全文获取类型
收费全文 | 13417篇 |
免费 | 2233篇 |
国内免费 | 1381篇 |
专业分类
电工技术 | 591篇 |
技术理论 | 2篇 |
综合类 | 802篇 |
化学工业 | 1457篇 |
金属工艺 | 348篇 |
机械仪表 | 1605篇 |
建筑科学 | 370篇 |
矿业工程 | 128篇 |
能源动力 | 160篇 |
轻工业 | 851篇 |
水利工程 | 47篇 |
石油天然气 | 697篇 |
武器工业 | 156篇 |
无线电 | 4050篇 |
一般工业技术 | 2362篇 |
冶金工业 | 300篇 |
原子能技术 | 557篇 |
自动化技术 | 2548篇 |
出版年
2024年 | 113篇 |
2023年 | 407篇 |
2022年 | 616篇 |
2021年 | 724篇 |
2020年 | 724篇 |
2019年 | 578篇 |
2018年 | 600篇 |
2017年 | 665篇 |
2016年 | 720篇 |
2015年 | 733篇 |
2014年 | 952篇 |
2013年 | 861篇 |
2012年 | 1016篇 |
2011年 | 1021篇 |
2010年 | 765篇 |
2009年 | 755篇 |
2008年 | 737篇 |
2007年 | 773篇 |
2006年 | 689篇 |
2005年 | 527篇 |
2004年 | 492篇 |
2003年 | 382篇 |
2002年 | 346篇 |
2001年 | 252篇 |
2000年 | 241篇 |
1999年 | 221篇 |
1998年 | 174篇 |
1997年 | 167篇 |
1996年 | 166篇 |
1995年 | 92篇 |
1994年 | 97篇 |
1993年 | 79篇 |
1992年 | 61篇 |
1991年 | 49篇 |
1990年 | 49篇 |
1989年 | 31篇 |
1988年 | 18篇 |
1987年 | 12篇 |
1986年 | 20篇 |
1985年 | 14篇 |
1984年 | 11篇 |
1983年 | 12篇 |
1981年 | 9篇 |
1980年 | 6篇 |
1964年 | 4篇 |
1962年 | 5篇 |
1961年 | 4篇 |
1959年 | 4篇 |
1956年 | 4篇 |
1955年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Fresh and frozen-thawed (F-T) pork meats were classified by Vis–NIR hyperspectral imaging. Eight optimal wavelengths (624, 673, 460, 588, 583, 448, 552 and 609 nm) were selected by successive projections algorithm (SPA). The first three principal components (PCs) obtained by principal component analysis (PCA) accounted for over 99.98% of variance. Gray-level-gradient co-occurrence matrix (GLGCM) was applied to extract 45 textural features from the PC images. The correct classification rate (CCR) was employed to evaluate the performance of the partial least squares-discriminate analysis (PLS-DA) models, by using (A) the reflected spectra at full wavelengths and (B) those at the optimal wavelengths, (C) the extracted textures based on the PC images, and (D) the fused variables combining spectra at the optimal wavelengths and textures. The results showed that the best CCR of 97.73% was achieved by applying (D), confirming the high potential of textures for fresh and F-T meat discrimination. 相似文献
12.
针对不同地质目标的叠前时间偏移成像解释评价 总被引:3,自引:0,他引:3
随着计算机硬件和地震勘探成像技术的发展,叠前时间偏移正逐步替代常规的NMO加DMO加叠后时间偏移成为地震数据成像处理方法的主流。但对于不同的地质目标,叠前时间偏移的成像效果是否优于常规NMO加DMO加叠后时间偏移的成像效果呢?为此,从地震数据成像处理方法、处理流程和处理参数等方面进行了讨论,并基于某地区三维数据常规处理结果和叠前时间偏移处理结果,针对不同地质目标进行了剖析与评价。认为:叠前时间偏移成像的垂向分辨率较常规处理明显降低,但对于空间波阻抗变化明显的河流和断层,叠前时间偏移成像的空间分辨率要高于常规处理;对于小于1/4波长的叠置薄储层,叠前时间偏移成像的垂向和空间分辨率低于常规处理结果。 相似文献
13.
多臂井径成像测井技术 总被引:2,自引:2,他引:0
多臂井径成像测井技术同以往的40臂、X—Y井径等非成像工程测井相比具有较为明显的优势,不但可以做定量解释提供最大、最小、平均井径值,而且可以提供更为直观的18条或36务独立的测井曲线、磁井径,磁重量、井温、井壁立体图、井壁成像图、井壁截面图,为检测井下套管的完好性及修复提供了更为可靠直观的资料,满足了地质学家及时监测套管状况的要求,也为油井作业、大修提供全面、准确的套管全貌。文章介绍了18臂、36臂两种井径成像测井技术。并通过对测试资料实例的解释、分析、研究,总结了多臂井径成像测井技术的特点及应用效果。 相似文献
14.
15.
介绍了医用红宝石激光器触摸屏控制系统的基本结构,分析了医用红宝石激光器中主要电磁干扰(EMI)的产生机制,提出了具体的电磁兼容(EMC)技术措施并得到实验验证。 相似文献
16.
激光水下成像技术及其进展 总被引:6,自引:0,他引:6
介绍了近年发展起来的三种主要的激光水下成像方法,即常规水下激光成像、高分辨率水下激光三维成像和偏振激光成像,分析了它们各自的工作原理、特点以及各自的发展状况。 相似文献
17.
To determine three‐dimensional fiber orientation states in injection‐molded short‐fiber composites, a confocal laser scanning microscope (CLSM) is used. Since the CLSM optically sections the specimen, more than two images of the cross sections on and below the surface of the composite can be obtained. Three‐dimensional fiber orientation states can be determined by using geometric parameters of fiber images obtained from two parallel cross sections. For experiments, carbon‐fiber‐reinforced polystyrene is examined by the CLSM and geometric parameters of fibers on each cross‐sectional plane are measured by an image analysis. In order to describe fiber orientation states compactly, orientation tensors are determined at different positions of the prepared specimen. Three‐dimensional orientation states are obtained without any difficulty by determining the out‐of‐plane angles utilizing fiber images on two parallel planes acquired by the CLSM. Orientation states are different at different positions and show the shell–core structure along the thickness of the specimen. Fiber orientation tensors are predicted by a numerical analysis and the numerically predicted orientation states show good agreement with measured ones. However, some differences are found at the end of cavity. They may result from the fountain flow effects, which are not considered in the numerical analysis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 500–509, 2003 相似文献
18.
19.
Gregory S. Zaric Jeffrey S. Hoch 《International Transactions in Operational Research》2006,13(6):493-513
Interest in medical savings accounts (MSAs) as a potential tool to reduce healthcare costs has been widespread. A small number of countries have either implemented or run pilot programs of MSAs, and vigorous policy debates have taken place in several other countries about the potential merits of introducing MSAs as a method of paying for health care. In this paper we develop a model to assess the cost saving potential of MSAs in a publicly funded healthcare system. We assume that the public healthcare payer may choose between reimbursing healthcare expenditures through an MSA or through a form of third‐party payer insurance. We use the model to identify the conditions under which MSAs may reduce costs. We illustrate using data on healthcare expenditures from Canada. 相似文献
20.
Using Web resources to construct multilingual medical thesaurus for cross-language medical information retrieval 总被引:1,自引:0,他引:1
Due to the language barrier, non-English users are unable to retrieve the most updated medical information from the U.S. authoritative medical websites, such as PubMed and MedlinePlus. However, currently, there is no any cross-language medical information retrieval (CLMIR) system that can help Chinese-speaking consumers cross the language barrier in finding useful English medical information. A few CLMIR systems utilize MeSH (Medical Subject Headings) to help overcome the language barrier. Unfortunately, the traditional Chinese version of MeSH is currently unavailable.In this paper, we employ a semi-automatic term translation method to construct a Chinese–English MeSH by exploiting abundant multilingual Web resources, including Web anchor texts and search–result pages. Through this method, we have developed a Chinese–English Mesh Compilation System to assist knowledge engineers in compiling a Chinese–English medical thesaurus with more than 19,000 entries. Furthermore, this thesaurus has been used to develop a prototypical system for cross-language medical information retrieval, MMODE, which can help consumers retrieve top-quality English medical information using Chinese terms. 相似文献