全文获取类型
收费全文 | 81732篇 |
免费 | 428篇 |
国内免费 | 397篇 |
专业分类
化学 | 26807篇 |
晶体学 | 835篇 |
力学 | 6840篇 |
数学 | 32403篇 |
物理学 | 15672篇 |
出版年
2020年 | 65篇 |
2019年 | 57篇 |
2018年 | 10462篇 |
2017年 | 10289篇 |
2016年 | 6144篇 |
2015年 | 913篇 |
2014年 | 370篇 |
2013年 | 523篇 |
2012年 | 4012篇 |
2011年 | 10749篇 |
2010年 | 5728篇 |
2009年 | 6127篇 |
2008年 | 6835篇 |
2007年 | 9009篇 |
2006年 | 478篇 |
2005年 | 1560篇 |
2004年 | 1706篇 |
2003年 | 2128篇 |
2002年 | 1158篇 |
2001年 | 295篇 |
2000年 | 342篇 |
1999年 | 187篇 |
1998年 | 231篇 |
1997年 | 186篇 |
1996年 | 259篇 |
1995年 | 158篇 |
1994年 | 123篇 |
1993年 | 126篇 |
1992年 | 90篇 |
1991年 | 102篇 |
1990年 | 97篇 |
1989年 | 88篇 |
1988年 | 85篇 |
1987年 | 75篇 |
1986年 | 79篇 |
1985年 | 83篇 |
1984年 | 91篇 |
1983年 | 72篇 |
1982年 | 84篇 |
1981年 | 73篇 |
1980年 | 75篇 |
1979年 | 66篇 |
1978年 | 62篇 |
1977年 | 41篇 |
1973年 | 42篇 |
1914年 | 45篇 |
1913年 | 40篇 |
1912年 | 40篇 |
1909年 | 48篇 |
1908年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
Gregory S. Constable Alan J. Lesser E. Bryan Coughlin 《Journal of Polymer Science.Polymer Physics》2003,41(12):1323-1333
An in situ ultrasonic spectroscopy technique was used to study the ring‐opening metathesis polymerization of dicyclopentadiene catalyzed by bis(tricyclohexylphosphine)benzylidene ruthenium dichloride. A reaction cell employing a flexible poly(ethylene terephthalate) window for pulse echo ultrasonic spectroscopy was used to monitor the polymerization. The changes in the density, wave speed, acoustic modulus, and attenuation were all simultaneously monitored. In comparison with Fourier transform infrared (FTIR) spectroscopy data, the changes in the density, velocity, and modulus only accurately measured the rate constant for the metathesis of the cyclopentyl unsaturation. The ultrasonic values were within 6% of the values determined by FTIR. The activation energy for metathesis of the cyclopentyl unsaturation was 84 kJ mol?1, following first‐order kinetics. Rate constants for the polymerization of the norbornyl unsaturation could not be determined by ultrasound. The gel point, vitrification, and qualitative information about the reaction rate could be determined from the change in the attenuation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1323–1333, 2003 相似文献
5.
Christiane Albrecht 《Analytical and bioanalytical chemistry》2008,390(5):1223-1224
6.
7.
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
8.
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
9.
10.
Khaled A. Aamer Gregory N. Tew 《Journal of polymer science. Part A, Polymer chemistry》2007,45(6):1109-1121
Supramolecular block‐random copolymers containing [Ir(terpy)2]3+ in the side chain were synthesized via postfunctionalization of a P(S‐b‐ACterpy) block copolymer. Absorbance and emission spectra compared to a model compound show that the polymer backbone has a minor effect on the polymer absorbance but produces a larger shift for the phosphorescence signals to higher wavelength. Dynamic light scattering of the metal complex containing copolymer studied in various solvents showed monomodal aggregation with decreasing aggregate size as the solvent dielectric constant increased. The copolymer precursor P(S‐b‐ACterpy) shows multimodal aggregation in different solvents with the major population consisting of single chains. This difference in behavior between the two polymers is attributed to the electrolytic nature of the complex and the amphiphilicity induced by the charged metal complex. Supramolecular copolymers like these will continue to have interesting self‐organizational properties and may find applications in multicomponent systems for photoinduced charge separation processes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1109–1121, 2007 相似文献