全文获取类型
收费全文 | 7262篇 |
免费 | 305篇 |
国内免费 | 52篇 |
专业分类
化学 | 5331篇 |
晶体学 | 71篇 |
力学 | 190篇 |
综合类 | 1篇 |
数学 | 930篇 |
物理学 | 1096篇 |
出版年
2023年 | 52篇 |
2022年 | 35篇 |
2021年 | 134篇 |
2020年 | 142篇 |
2019年 | 125篇 |
2018年 | 102篇 |
2017年 | 86篇 |
2016年 | 209篇 |
2015年 | 187篇 |
2014年 | 225篇 |
2013年 | 380篇 |
2012年 | 533篇 |
2011年 | 583篇 |
2010年 | 332篇 |
2009年 | 241篇 |
2008年 | 490篇 |
2007年 | 511篇 |
2006年 | 519篇 |
2005年 | 498篇 |
2004年 | 424篇 |
2003年 | 338篇 |
2002年 | 248篇 |
2001年 | 76篇 |
2000年 | 52篇 |
1999年 | 53篇 |
1998年 | 51篇 |
1997年 | 63篇 |
1996年 | 95篇 |
1995年 | 59篇 |
1994年 | 56篇 |
1993年 | 62篇 |
1992年 | 42篇 |
1991年 | 26篇 |
1990年 | 26篇 |
1989年 | 24篇 |
1988年 | 38篇 |
1987年 | 23篇 |
1986年 | 30篇 |
1985年 | 61篇 |
1984年 | 39篇 |
1983年 | 25篇 |
1982年 | 49篇 |
1981年 | 26篇 |
1980年 | 21篇 |
1979年 | 26篇 |
1978年 | 32篇 |
1977年 | 28篇 |
1976年 | 23篇 |
1975年 | 19篇 |
1974年 | 22篇 |
排序方式: 共有7619条查询结果,搜索用时 31 毫秒
1.
Mueller Eric V. Gallagher Michael R. Skowronski Nicholas Hadden Rory M. 《Transport in Porous Media》2021,138(3):637-660
Transport in Porous Media - Modeling flow in vegetative fuel beds is a key component in any detailed physics-based tool for simulating wildland fire dynamics. Current approaches for drag modeling,... 相似文献
2.
The Swendsen‐Wang (SW) dynamics is a popular Markov chain for sampling from the Gibbs distribution for the ferromagnetic Ising model on a graph G = (V,E). The dynamics is conjectured to converge to equilibrium in O(|V|1/4) steps at any (inverse) temperature β, yet there are few results providing o(|V|) upper bounds. We prove fast convergence of the SW dynamics on general graphs in the tree uniqueness region. In particular, when β < βc(d) where βc(d) denotes the uniqueness/nonuniqueness threshold on infinite d‐regular trees, we prove that the relaxation time (i.e., the inverse spectral gap) of the SW dynamics is Θ(1) on any graph of maximum degree d ≥ 3. Our proof utilizes a monotone version of the SW dynamics which only updates isolated vertices. We establish that this variant of the SW dynamics has mixing time and relaxation time Θ(1) on any graph of maximum degree d for all β < βc(d). Our proof technology can be applied to general monotone Markov chains, including for example the heat‐bath block dynamics, for which we obtain new tight mixing time bounds. 相似文献
3.
Habarurema Gratien Gerber Thomas Mukabagorora Theonille Hosten Eric Ndayambaje Jean Bernard Betz Richard 《Transition Metal Chemistry》2020,45(1):55-63
Transition Metal Chemistry - Rhenium(I) and (VII) complexes with cyclohex-1-enylolonium cation and bridging pyridyl derivatives are reported. Additionally, the CO-bridged pyridyl and their related... 相似文献
4.
5.
6.
7.
Control over Nanostructures and Associated Mesomorphic Properties of Doped Self‐Assembled Triarylamine Liquid Crystals 下载免费PDF全文
Dr. Yuya Domoto Dr. Eric Busseron Prof. Dr. Mounir Maaloum Dr. Emilie Moulin Prof. Dr. Nicolas Giuseppone 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(5):1938-1948
We have synthesized a series of triarylamine‐cored molecules equipped with an adjacent amide moiety and dendritic peripheral tails in a variety of modes. We show by 1H NMR and UV/Vis spectroscopy that their supramolecular self‐assembly can be promoted in solution upon light stimulation and radical initiation. In addition, we have probed their molecular arrangements and mesomorphic properties in the bulk by integrated studies on their film state by using differential scanning calorimetry (DSC), variable‐temperature polarizing optical microscopy (VT‐POM), variable‐temperature X‐ray diffraction (VT‐XRD), and atomic force microscopy (AFM). Differences in the number and the disposition of the peripheral tails significantly affect their mesomorphic properties associated with their lamellar‐ or columnar‐packed nanostructures, which are based on segregated stacks of the triphenylamine cores and the lipophilic/lipophobic periphery. Such structural tuning is of interest for implementation of these soft self‐assemblies as electroactive materials from solution to mesophases. 相似文献
8.
Brian R. Holder Colleen A. McNaney David Luchetti Eric Schaeffer Dieter M. Drexler 《Biomedical chromatography : BMC》2015,29(9):1375-1379
Acetyl‐l ‐carnitine (ALCAR) is a potential biomarker for the modulation of brain neurotransmitter activity, but is also present in cerebrospinal fluid (CSF). Recent studies have utilized hydrophilic interaction liquid chromatography–tandem mass spectrometry (HILIC‐MS/MS) based assays to detect and quantify ALCAR within biofluids such as urine, plasma and serum, using various sample pretreatment procedures. In order to address the need to quantify ALCAR in CSF on a high‐throughput scale, a new and simple HILIC‐MS/MS assay has been successfully developed and validated. For rapid analysis, CSF sample pretreatment was performed via ‘dilute and shoot’ directly onto an advanced HILIC column prior to MS/MS detection. This newly developed HILIC‐MS/MS assay shows good recoveries of ALCAR without the need for chemical derivatization and multistep sample extraction procedures. The employment of this assay is suitable for the high‐throughput bioanalysis and quantification of ALCAR within the CSF of various animal models and human clinical studies. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
9.
10.
Chemorheology investigation of a glassy epoxy thermoset on tensile plastic flow and fracture morphology 下载免费PDF全文
Stephen F. Foster Emily A. Hoff Greg W. Curtzwiler Eric B. Williams Kevin B. Davis Derek L. Patton James W. Rawlins 《Journal of Polymer Science.Polymer Physics》2015,53(19):1333-1344
Reproducible and uncharacteristic tensile stress–strain behavior of cured glassy epoxy‐amine networks produces distinctive fracture surfaces. Test specimens exhibiting plastic flow result in mirror‐like fracture surfaces, whereas samples that fail during yield or strain softening regions possess nominal mirror‐mist‐hackle topography. Atomic force microscopy and scanning electron microscopy reveal branched nodule morphologies in the 50‐nm size scale that may be responsible for the unusual tensile properties. Current hypothesis is that plastic flow of the glassy thermoset occurs through the existence and deformation of these nodular nanostructures. The thermal cure profile of the epoxy‐amine thermoset affects the size and formation of the nodular nanostructure. Eliminating vitrification during thermoset polymerization forms a more continuous phase, reduction in size of the nodules, and eliminates the capacity of the material to yield in plastic flow. This maximizes nanostructure connectivity of the glassy epoxy‐amine thermoset and reduces strain to failure significantly. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1333–1344. 相似文献