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91.
92.
The stages of transformation of a colloidal crystalline film of latex spheres to a new periodic structure were imaged by atomic force microscopy. Colloidal crystalline films were prepared with 320 nm diameter poly(styrene-co-2-hydroxyethyl methacrylate) (PSt/HEMA) spheres. The hexagonally ordered surfaces of the colloidal crystalline films were transformed with styrene vapor at room temperature to a new morphology having holes in the surface and the same periodicity as the original films. The surfaces of colloidal crystals and the transformed films have a raspberry-like texture superposed on the 320 nm hexagonal periodicity. Both height images and phase images reveal that the latex spheres shrink and the transformation proceeds by an order-disorder-order sequence. The final structure is an interconnected colloidal array with smaller polystyrene particles dispersed in a continuous PSt/HEMA matrix. 相似文献
93.
94.
Ho-Shen Lin Ashraff A. Rampersaud Karen Zimmerman Mitchell I. Steinberg Donald B. Boyd 《中国化学会会志》1993,40(3):273-282
A series of nonpeptide angiotensin II receptor antagonists was synthesized via palladium-assisted cross coupling of aryl stannane and cycloalkenyl triflates and subsequent alkylation of silyl-protected imidazole. Our compounds, which have a terminal five- to seven-membered cycloalkenyl ring, are compared to DuPont EXP7711, an N-[(2′-carboxybiphenylyl)methyl]imidazole, which has a terminal phenyl moiety. Physicochemical properties of the compounds, such as lipophilicity, steric bulk, conformation, and the relative spatial proximity of the 2-carboxyl and the middle phenyl, are quantitated by computational chemistry. Potency in terms of binding affinity to AT1 receptors in rat adrenal glomerulosa and rabbit aorta is maximized when the terminal ring is aromatic. 相似文献
95.
96.
Frank R. Fronczek Richard D. Gandour Laura M. B. Gehrig Lyman R. Caswell Karen A. McDowell I. Alam 《Journal of inclusion phenomena and macrocyclic chemistry》1987,5(3):379-383
The first crystal structure of a potassium cation complex with dicyclohexano-18-crown-6 is reported. The potassium 2-nitrophenoxide complex ofsyn-cis-syn dicyclohexano-18-crown-6 crystallizes in the triclinic space group P
with cell constantsa=8.604(2),b=10.772(4),C=16.123(5)Å, =73.86(3)°,=77.61(3)°, =82.68(3)° andZ=2 forD
c
=1.31 g cm–3. Least-squares refinement based on 2742 observed reflections led to a final conventionalR value of 0.040. Dicyclohexano-18-crown-6 has the shape of a saddle with the potassium cation sitting at the saddlepoint. The structure of the 2-nitrophenoxide anion is dominanted by the quinoid resonance contributor. Because the complex is devoid of significant intercomplex interactions, it is a prototypical 1:1:1 complex.
Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82043 (26 pages).Now Mrs. K. M. Balo. 相似文献
97.
98.
Background
Kynureninase is a key enzyme on the kynurenine pathway of tryptophan metabolism. One of the end products of the pathway is the neurotoxin quinolinic acid which appears to be responsible for neuronal cell death in a number of important neurological diseases. This makes kynureninase a possible therapeutic target for diseases such as Huntington's, Alzheimer's and AIDS related dementia, and the development of potent inhibitors an important research aim. 相似文献99.
Guo Zhijun Niu Yanning Zhang Weiguang Tan Minyu 《Journal of Radioanalytical and Nuclear Chemistry》2004,262(2):331-337
N,N,N',N',N',N'-Hexaethyl-2,2′,2'-(nitrilotrisethyleneoxy-2-benzyloxy)tris(acetamide) (L3) has been prepared and characterized
by using IR, 1H NMR and positive-ion FAB mass spectra. The extraction of Th4+ and UO2
2+ with N,N,N',N',N',N'-hexaethyl-2,2',2'- (nitrilo-trisethyleneoxy)tris(acetamide) (L1), N,N,N',N',N',N'-hexaisopropyl-2,2',2'-(nitrilotrisethyleneoxy)tris(acetamide)
(L2), and L3 was studied at 20±1 °C as a function of diluent, concentration of free extractant in organic phase and concentration
of picrate in aqueous phase. It was found that the extracting powers of L1 and L2 for Th4+ are almost identical. The extracting power of L2 for UO22+ was slightly higher than that of L1. The difference in terminal
groups (ethyl or isopropyl) of the extractants (L1 and L2) with same backbone has a little effect on the extracting power
for both Th4+ and UO22+. The extracting powers of L3 for both Th4+ and UO22+ were larger than those of L1 and L2. The extractants
(L1 and L3) having the same terminal group (ethyl) with different backbones have obviously different extracting powers for
Th4+ or UO22+. The extracting powers of all three extractants L1, L2, and L3 for Th4+ were larger than those for UO22+. The
compositions of extracted species in organic phase were predominantly ThL(Pic)3NO3 and UO2L(Pic)NO3, respectively (L denotes
L1, L2 and L3).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
100.
Nafion membranes were modified by chemical polymerization of aniline using ammonium peroxodisulfate as the oxidant. The Nafion-polyaniline composite membranes were extensively characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), infrared (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and ion-exchange capacity measurements. The transport properties were also evaluated by conductivity and electrodialysis measurements. The data show that when a high oxidant concentration (1 M (NH4)2S2O8) is used, polyaniline is mostly formed at the surface of the Nafion membrane with a higher proportion of oligomers. On the contrary, when 0.1 M oxidant is used, polyaniline is mostly formed inside the ionic domains of Nafion, blocking the pathway to ion transport and thus reducing the transport of Zn2+ as well as the transport of H+. These data were also compared to the data obtained with poly(styrene sulfonate)-PANI composite membranes. 相似文献