全文获取类型
收费全文 | 4758篇 |
免费 | 45篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 41篇 |
综合类 | 7篇 |
化学工业 | 359篇 |
金属工艺 | 36篇 |
机械仪表 | 68篇 |
建筑科学 | 123篇 |
矿业工程 | 15篇 |
能源动力 | 87篇 |
轻工业 | 221篇 |
水利工程 | 21篇 |
石油天然气 | 12篇 |
无线电 | 451篇 |
一般工业技术 | 397篇 |
冶金工业 | 2723篇 |
原子能技术 | 34篇 |
自动化技术 | 219篇 |
出版年
2022年 | 13篇 |
2021年 | 29篇 |
2020年 | 16篇 |
2019年 | 24篇 |
2018年 | 24篇 |
2017年 | 26篇 |
2016年 | 27篇 |
2015年 | 22篇 |
2014年 | 37篇 |
2013年 | 137篇 |
2012年 | 78篇 |
2011年 | 97篇 |
2010年 | 78篇 |
2009年 | 77篇 |
2008年 | 90篇 |
2007年 | 90篇 |
2006年 | 94篇 |
2005年 | 73篇 |
2004年 | 77篇 |
2003年 | 73篇 |
2002年 | 66篇 |
2001年 | 76篇 |
2000年 | 51篇 |
1999年 | 148篇 |
1998年 | 868篇 |
1997年 | 454篇 |
1996年 | 338篇 |
1995年 | 197篇 |
1994年 | 173篇 |
1993年 | 179篇 |
1992年 | 48篇 |
1991年 | 58篇 |
1990年 | 66篇 |
1989年 | 46篇 |
1988年 | 47篇 |
1987年 | 50篇 |
1986年 | 62篇 |
1985年 | 60篇 |
1984年 | 51篇 |
1983年 | 37篇 |
1982年 | 48篇 |
1981年 | 40篇 |
1980年 | 37篇 |
1979年 | 21篇 |
1978年 | 29篇 |
1977年 | 82篇 |
1976年 | 150篇 |
1975年 | 20篇 |
1973年 | 24篇 |
1971年 | 13篇 |
排序方式: 共有4814条查询结果,搜索用时 0 毫秒
1.
Presents the Satellite Communications Network Expert (SaNE), a knowledge-based aid designed to provide engineering support for fault diagnosis. The SaNE is composed of two elements: a satcom network model, which simulates the structure and functionality of a system based loosely upon a large military satcom network, and a diagnostic component, which uses knowledge- and model-based reasoning techniques to analyse system anomalies and diagnose possible causes for the alarms such networks generate. The development cycle is described, emphasising lessons learnt during development and testing and the advantages and disadvantages of the techniques applied. The goal of the SaNE project is primarily commercial acceptance rather than innovation. The authors illustrate how novel concepts can be implemented in a practical system without compromising this goal 相似文献
2.
A model is established to quantify the influence of interfacial microcracks on the elastic properties of a particulate composite using a combination of theoretical and finite element analysis. A unique way to construct physical models which could accommodate both crack size and crack density is proposed. Based on energy principles, the influence of a dilute concentration of interfacial microcracks is first studied. The case of a finite concentration of microcracks is solved subsequently by combining the dilute concentration solutions and the differential scheme. Both cases agreed well with existing composite theories for the limiting condition of complete decohesion. The final model predicts the effective elastic properties as functions of both crack size and microcrack density. 相似文献
3.
Among engineers and scientists, MATLAB is one of the most popular computational packages. Part of MATLAB's popularity stems from its simple, yet sophisticated, graphics capabilities. While basic plots are relatively easy to obtain, specialized plots require a little more effort to produce. This article introduces MATLAB's Handle Graphics, which provides a mechanism to fully control and customize graphics objects in MATLAB. With a basic understanding of Handle Graphics, users can produce plots that meet the unique needs and quality standards commonly required by the profession, several examples are presented to illustrate the concepts. 相似文献
4.
5.
Renal length has been measured by ultrasound in 237 subjects with homozygous sickle cell (SS) disease, 147 with sickle cell-hemoglobin C (SC) disease, and in 78 age-matched controls with a normal hemoglobin (AA) genotype. As expected, renal length increased with age in all genotypes but mean length was significantly greater in SS disease compared with SC disease (mean difference 4.3 mm after adjustment for height) and significantly greater in both genotypes than in AA controls (SS/AA difference 9.2 mm, SC/AA difference 5.0 mm after adjustment for height). Examination of relationships between renal length and some hematological indices (hemoglobin, fetal hemoglobin, reticulocyte counts, alpha thalassemia status) in SS or SC disease showed only a significant negative correlation with hemoglobin and positive correlation with reticulocyte count in SS disease. Further analysis suggested that the stronger relationship was between renal length and high reticulocyte count. The mechanism of renal enlargement is unknown although glomerular hypertrophy and increased renal blood volume are likely contributors. 相似文献
6.
M Hessing D Kanters H Takeya C van 't Veer TM Hackeng S Iwanaga BN Bouma 《Canadian Metallurgical Quarterly》1993,317(3):228-232
Human C4b-binding protein (C4BP) functions as a cofactor to factor I in the degradation of C4b and accelerates the decay rate of the C4b2a complex. In this study we describe a monoclonal antibody directed against the alpha-chain of C4BP that inhibits the binding of C4b to C4BP. In order to identify the structural domain of the alpha-chain of C4BP that interacts with C4b, tryptic fragments of C4BP were generated. Amino acid sequence analysis of the fragments revealed that the residues Ser333-Arg356 of the alpha-chain of C4BP contain the epitope of this antibody, and as a consequence, that this part of the alpha-chain of C4BP is likely to be involved in the interaction with C4b. 相似文献
7.
A deletion mutant of the catalytic RNA component of Escherichia coli RNase P missing residues 87-241 retains the ability to interact with the protein component to form a functional catalyst. The deletion of this phylogenetically conserved region significantly increases the Km, indicating that the deleted structures may be important for binding to the precursor tRNA substrate but not for the cleavage reaction. Under some reaction conditions, this RNase P deletion mutant can become a relatively non-specific nuclease, indicating that this RNA's catalytic center may be more exposed. The catalytic core of the RNase P is formed by less than one third of the 377 residues of the RNase P RNA. 相似文献
8.
CM Wheeler CA Parmenter WC Hunt TM Becker CE Greer A Hildesheim MM Manos 《Canadian Metallurgical Quarterly》1993,20(5):286-289
OBJECTIVES: To confirm the risk factors for genital human papillomavirus (HPV) infection. GOAL OF THIS STUDY: To investigate risk factors for HPV detection apart from the correlated risk factors for cervical neoplasia. STUDY DESIGN: Cervical human papillomavirus (HPV) DNA was assessed in 357 cytologically normal women attending the University of New Mexico student health center. Cervical swab samples were obtained for HPV DNA detection and typing using a PCR-based DNA amplification system. Possible determinants of cervical HPV were examined including age, ethnicity, history of sexually transmitted disease, oral contraceptive use, smoking, age at first intercourse, lifetime number of sex partners, marital status, and history of pregnancy. RESULTS: A 44.3% overall prevalence of cervical HPV was observed. On univariate analysis, factors associated with increasing HPV prevalence included higher lifetime number of sex partners and single marital status. After adjustment for potential confounding variables, we found that HPV prevalence increased with higher lifetime number of sexual partners. CONCLUSION: These findings, along with those from the companion reports in this issue of the journal, support the sexual route of transmission of the virus. 相似文献
9.
Arthur Green 《Information Systems Management》1991,8(3):67-70
Applying information systems strategic planning (ISSP) theory to a practical planning effort is not a straightforward endeavor, and the penalties of a misapplied planning exercise are high. IS managers do not need another conceptual framework for ISSP as much as they need a practical point of view on driving the planning effort to produce tangible, high-quality results. 相似文献
10.