全文获取类型
收费全文 | 38676篇 |
免费 | 2963篇 |
国内免费 | 1929篇 |
专业分类
化学 | 6016篇 |
晶体学 | 51篇 |
力学 | 3195篇 |
综合类 | 348篇 |
数学 | 3620篇 |
物理学 | 4287篇 |
综合类 | 26051篇 |
出版年
2024年 | 106篇 |
2023年 | 390篇 |
2022年 | 773篇 |
2021年 | 787篇 |
2020年 | 947篇 |
2019年 | 752篇 |
2018年 | 723篇 |
2017年 | 978篇 |
2016年 | 1055篇 |
2015年 | 1218篇 |
2014年 | 1759篇 |
2013年 | 1898篇 |
2012年 | 2151篇 |
2011年 | 2276篇 |
2010年 | 1814篇 |
2009年 | 1998篇 |
2008年 | 1981篇 |
2007年 | 2448篇 |
2006年 | 2294篇 |
2005年 | 2098篇 |
2004年 | 1926篇 |
2003年 | 1824篇 |
2002年 | 1516篇 |
2001年 | 1317篇 |
2000年 | 1250篇 |
1999年 | 1033篇 |
1998年 | 881篇 |
1997年 | 747篇 |
1996年 | 730篇 |
1995年 | 616篇 |
1994年 | 556篇 |
1993年 | 478篇 |
1992年 | 444篇 |
1991年 | 351篇 |
1990年 | 335篇 |
1989年 | 287篇 |
1988年 | 252篇 |
1987年 | 205篇 |
1986年 | 106篇 |
1985年 | 68篇 |
1984年 | 42篇 |
1983年 | 14篇 |
1982年 | 34篇 |
1981年 | 16篇 |
1980年 | 11篇 |
1979年 | 17篇 |
1978年 | 13篇 |
1977年 | 12篇 |
1976年 | 9篇 |
1957年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
《Electroanalysis》2006,18(24):2435-2440
Several hydroximethylfurfural (HMF) microbiosensors, based on a microelectrode configuration built by photolithographic techniques, have been developed. Two different biosensors based on the aldehyde dehydrogenase (ALDH) enzyme coupling with NADH oxidase (NOD) or diaphorase (Diaph) are described. Experimental variables were optimized using experimental design methodology, by central composite designs, taking the intensity registered for a given HMF solution as response. Given the reproducibility (residual standard deviation (RSD), 7.20%), repeatability (RSD=3%) and limit of detection (LOD)=1.68×10?4 mol dm?3 (α=β=0.05 and a replicate) reached by the ALDH‐Diaph microbiosensor under the optimum conditions, the analysis of HMF in honey was successfully accomplished. 相似文献
42.
A profit-maximizing supply chain network design model with demand choice flexibility 总被引:1,自引:0,他引:1
Zuo-Jun Max Shen 《Operations Research Letters》2006,34(6):673-682
We present a profit-maximizing supply chain design model in which a company has flexibility in determining which customers to serve. The company may lose a customer to competition if the price it charges is too high. We show the problem formulation and solution algorithm, and discuss computational results. 相似文献
43.
医用降温仪的设计与试验研究 总被引:2,自引:0,他引:2
介绍应用机械制冷方法设计医用降温仪的过程,并对所研制的降温仪进行试验和分析研究。 相似文献
44.
面的回转会产生立体,服装造型可以说就是面料按结构组合与面回转的原理形成的立体形态。此文通过立体构成与服装造型设计上的关系,阐明立体构成对服装造型设计的影响与作用。 相似文献
45.
We consider a resource management problem in which the management objective is to minimize fluctuations in resource stocks. Stabilizing management policies constitute the designing of memoryless state feedback control strategies for a discrete time resource model which contains unknown but bounded fluctuations. We also show that the problem of maximizing sustainable yield in an uncertain fishery can be considered as the problem of stabilizing of the stock level.The paper corresponds to an invited talk at the 14th Symposium on Operations Research, Ulm, September 6–8, 1989.The support by Yrjö Jahnsson Foundation is gratefully acknowledged.This work was supported by NSF and AFOSR under grant ECS 8602524. 相似文献
46.
47.
48.
对专科综合英语教学的探索与思考 总被引:1,自引:0,他引:1
康素霞 《曲靖师范学院学报》2002,21(2):93-95
综合英语教学是英语专业学习中的核心内容。文章就如何抓好专科综合英语教学中的语音基础及以学生为中心的教学模式展开探索与思考 相似文献
49.
Papert's (1978) appeal to reconsider the power and possibilities of the aesthetic in mathematics learning is often ignored in mathematics education research. This paper begins with the premise, put forth by Dewey (1934), that the aesthetic structures many dimensions of inquiry and experience. In the same way that using particular paintings, musical compositions, or even everyday experiences has been instrumental to attempts by philosophers to understand the aesthetic dimensions of meaning and experience in artistic domains, I propose that analysing a particular encounter with mathematics may help reveal the nature and role of the often nebulous responses of elegance, beauty, and `fit' to which mathematicians lay claim in their mathematical activity. To achieve this, I draw on and adapt the defining features of the aesthetic character of experience set forth by the aesthetician Beardsley (1982). This, in turn, sheds light on the role thataesthetics can play in mathematical inquiry and experience, and provides initial categories and conjectures that can be used to investigate the potential roles of aesthetics in mathematics learning contexts.This revised version was published online in September 2005 with corrections to the Cover Date. 相似文献
50.
Let G=(V(G),E(G)) be a graph. A (n,G, λ)‐GD is a partition of the edges of λKn into subgraphs (G‐blocks), each of which is isomorphic to G. The (n,G,λ)‐GD is named as graph design for G or G‐decomposition. The large set of (n,G,λ)‐GD is denoted by (n,G,λ)‐LGD. In this work, we obtain the existence spectrum of (n,P3,λ)‐LGD. © 2002 Wiley Periodicals, Inc. J Combin Designs 10: 151–159, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jcd.10008 相似文献