全文获取类型
收费全文 | 14312篇 |
免费 | 2427篇 |
国内免费 | 1308篇 |
专业分类
化学 | 11516篇 |
晶体学 | 487篇 |
力学 | 1471篇 |
综合类 | 59篇 |
数学 | 400篇 |
物理学 | 4114篇 |
出版年
2024年 | 36篇 |
2023年 | 184篇 |
2022年 | 360篇 |
2021年 | 498篇 |
2020年 | 895篇 |
2019年 | 620篇 |
2018年 | 581篇 |
2017年 | 547篇 |
2016年 | 880篇 |
2015年 | 878篇 |
2014年 | 920篇 |
2013年 | 1221篇 |
2012年 | 818篇 |
2011年 | 972篇 |
2010年 | 855篇 |
2009年 | 836篇 |
2008年 | 927篇 |
2007年 | 917篇 |
2006年 | 842篇 |
2005年 | 645篇 |
2004年 | 645篇 |
2003年 | 637篇 |
2002年 | 422篇 |
2001年 | 361篇 |
2000年 | 271篇 |
1999年 | 203篇 |
1998年 | 184篇 |
1997年 | 154篇 |
1996年 | 128篇 |
1995年 | 80篇 |
1994年 | 88篇 |
1993年 | 67篇 |
1992年 | 63篇 |
1991年 | 51篇 |
1990年 | 43篇 |
1989年 | 36篇 |
1988年 | 22篇 |
1987年 | 23篇 |
1986年 | 32篇 |
1985年 | 18篇 |
1984年 | 18篇 |
1983年 | 19篇 |
1982年 | 17篇 |
1981年 | 9篇 |
1980年 | 2篇 |
1979年 | 7篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1971年 | 7篇 |
1957年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 22 毫秒
91.
92.
A. Konjhodzic A. Adamczyk F. Vagizov Z. Hasan E E. Alp W. Sturhahn Jiyong Zhao J J. Carroll 《Hyperfine Interactions》2006,170(1-3):83-89
With the decrease in size of devices, rapid characterization of nano-devices is an inevitable necessity. It is shown that Mössbauer spectroscopy using synchrotron radiation from the advanced photon source provides such a tool of investigation. Results are presented and compared for conventional Mössbauer and Nuclear Forward Scattering for 151Eu-doped magnesium sulfide as an example, especially at low concentrations. 相似文献
93.
Leszek Wachowski Antoni Grodzicki Piotr Piszczek Monika Richert Magdalena Hofman 《Reaction Kinetics and Catalysis Letters》2007,91(1):93-99
Hydrogenation of styrene has been applied as a test reaction to study the catalytic activity of TiO2 deposited by the CVD (chemical vapour deposition) method on the surface of a carbonaceous material enriched in nitrogen (CN). 相似文献
94.
95.
Jin Kyu Park Dong Hun Lee Bok Ju Song Jae Buem Oh Hwan Kyu Kim 《Journal of polymer science. Part A, Polymer chemistry》2006,44(3):1326-1342
We have designed and synthesized novel perfluorinated polyimides with 3D controlled structure. At first, we successfully developed the new synthetic routes to diamines with pendant bulky perfluorinated aromatic units in a multi‐step synthetic procedure. Novel perfluorinated polyimides were prepared in a two‐step reaction in N‐methyl‐2‐pyrrolidinone (NMP) solution: The first step was for the synthesis of polyamic acids (PAAs) and the second reaction was for the imidization of PAA. The polymer yield was over 89% and the inherent viscosity of PAAs was in the range of 0.24–0.36 dL/g. The thin films were prepared by spin‐coating the PAA solution in NMP onto various substrates such as a Si wafer or a KBr pellet, dried at 80 °C and further cured at 230 °C. The resultant polyimides are thermally stable over 400 °C. The refractive index and birefringence of the resultant polyimides are 1.5858–1.6452 and 0.01–0.005, respectively. The refractive index of polyimide decreases with increasing the fluorine content. The copolymerization and the ether linkages into the backbone reduce the birefringence of polyimides. Surprisingly, the pendant ether linkage is not a crucial factor in reducing the polyimide birefringence. Their birefringence is comparatively very low, compared with that of previous polyimides. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1326–1342, 2006 相似文献
96.
Gurkan Hizal Umit Tunca Sermin Aras Humeyra Mert 《Journal of polymer science. Part A, Polymer chemistry》2006,44(1):77-87
Copper‐catalyzed controlled/living radical polymerization (LRP) of styrene (St) was conducted using the silica gel‐supported CuCl2/N,N,N′,N′,N″‐pentamethyldiethylenetriamine (SG‐CuCl2/PMDETA) complex as catalyst at 110 °C in the presence of a definite amount of air. This novel approach is based on in situ generation and regeneration of Cu(I) via electron transfer reaction between phenols and Cu(II). Sodium phenoxide or p‐methoxyphenol was used as a reducing agent of Cu(II) complexes in LRP. The number–average molecular weight, Mn,GPC, increases linearly with monomer conversion and agrees well with the theoretical values up to 85% conversion The molecular weight distribution, Mw/Mn, decreases as the conversion increases and reaches values below 1.2. The catalyst was recovered in aerobic condition and reused in copper‐catalyzed LRP of St. For the second run, the number–average molecular weights increased with monomer conversion and the polydispersities decreased as the polymerization proceeded and reached to the value <1.3 at 81% conversion. The recycled catalyst retained 90% of its original activity in the subsequent polymerization. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 77–87, 2006 相似文献
97.
In this paper, a model of the motional nonlinear heterogeneous catalysis process is discussed using the characteristic line method, the analytical results of elution profile are obtained and the formula which determines the parameters of reaction rate and adsorption isotherm through the motional measurement data under the nonlinear condition is given. 相似文献
98.
Summary Equilibrium equations and stability conditions for the simple deformable elastic body are derived by means of considering
a minimum of the static energy principle. The energy is supposed to be sum of the volume (elastic) and the surface terms.
The ability to change relative positions of different material particles is taken into account, and appropriate natural definitions
of the first and second variations of the energy are introduced and calculated explicitly. Considering the case of negligible
magnitude of the surface tension, we establish that an equilibrium state of a nonhydrostatically stressed simple elastic body
(of any physically reasonable elastic energy potential and of any symmetry) possessing any small smooth part of free surface
is always unstable with respect to relative transfer of the material particles along the surface. Surface tension suppresses
the mentioned instability with respect to sufficiently short disturbances of the boundary surface and thus can probably provide
local smoothness of the equilibrium shape of the crystal. We derive explicit formulas for critical wavelength for the simplest
models of the internal and surface energies and for the simplest equilibrium configurations. We also formulate the simplest
problem of mathematical physics, revealing peculiarities and difficulties of the problem of equilibrium shape of elastic crystals,
and discuss possible manifestations of the above-mentioned instability in the problems of crystal growth, materials science,
fracture, physical chemistry, and low-temperature physics. 相似文献
99.
100.
负载型双金属簇催化剂的多相一氧化碳加氢反应性能索全伶,李晔(内蒙古工业大学化学工程系,呼和浩特010062)殷元骐,金道森(中国科学院兰州化学物理研究所,兰州730000)关键词一氧化碳加氢,多相催化,双金属簇催化剂,钾效应。1.引言异核金属羰基簇作... 相似文献