全文获取类型
收费全文 | 108677篇 |
免费 | 3126篇 |
国内免费 | 5350篇 |
专业分类
系统科学 | 4664篇 |
丛书文集 | 3747篇 |
教育与普及 | 4107篇 |
理论与方法论 | 445篇 |
现状及发展 | 554篇 |
研究方法 | 313篇 |
综合类 | 103304篇 |
自然研究 | 19篇 |
出版年
2024年 | 550篇 |
2023年 | 1254篇 |
2022年 | 1843篇 |
2021年 | 2154篇 |
2020年 | 1445篇 |
2019年 | 615篇 |
2018年 | 975篇 |
2017年 | 1295篇 |
2016年 | 1269篇 |
2015年 | 2553篇 |
2014年 | 3632篇 |
2013年 | 3530篇 |
2012年 | 3949篇 |
2011年 | 4623篇 |
2010年 | 4586篇 |
2009年 | 5118篇 |
2008年 | 5817篇 |
2007年 | 5501篇 |
2006年 | 4364篇 |
2005年 | 4281篇 |
2004年 | 3148篇 |
2003年 | 2900篇 |
2002年 | 3313篇 |
2001年 | 3437篇 |
2000年 | 3373篇 |
1999年 | 5212篇 |
1998年 | 4595篇 |
1997年 | 4794篇 |
1996年 | 4406篇 |
1995年 | 3875篇 |
1994年 | 3530篇 |
1993年 | 3062篇 |
1992年 | 2646篇 |
1991年 | 2350篇 |
1990年 | 2046篇 |
1989年 | 1820篇 |
1988年 | 1504篇 |
1987年 | 948篇 |
1986年 | 508篇 |
1985年 | 192篇 |
1984年 | 49篇 |
1983年 | 15篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1974年 | 6篇 |
1973年 | 5篇 |
1971年 | 7篇 |
1970年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
71.
用ASP技术实现网站新闻发布系统 总被引:3,自引:0,他引:3
李鑫 《淮北煤炭师范学院学报(自然科学版)》2008,29(4)
提出了一个基于WWW环境的新闻动态发布系统.系统采用ASP+ACCESS的开发模式,以数据库为核心,实现网站的新闻动态管理,有比较完善的后台管理系统,用户完全可以按照自己的网站修改前台分类,以使其与站点内容保持一致. 相似文献
72.
73.
WANG Xibo ZHOU Benhai YU Gei LI Qian 《武汉大学学报:自然科学英文版》2007,12(5):946-950
μC/OS-Ⅱ is an open source real-time kernel adopting priority preemptive schedule strategy. Aiming at the problem of μC/OS-Ⅱ failing to support homology priority tasks scheduling, an approach for solution is proposed. The basic idea is adding round-robin scheduling strategy in its original scheduler in order to schedule homology priority tasks through time slice roundrobin. Implementation approach is given in detail. Firstly, the Task Control Block (TCB) is extended. And then, a new priority index table is created, in which each index pointer points to a set of homology priority tasks. Eventually, on the basis of reconstructing μC/OS-Ⅱ real-time kernel, task scheduling module is rewritten. Otherwise, schedulability of homology task supported by modified kernel had been analyzed, and deadline formula of created homology tasks is given. By theoretical analysis and experiment verification, the modified kernel can support homology priority tasks scheduling, meanwhile, it also remains preemptive property of original μC/OS-Ⅱ. 相似文献
74.
75.
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
76.
77.
提出了一种基于正六边形线阵CCD探测器的运动目标探测系统.系统不仅可以实现360°范围内环形视场探测,还可以实时显示运动目标的位置及角速度信息,达到搜索跟踪的目的.在硬件设计方面,提出并实现了基于CPLD和AVR的电路方案.在算法设计方面,设计了适于周视场运动目标探测算法. 相似文献
78.
Finding finer functions for partially characterized proteins by protein-protein interaction networks
LI YanHui GUO Zheng MA WenCai YANG Da WANG Dong ZHANG Min ZHU ding ZHONG GuoCai LI YongJin YAO Chen WANG Jing 《科学通报(英文版)》2007,52(24):3363-3370
Based on high-throughput data, numerous algorithms have been designed to find functions of novel proteins. However, the effectiveness of such algorithms is currently limited by some fundamental factors, including (1) the low a-priori probability of novel proteins participating in a detailed function; (2) the huge false data present in high-throughput datasets; (3) the incomplete data coverage of functional classes; (4) the abundant but heterogeneous negative samples for training the algorithms; and (5) the lack of detailed functional knowledge for training algorithms. Here, for partially characterized proteins, we suggest an approach to finding their finer functions based on protein interaction sub-networks or gene expression patterns, defined in function-specific subspaces. The proposed approach can lessen the above-mentioned problems by properly defining the prediction range and functionally filtering the noisy data, and thus can efficiently find proteins’ novel functions. For thousands of yeast and human proteins partially characterized, it is able to reliably find their finer functions (e.g., the translational functions) with more than 90% precision. The predicted finer functions are highly valuable both for guiding the follow-up wet-lab validation and for providing the necessary data for training algorithms to learn other proteins. 相似文献
79.
揭示了城市技术创新系统和城乡统筹发展的内涵,并在技术创新、增长极和区域经济等理论框架下阐述了城市技术创新与城乡统筹发展的关系,进而提出城市技术创新促进城乡统筹的路径。 相似文献
80.
新建地方院校实验室仪器设备管理工作探讨 总被引:1,自引:0,他引:1
张勇 《科技情报开发与经济》2007,17(34):231-232
分析了新建地方院校实验室仪器设备管理工作的特点和问题,探讨了加强仪器设备管理的措施。 相似文献