全文获取类型
收费全文 | 5839篇 |
免费 | 1094篇 |
国内免费 | 797篇 |
专业分类
化学 | 4360篇 |
晶体学 | 102篇 |
力学 | 364篇 |
综合类 | 44篇 |
数学 | 693篇 |
物理学 | 2167篇 |
出版年
2024年 | 18篇 |
2023年 | 133篇 |
2022年 | 239篇 |
2021年 | 242篇 |
2020年 | 332篇 |
2019年 | 294篇 |
2018年 | 264篇 |
2017年 | 279篇 |
2016年 | 342篇 |
2015年 | 372篇 |
2014年 | 341篇 |
2013年 | 480篇 |
2012年 | 545篇 |
2011年 | 537篇 |
2010年 | 395篇 |
2009年 | 374篇 |
2008年 | 387篇 |
2007年 | 319篇 |
2006年 | 307篇 |
2005年 | 261篇 |
2004年 | 215篇 |
2003年 | 150篇 |
2002年 | 159篇 |
2001年 | 110篇 |
2000年 | 110篇 |
1999年 | 98篇 |
1998年 | 39篇 |
1997年 | 46篇 |
1996年 | 39篇 |
1995年 | 34篇 |
1994年 | 12篇 |
1993年 | 29篇 |
1992年 | 23篇 |
1991年 | 16篇 |
1990年 | 12篇 |
1989年 | 10篇 |
1988年 | 19篇 |
1986年 | 15篇 |
1985年 | 16篇 |
1984年 | 14篇 |
1983年 | 6篇 |
1982年 | 13篇 |
1980年 | 6篇 |
1979年 | 11篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1975年 | 7篇 |
1974年 | 5篇 |
1973年 | 5篇 |
排序方式: 共有7730条查询结果,搜索用时 15 毫秒
161.
Jin Kai Li Baowei Wang Kaixing Luo Huijuan Gong Zhijun Wu Wenfei 《Research on Chemical Intermediates》2018,44(11):6933-6943
Research on Chemical Intermediates - A rare-earth concentrate obtained from Bayan Obo tailings was used as catalyst for low-temperature selective catalytic reduction (SCR) of NOx. X-ray powder... 相似文献
162.
Mingli Jiao Kai Yang Wangxi Zhang Wei Pan Ruiwen Zhang Si Xie 《Journal of Macromolecular Science: Physics》2013,52(11):2103-2115
A series of poly(L-lactic acid)/polybutadiene (PLA/PB) biodegradable multiblock elastomers was synthesized and characterized. A two-step process to prepare PLA/PB multiblock elastomers was applied. Melt polymerization was used to prepare poly(L-lactic acid) (PLA) terminated with hydroxyl groups and, at the same time, hydroxyl-terminated polybutadiene (HTPB) and 1,6-hexamethylene diisocyanate (HDI) were employed to synthesize diisocyanate-terminated polybutadiene (ITPB). Then, PLA and ITPB were reacted with different PLA/PB weight ratios. Consequently, a series of PLA/PB biodegradable poly(ester-urethane)s with crosslinked chains was obtained. Swelling characteristics and crosslink density of the crosslinked elastomer were investigated. DMA was applied to characterize its thermal properties. The measurement of mechanical properties showed that a PLA/PB elastomer with adjustable mechanical properties was synthesized. Micromorphology, hydrophobicity, and degradability of the material were also characterized. 相似文献
163.
Isotactic polypropylene (PP) composites filled with hydroxyapatite nanorods (nHAs) were fabricated using a melt compounding process. The effects of nHA additions on the structure, thermal, and mechanical properties as well as bioactivity of PP were investigated. Wide-angle X-ray diffraction and differential scanning calorimetry results showed that PP crystallized exclusively in the α-form when adding nHAs. Dynamic mechanical analysis showed that nHAs enhanced the storage modulus of PP. Mechanical measurements showed that nHAs stiffened and reinforced PP but reduced its tensile ductility and impact strength considerably. Furthermore, the PP/nHA nanocomposites were found to exhibit excellent bioactivity upon immersion in a simulated body fluid solution. This was attributed to the formation of apatite mineral crystals on the nanocomposite surfaces as revealed by scanning electron microscopy and energy dispersive X-ray analysis. 相似文献
164.
165.
Binglu Zhao Luxiang Ma Kai Wu Mengxiong Cao Minggui Xu Xinxiang Zhang Wen Liu Jitao Chen 《中国化学快报》2021,32(1):125-131
All-solid-state Li metal battery has been regarded as a promising battery technology due to its high energy density based on the high capacity of lithium metal anode and high safety based on the all solid state electrolyte without inflammable solvent.However,challenges still exist mainly in the poor contact and unstable interface between electrolyte and electrodes.Herein,we demonstrate an asymmetric design of the composite polymer electrolyte with two different layers to overcome the interface issues at both the cathode and the anode side simultaneously.At the cathode side,the polypropylene carbonate layer has enough viscosity and flexibility to reduce the inter-facial resistance,while at the Li anode side,the polyethylene oxide layer modified with hexagonal boron nitride has high mechanical strength to suppress the Li dendrite growth.Owing to the synergetic effect between different components,the asprepared double layer composite polymer electrolyte demonstrates a large electrochemical window of5.17 V,a high ionic conductivity of 6.1×10~(-4) S/cm,and a transfe rence number of 0.56,featuring excellent ion transport kinetics and good chemical stability.All-solid-state Li metal battery assembled with LiFePO_4 cathode and Li anode delivers a high capacity of 150.9 mAh/g at 25℃ and 0.1 C-rate,showing great potential for practical applications. 相似文献
166.
Using the so-called martingale difference correlation (MDC), we propose a novel censored-conditional-quantile screening approach for ultrahigh-dimensional survival data with heterogeneity (which is often present in such data). By incorporating a weighting scheme, this method is a natural extension of MDC-based conditional quantile screening, as considered in Shao and Zhang (2014), to handle ultrahigh-dimensional survival data. The proposed screening procedure has a sure-screening property under certain technical conditions and an excellent capability of detecting the nonlinear relationship between independent and censored dependent variables. Both simulation results and an analysis of real data demonstrate the effectiveness of the new censored conditional quantile-screening procedure. 相似文献
167.
Dr. Marko Förstel Kai Pollow Taarna Studemund Prof. Dr. Otto Dopfer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(61):15075-15080
Au2+ is a simple but crucial model system for understanding the diverse catalytic activity of gold. While the Au2+ ground state (X2Σg+) is understood reasonably well from mass spectrometry and computations, no spectroscopic information is available for its first excited state (A2Σu+). Herein, we present the vibrationally resolved electronic spectrum of this state for cold Ar-tagged Au2+ cations. This exceptionally low-lying and well isolated A2Σ(u)+←X2Σ(g)+ transition occurs in the near-infrared range. The observed band origin (5738 cm−1, 1742.9 nm, 0.711 eV) and harmonic Au−Au and Au−Ar stretch frequencies (201 and 133 cm−1) agree surprisingly well with those predicted by standard time-dependent density functional theory calculations. The linearly bonded Ar tag has little impact on either the geometric or electronic structure of Au2+, because the Au2+⋅⋅⋅Ar bond (∼0.4 eV) is much weaker than the Au−Au bond (∼2 eV). As a result of 6 s←5d excitation of an electron from the antibonding σu* orbital (HOMO-1) into the bonding σg orbital (SOMO), the Au−Au bond contracts substantially (by 0.1 Å). 相似文献
168.
Bo Wang Limin Qiu Kai Wang Daming Sun Xuejun Zhang Weijuan Yang Junhu Zhou 《Applied Acoustics》2012,73(5):508-513
A Helmholtz resonator can be used as a transmission part to connect the thermoacoustic engine (TE) with its load. However, the resonator can significantly influence the performance of the TE. In order to investigate the impact of a Helmholtz resonator on the onset process of a TE, infrared (IR) imaging is firstly used as a visualization method to characterize the onset mechanism. The influence of dimensions of the Helmholtz resonator on the onset process are analyzed experimentally and theoretically. Results show that the Helmholtz resonator reduces the pressure amplitude at the onset moment and increases the onset temperature of the TE, both of which depend on the acoustic power absorbed from the TE. Onset without a sudden increase of pressure amplitude is observed with the Helmholtz resonator at resonance length. This paper shows that IR imaging is an effective way to characterize the temperature distribution in a TE study. 相似文献
169.
170.
Suppression of the Charge Density Wave State in Two-Dimensional 1T-TiSe2 by Atmospheric Oxidation
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Lifei Sun Chuanhui Chen Dr. Qinghua Zhang Christian Sohrt Tianqi Zhao Dr. Guanchen Xu Jinghui Wang Prof. Dong Wang Prof. Kai Rossnagel Prof. Lin Gu Prof. Chenggang Tao Prof. Liying Jiao 《Angewandte Chemie (International ed. in English)》2017,56(31):8981-8985
Two-dimensional (2D) metallic transition-metal dichalcogenides (TMDCs), such as 1T-TiSe2, have recently emerged as unique platforms for exploring their exciting properties of superconductivity and the charge density wave (CDW). 2D 1T-TiSe2 undergoes rapid oxidation under ambient conditions, significantly affecting its CDW phase-transition behavior. We comprehensively investigate the oxidation process of 2D TiSe2 by tracking the evolution of the chemical composition and atomic structure with various microscopic and spectroscopic techniques and reveal its unique selenium-assisting oxidation mechanism. Our findings facilitate a better understanding of the chemistry of ultrathin TMDCs crystals, introduce an effective method to passivate their surfaces with capping layers, and thus open a way to further explore the functionality of these materials toward devices. 相似文献