全文获取类型
收费全文 | 290436篇 |
免费 | 21580篇 |
国内免费 | 11164篇 |
专业分类
电工技术 | 15447篇 |
技术理论 | 31篇 |
综合类 | 17512篇 |
化学工业 | 50345篇 |
金属工艺 | 16944篇 |
机械仪表 | 18470篇 |
建筑科学 | 22977篇 |
矿业工程 | 9565篇 |
能源动力 | 7974篇 |
轻工业 | 16741篇 |
水利工程 | 4806篇 |
石油天然气 | 20324篇 |
武器工业 | 2239篇 |
无线电 | 31545篇 |
一般工业技术 | 34488篇 |
冶金工业 | 15342篇 |
原子能技术 | 2877篇 |
自动化技术 | 35553篇 |
出版年
2024年 | 1223篇 |
2023年 | 4690篇 |
2022年 | 7956篇 |
2021年 | 11527篇 |
2020年 | 8577篇 |
2019年 | 7300篇 |
2018年 | 8193篇 |
2017年 | 9258篇 |
2016年 | 8046篇 |
2015年 | 11228篇 |
2014年 | 13827篇 |
2013年 | 16504篇 |
2012年 | 17823篇 |
2011年 | 19459篇 |
2010年 | 16811篇 |
2009年 | 15955篇 |
2008年 | 15511篇 |
2007年 | 15137篇 |
2006年 | 16016篇 |
2005年 | 14189篇 |
2004年 | 9078篇 |
2003年 | 7926篇 |
2002年 | 7322篇 |
2001年 | 6507篇 |
2000年 | 7121篇 |
1999年 | 8521篇 |
1998年 | 6859篇 |
1997年 | 5839篇 |
1996年 | 5469篇 |
1995年 | 4515篇 |
1994年 | 3764篇 |
1993年 | 2628篇 |
1992年 | 2137篇 |
1991年 | 1602篇 |
1990年 | 1174篇 |
1989年 | 934篇 |
1988年 | 760篇 |
1987年 | 523篇 |
1986年 | 389篇 |
1985年 | 265篇 |
1984年 | 183篇 |
1983年 | 120篇 |
1982年 | 130篇 |
1981年 | 86篇 |
1980年 | 70篇 |
1979年 | 24篇 |
1978年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
991.
992.
微震定位系统中拾震器布阵研究 总被引:1,自引:0,他引:1
对微震监测中拾震器阵列进行科学有效的布置是保证微震定位系统能有效运行的一个关键条件,设计了4种拾震器阵列布设方案,使煤矿中微震定位监测系统运行得更加科学有效.首先建立复杂地质模型,利用微变网格射线追踪正演模拟出微震源起震到拾震器阵列接收信号的过程,然后在施加随机扰动的情况下,利用粒子群-神经网络算法(PSO-BP)反演推算出震源位置,最后通过震源位置的误差来分析各个布阵方案的特点,同时分析了阵列中拾震器数量的合理值.研究结果表明,在微震监测系统中拾震器利用率最高的情况下,可以给出准确、合理、有效的拾震器布阵方案. 相似文献
993.
针对LLC负载1 MHz超高频感应加热电压型谐振逆变器并联运行中,串联不同电感时逆变器的工作特性进行了理论分析,探究逆变器换流角度以及LLC品质因数的变化,对逆变器输出电压存在差异时换流角度的变化进行了研究。得出1 MHz的电压型谐振逆变器在存在电感差异、电压差异时换流角度是较小的,可以保证逆变器工作在小感性换流状态。最后通过MATLAB/Simulink仿真实验验证了理论分析的正确性,并对仿真结果进行了综合分析。 相似文献
994.
Dawei Song Yanjie Shi Peng Zhang Qiang Huang Udo Kruschwitz Yuexian Hou Bo Wang 《Computational Intelligence》2015,31(4):699-720
Query language modeling based on relevance feedback has been widely applied to improve the effectiveness of information retrieval. However, intra‐query term dependencies (i.e., the dependencies between different query terms and term combinations) have not yet been sufficiently addressed in the existing approaches. This article aims to investigate this issue within a comprehensive framework, namely the Aspect Query Language Model (AM). We propose to extend the AM with a hidden Markov model (HMM) structure to incorporate the intra‐query term dependencies and learn the structure of a novel aspect HMM (AHMM) for query language modeling. In the proposed AHMM, the combinations of query terms are viewed as latent variables representing query aspects. They further form an ergodic HMM, where the dependencies between latent variables (nodes) are modeled as the transitional probabilities. The segmented chunks from the feedback documents are considered as observables of the HMM. Then the AHMM structure is optimized by the HMM, which can estimate the prior of the latent variables and the probability distribution of the observed chunks. Our extensive experiments on three large‐scale text retrieval conference (TREC) collections have shown that our method not only significantly outperforms a number of strong baselines in terms of both effectiveness and robustness but also achieves better results than the AM and another state‐of‐the‐art approach, namely the latent concept expansion model. © 2014 Wiley Periodicals, Inc. 相似文献
995.
996.
997.
998.
Inertial sensors such as gyroscopes and accelerometers are normally considered as the most important sensors in a navigation system. Especially in the underwater or under-ice applications, the accuracy of the entire navigation system has to mainly rely on the precision of the inertial sensors due to inapplicability of global positioning systems. For MEMS-based inertial sensors, fabrication variation and environmental disturbance are among the major error sources. To address these challenges, in this paper we propose an optimization methodology by using parametric analysis on a reference design for improving sensor reliability and resolution. Apart from studying the resolution improvement by deploying an alternative sensing scheme, the effects of changing location, shape, and size of critical cantilevers have been thoroughly explored. By using this method, we have derived an improved mechanical structure for tuning-fork gyroscopes. Our numerical analyses show that the bandwidth of the proposed structure, which is the most important stability measure in the vibratory gyroscopes with slightly mismatched resonant frequencies, is over 1.7 times more immune to fabrication imperfection than the other structural alternatives. The drive and sense resonant amplitude robustness against fabrication imperfection is also improved in the proposed structure. In addition, this structure is able to provide at least 2.3 times larger sense-mode capacitance response to external rotation compared to the previously published designs. More important, it is observed that there is always non-negligible room for improving performance of gyroscopes if our proposed structural optimization methodology is integrated into the conventional MEMS-based inertial sensor design flow. 相似文献
999.
The generation of creative solutions involves nonlinear dynamic procedures that can only be achieved through the creativity of individual team members. Thus, it is important to understand how the formation of individual‐level creativity factors influence the creative solution formation process. The creative solution formation process can be divided into four phases: idea generation, idea screening, idea development and solution verification. Prior research suggests that the creative process may be affected by motivation (intrinsic and extrinsic), knowledge stock (explicit and tacit), individual creativity (intelligence and divergent thinking), and pressure (challenge and time). We tested the effects of these eight factors on performance in the idea generation and idea development phases by conducting an experiment. Our results indicate that intrinsic motivation, intelligence and divergent thinking have a significant positive effect on both idea generation and idea development. Tacit knowledge and challenge pressure have a significant positive effect on idea generation. Time pressure has a significant negative effect on idea development. We also show that both idea generation and idea development have a significant impact on the quality of the final creative solution. 相似文献
1000.
Industrial Designers: Are You Ready for Foreign Markets? Assessing Designer Confidence and Prediction Accuracy in a Transnational Marketing Context 下载免费PDF全文
Dan Zhang 《Creativity & Innovation Management》2015,24(3):449-463
In order to boost sales in foreign markets and compete with emerging local competitors, global companies from developed countries are realizing that they need to develop products specifically for the local markets. Meanwhile, companies in developing nations are building up their design staff and seeking to establish their own global brands. This recent growth in design activity targeting overseas markets suggests the need for academic research to better understand the phenomenon of design expertise transfer across national borders. The present research explores industrial designers' expertise transfer across cultures with respect to knowledge calibration. Based on the literature on expertise and Shanteau's theory of expert competence, several hypotheses are developed regarding the main effect of culture, and the interaction between culture and expertise level, on design confidence and prediction accuracy. A three‐phase experimental study is conducted to test the hypotheses. Results suggest that both expert designers and non‐expert designers are poorly calibrated and overconfident. Nonetheless, expert designers are better calibrated when designing products for a foreign market than for their home market. Theoretical and managerial implications are discussed. 相似文献