全文获取类型
收费全文 | 5535篇 |
免费 | 106篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 279篇 |
综合类 | 7篇 |
化学工业 | 1094篇 |
金属工艺 | 161篇 |
机械仪表 | 105篇 |
建筑科学 | 76篇 |
矿业工程 | 2篇 |
能源动力 | 134篇 |
轻工业 | 324篇 |
水利工程 | 9篇 |
石油天然气 | 18篇 |
无线电 | 570篇 |
一般工业技术 | 1067篇 |
冶金工业 | 1296篇 |
原子能技术 | 174篇 |
自动化技术 | 345篇 |
出版年
2023年 | 25篇 |
2022年 | 60篇 |
2021年 | 117篇 |
2020年 | 48篇 |
2019年 | 66篇 |
2018年 | 70篇 |
2017年 | 69篇 |
2016年 | 91篇 |
2015年 | 72篇 |
2014年 | 91篇 |
2013年 | 209篇 |
2012年 | 188篇 |
2011年 | 258篇 |
2010年 | 175篇 |
2009年 | 174篇 |
2008年 | 186篇 |
2007年 | 197篇 |
2006年 | 172篇 |
2005年 | 166篇 |
2004年 | 143篇 |
2003年 | 150篇 |
2002年 | 112篇 |
2001年 | 111篇 |
2000年 | 105篇 |
1999年 | 136篇 |
1998年 | 540篇 |
1997年 | 295篇 |
1996年 | 221篇 |
1995年 | 165篇 |
1994年 | 131篇 |
1993年 | 120篇 |
1992年 | 78篇 |
1991年 | 81篇 |
1990年 | 62篇 |
1989年 | 69篇 |
1988年 | 50篇 |
1987年 | 56篇 |
1986年 | 62篇 |
1985年 | 60篇 |
1984年 | 54篇 |
1983年 | 37篇 |
1982年 | 42篇 |
1981年 | 46篇 |
1980年 | 44篇 |
1979年 | 31篇 |
1978年 | 31篇 |
1977年 | 31篇 |
1976年 | 75篇 |
1975年 | 18篇 |
1973年 | 15篇 |
排序方式: 共有5661条查询结果,搜索用时 15 毫秒
11.
12.
AIM: To introduce the "starlight" test which was devised to check binocular vision in normal conditions of seeing in a rapid, easy, and cost effective manner and to estimate the possibility of its clinical use in screening the binocular visual field of patients. METHOD: The Bagolini striated glass test consists of optically plano lenses with imperceptible parallel scratches that barely blur the environment but produce two perpendicular luminous stripes (right eye stripe of 45 degrees and left eye stripe of 135 degrees) when subjects with normal binocular vision view one light source. Unlike the original Bagolini test, the starlight test uses three light sources in horizontal or vertical lines according to the testing purposes and the subject is asked to fixate upon the centre light. Through Bagolini glasses, the subject observes the resulting grid-like pattern and the state of binocular visual field of the subject can be roughly estimated. RESULTS: Normal subjects and patients with strabismus, visual field loss from intracranial diseases, glaucoma, retinitis pigmentosa, and functional visual loss were examined using the starlight test and findings from each case were discussed. CONCLUSIONS: The starlight test, which was made by hand at a low cost, is a simple test that can be used clinically. It provides information about the state of binocular vision of patients in normal conditions of seeing. It is also useful because it enables the examiner to share similar experiences with the examinee. The results suggest it can be effective in visual field screening. 相似文献
13.
In an earlier study, an in vitro evolution procedure was applied to a large population of variants of the Tetrahymena group I ribozyme to obtain individuals with a 10(5)-fold improved ability to cleave a target single-stranded DNA substrate under simulated physiological conditions. The evolved ribozymes also showed a twofold improvement, compared to the wild-type, in their ability to cleave a single-stranded RNA substrate. Here, we report continuation of the in vitro evolution process using a new selection strategy to achieve both enhanced DNA and diminished RNA-cleavage activity. Our strategy combines a positive selection for DNA cleavage with a negative selection against RNA binding. After 36 "generations" of in vitro evolution, the evolved population showed an approximately 100-fold increase in the ratio of DNA to RNA-cleavage activity. Site-directed mutagenesis experiments confirmed the selective advantage of two covarying mutations within the catalytic core of the ribozyme that are largely responsible for this modified behavior. The population of ribozymes has now undergone a total of 63 successive generations of evolution, resulting in an average of 28 mutations relative to the wild-type that are responsible for the altered phenotype. 相似文献
14.
Jian Chen Sato Y. Tamura S. 《IEEE transactions on pattern analysis and machine intelligence》2000,22(5):417-429
The goal of this paper is to present an appropriate method for the segmentation of lines at intersections (X-junctions) and branches (T-junctions), which can be regarded as local regions where lines occur at multiple orientations. A novel representation called “orientation space” is proposed, which is derived by adding the orientation axis to the abscissa and the ordinate of the image. The orientation space representation is constructed by treating the orientation parameter, to which Gabor filters can be tuned, as a continuous variable. The problem of segmenting lines at multiple orientations is dealt with by thresholding 3D images in the orientation space and then detecting the connected components therein. In this way, X-junctions and T-junctions can be separated effectively. Curve grouping can also be accomplished. The segmentation of mathematically modeled X-, T-, and L-junctions is demonstrated and analyzed. The sensitivity limits of the method are also discussed. Experimental results using both synthesized and real images show the method to be effective for junction segmentation and curve grouping 相似文献
15.
Nishino K. Sato Y. Ikeuchi K. 《IEEE transactions on pattern analysis and machine intelligence》2001,23(11):1257-1265
Image-based and model-based methods are two representative rendering methods for generating virtual images of objects from their real images. However, both methods still have several drawbacks when we attempt to apply them to mixed reality where we integrate virtual images with real background images. To overcome these difficulties, we propose a new method, which we refer to as the Eigen-Texture method. The proposed method samples appearances of a real object under various illumination and viewing conditions, and compresses them in the 2D coordinate system defined on the 3D model surface generated from a sequence of range images. The Eigen-Texture method is an example of a view-dependent texturing approach which combines the advantages of image-based and model-based approaches. No reflectance analysis of the object surface is needed, while an accurate 3D geometric model facilitates integration with other scenes. The paper describes the method and reports on its implementation 相似文献
16.
Kenzo Sato 《Journal of Infrared, Millimeter and Terahertz Waves》1984,5(9):1269-1288
To promote the efficiency of the effect of remote-resonance which is induceable in the anomalous dispersion region of the resonator surface in the I.R. region, we have investigated three subjects; One is usage of the multi-piled oscillators made of silica-Si layers. Second is the soft-Zeeman effect (at 0–15 Gauss) which was induced in the system of remote-resonance which consists of the oscillator and the resonator they were situated perpendicularly with some distance in the atomospheric air. Third is usage of the I.R. radiation emitted from the surface of hand and the radiation modulated by some textiles as oscillators. The efficiency of this system was shown as ΔRi (Ei) α α (Ei), β (Ei). γ (Ei), (emission efficiency x transferring efficiency x resonance efficiency) and ΔRi (Ei) was shown as (No (Ei)±ΔNi (Ei))x fα{Ro (Ei)±ΔRi (Ei)} at the spin sensitive region of the resonator surface in the Nf-R relation. Also, we discussed the stress-optical effect, the soft-Zeeman effect and some physiological problems induced in this system based on the statistical spin-quantum mechanics considering the predissociation and dissociation process of the shallow electrons in Si (100) face and CO 2 * excimers and the CO2 molecules in the air. 相似文献
17.
18.
19.
20.
Increase in the amount of erythrocyte delta-aminolevulinic acid dehydratase in workers with moderate lead exposure 总被引:2,自引:0,他引:2
This report summarizes our current understanding of the heavy chain haplotypes found in our laboratories' rabbits. Independently derived data from several laboratories have been synthesizes into a consistent picture of the linked inheritance of allotypic markers found on the different heavy chain classes and subclasses of rabbit immunoglobulins in pedigreed rabbits, including the families of three apparent VH-CH recombinants. In one recombinant, the entire group of CH markers (C mu, C gamma, and C alpha) recombined with the set of VH. Although in the other two recombinants all CH markers may also have recombined as a group, in one of these only IgG and IgA CH genes were informative; in the other recombinant, only the IgG allotypes were informative. Some allotypic determinants found on IgM molecules ("conformational") appear only when a specific variable region allotype (VHa) is combined with a specific mu constant region allotype (C mu). New combinations of VHa and C mu allotypes were generated in two of the genetic recombinants and led to new "conformational" determinants. The gains and losses observed lend support to the hypothesis that the determinants result from conformations generated by the combination of allotype-specific VH and C mu protein sequences. Conceivably, DNA events that join VH to diversity (D)- and joining (J)-coding sequences or mRNA processing events that splice J to C mu could be involved in generating the sequences that form allotype-specific determinants. 相似文献