全文获取类型
收费全文 | 1832550篇 |
免费 | 50171篇 |
国内免费 | 18700篇 |
专业分类
电工技术 | 51597篇 |
技术理论 | 56篇 |
综合类 | 25595篇 |
化学工业 | 316148篇 |
金属工艺 | 81322篇 |
机械仪表 | 64143篇 |
建筑科学 | 70862篇 |
矿业工程 | 22290篇 |
能源动力 | 59000篇 |
轻工业 | 132330篇 |
水利工程 | 20694篇 |
石油天然气 | 58211篇 |
武器工业 | 2787篇 |
无线电 | 229544篇 |
一般工业技术 | 324037篇 |
冶金工业 | 196293篇 |
原子能技术 | 37067篇 |
自动化技术 | 209445篇 |
出版年
2022年 | 13524篇 |
2021年 | 26791篇 |
2020年 | 20852篇 |
2019年 | 21739篇 |
2018年 | 25016篇 |
2017年 | 25843篇 |
2016年 | 30266篇 |
2015年 | 28985篇 |
2014年 | 43667篇 |
2013年 | 105278篇 |
2012年 | 55715篇 |
2011年 | 70733篇 |
2010年 | 61455篇 |
2009年 | 68640篇 |
2008年 | 62955篇 |
2007年 | 59726篇 |
2006年 | 62608篇 |
2005年 | 55492篇 |
2004年 | 51608篇 |
2003年 | 50298篇 |
2002年 | 48277篇 |
2001年 | 44795篇 |
2000年 | 43737篇 |
1999年 | 44503篇 |
1998年 | 57312篇 |
1997年 | 48330篇 |
1996年 | 43046篇 |
1995年 | 36907篇 |
1994年 | 33784篇 |
1993年 | 32247篇 |
1992年 | 28247篇 |
1991年 | 25046篇 |
1990年 | 24923篇 |
1989年 | 23623篇 |
1988年 | 21980篇 |
1987年 | 19952篇 |
1986年 | 19432篇 |
1985年 | 22513篇 |
1984年 | 22397篇 |
1983年 | 20300篇 |
1982年 | 19250篇 |
1981年 | 19290篇 |
1980年 | 17996篇 |
1979年 | 18472篇 |
1978年 | 17655篇 |
1977年 | 17714篇 |
1976年 | 19072篇 |
1975年 | 15882篇 |
1974年 | 15440篇 |
1973年 | 15524篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
M1080B无心外圆磨床砂轮及导轮宽度较窄,磨削轴承套圈外圆时,磨削效率低,托板架调整较为繁琐、皮带打滑、磨损较为严重。针对上述问题,提出了相应的解决办法,提高了磨削效率。 相似文献
992.
993.
994.
995.
996.
Filippo Lococo Massimiliano Paci Cristian Rapicetta Teresa Rossi Valentina Sancisi Luca Braglia Silvio Cavuto Alessandra Bisagni Italia Bongarzone Douglas M. Noonan Adriana Albini Sally Maramotti 《International journal of molecular sciences》2015,16(8):19612-19630
Assessment of biological diagnostic factors providing clinically-relevant information to guide physician decision-making are still needed for diseases with poor outcomes, such as non-small cell lung cancer (NSCLC). Epidermal growth factor receptor (EGFR) is a promising molecule in the clinical management of NSCLC. While the EGFR transmembrane form has been extensively investigated in large clinical trials, the soluble, circulating EGFR isoform (sEGFR), which may have a potential clinical use, has rarely been considered. This study investigates the use of sEGFR as a potential diagnostic biomarker for NSCLC and also characterizes the biological function of sEGFR to clarify the molecular mechanisms involved in the course of action of this protein. Plasma sEGFR levels from a heterogeneous cohort of 37 non-advanced NSCLC patients and 54 healthy subjects were analyzed by using an enzyme-linked immunosorbent assay. The biological function of sEGFR was analyzed in vitro using NSCLC cell lines, investigating effects on cell proliferation and migration. We found that plasma sEGFR was significantly decreased in the NSCLC patient group as compared to the control group (median value: 48.6 vs. 55.6 ng/mL respectively; p = 0.0002). Moreover, we demonstrated that sEGFR inhibits growth and migration of NSCLC cells in vitro through molecular mechanisms that included perturbation of EGF/EGFR cell signaling and holoreceptor internalization. These data show that sEGFR is a potential circulating biomarker with a physiological protective role, providing a first approach to the functional role of the soluble isoform of EGFR. However, the impact of these data on daily clinical practice needs to be further investigated in larger prospective studies. 相似文献
997.
Joo H. Kang Eujin Um Alexander Diaz Harry Driscoll Melissa J. Rodas Karel Domansky Alexander L. Watters Michael Super Howard A. Stone Donald E. Ingber 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(42):5657-5666
Magnetic nanoparticles have been employed to capture pathogens for many biological applications; however, optimal particle sizes have been determined empirically in specific capturing protocols. Here, a theoretical model that simulates capture of bacteria is described and used to calculate bacterial collision frequencies and magnetophoretic properties for a range of particle sizes. The model predicts that particles with a diameter of 460 nm should produce optimal separation of bacteria in buffer flowing at 1 L h−1. Validating the predictive power of the model, Staphylococcus aureus is separated from buffer and blood flowing through magnetic capture devices using six different sizes of magnetic particles. Experimental magnetic separation in buffer conditions confirms that particles with a diameter closest to the predicted optimal particle size provide the most effective capture. Modeling the capturing process in plasma and blood by introducing empirical constants (ce), which integrate the interfering effects of biological components on the binding kinetics of magnetic beads to bacteria, smaller beads with 50 nm diameters are predicted that exhibit maximum magnetic separation of bacteria from blood and experimentally validated this trend. The predictive power of the model suggests its utility for the future design of magnetic separation for diagnostic and therapeutic applications. 相似文献
998.
Pratik P. BHATT Venkatesh K. R. KODUR Anuj M. SHAKYA Tarek ALKHRDAJI 《Frontiers of Structural and Civil Engineering》2021,15(1):177
This paper presents the results of fire resistance tests on carbon fiber-reinforced polymer (CFRP) strengthened concrete flexural members, i.e., T-beams and slabs. The strengthened members were protected with fire insulation and tested under the combined effects of thermal and structural loading. The variables considered in the tests include the applied load level, extent of strengthening, and thickness of the fire insulation applied to the beams and slabs. Furthermore, a previously developed numerical model was validated against the data generated from the fire tests; subsequently, it was utilized to undertake a case study. Results from fire tests and numerical studies indicate that owing to the protection provided by the fire insulation, the insulated CFRP-strengthened beams and slabs can withstand four and three hours of standard fire exposure, respectively, under service load conditions. The insulation layer impedes the temperature rise in the member; therefore, the CFRP–concrete composite action remains active for a longer duration and the steel reinforcement temperature remains below 400°C, which in turn enhances the capacity of the beams and slabs. 相似文献
999.
在国家政策和市场需求的双重推动下,BIM技术在国内建筑领域迎来快速发展阶段,从最初的概念普及,到能够局部应用,再到现在能够全过程应用,其趋势是十分明确的,但是在其发展的过程中仍然存在着不少问题,如传统技术与BIM技术深入融合问题,BIM技术如何解决工程施工现场实际问题等.本文主要研究BIM技术在连云港民用机场迁建工程旅客过夜用房酒店项目中的综合应用,从协同建模、碰撞检查、管线综合、施工图深化出图及漫游展示等方面着手,着重解决BIM技术在施工过程中应用的落地问题,从而达到提高效率,缩短工期,降低成本,提升质量的目标. 相似文献
1000.
J. Grune K. Sempert M. Kuznetsov T. Jordan 《International Journal of Hydrogen Energy》2021,46(23):12487-12496
This paper presents results of experimental investigations on spherical and cylindrical flame propagation in pre-mixed H2/air-mixtures in unconfined and semi-confined geometries. The experiments were performed in a facility consisting of two transparent solid walls with 1 m2 area and four weak side walls made from thin plastic film. The gap size between the solid walls was varied stepwise from thin layer geometry (6 mm) to cube geometry (1 m). A wide range of H2/air-mixtures with volumetric hydrogen concentrations from 10% to 45% H2 was ignited between the transparent solid walls. The propagating flame front and its structure was observed with a large scale high speed shadow system. Results of spherical and cylindrical flame propagation up to a radius of 0.5 m were analyzed. The presented spherical burning velocity model is used to discuss the self-acceleration phenomena in unconfined and unobstructed pre-mixed H2/air flames. 相似文献