全文获取类型
收费全文 | 514篇 |
免费 | 1篇 |
国内免费 | 2篇 |
专业分类
化学 | 355篇 |
晶体学 | 2篇 |
力学 | 6篇 |
数学 | 34篇 |
物理学 | 120篇 |
出版年
2022年 | 4篇 |
2021年 | 7篇 |
2020年 | 7篇 |
2019年 | 6篇 |
2017年 | 4篇 |
2015年 | 3篇 |
2014年 | 5篇 |
2013年 | 30篇 |
2012年 | 14篇 |
2011年 | 19篇 |
2010年 | 7篇 |
2009年 | 9篇 |
2008年 | 30篇 |
2007年 | 28篇 |
2006年 | 23篇 |
2005年 | 22篇 |
2004年 | 23篇 |
2003年 | 24篇 |
2002年 | 14篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 16篇 |
1997年 | 9篇 |
1996年 | 17篇 |
1995年 | 9篇 |
1994年 | 6篇 |
1993年 | 9篇 |
1992年 | 3篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 13篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 6篇 |
1979年 | 10篇 |
1978年 | 17篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1975年 | 5篇 |
1973年 | 3篇 |
1972年 | 4篇 |
1969年 | 5篇 |
1962年 | 3篇 |
排序方式: 共有517条查询结果,搜索用时 15 毫秒
1.
Alain Estve Adeline Bail Georges Landa Ahmed Dkhissi Marie Brut Mehdi Djafari Rouhani Jan Sudor Anne-Marie Gu 《Chemical physics》2007,340(1-3):12-16
Possible collapsed forms of poly(N-isopropylacrylamide) molecules are reviewed on the basis of first principle calculations. Various configurations and associated conformations are detailed. The calculated optimized structures exhibit different possibilities of creating networks of intra-molecular bonds of the hydrogen type. We show that the most remarkable one is able to form a local, self-saturated and well ordered helix. We also indicate in which direction the synthesis of the molecule should be oriented to improve its global behavior in term of hydrophobic/hydrophilic behavior. 相似文献
2.
Joaquin Barbera Anne-Marie Levelut Mercedes Marcos Pilar Romero Jose Luis Serrano 《Liquid crystals》1991,10(1):119-126
We present a comparative study of various metallomesogenic complexes, using X-ray diffraction methods. For a given ligand linked to different metal atoms (Cu, Ni, VO), the nature of this central atom influences mainly the magnetic susceptibilities of the mesophases. With different ligands, which keep the close neighbourhood of the metal atom unchanged, the apparent length of the mesogenic unit is longer for short ligands than for longer ones. This unexpected behaviour is qualitatively well explained by taking into account the global shape of the different complexes. 相似文献
3.
We report on the integration of the kinematic dynamo problem in a spherical domain forced by velocity fields that are convective
fluid flows resulting from a bifurcation analysis of the spherical Bénard problem. We derive a code based on generalized spherical
harmonics that ensures a divergence-free magnetic field. We determine the growth or decay of a magnetic field in the kinematic
dynamo equation for various physically relevant velocity fields which are stationary as well as time-periodic and chaotic.
Velocity signals that are produced by heteroclinic cycles are used as an input to an energy-saturated kinematic dynamo equation
that limits the growth of the linearly unstable modes. Preliminary calculations indicate the possibility of reversals of the
magnetic field for this case of forcing.
Received 8 October 1996 and accepted 28 April 1997 相似文献
4.
E. Casarejos P. Armbruster L. Audouin J. Benlliure M. Bernas A. Boudard R. Legrain S. Leray B. Mustapha S. Czajkowski T. Enqvist B. Fernandez J. Pereira M. Pravikoff F. Rejmund K. -H. Schmidt C. Stephan J. Taieb L. Tassan-Got C. Villagrasa C. Volant W. Wlazlo 《Physics of Atomic Nuclei》2003,66(8):1413-1420
The isotopic production cross sections of heavy residues in relativistic heavy-ion collisions have been investigated in inverse kinematics. The primary reaction products were fully identified in mass and atomic number prior to beta decay using the fragment separator FRS. The huge collection of data obtained helps in the understanding of the two main reaction mechanisms involved: fragmentation and fission. These data provide basic information for future radioactive ion beam facilities and for technical applications like intense neutron sources by means of spallation targets. 相似文献
5.
C. Donzaud S. Czajkowski P. Armbruster M. Bernas C. Böckstiegel P. Dessagne H. Geissel E. Hanelt A. Heinz C. Kozhuharov C. Miehé G. Münzenberg M. Pfützner W. Schwab C. Stéphan K. Sümmerer L. Tassan-Got B. Voss 《The European Physical Journal A - Hadrons and Nuclei》1998,1(4):407-426
Projectile fission of 750 AMeV 238U-ions interacting with a Pb target was studied by means of the spectrometer FRS, GSI-Darmstadt. One of the two fission fragments
was detected with a transmission of few percent and identified in mass and charge. Low-energy fission (E* < 25 MeV) events were selected by their magnetic rigidity. Whereas the production of asymmetric fission events is dominated
by the GDR excitation, very asymmetric fission and symmetric fission take place after a GQR or DGDR excitation or after a
nuclear interaction. Cross sections of more than 250 isotopes were measured. Isotopic distributions of low-energy fission
were reconstructed for elements from Se to Te. The fission modes SI, SII and SL were clearly shown in these distributions
and in the mass and TKE distributions. Charge polarization and mass dispersion were deduced for each fission mode. Finally,
the characteristics of the low-energy fission process explain the production rates of neutron-rich species.
Received: 14 July 1997 / Revised version: 6 October 1997 相似文献
6.
A. Türler H. W. Gäggeler D. T. Jost P. Armbruster W. Brüchle H. Folger F. P. Heßberger S. Hofmann G. Münzenberg V. Ninov M. Schädel K. Sümmerer J. V. Kratz U. Scherer 《Zeitschrift für Physik A Hadrons and Nuclei》1988,331(3):363-364
The isotope254No was produced in the fusion reaction48Ca +208Pb. Using the velocity filter SHIP and radiochemical techniques it was found that the nuclide254No with a half-life of 55 s decays byα, EC, and spontaneous-fission. Deduced partial half-lives are (61±2) s forα-decay, (550 ?160 +370 ) s for EC and [2.2 ?1.0 +2.0 ]×104 s for spontaneous fission. 相似文献
7.
Rainer Wolf Anne-Marie Dommrse Hans-Fr. Grützmacher 《Journal of mass spectrometry : JMS》1988,23(1):26-32
The secondary α-carbomethoxybenzyl cations a and the tertiary α-carbomethoxybenzyl cations d have been generated by electron impact-induced fragmentation from appropriately α-substituted methyl phenylacetate and 2-phenylpropionates 1–4. The ions a and d are further examples of destabilized carbenium ions with a push–pull substitution at the carbenium ion centre. The characteristic reaction of these ions is a rearrangement by a 1,2-shift of the methoxy group concomitant to the elimination of CO. This rearrangement reaction is associated with a very large and non-statistical kinetic energy release (a : T 50 = 570 meV; d : T 50 = 760 meV), which is attributed to tight transition states along the reaction coordinates corresponding to the three-membered cyclic oxonium ions b and h, respectively. The tertiary ion d can be distinguished from its more stable isomers f and g by the mass-analysed ion kinetic energy and collisional activation spectra. The investigation of specifically deuterated analogues of ions d and g reveals an isomerization of d to g via a species protonated at the phenyl group but no equilibration between d and g. This isomerization exhibits a large isotope effect for the hydrogen transfer, indicating similar energy barriers for the isomerization and for the CO elimination of d. 相似文献
8.
Depecker G Patino N Di Giorgio C Terreux R Cabrol-Bass D Bailly C Aubertin AM Condom R 《Organic & biomolecular chemistry》2004,2(1):74-79
A cyclic molecule including a hexameric PNA sequence has been designed and synthesized in order to target the TAR RNA loop of HIV-1 through the formation of a "kissing complex". For comparison, its linear analogue has also been investigated. The synthesis of the cyclic and linear PNA has been accomplished following a liquid-phase strategy using mixed PNA and fully N-protected (aminoethylglycinamide) fragments. The interactions of this cyclic PNA and its linear analogue with TAR RNA have been studied and the results indicate clearly that no interaction occurs between the cyclic antisense PNA and TAR RNA, whereas a tenuous interaction has been detected with its linear PNA analogue. 相似文献
9.
Shaping, defined as deformation in combination with gel formation of gelatine and kappa-carrageenan drops in an elongation flow, was studied. The focus was to investigate the possibility of shaping and fixating small drops in the diameter range 20 to 229 mum. In the shaping progress and the influence of experimental properties, the viscosity, temperature, and flow of the deforming fluid were examined on the final drop shape. In the experiments a hot emulsion of an aqueous biopolymer solution in silicone oil was injected into cold silicone oil where a deforming elongation flow field existed. After injection, a temperature decrease in the drops resulted in a gel formation of the biopolymer and a fixation of the deformed drop in the flow. The shape was measured and the effect on the drop aspect ratio was determined by image analysis. Over the total drop diameter range, kappa-carrageenan was more ellipsoid-shaped than gelatine, with a maximum aspect ratio of 6 compared to 4 for gelatine. For small drops, around 22 mum, it is possible to shape kappa-carrageenan, but for gelatine small drops tend to be unaffected. An increase in viscosity, temperature, and flow resulted in an increase in the final fixated shape of the drops. The differences in drop deformation between the biopolymers were explained by drop-viscosity/oil differences and differences in the kinetics of gel formation. The different gel formation kinetics resulted in a short, well-defined, shaping process for kappa-carrageenan, while for gelatine the process was more complex, with both deformation and relaxation present at different stages. 相似文献
10.
Paul Servin Régis Laurent Anne-Marie Caminade Jean-Pierre Majoral 《Tetrahedron letters》2007,48(4):579-583
A series of densely functionalized dendrimers is synthesized using two branched monomers of type AB2 and CD2, in which the A function (NH2) reacts with D (CHO) and the B function (Cl) reacts with C (OH). The reaction has been carried out up to the fourth generation possessing 96 end groups and has been obtained in only four steps. 相似文献