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991.
In this paper, we apply finite element Galerkin method to a single-phase linear Stefan problem with a forcing term. We apply the extrapolated Crank-Nicolson method to construct the fully discrete approximation and we derive optimal error estimates in the temporal direction inL 2,H 1 spaces. 相似文献
992.
Kyung Ho Choi Kyung Hoon Lee Jin Chul Jung 《Journal of polymer science. Part A, Polymer chemistry》2001,39(21):3818-3825
Two series of new poly(amide imide)s having (n‐alkyoxy)phenyloxy side branches with various lengths, poly{p‐phenyleneiminoterephthaloylimino‐p‐phenylene[3,6‐di(n‐alkyloxy)phenyloxy]pyromellitimide}s ( PC m TA s, m = 4, 8, 12) and poly{p‐phenyleneiminosebacoylimino‐p‐phenylene[3,6‐di(n‐alkyloxy)‐phenyloxy]‐ pyromellitimide}s ( PC m SeA s, m = 4, 8, 12), were prepared by condensation of terephthalamide‐N,N′‐4,4′‐dianiline ( TA ) and sebacamide‐N,N′‐4,4′‐dianiline ( SeA ) with 3,6‐di[4‐(n‐alkyloxy)phenyloxy]pyromellitic dianhydrides , respectively. The inherent viscosities of the polymers were in the 0.82–1.20 dL/g range. The polymers were highly soluble in N‐methylpyrolidinone (NMP), even at room temperature and soluble in other polar aprotic solvents on heating. The PC m TA s, which have aromatic backbones, were thermally more stable (431–442 °C) than the PC m SeA s, which have an octamethylene unit in the main chain (407–409 °C). Degradation of weight up to 900 °C corresponded with the loss of side chain contents. The PC m TA s exhibited no phase transition, whereas two endothermic peaks were observed for each of the PC m SeA s. Wide‐angle X‐ray diffractometer investigations revealed that both polymers are amorphous and the n‐alkyloxy side chains are present in a layered structure. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3818–3825, 2001 相似文献
993.
Loon‐Seng Tan Sharon R. Simko Shih Jung Bai Richard A. Vaia Barney E. Taylor Marlene D. Houtz Max D. Alexander Robert J. Spry 《Journal of Polymer Science.Polymer Physics》2001,39(20):2539-2548
As an alternative method for processing polyaniline (PANI) from its conducting (protonated) state, vacuum casting of PANI from a methanesulfonic acid (MSA) solution provided films with electrical conductivity values of about 130–150 S/cm. In addition, we similarly prepared blended films of PANI · MSA and poly(p‐phenylene benzobisthiazole) (PBZT). This process eliminated the need for a subsequent protonation step and had the additional advantage that the conjugated PBZT may provide alternative conducting pathways. Conductivity values of the composite films ranged from 100 pS/cm to 124 S/cm, and the films displayed critical concentration behavior with a PANI threshold concentration of 2.75% and a critical exponent of 4. Transmission electron micrographs displayed phase‐separated regions with PANI forming a continuous network at high concentrations. Thermogravimetric analysis results demonstrated the thermal and thermooxidative stability advantage of the blends due to the PBZT component. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2539–2548, 2001 相似文献
994.
995.
A versatile synthetic method for preparing 4‐hydroxyquinolone and 2‐substituted quinolone compounds from simple benzoic acid derivatives was demonstrated. The synthetic strategies involve the use of well known ethyl acetoacetate synthesis, malonic ester synthesis and reductive cyclization. The key intermediates were keto esters 4a‐e , which could be transformed to 4‐hydroxyquinolones 5a,b or 2‐substituted quinolone ethyl esters 6a‐c depending on the reaction conditions. 4‐Hydroxyquinolone analogues were prepared and investigated for N‐methyl‐D‐aspartate (NMDA) activity in vitro. Among these derivatives, 6,7‐difluoro‐3‐nitro‐4‐hydroxyquinolin‐2(1H)‐one ( 9 ) exhibited moderate activity. 相似文献
996.
C M Jung H C Kwon J J Seo Y Ohizumi K Matsunaga S Saito K R Lee 《Chemical & pharmaceutical bulletin》2001,49(7):912-914
The aerial part of Aster scaber Thunb. (Asteraceae) yielded two new monoterpene peroxide glycosides, (3S)-3-O-(3',4'-diangeloyl-beta-D-glucopyranosyloxy)-7-hydroperoxy-3,7-dimethylocta-1,5-diene (1) and (3S)-3-O-(3',4'-diangeloyl-beta-D-glucopyranosyloxy)-6-hydroperoxy-3,7-dimethylocta-1,7-diene (2), and five known compounds, alpha-spinasterol (3), germacra-4(15),5,10(14)-triene-1-beta-ol (4), 7-methoxy-4(15)-oppositen-1-beta-ol (5), 6alpha-methoxy-4(15)-eudesmane-1beta-ol (6) and alpha-spinasterol 3-O-beta-D-glucopyranoside (7). The structures were established by chemical and spectroscopic methods. 相似文献
997.
Bok Lyeon Lee Yoon Hee Lee Il Yoon Jong Hwa Jung Ki-Min Park Shim Sung Lee 《Microchemical Journal》2001,68(2-3)
Extraction and transport behaviors of isomeric oxathia macrocycles (L2, ortho-; L3, meta- and L4, para-isomer) and their structure related open-chain compound (L1) towards Ag(I) picrate have been examined. From the plot of log (DAg(I)/[pic−]) vs. log [L]0 for all of the ionophores were linear with slope near unity, thereby confirming the 1:1:1 complex formations of Ag(I)/ligand/picrate ion to be extracted into the dichloromethane phase. The extractability of an acyclic ionophore was superior to those of the corresponding cyclic ones. In membrane transport experiments, the slow rate of release of Ag(I) from the membrane into the receiving phase seems to be responsible for lower transport efficiency. Upon addition of sodium thiosulfate as a stripping reagent in receiving phase, the efficiency of transport is significantly enhanced in the order of L1 (acyclic)>L2 (ortho-)>L3 (meta-)>L4 (para-) in accordance with those of log Kex values. It is hypothesized that the ion-pair complexation of L1 in extraction step would be more favorable in extraction and transport of Ag(I). Its structure have been confirmed by X-ray diffraction analysis of [Ag(L1)pic], where L1=1,10-bis(mercaptobenzylyl)-4,7-dioxadecane. 相似文献
998.
The polymerisation of styrene in lyotropic liquid-crystalline (LC) phases of dioctadecyldimethylammonium bromide (DODAB)
in water is explored. Amphiphile concentrations between 20 and 50 wt % are employed. The study is set out as a model study
for polymerisation reactions in nonstabilised, nonfunctional bilayer systems. X-ray characterisation was used to assess the
phase behaviour of the lyotropic mesophases before, during and after polymerisation. The DODAB/water system forms the lamellar
phase within the concentration range considered. Addition of styrene to the lamellar phase of DODAB at an equimolar ratio
induces a phase shift to a bicontinuous cubic phase at elevated temperatures near the phase-transition temperature. Upon polymerisation
within this cubic phase, the phase structure is maintained if the system is kept at constant temperature; however, if the
polymer/amphiphile phase is cooled, the lamellar phase, being typical of the DODAB/water system, is restored. It is concluded
that, as a result of phase separation between the polymer and the amphiphile phase, the polymerisation in lyotropic LC phases
does not provide a stable copy of the templating amphiphile phase. This is in analogy to the observations for polymerisations
in other lyotropic phases.
Received: 16 March 2000 Accepted: 1 July 2000 相似文献
999.
Jun‐Gill Kang Jung‐Pyo Hong Il‐Hwan Suh 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(2):231-232
In the crystal structure of the title compound, 4‐cyano‐N‐(4‐methoxybenzylidene)phenylamine N‐oxide, C15H12N2O2, the 4‐methoxyphenyl is approximately coplanar with the nitrone moiety but significantly rotated with respect to the 4‐cyanophenyl moiety. The extent of this rotation is significantly different for the two crystallographically independent molecules of the asymmetric unit [dihedral angles of 19.4 (1) and 26.5 (1)°]. The geometry about the C=N bond is Z. The two molecules are related to one another by a pseudo inversion centre. 相似文献
1000.
Kyung‐Lae Park Byoung‐Gi Moon Sang‐Hun Jung Jin‐Gyu Kim Il‐Hwan Suh 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(10):1247-1250
The title compound, (S)‐(+)‐4‐[5‐(2‐oxo‐4,5‐dihydroimidazol‐1‐ylsulfonyl)indolin‐1‐ylcarbonyl]anilinium chloride (S)‐(+)‐1‐[1‐(4‐aminobenzoyl)indoline‐5‐sulfonyl]‐4‐phenyl‐4,5‐dihydroimidazol‐2‐one, C24H23N4O4S+·Cl?·C24H22N4O4S, crystallizes in space group C2 from a CH3OH/CH2Cl2 solution. In the crystal structure, there are two different conformers with their terminal C6 aromatic rings mutually oriented at angles of 67.69 (14) and 61.16 (15)°. The distances of the terminal N atoms (of the two conformers) from the chloride ion are 3.110 (4) and 3.502 (4) Å. There are eight distinct hydrogen bonds, i.e. four N—H?Cl, three N—H?O and one N—H?N, with one N—H group involved in a bifurcated hydrogen bond with two acceptors sharing the H atom. C—H?O contacts assist in the overall hydrogen‐bonding process. 相似文献