全文获取类型
收费全文 | 10446篇 |
免费 | 845篇 |
国内免费 | 389篇 |
专业分类
电工技术 | 474篇 |
技术理论 | 2篇 |
综合类 | 694篇 |
化学工业 | 1945篇 |
金属工艺 | 621篇 |
机械仪表 | 656篇 |
建筑科学 | 881篇 |
矿业工程 | 306篇 |
能源动力 | 217篇 |
轻工业 | 774篇 |
水利工程 | 201篇 |
石油天然气 | 766篇 |
武器工业 | 85篇 |
无线电 | 1009篇 |
一般工业技术 | 1179篇 |
冶金工业 | 424篇 |
原子能技术 | 155篇 |
自动化技术 | 1291篇 |
出版年
2024年 | 27篇 |
2023年 | 141篇 |
2022年 | 267篇 |
2021年 | 458篇 |
2020年 | 367篇 |
2019年 | 290篇 |
2018年 | 344篇 |
2017年 | 394篇 |
2016年 | 325篇 |
2015年 | 435篇 |
2014年 | 504篇 |
2013年 | 689篇 |
2012年 | 760篇 |
2011年 | 762篇 |
2010年 | 696篇 |
2009年 | 578篇 |
2008年 | 569篇 |
2007年 | 534篇 |
2006年 | 589篇 |
2005年 | 465篇 |
2004年 | 323篇 |
2003年 | 266篇 |
2002年 | 226篇 |
2001年 | 196篇 |
2000年 | 199篇 |
1999年 | 251篇 |
1998年 | 207篇 |
1997年 | 186篇 |
1996年 | 149篇 |
1995年 | 121篇 |
1994年 | 81篇 |
1993年 | 67篇 |
1992年 | 56篇 |
1991年 | 35篇 |
1990年 | 31篇 |
1989年 | 26篇 |
1988年 | 17篇 |
1987年 | 7篇 |
1986年 | 12篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1971年 | 2篇 |
1959年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 375 毫秒
91.
针对传统布谷鸟搜索算法(cuckoo search,CS)对复杂问题收敛精度低、迭代步幅局限性大的特点,提出了基于骑手优化的动态布谷鸟搜索策略(rider optimization cuckoo search,ROCS)。结合骑手优化算法(rider optimization algorithm,ROA)思想,利用多种群在单周期内进行多策略寻优,动态使用最优策略进行加强搜索,提高算法对复杂问题的收敛效率;同时对Lévy飞行运动进行动态参数调节,改善算法搜索前期及末期表现。仿真测试结果显示,改进算法对复杂问题的优化表现优于比对算法,算法寻优效率得到显著改善。 相似文献
92.
针对实时监控系统中的运行设备或装置的异常报警信息,设计了基于GSM无线通讯的微机监测系统,实现了多故障远程短信息报警功能,介绍了系统的软硬件设计及主要功能;经应用测试,系统具有宴时性强、稳定性高、投入成本低等特点,能将信息同时发送至多个移动通信终端,已成功应用于农业温室大棚监控系统的实时故障报警,系统也可方便地应用于工厂生产线、金融、交通及家庭安全等方面的远程监测. 相似文献
93.
This paper studies optimal path problems integrated with the concept of second order stochastic dominance. These problems arise from applications where travelers are concerned with the trade off between the risks associated with random travel time and other travel costs. Risk-averse behavior is embedded by requiring the random travel times on the optimal paths to stochastically dominate that on a benchmark path in the second order. A general linear operating cost is introduced to combine link- and path-based costs. The latter, which is the focus of the paper, is employed to address schedule costs pertinent to late and early arrival. An equivalent integer program to the problem is constructed by transforming the stochastic dominance constraint into a finite number of linear constraints. The problem is solved using both off-the-shelf solvers and specialized algorithms based on dynamic programming (DP). Although neither approach ensures satisfactory performance for general large-scale problems, the numerical experiments indicate that the DP-based approach provides a computationally feasible option to solve medium-size instances (networks with several thousand links) when correlations among random link travel times can be ignored. 相似文献
94.
Liang Gao Mi Xiao Xinyu Shao Ping Jiang Li Nie Haobo Qiu 《Structural and Multidisciplinary Optimization》2012,46(3):399-413
To reduce the computational cost of implementing computer-based simulations and analyses in engineering design, a variety of metamodeling techniques have been developed and used for the construction of metamodels. Metamodels, also called approximation models and surrogate models, can be used to make a replacement of the expensive simulation codes for design and optimization. In this paper, gene expression programming (GEP) algorithm in the evolutionary computing area is investigated as an alternative metamodeling technique to provide the approximation of a design space. The approximation performance of GEP is tested on some low-dimensional mathematical and engineering problems. A comparative study is conducted on GEP and three common metamodeling techniques in engineering design (i.e., response surface methodology (RSM), kriging and radial basis functions (RBF)) for the approximation of the low-dimensional design space. Multiple evaluation criteria are considered in the comparison: accuracy, robustness, transparency and efficiency. Two different sample sizes are adopted: small and large. Comparative results indicate that GEP can achieve the most accurate and robust approximation of a low-dimensional design space for small sample sets. For large sample sets, GEP also presents good prediction accuracy and high robustness. Moreover, the transparency of GEP is the best since it can provide clear function relationships and factor contributions by means of compact expressions. As a novel metamodeling technique, GEP shows great promise for metamodeling applications in a low-dimensional design space, especially when only a few sample points are selected and used for training. 相似文献
95.
96.
介绍一种梅山冶金公司板坯连同上应用的新型的结晶器液位控制系统,它由浮式式液位检测装置,RSE1000控制器和电动塞棒执行机构所组成,由法国SERT公司成套制造。 相似文献
97.
Miaomiao Shen Yanshen Nie Yueyue Chen Xiufeng Zhang Jie Zhao 《International journal of molecular sciences》2021,22(1)
Meiotic recombination 11 (Mre11) is a relatively conserved nuclease in various species. Mre11 plays important roles in meiosis and DNA damage repair in yeast, humans and Arabidopsis, but little research has been done on mitotic DNA replication and repair in rice. Here, it was found that Mre11 was an extensively expressed gene among the various tissues and organs of rice, and loss-of-function of Mre11 resulted in severe defects of vegetative and reproductive growth, including dwarf plants, abnormally developed male and female gametes, and completely abortive seeds. The decreased number of cells in the apical meristem and the appearance of chromosomal fragments and bridges during the mitotic cell cycle in rice mre11 mutant roots revealed an essential role of OsMre11. Further research showed that DNA replication was suppressed, and a large number of DNA strand breaks occurred during the mitotic cell cycle of rice mre11 mutants. The expression of OsMre11 was up-regulated with the treatment of hydroxyurea and methyl methanesulfonate. Moreover, OsMre11 could form a complex with OsRad50 and OsNbs1, and they might function together in non-homologous end joining and homologous recombination repair pathways. These results indicated that OsMre11 plays vital roles in DNA replication and damage repair of the mitotic cell cycle, which ensure the development and fertility of rice by maintaining genome stability. 相似文献
98.
ZENG Yong WU Zhengyuan DONG Lihua LIU Zhihong MA Jianfeng LI Zan 《西安电子科技大学学报(自然科学版)》2021,48(3):170-187
The encrypted transmission of network traffic is one of the development trends of the Internet.The identification of malicious traffic in encrypted traffic is an important way to maintain the security of cyberspace.One of the prior tasks of identifying malicious traffic is to classify encrypted traffic into the encrypted/unencrypted,different kinds of the application programs and encryption algorithms in order to improve the efficiency of identification.Then they are transformed into the image,matrix,n-gram or other forms which will be sent into the machine learning training model,so as to realize the binary classification and multi classification of benign malicious traffic.However,the machine learning based way relies seriously on the number and quality of samples,and can not effectively deal with the data after traffic shaping or confusion.Fortunately,cryptography based malicious traffic identification can search malicious keywords over encrypted traffic to avoid such problems,which must integrate searchable encryption technology,deep packet inspection and a provable security model to protect both data and rules.Finally,some unsolved problems of malicious traffic identification technology in encrypted traffic are presented. 相似文献
99.
区块链是随比特币等数字货币兴起的一种全新的去中心化架构, 具有去信任化的特点。在区块链中用假名来提供匿名性, 然而研究表明这种匿名并不安全, 通过交易图谱分析可以发现不同假名间的关联性, 找到同一用户的假名, 破坏匿名性。通过地址的混合可以解决这一问题。本文提出了一种去中心化的混币方法, 通过分析证明, 该方法能有效地保障用户的隐私, 还能实现用户不同金额的混合, 增加便捷性。 相似文献
100.
考虑到在电力市场环境下出现的新市场主体,首先引入配电分配矩阵来模拟市场双边交易行为,在传统负荷频率控制模型的基础上,建立基于配电分配矩阵的负荷频率控制模型.然后针对负荷频率控制模型在区域地理上的分布式特点,采用基于分布式模型预测控制方式进行控制.最后,以一个两区域交直流互联电网负荷频率控制模型为例进行Simulink仿真.结果表明所建立的模型能够有效地模拟市场双边交易过程与C-MPC控制、传统PI控制方式相比,基于分布式模型预测控制方式具有更好的控制性能. 相似文献