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961.
Study on swelling behavior of poly(sodium acrylate‐co‐2‐acryloylamino‐2‐methyl‐1‐propanesulfonic acid)/attapulgite macroporous superabsorbent composite 下载免费PDF全文
A fast swelling sulfonic acid macroporous superabsorbent composite is prepared by copolymerization of partially neutralized acrylic acid, 2‐acryloylamino‐2‐methyl‐1‐propanesulfonic acid, and attapulgite. The effects of pH values, ions, and their concentration on swelling behavior of sample are investigated. The results show that the swelling behavior of sample is affected by pH value. The supercase Π diffusion is observed in all NaCl solutions with different pH value. An overshooting effect appears in all solutions containing multivalent cations. This phenomenon may be attributed to the reorganization of the gel structure due to the formation of complex compound between cation and polymer network. A quantitative kinetics model proposed by Díez‐Peña is used to interprete it and the theoretical curves are in good agreement with the experimental data. For anions, it shows little effect on swelling process, and supercase Π diffusion is also observed no matter which kind of anion exists in swelling medium. POLYM. ENG. SCI., 55:681–687, 2015. © 2014 Society of Plastics Engineers 相似文献
962.
Simulation of polyimide fibers with trilobal cross section produced by dry‐spinning technology 下载免费PDF全文
As one type of high performance fibers, polyimide fibers can be prepared from polyamic acid (PAA) solution by dry‐spinning technology. The transformation from the precursor of polyamic acid to polyimides via thermal cyclization reaction in the dry‐spinning process is a main distinguishing feature, which is very different from other fibers produced by dry‐spinning such as cellulose acetate fiber and polyurethane fiber. In this report, the dry‐spinning formation of polyimide fibers with trilobal cross section from PAA solution in N,N‐dimethylacetamide is simulated via a one‐dimensional model based on a viscoelastic constitutive equation, combined with profile degree equation of cross section and imidization kinetics equation. The glass transition temperature, imidization degree and profile degree of the filament along the spinline are predicted by the model, as well as relative parameters such as solvent mass fraction and temperature. As a simulated result, solidification of polyimide fibers take place about 150 cm from the spinneret which is farther than for cellulose acetate fiber (70 cm). Moreover, the final profile degree of fiber is affected by many spinning parameters, such as spinning temperature, surface tension, spinning solution concentration, major, and minor axis length of the spinneret hole. POLYM. ENG. SCI., 55:2148–2155, 2015. © 2015 Society of Plastics Engineers 相似文献
963.
Blends of poly(phenylene sulfide) (PPS) and recycled poly(ether ether ketone) (r‐PEEK) were prepared using a twin‐screw extruder. The carbon nanotube (CNT) added to the blends not only improved the compatibility of the two polymers, but also affected the morphology of the immiscible PPS/r‐PEEK blends. R‐PEEK always forms the dispersed phase and PPS the continuous phase in such blends. In the composite, CNT particles were observed in the PPS phase, mostly distributes in the interface between PPS and PEEK. The results show that r‐PEEK improves the impact and tensile strength of PPS, but does not provide nucleation effect on PPS. However, CNT improved the flexural modulus of PPS/r‐PEEK blends and promoted the crystallization of r‐PEEK rather than that of PPS. The prepared PPS/r‐PEEK blends provided larger electrical conductivity than neat polymers. Adding 20 wt % CNT to blend resulted in composite with the minimum volume resistivity, a reduction of four orders of magnitude, compared with that of the neat blend. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42497. 相似文献
964.
Effect of aliphatic diacyl adipic dihydrazides on the crystallization of poly(lactic acid) 下载免费PDF全文
A series of aliphatic diacyl adipic dihydrazides (ADHs) with different alkyl moieties were synthesized by the reaction between adipic dihydrazide and acyl chloride. Then these ADHs were solution blended with PLA respectively and were evaluated as nucleating agents. Through the investigation of nonisothermal and isothermal crystallization, it was found that both the crystallization rate and the crystallinity of PLA could be enhanced by adding only 1 wt % of ADHs. Especially for ADH‐Oc (ADH‐Octyl), the crystallization rate of PLA increased about 4 times at 105°C. Optical morphology showed that and the size of PLA spherulites decreased and the nucleation density increased with the existence of ADH‐Oc. Meanwhile, the crystal structure of PLA were not discerniblly affected after the addition of ADHs as found by wide‐angle X‐ray diffraction. Thus, this study suggested these ADHs compounds are simple and potential nucleating agents to enhance crystallization ability of PLA. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42028. 相似文献
965.
966.
Jiale Xu Lei Hu Yuzhu Song Fei Han Yongqiang Qiao Jinxia Deng Jun Chen Xianran Xing 《Journal of the American Ceramic Society》2017,100(12):5385-5388
Isotropic zero thermal expansion (ZTE) is rare but intriguing physical property in materials. Here, we report an isotropic ZTE property in a double ReO3‐type compound of MgZrF6, which exhibits a negligible value of coefficient of thermal expansion (αl = ?7.94 × 10?7 K?1 (XRD), αl = ?4.22 × 10?7 K?1 (dilatometry), 300‐675 K). The ZTE mechanism of MgZrF6 is understood by the joint studies of temperature dependence of crystal structure and lattice dynamics. Interestingly, different magnitudes of atomic displacement parameters (ADPs) for the fluorine atoms in MZrF6 (M = Ca, Ni, Mg) are found. The strong temperature sensitivity of ADPs demonstrates intensive transverse thermal vibration of fluorine atoms, which contributes essentially to the negative thermal expansion of CaZrF6. By contrast, for NiZrF6 with positive thermal expansion, the temperature response of ADPs is weak. Moderate transverse thermal vibration takes place in MgZrF6, and ZTE appears. Furthermore, lattice dynamics of MgZrF6 is studied by temperature‐dependent Raman spectroscopy, which reveals the ZTE mechanism. In particular, the F2g and Ag modes, corresponding to the bending and stretching vibrations of fluorine atoms, respectively, neither soften nor harden over the whole temperature range, which is correlated with the isotropic ZTE property of MgZrF6. 相似文献
967.
968.
High‐performance polymer‐supported extractants with phosphonate ligands for scandium(III) separation 下载免费PDF全文
Hongmin Cui Ji Chen Hailian Li Dan Zou Yu Liu Yuefeng Deng 《American Institute of Chemical Engineers》2016,62(7):2479-2489
As the market demand for scandium has grown, a great deal of interest has been generated in its recovery. To substantially simplify the process and provide a green alternative for scandium separation, novel polymer‐supported extractants containing di(2‐ethylhexyl) phosphonate and bis(2,4,4‐trimethylpentyl) phosphonate, [D201][DEHP] and [D201][C272] are proposed because they demonstrate improved adsorption capacity and selectivity toward scandium(III). Scandium(III) adsorption is significantly affected by the solution pH, with the maximum adsorption occurring at a pH of approximately 0.78. The batch adsorption data fit well with the Langmuir isotherm and pseudo‐second‐order kinetic models. A combination of the Fourier transform infrared and XPS spectra suggest that the complexation of oxygen atoms in phosphate groups with scandium(III) is the predominant adsorption mechanism. Additionally, the two resins were used to recover scandium from leaching liquor of nickel laterite ore. [D201][DEHP] exhibits unusual selectivity for scandium and low competitive behavior with other metals, thus increasing its market potential. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2479–2489, 2016 相似文献
969.
David L. Brandon Thomas A. McKeon Stephanie A. Patfield Qiulian Kong Xiaohua He 《Journal of the American Oil Chemists' Society》2016,93(3):359-363
To facilitate the analysis of castor (Ricinus communis L.) seed fractions and germplasm for ricin content, we investigated the use of enzyme‐linked immunosorbent assay (ELISA) methods to differentiate between ricin toxin and the related Ricinus communis agglutinin (RCA). Both proteins are based on a heterodimeric AB structure, with a common A chain. RCA comprises two dimers of A and B chains. Both proteins are found in the meal remaining after castor oil extraction and impede the commercial production of castor seed in the USA. We identified pairs of monoclonal antibodies (mAbs) that could distinguish between the structurally related proteins that share a common A chain. Antibody specificity was determined by ELISA and checked by immunoblotting. We found that mAb–mAb pairs afforded quantification of each castor protein, and that a mAb paired with a commercial polyclonal antibody provided detection of both with comparable sensitivity. 相似文献
970.
Significant Improvement of Superconducting Properties in Nano‐NiFe2O4‐Doped Y–Ba–Cu–O Single‐Grain Superconductor 下载免费PDF全文
Introduction of refined second‐phase particles in superconducting YBa2Cu3O7?x (Y‐123) matrix is known to be an effective route to improve the δl‐type pinning and the performance of Y–Ba–Cu–O (YBCO) single‐grain superconductors, while the δTc‐type pinning induced by spatial fluctuations in matrix composition is also important and contributes to the in‐field Jc performance and high‐field applications of bulk superconductors. In this communication, chemical doping of nano‐sized NiFe2O4 (mean size 50 nm) in single‐grain YBCO superconductor is performed using a novel top‐seeded infiltration growth (TSIG) technique based on a solid source pellet (SSP) of nano‐Y2O3 + BaCuO2. The results indicate that, significant improvement of bulk performances including levitation force (33.93 N) and trapped field (0.3628 T) has been observed in the 0.2 wt% nano‐NiFe2O4‐doped sample, which are much higher than the undoped sample (28.81 N and 0.2754 T). Tc measurement indicates that, a decreased onset Tc of about 87.5 K and a broadened transition width of about 5 K are observed in the NiFe2O4‐doped sample, indicating appearance of weak superconducting regions in superconducting matrix caused by Ni and Fe substitutions in Y‐123 crystal lattice. This study supplies a practical approach to increase the YBCO bulk performance significantly. 相似文献