全文获取类型
收费全文 | 9193篇 |
免费 | 933篇 |
国内免费 | 416篇 |
专业分类
电工技术 | 568篇 |
技术理论 | 3篇 |
综合类 | 630篇 |
化学工业 | 1649篇 |
金属工艺 | 550篇 |
机械仪表 | 586篇 |
建筑科学 | 666篇 |
矿业工程 | 269篇 |
能源动力 | 341篇 |
轻工业 | 820篇 |
水利工程 | 218篇 |
石油天然气 | 478篇 |
武器工业 | 107篇 |
无线电 | 1006篇 |
一般工业技术 | 1065篇 |
冶金工业 | 353篇 |
原子能技术 | 85篇 |
自动化技术 | 1148篇 |
出版年
2024年 | 17篇 |
2023年 | 207篇 |
2022年 | 304篇 |
2021年 | 501篇 |
2020年 | 367篇 |
2019年 | 307篇 |
2018年 | 347篇 |
2017年 | 363篇 |
2016年 | 330篇 |
2015年 | 471篇 |
2014年 | 597篇 |
2013年 | 638篇 |
2012年 | 603篇 |
2011年 | 775篇 |
2010年 | 611篇 |
2009年 | 524篇 |
2008年 | 472篇 |
2007年 | 407篇 |
2006年 | 441篇 |
2005年 | 290篇 |
2004年 | 250篇 |
2003年 | 193篇 |
2002年 | 207篇 |
2001年 | 167篇 |
2000年 | 199篇 |
1999年 | 193篇 |
1998年 | 133篇 |
1997年 | 104篇 |
1996年 | 100篇 |
1995年 | 90篇 |
1994年 | 83篇 |
1993年 | 66篇 |
1992年 | 60篇 |
1991年 | 30篇 |
1990年 | 22篇 |
1989年 | 25篇 |
1988年 | 18篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 3篇 |
1984年 | 9篇 |
1982年 | 5篇 |
1979年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 644 毫秒
101.
102.
Yangyang Li Xia Xu Peidao Li Licheng Jiao 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2014,18(7):1383-1397
In this paper, local learning is proposed to improve the speed and the accuracy of convergence performance of regularity model-based multiobjective estimation of distribution algorithm (RM-MEDA), a typical multi-objective optimization algorithm via estimation of distribution. RM-MEDA employs a model-based method to generate new solutions, however, this method is easy to generate poor solutions when the population has no obvious regularity. To overcome this drawback, our proposed method add a new solution generation strategy, local learning, to the original RM-MEDA. Local learning produces solutions by sampling some solutions from the neighborhood of elitist solutions in the parent population. As it is easy to search some promising solutions in the neighborhood of an elitist solution, local learning can get some useful solutions which help the population attain a fast and accurate convergence. The experimental results on a set of test instances with variable linkages show that the implement of local learning can accelerate convergence speed and add a more accurate convergence to the Pareto optimal. 相似文献
103.
Ronghua Shang Licheng Jiao Yujing Ren Lin Li Luping Wang 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2014,18(4):743-756
The existing algorithms to solve dynamic multiobjective optimization (DMO) problems generally have difficulties in non-uniformity, local optimality and non-convergence. Based on artificial immune system, quantum evolutionary computing and the strategy of co-evolution, a quantum immune clonal coevolutionary algorithm (QICCA) is proposed to solve DMO problems. The algorithm adopts entire cloning and evolves the theory of quantum to design a quantum updating operation, which improves the searching ability of the algorithm. Moreover, coevolutionary strategy is incorporated in global operation and coevolutionary competitive operation and coevolutionary cooperative operation are designed to improve the uniformity, the diversity and the convergence performance of the solutions. The results on test problems and performance metrics compared with ICADMO and DBM suggest that QICCA has obvious effectiveness and advantages which shows great capability of evolving convergent, diverse and uniformly distributed Pareto fronts. 相似文献
104.
105.
In this paper, a new evolutionary algorithm, called immune clonal coevolutionary algorithm (ICCoA) for dynamic multiobjective optimization (DMO) is proposed. On the basis of the basic principles of artificial immune system, the proposed algorithm adopts the immune clonal selection to solve DMO problems. In addition, the theory of coevolution is incorporated in ICCoA in global operation to preserve the diversity of Pareto-fronts. Moreover, coevolutionary competitive and cooperative operation is designed to enhance the uniformity and the diversity of the solutions. In comparison with NSGA-II, immune clonal algorithm for DMO and direction-based method, the simulation results obtained on 5 difficult test problems and on related performance metrics suggest that ICCoA can achieve better distributed solutions and be very effective in maintaining the uniformity of Pareto-fronts. 相似文献
106.
水热法制备ZrO_2纳米微晶及对乙醇和丁烷气敏性研究 总被引:6,自引:0,他引:6
用水热法制备 Zr O2 纳米微晶的平均尺寸为直径 5 nm,长 7.5 nm。由 X射线衍射确认晶相为单斜相。并对其形状和大小进行了透射电镜和激光散射分析 ,结果表明 Zr O2 纳米粒子在水溶液中存在软团聚 ,团聚体平均尺寸约 90 nm。着重研究了 Zr O2 纳米微晶对乙醇及丁烷的气敏性能 ,结果表明用纳米级 Zr O2 粒子制备的气敏元件对乙醇和丁烷有好的气敏性。并且随着纳米粒子尺寸降低 ,对气体敏感性增强 相似文献
107.
聚羟基脂肪酸酯的合成和应用研究进展 总被引:2,自引:0,他引:2
介绍了聚羟基脂肪酸酯(PHA)的合成方法,重点讨论了微生物合成法、碳源、化学合成、分离方法及降低PHA生产成本的方法,介绍了PHA的性能及其改性研究,论述了PHA在生物医学、农业、电子、食品包装等领域的应用。 相似文献
108.
We report the graft copolymerization of acrylic acid onto the polypropylene (PP) melt‐blown nonwovens induced by electron beam (EB) preirradiation in this article. The occurrence of the graft copolymerization was confirmed by means of XPS, FTIR, and SEM. The effects of preirradiation dose, monomer concentration, bath ratio, reaction time, and temperature on the graft ratio were investigated. The water conservation, water absorption rate, and K+ exchange capacity were also determined on the grafted PP melt‐blown nonwovens, which showed that EB preirradiation‐induced grafting was an effective way to improve the hydrophicility of PP melt‐blown nonwovens. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4971–4977, 2006 相似文献
109.
以CO2-NaOH为介质,研究了填料结构、超重力因子、液体流量和气体流量等对两种多孔板错流旋转床有效比表面积的影响规律.结果表明,不锈钢多孔波纹板的有效比表面积大于聚丙烯多孔板,不锈钢多孔波纹板填料利用周期性变化的波纹表面不仅可以有效利用填料自身的比表面积,而且可起到良好的雾化扩展比表面积的作用,使有效比表面积增大至2.66倍.对实验数据进行回归得出了两种填料结构有效比表面积的关联式,根据关联式计算的有效比表面值与实验值吻合较好. 相似文献
110.
首先推导了粗糙洋面双向偏振反射模型pBRDF(Bidirectional Polarized Reflectance Distribution Function),并将其与SOSVRT(Successive Order of Scattering Radiative Transfer)矢量辐射传输模式耦合,建立了海洋-大气耦合的矢量辐射传输模式,并对该耦合模式的模拟结果与前人模拟结果进行对比,验证了该耦合模式的可靠性与有效性。不同大气和洋面状态、不同高度的主平面内辐射强度和偏振度的模拟结果表明:pBRDF模型可以很好地模拟不同风速下洋面的偏振反射分布特征;洋面在特定角度具有很高的偏振度,并对大气顶的偏振辐射有很大影响。因此,该耦合模式可以更准确地处理辐射光谱在海洋-大气两种介质间的传输问题,对矢量辐射传输、大气遥感问题的研究有重要意义。 相似文献