全文获取类型
收费全文 | 19355篇 |
免费 | 3414篇 |
国内免费 | 4896篇 |
专业分类
化学 | 14712篇 |
晶体学 | 549篇 |
力学 | 1270篇 |
综合类 | 604篇 |
数学 | 2700篇 |
物理学 | 7830篇 |
出版年
2024年 | 34篇 |
2023年 | 259篇 |
2022年 | 598篇 |
2021年 | 602篇 |
2020年 | 649篇 |
2019年 | 631篇 |
2018年 | 549篇 |
2017年 | 712篇 |
2016年 | 800篇 |
2015年 | 878篇 |
2014年 | 1174篇 |
2013年 | 1488篇 |
2012年 | 1640篇 |
2011年 | 1761篇 |
2010年 | 1441篇 |
2009年 | 1463篇 |
2008年 | 1673篇 |
2007年 | 1429篇 |
2006年 | 1345篇 |
2005年 | 1177篇 |
2004年 | 984篇 |
2003年 | 794篇 |
2002年 | 879篇 |
2001年 | 796篇 |
2000年 | 739篇 |
1999年 | 517篇 |
1998年 | 300篇 |
1997年 | 210篇 |
1996年 | 247篇 |
1995年 | 208篇 |
1994年 | 211篇 |
1993年 | 209篇 |
1992年 | 202篇 |
1991年 | 142篇 |
1990年 | 150篇 |
1989年 | 134篇 |
1988年 | 111篇 |
1987年 | 92篇 |
1986年 | 70篇 |
1985年 | 62篇 |
1984年 | 40篇 |
1983年 | 41篇 |
1982年 | 20篇 |
1981年 | 27篇 |
1980年 | 24篇 |
1979年 | 20篇 |
1959年 | 14篇 |
1958年 | 11篇 |
1957年 | 15篇 |
1956年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Briana L. Simms Nan Ji Indika Chandrasiri Mohammad Farid Zia Chinwe S. Udemgba Ravinder Kaur Jared H. Delcamp Alex Flynt Chalet Tan Davita L. Watkins 《Journal of polymer science. Part A, Polymer chemistry》2021,59(19):2177-2192
Here, we demonstrate the applicability of self-assembling linear-dendritic block copolymers (LDBCs) and their nanoaggregates possessing varied surfaces as therapeutic nanocarriers. These LDBCs are comprised of a hydrophobic, linear polyester chemically coupled to a hydrophilic dendron polyamidoamine (PAMAM)—the latter of which acts as the surface of the self-assembled nanoaggregate in aqueous media. To better understand how surface charge density affects the overall operability of these nanomaterials, we modified the nanoaggregate surface to yield cationic (NH3+), neutral (OH), and anionic (COO−) surfaces. The effect of these modifications on the physicochemical properties (i.e., size, morphology, and surface charge density), colloidal stability, and cellular uptake mechanism of the polymeric nanocarrier were investigated. This comparative study demonstrates the viability of nanoaggregates formed from PDLLA-PAMAM LDBCs to serve as nanocarriers for applications in drug delivery. 相似文献
12.
A new asymmetric Salamo‐based ligand H2L was synthesized using 3‐tert‐butyl‐salicylaldehyde and 6‐methoxy‐2‐[O‐(1‐ethyloxyamide)]‐oxime‐1‐phenol. By adjusting the ratio of the ligand H2L and Cu (II), Co (II), and Ni (II) ions, mononuclear, dinuclear, and trinuclear transition metal (II) complexes, [Cu(L)], [{Co(L)}2], and [{Ni(L)(CH3COO)(CH3CH2OH)}2Ni] with the ligand H2L possessing completely different coordination modes were obtained, respectively. The optical spectra of ligand H2L and its Cu (II), Co (II) and Ni (II) complexes were investigated. The Cu (II) complex is a mononuclear structure, and the Cu (II) atom is tetracoordinated to form a planar quadrilateral structure. The Co (II) complex is dinuclear, and the two Co (II) atoms are pentacoordinated and have coordination geometries of distorted triangular bipyramid. The Ni (II) complex is a trinuclear structure, and the terminal and central Ni (II) atoms are all hexacoordinated, forming distorted octahedral geometries. Furthermore, optical properties including UV–Vis, IR, and fluorescence of the Cu (II), Co (II), and Ni (II) complexes were investigated. Finally, the antibacterial activities of the Cu (II), Co (II), and Ni (II) complexes were explored. According to the experimental results, the inhibitory effect was found to be enhanced with increasing concentrations of the Cu (II), Co (II), and Ni (II) complexes. 相似文献
13.
14.
ZHAO Shan-Rong CHEN Kai-Xian JIANG Hua-Liang WANG Qin-Mi JI Ru-YunShanghai Institute of Materia Medica Chinese Academy of Sciences Shanghai China 《中国化学》1997,15(1):84-89
We have used quantum mechanical method to study the transition states(TSs) of uridine phosphorolysis reaction. Comparing the four different reaction pathways and the five transition states obtained, we conclude that enzymatic uridine phosphorolysis takes place mainly according to acid-catalyzed SN2 mechanism. The proposed reaction pathway is consistent with many experimental results. 相似文献
15.
16.
17.
浅析二阶齐次线性变系数微分方程的一个可积类型 总被引:1,自引:0,他引:1
姬志飞 《应用数学与计算数学学报》2006,20(1):125-128
本文讨论了二阶齐次线性变系数微分方程的特殊形式,给出了这种微分方程的一个可积类型. 相似文献
18.
19.
新生MnO2对酸性媒介黑T的吸附 总被引:4,自引:0,他引:4
以化学法合成的新生MnO2为吸附剂,对水中酸性媒介黑T(染料之一)进行了吸附脱色研究,并探讨了影响吸附的因素。结果表明,酸性媒介黑T的脱色率达95%。且PH是影响染料脱色的主要因素。 相似文献
20.