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951.
5-Hydroxytryptamino-induced calcium sparks in cultured rat stomach fundus smooth muscle cells 总被引:1,自引:0,他引:1
With the imaging fluorescence probe of Ca2+ (fluo-3) and a laser scanning confocal micro-scope, the spontaneous localized calcium release event was first discovered in resting rat cardiac myocytes by Cheng[1] in 1993. A mathematical simulation is developed with computer in order to reveal the effect, which is immediately suggested that these events are likely to reflect the local-ized release of Ca2+ from a small cluster of ryanodine-sensitive Ca2+ release channels in sar-coplasmic reticulum … 相似文献
952.
Zhan‐Xin Zhang Wei‐Dong Xie Ping‐Lin Li Yan‐Ping Shi Zhong‐Jian Jia 《Helvetica chimica acta》2006,89(12):2927-2933
Six new compounds were isolated from the whole plant of Sonchus uliginosus, including three eudesmane‐type sesquiterpenoids (1β,6α)‐1,6,14‐trihydroxyeudesm‐3‐en‐12‐oic acid γ‐lactone ( 1 ), (1β,6α)‐1,6,14‐trihydroxyeudesma‐3,11(13)‐dien‐12‐oic acid γ‐lactone ( 2 ), and (1β,6α)‐1,6‐dihydroxy‐14‐O‐[(4‐hydroxyphenyl)acetyl]eudesma‐3,11(13)‐dien‐12‐oic acid γ‐lactone ( 3 ), and three phenylpropane derivatives, 4‐hydroxy‐γ,3,5‐trimethoxybenzenepropanol ( 6 ), γ,3,4,5‐tetramethoxybenzenepropanol ( 7 ), and γ,3,4,5‐tetramethoxybenzenepropanol acetate ( 8 ), together with the two known compounds 4 and 5 . The new structures were elucidated by means of spectroscopic methods, such as IR, EI‐MS, HR‐ESI‐MS, 1D‐ and 2D‐NMR, and by comparison of the spectroscopic data with those reported for structurally related compounds. 相似文献
953.
954.
本文对电荷转移复合分子晶体TMPD·(TCNQ)_2的电子能带进行了计算。在计算中将TMPD及TCNQ分别作为准一维分子柱来处理。所用计算方法为EHMO/LCAO-MO-CO方法。计算结果再次证实我们在前文给出的规律, 即分子晶体能带的位置由其孤立分子相应分子轨道能级的位置决定, 而能带宽度由相邻分子的相应分子轨道间的相互作用决定。本文还对该晶体的能带结构及其与室温电导率的关系进行了讨论, 并与NMP·TCNQ 和TTF·TCNQ晶体的进行比较。 相似文献
955.
Reduced viscosity polymer matrices for microchip electrophoresis of double-stranded DNA 总被引:1,自引:0,他引:1
On a polymethylmethacrylate (PMMA) microchip, double-stranded DNA fragments with a wide size range from 50 bp to 20 kbp were separated by two polymer solutions. One was a hydroxypropylmethylcellulose-4000 (HPMC-4000) solution of 1.3% (w/v) to separate fragments below 590 bp, and another was a mixed four molecular weight poly(ethylene oxide) solution at a total concentration of 0.1% to separate fragments above 520 bp. The widths at half height (wh) of the fragments had a good relationship with their migration times (tR) in both polymer solutions. Such a relationship was suitable for obtaining the wh values of unresolved peaks, calculating the resolution of two adjacent fragments, and optimizing microchip separation matrices. Based on the relativity, a low viscosity medium containing 2% HPMC-50 and 8% glucose was optimized for high-performance separation of a phiX174 HaeIII restriction fragment digest. 相似文献
956.
Liya?Wang Zhiliang?Liu Chenxi?Zhang Zhanquan?Liu Daizheng?Liao Zonghui?JiangEmail author Shiping?Yan 《中国科学B辑(英文版)》2003,46(6):533-541
A novel one-dimensional manganese(II) complex containing nitronyl nitroxide radical [Mn2(IM2-py)2(Ac)2(μ1,1-N3)(μ1,3-N3) · EtOH]
n
was synthesized and characterized structurally and magnetically. It crystallizes in the monoclinic space group p21/n. Each Mn(II) ion is six-coordinated in a distorted octahedral environment. The two N atoms of the nitronyl nitroxide radical
and the two O atoms of acetate ligands are in the equatorial plane, whereas the two different azido bridging ligands are in
trans axial position. Mn(II) ions are linked by nitrogen atom of μ1,1-azido and oxygen atoms of two carboxy groups to form a Mn-Mn unit. Mn-Mn units are linked by azido ligands through μ1,3 bridging style to form a one-dimensional chain. The compound is connected by the coordination bonds, π-π interactions and
hydrogen bonds as a three-dimensional structure. Magnetic susceptibility data support that there are stronger antiferromagnetic
interactions between the radical and Mn(II) ion, weak antiferromagnetic interactions between the Mn-R units, and very weak
antiferromagnetic interactions between the R-Mn-Mn-R units. 相似文献
957.
A novel carrier of ultradispersed diamond black powder (UDDBP) was used to support metallocene catalyst. Al2O3 was also used as carrier in order to compare with UDDBP. Supported catalysts for ethylene polymerization were synthesized by two different reaction methods. One way was direct immobilization of the metallocene on the support, the other was adsorption of MAO onto the support followed by addition of the metallocene. Four supported catalysts Cp2ZrCl2/UDDBP, Cp2ZrCl2/Al2O3, Cp2ZrCl2/MAO/UDDBP and Cp2ZrCl2/Al2O3/MAO were obtained. The content of the zirconium in the supported catalyst was determined by UV spectroscopy. The activity of the ethylene polymerization catalyzed by supported catalyst was investigated. The influence of Al/Zr molar ratio and polymerization temperature on the activity was discussed. The polymerization rate was also observed. 相似文献
958.
Patterned polyelectrolyte multilayer: surface modification for enhancing selective adsorption 总被引:4,自引:0,他引:4
Shi F Wang Z Zhao N Zhang X 《Langmuir : the ACS journal of surfaces and colloids》2005,21(4):1599-1602
This paper describes the use of surface chemical modification to enhance the difference of the surface charge on a patterned polyelectrolyte multilayer, which can be used for selectively adsorbing functional materials. We fabricated a patterned multilayer by combining the layer-by-layer self-assembly technique and photolithography and taking advantage of the different solubility of polyelectrolyte multilayers of diazo resins (DAR)/poly(acrylic acid) before and after UV irradiation. This patterned surface can be used as a matrix for selective adsorption of small molecular dyes, such as Methylene Blue. However the difference in surface charge on the patterned surface was not enough when we used it to selectively adsorb polystyrene (PS) nanoparticles using electrostatic force as the driving force. Therefore, we modified the patterned surface by interfacial chemistry. After modification, the patterned polyelectrolyte multilayer can be used as a good matrix for selective adsorption of PS nanoparticles with both positive and negative charges. 相似文献
959.
Paranemic crossover (PX) DNA is a four-stranded coaxial DNA complex containing a central dyad axis that relates two flanking parallel double helices. The strands are held together exclusively by Watson-Crick base pairing. The key feature of the structure is that the two adjacent parallel DNA double helices form crossovers at every point possible. Hence, reciprocal crossover points flank the central dyad axis at every major or minor groove separation. This motif has been modeled and characterized in an oligonucleotide system; a minor groove separation of five nucleotide pairs and major groove separations of six, seven, or eight nucleotide pairs produce stable PX DNA molecules; a major groove separation of 9 nucleotide pairs is possible at low concentrations. Every strand undergoes a crossover every helical repeat (11, 12, 13, or 14 nucleotides), but the structural period of each strand corresponds to two helical repeats (22, 24, 26, or 28 nucleotides). Nondenaturing gel electrophoresis shows that the molecules are stable, forming well-behaved complexes. PX DNA can be produced from closed dumbbells, demonstrating that the molecule is paranemic. Ferguson analysis indicates that the molecules are similar in shape to DNA double crossover molecules. Circular dichroism spectra are consistent with B-form DNA. Thermal transition profiles suggest a premelting transition in each of the molecules. Hydroxyl radical autofootprinting analysis confirms that there is a crossover point at each of the positions expected in the secondary structure. These molecules are generalized Holliday junctions. 相似文献
960.
Qi‐Wei Zhang Yi‐Hang Wen Yun‐Long Feng 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(6):m255-m257
The title compound, [Zn2(C5H6O4)2(C13H14N2)]n or [Zn2(glu)2(bpp)]n, is a novel zinc polymer based on mixed flexible glutarate (glu) and 1,3‐di‐4‐pyridylpropane (bpp) ligands. The ZnII center has a distorted tetrahedral geometry and the central atom of the bpp ligand is located at a special site with a C2 axis passing through it. A layer is formed by Zn–glu bonding. Such layers are pillared by bpp ligands, forming a three‐dimensional framework with large channels. The inverted interpenetration of two three‐dimensional frameworks completes the molecular structure. 相似文献