全文获取类型
收费全文 | 1865篇 |
免费 | 37篇 |
国内免费 | 10篇 |
专业分类
化学 | 1325篇 |
晶体学 | 18篇 |
力学 | 43篇 |
数学 | 199篇 |
物理学 | 327篇 |
出版年
2022年 | 11篇 |
2021年 | 26篇 |
2020年 | 21篇 |
2019年 | 24篇 |
2018年 | 19篇 |
2017年 | 13篇 |
2016年 | 47篇 |
2015年 | 32篇 |
2014年 | 29篇 |
2013年 | 80篇 |
2012年 | 83篇 |
2011年 | 119篇 |
2010年 | 57篇 |
2009年 | 55篇 |
2008年 | 98篇 |
2007年 | 96篇 |
2006年 | 109篇 |
2005年 | 76篇 |
2004年 | 79篇 |
2003年 | 69篇 |
2002年 | 59篇 |
2001年 | 31篇 |
2000年 | 30篇 |
1999年 | 9篇 |
1998年 | 17篇 |
1997年 | 12篇 |
1996年 | 23篇 |
1995年 | 20篇 |
1994年 | 21篇 |
1993年 | 32篇 |
1992年 | 31篇 |
1991年 | 14篇 |
1990年 | 23篇 |
1989年 | 18篇 |
1988年 | 21篇 |
1987年 | 21篇 |
1986年 | 9篇 |
1985年 | 43篇 |
1984年 | 40篇 |
1983年 | 24篇 |
1982年 | 36篇 |
1981年 | 19篇 |
1980年 | 28篇 |
1979年 | 33篇 |
1978年 | 11篇 |
1977年 | 14篇 |
1976年 | 17篇 |
1975年 | 19篇 |
1974年 | 11篇 |
1968年 | 8篇 |
排序方式: 共有1912条查询结果,搜索用时 31 毫秒
71.
72.
73.
Meredith C. K. Sellers Benjamin M. Castle Charles P. Marsh 《Journal of Solid State Electrochemistry》2013,17(1):175-182
Three-dimensional manganese dioxide (MnO2)-functionalized multiwalled carbon nanotube (MWCNT) electrodes have been produced by a simple and scalable thermal decomposition process. The electrodes are prepared by treating planar MWCNT sheets with manganese(II) nitrate (Mn(NO3)2) solution and annealing at low temperature (200–300 °C) and ambient pressure. The morphology, chemical composition, and structure of the resulting matrices have been investigated with scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray diffraction. Supercapacitors assembled with three-dimensional electrodes exhibit a 14-fold increase in specific capacitance (C sp) in comparison to those containing pristine, two-dimensional MWCNT electrodes. C sp varies linearly with Mn(NO3)2 thermal decomposition temperature (from 100 to 61 F/g at 0.2 A/g), a trend that is discussed in the context of nitrate reaction chemistry and MWCNT structure. This efficient and promising approach allows for simultaneous enhancement of electrode–electrolyte contact area and incorporation of redox-based charge storage within electrochemical capacitors. 相似文献
74.
Oxidation of 1,4-hydroquinones to 1,4-benzoquinones by mercuric oxide or mercuric trifluoroacetate in methanol has recently been described, and required reaction times of 1–12 hours.1 We now report that use of bromomercury(II) species as oxidants under alkaline conditions greatly reduces the reaction time. This oxidation system has recently been used for conversion of aromatic aldehydes into carboxylic acids.2 相似文献
75.
76.
A convenient and high yielding preparation of 2,6-di-t-butyl-1,4-benzoquinone from the iron-catalyzed oxidation of 2,4,6-tri-t-butylphenol with t-butyl hydroperoxide (TBHP) under acidic conditions is reported. 相似文献
77.
Liam J. R. McGeachie Cameron L. Carpenter-Warren David B. Cordes Michael Bühl Steven J. Gray Guoxiong Hua Alexandra M. Z. Slawin J. Derek Woollins 《无机化学与普通化学杂志》2020,646(22):1795-1798
An improved route to d-block and main group NSO complexes is presented including the synthesis of the first antimony(V) complexes, (Ar3Sb(NSO)2), and copper examples [CuBipy(PPh3)NSO]. The structures of eight complexes are reported. The observed variation in M–N–S bond angles is due to the combination of orbital overlap (ligand-to-metal bonding) and the degree of ionicity of the bonding. 相似文献
78.
McLain Derek R. Brossard Tom W. Tsai Yifen Condon Nicholas J. Canaday Jodi L. 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(5):2169-2174
Journal of Radioanalytical and Nuclear Chemistry - Two methods were used to evaluate the age of 75Se sealed source material. Both methods utilized gamma spectroscopy to determine the quantity of... 相似文献
79.
Raana Kashfi‐Sadabad Laura Gonzalez‐Fajardo Derek Hargrove Bahar Ahmadi Daniel Munteanu Sina Shahbazmohamadi Michael Jay Xiuling Lu 《Particle & Particle Systems Characterization》2019,36(4)
Nonspecific high‐energy radiation for treatment of metastatic ovarian cancer is limited by damage to healthy organs, which can be mitigated by the use of radiosensitizers and image‐guided radiotherapy. Gold (Au) and tantalum oxide (TaOx) nanoparticles (NPs), by virtue of their high atomic numbers, find utility in the design of bimetallic NP systems capable of high‐contrast computed tomography (CT) imaging as well as a potential radiosensitizing effect. These two radio‐dense metals are integrated into dendritic mesoporous silica NPs (dMSNs) with radial porous channels for high surface‐area loading of therapeutic agents. This approach results in stable, monodispersed dMSNs with a uniform distribution of Au on the surface and TaOx in the core that exhibits CT attenuation up to seven times greater than iodine or monometallic dMSNs without either TaOx or Au. Tumor targeting is assessed in a metastatic ovarian cancer mouse model. Ex vivo micro‐CT imaging of collected tumors shows that these NPs not only accumulate at tumor sites but also penetrate inside tumor tissues. This study demonstrates that after intraperitoneal administration, rationally designed bimetallic NPs can simultaneously serve as targeted contrast agents for imaging tumors and to enhance radiation therapy in metastatic ovarian cancer. 相似文献
80.
Derek Yiren Ong Zhihao Yen Asami Yoshii Julia RevilloImbernon Ryo Takita Shunsuke Chiba 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(15):5046-5051
New protocols for controlled reduction of carboxamides to either alcohols or amines were established using a combination of sodium hydride (NaH) and zinc halides (ZnX2). Use of a different halide on ZnX2 dictates the selectivity, wherein the NaH‐ZnI2 system delivers alcohols and NaH‐ZnCl2 gives amines. Extensive mechanistic studies by experimental and theoretical approaches imply that polymeric zinc hydride (ZnH2)∞ is responsible for alcohol formation, whereas dimeric zinc chloride hydride (H?Zn?Cl)2 is the key species for the production of amines. 相似文献