全文获取类型
收费全文 | 699篇 |
免费 | 41篇 |
国内免费 | 4篇 |
专业分类
化学 | 425篇 |
晶体学 | 6篇 |
力学 | 20篇 |
数学 | 169篇 |
物理学 | 124篇 |
出版年
2024年 | 5篇 |
2023年 | 8篇 |
2022年 | 11篇 |
2021年 | 15篇 |
2020年 | 30篇 |
2019年 | 24篇 |
2018年 | 28篇 |
2017年 | 27篇 |
2016年 | 40篇 |
2015年 | 36篇 |
2014年 | 27篇 |
2013年 | 60篇 |
2012年 | 52篇 |
2011年 | 40篇 |
2010年 | 25篇 |
2009年 | 27篇 |
2008年 | 24篇 |
2007年 | 19篇 |
2006年 | 22篇 |
2005年 | 21篇 |
2004年 | 23篇 |
2003年 | 18篇 |
2002年 | 15篇 |
2001年 | 15篇 |
2000年 | 7篇 |
1999年 | 8篇 |
1998年 | 6篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1977年 | 3篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1966年 | 2篇 |
1960年 | 2篇 |
1958年 | 3篇 |
1947年 | 7篇 |
排序方式: 共有744条查询结果,搜索用时 15 毫秒
61.
T. A. Bal’burova V. G. Shiretorova E. V. Zoltoev G. I. Khanturgaeva 《Russian Journal of Applied Chemistry》2008,81(1):162-164
Optimal conditions for obtaining activated carbons from pine nutshells were determined. Their sorption properties were studied. 相似文献
62.
In the case of several formaldehyde derivatives, with importance in atmospheric and combustion chemistry, the currently available thermochemical values suffer from considerably large uncertainties. In this study a high-accuracy theoretical model chemistry has been used to provide accurate thermochemical data including heats of formation at 0 and 298 K and standard molar entropies at 298 K for CF(2)O, FCO, HFCO, HClCO, FClCO, HOCO, and NH(2)CO. For most of the thermochemical quantities studied here, this investigation delivers the best available estimate. 相似文献
63.
El-Ghayoury A Mézière C Simonov S Zorina L Cobián M Canadell E Rovira C Náfrádi B Sipos B Forró L Batail P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(47):14051-14059
We report on the acid ethylenedithiotetrathiafulvaleneamidoglycine (EDT-TTF-CO-NH-CH(2)-CO(2)H; 1; EDT-TTF=ethylenedithiotetrathiafulvalene) and the 1:1 adduct [(EDT-TTF)(·+)-CO-NH-CH(2)-(CO(2))(-)][(EDT-TTF)-CO-NH-CH(2)-(CO(2)H)]·CH(3)OH (2), a new type of hydrogen-bonded, 1:1 acid/zwitterion hybrid embrace of redox peptidics into a two-dimensional architecture, an example of a system deliberately fashioned so that oxidation of π-conjugated cores toward the radical-cation form would interfere with the activity of the appended ionizable residues in the presence of a templating base during crystal growth. First-principles calculations demonstrate that, notwithstanding preconceived ideas, a metallic state is more stable than the hole-localized alternatives for a neat 1:1 neutral acid/zwitterion hybrid. The inhomogeneous Coulomb field associated with proton-shared, interstacks O-H···O hydrogen bonds between the ionizable residues distributed on both sides of the two-dimensional π-conjugated framework leads, however, to a weak hole localization responsible for the activated but high conductivity of 1 S cm(-1). This situation is reminiscent of the role of the environment on electron transfer in tetraheme cytochrome c, in which the protonation state of a heme propionate becomes paramount, or ion-gated transport phenomena in biology. These observations open rather intriguing opportunities for the construction of electronic systems at the interface of chemistry and biology. 相似文献
64.
For just over a decade, stochastic gene expression has been the focus of many experimental and theoretical studies. It is now widely accepted that noise in gene expression can be decomposed into extrinsic and intrinsic components, which have orthogonal contributions to the total noise. Intrinsic noise stems from the random occurrence of biochemical reactions and is inherent to gene expression. Extrinsic noise originates from fluctuations in the concentrations of regulatory components or random transitions in the cell's state and is imposed to the gene of interest by the intra- and extra-cellular environment. The basic assumption has been that extrinsic noise acts as a pure input on the gene of interest, which exerts no feedback on the extrinsic noise source. Thus, multiple copies of a gene would be uniformly influenced by an extrinsic noise source. Here, we report that this assumption falls short when multiple genes share a common pool of a regulatory molecule. Due to the competitive utilization of the molecules existing in this pool, genes are no longer uniformly influenced by the extrinsic noise source. Rather, they exert negative regulation on each other and thus extrinsic noise cannot be determined by the currently established method. 相似文献
65.
在低温条件下采用定向刻蚀技术, 对金属Ti片表面用H2O2溶液进行刻蚀氧化, 制备了垂直生长的纳米TiO2叶片状阵列薄膜电极. 通过X射线衍射分析表明, 纳米TiO2叶片状阵列薄膜经500 ℃下烧结1 h后, 从无定型转变为锐钛矿相. 场发射扫描电子显微镜观察表明: 在80 ℃下的H2O2溶液刻蚀氧化, 经1 d制备得到的是Ti片表面垂直生长的叶片状阵列, 其形貌均匀且完整地
关键词:
2')" href="#">纳米TiO2
叶片状阵列电极
染料敏化太阳电池
电子传输 相似文献
66.
Balčiūnas T Mücke OD Mišeikis P Andriukaitis G Pugžlys A Giniūnas L Danielius R Holzwarth R Baltuška A 《Optics letters》2011,36(16):3242-3244
In this paper we report on the active stabilization of the carrier envelope phase (CEP) of a Yb:KGW chirped pulse amplifier laser system seeded by a Yb-doped solid-state Kerr-lens mode-locked oscillator. The regenerative amplifier delivers 180 fs CEP stable pulses of 30 μJ-1 mJ energy at a repetition rate tunable from 1 to 200 kHz. The bandwidth of the feedback loop was extended by a factor of 5 using a specially designed high-pass filter, which resulted in a dramatic decrease of CEP jitter below 0.45 rad after the amplifier. 相似文献
67.
Sánchez-Coronilla A Balón M Marcos ES Muñoz MA Carmona C 《Physical chemistry chemical physics : PCCP》2010,12(20):5276-5284
In this work, we present a quantum mechanical investigation on the hydrogen bond interactions of N(9)-methyl-9H-pyrido[3,4-b]indole, MBC, and N(2)-methyl-9H-pyrido[3,4-b]indole, BCA, with different hydrogen bond donors. Thus, it has been analysed the influence that the hydrogen bond donor strength and the co-operative effect of the increasing number of donor molecules have on the shape of the potential energy surfaces versus the N···H distances, r(N–H). To rationalize the nature of the interactions, the Bader theory has been applied and the characteristics of the bond critical points analysed. The results show that two different hydrogen bond complexes can be formed depending on the donor capabilities or the number of donor molecules included in the calculations. The topological parameters from the Bader theory are used to justify the statement that the analysed interactions can be classified as weak or partially covalent hydrogen bond interactions, respectively. As experimentally observed, weak hydrogen bond donors form weak hydrogen bond complexes, called HBC. Upon the increase of the donor strength the N···H proton is shifted nearest to the nitrogen atom giving rise to the observation of a stronger hydrogen bond complex, the proton transfer complex, PTC. The most outstanding result of these studies is the fact that the formation of the PTC can also be managed just by changing the number of donor molecules, that is, by a co-operative effect of the hydrogen bonds. 相似文献
68.
Pulse compression of nanojoule pulses in the visible using microstructure optical fiber and dispersion compensation 总被引:2,自引:0,他引:2
S. Lakó J. Seres P. Apai J. Balázs R.S. Windeler R. Szipőcs 《Applied physics. B, Lasers and optics》2003,76(3):267-275
Experimental results on the pulse compression of 1-nJ, 150-fs pulses from a tunable, 76-MHz Ti:sapphire laser oscillator operating
at around 750 nm are reported. The length of the pulses can be compressed to nearly one tenth by applying a high-delta, single-mode
microstructured optical fiber exhibiting zero group-delay dispersion at 767 nm, and by a prism-pair/chirped-mirror compressor.
The experimental results are verified by theoretical investigations modeling the pulse propagation taking into account non-linear
self-phase modulation and fiber dispersion.
Received: 10 June 2002 / Revised version: 15 November 2002 / Published online: 12 February 2003
RID="*"
ID="*"Corresponding author. Fax: +36-1/375-4553, E-mail: szipoecs@sunserv.kfki.hu 相似文献
69.
Dr. Christian Marquardt M. Sc. Tobias Kahoun Dr. Andreas Stauber Dr. Gábor Balázs Dr. Michael Bodensteiner Prof. Dr. Alexey Y. Timoshkin Prof. Dr. Manfred Scheer 《Angewandte Chemie (International ed. in English)》2016,55(47):14828-14832
We report on the synthesis and structural characterization of unprecedented anionic parent compounds of mixed Group 13/15 elements. The reactions of the pnictogenylboranes H2E‐BH2?NMe3 ( 1 a =P, 1 b =As) with phosphorus and arsenic centered nucleophiles of the type [EH2]? (E=P, As) lead to the formation of compounds of the type [H2E‐BH2‐E′H2]? ( 2 : E=E′=P; 3 : E=E′=As; 4 : E=P, E′=As) containing anionic pnictogen–boron chain‐like units. Furthermore, a longer 5‐membered chain species [H2As‐BH2‐PH2‐BH2‐AsH2]? ( 5 ) and a cyclic compound [NHCdipp‐H2B‐PH2‐BH2‐NHCdipp]+[P5B5H19]? ( 6 ) containing a n‐butylcyclohexane‐like anion were obtained. All the compounds have been characterized by X‐ray structure analysis, multinuclear NMR spectroscopy, IR spectroscopy, and mass spectrometry. DFT calculations elucidate their high thermodynamic stability, the charge distribution, and give insight into the reaction pathway. 相似文献
70.
Motivated by recent experiments on interacting cold atoms, we analyze interaction quenches in Luttinger liquids (LLs), where the interaction is ramped from zero to a finite value within a finite time. The fermionic single particle density matrix reveals several regions of spatial and temporal coordinates relative to the quench time, termed as Fermi liquid, sudden quench LL, adiabatic LL regime, and a LL regime with a time-dependent exponent. The various regimes can also be observed in the momentum distribution of the fermions, directly accessible through time of flight experiments. Most of our results apply to arbitrary quench protocols. 相似文献