全文获取类型
收费全文 | 18589篇 |
免费 | 1411篇 |
国内免费 | 689篇 |
专业分类
电工技术 | 998篇 |
综合类 | 2055篇 |
化学工业 | 521篇 |
金属工艺 | 1285篇 |
机械仪表 | 4503篇 |
建筑科学 | 5254篇 |
矿业工程 | 858篇 |
能源动力 | 432篇 |
轻工业 | 190篇 |
水利工程 | 656篇 |
石油天然气 | 509篇 |
武器工业 | 170篇 |
无线电 | 299篇 |
一般工业技术 | 1192篇 |
冶金工业 | 1222篇 |
原子能技术 | 109篇 |
自动化技术 | 436篇 |
出版年
2024年 | 116篇 |
2023年 | 231篇 |
2022年 | 504篇 |
2021年 | 573篇 |
2020年 | 606篇 |
2019年 | 399篇 |
2018年 | 421篇 |
2017年 | 494篇 |
2016年 | 609篇 |
2015年 | 656篇 |
2014年 | 1133篇 |
2013年 | 815篇 |
2012年 | 1332篇 |
2011年 | 1356篇 |
2010年 | 997篇 |
2009年 | 1106篇 |
2008年 | 926篇 |
2007年 | 1310篇 |
2006年 | 1200篇 |
2005年 | 1064篇 |
2004年 | 782篇 |
2003年 | 719篇 |
2002年 | 651篇 |
2001年 | 538篇 |
2000年 | 459篇 |
1999年 | 371篇 |
1998年 | 305篇 |
1997年 | 239篇 |
1996年 | 222篇 |
1995年 | 134篇 |
1994年 | 124篇 |
1993年 | 75篇 |
1992年 | 49篇 |
1991年 | 33篇 |
1990年 | 25篇 |
1989年 | 24篇 |
1988年 | 16篇 |
1987年 | 18篇 |
1986年 | 9篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 13篇 |
1981年 | 2篇 |
1980年 | 9篇 |
1979年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
为提高圆锥动静压轴承的综合性能,以单位承载力下功耗最小和平均温升最低为优化目标,考虑几何结构约束条件,采用最优拉丁超立方进行设计空间的布点,进行有限元数值计算.基于计算结果,采用Kriging方法建立目标函数的近似代理模型.在此模型基础上,使用非劣分层遗传算法(NSGA-II)获得Pareto最优解集;最后通过权重系数... 相似文献
992.
王琦 《冶金设备管理与维修》2012,(2):26-28
介绍了精锻机蜗杆轴承中重要部件装配间隙的调整、相配精度检查和控制,解决了推力轴承间隙调整问题,达到了高精度轴承的要求,保证了设备运行的稳定性和可靠性。 相似文献
993.
《矿业科学技术学报(英文版)》2017,27(6):945-954
Mine entries close to residual bearing coal pillars(RBCPs) will suffer large deformation that may cause rock burst. To better understand the deformation mechanism and develop safe and practical guidelines for entry design, most studies focus on the absolute size of the stress field in and around the pillar. In this paper, we present a new approach to analyze the abnormal stress field close to a RBCP that uses the stress concentration coefficient(SCC), stress gradient(SG), and coefficient of lateral pressure(CLP) to describe the stress state induced by the RBCP. Based on elastic theory and a mathematical model for the abutment stress in the RBCP, an analytical solution for the abnormal stress in the strata below the RBCP was derived and the characteristics of the abnormal stress for a case study of a coal mine in China were analyzed. The results show that the abnormal stress field around the pillar is characterized by four distinct zones: a zone of high SCC, high SG, and CLP less than 1, a zone of high SCC, low SG, and CLP less than 1, a zone of low SCC, SG close to 0, and CLP greater than 1, and a zone of SCC close to 1, SC close to 0, and CLP close to 1. Based on this zoning pattern, a numerical model was established to study the combined effects of the abnormal stress on the stability of the entry. The most stable zone was determined based on a model of the Xinrui coal mine and verified by field measurements at the mine. Our conclusions can be used as guidelines for designing safe entry layouts in similar geological and mining settings. 相似文献
994.
995.
以淮河南岸一级阶地某高层建筑采用CFG桩复合地基工程实例,通过利用工程地质参数复核计算、静载荷试验、沉降观测等验证资料,来探讨说明CFG桩复合地基在该区高层建筑使用的安全适用性。 相似文献
996.
在介绍圆柱滚子轴承滚道无油沟套圈的磨削加工方法的过程中,重点阐述了在3M1420沟道磨床中采用成形切入磨削方法及砂轮修整时的改进方案。实践证明,采用成形切入磨削的加工方法,能够实现无油沟滚道的加工。 相似文献
997.
998.
To characterize the highly nonlinear hysteretic behavior of high damping rubber (HDR) bearings, a previously developed mathematical hysteresis model, rather than a simplified bilinear hysteresis model, is adopted in this study. Unilateral and bilateral seismic simulation tests of a scaled-down multistory structure isolated with HDR bearings subjected to three recorded earthquakes were conducted. Based on the unilateral test results, different sets of model parameters can be identified. The fidelity of the adopted hysteresis model is investigated by comparing the analytical predictions using all sets of identified parameters with results measured from the tests. The significant influence ascribed to different ground motion characteristics such as the effects of near-field and far-field earthquakes on modeling the hysteretic behavior of HDR bearings is observed. Besides, a feasibility study on applying the identified parameters of the adopted hysteresis model to predict the bilateral seismic responses is performed. Even though the prediction accuracy of the seismic responses is satisfactory in two orthogonally horizontal directions, the bilateral hysteretic modeling of HDR bearings requires further intensive studies considering the coupling effect under bilateral excitations. 相似文献
999.
《Thin》2014
Fire safety has become an important part in structural design due to the ever increasing loss of properties and lives during fires. Conventionally the fire rating of load bearing wall systems made of Light gauge Steel Frames (LSF) is determined using fire tests based on the standard time–temperature curve in ISO834 (ISO 834-1, 1999 [1]). However, modern commercial and residential buildings make use of thermoplastic materials, which mean considerably high fuel loads. Hence a detailed fire research study into the fire performance of LSF walls was undertaken using realistic design fire curves developed based on Eurocode parametric (ENV 1991-1-2, 2002 [2]) and Barnett's BFD (Barnett, 2002 [3]) curves using both full scale fire tests and numerical studies. It included LSF walls without cavity insulation, and the recently developed externally insulated composite panel system. This paper presents the details of finite element models developed to simulate the full scale fire tests of LSF wall panels under realistic design fires. Finite element models of LSF walls exposed to realistic design fires were developed, and analysed under both transient and steady state fire conditions using the measured stud time–temperature curves. Transient state analyses were performed to simulate fire test conditions while steady state analyses were performed to obtain the load ratio versus time and failure temperature curves of LSF walls. Details of the developed finite element models and the results including the axial deformation and lateral deflection versus time curves, and the stud failure modes and times are presented in this paper. Comparison with fire test results demonstrate the ability of developed finite element models to predict the performance and fire resistance ratings of LSF walls under realistic design fires. 相似文献
1000.
《Vacuum》2013
The synthesis of graphene on Cu foils has been carried out using a low-pressure chemical vapor deposition (LPCVD) process. Under certain growth conditions apart from the graphene flakes, undesired CuxO nanodots appear. The samples were characterized by scanning electron microscopy, atomic force microscopy, Raman spectroscopy and X-ray photoemission spectroscopy. On the basis of the results, we investigated the effect of growth parameters such as pressure, methane-to-hydrogen ratio and cooling atmosphere on the growth rate, the composition, especially the cleanliness of graphene by scanning electron microscopy in detail. It is shown that the obtained film is quite sensitive on the preparation conditions and the appearance of CuxO nanodots is preventable. 相似文献