全文获取类型
收费全文 | 114207篇 |
免费 | 6191篇 |
国内免费 | 5310篇 |
专业分类
化学 | 52132篇 |
晶体学 | 1212篇 |
力学 | 8793篇 |
综合类 | 384篇 |
数学 | 35857篇 |
物理学 | 27330篇 |
出版年
2024年 | 109篇 |
2023年 | 705篇 |
2022年 | 1178篇 |
2021年 | 1314篇 |
2020年 | 1486篇 |
2019年 | 1572篇 |
2018年 | 11403篇 |
2017年 | 11158篇 |
2016年 | 7682篇 |
2015年 | 2673篇 |
2014年 | 2464篇 |
2013年 | 2926篇 |
2012年 | 6992篇 |
2011年 | 13651篇 |
2010年 | 7916篇 |
2009年 | 8096篇 |
2008年 | 8950篇 |
2007年 | 10801篇 |
2006年 | 2282篇 |
2005年 | 3069篇 |
2004年 | 2944篇 |
2003年 | 3262篇 |
2002年 | 2470篇 |
2001年 | 1506篇 |
2000年 | 1162篇 |
1999年 | 983篇 |
1998年 | 762篇 |
1997年 | 661篇 |
1996年 | 674篇 |
1995年 | 528篇 |
1994年 | 396篇 |
1993年 | 360篇 |
1992年 | 336篇 |
1991年 | 355篇 |
1990年 | 277篇 |
1989年 | 238篇 |
1988年 | 200篇 |
1987年 | 166篇 |
1986年 | 180篇 |
1985年 | 144篇 |
1984年 | 120篇 |
1983年 | 95篇 |
1982年 | 83篇 |
1981年 | 75篇 |
1980年 | 80篇 |
1979年 | 68篇 |
1978年 | 62篇 |
1977年 | 44篇 |
1973年 | 52篇 |
1914年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Gang Wang Xiulin Zhu Zhenping Cheng Jian Zhu 《Journal of polymer science. Part A, Polymer chemistry》2006,44(9):2912-2921
A series of (di)picolinic acids and their derivates are investigated as novel complexing tridentate or bidentate ligands in the iron‐mediated reverse atom transfer radical polymerization of methyl methacrylate in N,N‐dimethylformamide at 100 °C with 2,2′‐azobisisobutyrontrile as an initiator. The polymerization rates and polydispersity indices (1.32–1.8) of the resulting polymers are dependent on the structures of the ligands employed. Different iron complexes may be involved in iron‐mediated reverse atom transfer radical polymerization, depending on the type of acid used. 1H NMR spectroscopy has been used to study the structure of the resulting polymers. Chain‐extension reactions have been performed to further confirm the living nature of this catalytic system. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2912–2921, 2006 相似文献
2.
3.
本文对特征P的基域F引入适当的Galois群T,讨论p置换模的Green环的Conlon比析在Galois群T作用下的动态,证明了在T作用下p置换模的Green环的不动点集重合于置换模的Green环。 相似文献
4.
5.
6.
A lithium(I) coordination polymer has been formed from LiClO4 and the 2,2′‐bipyrimidine (bpym) ligand in which each square pyramidal lithium(I) atom is coordinated in the basal plane by four nitrogen donor atoms derived from two bpym ligands and one water molecule at the apical position. These are connected into a layer structure via hydrogen‐bonding interactions involving the perchlorate anions. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
7.
Christiane Albrecht 《Analytical and bioanalytical chemistry》2008,390(5):1223-1224
8.
9.
Chengzhi Qi Mingyang Wang Qihu Qian Jianjie Chen 《Moscow University Mechanics Bulletin》2008,63(5):113-121
The formation mechanisms for the structural hierarchy in geological media are discussed. It is shown that the formation of such a hierarchy is caused by certain external and internal circumstances. The first ones consist in the fact that, because of external actions, the Earth’s poles continuously execute the translational and rotational motions responsible for a regular structure of rock fracture and for the appearance of the scale factor √2. The second ones consist in the fact that, under the action of many random factors and because of external actions, during the formation of geological media there appear dissipative structures and, hence, some self-similar fractal structures are formed. 相似文献
10.
Howard Robinson 《Acta Analytica》2005,20(3):7-10
Nicholas Nathan tries to resist the current version of the causal argument for sense-data in two ways. First he suggests that,
on what he considers to be the correct re-construction of the argument, it equivocates on the sense of proximate cause. Second
he defends a form of disjunctivism, by claiming that there might be an extra mechanism involved in producing veridical hallucination,
that is not present in perception. I argue that Nathan’s reconstruction of the argument is not the appropriate one, and that,
properly interpreted, the argument does not equivocate on proximate cause. Furthermore, I claim that his postulation of a
modified mechanism for hallucinations is implausibly ad hoc. 相似文献