全文获取类型
收费全文 | 2428篇 |
免费 | 67篇 |
国内免费 | 12篇 |
专业分类
化学 | 1720篇 |
晶体学 | 13篇 |
力学 | 35篇 |
数学 | 475篇 |
物理学 | 264篇 |
出版年
2023年 | 14篇 |
2022年 | 23篇 |
2021年 | 38篇 |
2020年 | 46篇 |
2019年 | 47篇 |
2018年 | 24篇 |
2017年 | 20篇 |
2016年 | 68篇 |
2015年 | 42篇 |
2014年 | 52篇 |
2013年 | 82篇 |
2012年 | 111篇 |
2011年 | 109篇 |
2010年 | 57篇 |
2009年 | 82篇 |
2008年 | 134篇 |
2007年 | 110篇 |
2006年 | 113篇 |
2005年 | 101篇 |
2004年 | 91篇 |
2003年 | 94篇 |
2002年 | 93篇 |
2001年 | 42篇 |
2000年 | 64篇 |
1999年 | 42篇 |
1998年 | 47篇 |
1997年 | 51篇 |
1996年 | 48篇 |
1995年 | 36篇 |
1994年 | 44篇 |
1993年 | 33篇 |
1992年 | 25篇 |
1991年 | 35篇 |
1990年 | 26篇 |
1989年 | 22篇 |
1988年 | 32篇 |
1987年 | 25篇 |
1986年 | 17篇 |
1985年 | 29篇 |
1984年 | 42篇 |
1983年 | 26篇 |
1982年 | 38篇 |
1981年 | 33篇 |
1980年 | 28篇 |
1979年 | 17篇 |
1978年 | 16篇 |
1977年 | 20篇 |
1976年 | 21篇 |
1975年 | 10篇 |
1973年 | 8篇 |
排序方式: 共有2507条查询结果,搜索用时 15 毫秒
51.
Norbert Kalus 《Journal of statistical physics》1981,25(4):635-643
We describe a new class of single spin measures on then-dimensional sphereS
r
n
of radiusr (n 4) for which Lebowitz-type [J. Lebowitz,J. Stat. Phys.
16:463 (1977)] inequalities hold. This is achieved by an appropriate parametrization ofS
r
n
. The above class includes the uniform measures onxs Rn ¦x¦ r for any 0 p r. The second topic of this paper is an abstract formulation of the first Griffiths inequality [R. B. Griffiths,J. Math. Phys.
8:478 (1967)] and the underlying symmetry property. 相似文献
52.
We investigate the nature of the phase transition from the superconducting to the uniformly ordered magnetic phase in ferromagnetic superconductors by renormalization group methods. For this purpose Halperin, Lubensky, Ma's application of the-expansion to pure superconductors is extended to include the influence of magnetic order as well. Our treatment shows that in the vicinity of the ferromagnetic to superconducting phase-boundary critical fluctuations of the magnetization are absorbed into fluctuations of the magnetic field. As a consequence the transition always is first order. An additional indication to the dominance of electromagnetic effects is the irrelevance of the coupling corresponding to spin flip scattering. 相似文献
53.
Norbert Köhler 《manuscripta mathematica》1976,19(2):151-164
The following statements are valid:The complete directed graph ¯Kn, n1 (mod 2p), is decomposable into directed 2p-cycles.The complete directed bipartite graph ¯Km,n is decomposable into 2p-cycles if p is a divisor of m and np.If p is a prime, then this condition is necessary, too.The complete directed graph ¯Kn, n12, is decomposable into 6-cycles if and only if 6 相似文献
54.
Quentin Coquerel Claire Legendre Jacinthe Frangieh Stephan De Waard Jrme Montnach Leos Cmarko Joseph Khoury Charifat Said Hassane Dimitri Brard Benjamin Siegler Ziad Fajloun Harold De Pomyers Kamel Mabrouk Norbert Weiss Daniel Henrion Pascal Richomme Csar Mattei Michel De Waard Anne-Marie Le Ray Christian Legros 《Molecules (Basel, Switzerland)》2022,27(13)
Voltage-gated Na+ (NaV) channels are significant therapeutic targets for the treatment of cardiac and neurological disorders, thus promoting the search for novel NaV channel ligands. With the objective of discovering new blockers of NaV channel ligands, we screened an In-House vegetal alkaloid library using fluorescence cell-based assays. We screened 62 isoquinoline alkaloids (IA) for their ability to decrease the FRET signal of voltage sensor probes (VSP), which were induced by the activation of NaV channels with batrachotoxin (BTX) in GH3b6 cells. This led to the selection of five IA: liriodenine, oxostephanine, thalmiculine, protopine, and bebeerine, inhibiting the BTX-induced VSP signal with micromolar IC50. These five alkaloids were then assayed using the Na+ fluorescent probe ANG-2 and the patch-clamp technique. Only oxostephanine and liriodenine were able to inhibit the BTX-induced ANG-2 signal in HEK293-hNaV1.3 cells. Indeed, liriodenine and oxostephanine decreased the effects of BTX on Na+ currents elicited by the hNaV1.3 channel, suggesting that conformation change induced by BTX binding could induce a bias in fluorescent assays. However, among the five IA selected in the VSP assay, only bebeerine exhibited strong inhibitory effects against Na+ currents elicited by the hNav1.2 and hNav1.6 channels, with IC50 values below 10 µM. So far, bebeerine is the first BBIQ to have been reported to block NaV channels, with promising therapeutical applications. 相似文献
55.
Mthandazo Dube Dayma Llanes Mohamad Saoud Robert Rennert Peter Imming Ccile Hberli Jennifer Keiser Norbert Arnold 《Molecules (Basel, Switzerland)》2022,27(9)
Neglected tropical diseases affect the world’s poorest populations with soil-transmitted helminthiasis and schistosomiasis being among the most prevalent ones. Mass drug administration is currently the most important control measure, but the use of the few available drugs is giving rise to increased resistance of the parasites to the drugs. Different approaches are needed to come up with new therapeutic agents against these helminths. Fungi are a source of secondary metabolites, but most fungi remain largely uninvestigated as anthelmintics. In this report, the anthelmintic activity of Albatrellus confluens against Caenorhabditis elegans was investigated using bio-assay guided isolation. Grifolin (1) and neogrifolin (2) were identified as responsible for the anthelmintic activity. Derivatives 4–6 were synthesized to investigate the effect of varying the prenyl chain length on anthelmintic activity. The isolated compounds 1 and 2 and synthetic derivatives 4–6, as well as their educts 7–10, were tested against Schistosoma mansoni (adult and newly transformed schistosomula), Strongyloides ratti, Heligmosomoides polygyrus, Necator americanus, and Ancylostoma ceylanicum. Prenyl-2-orcinol (4) and geranylgeranyl-2-orcinol (6) showed promising activity against newly transformed schistosomula. The compounds 1, 2, 4, 5, and 6 were also screened for antiproliferative or cytotoxic activity against two human cancer lines, viz. prostate adenocarcinoma cells (PC-3) and colorectal adenocarcinoma cells (HT-29). Compound 6 was determined to be the most effective against both cell lines with IC50 values of 16.1 µM in PC-3 prostate cells and 33.7 µM in HT-29 colorectal cells. 相似文献
56.
Ulrich A. HarrÉus Barbara C. Wallner Ernst R. Kastenbauer Norbert H. Kleinsasser 《International journal of environmental analytical chemistry》2013,93(6):395-401
Surfactants, which are prevalent at industrial sites and in the environment generally, are potential risk factors in human carcinogenesis. The widespread industrial use of surfactants such as 4-alkylphenol ethoxylates and their prevalence in many cleaning products have provoked studies about surfactant concentrations in water and their toxicity levels. Up to now, these substances have mainly been tested on aquatic organisms. Though tests on human cell lines are rare. The alkaline Comet assay was performed to evaluate the genotoxicity of 4-nonylphenol ethoxylate, a biodegradable product of 4-alkylphenol ethoxylate, in human lymphocytes. Concentrations tested ranged from 0.15 to 150 µg/mL. Test concentrations of 10 to 15 µg/mL caused an increase level of DNA migration in human cells, but without inducing excessive toxicity (viability > 80%). Though induced levels of DNA migration starting at concentrations of 30 µg/mL may have been due to excessive levels of cytotoxicity (viability < 70%). Based on these data, 4-nonylphenol ethoxylate can induce DNA damage in human lymphocytes but at higher concentrations than are normally found in river or drinking water. However, considering the prevalence of surfactants, the measured genotoxicity of these substances is of concern. Further investigations on human target cells are necessary to evaluate the carcinogenic impact of surfactants and reconsider their environmental acceptance. 相似文献
57.
58.
In the paper results of the investigation of the influence of electric properties of the environment surrounding LiNbO3 crystals on photorefractive effect induced in these crystals by Gaussian Ar+ laser beam with various intensities are presented. We show spatial and temporal dependences of changes of the refractive index obtained experimentally in LiNbO3: Fe and LiNbO3: Fe:Mn samples surrounded by media with different electric conductivities and different permittivities (water, air, water solution of CaCl2). The space and time dependences of the refractive index changes induced by the Ar+ laser beam are observed by means of the Mach–Zehnder interferometer using light from HeNe laser. The experimentally obtained results are in a good agreement with those following from numerical calculations using the manifold mirroring method. The agreement between calculated and experimental results indicates that the polarization charge at the photorefractive crystal/surrounding medium boundary significantly influences the photorefractive process in the crystal. The experimentally observed slow spontaneous decrease of the refractive index change in a sample placed into a slightly conducting medium (air) after switching off the beam also indicates that the polarization charge in the sample's surroundings affects the photorefraction. 相似文献
59.