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991.
Particularism renders the options for a sound moral epistemology few and the prospects dim. One leading approach treats basic
knowledge of particular cases as derivable from an a priori moral principle and a posteriori knowledge of the contingent non-moral
facts to which the principle applies. Particularists must forgo this approach because it requires principles. Yet a purely
a posteriori moral epistemology is also implausible, especially when combined with particularism. Particularists such as Jonathan
Dancy are thus led to the view that our basic moral knowledge is a priori knowledge of contingent moral facts. We argue that
this epistemology is unsound. While some cases of a priori knowledge of (even deeply) contingent facts may be defensible,
they are not sufficient for particularist purposes. Moreover, neither Dancy’s appeal to the distinction between positive and
negative dependence nor his discussion of intuitive examples provides sufficient support for this epistemology. 相似文献
992.
Fluctuation signals of the QCD phase transition in nuclear collisions can be dissipated due to diffusion. Diffusive modes in the standard formulation of relativistic hydrodynamics propagate with infinite speed, violating causality. We develop a causal diffusion equation study the dissipation of net-charge fluctuations. We find that causality restricts the extent to which diffusion can dissipate these fluctuations. 相似文献
993.
The low index Magnesium hydride surfaces, MgH2(0 0 1) and MgH2(1 1 0), have been studied by ab intio Density Functional Theory (DFT) calculations. It was found that the MgH2(1 1 0) surface is more stable than MgH2(0 0 1) surface, which is in good agreement with the experimental observation. The H2 desorption barriers vary depending on the crystalline surfaces that are exposed and also the specific H atom sites involved - they are found to be generally high, due to the thermodynamic stability of the MgH2 system, and are larger for the MgH2(0 0 1) surface. The pathway for recombinative desorption of one in-plane and one bridging H atom from the MgH2(1 1 0) surface was found to be the lowest energy barrier amongst those computed (172 KJ/mol) and is in good agreement with the experimental estimates. 相似文献
994.
Jerry Rhee Talisa Mohammad Nejad Olivier Comets Sean Flannery Eine Begum Gulsoy Philip Iannaccone Craig Foster 《Complexity》2015,20(3):22-38
Why do mouse corneal epithelial cells display spiraling patterns? We want to provide an explanation for this curious phenomenon by applying an idealized problem solving process. Specifically, we applied complementary line‐fitting methods to measure transgenic epithelial reporter expression arrangements displayed on three mature, live enucleated globes to clarify the problem. Two prominent logarithmic curves were discovered, one of which displayed the ? ratio, an indicator of an optimal configuration in phyllotactic systems. We then utilized two different computational approaches to expose our current understanding of the behavior. In one procedure, which involved an isotropic mechanics‐based finite element method, we successfully produced logarithmic spiral curves of maximum shear strain based pathlines but computed dimensions displayed pitch angles of 35° (? spiral is ~17°), which was altered when we fitted the model with published measurements of coarse collagen orientations. We then used model‐based reasoning in context of Peircean abduction to select a working hypothesis. Our work serves as a concise example of applying a scientific habit of mind and illustrates nuances of executing a common method to doing integrative science. © 2014 Wiley Periodicals, Inc. Complexity 20: 22–38, 2015 相似文献
995.
A computational study of model halogen-bonded FCl?…?YZ dimers and FX′?…?FCl?…?YZ (FX′ = FH, FCl, F2Be; YZ = BF, CO, N2) trimers was undertaken at the MP2/6-311++G (2d, 2p) level of theory. Three different trimer arrangements are possible and the cooperative effect of hydrogen-, halogen- and beryllium-bonding in each of these trimers was assessed relative to the FCl?…?YZ dimer. It was found that the beryllium bond has the largest cooperative effect, while the halogen bond has the smallest, with the hydrogen bond being intermediate between the other two interactions. Interesting trends in selected properties were identified and discussed. 相似文献
996.
Iryna O. Lebedyeva Sean M. Sileno Kunal Patel Ion Ghiviriga Peter J. Steel Alan R. Katritzky 《Central European Journal of Chemistry》2013,11(6):1019-1022
Amination by organic azides has been carried out to provide aminobarbiturates by fusion of a triazole ring to the 5,6-positions of barbituric acid followed by cleavage and thermal elimination of nitrogen, whereas aza-Wittig reaction gave phosphoranylidene barbituric acid salts. 相似文献
997.
Shasha Li Sean A. Newmister Andrew N. Lowell Jiachen Zi Callie R. Chappell Fengan Yu Robert M. Hohlman Jimmy Orjala Robert M. Williams David H. Sherman 《Angewandte Chemie (International ed. in English)》2020,59(21):8166-8172
Stereospecific polycyclic core formation of hapalindoles and fischerindoles is controlled by Stig cyclases through a three‐step cascade involving Cope rearrangement, 6‐exo‐trig cyclization, and a final electrophilic aromatic substitution. Reported here is a comprehensive study of all currently annotated Stig cyclases, revealing that these proteins can assemble into heteromeric complexes, induced by Ca2+, to cooperatively control the stereochemistry of hapalindole natural products. 相似文献
998.
Differential Cross Sections and Collision-Induced Rotational Alignment in Inelastic Scattering of NO(X) by Xe
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Mark Brouard Helen Chadwick Sean D.S. Gordon Cornelia G. Heid Balazs Hornung Bethan Nichols Jacek K?os Pablo G. Jambrina F.Javier Aoiz 《化学物理学报(中文版)》2020,33(2):217-233
Fully \begin{document}$ \Lambda $\end{document} -doublet resolved differential cross sections and collision-induced rotational alignment moments have been measured for the NO(X)–Xe collision system at a collision energy of 519 cm\begin{document}$ ^{-1} $\end{document} . The experiments combine initial quantum state selection, employing a hexapole inhomogeneous electric field, with quantum state resolved detection, using (1+1\begin{document}$ ' $\end{document} ) resonantly enhanced multiphoton ionization and velocity map ion imaging. The differential cross sections and polarization dependent differential cross sections are shown to agree well with quantum mechanical scattering calculations performed on ab initio potential energy surfaces [J. K?os et al. J. Chem. Phys. 137 , 014312 (2012)]. By comparison with quasi-classical trajectory calculations, quantum mechanical scattering calculations on a hard-shell potential, and kinematic apse model calculations, the effects of the attractive part of the potential on the measured differential cross sections and collision-induced rotational alignment moments are assessed. 相似文献
999.
Dr. Shasha Li Dr. Sean A. Newmister Dr. Andrew N. Lowell Dr. Jiachen Zi Callie R. Chappell Dr. Fengan Yu Robert M. Hohlman Prof. Jimmy Orjala Prof. Robert M. Williams Prof. David H. Sherman 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(21):8243-8249
Stereospecific polycyclic core formation of hapalindoles and fischerindoles is controlled by Stig cyclases through a three-step cascade involving Cope rearrangement, 6-exo-trig cyclization, and a final electrophilic aromatic substitution. Reported here is a comprehensive study of all currently annotated Stig cyclases, revealing that these proteins can assemble into heteromeric complexes, induced by Ca2+, to cooperatively control the stereochemistry of hapalindole natural products. 相似文献
1000.
Zhenquan Sun Zhuo Shang Nicholas Forelli Kathy Hiu Laam Po Prof. Sheng Chen Prof. Sean F. Brady Prof. Xuechen Li 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(45):20040-20044
The development of novel antibiotics is critical to combating the growing emergence of drug-resistant pathogens. Malacidin A is a new member of the calcium-dependent antibiotic (CDAs) family with activity against antibiotic-resistant pathogens. Its mode of action is distinct from classical CDAs. However, the absolute structure of malacidin A has not been established. Herein, the total syntheses of malacidin A and its analogues are reported by a combination of Fmoc-based solid-phase peptide synthesis (SPPS) and β-hydroxyaspartic acid ligation-mediated peptide cyclization. The total synthesis enabled us to establish the absolute configuration of malacidin A, which is in agreement with those for natural malacidin A confirmed by advanced Marfey's analysis in our study. 相似文献