1
Lijuan Wan Honggang Fu Keying Shi Xiqiang Tian 《Microporous and mesoporous materials》2008,115(3):301-307
Mesoporous alumina layers have attracted attention for their potential use in ultrafiltration of salts, as a heterogeneous catalyst support, an adsorbent in environmental cleanup, and in petroleum refinement. The ability to control the fast hydrolysis rate of the inorganic precursors using simple and inexpensive routes is important for that potential to be realized. Herein, we introduce a novel and facile route to synthesize mesoporous alumina thin films from the combination of inexpensive and commercially available copolymer with aluminum chloride or nitrate (salts) in an EtOH–surfactant–NH3 · H2O–salts (EsNs) system through the evaporation-induced self-assembly (EISA) method. Mesoporous alumina layers obtained utilizing the EsNs system have ordered and tunable pore structures. The ability to easily control the mesophases of the alumina layers within a short time provides distinct advantages over previously reported synthesis procedures. Most importantly, we demonstrate that the binding of surfactant and NH3 · H2O for the formation of hydrogen bond between them in the EsNs system controls the fast hydrolysis rate of the inorganic species. This allows for the synthesis of nanocrystalline alumina layers via the aluminum oxo-clusters’ assembly with the surfactant. Such simple route may be applied in the synthesis of other non-silica mesostructured oxides. 相似文献