全文获取类型
收费全文 | 6176篇 |
免费 | 172篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 63篇 |
综合类 | 2篇 |
化学工业 | 1246篇 |
金属工艺 | 77篇 |
机械仪表 | 113篇 |
建筑科学 | 231篇 |
矿业工程 | 7篇 |
能源动力 | 175篇 |
轻工业 | 369篇 |
水利工程 | 28篇 |
石油天然气 | 11篇 |
无线电 | 578篇 |
一般工业技术 | 856篇 |
冶金工业 | 1714篇 |
原子能技术 | 61篇 |
自动化技术 | 823篇 |
出版年
2022年 | 55篇 |
2021年 | 81篇 |
2020年 | 47篇 |
2019年 | 61篇 |
2018年 | 85篇 |
2017年 | 102篇 |
2016年 | 126篇 |
2015年 | 89篇 |
2014年 | 114篇 |
2013年 | 255篇 |
2012年 | 214篇 |
2011年 | 259篇 |
2010年 | 212篇 |
2009年 | 223篇 |
2008年 | 212篇 |
2007年 | 219篇 |
2006年 | 223篇 |
2005年 | 163篇 |
2004年 | 174篇 |
2003年 | 145篇 |
2002年 | 148篇 |
2001年 | 111篇 |
2000年 | 103篇 |
1999年 | 119篇 |
1998年 | 512篇 |
1997年 | 333篇 |
1996年 | 251篇 |
1995年 | 188篇 |
1994年 | 146篇 |
1993年 | 163篇 |
1992年 | 64篇 |
1991年 | 63篇 |
1990年 | 64篇 |
1989年 | 68篇 |
1988年 | 59篇 |
1987年 | 59篇 |
1986年 | 46篇 |
1985年 | 98篇 |
1984年 | 58篇 |
1983年 | 57篇 |
1982年 | 48篇 |
1981年 | 84篇 |
1980年 | 61篇 |
1979年 | 50篇 |
1978年 | 18篇 |
1977年 | 59篇 |
1976年 | 84篇 |
1975年 | 44篇 |
1974年 | 30篇 |
1973年 | 26篇 |
排序方式: 共有6354条查询结果,搜索用时 15 毫秒
61.
Michel Brusin 《Materials and Structures》1990,23(2):79-80
Editorial
All a RILEM technical recommendation should be 相似文献62.
Benjamin Gerard Harouna Souley Ali Michel Zasadzinski Mohamed Darouach 《International Journal of Control, Automation and Systems》2012,10(6):1086-1095
This paper deals with the H ?? filtering problem for a class of nonlinear systems. This class of nonlinear systems is composed of a bilinear part and of a lipschitzian one. The use of an unbiasedness condition for the bilinear part (called quasi unbiasedness condition) permits to parameterize the filter matrices through a single gain. Two LPV (Linear Parameter Varying) extensions of the bounded real lemma are used to solve the filtering problem. This approach reduces the conservatism inherent to the boundedness of the inputs. Then the filtering solution is expressed in terms of LMI (Linear Matrix Inequality) to be verified at the vertices of a polytope. A numerical example is finally given to illustrate our approach. 相似文献
63.
The microstructure and mechanical properties of modified and non-modified stir-cast commercial aluminium alloys A-S7G03 and A-S4G have been investigated. Stir casting of these alloys resulted in spherical and/or rosette shape primary -phase, and the eutectic silicon was broken into miniature needle morphology. This stir-cast structure slightly improved the mechanical properties in comparison to those of conventionally cast alloys, however the fracture of the stir-cast alloys revealed intergranular brittle fracture. The addition of 0.02% strontium, in the form of Al-5 mass% Sr master alloy, during stir casting modified the eutectic silicon into a very fine spheroidal morphology, while the -phase particle showed the same morphology as the stir-cast alloys. This novel structure resulted in significant improvement of mechanical properties. The elongation of the modified stir-cast alloys was five times greater than that of the non-modified one. A transgranular mode of fracture was observed for the modified stircast alloys, moreover smooth ripple and dimple patterns were observed reflecting the high ductility of the modified stir-cast alloys. 相似文献
64.
Electrical conductivity, thermoelectrical power and thermal conductivity measurements on boron carbide samples show that the electrical conductivity follows the small polaron hopping theory and that thermal conductivity occurs by phonon diffusion. The evolution of these properties with carbon content illustrates the particular role played by the 13.3 at% C compound in the phase homogeneity range B10.5C to B4C. The value of the figure of merit (0.85×10–3 K at 1250 K) proves that this particular boron carbide compound could be a very interesting candidate material for high-temperature thermoelectrical conversion. 相似文献
65.
Substitution reactions are an appropriate way to attach chemical functions to polymer chains for improving properties and to diversify the application of polymer materials. The stereoselective substitution of chlorine atoms affords a useful way to plasticize polyvinychloride (PVC) by attaching appropriate plasticizing functions (ester group) such as isooctylthiosalicylate. Thus, the substitution of chlorine atoms of PVC by reactant bearing plasticizing groups was carried out in a continuous mixing apparatus such as a twin screw extruder. This continuous chemical engineering process taking place in the extruder is studied as the function of the residence time distribution (RTD) measured by a UV method. This function combined with the kinetics of the chemical reaction allows to define a new function G as the distribution of the extent of conversion by analogy with the RTD function. 相似文献
66.
The main contribution of the present article consists of new 3D parallel and symmetric thinning schemes which have the following qualities: They are effective and sound, in the sense that they are guaranteed to preserve topology. This guarantee is obtained thanks to a theorem on critical kernels; They are powerful, in the sense that they remove more points, in one iteration, than any other symmetric parallel thinning scheme; They are versatile, as conditions for the preservation of geometrical features (e.g., curve extremities or surface borders) are independent of those accounting for topology preservation; They are efficient: we provide in this article a small set of masks, acting in the grid ?3, that is sufficient, in addition to the classical simple point test, to straightforwardly implement them. 相似文献
67.
Structure and functional complementation of engineered fragments from yeast phosphoglycerate kinase 总被引:1,自引:0,他引:1
Pecorari Frederic; Minard Philippe; Desmadril Michel; Yon Jeannine M. 《Protein engineering, design & selection : PEDS》1993,6(3):313-324
Previous studies have shown that, although the isolated structuraldomains of yeast phosphoglycerate kinase recover a quasi-nativestructure in vitro as well as in vivo, they do not reassociatenor generate a functional enzyme. The aim of this work was firstto study the folding of complementary fragments different fromstructural domains and second to determine the requirementsfor their reassociation and functional complementation. Themethod used for producing rigorously defined fragments consistsof the introduction of a unique cysteinyl residue in the proteinfollowed by a specific cleavage by 5'5'-dithiobis(2-nitrobenzoate)/potassiumcyanide at this residue. Two pairs of complementary fragmentswere thus obtained, 196/97415 and 1248/249415.The structure and stabilities of the different fragments werestudied. The short fragments, i.e. 196 and 249415were found to contain some secondary structure, but to havea low stability. Each large fragment has a high structural contentand a stability close to that of the corresponding domain. Incontrast to that observed with the isolated domains, a weakbut significant complementation was observed for the two pairsof fragments; the pair of fragments 1248/249415recovered 8% of the activity of the native enzyme upon complementation.An independent refolding of the complementary fragments beforereassociation decreased the yield of complementation for thepair of fragments 196/97415, but did not affectthe complementation for the other pair (1248/249415).From the present data and previous work on the isolated domains,it appears that the correct folding of the isolated fragmentsis not a prerequisite for their complementation. 相似文献
68.
Many rate constants of elementary steps on single crystals have been measured. Their pre-exponential factors can now be compared to those calculated by transition state theory. Such a calculation is presented in this Letter with due attention to microscopic reversibility, standard states, and configurational entropy. 相似文献
69.
Michel C Bol A Spinks T Townsend D Bailey D Grootoonk S Jones T 《IEEE transactions on medical imaging》1991,10(3):240-248
The authors have assessed the response function both experimentally and theoretically for two commercial tomographs: CTI 931/08-12 and CTI 953B with and without interplane septa. Monte Carlo simulations were undertaken using the GEANT package from CERN. Spatial resolution (tomographic and axial) was calculated for line sources at various positions in the field of view. Sensitivity and scatter fraction (SF) were calculated for various source geometries as a function of energy discrimination. A very realistic response function in positron emission tomography (PET) is obtained by Monte Carlo methods, using global parameters to account for unsimulated phenomena such as scintillation light transport inside a detector block and its sharing among the various phototubes. Minor discrepancies remain for sensitivity and SF at high energy thresholds and may probably be explained by introducing the observed dispersion in the energy response for the various crystals within a detector block. 相似文献
70.