全文获取类型
收费全文 | 11832篇 |
免费 | 499篇 |
国内免费 | 648篇 |
专业分类
电工技术 | 191篇 |
综合类 | 396篇 |
化学工业 | 140篇 |
金属工艺 | 224篇 |
机械仪表 | 548篇 |
建筑科学 | 3575篇 |
矿业工程 | 105篇 |
能源动力 | 63篇 |
轻工业 | 86篇 |
水利工程 | 14篇 |
石油天然气 | 90篇 |
武器工业 | 62篇 |
无线电 | 830篇 |
一般工业技术 | 248篇 |
冶金工业 | 64篇 |
原子能技术 | 59篇 |
自动化技术 | 6284篇 |
出版年
2024年 | 11篇 |
2023年 | 46篇 |
2022年 | 81篇 |
2021年 | 100篇 |
2020年 | 105篇 |
2019年 | 86篇 |
2018年 | 139篇 |
2017年 | 143篇 |
2016年 | 272篇 |
2015年 | 313篇 |
2014年 | 594篇 |
2013年 | 472篇 |
2012年 | 662篇 |
2011年 | 876篇 |
2010年 | 672篇 |
2009年 | 620篇 |
2008年 | 769篇 |
2007年 | 991篇 |
2006年 | 951篇 |
2005年 | 898篇 |
2004年 | 761篇 |
2003年 | 817篇 |
2002年 | 483篇 |
2001年 | 381篇 |
2000年 | 344篇 |
1999年 | 307篇 |
1998年 | 209篇 |
1997年 | 146篇 |
1996年 | 146篇 |
1995年 | 101篇 |
1994年 | 83篇 |
1993年 | 67篇 |
1992年 | 57篇 |
1991年 | 37篇 |
1990年 | 27篇 |
1989年 | 26篇 |
1988年 | 22篇 |
1987年 | 20篇 |
1986年 | 18篇 |
1985年 | 21篇 |
1984年 | 18篇 |
1983年 | 20篇 |
1982年 | 16篇 |
1981年 | 14篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1974年 | 3篇 |
1971年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
11.
国家标准GB T175 44规定了软件包的质量要求及针对这些要求如何对软件包进行测试的细则。质量要求从产品描述、用户文档、程序及数据三个方面进行了规定 ,测试细则依据这些规定制定。ISO IEC912 6 (1991)版由ISO IEC 912 6 (软件产品质量 )和ISO IEC14 5 98(软件产品评测 )两个标准代替 ,ISO IEC912 6表述了软件产品质量的内部质量、外部质量和使用中的质量 ,规定了内部质量、外部质量的六个质量特性 ,并细分为 2 1个子特性 ,使用中的质量规定了四个使用质量特性 ,使用质量是指六个软件产品质量特性的综合效果。进行软件测试时 ,可以依据GB T175 44中的规定组织测试过程再结合ISO IEC912 6中的质量特性及子特性的规定确定测试需求的内容和测试的重点 ,利用ISO IEC912 6质量的规定建立质量评级的标准。 相似文献
12.
13.
14.
15.
虚拟仪器(VI)将计算机采集测试分析引入到电子测量领域,用数字化和软件技术极大地提高了测量的灵活性。而VI远程测控系统是网络技术、通信技术一计算机虚拟技术结合的产物。远程控制技术能够使操作突破地域的限制,已在网络环境下PⅢ工控机上实现。 相似文献
16.
17.
中频软件无线电系统的FPGA实现方案 总被引:11,自引:2,他引:9
软件无线电作为无线通信技术的又一次革命,是目前通信领域中最为重要的研究方向之一。本文研究职频软件无线电的实现方案,并用FPGA设计和实现了基于此方案的中频软件无线电的通用硬件平台。 相似文献
18.
M. Lipow 《Quality and Reliability Engineering International》1985,1(1):27-35
This paper presents a demonstration of a methodology for fault removal during software development. The methodology encompasses the entire development history, from system and software requirements generation to system test. Thus it considers not only the faults during software testing after formal configuration controls have been invoked, but also the faults discovered prior to that phase: during system and software requirements generation, preliminary design, detailed design and code and unit testing. The agents for fault discovery used in verification and validation are called activities, techniques and tools (AT & Ts) in this paper, each having a certain maximum potential or capability for fault discovery. The AT & Ts considered include the usual specification review activities, and also certain tools not normally applied in ‘standard’ software development, such as automated requirements aids. Application of the methodology yields numbers of residual faults as of each phase of development, including those remaining to be discovered during operations and maintenance. Some previous experience and data on residual faults correspond to these results, indicating that the methodology and choice of parameters are reasonable. The methodology also allows one to calculate a relative loss due to delay in fault discovery, which, as is well known, rises rapidly when faults are not discovered during the phase in which they are generated. 相似文献
19.
Nikos Antonopoulos Patrick Linke Antonis Kokossis 《Chemical Engineering Communications》2005,192(10):1258-1271
This article presents a GRID framework for distributed computations in the chemical process industries. We advocate a generic agent-based GRID environment in which chemical processes can be represented, simulated, and optimized as a set of autonomous, collaborative software agents. The framework features numerous advantages in terms of scalability, software reuse, security, and distributed resource discovery and utilization. It is a novel example of how advanced distributed techniques and paradigms can be elegantly applied in the area of chemical engineering to support distributed computations and discovery functions in chemical process engineering. A prototype implementation of the proposed framework for chemical process design is presented to illustrate the concepts. 相似文献
20.
Jeongsoo Choi 《Polymer》2005,46(23):9725-9735
A series of star-branched poly(ε-caprolactone)s (SPCLs) was synthesized with structural variation of the arm numbers and lengths through ring-opening polymerization under bulk condition. Arm numbers were varied to be 3, 4, and 6 by using multifunctional initiating cores such as trimethylol propane, pentaerythritol, and dipentaerythritol, respectively. The lengths of the poly(ε-caprolactone) arms were varied by controlling the molar ratio of monomer-to-initiating hydroxyl group molar ratio ([CL]0/[-OH]0=5, 10, 15). Molecular weights were determined by both 1H NMR end-group analysis and MALDI-TOF mass spectrometry, which gave reasonably consistent values. On the contrary, the GPC method failed to give accurate values of molecular weight of SPCLs due to the discrepancy with the linear standard. The branching architecture of SPCLs was evaluated by the branching ratio, g, which is the ratio of the mean-square radius of SPCL to that of liner counterpart, linear poly(ε-caprolactone) (LPCL), which is of the same chemistry and having the same molecular weight. The radii of gyration of SPCLs and LPCLs were determined using small-angle X-ray scattering (SAXS) from the initial slopes of Zimm plots, represented as 1/I(q) vs q2 with I(q) and q being the scattered intensity and scattering vector, respectively. The g values were observed to decrease with increasing arm numbers, indicating more compact molecular structure for SPCLs with higher arm numbers, while no such effect was observed for arm length variation. Thermal properties as well as the degree of crystallinity of SPCLs were found to be also dependent on structural variations. The melting points and the degradation temperatures were observed to increase with increasing arm lengths but with constant arm number. On the other hand, arm number variation with constant arm length gave no such changes to the thermal transitions of SPCLs. However, for the SPCLs with equivalent molecular weights, the degree of crystallinity was found to decrease with increasing arm numbers. 相似文献