全文获取类型
收费全文 | 586887篇 |
免费 | 21143篇 |
国内免费 | 1484篇 |
专业分类
化学 | 331165篇 |
晶体学 | 7851篇 |
力学 | 28344篇 |
综合类 | 18篇 |
数学 | 74284篇 |
物理学 | 167852篇 |
出版年
2021年 | 7381篇 |
2020年 | 9708篇 |
2019年 | 8436篇 |
2018年 | 10641篇 |
2017年 | 9241篇 |
2016年 | 16807篇 |
2015年 | 11336篇 |
2014年 | 15138篇 |
2013年 | 29108篇 |
2012年 | 22077篇 |
2011年 | 23875篇 |
2010年 | 20033篇 |
2009年 | 19709篇 |
2008年 | 22577篇 |
2007年 | 22250篇 |
2006年 | 19746篇 |
2005年 | 17772篇 |
2004年 | 16441篇 |
2003年 | 14777篇 |
2002年 | 14643篇 |
2001年 | 15075篇 |
2000年 | 11622篇 |
1999年 | 8980篇 |
1998年 | 7844篇 |
1997年 | 7777篇 |
1996年 | 7297篇 |
1995年 | 6607篇 |
1994年 | 6553篇 |
1993年 | 6435篇 |
1992年 | 6677篇 |
1991年 | 7117篇 |
1990年 | 6804篇 |
1989年 | 6745篇 |
1988年 | 6647篇 |
1987年 | 6424篇 |
1986年 | 6146篇 |
1985年 | 7825篇 |
1984年 | 8209篇 |
1983年 | 6876篇 |
1982年 | 7283篇 |
1981年 | 6800篇 |
1980年 | 6458篇 |
1979年 | 6953篇 |
1978年 | 7205篇 |
1977年 | 7195篇 |
1976年 | 7157篇 |
1975年 | 6942篇 |
1974年 | 6775篇 |
1973年 | 6884篇 |
1972年 | 5154篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Dr. Jordan Donat Mr. Patrick Dubourdeaux Dr. Martin Clémancey Dr. Julia Rendon Clara Gervasoni Mr. Morgan Barbier Jessica Barilone Dr. Jacques Pécaut Prof. Dr. Serge Gambarelli Prof. Dr. Pascale Maldivi Prof. Dr. Jean-Marc Latour 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(70):e202201875
Nitrene transfer reactions have emerged as one of the most powerful and versatile ways to insert an amine function to various kinds of hydrocarbon substrates. However, the mechanisms of nitrene generation have not been studied in depth albeit their formation is taken for granted in most cases without definitive evidence of their occurrence. In the present work, we compare the generation of tosylimido iron species and NTs transfer from FeII and FeIII precursors where the metal is embedded in a tetracarbene macrocycle. Catalytic nitrene transfer to reference substrates (thioanisole, styrene, ethylbenzene and cyclohexane) revealed that the same active species was at play, irrespective of the ferrous versus ferric nature of the precursor. Through combination of spectroscopic (UV-visible, Mössbauer), ESI-MS and DFT studies, an FeIV tosylimido species was identified as the catalytically active species and was characterized spectroscopically and computationally. Whereas its formation from the FeII precursor was expected by a two-electron oxidative addition, its formation from an FeIII precursor was unprecedented. Thanks to a combination of spectroscopic (UV-visible, EPR, Hyscore and Mössbauer), ESI-MS and DFT studies, we found that, when starting from the FeIII precursor, an FeIII tosyliodinane adduct was formed and decomposed into an FeV tosylimido species which generated the catalytically active FeIV tosylimide through a comproportionation process with the FeIII precursor. 相似文献
22.
Meccanica - The static limit analysis of axially symmetric masonry domes subject to pseudo-static seismic forces is addressed. The stress state in the dome is represented by the shell stress... 相似文献
23.
Dr. Yolimar Gil Dr. Alejandro Castro-Alvarez Dr. Pablo Fuentealba Prof. Evgenia Spodine Dr. Daniel Aravena 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(48):e202200336
Enhancement of axial magnetic anisotropy is the central objective to push forward the performance of Single-Molecule Magnet (SMM) complexes. In the case of mononuclear lanthanide complexes, the chemical environment around the paramagnetic ion must be tuned to place strongly interacting ligands along either the axial positions or the equatorial plane, depending on the oblate or prolate preference of the selected lanthanide. One classical strategy to achieve a precise chemical environment for a metal centre is using highly structured, chelating ligands. A natural approach for axial-equatorial control is the employment of macrocycles acting in a belt conformation, providing the equatorial coordination environment, and leaving room for axial ligands. In this review, we present a survey of SMMs based on the macrocycle belt motif. Literature systems are divided in three families (crown ether, Schiff-base and metallacrown) and their general properties in terms of structural stability and SMM performance are briefly discussed. 相似文献
24.
Russian Chemical Bulletin - New representatives of (O-Si)-chelate compounds, N-(fluorosilyl)methyl derivatives of N-methylacetamide, N-methylbenzamide, N-phenylacetamide, and N-phenylbenzamide,... 相似文献
25.
Russian Journal of General Chemistry - A mechanochemical method was developed for the synthesis of ferromagnetic Pd–Fe–Co–Ni composites based on the natural biopolymer chitosan,... 相似文献
26.
Herraiz A. Gutierrez M. Ortega-Mier M. 《Central European Journal of Operations Research》2022,30(4):1427-1450
Central European Journal of Operations Research - We define a geometric transformation of Euclidean Travelling Salesman Problem (TSP) tours that leads to a new formulation of the TSP. For every... 相似文献
27.
Differential Equations - For a spectrally controllable linear autonomous system with incommensurable delays, we construct a dynamic state feedback in the form of a differential-difference... 相似文献
28.
Yuki Shintani Taku Ohtomi Dr. Aya Shibata Dr. Yoshiaki Kitamura Koichiro M. Hirosawa Prof. Kenichi G. N. Suzuki Prof. Masato Ikeda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(8):e202104421
Aqueous self-assembly of short peptides has attracted growing attention for the construction of supramolecular materials for various bioapplications. Herein, we describe how the thermolysin-assisted biocatalytic construction of a dipeptide hydrazide from an N-protected amino acid and an amino acid hydrazide leads to the formation of thermally stable supramolecular hydrogels. In addition, we demonstrate the post-assembly modification of the supramolecular architectures constructed in situ tethering hydrazide groups as a chemical handle by means of fluorescence imaging. 相似文献
29.
Russian Journal of Applied Chemistry - In September 1975, the head of Russian electrochemists, Academician A.N. Frumkin (1895–1976), in his report at the XI Mendeleev Congress on General and... 相似文献
30.
Moroz Ya. A. Lozinskyy N. S. Lopanov A. N. Chebyshev K. A. 《Russian Journal of General Chemistry》2022,92(1):101-107
Russian Journal of General Chemistry - Tungstophosphatozincates with the Keggin anion structure Kt5[PW11O39Zn(H2O)]?nH2O, Kt = Rb+, Cs+, (CH3)4N+; (C2H5)4N+ were synthesized. Their... 相似文献