全文获取类型
收费全文 | 33089篇 |
免费 | 3788篇 |
国内免费 | 2994篇 |
专业分类
化学 | 16060篇 |
晶体学 | 280篇 |
力学 | 1337篇 |
综合类 | 187篇 |
数学 | 2309篇 |
物理学 | 8302篇 |
综合类 | 11396篇 |
出版年
2024年 | 82篇 |
2023年 | 523篇 |
2022年 | 785篇 |
2021年 | 975篇 |
2020年 | 985篇 |
2019年 | 913篇 |
2018年 | 802篇 |
2017年 | 833篇 |
2016年 | 1137篇 |
2015年 | 1269篇 |
2014年 | 1498篇 |
2013年 | 1972篇 |
2012年 | 2221篇 |
2011年 | 2382篇 |
2010年 | 1654篇 |
2009年 | 1677篇 |
2008年 | 1924篇 |
2007年 | 1808篇 |
2006年 | 1620篇 |
2005年 | 1330篇 |
2004年 | 1083篇 |
2003年 | 942篇 |
2002年 | 926篇 |
2001年 | 760篇 |
2000年 | 731篇 |
1999年 | 1049篇 |
1998年 | 927篇 |
1997年 | 900篇 |
1996年 | 995篇 |
1995年 | 827篇 |
1994年 | 829篇 |
1993年 | 578篇 |
1992年 | 548篇 |
1991年 | 522篇 |
1990年 | 388篇 |
1989年 | 357篇 |
1988年 | 319篇 |
1987年 | 224篇 |
1986年 | 171篇 |
1985年 | 99篇 |
1984年 | 69篇 |
1983年 | 53篇 |
1982年 | 40篇 |
1981年 | 28篇 |
1980年 | 32篇 |
1979年 | 18篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1975年 | 7篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
21.
22.
Understanding and control of the surface properties such as molecular orientations are of great importance in numerous applications of ionic liquids. However, there remain discrepancies among the previous experimental and theoretical studies on the surface orientation and structures of room temperature ionic liquids(RTIL) systems. In this article, the orientation of 1-butyl-3-methylimidazolium([bmin]) cation at the air/liquid interface of a characteristic RTIL, 1-butyl-3-methylimidazolium hexafluorophosphate([bmim][PF6]), was investigated by the sum frequency generation vibrational spectroscopy(SFG-VS). Detailed polarization and experimental configuration analyses of the SFG-VS spectra showed the possibility of a small spectral splitting in the CH3 symmetric stretching region, which can be further attributed to the probable existence of multiple orientations for the interfacial [bmim] cations. In addition, the(N)–CH3 vibrations were absent, ruling out the prediction by several recent molecular dynamics simulations which state that portions of the [bmim] cations orient with a standing-up(N)–CH3 group at the ionic liquid surface. Hence, new realistic theoretical models have to be developed to reflect the complex nature of the ionic liquid surface. 相似文献
23.
24.
A rapid method had been used for comparative study on Artemisia halodendron Turcz. and its two related plants by gas phase-mass spectrometry (GC-MS). The comparison of the volatile oils obtained in three plants by GC-MS were similar in 20 compositions. However, n-Hexadecanoic acid (10.40%), Biphenyl (7.867%) and 9,12-Octadecadienoic acid (7.25%) were the predominant in the volatile oils of A. halodendron Turcz., whereas these constituents did not exist in the other two plants. And the study investigated the effect of three plants against CCl4-induced hepatotoxicity in mice. 70% ethanol extracts of A. halodendron Turcz. showed weaker protective effect than the other two plants. It suggested that they provide a basis for the identification of the A. halodendron Turcz. from the other two plants and the ethanol extract from three plants exerted a protecting effect against hepatotoxicity. 相似文献
25.
26.
27.
Here, we report a new strategy for rapid synthesis of branched peptide by side-chain hydrazide ligation at Asn. The hydrazide was converted to thioester at Asn side chain by NaNO2 and thiol reagent, and sequential ligation with an N-terminus Cys-peptide efficiently afforded the branched peptide. A branched cyclic peptide was successfully synthesized by side-chain ligation with a two-Cys-peptide and formation of a disulfide bond. This approach provides a new way for expeditious synthesis of branched peptides and facilitates the design of neopeptides as functional bio-mimics. 相似文献
28.
LuJian-ke 《武汉大学学报:自然科学英文版》2004,9(1):1-5
The homogeneous quadratic Riemann boundary value problem (1) with Hoelder continuous coefficients for the normal case was considered by the author in 1997. But the solutions obtained there are incomplete. Here its general method of solution is obtained. 相似文献
29.
本文依据大学生生理、心理的阶段特征,通过变换组织教法以及增强学生主体、教师主导的双边作用,分析排球课的项目特点。使技能学习和人格发展相结合,培养身心健康发展的大学生。 相似文献
30.
陆选荣 《曲靖师范学院学报》2003,22(2):91-93
“强规强序”型内部管理体制深刻地制约着师范教育品质的进一步提升;主动调整管理策略,在管理中注入“人关怀”意识是变革教育模式、提升教育品质的重要举措。具体讲,可从四个方面实现突破:把尊重师生的个性差异作为制定管理规范的基本准则;把激发师生的个体潜能作为谋划管理策略的最终目标;把师生参与管理作为支持内部管理变革的主要方法;把营造宽松、和谐的人际氛围作为内部管理的激活措施。 相似文献