全文获取类型
收费全文 | 2337篇 |
免费 | 42篇 |
专业分类
电工技术 | 22篇 |
综合类 | 2篇 |
化学工业 | 346篇 |
金属工艺 | 105篇 |
机械仪表 | 29篇 |
建筑科学 | 88篇 |
矿业工程 | 3篇 |
能源动力 | 28篇 |
轻工业 | 221篇 |
水利工程 | 6篇 |
无线电 | 220篇 |
一般工业技术 | 350篇 |
冶金工业 | 635篇 |
原子能技术 | 15篇 |
自动化技术 | 309篇 |
出版年
2021年 | 18篇 |
2020年 | 17篇 |
2019年 | 24篇 |
2018年 | 22篇 |
2017年 | 17篇 |
2016年 | 19篇 |
2015年 | 22篇 |
2014年 | 41篇 |
2013年 | 79篇 |
2012年 | 68篇 |
2011年 | 87篇 |
2010年 | 58篇 |
2009年 | 55篇 |
2008年 | 83篇 |
2007年 | 71篇 |
2006年 | 92篇 |
2005年 | 75篇 |
2004年 | 54篇 |
2003年 | 61篇 |
2002年 | 69篇 |
2001年 | 60篇 |
2000年 | 38篇 |
1999年 | 50篇 |
1998年 | 130篇 |
1997年 | 86篇 |
1996年 | 75篇 |
1995年 | 51篇 |
1994年 | 50篇 |
1993年 | 45篇 |
1992年 | 40篇 |
1991年 | 21篇 |
1990年 | 38篇 |
1989年 | 33篇 |
1988年 | 26篇 |
1987年 | 26篇 |
1986年 | 26篇 |
1985年 | 34篇 |
1984年 | 28篇 |
1983年 | 22篇 |
1982年 | 26篇 |
1981年 | 21篇 |
1980年 | 24篇 |
1979年 | 26篇 |
1978年 | 25篇 |
1977年 | 25篇 |
1976年 | 43篇 |
1975年 | 20篇 |
1974年 | 18篇 |
1973年 | 15篇 |
1956年 | 10篇 |
排序方式: 共有2379条查询结果,搜索用时 359 毫秒
81.
Michael Herrmann Ulrich Frter‐Barth Manfred A. Bohn Horst Krause Michael Koch Werner Arnold 《Propellants, Explosives, Pyrotechnics》2015,40(6):880-885
Non‐destructive X‐ray diffraction techniques were applied in order to monitor the influence of mechanical and shock‐loading on the microstructure of the plastic‐bonded high explosive KS32. The investigations uncovered damage to embedded coarse HMX crystals and to the binder system HTPB‐IPDI. Damage to the crystals occurred already during the kneading process in terms of deformation twinning. On higher loading between 400 MPa (static) and 480 MPa (dynamic) also crystal fracture was observed. The change in the binder structure was found after both static and dynamic loading, but not in the cured, differently kneaded samples. Moreover, the change in binder structure after dynamic loading was verified by dynamic mechanical analysis, and interpreted as a partial damage of the binder rubber shell around the explosive particles. The results are compared to literature data from imaging techniques. 相似文献
82.
83.
The tensile and dynamic mechanical properties of polystyrene and a poly(styrene-co-buty1 acrylate-co-cyclohexy1 methacrylate) statistical terpolymer (terpolymer) reinforced by randomly oriented, discontinuous ultra-high molecular weight polyethylene (UHMWPE) fibers are presented in terms of the fiber/matrix interfacial properties. Using a thermomechanical block model based on the parallel rule of mixtures, the adhesion characteristics of poly(butyl acrylate) (PBA) and poly(cyclohexyl methacrylate) (PCHM) grafted, plasma treated, and untreated fibers were determined. The model successfully predicts the tan δ response of the composites including peak height variations and the development of additional loss dispersions associated with the interphase. Moreover, the model yields a fiber reinforcement efficiency factor, K, which gives a quantitative measure of adhesion. The contact angle of PBA and PCHM grafted high density polyethylene (HDPE) films are also included and are compared to the contact angle of plasma treated fibers. The results indicate that PBA and PCHM grafts enhance adhesion through polymer graft/matrix interactions, not simply by improved wetting. 相似文献
84.
Angela M. Gutierrez Rohit Bhandari Jiaying Weng Arnold Stromberg Thomas D. Dziubla J. Zach Hilt 《应用聚合物科学杂志》2020,137(37):49109
In this work, the development of novel magnetic nanocomposite microparticles (MNMs) via free radical polymerization for their application in the remediation of contaminated water is presented. Acrylated plant-based polyphenols, curcumin multiacrylate (CMA) and quercetin multiacrylate (QMA), were incorporated as functional monomers to create high affinity binding sites for the capture of polychlorinated biphenyls (PCBs), as a model pollutant. The MNMs were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, dynamic light scattering, and UV–visible spectroscopy. The affinity of these novel materials for PCB 126 was evaluated and fitted to the nonlinear Langmuir model to determine binding affinities (KD). The results suggest the presence of the polyphenolic moieties enhances the binding affinity for PCB 126, with KD values comparable to that of antibodies. This demonstrates that these nanocomposite materials have promising potential as environmental remediation adsorbents for harmful contaminants. 相似文献
85.
Thomas Janette A.; Arnold John R.P.; Basran Jaswir; Andrews Julie; Roberts Gordon C.K.; Birdsall Berry; Feeney James 《Protein engineering, design & selection : PEDS》1994,7(6):783-792
A mutant of Lactobacillus casei dihydrofolate reductase hasbeen constructed in which Thr63, a residue which interacts withthe 2'-phosphate group of the bound coenzyme, is replaced byalanine. This substitution does not affect kcat, but producesan 800-fold increase in the Km for NADPH, which reflects dissociationof NADPH from the enzyme-NADPH-tetrahydrofolate complex, anda 625-fold increase (corresponding to 3.8 kcal/mol) in the dissociationconstant for the enzyme-NADPH complex. The difference in magnitudeof these effects indicates a small effect of the substitutionon the negative cooperativity between NADPH and tetrahydrofolate.Stopped-flow studies of the kinetics of NADPH binding show thatthe weaker binding arises predominantly from a decrease in theassociation rate constant. NMR spectroscopy was used to comparethe structures of the mutant and wild-type enzymes in solution,in their complexes with methotrexate and with methotrexate andNADPH. This showed that only minimal structural changes resultfrom the mutation; a total of 47 residues were monitored fromtheir resolved 1H resonances, and of these nine in the binarycomplex and six in the ternary differed in chemical shift betweenmutant and wild-type enzyme. These affected residues are confinedto the immediate vicinity of residue 63. There is a substantialdifference in the 31P chemical shift of the 2'-phosphate ofthe bound coenzyme, reflecting the loss of the interaction withthe side chain of Thr63. The only changes in nuclear Overhausereffects (NOEs) observed were decreases in the intensity of NOEsbetween protons of the adenine ring of the bound coenzyme andthe nearby residues Leu62 and Ile102, showing that the substitutionof Thr63 does cause a change in the position or orientationof the adenine ring in its binding site. 相似文献
86.
George W. Johnson Arnold F. Bertelsen Jan Nossen 《American Institute of Chemical Engineers》2009,55(11):2788-2795
A new two‐phase roll wave model is compared with data from high pressure two‐phase stratified pipe flow experiments. Results from 754 experiments, including mean wave speed, wave height, pressure gradient, holdup and wave length, are compared with theoretical results. The model was able to predict these physical quantities with good accuracy without introducing any new empirically determined quantities to the two‐fluid model equations. This was possible by finding the unique theoretical limit for nonlinear roll amplitude and applying a new approach for determining the friction factor at the gas‐liquid interface. © 2009 American Institute of Chemical Engineers AIChE J, 2009 相似文献
87.
This paper presents a numerical validation of the new equations for the rail-tie structure, derived recently by Kerr and Zarembski [Acta Mech. 40, 253–276 (1981)], for the track response in the lateral plane. Equations of this type are needed for the analysis of track buckling and lateral track dynamics. This is achieved by comparing the results based on the new equations with those of a finite-element analysis, for a 24 m (80 ft) long rail-tie structure. The comparison revealed very close agreement for the lateral deflections and bending moments, for a wide range of rail and tie spacings currently in use, which includes narrow and wide gauge tracks. The effect of the boundaries, where the rail-tie structure experiences a discontinuity, was found to be negligibly small. The findings show that the new equations are suitable for the analysis of cross-tie tracks in the lateral plane. They also confirm that, for tracks with stiff fasteners, the use of the standard beam bending equation with a ‘substitute’ track bending stiffness is of questionable validity. 相似文献
88.
89.
W. Arnold 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1925,49(4):213-214
Ohne Zusammenfassung 相似文献
90.
Mass Spectra of Alicyclic Compounds. VI. Mass Spectrometric Fragmentation of Chloroacetic Esters of the trans-1,4-Cyclohexanediol The electron impact mass spectra of some chloroacetic esters of trans-1,4-cyclo-hexanediol and of cyclohexanol are discussed. It was found that the fragmentation process in these compounds is determined by the number of chlorine atoms in the acid and the interactions between the two functional groups. 相似文献