全文获取类型
收费全文 | 3285篇 |
免费 | 92篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 76篇 |
综合类 | 4篇 |
化学工业 | 1052篇 |
金属工艺 | 54篇 |
机械仪表 | 30篇 |
建筑科学 | 203篇 |
矿业工程 | 31篇 |
能源动力 | 36篇 |
轻工业 | 382篇 |
水利工程 | 10篇 |
石油天然气 | 14篇 |
无线电 | 183篇 |
一般工业技术 | 474篇 |
冶金工业 | 343篇 |
原子能技术 | 36篇 |
自动化技术 | 450篇 |
出版年
2022年 | 32篇 |
2021年 | 45篇 |
2020年 | 34篇 |
2019年 | 33篇 |
2018年 | 49篇 |
2017年 | 43篇 |
2016年 | 66篇 |
2015年 | 90篇 |
2014年 | 77篇 |
2013年 | 124篇 |
2012年 | 125篇 |
2011年 | 169篇 |
2010年 | 115篇 |
2009年 | 117篇 |
2008年 | 122篇 |
2007年 | 144篇 |
2006年 | 126篇 |
2005年 | 117篇 |
2004年 | 110篇 |
2003年 | 78篇 |
2002年 | 81篇 |
2001年 | 66篇 |
2000年 | 55篇 |
1999年 | 58篇 |
1998年 | 109篇 |
1997年 | 80篇 |
1996年 | 70篇 |
1995年 | 66篇 |
1994年 | 72篇 |
1993年 | 45篇 |
1992年 | 47篇 |
1991年 | 43篇 |
1990年 | 35篇 |
1989年 | 36篇 |
1988年 | 28篇 |
1987年 | 44篇 |
1986年 | 33篇 |
1985年 | 40篇 |
1984年 | 40篇 |
1983年 | 38篇 |
1982年 | 35篇 |
1981年 | 28篇 |
1980年 | 30篇 |
1978年 | 27篇 |
1977年 | 32篇 |
1976年 | 34篇 |
1975年 | 40篇 |
1974年 | 24篇 |
1973年 | 25篇 |
1970年 | 33篇 |
排序方式: 共有3378条查询结果,搜索用时 15 毫秒
61.
Filak LK Mühlgassner G Bacher F Roller A Galanski M Jakupec MA Keppler BK Arion VB 《Organometallics》2011,30(2):273-283
The synthesis of new modified indolo[3,2-c]quinoline ligands L(1)-L(8) with metal-binding sites is reported. By coordination to ruthenium- and osmium-arene moieties 16 complexes of the type [(η(6)-p-cymene)M(L)Cl]Cl (1a,b-8a,b), where M is Ru(II) or Os(II) and L is L(1)-L(8), have been prepared. All compounds were comprehensively characterized by elemental analysis, electrospray ionization mass spectrometry, IR, UV-vis, and NMR spectroscopy, thermogravimetric analysis, and single-crystal X-ray diffraction (2a, 4a, 4b, 5a, 7a, and 7b). The complexes were tested for antiproliferative activity in vitro in three human cancer cell lines, namely, CH1 (ovarian carcinoma), SW480 (colon adenocarcinoma), and A549 (non-small-cell lung cancer), yielding IC(50) values in the submicromolar or low micromolar range. 相似文献
62.
Herbert A. Mang Gerhard Höfinger Xin Jia 《Computer Methods in Applied Mechanics and Engineering》2011,200(13-16):1558-1567
The scientific motivation for this paper is lack of clarity about the interdependency of primary and initial secondary equilibrium paths in the frame of sensitivity analysis of elastic structures. The investigation of this interdependency comprises of the following four cases: (1) nonlinear primary path, nonlinear stability problem, (2) linear primary path, nonlinear stability problem, (3) nonlinear primary path, linear stability problem, and (4) linear primary path, linear stability problem. The consistently linearized eigenproblem is used for differentiation of two classes of nonlinear stability problems with markedly different characteristics of both the prebuckling and the postbuckling behavior. For one of them, e.g. zero-stiffness postbuckling is impossible. For the other one, which is restricted to a prebuckling regime with axial deformations only, sensitivity analysis of the initial postbuckling behavior either exhibits its continuous improvement or its continuous deterioration, depending on whether the bifurcation point diverges from or converges to the snap-through point. In other words, a monotonic variation of the design parameter cannot result in a non-monotonic change of the initial postbuckling behavior. The practical motivation for this work is to explore the mechanical reasons for qualitatively different modes of transition from imperfection sensitivity to insensitivity in the course of sensitivity analysis for the purpose of improving the postbuckling behavior of structures by means of minor design changes. Results from a numerical investigation corroborate the theoretical findings. 相似文献
63.
In performance evaluation or supervisory control, we often encounter problems of determining the maximum or minimum string execution time for a finite language when estimating the worst-case or best-case performance. It has been shown in the literature that the time complexity for computing the maximum string execution time for a finite language is polynomial with respect to the size of an automaton recognizer of that language and the dimension of the corresponding resource matrices. In this paper we provide a more efficient algorithm to compute such maximum string execution time. Then we show that it is NP-complete to determine the minimum string execution time. 相似文献
64.
Tunable Quantum Confinement in Ultrathin,Optically Active Semiconductor Nanowires Via Reverse‐Reaction Growth 下载免费PDF全文
65.
Amna Youssef Ramzy Ahmed Mohammed Moneeb El‐Sabbagh Leif Steuernagel Gerhard Ziegmann Dieter Meiners 《应用聚合物科学杂志》2014,131(3)
The presented study investigates the flow length and the corresponding fiber content distribution in the injection‐moulded natural fiber reinforced thermoplastics and its relation to fiber type and processing parameters such as injection pressure, temperature, injection rate and mould tempering by increasing die temperature. In this research, polypropylene compounds with nominally 30 wt % hemp and sisal fibers are investigated. The influence of the injection pressure (500 and 1000 bar), melt temperature (180°C, 200°C, and 220°C), and die temperature (23°C and 80°C) on the fiber content distribution all over the sample is investigated. An increasing linear trend of fiber content along the spiral length is observed as an evidence of a fiber/polymer multiflow system. A pattern for fiber content distribution with respect to the fiber length along the injected spiral can be distinguished, where the longer fibers are usually found at the end of the injected part and the shorter fibers remain near mould entrance point. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39861. 相似文献
66.
Investigations on Potato Pulp as a Dietary Fiber Source. Composition of Potato Pulp After Influence of Pectinases and Cellulases and Enzymatic Degradation of Starch. The composition of alcohol insoluble substances (AIS) of potato pulp have been investigated after succesive degradation with different pectolytic and cellulolytic enzymes followed by starch degrading enzymes. The pretreatment with pectinase/cellulase combinations has a significant influence on the amount and the properties of the residues after starch degradation. Furthermore the most important changes in the composition were found in the receiving residues after action of amylolytic enzymes. A correlation exists between the content of residual starch in the residues and the action of the cell wall degrading enzymes. The amount of residual starch correlates negatively with the intensity of cell wall degradation. The enzymatic susceptibility of starch depends on the damage of cell wall of potato pulp, especially on the degree of degradation of the cellulose. The water binding capacity decreases intensively after action of pectinase/cellulase combinations. The treatment with amylolytic enzymes causes only a negligible variation of the water binding capacity. 相似文献
67.
Jrg Hofmann Gerhard Just Wilhelm Pritzkow 《Advanced Synthesis \u0026amp; Catalysis》1991,333(1):67-71
The title compounds were prepared from 2,4-dioxohexahydro-triazine (DHT) and the corresponding acid chlorides in the presence of sulphuric acid. They are active acylating agents against piperidine in dioxane as the solvent. Only the diacyl derivatives of DHT with acyl chain lengths up to C6 react with aqueous solutions of sodium perborate forming the corresponding peroxy acids. 相似文献
68.
Dr. Markella Konstantinidou Francesca Magari Fandi Sutanto Dr. Jörg Haupenthal Dr. Varsha R. Jumde Dr. M. Yagiz Ünver Prof. Dr. Andreas Heine Dr. Carlos Jamie Camacho Prof. Dr. Anna K. H. Hirsch Prof. Dr. Gerhard Klebe Prof. Dr. Alexander Dömling 《ChemMedChem》2020,15(8):680-684
Pharmacophore searches that include anchors, fragments contributing above average to receptor binding, combined with one-step syntheses are a powerful approach for the fast discovery of novel bioactive molecules. Here, we are presenting a pipeline for the rapid and efficient discovery of aspartyl protease inhibitors. First, we hypothesized that hydrazine could be a multi-valent warhead to interact with the active site Asp carboxylic acids. We incorporated the hydrazine anchor in a multicomponent reaction and created a large virtual library of hydrazine derivatives synthetically accessible in one-step. Next, we performed anchor-based pharmacophore screening of the libraries and resynthesized top-ranked compounds. The inhibitory potency of the molecules was finally assessed by an enzyme activity assay and the binding mode confirmed by several soaked crystal structures supporting the validity of the hypothesis and approach. The herein reported pipeline of tools will be of general value for the rapid generation of receptor binders beyond Asp proteases. 相似文献
69.
Flavins and Chinamoyl Derivatives in Relation to the Light-induced Leaf Opening in Albizia julibrissin In search of blue-light photoreceptors for light-induced leaf opening we isolated from the aqueous extract of Albizia julibrissin Durazz. two flavins by adsorption on XAD-4 and separation with HPLC. One sample was identified as riboflavin 1a. In the hydrolysate of the second flavin fraction we found another dimethylisoalloxazine with a C5-side chain. Furthermore we isolated the cinnamoyl derivatives 3-O-(4-hydroxy-trans-cinnamoyl) quinic acid 2 and 3-O-(3,4-dihydroxy-trans-cinnamoyl)-4-O-malonyl-quinic acid 3 which formed charge transfer complexes with the flavins in the XAD-fraction. As a model complex we examined the absorption behaviour of the complex between riboflavin and chlorogenic acid. Using the association constant, we calculated the absorption spectrum and could show that a complex between a flavin and a phenolic compound is a possible blue-light photoreceptor for the light-induced leaf opening in Albizia julibrissin. 相似文献
70.
Xiao Junbing Yan Hongjie Liu Liu Möller Felix Hu Zhiwen Unger Sebastian 《Metallurgical and Materials Transactions B》2019,50(6):3002-3011
Metallurgical and Materials Transactions B - Spout height is a widely used parameter to quantitatively analyze the performance of the submerged gas injection in industrial applications. However,... 相似文献