全文获取类型
收费全文 | 11821篇 |
免费 | 1540篇 |
国内免费 | 985篇 |
专业分类
电工技术 | 1291篇 |
综合类 | 1036篇 |
化学工业 | 612篇 |
金属工艺 | 233篇 |
机械仪表 | 1010篇 |
建筑科学 | 687篇 |
矿业工程 | 516篇 |
能源动力 | 222篇 |
轻工业 | 435篇 |
水利工程 | 275篇 |
石油天然气 | 234篇 |
武器工业 | 164篇 |
无线电 | 1860篇 |
一般工业技术 | 1398篇 |
冶金工业 | 309篇 |
原子能技术 | 196篇 |
自动化技术 | 3868篇 |
出版年
2024年 | 49篇 |
2023年 | 163篇 |
2022年 | 260篇 |
2021年 | 340篇 |
2020年 | 368篇 |
2019年 | 335篇 |
2018年 | 319篇 |
2017年 | 415篇 |
2016年 | 523篇 |
2015年 | 552篇 |
2014年 | 740篇 |
2013年 | 841篇 |
2012年 | 959篇 |
2011年 | 934篇 |
2010年 | 722篇 |
2009年 | 759篇 |
2008年 | 743篇 |
2007年 | 882篇 |
2006年 | 737篇 |
2005年 | 639篇 |
2004年 | 531篇 |
2003年 | 443篇 |
2002年 | 370篇 |
2001年 | 304篇 |
2000年 | 250篇 |
1999年 | 207篇 |
1998年 | 163篇 |
1997年 | 144篇 |
1996年 | 121篇 |
1995年 | 110篇 |
1994年 | 68篇 |
1993年 | 68篇 |
1992年 | 57篇 |
1991年 | 39篇 |
1990年 | 38篇 |
1989年 | 27篇 |
1988年 | 27篇 |
1987年 | 11篇 |
1986年 | 18篇 |
1985年 | 12篇 |
1984年 | 9篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 8篇 |
1979年 | 3篇 |
1976年 | 3篇 |
1959年 | 5篇 |
1958年 | 2篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
The penalized calibration technique in survey sampling combines usual calibration and soft calibration by introducing a penalty term. Certain relevant estimates in survey sampling can be considered as penalized calibration estimates obtained as particular cases from an optimization problem with a common basic structure. In this framework, a case deletion diagnostic is proposed for a class of penalized calibration estimators including both design-based and model-based estimators. The diagnostic compares finite population parameter estimates and can be calculated from quantities related to the full data set. The resulting diagnostic is a function of the residual and leverage, as other diagnostics in regression models, and of the calibration weight, a singular feature in survey sampling. Moreover, a particular case, which includes the basic unit level model for small area estimation, is considered. Both a real and an artificial example are included to illustrate the diagnostic proposed. The results obtained clearly show that the proposed diagnostic depends on the calibration and soft-calibration variables, on the penalization term, as well as on the parameter to estimate. 相似文献
2.
在分析单一MU(Most Uncertainty)采样缺陷的基础上,提出一种"全局最优搜寻"方法 GOS(Global Optimal Search),并结合MU共同完成查询选择。GOS+MU方法中,GOS着眼全局寻找目标,在应用环境能提供的训练样本数量有限、分类器受训不充分时,该方法选择的对象学习价值高,能快速推进分类器学习进程;MU则能够在GOS采样失效情形下,利用分类器当前训练成果,选择查询不确定性最强的样本补充训练集。通过对网络商品的用户评论进行分类仿真,并比较其他采样学习方法的效果,证明了GOS+MU方法在压缩学习成本、提高训练效率方面的有效性。 相似文献
3.
《Food Control》2015
Listeria contamination in processing plant environments is a major issue for the seafood industry worldwide; faster and more reliable results are therefore desired for early detection and monitoring of environmental Listeria spp. This study aimed to gain a better understanding of the prevalence and diversity of Listeria spp., and to evaluate a rapid detection method, the 3M Molecular Detection Assay (MDA) Listeria, for its ability to detect Listeria spp. in environmental samples from seafood processing plants. Duplicate environmental sponge samples (n = 444) were collected from 152 different sites within three seafood processing plants, and analyzed for Listeria spp. by the MDA method (after 26 and 48 h of enrichment) and the U.S. Food and Drug Administration Bacteriological Analytical Manual method. Overall, detection of Listeria spp. by the two methods did not differ significantly (p > 0.05); 11 (4.9%) and 13 (5.9%) samples were positive for Listeria spp. by the MDA and FDA-BAM method, respectively. The sensitivity of the MDS was 87.0% (95% CI: 77.4–96.6%), specificity was 97.6% (95% CI: 95.5–99.7%), accuracy was 95.3%, and the positive predictive value was 89.4% (95% CI: 80.5–98.2%). Classification of 19 Listeria isolates by partial SigB sequencing analysis identified three allelic types. Twelve of these isolates were ATs 58 and 60 which were classified as Listeria monocytogenes lineage I and serotypes 1/2b, 3b, 4b, 4d, 4e, by multiplex-PCR serotyping. Six Listeria isolates were classified as Listeria innocua (AT31). Our data show that the 3M Molecular Detection Assay Listeria provides rapid and reliable results for detection and monitoring of Listeria spp., which are important for seafood processing plants. Effective Listeria monitoring programs will allow for improved development of Listeria control measures in order to minimize cross-contamination in finished products. 相似文献
4.
马钢二烧结配料计算机控制系统 总被引:1,自引:0,他引:1
阐明了马钢二烧结配科计算机控制系统的目的、控制形式、控制原理;根据烧结配料控制对象的特点对信号采样和控制算法进行了探讨;提供了系统的主要硬件结构,软件功能和程序框图。 相似文献
5.
A cell vertex finite volume method for the solution of steady compressible turbulent flow problems on unstructured hybrid
meshes of tetrahedra, prisms, pyramids and hexahedra is described. These hybrid meshes are constructed by firstly discretising
the computational domain using tetrahedral elements and then by merging certain tetrahedra. A one equation turbulence model
is employed and the solution of the steady flow equations is obtained by explicit relaxation. The solution process is accelerated
by the addition of a multigrid method, in which the coarse meshes are generated by agglomeration, and by parallelisation.
The approach is shown to be effective for the simulation of a number of 3D flows of current practical interest.
Sponsored by The Research Council of Norway, project number 125676/410
Dedicated to the memory of Prof. Mike Crisfield, a respected colleague 相似文献
6.
7.
在数据采集中采用带通采样,可大大降低采样率,但系统中的抗混叠滤波器会造成相位的非线性。采用对滤波后的信号进行带通采样,然后再用FRR滤波器校正相位的非线性,从而不失真地还原原信号,最后在Matlab中进行仿真,验证了该方法的有效性。 相似文献
8.
9.
Lie‐Fern Hsu 《Quality and Reliability Engineering International》2007,23(2):269-272
He and Grigoryan (Quality and Reliability Engineering International 2002; 18 :343–355) formulated the design of a double‐sampling (DS) s control chart as an optimization problem and solved it with a genetic algorithm. They concluded that the DS s control charts can be a more economically preferable alternative in detecting small shifts than traditional s control charts. We explain that, since they only considered the average sample size when the process is in control, their conclusion is questionable. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
10.
We describe a Gauss–Seidel algorithm for optimizing a three‐dimensional unstructured grid so as to conform to a given metric. The objective function for the optimization process is based on the maximum value of an elemental residual measuring the distance of any simplex in the grid to the local target metric. We analyse different possible choices for the objective function, and we highlight their relative merits and deficiencies. Alternative strategies for conducting the optimization are compared and contrasted in terms of resulting grid quality and computational costs. Numerical simulations are used for demonstrating the features of the proposed methodology, and for studying some of its characteristics. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献