全文获取类型
收费全文 | 3307篇 |
免费 | 101篇 |
国内免费 | 154篇 |
专业分类
系统科学 | 103篇 |
丛书文集 | 62篇 |
教育与普及 | 67篇 |
理论与方法论 | 10篇 |
现状及发展 | 48篇 |
研究方法 | 27篇 |
综合类 | 3245篇 |
出版年
2024年 | 8篇 |
2023年 | 25篇 |
2022年 | 38篇 |
2021年 | 54篇 |
2020年 | 28篇 |
2019年 | 8篇 |
2018年 | 22篇 |
2017年 | 22篇 |
2016年 | 31篇 |
2015年 | 51篇 |
2014年 | 72篇 |
2013年 | 74篇 |
2012年 | 91篇 |
2011年 | 115篇 |
2010年 | 91篇 |
2009年 | 109篇 |
2008年 | 126篇 |
2007年 | 135篇 |
2006年 | 107篇 |
2005年 | 110篇 |
2004年 | 109篇 |
2003年 | 71篇 |
2002年 | 89篇 |
2001年 | 100篇 |
2000年 | 111篇 |
1999年 | 198篇 |
1998年 | 179篇 |
1997年 | 182篇 |
1996年 | 172篇 |
1995年 | 171篇 |
1994年 | 157篇 |
1993年 | 132篇 |
1992年 | 114篇 |
1991年 | 97篇 |
1990年 | 79篇 |
1989年 | 92篇 |
1988年 | 67篇 |
1987年 | 54篇 |
1986年 | 30篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1972年 | 3篇 |
1971年 | 3篇 |
1970年 | 3篇 |
1969年 | 2篇 |
1968年 | 3篇 |
1967年 | 2篇 |
排序方式: 共有3562条查询结果,搜索用时 15 毫秒
131.
添加剂对氧化铝微粉—水浓悬浮液流变行为的影响 总被引:1,自引:0,他引:1
研究结果表明:掺入添加剂,能够改善氧化铝微粉浓悬浮液的流动性、触变性和粘弹性等流变性能,使系统胀性行为减弱,塑性行为增强,将有利于以氧化铝微粉为主的不定形耐火材料浇注料工作性的改善。 相似文献
132.
Lin Z Bei JX Shen M Li Q Liao Z Zhang Y Lv Q Wei Q Low HQ Guo YM Cao S Yang M Hu Z Xu M Wang X Wei Y Li L Li C Li T Huang J Pan Y Jin O Wu Y Wu J Guo Z He P Hu S Wu H Song H Zhan F Liu S Gao G Liu Z Li Y Xiao C Li J Ye Z He W Liu D Shen L Huang A Wu H Tao Y Pan X Yu B Tai ES Zeng YX Ren EC Shen Y Liu J Gu J 《Nature genetics》2012,44(1):73-77
To identify susceptibility loci for ankylosing spondylitis, we performed a two-stage genome-wide association study in Han Chinese. In the discovery stage, we analyzed 1,356,350 autosomal SNPs in 1,837 individuals with ankylosing spondylitis and 4,231 controls; in the validation stage, we analyzed 30 suggestive SNPs in an additional 2,100 affected individuals and 3,496 controls. We identified two new susceptibility loci between EDIL3 and HAPLN1 at 5q14.3 (rs4552569; P = 8.77 × 10(-10)) and within ANO6 at 12q12 (rs17095830; P = 1.63 × 10(-8)). We also confirmed previously reported associations in Europeans within the major histocompatibility complex (MHC) region (top SNP, rs13202464; P < 5 × 10(-324)) and at 2p15 (rs10865331; P = 1.98 × 10(-8)). We show that rs13202464 within the MHC region mainly represents the risk effect of HLA-B*27 variants (including HLA-B*2704, HLA-B*2705 and HLA-B*2715) in Chinese. The two newly discovered loci implicate genes related to bone formation and cartilage development, suggesting their potential involvement in the etiology of ankylosing spondylitis. 相似文献
133.
Resource allocation (RA) is the problem of allocating resources among various artifacts or business units to meet one or more expected goals, such a.s maximizing the profits, minimizing the costs, or achieving the best qualities. A complex multiobjective RA is addressed, and a multiobjective mathematical model is used to find solutions efficiently. Then, all improved particie swarm algorithm (mO_PSO) is proposed combined with a new particle diversity controller policies and dissipation operation. Meanwhile, a modified Pareto methods used in PSO to deal with multiobjectives optimization is presented. The effectiveness of the provided algorithm is validated by its application to some illustrative example dealing with multiobjective RA problems and with the comparative experiment with other algorithm. 相似文献
134.
"大系统"理论及其在温室系统建模中的应用 总被引:2,自引:0,他引:2
在简介现代系统工程发展的基础上,引入了“大系统”的基本概念,综述了“大系统”理论的特征,分类和大系统的控制邮将“大系统”理论应用到温室系统建立综合动态仿真模型中的思路,最后对建模方法进行了探讨。 相似文献
135.
电力安全生产关系到国家的财产安全、人民生活利益和电力职工的安康,是电力企业最根本的效益所在.电力安全生产是电力企业生存和发展的基石,影响着电力企业本身的内外形象,在我国经济社会正处于高速发展的大好时期,电力生产安全管理显得尤为重要. 相似文献
136.
Leaf rust caused by Puccinia triticina is an economically-important disease in wheat worldwide.A combination of different types of resistance genes may significantly enhance rust resistance under rust-favorable conditions.To investigate the interactions between the rust resistance gene Lr34 and the lesion mimic gene lm on 1BL in Ning 7840,a segregating F8-10 population of 180 recombinant inbred lines was developed from Ning 7840/Chokwang and evaluated for both lesion mimic expression and leaf rust response at the adult plant stage in a greenhouse.A major quantitative trait locus(QTL),derived from Sumai 3,was co-localized with Lr34 on chromosome 7D and explained 41.5% of phenotypic variations for rust severity and 22.1% for leaf tip necrosis(LTN).The presence of Lr34 was confirmed by Lr34-specific markers cssfr1 and cssfr2 in Ning 7840 and Sumai 3.Unlike Lr34,lm conditioned a spontaneous lesion mimic phenotype and had a significant effect on reducing uredinial size,and a smaller effect on severity.Additive effects were observed between lm and Lr34 for severity and LTN,and an epistatic effect was observed for infection type.Single marker analysis also identified several other QTL with minor effects on severity,infection type,or LTN. 相似文献
137.
138.
The abundant entities and entity-attribute relations in medical websites are important data resources for medical research. However, the medical websites are usually characterized of storing entity and attribute values in different pages. To extract those data records efficiently, we propose an automatic extraction system which is related to entity and attribute relations (attributes and values) of separate storage. Our system includes following modules: (1) rich-information interactive annotation page rendering; (2) separate storage attribute relations annotating; (3) annotated relations for pattern generating and data records extracting. This paper presents the relations about the attributes which are stored in many pages by effective annotation, then generates rules for data records extraction. The experiments show that the system can not only complete attribute relations of separate storage extraction, but also be compatible with regular relation extraction, while maintaining high accuracy. 相似文献
139.
140.
正作为神经科学研究超级大国的美国,正拟启动尖端创新神经技术脑研究计划。该计划此前称作脑活动图计划,已经过一年多的筹备性论证。计划的主要目标是,通过包括纳米技术在内的一系列技术创新,全面构造神经活动图谱,以求在神经-精神疾病诊治及智能机开发上取得突破。围绕计划目标之可行性存在大量争鸣。 相似文献