全文获取类型
收费全文 | 4907篇 |
免费 | 601篇 |
国内免费 | 189篇 |
专业分类
化学 | 2937篇 |
晶体学 | 432篇 |
力学 | 86篇 |
综合类 | 25篇 |
数学 | 73篇 |
物理学 | 2144篇 |
出版年
2024年 | 5篇 |
2023年 | 39篇 |
2022年 | 73篇 |
2021年 | 105篇 |
2020年 | 152篇 |
2019年 | 131篇 |
2018年 | 165篇 |
2017年 | 155篇 |
2016年 | 294篇 |
2015年 | 176篇 |
2014年 | 193篇 |
2013年 | 789篇 |
2012年 | 211篇 |
2011年 | 224篇 |
2010年 | 187篇 |
2009年 | 273篇 |
2008年 | 252篇 |
2007年 | 327篇 |
2006年 | 264篇 |
2005年 | 240篇 |
2004年 | 188篇 |
2003年 | 170篇 |
2002年 | 142篇 |
2001年 | 127篇 |
2000年 | 106篇 |
1999年 | 118篇 |
1998年 | 96篇 |
1997年 | 49篇 |
1996年 | 66篇 |
1995年 | 51篇 |
1994年 | 45篇 |
1993年 | 32篇 |
1992年 | 30篇 |
1991年 | 19篇 |
1990年 | 32篇 |
1989年 | 14篇 |
1988年 | 26篇 |
1987年 | 13篇 |
1986年 | 16篇 |
1985年 | 12篇 |
1984年 | 20篇 |
1983年 | 7篇 |
1982年 | 13篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1979年 | 10篇 |
1977年 | 4篇 |
1975年 | 6篇 |
1974年 | 3篇 |
1973年 | 7篇 |
排序方式: 共有5697条查询结果,搜索用时 31 毫秒
11.
A two-step swelling procedure was adopted to synthesize mono-dispersed and highly cross-linked poly (St-divinylbenzene) particles
with PSt micro-spheres (1.80 μm in diameter). The PSt micro-spheres were prepared by a dispersion polymerization method and
used as seeds. The effects of monomer concentration, ratio of ethanol to water, swelling reagents, crosslinking reagents,
swelling temperature and agitation speed on particle size were investigated in detail. The morphologies and size distributions
of these micro-spheres were examined by SEM and particle size analysis (PSA). The T
g of the micro-spheres was measured by DSC. The results indicate that the particles (6.20 μm in diameter) exhibit excellent
mono dispersed property and high crosslinking degree when the concentration of the swelling reagent was 25%, the concentration
of the crosslinking reagents was 23%, the swelling temperature was 30°C and the stirring speed was 150 r/min.
__________
Translated from Chinese Journal of Applied Chemistry, 2007, 24(11): 1289–1294 相似文献
12.
We analyse a model for equilibrium configurations of composite systems of nematic liquid crystal with polymer inclusions, in the presence of an external magnetic field. We assume that the system has a periodic structure, and consider the relaxed problem on the unit length constraint of the nematic director field. The relaxation of the Oseen–Frank energy functional is carried out by including bulk as well as surface energy penalty terms, rendering the problem fully non‐linear. We employ two‐scale convergence methods to obtain effective configurations of the system, as the size of the polymeric inclusions tends to zero. We discuss the minimizers of the effective energies for, both, the constrained as well as the unconstrained models. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
13.
T. K. Solovykh 《Journal of Applied Spectroscopy》1997,64(5):654-657
The role of impurity ions in formation of the optical properties of rare-earth orthoferrites is investigated. Optical spectra
of the substituted against unsubstituted orthoferrites are presented. The influence of different isovalent substitutions on
the optical absorption of orthoferrites that are promising for magnetooptics is studied.
Institute of Solid-State and Semiconductor Physics of the Academy of Sciences of Belarus, 17, P. Brovka St., Minsk, 220072,
Belarus. Translated from zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 5, pp. 642–645, September–October, 1997. 相似文献
14.
15.
16.
新疆野生黑加仑与马林果实的营养成分分析 总被引:2,自引:0,他引:2
通过对新疆野生黑加仑和野生马林的脂肪油,8种微量元素,17种氨基酸以及维生素C的含量进行测定得出:黑加仑脂肪油含量为17.9%,马林的脂肪油含量为22.3%,其中,黑加仑脂肪油中,r-亚麻酸的含量为19.02%,而马林中,其含量为9.40%,黑加仑中K,Na,Ca,Cu,Zn,Fe的含量比马林中的含量高,而Mn,Mg元素的含量却比马林含量低;马林的维生素C含量为16.22mg/g,黑加仑的含量为108mg/g,黑加仑的氨基酸的总量为1.63%,马林为1.14%。 相似文献
17.
Tunable properties of light propagation in photonic crystal fibers filled with liquid crystals, called photonic liquid crystal
fibers (PLCFs) are presented. The propagation properties of PLCFs strongly depend on contrast between refractive indices of
the solid core (pure silica glass) and liquid crystals (LCs) filing the holes of the fiber. Due to relatively strong thermo-optical
effect, we can change the refractive index of the LC by changing its temperature. Numerical analysis of light propagation
in PLCF, based on two simulation methods, such as finite difference (FD) and multipole method (MM) is presented. The numerical
results obtained are in good agreement with our earlier experimental results presented elsewhere [1]. 相似文献
18.
The kinetics of reactions occurring at the gas-exposed surfaces of charged mixed ionic electronic conductors (MIECs) are examined
from theoretical first principles. Analysis based on the classical electrochemical potential-transition state theory model
reveals that the nature of the reactions is electrochemical in general. However, the influence of the surface potential on
the reaction rate is opposite for adsorption and incorporation reactions. Two-dimensional finite volume models of an MIEC
as working electrode in a half-cell configuration are presented. The results for a simple, two-step reduction process show
that the effect of the surface potential on the rate of reactions is minimal for incorporation-limited reactions but more
influential for adsorption-limited reactions.
An erratum to this article is available at . 相似文献
19.
Combining layered positional order as smectic order and chirality can generate complex architectures since twist parallel
to the layers is not allowed. This paper will review some new experimental results on different phases resulting from the
competition between smectic positional order and twist orientational order. It concerns the TGBA and the NL*, that is the liquid line phase as well as the SmQ phase. Chiral effects in the isotropic phase will also be discussed. 相似文献
20.
Tunable microlens arrays using polymer network liquid crystal 总被引:1,自引:0,他引:1
A tunable-focus microlens array based on polymer network liquid crystal (PNLC) is demonstrated. The PNLC was prepared using an ultraviolet (UV) light exposure through a patterned photomask. The photocurable monomer in each of the UV exposed spot forms an inhomogeneous centro-symmetrical polymer network which acts as a lens when a homogeneous electric field is applied to the cell. The focal length of the microlens arrays is tunable with the applied voltage. 相似文献