全文获取类型
收费全文 | 3032篇 |
免费 | 96篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 16篇 |
综合类 | 3篇 |
化学工业 | 386篇 |
金属工艺 | 48篇 |
机械仪表 | 26篇 |
建筑科学 | 53篇 |
矿业工程 | 6篇 |
能源动力 | 68篇 |
轻工业 | 185篇 |
水利工程 | 7篇 |
石油天然气 | 8篇 |
无线电 | 319篇 |
一般工业技术 | 337篇 |
冶金工业 | 1386篇 |
原子能技术 | 13篇 |
自动化技术 | 271篇 |
出版年
2024年 | 5篇 |
2023年 | 36篇 |
2022年 | 54篇 |
2021年 | 99篇 |
2020年 | 71篇 |
2019年 | 86篇 |
2018年 | 76篇 |
2017年 | 76篇 |
2016年 | 111篇 |
2015年 | 56篇 |
2014年 | 82篇 |
2013年 | 113篇 |
2012年 | 97篇 |
2011年 | 105篇 |
2010年 | 88篇 |
2009年 | 72篇 |
2008年 | 78篇 |
2007年 | 53篇 |
2006年 | 40篇 |
2005年 | 44篇 |
2004年 | 28篇 |
2003年 | 29篇 |
2002年 | 33篇 |
2001年 | 27篇 |
2000年 | 29篇 |
1999年 | 50篇 |
1998年 | 446篇 |
1997年 | 264篇 |
1996年 | 132篇 |
1995年 | 98篇 |
1994年 | 65篇 |
1993年 | 88篇 |
1992年 | 27篇 |
1991年 | 19篇 |
1990年 | 27篇 |
1989年 | 20篇 |
1988年 | 15篇 |
1987年 | 17篇 |
1986年 | 22篇 |
1985年 | 13篇 |
1984年 | 5篇 |
1983年 | 12篇 |
1982年 | 18篇 |
1981年 | 11篇 |
1980年 | 16篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1977年 | 36篇 |
1976年 | 117篇 |
1955年 | 2篇 |
排序方式: 共有3132条查询结果,搜索用时 15 毫秒
41.
C Jurinke B Z?llner HH Feucht D van den Boom A Jacob S Polywka R Laufs H K?ster 《Canadian Metallurgical Quarterly》1998,14(3):97-102
DNA preparations from three different groups of serum samples were examined for HBV-DNA via a nested polymerase chain reaction assay (lower detection limit: 10 viral genomes in 100 microliters serum): Group I consisted of 11 uninfected control sera, group II consisted of sera obtained from 11 HBV infected patients and group III consisted of 21 isolated anti-HBc positive samples. The 21 samples from group III were HBV-DNA negative according to a conventional non-nested PCR assay and hybridization with a 32P-labelled probe. Using nested PCR and mass spectrometry, HBV-DNA was detected in none of group I and in all of group II samples. In 11 out of 21 (52%) of the isolated anti-HBc positive sera from group III, HBV-DNA was detected. No correlation was observed between HBV-DNA positivity and anti-HBc titers. Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry provided a fast, sensitive and non-radioactive assay for the detection of PCR products without the need for gel electrophoresis or hybridization with labelled probes. 相似文献
42.
43.
JC Oosterwijk WE Mesker MC Ouwerkerk-Van Velzen CF Knepflé KC Wiesmeijer GC Beverstock GJ Van Ommen HJ Tanke HH Kanhai 《Canadian Metallurgical Quarterly》1998,18(10):1082-1085
In a pilot study to establish fetal nucleated red blood cell (NRBC) detection in maternal blood, trisomy 13 was diagnosed by FISH analysis at 11 weeks' gestation. The NRBCs were detected after a single-step ficoll density gradient enrichment. In blood samples taken both before and after CVS, 52 and 80 NRBCs, respectively, were found to be positive for fetal haemoglobin. In 47 per cent of these cells, FISH analysis for X and Y chromosomes confirmed the fetal sex. Moreover, 48 per cent of these NRBCs showed three fluorescent signals for a chromosome 13 probe, which confirmed the diagnosis of trisomy 13, previously detected at CVS karyotyping. This is the first report of non-invasive prenatal diagnosis of trisomy 13, i.e., pre-CVS, in the first trimester. The high number of fetal NRBCs detected indicates a connection with aneuploidy, probably due to early impairment of the feto-maternal barrier. 相似文献
44.
Chi Nguyen Quynh Ho Minh Thi Tran Chung Chinh Doan Son Nghia Hoang Diem Hong Tran Long Thanh Le 《International journal of molecular sciences》2021,22(9)
Simulated microgravity (SMG) induced the changes in cell proliferation and cytoskeleton organization, which plays an important factor in various cellular processes. The inhibition in cell cycle progression has been considered to be one of the main causes of proliferation inhibition in cells under SMG, but their mechanisms are still not fully understood. This study aimed to evaluate the effects of SMG on the proliferative ability and cytoskeleton changes of Chang Liver Cells (CCL-13). CCL-13 cells were induced SMG by 3D clinostat for 72 h, while the control group were treated in normal gravity at the same time. The results showed that SMG reduced CCL-13 cell proliferation by an increase in the number of CCL-13 cells in G0/G1 phase. This cell cycle phase arrest of CCL-13 cells was due to a downregulation of cell cycle-related proteins, such as cyclin A1 and A2, cyclin D1, and cyclin-dependent kinase 6 (Cdk6). SMG-exposed CCL-13 cells also exhibited a downregulation of α-tubulin 3 and β-actin which induced the cytoskeleton reorganization. These results suggested that the inhibited proliferation of SMG-exposed CCL-13 cells could be associate with the attenuation of major cell cycle regulators and main cytoskeletal proteins. 相似文献
45.
In this Account, we explore the role constant curvature structures play in amphiphilic small molecule crystals and extended coordination solids. A constant curvature structure is one in which there is a surface or interface that has the same curvature throughout its surface. Simple examples of such structures contain spheres (micelles), columns, or layers. Yet another family are cubic as is found in the gyroid topology. For amphiphilic systems, there are two domains, one generally hydrophobic and the other hydrophilic. We find that the interfaces between these two domains in small molecule structures resemble those in larger scale systems and adopt topologies related to constant curvature structures. The hydrophobic-to-total volume ratio, a molecular parameter, can be used to predict which type of constant curvature structure is adopted. In the case of three coordinate extended solids, constant curvature plays a role both in the extended net topology and in the hydrophobic-to-hydrophilic interface. 相似文献
46.
47.
Tuan Anh Tran In Seop Na Soo Hyung Kim 《International Journal on Document Analysis and Recognition》2016,19(3):191-209
Document layout analysis or page segmentation is the task of decomposing document images into many different regions such as texts, images, separators, and tables. It is still a challenging problem due to the variety of document layouts. In this paper, we propose a novel hybrid method, which includes three main stages to deal with this problem. In the first stage, the text and non-text elements are classified by using minimum homogeneity algorithm. This method is the combination of connected component analysis and multilevel homogeneity structure. Then, in the second stage, a new homogeneity structure is combined with an adaptive mathematical morphology in the text document to get a set of text regions. Besides, on the non-text document, further classification of non-text elements is applied to get separator regions, table regions, image regions, etc. The final stage, in refinement region and noise detection process, all regions both in the text document and non-text document are refined to eliminate noises and get the geometric layout of each region. The proposed method has been tested with the dataset of ICDAR2009 page segmentation competition and many other databases with different languages. The results of these tests showed that our proposed method achieves a higher accuracy compared to other methods. This proves the effectiveness and superiority of our method. 相似文献
48.
49.
In this paper, we introduce an internet voting protocol which satisfies desired security requirements of electronic voting. In the newly proposed protocol, we allow the adversaries to get more power than in any previous works. They can be coercers or vote buyers outside, and corrupted parties inside our system. These adversaries also have ability to collude with each other to ruin the whole system. Our main contribution is to design an internet voting protocol which is unsusceptible to most of sophisticated attacks. We employ the blind signature technique and the dynamic ballots instead of complex cryptographic techniques to preserve privacy in electronic voting. Moreover, we also aim at the practical system by improving the blind signature scheme and removing physical assumptions which have often been used in the previous works. 相似文献
50.
Development of a quadruped walking robot AiDIN-III using biologically inspired kinematic analysis 总被引:1,自引:0,他引:1
Ig Mo Koo Duc Trong Tran Yoon Haeng Lee Hyungpil Moon Ja Choon Koo Sangdeok Park Hyouk Ryeol Choi 《International Journal of Control, Automation and Systems》2013,11(6):1276-1289
This paper presents a bio-inspired mechanism design for a quadruped walking robot. The approach is derived from the observation on the behaviors of quadruped locomotion, skeletal structure, and the study on the stability of walking based on morphological analysis. In the first, we define the design parameters such as the dimensions of the body and limbs, the center of mass position, and locomotion mechanisms based on surveys on the literatures from biologists. Then, by using the parameters, we propose an useful framework for determining the design parameters of a quadruped walking robot. For implementations, we manufacture a dog-type self-contained quadruped walking robot, named AiDIN-III (Artificial Digitigrade for Natural Environment version III) and the effectiveness of the proposed idea is validated via experimental works. 相似文献