全文获取类型
收费全文 | 3842篇 |
免费 | 121篇 |
国内免费 | 18篇 |
专业分类
化学 | 2875篇 |
晶体学 | 15篇 |
力学 | 58篇 |
数学 | 624篇 |
物理学 | 409篇 |
出版年
2023年 | 21篇 |
2022年 | 21篇 |
2021年 | 45篇 |
2020年 | 61篇 |
2019年 | 53篇 |
2018年 | 33篇 |
2017年 | 29篇 |
2016年 | 110篇 |
2015年 | 97篇 |
2014年 | 93篇 |
2013年 | 175篇 |
2012年 | 156篇 |
2011年 | 186篇 |
2010年 | 131篇 |
2009年 | 117篇 |
2008年 | 183篇 |
2007年 | 196篇 |
2006年 | 173篇 |
2005年 | 167篇 |
2004年 | 177篇 |
2003年 | 129篇 |
2002年 | 132篇 |
2001年 | 75篇 |
2000年 | 58篇 |
1999年 | 64篇 |
1998年 | 68篇 |
1997年 | 63篇 |
1996年 | 69篇 |
1995年 | 60篇 |
1994年 | 64篇 |
1993年 | 54篇 |
1992年 | 49篇 |
1991年 | 38篇 |
1990年 | 27篇 |
1989年 | 66篇 |
1988年 | 57篇 |
1987年 | 64篇 |
1986年 | 43篇 |
1985年 | 42篇 |
1984年 | 54篇 |
1983年 | 43篇 |
1982年 | 57篇 |
1981年 | 49篇 |
1980年 | 50篇 |
1979年 | 40篇 |
1978年 | 27篇 |
1977年 | 38篇 |
1976年 | 22篇 |
1975年 | 30篇 |
1973年 | 25篇 |
排序方式: 共有3981条查询结果,搜索用时 15 毫秒
51.
52.
Florian Capito Romas Skudas Bernd Stanislawski Harald Kolmar 《Colloid and polymer science》2013,291(7):1759-1769
The effect of low ionic strength leading to reduced polyelectrolyte–protein interactions has been shown by in silico and in vitro experiments, suggesting polyelectrolyte rigidity increasing at low ionic strength, thus leading to reduced interactions with proteins. This contribution elucidates polyelectrolyte–protein precipitation in the 0–2.6-mS?cm?1 ionic strength regime with polyelectrolyte rigidity determinations, using viscosimetry at these conditions, also considering protein charge distributions, using different proteins. Precipitation yields increased from 5 to 40 % at low ionic strength to up to 90 % at intermediate ionic strength, depending on protein and polyelectrolyte type, using lysozyme and three different monoclonal antibodies. Comparing precipitation behavior of the monoclonal antibodies, a qualitative correlation between required polyelectrolyte flexibility to enhance protein precipitation and protein average charge as well as hydrophobicity of the antibodies was discovered. Antibodies with lower average charge and less hydrophobicity required more flexible polyelectrolytes to enhance precipitation behavior by allowing interaction of the polyelectrolytes with proteins, attaching to positively charged protein patches while “circumnavigating” negatively charged protein areas. In contrast, antibodies with higher protein average charge showed increasing precipitation yields up to 90 % already at lower ionic strength, associated with then more rigid polyelectrolyte structures. Therefore, designing polyelectrolytes with specific chain flexibility could help to improve precipitation behavior toward specific target proteins in polyelectrolyte-driven purification techniques. 相似文献
53.
JPC – Journal of Planar Chromatography – Modern TLC - 相似文献
54.
55.
Palladium, vapor-deposited at room temperature on a reduced SnO2(101) surface, forms one-dimensional islands, one atomic layer high, 5 A wide, and up to 350 A long. Scanning tunneling microscopy shows that neighboring islands do not merge. First-principles calculations reveal the atomistic processes that lead to this, for metal oxide substrates unusual, overlayer growth. Formation of 1D islands is mediated by a large anisotropy in surface diffusion, strong Pd-Sn interaction, and the lack of stable binding sites at the sides of the Pd islands. Nucleation is defect mediated, and the initial nucleation site determines the width of the resulting nanocluster. 相似文献
56.
We show that the particle-hole conjugate of the Pfaffian state-or "anti-Pfaffian" state-is in a different universality class from the Pfaffian state, with different topological order. The two states can be distinguished easily by their edge physics: their edges differ in both their thermal Hall conductance and their tunneling exponents. At the same time, the two states are exactly degenerate in energy for a nu=5/2 quantum Hall system in the idealized limit of zero Landau level mixing. Thus, both are good candidates for the observed sigma_{xy}=5/2(e;{2}/h) quantum Hall plateau. 相似文献
57.
In most of the mass range encompassed by the limits from the direct search and the electroweak precision tests, the Higgs boson of the standard model preferably decays to bottom quarks. We present, in analytic form, the dominant two-loop electroweak correction, of O(GF2mt4), to the partial width of this decay. It amplifies the familiar enhancement due to the O(GFmt2) one-loop correction by about +16% and thus more than compensates the screening by about -8% through strong-interaction effects of order O(alphasGFmt2). 相似文献
58.
Stange CF Spott O Apelt B Russow RW 《Isotopes in environmental and health studies》2007,43(3):227-236
On the basis of the principle of reaction continuous-flow quadrupole mass spectrometry, an automated sample preparation unit for inorganic nitrogen (SPIN) species was developed and coupled to a quadrupole Mass Spectrometer (MAS). The SPINMAS technique was designed for an automated, sensitive, and rapid determination of 15N abundance and concentration of a wide variety of N-species involved in nitrogen cycling (e.g. NH4+, NO3-, NH2OH etc.). In this paper, the SPINMAS technique is evaluated with regard to the determination of 15N abundance and concentration of the most fundamental inorganic nitrogen compounds in ecosystems such as NH4+, NO2-, and NO3-. The presented paper describes the newly developed system in detail and demonstrates the general applicability of the system. For a precise determination of 15N abundance and concentration, a minimum total N-amount of 10 microg NH4+ - N, 0.03 microg NO2- - N, or 0.3 microg NO3- - N has to be supplied. Currently, the SPINMAS technique represents the most rapid and only fully automated all-round method for a simultaneous determination of 15N abundance and total N-amount of NH4+, NO2-, or NO3- in aqueous samples. 相似文献
59.
Ceren Kütahya Nicolai Meckbach Veronika Strehmel Bernd Strehmel 《Journal of polymer science. Part A, Polymer chemistry》2021,59(18):2023-2035
Cyanines with heptamethine pattern namely 5-(6-(2-(3-ethyl-1,1-dimethyl-1H-benzo[e]indol-2(3H)-ylidene)ethylidene)-2-(2-(3-ethyl-1,1-dimethyl-1H-benzo[e]indol-3-ium-2yl) vinyl) cyclo-hex-1-en-1-yl)-1,3-dimethyl-2,6-dioxo-1,2,3,6-tetrahydropyrimidin-4-olate comprising a barbiturate group facilitate controlled radical polymerization using FeBr3 in the ppm range applying radiation at 790 nm. Tris(4-methoylphenyl)phosphine, Tris(2-pyridylmethyl)amine or tetrabutylammonium bromide served as ligand. The latter showed the best performance resulting in a system needing no amino nitrogen for photo-ATRP. Ethyl α-bromophenylacetate worked as initiator. The cyanine interacts with FeBr3 resulting in a new absorption band at 877 nm that also resulted in formation of polymer exhibiting similar molecular weight but higher dispersity compared to that obtained by 790 nm radiation by exposure with a light-emitting diode (LED) emitting at 870 nm. This explains the reactivity of the system while other cyanines such as 2-[2-[3-[2-(1,3-Dihydro-1,3,3-trimethyl-2H-indol-2-ylidene)-ethylidene]-2-(1-phenyl- 1H-tetrazol-5-ylsulfanyl)-1-cyclohexen-1-yl]-ethenyl]-1,3,3-trimethyl-3H-indolium chloride showed no activity by exposure at 790 nm in combination with FeBr3/Br−. Controlled radical polymerization was confirmed by successful chain extension and block copolymerization experiments resulting in polymers, which exhibit a dispersity of about 1.3. Interestingly, the new system comprising the aforementioned barbiturate substituted cyanine, FeBr3/Br− and ethyl α-bromophenylacetate showed a certain oxygen tolerance. Polymers obtained exhibited similar dispersity as those made under inert conditions. 相似文献