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181.
Tomasz Radzik 《Mathematical Programming》1996,78(1):43-58
In this paper we consider an optimization version of the multicommodity flow problem which is known as the maximum concurrent
flow problem. We show that an approximate solution to this problem can be computed deterministically using O(k(ε
−2 + logk) logn) 1-commodity minimum-cost flow computations, wherek is the number of commodities,n is the number of nodes, andε is the desired precision. We obtain this bound by proving that in the randomized algorithm developed by Leighton et al. (1995)
the random selection of commodities can be replaced by the deterministic round-robin without increasing the total running
time. Our bound significantly improves the previously known deterministic upper bounds and matches the best known randomized
upper bound for the approximation concurrent flow problem.
A preliminary version of this paper appeared inProceedings of the 6th ACM-SIAM Symposium on Discrete Algorithms, San Francisco CA, 1995, pp. 486–492. 相似文献
182.
In this paper we give necessary and sufficient conditions for blow-up of solutions for a particular class of nonlinear Volterra equations. We also give some examples. 相似文献
183.
Andrzej Wolkenberg Tomasz Przes?awski Kazimierz Regiński 《Journal of Physics and Chemistry of Solids》2003,64(1):7-14
At low temperatures In0.53Ga0.47As samples show an increase of carrier concentration, which can be explained in terms of a two carriers transport model. This type of problem exists since the beginning of the semiconductor era, dating back to monocrystalline germanium.We propose that in all the investigated layers, there are X atoms or charged dislocations in the region of the first monolayers, which are built in during epitaxial growth. The layers were intentionally undoped. They form an impurity band in which low mobility carriers dominate over the localised electron scattering due to the s-d exchange interaction. These carriers do not freeze out at liquid helium temperature and give rise to two transport media for electrons; a conduction band at higher temperatures and an impurity band at lower temperatures. The electron which fall down onto the previously ionised X atoms, then move by thermally activated hopping. We show that the two carriers model for In0.53Ga0.47As epitaxial layers are confirmed by the carrier concentration-temperature, carrier concentration-magnetic field, resistivity-magnetic field behaviour, and also by YKA theory also. The differences between the two transport models are so distinctive that observed phenomena may exist. This paper presents experimental results, which constitute comprehensive evidence for the complicated structure of the semiconductor epitaxial layers on the sample of n-type In0.53Ga0.47As/InP layer with n=2.2×1015/cm3. 相似文献
184.
We show that every 3‐connected claw‐free graph which contains no induced copy of P11 is hamiltonian. Since there exist non‐hamiltonian 3‐connected claw‐free graphs without induced copies of P12 this result is, in a way, best possible. © 2004 Wiley Periodicals, Inc. J Graph Theory 47: 111–121, 2004 相似文献
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187.
Hydrogen Storage Materials: Room‐Temperature Wet‐Chemistry Approach toward Mixed‐Metal Borohydrides
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Dr. Tomasz Jaroń Piotr A. Orłowski Wojciech Wegner Dr. Karol J. Fijałkowski Dr. Piotr J. Leszczyński Prof. Wojciech Grochala 《Angewandte Chemie (International ed. in English)》2015,54(4):1236-1239
The poor kinetics of hydrogen evolution and the irreversibility of the hydrogen discharge hamper the use of transition metal borohydrides as hydrogen storage materials, and the drawbacks of current synthetic methods obstruct the exploration of these systems. A wet‐chemistry approach, which is based on solvent‐mediated metathesis reactions of precursors containing bulky organic cations and weakly coordinating anions, leads to mixed‐metal borohydrides that contain only a small amount of “dead mass”. The applicability of this method is exemplified by Li[Zn2(BH4)5] and M[Zn(BH4)3] salts (M=Na, K), and its extension to other systems is discussed. 相似文献
188.
Tomasz Rojek Tadeusz Lis Ewa Matczak‐Jon 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(7):593-597
The asymmetric unit of the title salt, C12H24N+·C2H2BrO2−, contains a dicyclohexylammonium cation connected to a bromoacetate anion by means of an N—H...O hydrogen bond. In the crystal, the ion pairs assemble via N—H...O interactions, forming zigzag infinite chains parallel to the c axis with the (...H—N—H...O—C—O...)n motif that is considered to be a prerequisite for ensuring gelation properties of secondary ammonium monocarboxylate salts. The title salt was characterized by FT–IR, X‐ray powder diffraction (XRPD), TG–DTA and 1H NMR spectroscopy in solution. Gelation experiments revealed that dicyclohexylammonium bromoacetate forms molecular gels with dimethylformamide and dimethyl sulfoxide. Scanning electron microscopy (SEM) was used to reveal morphological features of dried gels. 相似文献
189.
Tomasz Pospieszny 《Helvetica chimica acta》2015,98(10):1337-1350
A new steroid conjugates have been obtained from bile acids and sterol derivatives using ‘click chemistry’. Intermolecular 1,3‐dipolar cycloaddition of the propargyl ester of bile acids (lithocholic, deoxycholic, and cholic acid) and azide derivatives of sterols (ergosterol and cholesterol) gave a new bile acid? sterol conjugates linked with a 1,2,3‐triazole ring. The structures of all products were confirmed by spectroscopic (1H‐ and 13C‐NMR, and FT‐IR) analyses, mass spectrometry (ESI‐MS), and in silico biological activity evaluation methods (PASS), as well as PM5 semiempirical methods. 相似文献
190.
Synthesis of β-cyclodextrin-lysozyme conjugates and their physicochemical and biochemical properties
Tomasz Marek Goszczyński Maciej Gawłowski Beata Girek Konrad Kowalski Janusz Boratyński Tomasz Girek 《Journal of inclusion phenomena and macrocyclic chemistry》2017,87(3-4):341-348
Recently a great interest in the field of protein engineering and the design of innovative drug delivery systems employing specific ligands such as cyclodextrins is observed. The paper reports the solid state, thermal method for protein coupling with β-cyclodextrin and the physicochemical and biological properties of the obtained conjugates. The structure of the obtained conjugates was investigated via liquid chromatography-mass spectrometry, dynamic light scattering and circular dichroism analysis. The presented conjugates were biologically active and covalently bound β-cyclodextrin preserved the ability to form inclusion complexes with the model compound. This report demonstrates the great potential of cyclodextrin as a modifying unit that can be used to modulate the properties of therapeutic proteins, additionally giving such conjugates the possibility to transport many therapeutic substances in the form of inclusion complexes. In addition, the paper presents the potential of protein-cyclodextrin conjugates to construct innovative bioactive molecules for biological and medical applications. 相似文献