全文获取类型
收费全文 | 6572篇 |
免费 | 1199篇 |
国内免费 | 938篇 |
专业分类
电工技术 | 230篇 |
技术理论 | 1篇 |
综合类 | 109篇 |
化学工业 | 1171篇 |
金属工艺 | 239篇 |
机械仪表 | 189篇 |
建筑科学 | 98篇 |
矿业工程 | 7篇 |
能源动力 | 398篇 |
轻工业 | 187篇 |
水利工程 | 63篇 |
石油天然气 | 47篇 |
武器工业 | 8篇 |
无线电 | 1713篇 |
一般工业技术 | 1366篇 |
冶金工业 | 52篇 |
原子能技术 | 211篇 |
自动化技术 | 2620篇 |
出版年
2024年 | 19篇 |
2023年 | 243篇 |
2022年 | 205篇 |
2021年 | 283篇 |
2020年 | 289篇 |
2019年 | 160篇 |
2018年 | 202篇 |
2017年 | 304篇 |
2016年 | 333篇 |
2015年 | 307篇 |
2014年 | 435篇 |
2013年 | 441篇 |
2012年 | 628篇 |
2011年 | 769篇 |
2010年 | 544篇 |
2009年 | 691篇 |
2008年 | 514篇 |
2007年 | 576篇 |
2006年 | 508篇 |
2005年 | 212篇 |
2004年 | 106篇 |
2003年 | 86篇 |
2002年 | 101篇 |
2001年 | 110篇 |
2000年 | 88篇 |
1999年 | 99篇 |
1998年 | 69篇 |
1997年 | 65篇 |
1996年 | 54篇 |
1995年 | 32篇 |
1994年 | 29篇 |
1993年 | 22篇 |
1992年 | 20篇 |
1991年 | 29篇 |
1990年 | 38篇 |
1989年 | 28篇 |
1988年 | 14篇 |
1987年 | 16篇 |
1986年 | 12篇 |
1985年 | 8篇 |
1984年 | 9篇 |
1983年 | 1篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1959年 | 3篇 |
排序方式: 共有8709条查询结果,搜索用时 406 毫秒
1.
2.
Magnetic Resonance Materials in Physics, Biology and Medicine - To investigate the value of using diffusion-weighted imaging (DWI) and intravoxel incoherent motion DWI (IVIM-DWI) to assess the... 相似文献
3.
4.
《Journal of the European Ceramic Society》2020,40(10):3577-3584
In this work, the grain boundaries composition of the polycrystalline CaCu3Ti4O12 (CCTO) was investigated. A Focused Ion Beam (FIB)/lift-out technique was used to prepare site-specific thin samples of the grain boundaries interface of CCTO ceramics. Scanning transmission electron microscopy (STEM) coupled with energy dispersive X-ray spectrometry (EDXS) and Electron Energy Loss Spectroscopy (EELS) systems were used to characterize the composition and nanostructure of the grain and grain boundaries region. It is known that during conventional sintering, discontinuous grain growth occurs and a Cu-rich phase appears at grain boundaries. This Cu-rich phase may affect the final dielectric properties of CCTO but its structure and chemical composition remained unknown. For the first time, this high-resolution FIB-TEM-STEM study of CCTO interfacial region highlights the composition of the phases segregated at grain boundaries namely CuO, Cu2O and the metastable phase Cu3TiO4. 相似文献
5.
6.
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
7.
This article theoretically and empirically analyzes backtesting portfolio value-at-risk (VaR) with estimation risk in an intrinsically multi-variate framework. It particularly takes into account the estimation of portfolio weights in forecasting portfolio VaR and its impact on backtesting. It shows that the estimation risk from estimating portfolio weights and that from estimating the multi-variate dynamic model make the existing methods in a univariate framework inapplicable. It proposes a general theory to quantify estimation risk applicable to the present problem and suggests practitioners a simple but effective way to implement valid inference to overcome the effect of estimation risk in backtesting portfolio VaR. In particular, we apply our theory to the efficient mean-variance-skewness portfolio for a multi-variate generalized autoregressive conditional heteroscedasticity model with multi-variate general hyperbolic distributed innovations. Some Monte Carlo simulations and an empirical application demonstrate the merits of our method. 相似文献
8.
Bin Zhang Meng Zhang Yu Li Huansheng Cheng Jianming Zheng 《Ceramics International》2019,45(3):3081-3087
Proton induced X-ray emission (PIXE) technique and factor analysis were used to study the recovery of making-technology of Chinese Longquan celadon made in the late Southern Song Dynasty (1127–1279 CE). Based on factor analysis, for the raw material for body and the recipe for glaze, there is a close but slightly different relationship between these Longquan celadons unearthed from the core area of Dayao and the non-core area, despite all the Longquan celadons belong to the high-calcium-glaze system. The chemical compositions of most of the tentative body and glaze samples are very close to those of Longquan celadons unearthed from the core area of Dayao and the non-core area. This study can provide a guidance for recovery of making-technology of Longquan celandon. 相似文献
9.
Jianhuai Dong Zhixuan Dong 《International Journal of Adaptive Control and Signal Processing》2020,34(10):1466-1482
This article studies the optimal filtering and control for wireless networked control systems (WNCSs). In WNCSs, packets may be lost in both control and feedback channels and user datagram protocol is usually used to improve the performance of the real-time control. Relevant literature indicates that the conventional optimal filtering for such a system cannot be applied in practice due to the complex calculation with Gaussian mixtures. This paper proposes a novel scheme to realize the optimal filtering and the linear quadratic Gaussian control for WNCSs, in which the controlled node performs a local estimation and the remote-control node performs the final estimation and control, and a synchronization of two estimators is guaranteed by a communication mechanism. An optimal filtering algorithm is developed, the stability condition of the filtering error covariance is obtained, optimal finite-horizon and infinite-horizon control are derived, and the stability of the closed-loop control system is proved. Numerical simulations show the validity and feasibility of the theoretical results. 相似文献
10.
Yuanfang Tao Xin Ji Dr. Jian Zhang Yue Jin Nannan Wang Prof. Yubing Si Prof. Weili Zhao 《Chembiochem : a European journal of chemical biology》2020,21(21):3131-3136
Near-infrared (NIR) fluorescent probes are very significant for detecting cysteine in biological systems. Herein, we report a highly selective and sensitive NIR turn-on fluorescent probe (BDP-NIR) based on BODIPY with large Stokes shift (105 nm) for detecting Cys. We clarified the sensing mechanism based on the different thiol-induced SNAr substitution/rearrangement reaction of the probe with cysteine and homocysteine/glutathione, which leads to the corresponding amino- and thiol-BODIPY dyes with distinct photophysical properties. Moreover, a novel mechanism of fluorescence quenching was demonstrated by density functional theory calculation. The reason for the fluorescence quenching of the probe might be intersystem crossing (from singlet to triplet excited state). Moreover, BDP-NIR had a high linear dynamic range of 0–500 μM, which was promising for detecting cysteine quantificationally. Significantly, BDP-NIR was capable of sensing endogenous cysteine in living cells and in vivo. 相似文献