全文获取类型
收费全文 | 2183篇 |
免费 | 83篇 |
国内免费 | 8篇 |
专业分类
化学 | 1369篇 |
晶体学 | 18篇 |
力学 | 51篇 |
数学 | 229篇 |
物理学 | 607篇 |
出版年
2023年 | 27篇 |
2022年 | 33篇 |
2021年 | 38篇 |
2020年 | 60篇 |
2019年 | 51篇 |
2018年 | 39篇 |
2017年 | 35篇 |
2016年 | 67篇 |
2015年 | 62篇 |
2014年 | 89篇 |
2013年 | 200篇 |
2012年 | 125篇 |
2011年 | 157篇 |
2010年 | 84篇 |
2009年 | 84篇 |
2008年 | 129篇 |
2007年 | 133篇 |
2006年 | 82篇 |
2005年 | 81篇 |
2004年 | 67篇 |
2003年 | 41篇 |
2002年 | 31篇 |
2001年 | 34篇 |
2000年 | 20篇 |
1999年 | 9篇 |
1998年 | 8篇 |
1997年 | 9篇 |
1996年 | 14篇 |
1995年 | 17篇 |
1994年 | 24篇 |
1993年 | 27篇 |
1992年 | 17篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 13篇 |
1988年 | 17篇 |
1987年 | 20篇 |
1986年 | 17篇 |
1985年 | 22篇 |
1984年 | 16篇 |
1983年 | 23篇 |
1982年 | 26篇 |
1981年 | 22篇 |
1980年 | 21篇 |
1979年 | 19篇 |
1978年 | 22篇 |
1977年 | 14篇 |
1976年 | 19篇 |
1974年 | 16篇 |
1973年 | 12篇 |
排序方式: 共有2274条查询结果,搜索用时 15 毫秒
1.
2.
Satyanarayana A. V. S. Rao M. Jagannadha Mouli K. Chandra 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(3):1509-1513
Journal of Radioanalytical and Nuclear Chemistry - 相似文献
3.
Dr. Arijit Singha Hazari Shubhadeep Chandra Prof. Sanjib Kar Prof. Dr. Biprajit Sarkar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(24):e202104550
Metal complexes of multi-porphyrins and multi-corroles are unique systems that display a host of extremely interesting properties. Availability of free meso and β positions allow formation of different types of directly linked bis-porphyrins giving rise to intriguing optical and electronic properties. While the fields of metalloporphyrin and corroles monomer have seen exponential growth in the last decades, the chemistry of metal complexes of bis-porphyrins and bis-corroles remain rather underexplored. Therefore, the impact of covalent linkages on the optical, electronic, (spectro)electrochemical, magnetic and electrocatalytic activities of metal complexes of bis-porphyrins and -corroles has been summarized in this review article. This article shows that despite the (still) somewhat difficult synthetic access to these molecules, their extremely exciting properties do make a strong case for pursuing research on these classes of compounds. 相似文献
4.
Dapeng Liu Binod R. Giri Milán Szőri Béla Viskolcz Et-touhami Es-sebbar Aamir Farooq 《Proceedings of the Combustion Institute》2021,38(1):967-976
NOx mitigation is a central focus of combustion technologies with increasingly stringent emission regulations. NOx can also enhance the autoignition of hydrocarbon fuels and can promote soot oxidation. The reaction between allyl radical (C3H5) and NOx plays an important role in the oxidation kinetics of propene. In this work, we measured the absolute rate coefficients for the redox reaction between C3H5 and NOx over the temperature range of 1000–1252 K and pressure range of 1.5–5.0 bar using a shock tube and UV laser absorption technique. We produced C3H5 by shock heating of C3H5I behind reflected shock waves. Using a Ti:Sapphire laser system with frequency quadrupling, we monitored the kinetics of C3H5 at 220 nm. Unlike low-temperature chemistry, the two target reactions, C3H5 + NO → products (R1) and C3H5 + NO2 → products (R2), exhibited a strong positive temperature dependence for this radical-radical type reaction. However, these reactions did not show any pressure dependence over the pressure range of 1.5–5.0 bar, indicating that the measured rate coefficients are close to the high-pressure limit. The measured values of the rate coefficients resulted in the following Arrhenius expressions (in unit of cm3/molecule/s):To our knowledge, these are the first high-temperature measurements of allyl + NOx reactions. The reported data will be highly useful in understanding the interaction of NOx with resonantly stabilized radicals as well as the mutual sensitization effect of NOx on hydrocarbon fuels. 相似文献
5.
Harsha K. Tripathy Nair S.V. Manju Sreekanth Dittakavi Ram Murthi Bestha Ramesh Mullangi 《Biomedical chromatography : BMC》2020,34(12):e4953
Larotrectinib is a first-generation tropomyosin kinase inhibitor, approved for the treatment of solid tumors. In this paper, we present a validated dried blood spot (DBS) method for the quantitation of larotrectinib from mouse blood using HPLC–MS/MS, which was operated under multiple reaction monitoring mode. To the DBS disc cards, acidified methanol enriched with internal standard (IS; enasidenib) was added and extracted using tert-butyl methyl ether as an extraction solvent with sonication. Chromatographic separation of larotrectinib and the IS was achieved on an Atlantis dC18 column using 10 mm ammonium formate–acetonitrile (30:70, v/v) delivered at a flow-rate of 0.80 ml/min. Under these optimized conditions, the retention times of larotrectinib and the IS were ~0.93 and 1.37 min, respectively. The total run time was 2.50 min. Larotrectinib and the IS were analyzed using positive ion scan mode and parent–daughter mass to charge ion (m/z) transitions of 429.1 → 342.1 and 474.1 → 267.1, respectively, were used for the quantitation. The calibration range was 1.06–5,080 ng/ml. No matrix effect or carryover was observed. Hematocrit did not influence DBS larotrectinib concentrations. All of the validation parameters met the acceptance criteria. The applicability of the validated method was shown in a mouse pharmacokinetic study. 相似文献
6.
Theoretical insight of nitric oxide adsorption on neutral and charged Pdn (n = 1–5) clusters 下载免费PDF全文
Pakiza Begum Pranjal Gogoi Bhupesh Kumar Mishra Ramesh Chandra Deka 《International journal of quantum chemistry》2015,115(13):837-845
Density functional theory (DFT) calculations within the framework of generalized gradient approximation have been used to systematically investigate the adsorption of nitric oxide (NO) molecule on neutral, cationic, and anionic Pdn (n = 1–5) clusters. NO coordinate to one Pd atom of the cluster by the end‐on mode, where the tilted end‐on structure is more favorable due to the additional electron in the π* orbital. On the contrary, in the neutral and cationic Pd2 system, NO coordinates to the bridge site of cluster preferably by the side‐on mode. Charge transfer between Pd clusters and NO molecule and the corresponding weakening of N? O bond is an essential factor for the adsorption. The N? O stretching frequency follow the order of cationic > neutral > anionic. Binding energy of NO on anionic clusters is found to be greater than those of neutral and cationic clusters. © 2015 Wiley Periodicals, Inc. 相似文献
7.
The interface between fibre and matrix of fibrous polymeric composites is most critical and decisive in maintaining sustainability, durability and also reliability of this potential material, but unfortunately a comprehensive conclusion is yet to meet the label of confidence for the engineering viability. Fiber reinforced polymer (FRP) composites are being accepted and also utilized as better and reliable alternative materials for repairing and/or replacing conventional materials, starting from tiny objects to mega structure in various engineering applications. The promise and potential of these materials are sometimes threatened in speedy replacement of conventional materials because of their inhomogeneities and inherent susceptibility to degradation due to moist and thermal environments. Environmental conditioning is traditionally believed to be a physical phenomenon but present literature has revealed that the interdiffusion between fiber and polymer matrix resin comprises of physical, chemical, mechanical, physico-chemical and mechano-chemical phenomena. The failure and fracture behavior at ambient conditions itself is a complex phenomenon till at present. The service conditions which are mostly hygrothermal in nature, along with a variation of applied loads make the mechanical behavior nearly unpredictable, far off from conclusions in evaluating the short term as well as long term durability and reliability of FRPs. It is essential to accurately simulate the initial and subsequent evolution process of this kind of damage phenomena, in order to explore the full potential of the mechanical properties of composite laminates. The present review has emphasized the need of complying scattered as well as limited literature on this front, and has focused on creating the urgency to highlight the importance of judicious uses of these materials with minimum safety factors with an aim to achieving lighter weight in enhancing specific properties. 相似文献
8.
9.
10.
MXenes are recently developed two-dimensional layered materials composed of early transition metal carbides and/or nitrides that provide unique characteristics for biosensor applications. This review presents the recent progress made on the usage and applications of MXenes in the field of electrochemical biosensors, including microfluidic biosensors and wearable microfluidic biosensors, and highlights the challenges with possible solutions and future needs. The multilayered configuration and high conductivity make these materials as an immobilization matrix for the biomolecule immobilization with activity retention and to be explored in the fabrication of electrochemical sensors, respectively. First, how the MXene nanocomposite as an electrode modifier affects the sensing performance of the electrochemical biosensors based on enzymes, aptamer/DNA, and immunoassays is well described. Second, recent developments in MXene nanocomposites as wearable biosensing platforms for the biomolecule detection are highlighted. This review pointed out the future concerns and directions for the use of MXene nanocomposites to fabricate advanced electrochemical biosensors with high sensitivity and selectivity. Specifically, possibilities for developing microfluidic electrochemical sensors and wearable electrochemical microfluidic sensors with integrated biomolecule detection are emphasized. 相似文献