全文获取类型
收费全文 | 46617篇 |
免费 | 6024篇 |
国内免费 | 3009篇 |
专业分类
电工技术 | 6397篇 |
技术理论 | 2篇 |
综合类 | 2369篇 |
化学工业 | 7927篇 |
金属工艺 | 1340篇 |
机械仪表 | 3417篇 |
建筑科学 | 1278篇 |
矿业工程 | 602篇 |
能源动力 | 4472篇 |
轻工业 | 8250篇 |
水利工程 | 578篇 |
石油天然气 | 1657篇 |
武器工业 | 167篇 |
无线电 | 4088篇 |
一般工业技术 | 5204篇 |
冶金工业 | 2711篇 |
原子能技术 | 857篇 |
自动化技术 | 4334篇 |
出版年
2024年 | 276篇 |
2023年 | 1147篇 |
2022年 | 1926篇 |
2021年 | 2460篇 |
2020年 | 2228篇 |
2019年 | 2136篇 |
2018年 | 1908篇 |
2017年 | 2174篇 |
2016年 | 2186篇 |
2015年 | 2180篇 |
2014年 | 3157篇 |
2013年 | 3297篇 |
2012年 | 3423篇 |
2011年 | 3643篇 |
2010年 | 2472篇 |
2009年 | 2567篇 |
2008年 | 2105篇 |
2007年 | 2494篇 |
2006年 | 2223篇 |
2005年 | 1755篇 |
2004年 | 1489篇 |
2003年 | 1333篇 |
2002年 | 1147篇 |
2001年 | 924篇 |
2000年 | 788篇 |
1999年 | 660篇 |
1998年 | 560篇 |
1997年 | 486篇 |
1996年 | 406篇 |
1995年 | 341篇 |
1994年 | 287篇 |
1993年 | 250篇 |
1992年 | 219篇 |
1991年 | 189篇 |
1990年 | 127篇 |
1989年 | 99篇 |
1988年 | 68篇 |
1987年 | 64篇 |
1986年 | 62篇 |
1985年 | 60篇 |
1984年 | 52篇 |
1983年 | 37篇 |
1982年 | 63篇 |
1981年 | 75篇 |
1980年 | 37篇 |
1979年 | 13篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1975年 | 8篇 |
1974年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
张勇 《武汉理工大学学报(材料科学英文版)》2014,29(3):561-566
A new kind of composite buffering material was made by filling the voids of honeycomb paperboard with polyurethane. Drop tests were performed to evaluate the dynamic energy absorption capacity of the material. Based on the tests results, we analyzed the mechanical behaviors of the material under different conditions and obtained the inherent influencing laws of some factors on the material's dynamic buffering performance. It was shown that the dynamic buffering performance varied directly with impact velocity, and inversely with the void diameter, thickness and buffeting area of the composite material. 相似文献
53.
第二代农民工市民化利益要求的实现有助于从阶级基础、群众基础、执政理念、执政资源和执政环境等方面加强党的执政能力建设。在第二代农民工市民化背景下,党应该强化执政为民的理念,构建利益相关制度,强化第二代农民工的工人阶级意识和主人翁意识,鼓励他们积极参与政治生活,有组织、有秩序地进行利益表达,使他们充分享受到城市经济社会发展成果,同时提高党自身的执政能力。 相似文献
54.
以醋酸铜为模板,甲醇、氯仿为溶剂,2-乙烯吡啶、丙烯酰胺为功能单体,乙二醇二甲基丙烯酸酯为交联剂,采用本体聚合法制备铜离子印迹聚合物;然后掺入到壳聚糖海绵的制备中,使壳聚糖海绵对铜离子的吸附率由27.1%提高到72.3%。制备的铜离子印迹改性壳聚糖海绵需要2d达到吸附平衡,吸附-解吸5次后,性能稳定。 相似文献
55.
介绍了某露天山坡矿采用水耦合装药爆破技术,通过与常规爆破对比试验分析,提出利用水耦合爆破可以改善露天深孔爆破效果、提高原矿大块合格率和降低炸药单耗,达到安全增效、降耗的目的。 相似文献
56.
57.
采用外加恒电位下腐蚀电流-温度扫描方法研究了在0.5%Cl^-溶液中,SO4^2-浓度对316不锈钢点腐蚀行为的影响.结果表明,随着SO4^2-浓度的增加,钝化电流增加,开路电位降低.当SO4^2-浓度低于0.42%时,316不锈钢的临界点蚀温度比不存在SO4^2-时的临界点蚀温度低;当SO4^2-浓度大于0.42%时,临界点蚀温度比不存在SO4^2-时的临界点蚀温度高.从离子竞争吸附的角度进行分析,对SO4^2-加速与抑制点蚀两种作用规律的形成原因进行了解释. 相似文献
58.
F.c.c. solid Co---Pd alloys have been investigated thermodynamically by means of computer-aided Knudsen cell mass spectrometry. Thermodynamic evaluation has been performed by applying the “digital intensity ratio” method. The thermodynamic excess properties can be described algebraically by means of thermodynamically adapted power series with two adjustable parameters, i.e. C1G (−20 810 + 9.608T) J mol−1) and C2G (−30 720 + 6.78T) J mol−1). At 1470 K, f.c.c. solid Co---Pd alloys are characterized by negative molar excess Gibbs energies GE, exothermic molar heats of mixing (HE) and small negative molar excess entropies SE. At 1470 K, the minimum GE value is −4600 J mol−1 (61.9 at.% Pd), the minimum HE value is −9400 J mol−1 (59.5 at.% Pd) and the minimum SE value is −3.3 J mol−1 K−1 (55.9 at.% Pd). The thermodynamic activities of Co show small positive deviations from the ideal case for the Co-rich alloys (xPd < 0.34), and negative deviations from Raoults' law for alloys with higher Pd contents. The Pd activities aPd show negative deviations from the ideal case for all compositions. The phase diagram has been computed by means of a generally applicable procedure for the calculation of the equilibrium compositions of coexisting phases. This was achieved using the results of this work, thermodynamic data from earlier mass spectrometric studies on the liquid phase, and literature data for the heat capacities and enthalpies of Co and Pd. 相似文献
59.
H. -Y. Nie M. J. Walzak N. S. McIntyre 《Journal of Materials Engineering and Performance》2004,13(4):451-460
Atomic force microscopy (AFM) uses a very sharp pointed mechanical probe to collect real-space morphological information of
solid surfaces. AFM was used in this study to image the surface morphology of a biaxially oriented polypropylene film. The
polymer film is characterized by a nanometer-scale, fiberlike network structure, which reflects the drawing process used during
the fabrication of the film. AFM was used to study polymer-surface treatment to improve wettability by exposing the polymer
to ozone with or without ultraviolet (UV) irradiation. Surface-morphology changes observed by AFM are the result of the surface
oxidation induced by the treatment. Due to the topographic features of the polymer film, the fiberlike structure has been
used to check the performance of the AFM tip. An AFM image is a mixture of the surface morphology and the shape of the AFM
tip. Therefore, it is important to check the performance of a tip to ensure that the AFM image collected reflects the true
surface features of the sample, rather than contamination on the AFM tip. 相似文献
60.
Ontologies are structures, used for knowledge representation, which model domain knowledge in the form of concepts, roles, instances and their relationships. This knowledge can be exploited by an assessment system in the form of multiple choice questions (MCQs). The existing approaches, which use ontologies expressed in the Web Ontology Language (OWL) for MCQ generation, are limited to simple concept related questions — “What is C?” or “Which of the following is an example of C?” (where is a concept symbol) — or analogy type questions involving roles. There are no efforts in the literature which make use of the terminological axioms in the ontology such as existential, universal and cardinality restrictions on concepts and roles for MCQ generation. Also, there are no systematic methods for generating incorrect answers (distractors) from ontologies. Distractor generation process has to be given much importance, since the generated distractors determine the quality and hardness of an MCQ. We propose two new MCQ generation approaches, which generate MCQs that are very useful and realistic in conducting assessment tests, and the corresponding distractor generating techniques. Our distractor generation techniques, unlike other methods, consider the open-world assumption, so that the generated MCQs will always be valid (falsity of distractors is ensured). Furthermore, we present a measure to determine the difficulty level (a value between 0 and 1) of the generated MCQs. The proposed system is implemented, and experiments on specific ontologies have shown the effectiveness of the approaches. We also did an empirical study by generating question items from a real-world ontology and validated our results with the help of domain experts. 相似文献