全文获取类型
收费全文 | 30231篇 |
免费 | 2619篇 |
国内免费 | 1315篇 |
专业分类
电工技术 | 1696篇 |
技术理论 | 1篇 |
综合类 | 1768篇 |
化学工业 | 5218篇 |
金属工艺 | 1777篇 |
机械仪表 | 1778篇 |
建筑科学 | 2473篇 |
矿业工程 | 893篇 |
能源动力 | 923篇 |
轻工业 | 2183篇 |
水利工程 | 536篇 |
石油天然气 | 1471篇 |
武器工业 | 256篇 |
无线电 | 3411篇 |
一般工业技术 | 3793篇 |
冶金工业 | 1379篇 |
原子能技术 | 389篇 |
自动化技术 | 4220篇 |
出版年
2024年 | 147篇 |
2023年 | 578篇 |
2022年 | 1031篇 |
2021年 | 1405篇 |
2020年 | 1105篇 |
2019年 | 849篇 |
2018年 | 931篇 |
2017年 | 1116篇 |
2016年 | 943篇 |
2015年 | 1243篇 |
2014年 | 1504篇 |
2013年 | 1815篇 |
2012年 | 1901篇 |
2011年 | 2079篇 |
2010年 | 1765篇 |
2009年 | 1664篇 |
2008年 | 1584篇 |
2007年 | 1449篇 |
2006年 | 1456篇 |
2005年 | 1393篇 |
2004年 | 886篇 |
2003年 | 773篇 |
2002年 | 692篇 |
2001年 | 567篇 |
2000年 | 623篇 |
1999年 | 720篇 |
1998年 | 668篇 |
1997年 | 520篇 |
1996年 | 561篇 |
1995年 | 466篇 |
1994年 | 380篇 |
1993年 | 293篇 |
1992年 | 234篇 |
1991年 | 195篇 |
1990年 | 134篇 |
1989年 | 112篇 |
1988年 | 106篇 |
1987年 | 68篇 |
1986年 | 47篇 |
1985年 | 36篇 |
1984年 | 33篇 |
1983年 | 17篇 |
1982年 | 13篇 |
1981年 | 13篇 |
1980年 | 13篇 |
1979年 | 12篇 |
1978年 | 4篇 |
1976年 | 5篇 |
1972年 | 3篇 |
1959年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Minxue Pan Xuandong Li 《International Journal on Software Tools for Technology Transfer (STTT)》2012,14(6):639-651
Message Sequence Chart (MSC) is a graphical and textual language for describing the interactions between system components, and MSC specifications (MSSs) are a combination of a set of basic MSCs (bMSCs) and a High-level MSC that describes potentially iterating and branching system behavior by specifying the compositions of basic MSCs, which offer an intuitive and visual way of specifying design requirements. With concurrent, timing, and asynchronous properties, MSSs are amenable to errors, and their analysis is important and difficult. This paper deals with timing analysis of MSC specifications with asynchronous concatenation. For an MSC specification, we require that for any loop, its first node be flexible in execution time and its any associated external timing constraint be enforced on the entire loop. Such an MSC specification is called a flexible loop-closed MSC specification (FLMSS). We show that for FLMSSs, the reachability analysis and bounded delay analysis problems can be solved efficiently by linear programming. The solutions have been implemented into our tool TASS and evaluated by experiments. 相似文献
72.
In this paper, a cooperative control analysis and design method is investigated for heterogeneous dynamical systems that may be of arbitrary relative degree or nonminimum-phase or both. To achieve consensus or cooperative stability, a negative value of input-feedforward passivity index is used to accommodate and analyze such systems, and the magnitude of the index value is also used as the impact coefficient to quantify the impacts of heterogeneous dynamics of these systems on their networked operations. Physical-system-level designs are explicitly carried out to make individual linear and nonlinear systems (which are either feedback linearizable or nonminimum phase of certain form) become passivity-short and to embed one pure integrator into their input–output dynamics. The network-level distributed control can simply be chosen without any knowledge of the heterogeneous dynamics but with only information of an upper bound on their impact coefficients. It is shown, using the impact equivalence principle, that these controls separately designed but implemented together always ensure either local or global consensus and that a global non-trivial consensus emerges if and only if the information network has at least one globally reachable node or is varying but cumulatively connected. The proposed methodology of fully modularized designs unravels complexity of analyzing and designing cyber–physical systems and enables their plug-and-play into networked operations. 相似文献
73.
74.
本文主要叙述了环氧-丙烯酸酯聚合乳液的合成,以及该乳液粘合剂的配制;讨论了该乳液粘合剂的粘合性能及耐水、耐溶剂性能。 相似文献
75.
在并行测试的研究中对于任务的测试次序一直是个研究重点及难题。用时间Petri网建立关于并行测试系统的模型,并首次用元胞遗传算法(CAGA)对模型中的变迁序列进行搜索,快速得到最好的测试序列。通过仿真结果表明,该算法展示了很好的收敛效果,并且与已有的研究成果相比更具优势。 相似文献
76.
针对云系统服务器之间共享策略文件所面临的完整性安全威胁,提出一种新的基于固件的策略安全机制。该机制可在云系统服务器平台之间安全且快速地进行共享策略文件交互,并可对共享策略文件进行完整性校验,进而提高协同工作的服务器所共享策略文件的安全性。实验结果表明,该机制有效实现了云系统环境下共享策略文件的完整性安全,同时提高了云系统管理员的管理效率。 相似文献
77.
The hydrogenation of diene‐based polymers via diimide is a very attractive alternative to the conventional catalytic hydrogenation route based on gaseous molecular hydrogen. However, serious crosslinking always accompanies it and limits the end‐use properties of the polymers. Gel formation in polymers that are hydrogenated via diimide has been investigated in detail through an inspection of all the chemical reactions involved in the process. The results indicate that hydrogen peroxide decomposition, some reactions related to oxygen, and the redox reaction between hydrogen peroxide and hydrazine are capable of generating radicals. However, radicals generated in the aqueous phase do not appear to initiate the crosslinking of diene‐based polymers in the latex form. It is proposed that the primary radicals giving rise to crosslinking are generated in the polymer phase in situ, and the step responsible for generating these organic radicals is possibly the diimide disproportionation reaction. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1122–1125, 2005 相似文献
78.
本文对高聚合度聚氯乙烯(H-PVC)的发展及其优异的物理机械性能作了简要介绍;着重分析了H-PVC的加工性能和表征方法,并讨论了分子特性和颗料特性及加工组成、加工条件对加工性能的影响,提出了改进H-PVC加工性能的方法。 相似文献
79.
80.
Frank N. Jones Weidian Shen Stanley M. Smith Zhihua Huang Rose A. Ryntz 《Progress in Organic Coatings》1997,34(1-4):119-129
Scanning probe microscopy (SPM) is in a period of rapid development. It shows great promise for characterizing coating surfaces. This paper describes modification of an SPM so that it can be used to mar the surfaces of coatings under controlled conditions and to characterize the mars. Mar resistance of coatings is analyzed in terms of a ‘three response, two mechanism model.' The three responses (fracture, elastic, and plastic) can be measured quantitatively using the SPM. Of the three responses, only two (fracture and plastic deformation) are marring mechanisms – elastic deformations recover instantaneously. In some cases mars resulting from plastic deformation may recover slowly with time or with immersion in water; this phenomenon is attributed to viscoelastic creep. Microhardness is also measured with the modified SPM. Some thermoset coatings appear to be substantially harder near their surfaces than in the mass of material, and such materials may respond quite differently to stress applied at different levels near the surface. This finding has important implications for all coating properties that are strongly influenced by the surface. A quantity called ‘micro mar resistance' is defined. It may be useful for comparing different coatings under specified conditions of marring. However, there can be no single quantity that expresses ‘mar resistance' of a coating under all conditions. 相似文献