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51.
Highly Curved Bowl‐Shaped Fragments of Fullerenes: Synthesis,Structural Analysis,and Physical Properties 下载免费PDF全文
Min‐Kuan Chen Hsin‐Ju Hsin Dr. Tsun‐Cheng Wu Bo‐Yan Kang Yen‐Wei Lee Prof. Ming‐Yu Kuo Prof. Yao‐Ting Wu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(2):598-608
Highly curved buckybowls 3 , 4 , and 5 were synthesized from planar precursors, fluoranthenes 8 , benzo[k]fluoranthenes 10 and naphtho[1,2‐k]‐cyclopenta[cd]fluoranthenes 12 , respectively, using straightforward palladium‐catalyzed cyclization reactions. These fluoranthene‐based starting materials were easily prepared from 1,8‐bis(arylethynyl)naphthalenes 6 . Both buckybowls 3 and 4 are fragments of C60, whereas 5 is a unique subunit of C70. The curved structures were identified by X‐ray crystallography, and they are deep bowls. The maximum π‐orbital axis vector (POAV) pyramidalization angle in both 3 and 4 is 12.8°. Such a high curvature is very rarely obtained. Buckybowls 5 are less curved than the others because they have a lower density of five‐membered rings, analogous to the tube portion of C70. Cyclopentaannulation increases the bowl depths of 3 and 4 , but not the maximum POAV pyramidalization angle. Among the eight buckybowls studied herein, five form polar crystals. The bowl‐to‐bowl inversion dynamics of these buckybowls can be classified into two types; one has a planar transition structure, whereas the other has an S‐shaped transition structure. A larger longitudinal length of these buckybowls corresponds to a stronger preference for the latter. The photophysical properties of these buckybowls were examined and compared with those of C60 and C70. Buckybowls 5 have absorption bands at wavelengths greater than 450 nm, which are similar to those of C70. The chiral resolution of the mono‐substituted buckybowl 4 ac was also studied by using HPLC with a chiral column. 相似文献
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53.
Cheng-Li Wang Weng-Sing Hwang Hsueh-Liang Chu Feng-Lin Yen Chi-Yuen Hwang Chi-Shiung Hsi Huey-Er Lee Moo-Chin Wang 《Journal of Sol-Gel Science and Technology》2014,70(3):428-440
The phase transformation and crystalline growth of 4 mol% yttria partially stabilized zirconia (4Y-PSZ) precursor powders have been investigated using the coprecipitation route, using zirconium oxide chloride octahydrate (ZrOCl2·8H2O) and yttrium nitrate (Y(NO3)3·6H2O) as the initial materials. Differential thermal analysis (DTA), X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), nano beam electron diffraction (NBED), and high resolution TEM (HRTEM) were utilized to characterize the behavior of phase transformation and crystalline growth of the 4Y-PSZ precursor powders after calcined. Tetragonal ZrO2 crystallization occurred at about 718.2 K. The activation energy of tetragonal ZrO2 crystallization was 227.0 ± 17.4 kJ/mol, obtained by a non-isothermal method. The growth morphology parameter (n) and growth mechanism index were close to 2.0, showing that tetragonal ZrO2 had a plate-like morphology. The crystalline size of tetragonal ZrO2 increased from 7.9 to 27.6 nm when the calcination temperature was increased from 973 to 1,273 K. The activation energies of tetragonal ZrO2 growth were 14.97 ± 0.33 and 84.46 ± 6.65 kJ/mol when precursor powders after calcined from 723–973 and 973–1,273 K, respectively. 相似文献
54.
Dr. Hsin-Yung Yen Dr. Idlir Liko Joseph Gault Dr. Di Wu Dr. Weston B. Struwe Prof. Carol V. Robinson 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(36):15690-15694
The immune scavenger protein DC-SIGN interacts with glycosylated proteins and has a putative role in facilitating viral infection. How these recognition events take place with different viruses is not clear and the effects of glycosylation on the folding and stability of DC-SIGN have not been reported. Herein, we report the development and application of a mass-spectrometry-based approach to both uncover and characterise the effects of O-glycans on the stability of DC-SIGN. We first quantify the Core 1 and 2 O-glycan structures on the carbohydrate recognition and extracellular domains of the protein using sequential exoglycosidase sequencing. Using ion mobility mass spectrometry, we show how specific O-glycans, and/or single monosaccharide substitutions, alter both the overall collision cross section and the gas-phase stability of the DC-SIGN isoforms. We find that rather than the mass or length of glycoprotein modifications, the stability of DC-SIGN is better correlated with the number of glycosylation sites. 相似文献
55.
Ruixiang Qu Xiangyu Li Yanan Liu Huajun Zhai Shuaiheng Zhao Lin Feng Yen Wei 《Angewandte Chemie (International ed. in English)》2020,59(32):13437-13443
Superwetting membranes with responsive properties have attracted heightened attention because of their fine‐tunable surface wettability. However, their functional diversity is severely limited by the “black‐or‐white” wettability transition. Herein, we describe a coating strategy to fabricate multifunctional responsive superwetting membranes with SiO2/octadecylamine patterns. The adjustable patterns in the responsive region are the key factor for functional diversity. Specifically, the coated part of the membrane displayed a superhydrophobicity/superhydrophilicity transition at different pH values, whereas the uncoated part exhibited invariant superhydrophilicity. On the basis of this anisotropy/isotropy transition, the membranes can serve as either responsive permeable membranes or signal‐expression membranes, thus enabling the responsive separation and permeation of liquids with satisfactory separation efficiency (>99.90 %) and flux (ca. 60 L m?2 h), as well as real‐time liquid signal expression with alterable signals. 相似文献
56.
Dr. Gábor London Kuang‐Yen Chen Dr. Gregory T. Carroll Prof. Dr. Ben L. Feringa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(32):10690-10697
We report the synthesis of altitudinal molecular motors that contain functional groups in their rotor part. In an approach to achieve dynamic control over the properties of solid surfaces, a hydrophobic perfluorobutyl chain and a relatively hydrophilic cyano group were introduced to the rotor part of the motors. Molecular motors were attached to quartz surfaces by using interfacial 1,3‐dipolar cycloadditions. To test the effect of the functional groups on the rotary motion, photochemical and thermal isomerization studies of the motors were performed both in solution and when attached to the surface. We found that the substituents have no significant effect on the thermal and photochemical processes, and the functionalized motors preserved their rotary function both in solution and on a quartz surface. Preliminary results on the influence of the functional groups on surface wettability are also described. 相似文献
57.
Yi-Jung Liu Chih-Hung Yen Chia-Hao Hsu Kuo-Hui Yu Li-Yang Chen Tsung-Han Tsai Wen-Chau Liu 《Optical Review》2009,16(6):575-577
An interesting GaN-based light emitting diode (LED) using a 50 nm indium oxide (In2O3)/250 nm indium-tin oxide (ITO) mixed structure to replace the commonly used ITO (250 nm) current spreading layer is fabricated
and studied. Use of the In2O3 layer could reduce the contact resistance of p-GaN in LEDs. In addition, this highly-resistive In2O3 layer, below the ITO layer could improve the current spreading performance. Experimentally, at room temperature, using this
mixed structure, the luminous and EL intensities are enhanced by 17.7 and 17.1%, respectively. 相似文献
58.
Nguyen Huy Dan Pham Thi ThanhNguyen Hai Yen Nguyen Thi Thanh Huyen Duong Dinh Thang Luu Tien Hung 《Journal of magnetism and magnetic materials》2012,324(7):1435-1439
We have observed magnetic anisotropy in bulk Nd55−xCoxFe30Al10B5 (x=10, 15 and 20) alloys prepared by copper mold suction casting method with a presence of external magnetic field (quenching field) μ0H=0.25 T. By changing direction of the measuring field from perpendicular to parallel one in comparison with that of the quenching field, coercive force of the alloys slightly decreases while remanent magnetization and squareness of hysteresis loop increase more clearly. It is also found that the higher Co-concentration in the alloys the larger magnetic anisotropy is induced. The structure analyses manifest nanocrystalline particles embedded in residual amorphous matrix of the alloys. The size of the particles is in range of 10-30 nm and their crystalline phases consist of Nd2(Fe,Co)14B, Nd3Co, Nd3Al, NdAl2 and Nd. 相似文献
59.
Four kinds of poly(ethylene glycol) (PEG) derivatives with the similar backbone and different side groups have been synthesized successfully. When both catecholamine and double bond are tethered to polymer backbone, i.e., the PEG backbone, simultaneously, the polymer can accelerate the curing speed of ethyl α‐cyanoacrylate (commercially available as 502) greatly under the same conditions (the curing time of such system is no more than 5 s). Probably this is due to the autoxidation of catecholamines. Through the redox‐cycling, catecholamines can produce, collect free radicals, and thus initiate the free radical polymerization. Due to the fast‐curing of such material when mixed with α‐cyanoacrylate, we could design and develop a new bicomponent super bioglue used in the dentistry or other bioenvironment requiring super fast settlement for further surgical operations. 相似文献
60.