全文获取类型
收费全文 | 77859篇 |
免费 | 11813篇 |
国内免费 | 8763篇 |
专业分类
化学 | 53830篇 |
晶体学 | 881篇 |
力学 | 5105篇 |
综合类 | 657篇 |
数学 | 9496篇 |
物理学 | 28466篇 |
出版年
2024年 | 80篇 |
2023年 | 1558篇 |
2022年 | 1707篇 |
2021年 | 2413篇 |
2020年 | 2971篇 |
2019年 | 2922篇 |
2018年 | 2579篇 |
2017年 | 2343篇 |
2016年 | 3393篇 |
2015年 | 3503篇 |
2014年 | 4173篇 |
2013年 | 5543篇 |
2012年 | 6719篇 |
2011年 | 6912篇 |
2010年 | 4861篇 |
2009年 | 4732篇 |
2008年 | 4943篇 |
2007年 | 4387篇 |
2006年 | 4193篇 |
2005年 | 3673篇 |
2004年 | 2958篇 |
2003年 | 2314篇 |
2002年 | 2060篇 |
2001年 | 1879篇 |
2000年 | 1608篇 |
1999年 | 1694篇 |
1998年 | 1415篇 |
1997年 | 1197篇 |
1996年 | 1273篇 |
1995年 | 1135篇 |
1994年 | 1080篇 |
1993年 | 936篇 |
1992年 | 809篇 |
1991年 | 727篇 |
1990年 | 586篇 |
1989年 | 510篇 |
1988年 | 382篇 |
1987年 | 359篇 |
1986年 | 314篇 |
1985年 | 313篇 |
1984年 | 208篇 |
1983年 | 183篇 |
1982年 | 146篇 |
1981年 | 112篇 |
1980年 | 84篇 |
1978年 | 56篇 |
1977年 | 52篇 |
1976年 | 50篇 |
1975年 | 57篇 |
1973年 | 57篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
Zhengcheng Wang Shangyan Zhou Wei Liao Qian Zhou Meida Chen Jin Long Prof. Qingmei Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(66):e202201987
The designs of efficient and inexpensive Pt-based catalysts for methanol oxidation reaction (MOR) are essential to boost the commercialization of direct methanol fuel cells. Here, the highly catalytic performance PtFe alloys supported on multiwalled carbon nanotubes (MWCNTs) decorating nitrogen-doped carbon (NC) have been successfully prepared via co-engineering of the surface composition and electronic structure. The Pt1Fe3@NC/MWCNTs catalyst with moderate Fe3+ feeding content (0.86 mA/mgPt) exhibits 2.26-fold enhancement in MOR mass activity compared to pristine Pt/C catalyst (0.38 mA/mgPt). Furthermore, the CO oxidation initial potential of Pt1Fe3@NC/MWCNTs catalyst is lower relative to Pt/C catalyst (0.71 V and 0.80 V). Benefited from the optimal surface compositions, the anti-corrosion ability of MWCNT, strong electron interaction between PtFe alloys and MWCNTs and the N-doped carbon (NC) layer, the Pt1Fe3@NC/MWCNTs catalyst presents an improved MOR performance and anti-CO poisoning ability. This study would open up new perspective for designing efficient electrocatalysts for the DMFCs field. 相似文献
62.
Meihua Shen Dr. Xinpeng Zhao Dr. Lu Han Nanxi Jin Prof. Song Liu Prof. Tao Jia Prof. Zhijun Chen Prof. Xiuhua Zhao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(20):e202104137
Solar-driven interfacial vaporization by localizing solar-thermal energy conversion to the air−water interface has attracted tremendous attention. In the process of converting solar energy into heat energy, photothermal materials play an essential role. Herein, a flexible solar-thermal material di-cyan substituted 5,12-dibutylquinacridone (DCN−4CQA)@Paper was developed by coating photothermal quinacridone derivatives on the cellulose paper. The DCN−4CQA@Paper combines desired chemical and physical properties, broadband light-absorbing, and shape-conforming abilities that render efficient photothermic vaporization. Notably, synergetic coupling of solar-steam and solar-electricity technologies by integrating DCN−4CQA@Paper and the thermoelectric devices is realized without trade-offs, highlighting the practical consideration toward more impactful solar heat exploitation. Such solar distillation and low-grade heat-to-electricity generation functions can provide potential opportunities for fresh water and electricity supply in off-grid or remote areas. 相似文献
63.
Emerging Trends in Fluorescence Bioimaging of Divalent Metal Cations Using Small-Molecule Indicators
Mingqiao Liu Junwei Zhang Zhixing Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(45):e202200587
Visualization of cation dynamics inside a living system represent a major breakthrough at the crossroad of chemistry and cellular physiology. Since the inception of BAPTA-based cellular calcium indicators in the 1980s, generations of chemical and genetically encoded ion indicators spanning the visible spectrum have been developed. In this article, we bring up three emerging concepts in this field: 1. red-shifting cation indicators towards far-red and near-infrared (NIR) channels; 2. directing the indicators to various subcellular localizations; 3. lowering the phototoxicity of indicators for long term recording. These initiatives collectively echo the advocate of 4D cellular physiology, where biological processes within living systems can be panoramically unveiled under 3D, long-term, and multi-channel imaging with unprecedented spatial and temporal resolution. This outlook poses exciting challenges and opportunities for chemists to upgrade the toolkit of fluorescent indicators as key enablers for a new era of imageomics. 相似文献
64.
65.
Nonlinear Dynamics - The perovskite solar cell (PSC) is one of the most promising photovoltaic candidates along with the highly increasing demand for green electricity. One of the main concerns... 相似文献
66.
67.
根据教育部颁布的《普通高中物理课程标准(2017年版)》,在上海市物理教育教学基地(上海高校“立德树人”人文社会科学重点研究基地)的大力支持下,由上海市教育委员会组织编写的上海高中物理非统编教材进行了正式使用前的试教试用活动,此教材是在上海高中物理“二期课改”教材的基础上全面改写而成的.单元教学设计已成为当前教学设计的焦点问题,以《物理·必修》(第三册)静电场单元为例,详细阐述了“教学问题链”的设计理念,希望与广大一线教师交流试教试用的心得与反思,推动新课改课堂转型. 相似文献
68.
Acoustical Physics - In order to suppress the vibration and noise in the middle and low frequency band of the wheel-driven bus, this paper explores the application of the locally resonant phononic... 相似文献
69.
This paper investigates the effect of phosphorus (P) on char structure and reactivity of char prepared from the fast pyrolysis of purposely-prepared P-loaded biomass samples at 1000 °C in absence of other inorganic species. Biomass was first acid-washed then loaded with P of three different occurrence forms (one organic P i.e. phytic acid, and two inorganic P i.e. orthophosphoric acid and polyphosphoric acid) at the same P content of 0.8 wt%. Experimental results show that both organic and inorganic P substantially increase char yields during pyrolysis from 6.2% for the biomass sample without P to 23.0–26.0% for P-loaded samples due to the enhanced crosslinking by P-containing structures in char, leading to increases in the char C and H contents and decrease in O content. The presence of P in biochars from fast pyrolysis of various P-loaded biomass samples plays important role in the evolution of char structure and intrinsic reactivity measured during low-temperature oxidation at 500 °C in air under chemical-reaction-controlled regime. After pyrolysis and subsequent char oxidation, all P in biomass either as organic or inorganic P are found to be present in forms of acid-insoluble organic structures. For char prepared from acid-washed wood, char reactivity increases with char conversion due to the increasing pore surface area at higher conversion. Comparatively, for char prepared from acid-washed wood loaded with various P at char conversion below 60%, the presence of P increases char intrinsic reactivity due to the enhanced crosslinking of reactive carbon structures and reduced condensation of char structures. However, at conversions above 60%, P-containing species in char lead to a significant decrease in char reactivity, due to the formation of abundant CO-P bonds, that is highly resistant to the oxidation in air, in the reacting chars. 相似文献
70.
Journal of Fluorescence - Carbon nanodots (CDs) have exhibited excellent sensing capability for various metal ions. However, it is difficult to determine the selectivity of CDs to metal ions. In... 相似文献