全文获取类型
收费全文 | 52429篇 |
免费 | 5466篇 |
国内免费 | 3563篇 |
专业分类
电工技术 | 3866篇 |
技术理论 | 2篇 |
综合类 | 5024篇 |
化学工业 | 3011篇 |
金属工艺 | 4904篇 |
机械仪表 | 7720篇 |
建筑科学 | 3434篇 |
矿业工程 | 2479篇 |
能源动力 | 1065篇 |
轻工业 | 4236篇 |
水利工程 | 698篇 |
石油天然气 | 808篇 |
武器工业 | 482篇 |
无线电 | 4678篇 |
一般工业技术 | 4400篇 |
冶金工业 | 2019篇 |
原子能技术 | 169篇 |
自动化技术 | 12463篇 |
出版年
2024年 | 197篇 |
2023年 | 943篇 |
2022年 | 1622篇 |
2021年 | 1908篇 |
2020年 | 1903篇 |
2019年 | 1460篇 |
2018年 | 1338篇 |
2017年 | 1579篇 |
2016年 | 1838篇 |
2015年 | 2049篇 |
2014年 | 3341篇 |
2013年 | 2826篇 |
2012年 | 3920篇 |
2011年 | 4046篇 |
2010年 | 2969篇 |
2009年 | 2965篇 |
2008年 | 2862篇 |
2007年 | 3694篇 |
2006年 | 3464篇 |
2005年 | 2977篇 |
2004年 | 2367篇 |
2003年 | 2013篇 |
2002年 | 1701篇 |
2001年 | 1489篇 |
2000年 | 1197篇 |
1999年 | 935篇 |
1998年 | 744篇 |
1997年 | 625篇 |
1996年 | 496篇 |
1995年 | 431篇 |
1994年 | 366篇 |
1993年 | 248篇 |
1992年 | 186篇 |
1991年 | 151篇 |
1990年 | 133篇 |
1989年 | 126篇 |
1988年 | 95篇 |
1987年 | 38篇 |
1986年 | 35篇 |
1985年 | 24篇 |
1984年 | 18篇 |
1983年 | 25篇 |
1982年 | 22篇 |
1981年 | 10篇 |
1980年 | 17篇 |
1979年 | 10篇 |
1978年 | 8篇 |
1977年 | 4篇 |
1974年 | 5篇 |
1959年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(45):19718-19731
Metals and alloys forming reversible hydrides with hydrogen gas are potential building blocks for compact, solid state hydrogen storage systems. Based on the materials’ thermodynamic characteristics, their use as temperature-swing gas compression and delivery systems in the hydrogen economy is also possible. Given the wide variety of materials developed and tested at laboratory and pilot scales, a harmonized method of selecting the feasible material(s) for a particular real-life application is required. This study proposes a system selection framework based on a normalized, multi-criteria metric. Using calculated values of multi-criteria metric, multi-criteria screening and ranking of potential materials has been demonstrated for a particular use case. It is found that the alloy TiMn1.52 having value of additive metric between 0.25 and 0.35 represents the best material for a single stage system. The alloy pair CaNi5–Ti1.5CrMn represents the best alternative for a two-stage system with additive metric values between 0.63 and 0.82. Energy and economic characteristics of the metal hydride gas compression and delivery systems are evaluated and compared with an equivalent mechanical compression system producing the same final effect (i.e., delivery of a given quantity of gas at a defined pressure). 相似文献
2.
3.
边坡位移的时间序列曲线存在复杂的非线性特性,传统的预测模型精度不足以满足预测要求。为此提出了基于变分模态分解的鸟群优化-核极限学习机的预测模型,并用于河北省某水泥厂的边坡位移预测。该方法首先采用VMD把边坡位移序列分解为一系列的有限带宽的子序列,再对各子序列分别采用相空间重构并用核极限学习机预测,采用鸟群算法优化相空间重构的嵌入维度和KELM中惩罚系数和核参数三个数值,以取得最优预测模型。最后将各个子序列预测值叠加,得到边坡位移的最终预测值。结果表明:和KELM、BSA-KELM、EEMD-BSA-KELM模型相比,基于VMD的BSA-KELM预测精度更高,为边坡位移的预测提供一种有效的方法。 相似文献
4.
在传统的轮胎表面缺陷依靠人工检测,存在劳动强度高、受人的主观影响大以及效率低下的问题。针对这一现象,研究了一种基于机器视觉的轮胎表面缺陷3D检测系统。该系统依靠机器视觉系统获取检测轮胎的表面图像,然后创建3D模型、判定缺陷类型,最终实现实时自动预警,为轮胎生产商提供一种自动化检测方案。系统集成了先进的技术、软件和工具,配套的信息管控系统可以对轮胎型号和生产数据进行采集、存储、分析,以便在生产过程中实现更高效、更可靠的质量控制,具有较高的实际应用推广价值。 相似文献
5.
6.
Yuzhu Su Junpu Wang Xin Li Qiqi Tang Jing Yang Li Lei Yi Tian Zhiwei Wang Duanwei He 《Ceramics International》2021,47(15):21077-21082
The in situ axial X-ray diffraction patterns of four ceramic powder samples (MgO, Al2O3, AlN, and cBN) that were compressed in a diamond anvil cell under uniaxial non-hydrostatic conditions were recorded. The microscopic deviatoric stress as a function of the pressure was determined from the X-ray diffraction peak broadening analysis: the curves increased approximately linearly with the pressure at the initial compression stage and then levelled off under further compression. Pressure-induced transparency was observed in all of the samples under compression, and the pressure at the turning point on the curves of the microscopic deviatoric stress versus pressure corresponded to the pressure at which the samples became transparent. Analysis of the microstructural features of the pressure-induced transparent samples indicated that the compression caused the grains to fracture, and the broken grains bonded with each other. We demonstrated that the ceramics’ pressure-induced transparency was a process during which the grains were squeezed and broken, the pores were close between the grains, and the broken grains were re-bonded under compression. 相似文献
7.
Corey Andrews Yiting Xu Michael Kirberger Jenny J. Yang 《International journal of molecular sciences》2021,22(1)
Calmodulin (CaM) is an important intracellular protein that binds Ca2+ and functions as a critical second messenger involved in numerous biological activities through extensive interactions with proteins and peptides. CaM’s ability to adapt to binding targets with different structures is related to the flexible central helix separating the N- and C-terminal lobes, which allows for conformational changes between extended and collapsed forms of the protein. CaM-binding targets are most often identified using prediction algorithms that utilize sequence and structural data to predict regions of peptides and proteins that can interact with CaM. In this review, we provide an overview of different CaM-binding proteins, the motifs through which they interact with CaM, and shared properties that make them good binding partners for CaM. Additionally, we discuss the historical and current methods for predicting CaM binding, and the similarities and differences between these methods and their relative success at prediction. As new CaM-binding proteins are identified and classified, we will gain a broader understanding of the biological processes regulated through changes in Ca2+ concentration through interactions with CaM. 相似文献
8.
9.
10.
为了降低机床等待过程中的能耗,提出了一种实时数据驱动的机床等待时间预测与节能控制方法。首先,建立了射频识别驱动的生产进度评估方法,并以生产进度数据作为输入,构建了基于堆栈降噪自编码的机床等待时间预测模型;其次,依据预测的机床等待时间,提出了机床状态切换方法,以降低机床能耗;最后,通过一个电梯零部件制造车间的案例分析,表明该方法的预测误差仅为4.1%,同时将机床等待过程能耗降低了57%,实现了制造车间的节能减排。 相似文献