全文获取类型
收费全文 | 20885篇 |
免费 | 3799篇 |
国内免费 | 3362篇 |
专业分类
化学 | 16071篇 |
晶体学 | 481篇 |
力学 | 1091篇 |
综合类 | 297篇 |
数学 | 2236篇 |
物理学 | 7870篇 |
出版年
2024年 | 34篇 |
2023年 | 306篇 |
2022年 | 471篇 |
2021年 | 606篇 |
2020年 | 740篇 |
2019年 | 853篇 |
2018年 | 661篇 |
2017年 | 678篇 |
2016年 | 921篇 |
2015年 | 1007篇 |
2014年 | 1137篇 |
2013年 | 1526篇 |
2012年 | 1967篇 |
2011年 | 1930篇 |
2010年 | 1550篇 |
2009年 | 1527篇 |
2008年 | 1710篇 |
2007年 | 1445篇 |
2006年 | 1453篇 |
2005年 | 1313篇 |
2004年 | 1061篇 |
2003年 | 829篇 |
2002年 | 878篇 |
2001年 | 691篇 |
2000年 | 549篇 |
1999年 | 438篇 |
1998年 | 277篇 |
1997年 | 203篇 |
1996年 | 188篇 |
1995年 | 164篇 |
1994年 | 173篇 |
1993年 | 134篇 |
1992年 | 81篇 |
1991年 | 101篇 |
1990年 | 63篇 |
1989年 | 51篇 |
1988年 | 56篇 |
1987年 | 28篇 |
1986年 | 35篇 |
1985年 | 47篇 |
1984年 | 20篇 |
1983年 | 20篇 |
1982年 | 13篇 |
1981年 | 16篇 |
1980年 | 11篇 |
1979年 | 12篇 |
1978年 | 7篇 |
1977年 | 11篇 |
1975年 | 11篇 |
1969年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
881.
882.
讨论了完备化Witt代数的三类非有限阶化子代数的不可约非权模的实现,并利用它们的表示得到一些有趣的组合恒等式. 相似文献
883.
利用“每课一题”这个教学环节从已有知识中提取基本原理,并应用于新知识的学习;提取学生的问题编制习题,让学生暴露产生问题的根源并从根本上解决。探讨了每课一题的必要性及其基本类型。 相似文献
884.
ZOU XiaoChuan CHEN ShaoCheng REN YanRong SHI KaiYun LI Jun & FU XiangKai 《中国科学:化学(英文版)》2012,(11):2397-2407
Chiral Mn Ⅲ (salen) (Jacobsen’s catalyst) was axially immobilized onto a new type of organic polymer-inorganic hybrid materialzirconium poly(styrene-isopropenyl phosphonate)-phosphate(ZPS-IPPA) with different linkage lengths and evaluated as catalysts for the epoxidation of unfunctionalized olefins. The results demonstrated that the prepared catalysts exhibited moderate to good activity and enantioselectivity in the asymmetric epoxidation of unfunctionalized olefins. Furthermore, the immobilized catalysts were relatively stable and could be conveniently separated from the reaction system by simple precipitation in hexane. Moreover, higher enantioselectivity was obtained with catalyst 2c than that of homogeneous counterpart catalyzed even after eight times. The excellent recycling of the catalyst was attributed to its structure feature of ZPS-IPPA which is different from either pure polystyrene or pure zirconium phosphates. 相似文献
885.
886.
887.
Residual determination and risk assessment of buprofezin in plum (Prunus domestica) grown in open‐field conditions following the application of three different formulations
下载免费PDF全文
![点击此处可从《Biomedical chromatography : BMC》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Md. Humayun Kabir A.M. Abd El‐Aty Sung‐Woo Kim Han Sol Lee Md. Musfiqur Rahman Young‐Jun Lee Hyung Suk Chung Truong Lieu Jeong‐Heui Choi Ho‐Chul Shin Geon‐Jae Im Su Myeong Hong Jae‐Han Shim 《Biomedical chromatography : BMC》2016,30(11):1721-1727
This study was conducted to characterize the residual level and perform a risk assessment on buprofezin formulated as an emulsifiable concentrate, wettable powder, and suspension concentrate over various treatment schedules in plum (Prunus domestica). The samples were extracted with an AOAC quick, easy, cheap, effective, rugged, and safe, ‘QuEChERS’, method after major modifications. As intrinsic interferences were observed in blank plum samples following dispersive‐solid phase extraction (consisting of primary secondary amine and C18 sorbents), amino cartridges were used for solid‐phase extraction. Analysis was carried out using liquid chromatography with diode array detection and confirmed by liquid chromatography–tandem mass spectrometry. The method showed excellent linearity with determination coefficient (R2 = 1) and satisfactory recoveries (at two spiking levels, 0.5 and 2.5 mg/kg) between 90.98 and 94.74% with relative standard deviation (RSD) ≤8%. The limit of quantification (0.05 mg/kg) was considerably lower than the maximum residue limit (2 mg/kg) set by the Codex Alimentarius. Absolute residue levels for emulsifiable concentrates were highest, perhaps owing to the dilution rate and adjuvant. Notably, all formulation residues were lower than the maximum residue limit, and safety data proved that the fruits are safe for consumers. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
888.
正The Chang'E-3(CE-3)mission began with a smooth countdown and flawless launch on the Long March 3B rocket from the Xichang satellite launch center at 01:30 CST on December 2,2013.It landed on the northeastern Imbrium basin(340.49°E,44.12°N)at 21:11 CST on December 14,2013,and the Yutu rover was deployed from the lander the next morning at 04:35.The lander was equipped with a number of remote-sensing 相似文献
889.
Shin-ichi Kondo Kimihiro Endo Jun Iioka Keisuke Sato Yuka Matsuta 《Tetrahedron letters》2017,58(43):4115-4118
We have successfully prepared 5-(2-phenylethynyl)isophathalilc acid as a signaling unit and the corresponding derivatives for an anion receptor 2 and a barbiturate receptor 4. Receptor 2 showed characteristic UV–vis changes and dramatic fluorescence quenching upon the addition of anions and receptor 4 showed UV–vis and an OFF-ON fluorescence changes upon the addition of dibutylbarbituric acid based on the diphenylethyne moiety. 相似文献
890.