全文获取类型
收费全文 | 42027篇 |
免费 | 2108篇 |
国内免费 | 29篇 |
专业分类
电工技术 | 228篇 |
综合类 | 17篇 |
化学工业 | 6476篇 |
金属工艺 | 607篇 |
机械仪表 | 683篇 |
建筑科学 | 910篇 |
矿业工程 | 71篇 |
能源动力 | 540篇 |
轻工业 | 5405篇 |
水利工程 | 311篇 |
石油天然气 | 114篇 |
武器工业 | 5篇 |
无线电 | 1208篇 |
一般工业技术 | 5526篇 |
冶金工业 | 17542篇 |
原子能技术 | 117篇 |
自动化技术 | 4404篇 |
出版年
2024年 | 76篇 |
2023年 | 286篇 |
2022年 | 294篇 |
2021年 | 745篇 |
2020年 | 652篇 |
2019年 | 737篇 |
2018年 | 1332篇 |
2017年 | 1298篇 |
2016年 | 1345篇 |
2015年 | 1032篇 |
2014年 | 1205篇 |
2013年 | 2552篇 |
2012年 | 1903篇 |
2011年 | 1702篇 |
2010年 | 1412篇 |
2009年 | 1258篇 |
2008年 | 1225篇 |
2007年 | 1160篇 |
2006年 | 771篇 |
2005年 | 665篇 |
2004年 | 629篇 |
2003年 | 570篇 |
2002年 | 547篇 |
2001年 | 403篇 |
2000年 | 381篇 |
1999年 | 711篇 |
1998年 | 5441篇 |
1997年 | 3421篇 |
1996年 | 2134篇 |
1995年 | 1237篇 |
1994年 | 962篇 |
1993年 | 1146篇 |
1992年 | 260篇 |
1991年 | 330篇 |
1990年 | 253篇 |
1989年 | 270篇 |
1988年 | 285篇 |
1987年 | 231篇 |
1986年 | 200篇 |
1985年 | 196篇 |
1984年 | 126篇 |
1983年 | 103篇 |
1982年 | 175篇 |
1981年 | 190篇 |
1980年 | 218篇 |
1979年 | 78篇 |
1978年 | 101篇 |
1977年 | 462篇 |
1976年 | 1069篇 |
1973年 | 63篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
Nicholas A. Yaraghi Nicolás Guarín‐Zapata Lessa K. Grunenfelder Eric Hintsala Sanjit Bhowmick Jon M. Hiller Mark Betts Edward L. Principe Jae‐Young Jung Leigh Sheppard Richard Wuhrer Joanna McKittrick Pablo D. Zavattieri David Kisailus 《Advanced materials (Deerfield Beach, Fla.)》2016,28(32):6835-6844
995.
Henri Bataller Cédric Giraudet Fabrizio Croccolo José Maria Ortiz de Zárate 《Microgravity science and technology》2016,28(6):611-619
From the benchmark values of the diffusion and thermodiffusion coefficients of the tetralin, isobutylbenzene and n-dodecane ternary mixture, and the published optical contrast factors, we have evaluated the theoretical amplitudes of the two composition modes of the refractive-index fluctuations. Shadowgraph experiments have been performed on ground, where the current theory is expected to be correct only for large wave vectors. Two decay times have been observed experimentally. The fastest one being related to the thermal diffusivity of the mixture, while the slower one to mass diffusion. Hence, it has not been possible to distinguish the two eigenvalues of the mass diffusion matrix, a problem also encountered in traditional light-scattering with ternary mixtures of similar-size molecules. Thus, to compare the measured Intermediate Scattering Function with theory, we fix the amplitudes and decay rates to the benchmark values, use the wave number as a fitting parameter, and compare it to the experimental wave number. The good agreement between theory and experiments for the larger wave numbers validates the theory developed for the microgravity conditions. 相似文献
996.
Andrielli Morais de Oliveira Flávio de Andrade Silva Eduardo de Moraes Rego Fairbairn Romildo Dias Toledo Filho 《Materials and Structures》2018,51(3):65
This paper reports the experimental findings on the tensile behavior of strain-hardening cement-based composites (SHCC). The composites were subjected to the combined effects of elevated temperatures and internal moisture condition. Uniaxial tensile tests on dumbbell-shaped SHCC specimens with in situ temperature control were performed at 22, 60 and 100 °C. In addition, the effect of the internal humidity of SHCC (95, 50, 20 and 0%) coupled to the elevated temperatures was investigated. It was shown that the tensile strength decreases and the strain capacity increases with an increase in temperature. The influence of the internal moisture conditions was more significant in high temperatures. The strain capacity reduced significantly with a decrease in the humidity level. The crack pattern of the SHCC specimens was determined. Furthermore, single fiber pullout tests were performed under the considered high temperatures condition. Finally, the results are discussed based on the thermogravimetry analysis of the PVA fiber, alterations on its microstructure and surface coating. 相似文献
997.
Yury A. Villagrán-Zaccardi Anya Vollpracht Elke Gruyaert Nele De Belie 《Materials and Structures》2018,51(1):27
The performance of slag and fly ash in hydrated cementitious materials depends on the degree of reaction developed at the evaluated age. Several methods for the determination of the reaction degree of supplementary cementitious materials are available, among which the selective dissolution method is one of methods developed the earliest. This is a direct method that aims to quantify the amount of unreacted slag or fly ash in the sample by applying a selective acid attack. The degree of reaction is obtained from the comparison between the remaining unreacted SCM, which should not dissolve, and the total amount initially included in the mix. This recommendation indicates suitable procedures for computing the degree of reaction by selective dissolution of cement pastes containing slag and fly ash. Specific considerations are indicated for necessary corrections due to the imperfect selective dissolution when the procedure is applied to hydrated cement paste. 相似文献
998.
Daniel Vázquez-Nion Federica Troiano Patricia Sanmartín Chiara Valagussa Francesca Cappitelli Beatriz Prieto 《Materials and Structures》2018,51(6):158
Salt crystallisation is a very common and powerful weathering agent that can modify the petrophysical properties of building stone such as granite. In addition, the weathering can affect the susceptibility of the stone to biological colonisation. The aims of the present study were to examine the properties of a granite weathered by sodium chloride crystallisation and to evaluate the effects of the weathering on the secondary bioreceptivity of the stone to subaerial phototrophic biofilms. For this purpose, granite samples were subjected to a laboratory-based accelerated salt weathering test, and changes in weight, open porosity, bulk density, capillary water content, abrasion pH and surface roughness of the samples were determined. Samples of both weathered and non-weathered granite were then inoculated with a multi-species phototrophic culture derived from a natural subaerial biofilm and incubated under standardised laboratory conditions for 3 months. The weight loss produced by the weathering process was consistent with significant changes in abrasion pH and surface roughness. The bioreceptivity of the stone was also altered. According to the bioreceptivity index, the granite under study was characterised by ‘mild primary bioreceptivity’, but ‘high secondary bioreceptivity’ after the salt weathering process. Study of the secondary bioreceptivity of stone materials can provide very useful information about response to weathering effects, and the findings can be used to improve the selection of materials for building purposes. 相似文献
999.
1000.
Mónica Giménez‐Marqués Elena Bellido Thomas Berthelot Teresa Simón‐Yarza Tania Hidalgo Rosana Simón‐Vázquez África González‐Fernández José Avila Maria Carmen Asensio Ruxandra Gref Patrick Couvreur Christian Serre Patricia Horcajada 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(40)
Controlling the outer surface of nanometric metal–organic frameworks (nanoMOFs) and further understanding the in vivo effect of the coated material are crucial for the convenient biomedical applications of MOFs. However, in most studies, the surface modification protocol is often associated with significant toxicity and/or lack of selectivity. As an alternative, how the highly selective and general grafting GraftFast method leads, through a green and simple process, to the successful attachment of multifunctional biopolymers (polyethylene glycol (PEG) and hyaluronic acid) on the external surface of nanoMOFs is reported. In particular, effectively PEGylated iron trimesate MIL‐100(Fe) nanoparticles (NPs) exhibit suitable grafting stability and superior chemical and colloidal stability in different biofluids, while conserving full porosity and allowing the adsorption of bioactive molecules (cosmetic and antitumor agents). Furthermore, the nature of the MOF–PEG interaction is deeply investigated using high‐resolution soft X‐ray spectroscopy. Finally, a cell penetration study using the radio‐labeled antitumor agent gemcitabine monophosphate (3H‐GMP)‐loaded MIL‐100(Fe)@PEG NPs shows reduced macrophage phagocytosis, confirming a significant in vitro PEG furtiveness. 相似文献