全文获取类型
收费全文 | 4979篇 |
免费 | 795篇 |
国内免费 | 667篇 |
专业分类
电工技术 | 563篇 |
技术理论 | 2篇 |
综合类 | 770篇 |
化学工业 | 272篇 |
金属工艺 | 138篇 |
机械仪表 | 215篇 |
建筑科学 | 235篇 |
矿业工程 | 65篇 |
能源动力 | 65篇 |
轻工业 | 122篇 |
水利工程 | 49篇 |
石油天然气 | 43篇 |
武器工业 | 104篇 |
无线电 | 1129篇 |
一般工业技术 | 324篇 |
冶金工业 | 98篇 |
原子能技术 | 6篇 |
自动化技术 | 2241篇 |
出版年
2024年 | 40篇 |
2023年 | 131篇 |
2022年 | 152篇 |
2021年 | 195篇 |
2020年 | 222篇 |
2019年 | 224篇 |
2018年 | 170篇 |
2017年 | 206篇 |
2016年 | 225篇 |
2015年 | 250篇 |
2014年 | 398篇 |
2013年 | 363篇 |
2012年 | 424篇 |
2011年 | 464篇 |
2010年 | 340篇 |
2009年 | 351篇 |
2008年 | 299篇 |
2007年 | 341篇 |
2006年 | 261篇 |
2005年 | 254篇 |
2004年 | 187篇 |
2003年 | 171篇 |
2002年 | 129篇 |
2001年 | 105篇 |
2000年 | 94篇 |
1999年 | 86篇 |
1998年 | 58篇 |
1997年 | 45篇 |
1996年 | 44篇 |
1995年 | 37篇 |
1994年 | 39篇 |
1993年 | 34篇 |
1992年 | 29篇 |
1991年 | 13篇 |
1990年 | 12篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1963年 | 2篇 |
1962年 | 2篇 |
1961年 | 2篇 |
1960年 | 2篇 |
排序方式: 共有6441条查询结果,搜索用时 859 毫秒
1.
Priyadarshi Chakraborty Yiming Tang Tomoya Yamamoto Yifei Yao Tom Guterman Shai Zilberzwige-Tal Nofar Adadi Wei Ji Tal Dvir Ayyalusamy Ramamoorthy Guanghong Wei Ehud Gazit 《Advanced materials (Deerfield Beach, Fla.)》2020,32(9):1906043
Self-assembled peptide hydrogels represent the realization of peptide nanotechnology into biomedical products. There is a continuous quest to identify the simplest building blocks and optimize their critical gelation concentration (CGC). Herein, a minimalistic, de novo dipeptide, Fmoc-Lys(Fmoc)-Asp, as an hydrogelator with the lowest CGC ever reported, almost fourfold lower as compared to that of a large hexadecapeptide previously described, is reported. The dipeptide self-assembles through an unusual and unprecedented two-step process as elucidated by solid-state NMR and molecular dynamics simulation. The hydrogel is cytocompatible and supports 2D/3D cell growth. Conductive composite gels composed of Fmoc-Lys(Fmoc)-Asp and a conductive polymer exhibit excellent DNA binding. Fmoc-Lys(Fmoc)-Asp exhibits the lowest CGC and highest mechanical properties when compared to a library of dipeptide analogues, thus validating the uniqueness of the molecular design which confers useful properties for various potential applications. 相似文献
2.
Kamalesh Pal Amitava Mukherjee Md. Motin Seikh Parthasarathi Bera Arup Gayen 《Ceramics International》2021,47(10):14798-14808
Synthesis of nanocrystalline pristine and Mn-doped calcium copper titanate quadruple perovskites, CaCu3?xMnxTi4?xMnxO12 (x = 0, 0.5, and 1.0) by modified citrate solution combustion method has been reported. Powder X-ray diffraction patterns attest the phase purity of the perovskite materials. Average particle sizes of all the materials obtained from the Scherrer's formula are in the range of 55–70 nm. The specific surface areas for all the perovskites obtained from BET isotherms are found to be low as expected for the condensed oxide systems and fall in the range of 13–17 m2 g?1. Transmission electron microscopy studies show a reduction in particle size of CaCu3Ti4O12 with increase in Mn doping. Ca and Ti are present in +2 and +4 oxidation states in all the materials as demonstrated by X-ray photoelectron spectroscopy analyses. Cu2+ gets reduced in CaCu3Ti4O12 with higher Mn content. Mn is observed to be present only in +3 oxidation state. All the materials have been examined to be active in CO oxidation as well as H2 production from methanol steam reforming. CaCu3Ti4O12 with ~14 at.% Mn is found to show best catalytic activities among these materials. A comprehensive analysis of the catalytic activities of these perovskites toward CO oxidation and H2 production from MSR reveal the cooperative activity of copper-manganese in the doped perovskites and it is more effective at lower manganese content. 相似文献
3.
Combinatorial auction is a useful trade manner for transportation service procurements in e-marketplaces. To enhance the competition of combinatorial auction, a novel auction mechanism of two-round bidding with bundling optimization is proposed. As the recommended the auction mechanism, the shipper/auctioneer integrates the objects into several bundles based on the bidding results of first round auction. Then, carriers/bidders bid for the object bundles in second round. The bundling optimization is described as a multi-objective model with two criteria on price complementation and combination consistency. A Quantum Evolutionary Algorithm (QEA) with β-based rotation gate and the encoding scheme based on non-zero elements in complementary coefficient matrix is developed for the model solution. Comparing with a Contrast Genetic Algorithm, QEA can achieve better computational performances for small and middle size problems. 相似文献
4.
5.
This article deals with the kinetics of two-step anionic polymerization by way of a non-steady state method. Several molecular parameters can be evaluated using the formulae developed. A bimodal molecular weight distribution function for the resulting polymer is derived from the set of kinetic differential equations, which is in agreement with the experimental data reported. 相似文献
6.
大系统分散鲁棒容错控制的进展及主要成果 总被引:1,自引:0,他引:1
综述了近20年来关联大系统分散鲁棒容错控制的研究动态及取得的主要成果。说明了统一地研究分散鲁棒容错控制的必要性。在分散控制、鲁棒控制和容错控制研究领域内,分析了各种设计方法的主导思想及实质;指出了这些研究成果的意义与存在的问题。文中着重论述了分散、鲁棒、容错控制研究方法的发展途径。 相似文献
7.
No authorship indicated 《Canadian Metallurgical Quarterly》2003,58(11):931
Provides the biography of David W. Johnson and announces that he has won the Award for Distinguished Contributions of Applications of Psychology to Education and Training for programmatic research, comprehensive research reviews, and revision of theory over four decades of persistence that have provided the knowledge foundation for cooperative learning, constructive controversy, conflict resolution, and peer mediation training. A selected bibliography is also provided. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
8.
反拍卖采购:一种新的采购模式 总被引:6,自引:0,他引:6
反拍卖采购技术以其新的理念和对信息技术的融合,能够使企业采购成本大幅度降低。通过对我国传统采购模式与反拍卖采购模式的对比分析,可以了解到反拍卖采购技术的应用前景。 相似文献
9.
New technologies such as power electronics have made it possible to change continuously the impedance of a power system not only to control power flow but also to enhance stability. A power system incorporating a variable impedance apparatus such as a variable series capacitor (VSrC) and high-speed phase shifter (HSPS) is called VIPS (Variable Impedance Power System) by the authors. This paper proposes a novel control method of VIPS apparatus such as VSrC and HSPS installed at an interconnecting point for stabilizing inter-area unstable and/or oscillatory modes. The proposed design method of the control system is a kind of hierarchical decentralized control method of a large-scale power system based on a Lyapunov function. Under the proposed control scheme, each subsystem can be stabilized independently by local controllers such as AVR, speed governor and PSS, and then the whole interconnected system can be stabilized by VIPS apparatus taking into account interactions between subsystems. The effectiveness and robustness of the VIPS apparatus control are shown by numerical examples with model systems including a large-scale power system. 相似文献
10.
为了适应电力工业发展和国家新兴产业政策的需要,本文扼要介绍了21世纪新建电厂在热控系统的规划设计方面应做的改进和注意的问题.并在此基础上阐述了一些个人的观点和看法供管理、设计和技术人员参考. 相似文献