全文获取类型
收费全文 | 7464篇 |
免费 | 466篇 |
国内免费 | 15篇 |
专业分类
电工技术 | 229篇 |
综合类 | 36篇 |
化学工业 | 1763篇 |
金属工艺 | 226篇 |
机械仪表 | 211篇 |
建筑科学 | 238篇 |
矿业工程 | 38篇 |
能源动力 | 273篇 |
轻工业 | 1068篇 |
水利工程 | 64篇 |
石油天然气 | 39篇 |
武器工业 | 1篇 |
无线电 | 462篇 |
一般工业技术 | 1696篇 |
冶金工业 | 236篇 |
原子能技术 | 97篇 |
自动化技术 | 1268篇 |
出版年
2023年 | 63篇 |
2022年 | 66篇 |
2021年 | 199篇 |
2020年 | 153篇 |
2019年 | 179篇 |
2018年 | 291篇 |
2017年 | 278篇 |
2016年 | 311篇 |
2015年 | 248篇 |
2014年 | 373篇 |
2013年 | 749篇 |
2012年 | 494篇 |
2011年 | 606篇 |
2010年 | 469篇 |
2009年 | 379篇 |
2008年 | 306篇 |
2007年 | 282篇 |
2006年 | 182篇 |
2005年 | 196篇 |
2004年 | 125篇 |
2003年 | 134篇 |
2002年 | 157篇 |
2001年 | 119篇 |
2000年 | 103篇 |
1999年 | 74篇 |
1998年 | 98篇 |
1997年 | 79篇 |
1996年 | 74篇 |
1995年 | 57篇 |
1994年 | 59篇 |
1993年 | 60篇 |
1992年 | 49篇 |
1991年 | 38篇 |
1990年 | 39篇 |
1989年 | 40篇 |
1988年 | 27篇 |
1986年 | 24篇 |
1985年 | 52篇 |
1984年 | 63篇 |
1983年 | 53篇 |
1982年 | 49篇 |
1981年 | 70篇 |
1980年 | 57篇 |
1979年 | 51篇 |
1978年 | 43篇 |
1977年 | 37篇 |
1976年 | 51篇 |
1975年 | 36篇 |
1974年 | 25篇 |
1973年 | 38篇 |
排序方式: 共有7945条查询结果,搜索用时 15 毫秒
71.
Dual approach to multiple authorship in the study of collaboration/scientific output relationship 总被引:3,自引:0,他引:3
This paper presents an empirical study of the relations between scientific output and collaboration performed on two scales: (1) an individual scale, for members of a study model, and (2) a group scale, for three samples varying in the level of productivity. The rank approach was applied in the preparation of the study model resulting in the selection of a set of the most prolific authors. In the course of that process, multiple authorship problem was solved by a dual approach, consisting of normal count and modified straight count procedures. As shown by the analysis of collaborative patterns, either on individual or on group scales, scientific output is highly dependent on the frequency of collaboration among the same authors. Expressed as the collaboration measure, it might serve as an indicator in comparative analyses of scientific productivity in a given field of science. 相似文献
72.
This paper studies the behavior of motions of large-scale (LS) semistate systems (SSS) governed byP
i
(t)x
i
=M
i
(t,x
i
)x
i
+f
i
(t)+h
i
(t, x), i=1,2,...,s, =(x
1
T
x
2
T
x
s
T
)T, where matricesP
i
(t) are singular. Using Lyapunov's approach and the tools for LS system analysis, a variant of attractivity and ultimate boundedness of appropriate time-variable sets are investigated. The results are based on a specific choice of the aggregate functions. It is assumed that the reduction of equations to a normal form of lower order is inconvenient. The aggregation-decomposition approach used in this paper reduces the dimensionality of an aggregate matrix of the system to the number of its systems. Motion properties of LS systems are deduced from the properties of its isolated subsystems, the character of interconnections, and the conditions imposed on the system aggregate matrix. Sufficient algebraic conditions for the above-mentioned motion properties are developed. 相似文献
73.
The magnetic structure of a vortex in the presence of an anisotropic inhomogeneity distribution is calculated within the London model. The anisotropic supercurrent pattern consists of closed current loops, superimposed on a backflow pattern. The nonvanishing current density at the vortex core gives rise to an intrinsic Lorentz force identical with the pinning force resulting from the spatial variation of the vortex self-energy. 相似文献
74.
Pori Maja Arčon Iztok Dasireddy Venkata D. B. C. Likozar Blaž Orel Zorica Crnjak Marinšek Marjan 《Catalysis Letters》2021,151(11):3114-3134
Catalysis Letters - Industrial Cu/ZnO/Al2O3 or novel rate catalysts, prepared with a photochemical deposition method, were studied under functional CH3OH synthesis conditions at the set temperature... 相似文献
75.
Galina M. Viryasova Ekaterina A. Golenkina Tibor Hianik Nataliya V. Soshnikova Nina G. Dolinnaya Tatjana V. Gaponova Yulia M. Romanova Galina F. Sudina 《International journal of molecular sciences》2021,22(5)
Neutrophil-mediated innate host defense mechanisms include pathogen elimination through bacterial phagocytosis, which activates the 5-lipoxygenase (5-LOX) product synthesis. Here, we studied the effect of synthetic oligodeoxyribonucleotides (ODNs), which mimic the receptor-recognized sites of bacterial (CpG-ODNs) and genomic (G-rich ODNs) DNAs released from the inflammatory area, on the neutrophil functions after cell stimulation with Salmonella typhimurium. A possible mechanism for ODN recognition by Toll-like receptor 9 (TLR9) and RAGE receptor has been proposed. We found for the first time that the combination of the magic peptide LRR11 from the leucine-rich repeat (LRR) of TLR9 with the CpG-ODNs modulates the uptake and signaling from ODNs, in particular, dramatically stimulates 5-LOX pathway. Using thickness shear mode acoustic method, we confirmed the specific binding of CpG-ODNs, but not G-rich ODN, to LRR11. The RAGE receptor has been shown to play an important role in promoting ODN uptake. Thus, FPS-ZM1, a high-affinity RAGE inhibitor, suppresses the synthesis of 5-LOX products and reduces the uptake of ODNs by neutrophils; the inhibitor effect being abolished by the addition of LRR11. The results obtained revealed that the studied peptide-ODN complexes possess high biological activity and can be promising for the development of effective vaccine adjuvants and antimicrobial therapeutics. 相似文献
76.
应用有限元成形分析软件,对轮辐翻边成形过程进行了模拟分析,探讨了不同冲模斜角对翻边变形的影响,以控制变形冲力和轮辐变形区应变分布为目标,对冲模斜角参数进行优化。 相似文献
77.
Petar R. Dvornic Milutin N. Govedarica Jelena D. Jovanović Vesna V. Gerov Mališa P. Antić 《Polymer Bulletin》1995,35(5):539-545
Summary A new general procedure for preparation of functionalized oligopolysiloxanes of predetermined molecular weight is described. It utilizes heterogeneously catalyzed siloxane equilibration polymerization reactions which do not require troublesome and sometimes difficult post-preparative work-up procedures usually encountered with the well known homogeneously catalyzed corresponding reactions. The method is described using as example the preparation of , -telechelic vinyldimethylsiloxy-oligopolydimethylsiloxanes from octamethylcyclotetrasiloxane and 1,3-divinyltetramethyldisiloxane, but reference to the preparations of trimethylsiloxy-, dimethylsiloxy-and carboxypropyldimethylsiloxyoligopolydimethylsiloxanes, oligopolymethylhydridosiloxanes or their copolymers is also made. 相似文献
78.
Summary The effect of tert-butyl chloride in the polymerizations of isobutylene carried out in the presence of SnCl4 in dichloromethane at temperatures-20°C and-78°C was investigated. Synthesized polyisobutylene samples showed a bimodal molecular
weight distribution (MWD) and it was found that the weight content of the lowermolecular weight (LMW) fraction increased with
increasing t-BuCl concentration in the polymerization mixture. The effect of ageing of the initiation mixture t-BuCl/SnCl4 in CH2Cl2 prepared in advance on MWD of the PIB samples was also studied. Ageing of the initiation system supports the formation of
the LMW fraction and this oily PIB is the only product of the polymerization at-20°C,
. 相似文献
79.
80.
Oliver R. Ilić 《Journal of Intelligent Manufacturing》2014,25(3):617-628
Manufacturing cell formation is the first step in the design of cellular manufacturing system. The primary objective of this step is to cluster machines into machine cells and parts into part families so that the minimum of intercell trips will be achieved. This paper will be focused on the configuration of machine cells considering three types of initial machine-part matrix: binary (zero-one) matrix, production volume matrix, and operation time matrix. The similarity measure uses only information from these types of matrix. A pure combinatorial programming formulation will be developed to maximize the sum of similarity coefficients between machine/part pairs. An e-Learning tool/application to help industrial students and engineers for enhancing their cell formation capability is proposed. This tool is designed to include a novel similarity coefficient-based heuristic algorithm for solving the cell formation problem. To determine the performance of the proposed tool, comparison is made with a well-known tool along a case study. 相似文献