全文获取类型
收费全文 | 2102篇 |
免费 | 282篇 |
国内免费 | 159篇 |
专业分类
化学 | 1644篇 |
晶体学 | 26篇 |
力学 | 69篇 |
综合类 | 9篇 |
数学 | 204篇 |
物理学 | 591篇 |
出版年
2024年 | 4篇 |
2023年 | 32篇 |
2022年 | 55篇 |
2021年 | 54篇 |
2020年 | 53篇 |
2019年 | 80篇 |
2018年 | 70篇 |
2017年 | 49篇 |
2016年 | 89篇 |
2015年 | 100篇 |
2014年 | 113篇 |
2013年 | 160篇 |
2012年 | 187篇 |
2011年 | 196篇 |
2010年 | 130篇 |
2009年 | 102篇 |
2008年 | 139篇 |
2007年 | 118篇 |
2006年 | 135篇 |
2005年 | 111篇 |
2004年 | 104篇 |
2003年 | 74篇 |
2002年 | 69篇 |
2001年 | 24篇 |
2000年 | 24篇 |
1999年 | 38篇 |
1998年 | 24篇 |
1997年 | 28篇 |
1996年 | 36篇 |
1995年 | 17篇 |
1994年 | 11篇 |
1993年 | 9篇 |
1992年 | 13篇 |
1991年 | 9篇 |
1990年 | 12篇 |
1989年 | 6篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1986年 | 2篇 |
1985年 | 7篇 |
1984年 | 10篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1938年 | 1篇 |
排序方式: 共有2543条查询结果,搜索用时 31 毫秒
91.
92.
93.
94.
Dr. Maria Książek Dr. Marek Weselski Marcin Kaźmierczak Aleksandra Tołoczko Dr. Miłosz Siczek Dr. Piotr Durlak Dr. Juliusz A. Wolny Prof. Dr. Volker Schünemann Prof. Dr. Joachim Kusz Dr. Robert Bronisz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(63):14419-14434
Reaction of 1,2-di(tetrazol-2-yl)ethane (ebtz) with Fe(BF4)2⋅6 H2O in different nitriles yields one-dimensional coordination polymers [Fe(ebtz)2(RCN)2](BF4)2⋅nRCN (n=2 for R=CH3 ( 1 ) and n=0 for R=C2H5 ( 2 ) C3H7 ( 3 ), C3H5 ( 4 ), CH2Cl ( 5 )) exhibiting spin crossover (SCO). SCO in 1 and 3 – 5 is complete and occurs above 160 K. In 2 , it is shifted to lower temperatures and is accompanied by wide hysteresis (T1/2↓=78 K, T1/2↑=123 K) and proceeds extremely slowly. Isothermal (80 K) time-resolved single-crystal X-ray diffraction studies revealed a complex nature for the HS→LS transition in 2 . An initial, slow stage is associated with shrinkage of polymeric chains and with reduction of volume at 77 % (in relation to the difference between cell volumes VHS−VLS) whereas only 16 % of iron(II) ions change spin state. In the second stage, an abrupt SCO occurs, associated with breathing of the crystal lattice along the direction of the Fe–nitrile bonds, while the nitriles reorient. HS→LS switching triggered by light (808 nm) reveals the coupling of spin state and nitrile orientation. The importance of this coupling was confirmed by studies of [Fe(ebtz)2(C2H5CN/C3H7CN)2](BF4)2 mixed crystals ( 2 a , 2 b ), showing a shift of T1/2 to higher values and narrowing of the hysteresis loop concomitant with an increase of the fraction of butyronitrile. This increase reduces the capability of nitrile molecules to reorient. Density functional theory (DFT) studies of models of 1 – 5 suggest a particular possibility of 2 to adopt a low (140–145°) value of its Fe-N-C(propionitrile) angle. 相似文献
95.
Birnšteinová Š. Hnatič M. Lučivjanský T. Mižišin L. Škultéty V. 《Theoretical and Mathematical Physics》2019,200(3):1335-1347
Theoretical and Mathematical Physics - We study an instructive model of the directed percolation process near its second-order phase transition between absorbing and active states. We first express... 相似文献
96.
Hyuk‐Joon Cho Sang‐Mi Jeong Taekyung Lim Sanghyun Ju 《Journal of polymer science. Part A, Polymer chemistry》2019,57(4):495-502
Toward the goal of smart sensor systems for wearable electronics, polymer microfiber‐based free‐standing sensors benefit from excellent flexibility, decent ductility, and easy wearability in comparison with thin‐film‐based sensing devices. Herein, we report a hydrophobic and conducting single‐strand microfiber‐based liquid‐phase chemical sensor consisting of polyurethane (PU), tin oxide (SnO2), and carbon nanotube (CNT) composites with applying a (1H,1H,2H,2H‐heptadecafluorodec‐1‐yl) phosphonic acid (HDF‐PA)‐based self‐assembled monolayer. The free‐standing HDF‐PA‐treated PU–SnO2–CNT composite microfiber showing selective filtering properties with the repellency of water and the penetration of an organic solvent is electrically and mechanically characterized. Finally, the single‐strand HDF‐PA‐treated PU–SnO2–CNT composite microfiber‐based chemical sensor, which shows excellent mechanical properties and aqueous stability, is demonstrated to detect the presence of a chemical in pure water or counterfeit gasoline in pure gasoline by observing mechanical changes, especially variations in the length and diameter of the fiber, and monitoring the electrical resistance change. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 495–502 相似文献
97.
Miša Biro Darja Kavšek Jakub Karasiński Piotr Szwarczewski Ewa Bulska Darinka Brodnjak Vončina 《Central European Journal of Chemistry》2014,12(6):687-699
The development and validation of a reliable analytical procedure for the determination of selected metals (Cd, Cr, Cu, Pb, Zn and Mn) in sediments accumulated in the Utrata River (Poland) is described. The aqua regia extraction followed by inductively coupled plasma optical emission spectrometry (ICP-OES) was used for this purpose. The optimized analytical procedure was validated, and adequate quality control actions were implemented in order to provide reliable data. The precision under’ within-laboratory’ reproducibility conditions was estimated from duplicate analysis. Certified reference material (CRM) was used in order to evaluate the accuracy of the results regarding the sewage sludge amended soil CRM 143R. The detection limits for all elements of interest were well-below their content in the investigated sediment samples. The obtained reliable data could be used for assessment of the relationship between human economic activity in the past and the geochemical features of the sediments. 相似文献
98.
Active-to-absorbing phase transition subjected to the velocity fluctuations in the frozen limit case
N. V. Antonov M. Hnatich A. S. Kapustin T. Lučivjanský L. Mižišin 《Physics of Particles and Nuclei Letters》2017,14(6):944-952
The directed bond percolation process is studied in the presence of compressible velocity fluctuations with long-range correlations. We discuss a construction of a field theoretic action and a way of obtaining its large scale properties using the perturbative renormalization group. The most interesting results for the frozen velocity limit are given. 相似文献
99.
Matej Mičušík Audrey Bonnefond Maria Paulis Jose R. Leiza 《European Polymer Journal》2012,48(5):896-905
The nitroxide mediated controlled surface initiated polymerization of methyl methacrylate (MMA)/butyl acrylate (n-BA) was carried out with a macroinitiator modified montmorillonite. The macroinitiator was synthesized by the nitroxide mediated polymerization of vinylbenzyl trimethylammonium chloride (VBTMACl), methylmethacrylate (MMA) and styrene (S) at 90 °C using BlocBuilder®. The macroinitiator was exchanged with the sodium cations of the montmorillonite, to yield surface modified reactive montmorillonite. The bulk polymerizations of BA/MMA from the clay surface produced controlled molecular weight polymers that were able to exfoliate the clay. This controlled polymer/clay nanocomposite was used as masterbatch and further dispersed in monomers and miniemulsified to perform miniemulsion polymerization of BA/MMA (90/10 wt.%) at 30 wt.% solids content at low emulsifier concentration. The adhesive properties of the nanocomposites prepared with the masterbatch were proved to be better than those prepared with an organically modified clay. 相似文献
100.
Vladislava Mičková Silvia Ružičková Dagmar Remeteiová Martina Laubertová Marianna Dorková 《Chemical Papers》2018,72(5):1231-1238
Sampling is the most important procedure in arriving at the value of an electronic scrap. Inappropriate sampling makes other procedures, including assaying, valueless, as the sample must really represent the electronic scrap from which it was taken. The aim of this study was to develop the procedure to investigate the composition of heterogeneous printed circuit boards (PCBs) material and to show its applicability as well as its related limitations. The contents of Cu, Pb, Ni, and Zn in PCBs from wasted mobile phones were determined. Mixtures of aqua regia, hydrogen peroxide and hydrofluoric acid were applied to sample digestion. Open and closed vessel wet digestion with or without heating and microwave-assisted one was realized. For these purposes different sample amounts (0.2, 0.4, and 0.5 g) were applied and on the basis of calculated relative standard deviation values (RSD), the precision of repeated the most effective digestion was evaluated. The microwave-assisted wet digestion and mixture of aqua regia and hydrogen peroxide was found as the most effective one of the compared mixtures and applied conditions. A sample amount of 0.5 g was found as the most suitable. RSD values confirm the importance of electronic waste material sample preparation. 相似文献