全文获取类型
收费全文 | 16219篇 |
免费 | 553篇 |
国内免费 | 963篇 |
专业分类
系统科学 | 672篇 |
丛书文集 | 469篇 |
教育与普及 | 324篇 |
理论与方法论 | 79篇 |
现状及发展 | 89篇 |
研究方法 | 56篇 |
综合类 | 16040篇 |
自然研究 | 6篇 |
出版年
2024年 | 50篇 |
2023年 | 158篇 |
2022年 | 248篇 |
2021年 | 267篇 |
2020年 | 214篇 |
2019年 | 127篇 |
2018年 | 172篇 |
2017年 | 179篇 |
2016年 | 215篇 |
2015年 | 393篇 |
2014年 | 559篇 |
2013年 | 571篇 |
2012年 | 609篇 |
2011年 | 677篇 |
2010年 | 627篇 |
2009年 | 691篇 |
2008年 | 736篇 |
2007年 | 742篇 |
2006年 | 633篇 |
2005年 | 612篇 |
2004年 | 526篇 |
2003年 | 704篇 |
2002年 | 1075篇 |
2001年 | 889篇 |
2000年 | 621篇 |
1999年 | 822篇 |
1998年 | 563篇 |
1997年 | 564篇 |
1996年 | 594篇 |
1995年 | 511篇 |
1994年 | 485篇 |
1993年 | 343篇 |
1992年 | 315篇 |
1991年 | 317篇 |
1990年 | 234篇 |
1989年 | 245篇 |
1988年 | 207篇 |
1987年 | 126篇 |
1986年 | 72篇 |
1985年 | 14篇 |
1984年 | 8篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1972年 | 2篇 |
1970年 | 3篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1962年 | 1篇 |
1955年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
21.
张志跃 《山东大学学报(理学版)》2002,37(2):120-123
应用交替分段显-隐方法求解变系数对流扩散方程,此方法具有很好的并行性且无条件稳定。 相似文献
22.
数字调制方式的识别研究 总被引:5,自引:0,他引:5
数字调制方式的识别对于通信信号分析有着重要的作用 .此文首先介绍了数字调制方式的识别算法(DMRA) ,即判决理论算法的原理 ;然后提出了一种基于该算法的判决流程 ;最后在软件环境中进行计算机仿真 ,通过实验数据对该算法进行修正 .仿真结果表明 ,该修正算法具有较高的识别率和良好的可行性 . 相似文献
23.
Science Letters: A synthetic Toll-like receptor 2 ligand decreases allergic immune responses in a mouse rhinitis model sensitized to mite allergen
下载免费PDF全文
![点击此处可从《浙江大学学报(自然科学英文版)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
It has been proposed that activation of Toll-like receptors (TLRs) plays crucial roles in the polarization of adaptive immune responses. A synthetic Toll-like receptor 2 (TLR2) ligand, Pam3CSK4, has been reported to modulate the balance of Th1/Th2 responses. We evaluated the modulation effect of Pam3CSK4 on allergic immune response in a mouse rhinitis model sensitized to house dust mite allergen (HDM). Mice were sensitized and challenged with Dermatophagoidesfarinae allergen (Der f), and then the allergic mice were treated by Pam3CSK4. Nasal allergic symptoms and eosinophils were scored. Der f-specific cytokine responses were examined in the splenocytes and bronchoalveolar lavage fluid (BALF). Serum level of total IgE was also detected. After establishing a mouse allergic rhinitis model with HDM, we have showed that Pam3CSK4 treatment not only ameliorated the nasal allergic symptoms remarkably but also decreased the eosinophils and total inflammation cells in BALF significantly. Analysis of cytokine profile found that IFN-7 released from either BALF or stimulated splenocytes increased markedly in Pam3CSK4-treated mice, while IL-13 decreased significantly. Moreover, serum level of total IgE was significantly lower in Pam3CSK4-treated mice than in the untreated. Thus, in an allergic rhinitis mouse model developed with HDM, Pam3CSK4 was shown to exhibit an antiallergic effect, indicating its potential application in allergic diseases. 相似文献
24.
Duan Jinqing Liu Hongbin Zhang Xinian Lu Hongmin Gou Ai Liu Zheng Wang Tao Ge Rili 《中国工程科学》2006,4(2):183-186
Study Objective: To compare and analyze the changes of the pulmonary-artery pressure of the migrants coming from different elevation in the hypoxic environment of 4636 - 4907 m extreme altitude. To explore the susceptibility to hypoxic pulmonary-artery hypertension (PH) in the subjects from different altitude and profession. Methods: By using Color Doppler Ultmsonography (CDU), measuring the pulmonary-artery pressure of 207 healthy men, who had continuously being lived and worked at the extreme altitude for more than six months, and then were divided into three groups according to their profession and the altitude of original living place. Results: There was a significant difference in the outcomes of pulmonary-artery pressure from the 3 groups. Conclusions: Altitude of original living place, labor intensity are some of factors that impact the pulmonary-artery pressure of the people who exposure to a hypoxic environment. The pulmonary- artery pressure of person without strenuously physical work experience was more sensitive to hypoxic surroundings than that of labor workers. It was not always the fact at an extreme altitude that the moderate altitude mountaineers were superior to other migrants from a lower altitude or plain. The higher PH was found in the groups of the moderate altitude mountaineers and labor workers. It is unlikely certain that one with PH would surfer from HAPE. 相似文献
25.
Prof. Zhu Zuoyan Vice President of NSFC met with the National Institute of Agricultural Research 《中国科学基金(英文版)》2007,15(1):33
Prof. Zhu Zuoyan, Vice President of NSFC, met with the National Institute of Agricultural Research (INRA) delegation led by its Deputy Director General, Prof. Guy Riba on Jan. 18, 2007. 相似文献
26.
本文对绢纺生产用抗静电剂的配方进行了研究,研制出SS1及SS2绢纺抗静电剂。应用表明,采用此类抗静电剂,不但降低了生产中的静电,而且提高了梳折;在圆梳系统中提高了3.23%,在精梳系统中提高了3.1%;同时精绵的长度和强力也有所增加,从而提高了经济效益。 相似文献
27.
28.
介绍新型防水材料SBS改性沥青柔性油毡的性能、施工工艺、操作方法及保证质量的措施,并提出存在的问题及施工中注意事项。 相似文献
29.
论述了以8031为控制核心的钢丝绳张力单片机检测系统的工作原理、数学模型和系统组成,重点介绍了钢丝绳张力检测的工作原理、主要硬件电路的设计特点及软件设计思想,提供了部分硬件电路图及控制软件的流程图。该系统具有置数、动态显示、数据处理、打印及人机对话等功能,并且使用方便,造价低廉。 相似文献
30.
本文论述了描述微波与生物组织相互作用的数学表达式,讨论工作频率选择、透入深度、反射、极化、泄漏及防护等实际问题。 相似文献