全文获取类型
收费全文 | 3133篇 |
免费 | 27篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 5篇 |
化学工业 | 165篇 |
金属工艺 | 9篇 |
机械仪表 | 9篇 |
建筑科学 | 32篇 |
能源动力 | 15篇 |
轻工业 | 102篇 |
水利工程 | 9篇 |
石油天然气 | 4篇 |
无线电 | 51篇 |
一般工业技术 | 124篇 |
冶金工业 | 2566篇 |
原子能技术 | 5篇 |
自动化技术 | 66篇 |
出版年
2023年 | 8篇 |
2022年 | 5篇 |
2021年 | 16篇 |
2020年 | 13篇 |
2019年 | 12篇 |
2018年 | 9篇 |
2017年 | 15篇 |
2016年 | 9篇 |
2015年 | 11篇 |
2014年 | 23篇 |
2013年 | 31篇 |
2012年 | 29篇 |
2011年 | 63篇 |
2010年 | 59篇 |
2009年 | 22篇 |
2008年 | 50篇 |
2007年 | 32篇 |
2006年 | 30篇 |
2005年 | 31篇 |
2004年 | 22篇 |
2003年 | 28篇 |
2002年 | 16篇 |
2001年 | 11篇 |
2000年 | 14篇 |
1999年 | 76篇 |
1998年 | 711篇 |
1997年 | 394篇 |
1996年 | 269篇 |
1995年 | 167篇 |
1994年 | 119篇 |
1993年 | 161篇 |
1992年 | 40篇 |
1991年 | 22篇 |
1990年 | 27篇 |
1989年 | 36篇 |
1988年 | 39篇 |
1987年 | 40篇 |
1986年 | 32篇 |
1985年 | 39篇 |
1983年 | 7篇 |
1982年 | 24篇 |
1981年 | 21篇 |
1980年 | 36篇 |
1979年 | 6篇 |
1978年 | 11篇 |
1977年 | 76篇 |
1976年 | 203篇 |
1975年 | 16篇 |
1974年 | 6篇 |
1973年 | 4篇 |
排序方式: 共有3162条查询结果,搜索用时 187 毫秒
21.
22.
RD Wegner I Henrichs H Joenje T Schroeder-Kurth 《Canadian Metallurgical Quarterly》1996,50(6):479-482
The clinical and cytogenetic data of the first patient proven to belong to the fifth Fanconi anemia complementation group are described. The Turkish boy presented with psychomotoric retardation, growth retardation, retarded bone age, brachycephaly, hypotelorism, epicanthus, syndactyly, brachydactyly, renal dystopia, and cryptorchism. In addition, an asymmetrical skeletal anomaly was seen with a double distal phalanx of the left thumb and hypoplasia of the right thumb. Typical hematological features of the disorder developed, at the age of 2.5 years, about 1 year after diagnosis. Cytogenetic studies confirmed the clinical diagnosis and revealed a spontaneous chromosomal instability and hypersensitivity to the cross-linking agents diepoxybutane and Trenimon. The findings in the patient, who is considered to be the standard for the fifth Fanconi anemia complementation group, are compared with data reported for other patients affected with Fanconi anemia. 相似文献
23.
24.
BACKGROUND: Arteriovenous malformations (AVMs) are an abnormal communication between arterial and venous structures. Pelvic AVMs have been infrequently described in the literature and represent an uncommon cause of a palpable pelvic mass. CASE: A case of pelvic AVM with ureteral obstruction occurred. The location and radiologic appearance of the AVM suggested a complex adnexal mass. During exploration and resection of the mass, significant bleeding was encountered. The diagnosis of AVM was made only retrospectively, with histologic examination of the specimen. CONCLUSION: AVMs are an uncommon and unique cause of pelvic pathology. Preoperative diagnosis will alert the surgeon as to the technically difficult resection that may be encountered and to the massive bleeding that can be associated with their removal. 相似文献
25.
RD Mootz 《Canadian Metallurgical Quarterly》1996,19(4):257-264
BACKGROUND: The presence of a genetic factor in the determination of leprosy has long been debated. This study tests whether the HLA-linked control of susceptibility to leprosy and/or for the types of leprosy could be confirmed. MATERIALS AND METHODS: In 15 multicase families, the method of DeVries et al., 1976, was used to detect nonrandom segregation of parental HLA haplotypes in their affected and healthy siblings. Linkage analyses, for two and three alleles were performed by the computer program LIPED: RESULTS: For the affected siblings, the segregations of the parental HLA haplotype were significantly nonrandom from the healthy parents and random from the affected parents, indicating that affected siblings were sharing their HLA haplotypes (segregated from the healthy parents) more than expected. The segregations to the healthy siblings from both the healthy and affected parents were random. Healthy siblings inherited the haplotypes shared among the leprosy siblings randomly as expected. There were excess DR2/DR2 homozygote individuals among tuberculoid siblings. The highest lod score was achieved when we considered our suggested three-alleles model for the susceptibility to the different types of leprosy. CONCLUSIONS: A closely HLA-linked gene on chromosome number 6 with multiple alleles (3 or more) in recombination fraction between 0.05 and 0.1 with 70 to 100% penetrance may be responsible for the susceptibility to the different types of leprosy, whereas the susceptibility to leprosy per se maybe the responsibility of non-HLA linked gene/s. DR2/DR2 homozygote individuals may be relatively at high risk of developing leprosy or tuberculoid leprosy. 相似文献
26.
27.
28.
29.
30.
Knowledge conceptualization tool 总被引:3,自引:0,他引:3
Fujihara H. Simmons D.B. Ellis N.C. Shannon R.E. 《Knowledge and Data Engineering, IEEE Transactions on》1997,9(2):209-220
Knowledge acquisition is one of the most important and problematic aspects of developing knowledge-based systems. Many automated tools have been introduced in the past, however, manual techniques are still heavily used. Interviewing is one of the most commonly used manual techniques for a knowledge acquisition process, and few automated support tools exist to help knowledge engineers enhance their performance. The paper presents a knowledge conceptualization tool (KCT) in which the knowledge engineer can effectively retrieve, structure, and formalize knowledge components, so that the resulting knowledge base is accurate and complete. The KCT uses information retrieval technique to facilitate conceptualization, which is one of the human intensive activities of knowledge acquisition. Two information retrieval techniques employing best-match strategies are used: vector space model and probabilistic ranking principle model. A prototype of the KCT was implemented to demonstrate the concept. The results from KCT are compared with the outputs from a manual knowledge acquisition process in terms of amount of information retrieved and the process time spent. An analysis of the results shows that the process time to retrieve knowledge components (e.g., facts, rules, protocols, and uncertainty) of KCT is about half that of the manual process, and the number of knowledge components retrieved from knowledge acquisition activities is four times more than that retrieved through a manual process 相似文献