全文获取类型
收费全文 | 96682篇 |
免费 | 11026篇 |
国内免费 | 11560篇 |
专业分类
系统科学 | 4034篇 |
丛书文集 | 2408篇 |
教育与普及 | 1945篇 |
理论与方法论 | 319篇 |
现状及发展 | 677篇 |
研究方法 | 177篇 |
综合类 | 109700篇 |
自然研究 | 8篇 |
出版年
2024年 | 457篇 |
2023年 | 1009篇 |
2022年 | 1503篇 |
2021年 | 1854篇 |
2020年 | 1996篇 |
2019年 | 3872篇 |
2018年 | 4110篇 |
2017年 | 4462篇 |
2016年 | 4740篇 |
2015年 | 5351篇 |
2014年 | 6194篇 |
2013年 | 5640篇 |
2012年 | 5485篇 |
2011年 | 5686篇 |
2010年 | 5688篇 |
2009年 | 5497篇 |
2008年 | 5083篇 |
2007年 | 5120篇 |
2006年 | 4038篇 |
2005年 | 3720篇 |
2004年 | 3504篇 |
2003年 | 2864篇 |
2002年 | 2795篇 |
2001年 | 2528篇 |
2000年 | 2273篇 |
1999年 | 3150篇 |
1998年 | 2628篇 |
1997年 | 2664篇 |
1996年 | 2334篇 |
1995年 | 1998篇 |
1994年 | 1901篇 |
1993年 | 1760篇 |
1992年 | 1538篇 |
1991年 | 1423篇 |
1990年 | 1150篇 |
1989年 | 988篇 |
1988年 | 879篇 |
1987年 | 518篇 |
1986年 | 388篇 |
1985年 | 152篇 |
1984年 | 43篇 |
1983年 | 21篇 |
1982年 | 20篇 |
1981年 | 10篇 |
1980年 | 12篇 |
1977年 | 26篇 |
1973年 | 10篇 |
1972年 | 68篇 |
1968年 | 12篇 |
1967年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
101.
连铸坯角部传热过程的数值模拟 总被引:1,自引:0,他引:1
在连铸理论与实践研究的基础上,提出了系数法铸坯角部热通量模型,为准确研究铸坯角部传热、应力和角部缺陷的产生提供了条件。 相似文献
102.
在考察针刺穴位治疗作用的基础上,根据现有的实验事实,将人体经络的观念和经改进后的神经-内分泌-免疫系统的观念统一起来,提出人体经络是具有敏感节点和功能连接的神经-内分泌-免疫网络的假说。人体经络的复杂网络不仅是遍及全身的系统,而且可以通过敏感节点及其功能连接对身体起调控作用。 相似文献
103.
104.
显著的移民资本流动已经在南朝鲜与延边之间发生。延边当地政府支持劳动力移民,支持随后的汇款额利用所带来的渐进利益。官方对成功的移民者和他们同延边经济发展的整合不感兴趣。他们已经采取措施推动移民但是并没有出台有效的政策用以将新资本转移到延边,并将它们注入当地发展中。到目前为止重要的资源并没有被触及。 相似文献
105.
论新形势下国企的思想政治工作 总被引:1,自引:0,他引:1
Liu Guangli 《科学之友》2007,(11)
笔者提出了国有企业在新形势下要有新发展,需要靠强大的思想政治工作,并论述了一些具体做法。 相似文献
106.
XIE Xianjian WEI Fangqiang BAI Jingwen LAI Ting 《武汉大学学报:自然科学英文版》2007,12(4):729-736
In this experiment, using the methods of drought-stress in the pot and PEG simulative drought-stress, three native rocky-slope grasses Pogonatherum panideum(Lam.) Hack, Erioophorum comosum nees and Cynodon dactylon cultivated in the pots were selected as materials to study their drought-resistance by analyzing the indexes such as the leaf area index, the drying roots accumulation, the holding water ability of leaf, the relative conductance of leaf, the soluble protein, chlorophyll. At the same time, by comparing with membership function value of each index, the order of each grass drought-resistance was decided. The results showed that the drought-resistance of Erioophorum comosum nees was stronger than Cynodon dactylon and drought-resistance of Cynodon dactylon was stronger than Pogonatherum panideum (Lam.) Hack. The purpose of the experimental results was to find theoretical foundations for selecting and cultivating native protecting-slope vegetations to adapt to rocky slopes. 相似文献
107.
刘克玲 《国外科技新书评介》2007,(10):11-12
本书是以作者给研究生讲课时的讲稿为基础撰写的,对象是生物化学、化学、分子生物物理学和分子生物结构设计等交叉学科方面的研究生。书中还讲述了有关光合天线以及光合作用反应中心方面的实验信息。 相似文献
108.
High-density event-related potentials (ERPs) were measured when participants were required to evaluate oneself, significant others (father and mother) and the most familiar public figures (Lei Feng and Jiang Qing) based on trait adjectives. There were three referential conditions and a non-referential control condition including self-evaluation (SE), significant other-evaluation (SOE), general other-evaluation (GOE), and semantic positivity-evaluation (SPE). The behavioral data showed that RTs to GOE condition were longer than the other three conditions. Scalp ERP analysis revealed that (1) SPE condition elicited a more negative N2 than SE condition, which was associated with inhibition of responses; (2) SE condition elicited a more positive P300 than SPE condition, which was an index of attention to self-relevant stimuli; (3) there was no difference on the amplitude and latency of P300 between SE and SOE conditions, which reflected that the concept of “self” included intimate others (e.g., father and mother) in Chinese culture. 相似文献
109.
莱钢特钢厂20CrMnTiH钢材成分波动较大,淬透性带HRC8~10,范围较大,制约了齿轮钢质量的进一步提高.通过研究,发现铸坯中心偏析尤其是碳偏析为主要问题.通过工艺优化采取各项措施,尤其增加电磁搅拌后,中心碳偏析得到明显改善;C控制在0.19%~0.20%的炉次达到了95.6%;淬透性带控制在HRC6内的达到了92.1%;在HRC4内的达到了86.2%;提高了产品质量,满足了用户需求. 相似文献
110.
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