全文获取类型
收费全文 | 601110篇 |
免费 | 9069篇 |
国内免费 | 1945篇 |
专业分类
电工技术 | 11317篇 |
综合类 | 657篇 |
化学工业 | 89689篇 |
金属工艺 | 21793篇 |
机械仪表 | 17977篇 |
建筑科学 | 15923篇 |
矿业工程 | 1810篇 |
能源动力 | 15699篇 |
轻工业 | 57932篇 |
水利工程 | 5208篇 |
石油天然气 | 5497篇 |
武器工业 | 81篇 |
无线电 | 78114篇 |
一般工业技术 | 112269篇 |
冶金工业 | 112410篇 |
原子能技术 | 9684篇 |
自动化技术 | 56064篇 |
出版年
2021年 | 4306篇 |
2019年 | 4085篇 |
2018年 | 6611篇 |
2017年 | 6757篇 |
2016年 | 7188篇 |
2015年 | 5235篇 |
2014年 | 8761篇 |
2013年 | 27617篇 |
2012年 | 14954篇 |
2011年 | 20994篇 |
2010年 | 16344篇 |
2009年 | 18617篇 |
2008年 | 19954篇 |
2007年 | 20257篇 |
2006年 | 18244篇 |
2005年 | 16774篇 |
2004年 | 16277篇 |
2003年 | 15815篇 |
2002年 | 15345篇 |
2001年 | 15316篇 |
2000年 | 14394篇 |
1999年 | 15072篇 |
1998年 | 34584篇 |
1997年 | 25098篇 |
1996年 | 19822篇 |
1995年 | 15485篇 |
1994年 | 13779篇 |
1993年 | 13310篇 |
1992年 | 10238篇 |
1991年 | 9696篇 |
1990年 | 9149篇 |
1989年 | 8761篇 |
1988年 | 8381篇 |
1987年 | 7253篇 |
1986年 | 7106篇 |
1985年 | 8575篇 |
1984年 | 8004篇 |
1983年 | 7100篇 |
1982年 | 6601篇 |
1981年 | 6663篇 |
1980年 | 6250篇 |
1979年 | 6047篇 |
1978年 | 5674篇 |
1977年 | 6831篇 |
1976年 | 8911篇 |
1975年 | 4928篇 |
1974年 | 4804篇 |
1973年 | 4730篇 |
1972年 | 3772篇 |
1971年 | 3405篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
Thermally conductive polymers offer new possibilities for the heat dissipation in electric and electronic components, for example, by a three‐dimensional shaping of the heat sinks. To face safety regulations, improved fire performance of those components is required. In contrast to unfilled polymers, those materials exhibit an entirely different thermal behavior. To investigate the flammability, a phosphorus flame retardant was incorporated into thermally conductive composites of polyamide 6 and hexagonal boron nitride. The flame retardant decreased the thermal conductivity only slightly. However, the burning behavior changed significantly, due to a different heat propagation, which was investigated using a thermographic camera. An optimum content of hexagonal boron nitride for a sufficient thermal conductivity and fire performance was found between 20 and 30 vol%. The improvement of the fire performance was due to a faster heat release out of the pyrolysis zone and an earlier decomposition of the flame retardant. For higher contents of hexagonal boron nitride, the heat was spread faster within the part, promoting an earlier ignition and increasing the decomposition rate of the flame retardant. 相似文献
103.
Scientometrics - This study investigates a potential relationship between highly-cited scholarly papers and the number of citations received by other papers with which they share a journal issue.... 相似文献
104.
Metallurgist - We consider domestic and foreign standards for rolled metals used in bridge building. Domestic standards contain elevated requirements to the reliability of rolled metals in terms of... 相似文献
105.
Kolmachikhina E. B. Sviridov A.V. Naumov K. D. 《Russian Journal of Non-Ferrous Metals》2020,61(5):488-493
Russian Journal of Non-Ferrous Metals - This article is devoted to the influence of sodium lignosulfonate (SL), anionic surfactants (sodium dodecylsulfate (SDS), sodium dodecylbenzene sulfonate... 相似文献
106.
Wireless Personal Communications - In this article compact multiple input multiple output (MIMO) antenna with triple notch at the ultra-wideband application having two identical monopole antennas... 相似文献
107.
Sebastian Roth Peter Stockinger Jakob Steff Simon Steimle Dr. Viktor Sautner Prof. Dr. Kai Tittmann Prof. Dr. Jürgen Pleiss Prof. Dr. Michael Müller 《Chembiochem : a European journal of chemical biology》2020,21(18):2615-2619
The family of NAD(P)H-dependent short-chain dehydrogenases/reductases (SDRs) comprises numerous biocatalysts capable of C=O or C=C reduction. The highly homologous noroxomaritidine reductase (NR) from Narcissus sp. aff. pseudonarcissus and Zt_SDR from Zephyranthes treatiae, however, are SDRs with an extended imine substrate scope. Comparison with a similar SDR from Asparagus officinalis (Ao_SDR) exhibiting keto-reducing activity, yet negligible imine-reducing capability, and mining the Short-Chain Dehydrogenase/Reductase Engineering Database indicated that NR and Zt_SDR possess a unique active-site composition among SDRs. Adapting the active site of Ao_SDR accordingly improved its imine-reducing capability. By applying the same strategy, an unrelated SDR from Methylobacterium sp. 77 (M77_SDR) with distinct keto-reducing activity was engineered into a promiscuous enzyme with imine-reducing activity, thereby confirming that the ability to reduce imines can be rationally introduced into members of the “classical” SDR enzyme family. Thus, members of the SDR family could be a promising starting point for protein approaches to generate new imine-reducing enzymes. 相似文献
108.
109.
110.
The Interplay of Modulus,Strength, and Ductility in Adhesive Design Using Biomimetic Polymer Chemistry
下载免费PDF全文
![点击此处可从《Advanced functional materials》网站下载免费的PDF全文](/ch/ext_images/free.gif)
High‐performance adhesives require mechanical properties tuned to demands of the surroundings. A mismatch in stiffness between substrate and adhesive leads to stress concentrations and fracture when the bonding is subjected to mechanical load. Balancing material strength versus ductility, as well as considering the relationship between adhesive modulus and substrate modulus, creates stronger joints. However, a detailed understanding of how these properties interplay is lacking. Here, a biomimetic terpolymer is altered systematically to identify regions of optimal bonding. Mechanical properties of these terpolymers are tailored by controlling the amount of a methyl methacrylate stiff monomer versus a similar monomer containing flexible poly(ethylene glycol) chains. Dopamine methacrylamide, the cross‐linking monomer, is a catechol moiety analogous to 3,4‐dihydroxyphenylalanine, a key component in the adhesive proteins of marine mussels. Bulk adhesion of this family of terpolymers is tested on metal and plastic substrates. Incorporating higher amounts of poly(ethylene glycol) into the terpolymer introduces flexibility and ductility. By taking a systematic approach to polymer design, the region in which material strength and ductility are balanced in relation to the substrate modulus is found, thereby yielding the most robust joints. 相似文献