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991.
Chung‐Cheng Chang Kuo‐Ching Yang Jeng‐Gong Guo Leigh‐May Huang Li‐Chyung Wang Gene‐Hsiang Lee Shie‐Ming Peng 《中国化学会会志》2003,50(5):965-971
The insertion reaction of CS2 with Mg(NR2)2 (R= Et, iPr), MgR′2 (R′= Et, Ph) and R″MgBr (R″= iPr, Ph) respectively lead solid products, Mg(S2CNR2)2(THF)n ( 1 : R= Et, n=2; 2 : R= iPr, n=1), Mg(S2C′R)2(THF)2 ( 3 : ′R= Et, 4 : ′R= Ph), BrMg(S2C″R) (THF)3 ( 5 : ″R= iPr, 6 : ″R= Ph) in which the inserted carbon disulfides act as terminal chelating ligands. These compounds were characterized with 1H, 13C NMR, IR spectroscopy, mass spectrometry, elemental analyses, and X‐ray crystallography. 相似文献
992.
Molecular diodes based on conjugated diblock co-oligomers 总被引:2,自引:0,他引:2
This report describes synthesis and characterization of a molecular diode based upon a diblock conjugated oligomer system. This system consists of two conjugated blocks with opposite electronic demand. The molecular structure exhibits a built-in electronic asymmetry, much like a semiconductor p-n junction. Electrical measurements by scanning tunneling spectroscopy (STS) clearly revealed a pronounced rectifying effect. Definitive proof for the molecular nature of the rectifying effect in this conjugated diblock molecule is provided by control experiments with a structurally similar reference compound. 相似文献
993.
Lei Liu Wes Lee Mingbin Yuan Chris Acha Michael B. Geherty Brandon Williams Osvaldo Gutierrez 《Chemical science》2020,11(12):3146
Design and implementation of the first (asymmetric) Fe-catalyzed intra- and intermolecular difunctionalization of vinyl cyclopropanes (VCPs) with alkyl halides and aryl Grignard reagents has been realized via a mechanistically driven approach. Mechanistic studies support the diffusion of alkyl radical intermediates out of the solvent cage to participate in an intra- or intermolecular radical cascade with a range of VCPs followed by re-entering the Fe radical cross-coupling cycle to undergo (stereo)selective C(sp2)–C(sp3) bond formation. This work provides a proof-of-concept of the use of vinyl cyclopropanes as synthetically useful 1,5-synthons in Fe-catalyzed conjunctive cross-couplings with alkyl halides and aryl/vinyl Grignard reagents. Overall, we provide new design principles for Fe-mediated radical processes and underscore the potential of using combined computations and experiments to accelerate the development of challenging transformations.Design and implementation of the first (asymmetric) Fe-catalyzed intra- and intermolecular difunctionalization of vinyl cyclopropanes (VCPs) with alkyl halides and aryl Grignard reagents has been realized via a mechanistically driven approach. 相似文献
994.
Lee K Song H Kim B Park JT Park S Choi MG 《Journal of the American Chemical Society》2002,124(12):2872-2873
Reaction of Rh(6)(CO)(9)(dppm)(2)(mu(3)-eta(2),eta(2),eta(2)-C(60)) (1) with C(60) in refluxing chlorobenzene followed by treatment with CNR (R = CH(2)C(6)H(5)) at room temperature affords the first fullerene-metal sandwich complex Rh(6)(CO)(5)(dppm)(2)(CNR)(mu(3)-eta(2),eta(2),eta(2)-C(60))(2) (2). Compound 2 has been characterized by an X-ray diffraction study. Electrochemical study of 2 reveals six well-separated reversible redox couples localized at C(60) cages due to a strong electronic communication between the two C(60) centers via the Rh(6) cluster spacer. 相似文献
995.
He Ping ZENG 《中国化学快报》2002,13(12)
Photoinduced electron transfer processes between fullerenes (C60 / C70) and N, N, N′, N′- tetra - ( p-methylphenyl ) - 4, 4′- diamino - 1, 1′- diphenyl ether ( TPDAE ) have been studied by nanosecond laser flash photolysis. Quantum yields and rate constants of electron transfer from TPDAE to excited triplet state of fullerenes (C60 / C70 ) in benzonitrile have been evaluated by observing the transient absorption bands in the near-IR region where the excited triplet state, radical anion of fullerenes ( C60 / C70 ) and radical cations of TPDAE appear. 相似文献
996.
Frank Seela Padmaja Chittepu Yang He Henning Eickmeier Hans Reuter 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(3):o173-o176
In 2‐(2‐deoxy‐β‐d ‐erythro‐pentofuranosyl)‐1,2,4‐triazine‐3,5(2H,4H)‐dione (6‐aza‐2′‐deoxyuridine), C8H11N3O5, (I), the conformation of the glycosylic bond is between anti and high‐anti [χ = −94.0 (3)°], whereas the derivative 2‐(2‐deoxy‐β‐d ‐erythro‐pentofuranosyl)‐N4‐(2‐methoxybenzoyl)‐1,2,4‐triazine‐3,5(2H,4H)‐dione (N3‐anisoyl‐6‐aza‐2′‐deoxyuridine), C16H17N3O7, (II), displays a high‐anti conformation [χ = −86.4 (3)°]. The furanosyl moiety in (I) adopts the S‐type sugar pucker (2T3), with P = 188.1 (2)° and τm = 40.3 (2)°, while the sugar pucker in (II) is N (3T4), with P = 36.1 (3)° and τm = 33.5 (2)°. The crystal structures of (I) and (II) are stabilized by intermolecular N—H⋯O and O—H⋯O interactions. 相似文献
997.
Hollow fiber membrane-protected solid-phase microextraction of triazine herbicides in bovine milk and sewage sludge samples 总被引:2,自引:0,他引:2
A porous polypropylene hollow fiber membrane (HFM)-protected solid-phase microextraction (HFM-SPME) procedure in conjunction with gas chromatography/mass spectrometric analysis for use in the determination of triazine herbicides in bovine milk samples is described. A 65-microm polydimethylsiloxane-divinylbenzne (PDMS-DVB) SPME fiber was protected by an HFM. HFM-SPME experimental parameters such as fiber type, extraction time, extraction temperature and salt concentration were investigated and optimized. The relative standard deviations for the reproducibility of the optimized HFM-SPME method varied from 4.30 to 12.37%. The correlation coefficients of the calibration curves were between 0.9799 and 0.9965 across a concentration range of 0-200 microg l(-1). The method detection limits for triazines in bovine milk were in the range of 0.003-0.013 microg l(-1) and limits of quantification were in the range of 0.006-0.021 microg l(-1). The suitability of HFM-SPME was extended to the analysis of the herbicides in sewage sludge samples. The results demonstrate that HFM-SPME was an efficient pretreatment and enrichment procedure for complex matrices. 相似文献
998.
Resveratrol has been shown to possess antioxidant and anticancer activities, but little is known on the effect of resveratrol derivatives. Recently we have isolated resveratrol and its dimers and trimers from peony (Paeonia lactiflora) seeds, and reported their strong antioxidant and cytotoxic activity. In the present study, we have evaluated cellular effects of resveratrol derivatives; viniferin, gnetin H, and suffruticosol B on the proliferation and apoptosis in HL-60 cells in vitro. All resveratrol and its derivatives reduced viability of HL-60 cells in a dose-dependent manner with their IC(50) values of 20-90 microM. Ascending orders of IC(50) values were suffruticosol B, gnetin H, viniferin and resveratrol respectively. HL-60 cells treated with the four stilbenes exhibited the distinct morphological changes characteristics of cell apoptosis such as chromatin condensation, apoptotic bodies, and DNA fragmentations. A time-dependent histogram of the cellular DNA analyzed by flow cytometry revealed a rapid increase in subdiploid cells and a concomitant decrease in diploid cells exposed to 100 microM resveratrol for 0-24 h. Cells treated with 25 microM of resveratrol, viniferin, gnetin H, and suffruticosol B for 24 h resulted in increment of sub-G1 population by 51, 5, 11 and 59%, respectively. Treatment of cells with 0-20 microM resveratrol for 5 h produced a concentration-dependent decrease in cytochrome P450 (CYP) 1B1 mRNA levels. Suffruticosol B also suppressed CYP1B1 gene expression. These results demonstrated that resveratrol oligomers also strongly suppressed HL-60 cell proliferation, and induced DNA damage. In addition, CYP1B1 gene supression may suggest an involvement in the resveratrol-induced apoptosis in HL-60 cells. 相似文献
999.
We have investigated atomic and electronic structures of hydrogen-chemisorbed single-walled carbon nanotubes (SWCNTs) by density functional calculations. We have searched for relative stability of various hydrogen adsorption geometries with coverage. The hydrogenated SWCNTs are stable with coverage of H/C, theta >/= 0.3. The circular cross sections of nanotubes are transformed to polygonal shapes with different symmetries upon hydrogen adsorption. We find that the band gap in carbon nanotubes can be engineered by varying hydrogen coverage, independent of the metallicity of carbon nanotubes. This is explained by the degree of sp(3) hybridization. 相似文献
1000.
Crystal and molecular structures of the planar neutral ligand, C26H16N8, and the four isomorphous five-coordinated metal complexes, [M(C26H16N8)(H2O)], M = Mn(II), Co(II), Cu(II), Zn(II), have been determined from three-dimensional X-ray diffraction data. The free ligand hpH2, C26H16N8, belongs to the P 21/c space group with Z=2, a=4.142(3), b=23.736(6), c=10.338(3) Ä, β=94.66(6)°. The metal complexes monohydrate Mhp-H2O all belong to the orthorhombic Pcab space group with Z=8. The dimensions are roughly 8.8×19.3×23.7 Å3. In each structure, the macrocyclic ligand has an almost planar conformation which differs from the saddle shaped ligand hydrate (hpH2·H2O) and the nickel complex [Nihp]5. The distances from the center of the macrocyclic ring to the nitrogen atom of the free ligand are 1.907(6) and 2.245(6)Å. The coordination geometry in these four complexes is square pyramidal with a water molecule as an axial ligand. The bond distances of M(II)-O(H2O), M(II)-N1 (imine), M(II)-N3 (pyridine) are: 2.19(1), 2.00(2), 2.27(2)Å respectively for the manganese complex; 2.08(1), 1.97(1), 2.23(1)Å for the cobalt complex; 2.33(1), 1.92(3), 2.18(1)Å for the copper complex; 2.110(5), 1.964(6), 2.252(6)Å for the zinc complex. The variation of metal-ligand distances can be correlated to the metal d orbital occupancy. A comparison with similar ligands will be presented. 相似文献