全文获取类型
收费全文 | 64684篇 |
免费 | 2673篇 |
国内免费 | 1846篇 |
专业分类
电工技术 | 3339篇 |
技术理论 | 11篇 |
综合类 | 5244篇 |
化学工业 | 11672篇 |
金属工艺 | 1769篇 |
机械仪表 | 2691篇 |
建筑科学 | 6789篇 |
矿业工程 | 2930篇 |
能源动力 | 1290篇 |
轻工业 | 6135篇 |
水利工程 | 1779篇 |
石油天然气 | 5825篇 |
武器工业 | 433篇 |
无线电 | 3445篇 |
一般工业技术 | 4173篇 |
冶金工业 | 4490篇 |
原子能技术 | 284篇 |
自动化技术 | 6904篇 |
出版年
2024年 | 156篇 |
2023年 | 414篇 |
2022年 | 950篇 |
2021年 | 1286篇 |
2020年 | 1426篇 |
2019年 | 824篇 |
2018年 | 730篇 |
2017年 | 1086篇 |
2016年 | 1295篇 |
2015年 | 1487篇 |
2014年 | 4142篇 |
2013年 | 2960篇 |
2012年 | 4312篇 |
2011年 | 4506篇 |
2010年 | 4018篇 |
2009年 | 3976篇 |
2008年 | 3239篇 |
2007年 | 4408篇 |
2006年 | 4502篇 |
2005年 | 4109篇 |
2004年 | 3570篇 |
2003年 | 3365篇 |
2002年 | 2652篇 |
2001年 | 2267篇 |
2000年 | 1760篇 |
1999年 | 1317篇 |
1998年 | 1003篇 |
1997年 | 703篇 |
1996年 | 584篇 |
1995年 | 476篇 |
1994年 | 319篇 |
1993年 | 234篇 |
1992年 | 174篇 |
1991年 | 121篇 |
1990年 | 94篇 |
1989年 | 76篇 |
1988年 | 82篇 |
1987年 | 51篇 |
1986年 | 37篇 |
1985年 | 29篇 |
1984年 | 47篇 |
1983年 | 24篇 |
1982年 | 25篇 |
1966年 | 24篇 |
1964年 | 20篇 |
1959年 | 30篇 |
1958年 | 18篇 |
1957年 | 18篇 |
1955年 | 21篇 |
1954年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
对"比较法"原理和应用情况进行了分析,说明其在房地产开发中能够科学地预测房地产的价格和收益,从而提高财务分析的科学性和权威性,为项目决策提供科学依据,以促进"比较法"在房地产开发中的应用。 相似文献
32.
绿色再生混凝土利用途径与评定思路 总被引:3,自引:0,他引:3
就再生混凝土骨料进行深入系统的研究 ,建立了一套与现行评价天然骨料标准相一致的评定方法 ,具有工程实际意义 ,为将来实际应用作好了基础理论研究 相似文献
33.
保健食品行业GMP的实施有利HACCP的应用推广。本文应用HACCP于传统保健食品西洋参口服液生产过程中,将生产及加工过程中危害因素降最低限度,以确保产品的质量与安全。 相似文献
34.
日本落叶松是适合在北半球广泛种植的早期速生树种 ,在我国的生长适应范围比较广 ,如今在我国华北、西北、西南和华中亚热带山区的部分地区已有种植。它在造纸领域中的应用研究已经开始 ,而且已经证实是一种很有潜力的造纸木材 相似文献
36.
Education-driven research in CAD 总被引:1,自引:0,他引:1
We argue for a new research category, named education-driven research (EDR), which fills the gap between traditional field-specific research that is not concerned with educational objectives and research in education that focuses on fundamental teaching and learning principles and possibly on their customization to broad areas (such as mathematics or physics), but not to specific disciplines (such as CAD). The objective of EDR is to simplify the formulation of the underlying theoretical foundations and of specific tools and solutions in a specialized domain, so as to make them easy to understand and internalize. As such, EDR is a difficult and genuine research activity, which requires a deep understanding of the specific field and can rarely be carried out by generalists with primary expertise in broad education principles. We illustrate the concept of EDR with three examples in CAD: (1) the Split and Tweak subdivisions of a polygon and its use for generating curves, surfaces, and animations; (2) the construction of a topological partition of a plane induced by an arbitrary arrangement of edges; and (3) a romantic definition of the minimal and Hausdorff distances. These examples demonstrate the value of using analogies, of introducing evocative terminology, and of synthesizing the simplest fundamental building blocks. The intuitive understanding provided by EDR enables the students (and even the instructor) to better appreciate the limitations of a particular solution and to explore alternatives. In particular, in these examples, EDR has allowed the author to: (1) reduce the cost of evaluating a cubic B-spline curve; (2) develop a new subdivision curve that is better approximated by its control polygon than either a cubic B-spline or an interpolating 4-point subdivision curve; (3) discover how a circuit inclusion tree may be used for identifying the faces in an arrangement; and (4) rectify a common misconception about the computation of the Hausdorff error between triangle meshes. We invite the scientific community to encourage the development of EDR by publishing its results as genuine research contributions in peer-reviewed professional journals. 相似文献
37.
Youngjoong Ko Sooyong Park Jungyun Seo Soonhwang Choi 《Information and Software Technology》2007,49(11-12):1128-1140
In order to efficiently develop large-scale and complicated software, it is important for system engineers to correctly understand users’ requirements. Most requirements in large-scale projects are collected from various stakeholders located in various regions, and they are generally written in natural language. Therefore, the initial collected requirements must be classified into various topics prior to analysis phases in order to be usable as input in several requirements analysis methods. If this classification process is manually done by analysts, it becomes a time-consuming task. To solve this problem, we propose a new bootstrapping method which can automatically classify requirements sentences into each topic category using only topic words as the representative of the analysts’ views. The proposed method is verified through experiments using two requirements data sets: one written in English and the other in Korean. The significant performances were achieved in the experiments: the 84.28 and 87.91 F1 scores for the English and Korean data sets, respectively. As a result, the proposed method can provide an effective function for an Internet-based requirements analysis-supporting system so as to efficiently gather and analyze requirements from various and distributed stakeholders by using the Internet. 相似文献
38.
Advances in research on disability and rehabilitation are essential to creating equal opportunity, economic self-sufficiency, and full participation for persons with disabilities. Historically, such initiatives have focused on separate and specific areas, including neuroscience, molecular biology and genetics, gerontology, engineering and physical sciences, and social and behavioral sciences. Research on persons with disabilities should examine the broader context and trends of society that affect the total environment of persons with disabilities. This article examines the various disability paradigms across time, assessing the relative contribution of the socioecological perspective in guiding research designed to improve the lives of persons with disabilities. The authors recommend new research directions that include a focus on life span issues, biomedicine, biotechnology, the efficacy and effectiveness of current interventions, an emphasis on consumer-driven investigations within a socioecological perspective of disability, and the implications for research and practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
39.
Why was there a preponderance of women engaged in laboratory-based studies of animal behavior in Britain in the early years of the 20th century? As a new experimental subject with recently neglected potential, animal psychology then represented an opportunity for women to make further inroads into academic science. Because the study of psychology before World War I offered negligible professional opportunities for the application of the subject, the intake of students was restricted. Perhaps this encouraged academic access to it by aspiring female scientists who felt that career prospects, uncertain and socially unexpected of them in any case, were worth chancing for greater long-term rewards. The academic circumstances and contributions of 3 British female pioneers in experimental comparative psychology are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
40.
挤出成型中遇到的最严重问题是熔体破裂,应用含氟改性剂可很好地消除熔体破裂现象。介绍了含氟改性剂对线性低密度聚乙烯(LLDPE)树脂挤出性能的影响及表面性能的改善。结果表明,在LLDPE挤出成型过程中加入含氟改性剂可有效消除熔体破裂现象,降低熔体温度,减小挤出机头压力,提高挤出效率,改善制品的外观质量。 相似文献