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281.
Ging Ho Hsiue Ying Ling Liu Hsin Hao Liao 《Journal of polymer science. Part A, Polymer chemistry》2001,39(7):986-996
Phosphorus‐containing epoxy‐based epoxy–silica hybrid materials with a nanostructure were obtained from bis(3‐glycidyloxy)phenylphosphine oxide, diaminodiphenylmethane, and tetraethoxysilane in the presence of the catalyst p‐toluenesulfonic acid via an in situ sol–gel process. The silica formed on a nanometer scale in the epoxy resin was characterized with Fourier transform infrared, NMR, and scanning electron microscopy. The glass‐transition temperatures of the hybrid epoxy resins increased with the silica content. The nanometer‐scale silica showed an enhancement effect of improving the flame‐retardant properties of the epoxy resins. The phosphorus–silica synergistic effect on the limited oxygen index (LOI) enhancement was also observed with a high LOI value of 44.5. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 986–996, 2001 相似文献
282.
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
283.
Ye?Mei Caiyi?Wei Yew?Mun?Yip Chun?Ying?Ho John?Z.?H.?Zhang Dawei?ZhangEmail author 《Theoretical chemistry accounts》2012,131(3):1168
Two replica exchange molecular dynamics (REMD) simulations were carried out to study the thermodynamics of a 20-residue Trp-cage
folding based on a newly developed polarized protein-specific charge (PPC). Starting from a fully extended conformation, Trp-cage
native conformation was successfully sampled using REMD based on a 3-step PPC update. Next, the obtained Trp-cage folded conformation
was then used to calculate the PPC in which another REMD was performed to explore the thermodynamic stability of Trp-cage.
The theoretical melting temperature T
m of ≈325 K was found to be in close agreement with experimental melting temperature, T
m of 315 K. This indicates that the PPC was correctly predicting the temperature dependence. The current study provides a direct
proof of how electrostatic polarization affects protein folding. 相似文献
284.
Dong Chan Kim Kyung Ho Yoo Kye Jung Shin Sang Woo Park Dong Jin Kim 《Journal of heterocyclic chemistry》1997,34(1):57-63
The pKa′s of several thiazole heterocyclic compounds have been determined and represent products with significantly high values. Because of their high basicities, sometimes these compounds were able to act as not only nucleophiles but also strong organic bases. 4-Substituted-3-methyl-2-methylimino-Δ4-thiazolines 5a-d reacted with ethyl bromoacetate in refluxing benzene, giving the corresponding N-alkylated salts 8a-d , while the products obtained from the reaction with 2-bromoacetophenone in the presence of base were pyrrolothiazines 10b-d. 相似文献
285.
A variable-low-temperature scanning tunneling microscope (STM) was used to observe oxygen (O2), ethylene (C2H4), and acetylene (C2H2) molecules on a Ag(110) surface and the various complexes that were formed between these two hydrocarbons and oxygen at 13 K. Ethylene molecule(s) were moved to the vicinity of O2 either by STM tunneling electrons at 13 K or thermally at 45 K to form (C2H4)x-O2 (x = 1-4) complexes stabilized by C-H...O hydrogen bonding. Acetylene-oxygen complexes involving one or two acetylene molecules were observed. 相似文献
286.
Phytochemical investigation of Ginkgo biloba (Ginkgoaceae) has resulted in the isolation of two new biflavone glucosides, ginkgetin 7'-O-beta-D-glucopyranoside (1) and isoginkgetin 7-O-beta-D-glucopyranoside (2). The structures were determined on the basis of chemical and spectroscopic evidences. 相似文献
287.
The synthesis and optical properties of a series of benz[f]indenes as new building blocks for electronic and optoelectronic materials are described. 相似文献
288.
Seo YJ Jeon MH Lee JH Lee YJ Youn HJ Ko JH Lee JH 《Experimental & molecular medicine》2005,37(6):624-630
Bis (Bag-3, CAIR), a Bcl-2-interacting protein, promotes the anti-apoptotic activity of Bcl-2 and increased levels of Bis have been observed in several disease models. The involvement of Bcl-2 and some Bcl-2-binding proteins in differentiation has recently been reported. However, the relevance of Bis to cellular differentiation remains unknown. The findings herein show that Bis expression is up-regulated during the differentiation of HL-60 cells. To investigate the effect of Bis expression on differentiation, we established Bis-overexpressing HL-60 cells (HL-60-bis). HL-60-bis cells have a low nuclear: cytoplasmic ratio and indented nucleus in Wright- Giemsa staining, and an increased expression of CD11b in immunofluorescence study, indicating the promotion of differentiation. The overexpression of Bis also resulted in a retarded cell growth rate, accompanied by the accumulation of HL-60 cells at the G0/G1 phase of the cell cycle, which was sustained during the differentiation process. Western blot analysis revealed that the expression of p27, a representative inducer of cell cycle arrest at the G1 phase, was increased 2.5-fold in HL-60-bis cells compared to HL-60-neo cells. These results suggest that the Bis induced growth inhibition of HL-60 cells promotes G0/G1 phase arrest via up-regulation of p27, which seems to be a prerequisite for differentiation. Further studies will be required to define the exact roles of Bis on cellular differentiation more precisely. 相似文献
289.
A general strategy is proposed to assign aliphatic side-chain resonances of large 13C,15N-labeled proteins without deuteration, using 4D 13C,15N-edited NOESY and MQ-(H)CCH-TOCSY experiments on the basis of prior assignments of backbone and 13Cbeta resonances. The strategy has been tested on a 214 residue protein (DdCAD-1) and applied to a chain-selectively 13C,15N-labeled hemoglobin (65 kDa). About 96 and 80% aliphatic side-chain spins in DdCAD-1 and hemoglobin have been assigned, respectively. The strategy proposed here will be very useful for the structure determination and dynamics characterization of large proteins by NMR. 相似文献
290.
A Family of Molecular Sieves Containing Framework‐Bound Organic Structure‐Directing Agents 下载免费PDF全文
Jun Kyu Lee Dr. Jiho Shin Nak Ho Ahn Alessandro Turrina Dr. Min Bum Park Dr. Youngchul Byun Prof. Sung June Cho Prof. Paul A. Wright Prof. Suk Bong Hong 《Angewandte Chemie (International ed. in English)》2015,54(38):11097-11101
Organic structure‐directing agents (OSDAs), such as quaternary ammonium cations and amines, used in the synthesis of zeolites and related crystalline microporous oxides usually end up entrapped inside the void spaces of the crystallized inorganic host lattice. But none of them is known to form direct chemical bonds to the framework of these industrially important catalysts and adsorbents. We demonstrate that ECR‐40, currently regarded as a typical silicoaluminophosphate molecular sieve, constitutes instead a new family of inorganic‐organic hybrid networks in which the OSDAs are covalently bonded to the inorganic framework. ECR‐40 crystallization begins with the formation of an Al–OSDA complex in the liquid phase in which the Al is octahedrally coordinated. This unit is incorporated in the crystallizing ECR‐40. Subsequent removal of framework‐bound OSDAs generates Al‐O‐Al linkages in a fully tetrahedrally coordinated framework. 相似文献