全文获取类型
收费全文 | 24256篇 |
免费 | 2411篇 |
国内免费 | 3141篇 |
专业分类
化学 | 7205篇 |
晶体学 | 285篇 |
力学 | 691篇 |
综合类 | 236篇 |
数学 | 1518篇 |
物理学 | 4617篇 |
综合类 | 15256篇 |
出版年
2024年 | 88篇 |
2023年 | 238篇 |
2022年 | 486篇 |
2021年 | 558篇 |
2020年 | 589篇 |
2019年 | 501篇 |
2018年 | 549篇 |
2017年 | 611篇 |
2016年 | 647篇 |
2015年 | 941篇 |
2014年 | 1240篇 |
2013年 | 1441篇 |
2012年 | 1492篇 |
2011年 | 1716篇 |
2010年 | 1585篇 |
2009年 | 1627篇 |
2008年 | 1765篇 |
2007年 | 1808篇 |
2006年 | 1521篇 |
2005年 | 1404篇 |
2004年 | 1178篇 |
2003年 | 1061篇 |
2002年 | 1345篇 |
2001年 | 1245篇 |
2000年 | 900篇 |
1999年 | 665篇 |
1998年 | 338篇 |
1997年 | 292篇 |
1996年 | 273篇 |
1995年 | 226篇 |
1994年 | 216篇 |
1993年 | 207篇 |
1992年 | 166篇 |
1991年 | 166篇 |
1990年 | 137篇 |
1989年 | 160篇 |
1988年 | 104篇 |
1987年 | 106篇 |
1986年 | 55篇 |
1985年 | 43篇 |
1984年 | 24篇 |
1983年 | 21篇 |
1982年 | 13篇 |
1981年 | 25篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1965年 | 3篇 |
1959年 | 2篇 |
1957年 | 2篇 |
1955年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
韩书法 《科技情报开发与经济》2005,15(10):283-284
统计分析的广度、深度和力度决定于分析思路和表述思路,归结于写作思路。提高统计分析的广度、深度和力度,必须在写作思路的培养锻炼上下功夫,达到升华和提高。 相似文献
43.
44.
为了准确计算出镀膜过程中每层膜的折射率,介绍了实时监控过程中确定膜层折射率的2种方法:一种是由实测的透射比光谱直接反算出膜层的折射率;另一种是用最小二乘法的优化算法实时拟合折射率。试验结果表明:在线反算适合单点监控,所得折射率误差小于2%。然而在实际镀膜过程中,由于宽带内膜层参数误差较大,一般大于25%。为此,采用最小二乘法拟合,即在整个宽光谱范围内采集每个波长点的信息,所得结果误差很小,一般都在2%~5%之间,有时可达到10%,在很大程度上提高了实际镀膜时膜厚监控的精度。 相似文献
45.
46.
随着我国加入世贸组织,政治思想工作将面临新的机遇和挑战,因之,我们应从道德规范教育入手,运用法制教育手段,通过学生主体性的发挥,依托校园化氛围开展德育工作。 相似文献
47.
一类混合型微分差分方程的周期解 总被引:1,自引:0,他引:1
利用Fenchel变换,我们推出一类微分差分方程存在周期解等价于某泛函具有临界点,并求出方程具有周期解的充分条件. 相似文献
48.
The traditional chemical industry has become a largely mature industry with many commodity products based on established technologies. Therefore, new product and market opportunities will more likely come from speciality chemicals, and from new functionalities obtained from new processing technologies as well as new microstructure control methodologies. It is a well-known fact that in addition to its molecular structure, the microstructure of a material is key to determining its properties. Controlling structures at the micro- and nano-levels is therefore essential to new discoveries. For this article, we define nanotechnology as the controlled manipulation of nanomaterials with at least one dimension less than 100nm. Nanotechnology is emerging as one of the principal areas of investigation that is integrating chemistry and materials science, and in some cases integrating these with biology to create new and yet undiscovered properties that can be exploited to gain new market opportunities. In this article market opportunities for nanotechnology will be presented from an industrial perspective covering electronic, biomedical, performance materials, and consumer products. Manufacturing technology challenges will be identified, including operations ranging from particle formation, coating, dispersion, to characterization, modeling, and simulation. Finally, a nanotechnology innovation roadmap is proposed wherein the interplay between the development of nanoscale building blocks, product design, process design, and value chain integration is identified. A suggestion is made for an R&D model combining market pull and technology push as a way to quickly exploit the advantages in nanotechnology and translate these into customer benefits. 相似文献
49.
在国内外综合因素的影响下,我国主流意识形态的指导地位存在安全隐患,因此加强意识形态工作,确保意识形态安全是摆在我们面前的一项重大而艰巨的任务。 相似文献
50.
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