全文获取类型
收费全文 | 8359篇 |
免费 | 863篇 |
国内免费 | 499篇 |
专业分类
化学 | 1541篇 |
晶体学 | 10篇 |
力学 | 694篇 |
综合类 | 169篇 |
数学 | 4714篇 |
物理学 | 2593篇 |
出版年
2024年 | 25篇 |
2023年 | 73篇 |
2022年 | 161篇 |
2021年 | 194篇 |
2020年 | 230篇 |
2019年 | 226篇 |
2018年 | 170篇 |
2017年 | 265篇 |
2016年 | 275篇 |
2015年 | 218篇 |
2014年 | 299篇 |
2013年 | 729篇 |
2012年 | 382篇 |
2011年 | 426篇 |
2010年 | 330篇 |
2009年 | 395篇 |
2008年 | 443篇 |
2007年 | 493篇 |
2006年 | 422篇 |
2005年 | 348篇 |
2004年 | 352篇 |
2003年 | 364篇 |
2002年 | 345篇 |
2001年 | 304篇 |
2000年 | 320篇 |
1999年 | 258篇 |
1998年 | 229篇 |
1997年 | 181篇 |
1996年 | 158篇 |
1995年 | 123篇 |
1994年 | 119篇 |
1993年 | 90篇 |
1992年 | 85篇 |
1991年 | 94篇 |
1990年 | 64篇 |
1989年 | 60篇 |
1988年 | 61篇 |
1987年 | 47篇 |
1986年 | 34篇 |
1985年 | 49篇 |
1984年 | 62篇 |
1983年 | 29篇 |
1982年 | 29篇 |
1981年 | 38篇 |
1980年 | 20篇 |
1979年 | 26篇 |
1978年 | 19篇 |
1977年 | 15篇 |
1976年 | 11篇 |
1973年 | 7篇 |
排序方式: 共有9721条查询结果,搜索用时 0 毫秒
61.
We investigate the phenomena of spontaneous symmetry breaking
for φ4 model on a square lattice in the parameter space by using
the potential importance sampling method, which was proposed by Milchev,
Heermann, and Binder [J. Stat. Phys. 44 (1986) 749]. The critical
values of the parameters allow us to determine the phase diagram of the
model. At the same time, some relevant quantities such as
susceptibility and specific heat are also obtained. 相似文献
62.
The orientation of antibodies, employed as capture molecules on biosensors, determines biorecognition efficiency and bioassay performance. In a previous publication we demonstrated for antibodies attached covalently to silicon that an increase in their surface amount Γ, evaluated with ellipsometry, induces changes in their orientation, which is traced directly using Time-of-Flight Secondary Ion Mass Spectroscopy combined with Principal Component Analysis. Here, we extend the above studies to antibodies adsorbed physically on a 3-aminopropyltriethoxysilane (APTES) monolayer. Antibodies physisorbed on APTES (0 ≤ Γ ≤ 3.5 mg/m2) reveal the Γ ranges for flat-on, side-on, and vertical orientation consistent with random molecular packing. The relation between orientation and Γ is juxtaposed for silicon functionalized with APTES, APTES modified with glutaraldehyde (APTES/GA) and N-hydroxysuccinimide-silane (NHS-silane). Antibody reorientation occurs at lower Γ values when physisorption (APTES) is involved rather than chemisorption (APTES/GA, NHS-silane). At high Γ values, comparable proportions of molecules adapting head-on and tail-on vertical alignment are concluded for APTES and the NHS-silane monolayer, and they are related to intermolecular dipole–dipole interactions. Intermolecular forces seem to be less decisive than covalent binding for antibodies on the APTES/GA surface, with dominant head-on orientation. Independently, the impact of glutaraldehyde activation of APTES on vertical orientation is confirmed by separate TOF-SIMS measurements. 相似文献
63.
Irina Legchenkova Mark Frenkel Nir Shvalb Shraga Shoval Oleg V. Gendelman Edward Bormashenko 《Entropy (Basel, Switzerland)》2022,24(6)
Properties of the Voronoi tessellations arising from random 2D distribution points are reported. We applied an iterative procedure to the Voronoi diagrams generated by a set of points randomly placed on the plane. The procedure implied dividing the edges of Voronoi cells into equal or random parts. The dividing points were then used to construct the following Voronoi diagram. Repeating this procedure led to a surprising effect of the positional ordering of Voronoi cells, reminiscent of the formation of lamellae and spherulites in linear semi-crystalline polymers and metallic glasses. Thus, we can conclude that by applying even a simple set of rules to a random set of seeds, we can introduce order into an initially disordered system. At the same time, the Shannon (Voronoi) entropy showed a tendency to attain values that are typical for completely random patterns; thus, the Shannon (Voronoi) entropy does not distinguish the short-range ordering. The Shannon entropy and the continuous measure of symmetry of the patterns demonstrated the distinct asymptotic behavior, while approaching the close saturation values with the increase in the number of iteration steps. The Shannon entropy grew with the number of iterations, whereas the continuous measure of symmetry of the same patterns demonstrated the opposite asymptotic behavior. The Shannon (Voronoi) entropy is not an unambiguous measure of order in the 2D patterns. The more symmetrical patterns may demonstrate the higher values of the Shannon entropy. 相似文献
64.
李杰 《浙江大学学报(理学版)》2006,33(5):500-502
令{Xm;1≤i≤n,n≥1}是行NA的随机变量三角阵列.利用NA随机变量序列的一个矩不等式,讨论了行NA的随机变量三角阵列在被随机变量X弱平均控制的条件下的完全收敛性.所得到的结果推广了行独立的随机变量三角阵列相应的结果. 相似文献
65.
Monika Schuster Claudia Turecek Helga Lichtenegger Robert Liska 《Applied Surface Science》2007,254(4):1131-1134
Continuously increasing life expectancy results in a rising number of bone diseases and fractures. Replacements from natural sources are not only limited in their availability, they also have some serious disadvantages such as possible immunological reactions or transmission of diseases. New synthetic biodegradable materials based on photopolymers could be an alternative solution. In these investigations an acrylate-based monomer formulation has been developed, consisting of a biodegradable basis monomer which is derived from gelatin, different reactive diluents, an appropriate photoinitiator and filler materials. For the three-dimensional shaping process stereolithography is the method of choice because of its capability to produce cellular structures with high resolutions. 相似文献
66.
REN Hongwu FANG Zujie 《Chinese Journal of Lasers》1999,8(4):327-333
Introduction Opticaltomographyusingnearinfraredlighttoextractinteriorabnormalitiesinformationattractsmanyresearchinterestsinbiomedicaloptics[1],becauseitprovidesanalternativepotentialmodalitytoprobebreastcancerandmonitorbrainandmuscleoxygenationnon… 相似文献
67.
M. Schilling M. C. Solci-palhares D. Klockow 《International journal of environmental analytical chemistry》2013,93(1-4):57-63
Abstract A new coating procedure for different diffusion controlled preconcentration methods (tubular denuder, annular denuder, diffusion screen) is described for the determination of nitric acid in air. In this study, a silanization reaction is applied to obtain a chemically fixed coating with an end placed functional NH2-group, which can be used as a sink to collect acidic compounds from air. This coating must be carried out only once and can be used for a long time. The denuders, coated with this procedures, were compared with conventionally coated NaF denuders. 相似文献
68.
高温气冷堆是新一代反应堆系统的热门候选堆型,已经受到国际上越来越多的关注。为设计和分析这种堆型,因其特有的包覆颗粒燃料引入了双重非均匀性,需要应用随机分布模型。对粗网格模型、细网格随机(FLS)模型、随机顺序添加(RSA)模型、子网格随机(Sub-FLS)模型和Metropolis模型等进行了研究,通过计算分析比较给出了各种模型的优缺点。结果表明:子网格随机模型和连续的RSA模型非常接近参考值,但是连续RSA模型的建模时间随着燃料体积份额的增加连续快速上升。 Key words: coated particle fuels; stochastic transport model; Monte Carlo; random distribution 相似文献
69.
Abstract The following analytical method has been used to identify some odorous compounds in the air of the water treatment plant Werdholzli, Zurich: sampling of contaminated air with the help of activated carbon, desorption by the solvents carbon disulphide and methylene chloride, separation of the carbon disulfide extract into a polar and a nonpolar fraction by adsorption column chromatography on silica. Hereafter gaschromatographic analysis of the polar fraction on glass capillary column (Ucon HB 5100); detection and identification were achieved by flame ionisation, thermoionic nitrogen selective detector and computerized mass spectrometry (Finnigan 3200 F, data system 6110). The results show the presence of sulfur compounds: thiophenes, thiazoles; nitrogen compounds: pyrazines; oxygen compounds: phenols, alcohols and some unsatured hydrocarbons. The malodorous compounds were sulfur and nitrogen compounds in the range of 0.01-0.1 ppm. 相似文献
70.
基于改进的Newman和Ziff算法以及有限尺寸标度理论, 通过对表征渗流相变特征物理量的序参量、平均集团尺寸、二阶矩、标准偏差及尺寸不均匀性的数值模拟, 分析研究了Erdös Rényi随机网络上Achlioptas爆炸渗流模型的相变性质.研究表明: 尽管序参量表现出了不连续相变的特征, 但序参量以及其他特征物理量仍具有连续相变的幂律标度行为.因此严格地说, Erdös Rényi随机网络中的爆炸渗流相变是一种奇异相变, 它既不是标准的不连续相变, 又与常规随机渗流表现出的连续相变处于不同的普适类.
关键词:
Erdös Rényi随机网络
爆炸渗流模型
相变
幂律标度行为 相似文献