全文获取类型
收费全文 | 8261篇 |
免费 | 833篇 |
国内免费 | 1270篇 |
专业分类
化学 | 4999篇 |
晶体学 | 42篇 |
力学 | 379篇 |
综合类 | 25篇 |
数学 | 1392篇 |
物理学 | 3527篇 |
出版年
2024年 | 7篇 |
2023年 | 198篇 |
2022年 | 232篇 |
2021年 | 244篇 |
2020年 | 287篇 |
2019年 | 228篇 |
2018年 | 215篇 |
2017年 | 299篇 |
2016年 | 337篇 |
2015年 | 296篇 |
2014年 | 418篇 |
2013年 | 564篇 |
2012年 | 507篇 |
2011年 | 765篇 |
2010年 | 644篇 |
2009年 | 910篇 |
2008年 | 748篇 |
2007年 | 749篇 |
2006年 | 541篇 |
2005年 | 386篇 |
2004年 | 327篇 |
2003年 | 273篇 |
2002年 | 155篇 |
2001年 | 150篇 |
2000年 | 103篇 |
1999年 | 95篇 |
1998年 | 106篇 |
1997年 | 117篇 |
1996年 | 76篇 |
1995年 | 66篇 |
1994年 | 44篇 |
1993年 | 46篇 |
1992年 | 44篇 |
1991年 | 32篇 |
1990年 | 24篇 |
1989年 | 28篇 |
1988年 | 21篇 |
1987年 | 10篇 |
1986年 | 15篇 |
1985年 | 16篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Dr. Tao Yuan Ziwei Wu Senmao Zhai Rong Wang Shiwen Wu Prof. Jiajia Cheng Prof. Meifang Zheng Prof. Xinchen Wang 《Angewandte Chemie (International ed. in English)》2023,62(27):e202304861
Light-driven fixation of CO2 in organics has emerged as an appealing alternative for the synthesis of value-added fine chemicals. Challenges remain in the transformation of CO2 as well as product selectivity due to its thermodynamic stability and kinetic inertness. Here we develop a boron carbonitride (BCN) with the abundant terminal B/N defects around the mesoporous walls, which essentially enhances surface active sites as well as charge transfer kinetics, boosting the overall rate of CO2 adsorption and activation. In this protocol, anti-Markovnikov hydrocarboxylation of alkenes with CO2 to an extended carbon chain is achieved with good functional group tolerance and specific regioselectivity under visible-light irradiation. The mechanistic studies demonstrate the formation of CO2 radical anion intermediate on defective boron carbonitride, leading to the anti-Markovnikov carboxylation. Gram-scale reaction, late-stage carboxylation of natural products and synthesis of anti-diabetic GPR40 agonists reveal the utility of this method. This study sheds new insight on the design and application of metal-free semiconductors for the conversion of CO2 in an atom-economic and sustainable manner. 相似文献
62.
Liangxu Lin Liang Huang Chang Wu Yu Gao Naihua Miao Chao Wu Aaron T. Marshall Yi Zhao Jiazhao Wang Jun Chen Shixue Dou Gordon G. Wallace Wei Huang 《Angewandte Chemie (International ed. in English)》2023,62(49):e202315182
The exploration of inexpensive and efficient catalysts for oxygen reduction reaction (ORR) is crucial for chemical and energy industries. Carbon materials have been proved promising with different catalysts enabling 2 and 4e− ORR. Nevertheless, their ORR activity and selectivity is still complex and under debate in many cases. Many structures of these active carbon materials are also chemically unstable for practical implementations. Unlike the well-discussed structures, this work presents a strategy to promote efficient and stable 2e− ORR of carbon materials through the synergistic effect of lattice distortion and H-passivation (on the distorted structure). We show how these structures can be formed on carbon cloth, and how the reproducible chemical adsorption can be realized on these structures for efficient and stable H2O2 production. The work here gives not only new understandings on the 2e− ORR catalysis, but also the robust catalyst which can be directly used in industry. 相似文献
63.
Francesco Mattarozzi Marisol Tapia Rosales Rim C. J. van de Poll Prof. Dr. Emiel J. M. Hensen Dr. Peter Ngene Prof. Dr. Petra E. de Jongh 《欧洲无机化学杂志》2023,26(28):e202300152
The electrochemical reduction of CO2 to produce sustainable fuels and chemicals has attracted great attention in recent years. It is shown that surface-modified carbons catalyze the CO2RR. This study reports a strategy to modify the surface of commercially available carbon materials by adding oxygen and nitrogen surface groups without modifying its graphitic structure. Clear differences in CO2RR activity, selectivity and the turnover frequency between the surface-modified carbons were observed, and these differences were ascribed to the nature of the surface groups chemistry and the point of zero charge (PZC). The results show that nitrogen-containing surface groups are highly selective towards the formation of CO from the electroreduction of CO2 in comparison with the oxygen-containing surface groups, and the carbon without surface groups. This demonstrates that the selectivity of carbon for CO2RR can be rationally tuned by simply altering the surface chemistry via surface functionalization. 相似文献
64.
《Arabian Journal of Chemistry》2023,16(4):104576
Multi-color is the fundamental for display, white LED (WLED), and bioimaging. Three kinds of carbon dots (co-doped of S and N elements) (S,N-CDs) with red (R), green (G) and blue (B) fluorescence were synthesized using 2,5-Diaminobenzenesulfonicacid as the only precursor by a simple, environmentally friendly solvent modulation method, which neither needed complex precursor formulations nor tedious post-processes to obtain multi-color performance. Compared to the previous S,N-CDs, our CDs has a higher fluorescence quantum yield and tunable colors which implies a higher resolution in detection and deeper penetration in tissue observation. We present their outstanding roles in chemical trace detection and light source application to demonstrate their application potential. The three CDs were highly sensitive and could selectively recognize Ag+ and Fe3+ with low limit of detection of up to 35 and 23 nM, respectively. The CDs were mixed to fabricate WLED in solution, solid (with lotus root powder) and xerogel forms, achieved satisfactory white light properties with CIE (1931) coordinates (0.32,0.33), (0.31, 0.32) and (0.33, 0.35), respectively, almost pure white light. This is digestible light source and fluorescent biomarker that open up possibilities for in vivo recycling-free imaging applications. 相似文献
65.
《Arabian Journal of Chemistry》2023,16(4):104568
A bio-catalyst made of natural resources, such as Carica papaya latex, is very challenging for nanoparticle separation. In addition, differences in thermal conditions between nanoparticles affect the movement of substances in the separation process. The study experimentally investigated the role of Carica papaya latex bio-catalyst and thermal shock in water on synthesizing rice husk (RH). The synthesis retained the Mg and C elements attached to SiO2, which were generally neglected during the process. The study's objective was to evaluate the effectiveness of biocatalysts and thermal effects on the separation of Mg-SiO2-C from rice husk carbon nanoparticles (CNPs-RH). The research involved various treatment processes, such as RH pyrolysis in obtaining charcoal, High energy milling (HEM) to have carbon particles, and washing to get nano-sized carbon particles. The bonding of elemental compounds to rice husk carbon particles (CPs-RH) was released using NaOH and coagulation using a bio-catalyst. Coagulated CPs-RH was injected into water at a temperature of 60–70 °C to have a thermal shock effect for H2O clusters in Na+ and Mg2+ ions attached to the surface of the nanoparticles. Several tests were carried out, such as the SEM-EDX, TEM, XRD, and FTIR tests, to investigate the two nanoparticle clusters formed up to the nanometer scale. The results indicated that CNPs-RH nanoparticles consist of spherical particles with a diameter of 1.2 nm, while Mg-SiO2-C nanoparticles have a diameter of 0.6 nm. Both are classified as amorphous. Based on the FTIR test, CNPs-RH is hydrophilic, while Mg-SiO2-C is hydrophobic. Thermal shock in water strengthens the ion's mobility, increasing the interfacial dipole forces between nanoparticles and accelerating the separation process. 相似文献
66.
《Arabian Journal of Chemistry》2023,16(5):104670
As an indispensable part of cement slurry for high temperature and high pressure oil and gas wells, weighting materials have a significant impact on the carbon dioxide corrosion of oil well cement-based composites.This paper studied the carbonation process of cement with three weighting agents, and evaluated the compressive strength and carbonation depth of cement at 150 ℃. XRD, SEM and MIP were used to study the carbonation mechanism of cement. When 21 days of carbonation, the carbonation depth growth rate of hausmannite cement was 0.21 mm/d, hematite cement was 0.24 mm/d, and barite cement was 0.31 mm/d. The compressive strength of cement decreased after carbonation,and the carbonation had a minor influence on the compressive strength of hausmannite cement and the most significant impact on barite cement. The carbonation product of oil well cement was mainly calcite. Unstable vaterite mainly existed in the barite cement sample, indicating that the barite cement sample was the most serious corrosion. In the carbonation zone, the number of pores smaller than 10 nm increased the most in the hausmannite cement sample. Pores with a diameter greater than 100 nm accounted for 1.9 % in the hausmannite cement, 3.0 % in hematite cement, and 4.8 % in barite cement. The result shows that hausmannite is the most conducive to the corrosion resistance of oil well cement. 相似文献
67.
《Arabian Journal of Chemistry》2023,16(5):104682
The study of the inclined flow along with the heterogeneous/homogeneous reactions in the fluid has been widely used in many industrial and engineering applications, such as petrochemical, pharmaceutical, materials science, heat exchanger design, fluid flow through porous media, etc. The purpose of this study is to present an infinite shear rate viscosity model using the inclined Carreau fluid with nanoscale heat transport. The model considers the effect of inclined angle on the fluid’s viscosity and the transfer of heat at the nanoscale. The result shows that the viscosity of the fluid decreases by increasing the inclination angle and the coefficient of heat transfer also increases with the inclination. The model can be used to predict the viscosity and heat transfer fluid’s behavior in the inclined systems that is widely used in the industrial and engineering applications. The results provide a better understanding of the inclined flow behavior of fluids and the heat transfer at the nanoscale, which can be useful in heat exchanger design, fluid flow through porous media, etc. Greater Infinite shear rate viscosity parameter gives the higher magnitude of Carreau fluid velocity. Moreover, inclined magnetic field reduces the velocity due to Lorentz force. Two numerical schemes are used to solve the model, BVP4C and Shooting. 相似文献
68.
Xiaotong Fan Dr. Kai Huang Prof. Long Chen Haipeng You Menglei Yao Prof. Hao Jiang Prof. Ling Zhang Prof. Cheng Lian Dr. Xiangwen Gao Prof. Chunzhong Li 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(2):e202215342
Supercapacitor represents an important electrical energy storage technology with high-power performance and superior cyclability. However, currently commercialized supercapacitors still suffer limited energy densities. Here we report an unprecedentedly respiring supercapacitor with chlorine gas iteratively re-inspires in porous carbon materials, that improves the energy density by orders of magnitude. Both electrochemical results and theoretical calculations show that porous carbon with pore size around 3 nm delivers the best chlorine evolution and adsorption performance. The respiring supercapacitor with multi-wall carbon nanotube as the cathode and NaTi2(PO4)3 as the anode can store specific energy of 33 Wh kg−1 with negligible capacity loss over 30 000 cycles. The energy density can be further improved to 53 Wh kg−1 by replacing NaTi2(PO4)3 with zinc anode. Furthermore, thanks to the extraordinary reaction kinetics of chlorine gas, this respiring supercapacitor performs an extremely high-power density of 50 000 W kg−1. 相似文献
69.
70.
Haodong Nie Kaiqiang Wei Yi Li Yan Liu Yajie Zhao Hui Huang Mingwang Shao Yang Liu Zhenhui Kang 《中国化学快报》2021,32(7):2283-2286
Overall water photo-splitting is a prospective ideal pathway to produce ultra-clean H_2 energy by semiconductors.However,the band structure of many semiconductors cannot satisfy the requirement of H_2 and O_2 production at the same time.Herein,we illustrate that carbon dots(CDs)/Bi_2 WO_6 photocatalyst with compensatory photo-electronic effect has enhanced activity for overall water photo-splitting without any sacrificial agent.In this complex photocatalytic system,the photo-potential provided by CDs makes the CDs/Bi_2 WO6(C-BWO) composite could satisfy the band structure conditions for overall water photo-splitting.The C-BWO composite(3 wt% CDs content) exhibits optimized hydrogen evolution(oxygen evolution) of 0.28 μmol/h(0.12 μmol/h) with an approximate 2:1(H_2:O_2) stoichiometry at normal pressure.We further employed the in-situ transient photovoltage(TPV) technique to study the photoelectron extraction and the interface charge transfer kinetics of this composite catalyst. 相似文献