全文获取类型
收费全文 | 3959篇 |
免费 | 87篇 |
国内免费 | 22篇 |
专业分类
化学 | 2540篇 |
晶体学 | 23篇 |
力学 | 159篇 |
数学 | 647篇 |
物理学 | 699篇 |
出版年
2021年 | 27篇 |
2020年 | 31篇 |
2019年 | 33篇 |
2018年 | 39篇 |
2017年 | 38篇 |
2016年 | 61篇 |
2015年 | 73篇 |
2014年 | 86篇 |
2013年 | 229篇 |
2012年 | 170篇 |
2011年 | 200篇 |
2010年 | 124篇 |
2009年 | 116篇 |
2008年 | 172篇 |
2007年 | 165篇 |
2006年 | 177篇 |
2005年 | 196篇 |
2004年 | 158篇 |
2003年 | 144篇 |
2002年 | 122篇 |
2001年 | 45篇 |
2000年 | 57篇 |
1999年 | 33篇 |
1998年 | 31篇 |
1997年 | 67篇 |
1996年 | 66篇 |
1995年 | 63篇 |
1994年 | 52篇 |
1993年 | 57篇 |
1992年 | 47篇 |
1991年 | 49篇 |
1990年 | 37篇 |
1989年 | 39篇 |
1988年 | 32篇 |
1987年 | 28篇 |
1985年 | 77篇 |
1984年 | 59篇 |
1983年 | 50篇 |
1982年 | 63篇 |
1981年 | 72篇 |
1980年 | 53篇 |
1979年 | 66篇 |
1978年 | 68篇 |
1977年 | 78篇 |
1976年 | 52篇 |
1975年 | 53篇 |
1974年 | 50篇 |
1973年 | 37篇 |
1971年 | 36篇 |
1968年 | 27篇 |
排序方式: 共有4068条查询结果,搜索用时 15 毫秒
91.
Nelly Durand Bruno Ameduri Bernard Boutevin 《Journal of polymer science. Part A, Polymer chemistry》2011,49(1):82-92
The synthesis and characterizations of fluorinated telomers based on vinylidene fluoride (VDF) by iodine transfer polymerization (ITP) are presented. These telomers were prepared in the presence of ω‐iodoperfluorinated functional chain transfer agents, C6F13I or C4F9I. ITPs were initiated by thermal decomposition of bis(4‐tert‐butylcyclohexyl) peroxydicarbonate (BBCHPDC), in solution (in the presence of acetonitrile). The obtained telomers were characterized by different analyses such as elemental analyses, nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy, size exclusion chromatography, X‐ray diffraction (XRD), and finally by thermal analyses such as differential scanning calorimetry (DSC) and thermogravimetric analyses. These technical analyses enabled one to assess their chemical structures, various thermal properties, and their crystalline forms. The assignments of the characteristic signals obtained by 19F NMR spectroscopy enabled one to calculate the average degrees of polymerization (DPn) and percentages of ? CH2CF2I end group functionalities that depend on the initiator and the fractionation process after reaction. A good control of polymerization was shown by the absence of reversed ? CH2CF2? CF2CH2? (VDF–VDF dyads) and narrow polydispersity indices (<1.2). The XRD and DSC evidenced the influence of the chain length of the telomers on the crystallinity rate (>70%) and indicated two crystalline forms, α and β, that depended on DPn values. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
92.
93.
Yaniv Almog Bernard Helffer Xing-Bin Pan 《Communications in Mathematical Physics》2010,300(1):147-184
We consider the linearization of the time-dependent Ginzburg-Landau system near the normal state. We assume that an electric
current is applied through the sample, which captures the whole plane, inducing thereby, a magnetic field. We show that independently
of the current, the normal state is always stable. Using Fourier analysis the detailed behaviour of solutions is obtained
as well. Relying on semi-group theory we then obtain the spectral properties of the steady-state elliptic operator. 相似文献
94.
C. Rodriguez N. Bernard C. Julien G. Cuisinaud J. Sassard 《International journal of environmental analytical chemistry》2013,93(1-3):235-255
Abstract A reversed-phase liquid chromatographic technique including a column switching system has been adapted for the routine measurement of catecholamines and their metabolites (14 compounds) in urine. From 1 ml of urine all the compounds and the internal standards were obtained according to combined extraction procedures involving organic solvent, anionic and weakly cationic resins. Finally four extracts (catecholamines, methoxamines, acidic and neutral derivatives) had to be chromatographed throughout a wholly automated apparatus. For each run, the column switching system determined the analytical columns to be used to obtain the separation of the compounds from interferences due to other co-extracted endogenous substances, while the analysis times remained between 20 and 40 min. Such a system allowed the rapid clean-up of columns (in direct- and back-flush mode) carried out between two consecutive injections. By coupling on-line fluorimetric and electro-chemical detections the specificity of the technique could be checked, since the ratio of the responses of both detectors was an index of the purity of the peaks. Finally the advanced automation of the equipment allowed weekly the evaluation of catecholamines and the whole range of their known metabolites in 36 urine samples. 相似文献
95.
Jürg Nussberger Dorette B. Brunner Bernard Waeber Hans R. Brunner 《International journal of environmental analytical chemistry》2013,93(1-3):257-268
Abstract Angiotensin-(1–8)octapeptide (angiotensin II) is the active principle of the reninangiotensin system. Crossreaction of angiotensin II-antisera with inactive precursors and metabolic fragments prevented the specific quantitation of this hormone in biological fluids. Peptide-extraction on bonded-phase silica followed by peptide-separation using isocratic reverse-phase high performance liquid chromatography and subsequent radioimmunoassay rendered possible the octapeptide-specific measurement of angiotensin II in 2 ml plasma with a detection limit of 0.4fmol/ml. The coefficient of variation for intra-assay precision was 0.06 and for inter-assay precision 0.13. 125Iangiotensin II was recovered from plasma by solid-phase extraction to 99±2% (mean ± S.D.). The overall recovery of 5, 10 and 20 fmol unlabeled angiotensin II added to plasma was 80±10%. Plasma concentrations in supine normal humans averaged 4.1 ± 1.6 fmol/ml and were suppressed below the detection limit by angiotensin I converting enzyme inhibition. 相似文献
96.
The preparation of 3-carboxymethylamino (or oxy or thio)-2-aryl (or arylmethyl)-isoindol-1-ones are described from hydroxylactams according to three different pathways. 相似文献
97.
Cuauhtémoc Pozos vázquez Russell Tayouo Christine Joly‐Duhamel Bernard Boutevin 《Journal of polymer science. Part A, Polymer chemistry》2010,48(10):2123-2134
The synthesis and characterization of poly(dimethylsiloxanes) bearing maleimides end‐groups (PDMSM) were carried out through imidization of maleic anhydride with three poly(dimethylsiloxanes) diamines of different molecular weights. Self‐photopolymerization of PDMSM was studied by Real‐Time Fourier Transform infrared spectroscopy (RT‐FTIR) and was possible even without photoinitiator (Darocur 1173). The reaction was found to proceed within seconds upon exposure to ultraviolet (UV) radiation to generate highly crosslinked polymer networks. The results indicated that these polymerizations were less sensitive to oxygen inhibition than the radical processes carried out on conventional UV‐curable acrylate resins. The thermal and mechanical properties of these resulting materials were studied starting from PDMS precursors with different molecular weights. These materials exhibit a low glass transition temperature (100 °C) and a high degradation temperature (400 °C) depending on the density of crosslinking points. These PDMSM are suitable as hydrophobic additives in a coating formulation based on a UV cured polypropylene glycol bismaleimide. Only a very small amount of silicone additives (0.3 wt %) is needed to change the wettability on the surface of the films. The migration of the additive was clearly shown before irradiation by scanning electron microscopy EDX and surface energy measurements. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2123–2134, 2010 相似文献
98.
99.
100.
Proteome analysis of Aspergillus fumigatus identifies glycosylphosphatidylinositol-anchored proteins associated to the cell wall biosynthesis. 总被引:1,自引:0,他引:1
J M Bruneau T Magnin E Tagat R Legrand M Bernard M Diaquin C Fudali J P Latgé 《Electrophoresis》2001,22(13):2812-2823
Previous studies in Aspergillus fumigatus (Mouyna I., Fontaine T., Vai M., Monod M., Fonzi W. A., Diaquin M., Popolo L., Hartland R. P., Latgé J.-P, J. Biol. Chem. 2000, 275, 14882-14889) have shown that a glucanosyltransferase playing an important role in fungal cell wall biosynthesis is glycosylphosphatidylinositol (GPI) anchored to the membrane. To identify other GPI-anchored proteins putatively involved in cell wall biogenesis, a proteomic analysis has been undertaken in A. fumigatus and the protein data were matched with the yeast genomic data. GPI-anchored proteins of A. fumigatus were released from membrane preparation by an endogenous GPI-phospholipase C, purified by liquid chromatography and separated by two-dimensional electrophoresis. They were characterized by their peptide mass fingerprint through matrix-assisted laser desorption/ionization-time of flight-(MALDI-TOF)-mass spectrometry and by internal amino acid sequencing. Nine GPI-anchored proteins were identified in A. fumigatus. Five of them were homologs of putatively GPI-anchored yeast proteins (Csa1p, Crh1p, Crh2p, Ecm33p, Gas1p) of unknown function but shown by gene disruption analysis to play a role in cell wall morphogenesis. In addition, a comparative study performed with chitin synthase and glucanosyl transferase mutants of A. fumigatus showed that a modification of the growth phenotype seen in these mutants was associated to an alteration of the pattern of GPI-anchored proteins. These results suggest that GPI-anchored proteins identified in this study are involved in A. fumigatus cell wall organization. 相似文献