全文获取类型
收费全文 | 83954篇 |
免费 | 9024篇 |
国内免费 | 5588篇 |
专业分类
电工技术 | 7176篇 |
技术理论 | 2篇 |
综合类 | 7357篇 |
化学工业 | 11521篇 |
金属工艺 | 5010篇 |
机械仪表 | 5885篇 |
建筑科学 | 7470篇 |
矿业工程 | 2540篇 |
能源动力 | 2656篇 |
轻工业 | 7215篇 |
水利工程 | 2172篇 |
石油天然气 | 3660篇 |
武器工业 | 976篇 |
无线电 | 9786篇 |
一般工业技术 | 8141篇 |
冶金工业 | 3324篇 |
原子能技术 | 1061篇 |
自动化技术 | 12614篇 |
出版年
2024年 | 399篇 |
2023年 | 1251篇 |
2022年 | 2549篇 |
2021年 | 3373篇 |
2020年 | 2629篇 |
2019年 | 2040篇 |
2018年 | 2367篇 |
2017年 | 2627篇 |
2016年 | 2423篇 |
2015年 | 3438篇 |
2014年 | 4499篇 |
2013年 | 5075篇 |
2012年 | 6016篇 |
2011年 | 6264篇 |
2010年 | 5881篇 |
2009年 | 5755篇 |
2008年 | 5834篇 |
2007年 | 5380篇 |
2006年 | 5211篇 |
2005年 | 4188篇 |
2004年 | 3372篇 |
2003年 | 3159篇 |
2002年 | 3851篇 |
2001年 | 3225篇 |
2000年 | 2008篇 |
1999年 | 1415篇 |
1998年 | 855篇 |
1997年 | 688篇 |
1996年 | 583篇 |
1995年 | 486篇 |
1994年 | 409篇 |
1993年 | 291篇 |
1992年 | 228篇 |
1991年 | 185篇 |
1990年 | 121篇 |
1989年 | 121篇 |
1988年 | 70篇 |
1987年 | 61篇 |
1986年 | 48篇 |
1985年 | 27篇 |
1984年 | 21篇 |
1983年 | 13篇 |
1982年 | 20篇 |
1981年 | 25篇 |
1980年 | 15篇 |
1979年 | 16篇 |
1978年 | 6篇 |
1965年 | 3篇 |
1959年 | 17篇 |
1951年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Zhang Huawei Yang Zhi Wu Zhaoyu Hong Xiaoyu Li Zhong Xu Yulai Li Jun Ni Gaojin Xiao Xueshan 《Oxidation of Metals》2019,92(1-2):49-65
Oxidation of Metals - The isothermal oxidation behavior and oxide-scale evolution on a newly developed Ni–Fe-based superalloy were investigated. Three oxidation stages were generally... 相似文献
32.
A novel bio‐based phthalonitrile resin derived from catechin: synthesis and comparison of curing behavior with petroleum‐based counterpart
下载免费PDF全文
![点击此处可从《Polymer International》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yu Qi Zhihuan Weng Jinyan Wang Shouhai Zhang Lishuai Zong Cheng Liu Xigao Jian 《Polymer International》2018,67(3):322-329
The development of bio‐based thermosetting resins with good thermal stability can potentially afford sustainable polymers as replacements for petroleum‐based polymers. We report a practical route to a novel catechin‐based phthalonitrile resin precursor (CA‐Ph), which contains free phenolic hydroxyl groups that result in ‘self‐curing’ at elevated temperatures to afford a thermostable polymer. Comparison of the performance of this CA‐Ph resin with that of a conventional petroleum‐based bisphenol A phthalonitrile resin (BPA‐Ph; containing 5 wt% of the curing agent 4,4′‐diaminodiphenylsulfone) revealed that CA‐Ph exhibits a lower melting point and curing temperature. Cured CA‐Ph resin retains 95% of its weight at 520 °C under a nitrogen atmosphere, which compares favorably with results obtained for BPA‐Ph resin that retains 95% of its weight at a lower temperature of 484 °C. Kinetic results indicated that the curing reactions of both CA‐Ph and BPA‐Ph systems follow an autocatalytic mechanism. These results suggest that catechin is a useful bio‐based feedstock for the preparation of self‐curing and thermally stable phthalonitrile resins for advanced technological applications. © 2017 Society of Chemical Industry 相似文献
33.
Jialin Sun Jun Zhao Xiuying Ni Feng Gong Zuoli Li 《Journal of the European Ceramic Society》2018,38(9):3096-3103
This work investigates the critical roles of two-step sintering (TSS) and laminated structure on the sintering behavior and mechanical properties of functionally graded WC-TiC-Al2O3 nanostructured composite materials doped with Cr3C2/VC. Results show that excellent mechanical properties are achieved for tailored TSS conditions with a hardness of 27.91?±?2.3?GPa and a flexural strength of 1423.3?±?23.5?MPa. The desirable mechanical properties are attributed to the suppressed grain growth without densification deterioration. TSS is more effective in facilitating the favorable dispersion of secondary phase toughening nano-particulates in a WC matrix than conventional sintering (CS). Cr3C2/VC dopant plays an important role in maximizing and shifting the temperature range of the kinetic window for WC-Al2O3 composites. Al2O3 crack deflection, transgranular Al2O3, microcracking, WC crack bridging and plate-like WC crack deflection are the major toughening mechanisms. Residual surface compressive stress induced by the graded structure is also an appreciated contribution to the improvement of mechanical properties. 相似文献
34.
Functional expression and synergistic cooperation of xylan‐degrading enzymes from Hypocrea orientalis and Aspergillus niger
下载免费PDF全文
![点击此处可从《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
35.
36.
37.
This paper considers a novel distributed iterative learning consensus control algorithm based on neural networks for the control of heterogeneous nonlinear multiagent systems. The system's unknown nonlinear function is approximated by suitable neural networks; the approximation error is countered by a robust term in the control. Two types of control algorithms, both of which utilize distributed learning laws, are provided to achieve consensus. In the provided control algorithms, the desired reference is considered to be an unknown factor and then estimated using the associated learning laws. The consensus convergence is proven by the composite energy function method. A numerical simulation is ultimately presented to demonstrate the efficacy of the proposed control schemes. 相似文献
38.
Tuntun Wang Dr. Sitansu Sekhar Nanda Dr. Georgia C. Papaefthymiou Prof. Dong Kee Yi 《Chembiochem : a European journal of chemical biology》2020,21(9):1254-1264
The extracellular matrix (ECM) is a macromolecular network that can provide biochemical and structural support for cell adhesion and formation. It regulates cell behavior by influencing biochemical and physical cues. It is a dynamic structure whose components are modified, degraded, or deposited during connective tissue development, giving tissues strength and structural integrity. The physical properties of the natural ECM environment control the design of naturally or synthetically derived biomaterials to guide cell function in tissue engineering. Tissue engineering is an important field that explores physical cues of the ECM to produce new viable tissue for medical applications, such as in organ transplant and organ recovery. Understanding how the ECM exerts physical effects on cell behavior, when cells are seeded in synthetic ECM scaffolds, is of utmost importance. Herein we review recent findings in this area that report on cell behaviors in a variety of ECMs with different physical properties, i.e., topology, geometry, dimensionality, stiffness, and tension. 相似文献
39.
Yao Dajie Liu Xiaofei Wu Jian 《International Journal of Control, Automation and Systems》2020,18(9):2251-2258
International Journal of Control, Automation and Systems - In this paper, the tracking problem for a class of uncertain nonlinearly parameterized systems with input delay based the adaptive... 相似文献
40.
针对电牵引采煤机渐开线行走轮在ANSYS分析中存在的问题,提出运用APDL语言命令直接建模,并通过VB与ANSYS的交互运行途径,设计了基于VB界面和程序的软件,实现了利用VB界面直接输入参数并调用ANSYS对行走轮自动建模、加载和计算的有限元分析。验证结果表明,该软件减少了设计人员的重复劳动,提高了行走轮的设计效率和水平,具有一定的工程实用价值。 相似文献