全文获取类型
收费全文 | 30654篇 |
免费 | 160篇 |
国内免费 | 295篇 |
专业分类
化学 | 11681篇 |
晶体学 | 268篇 |
力学 | 1423篇 |
综合类 | 12篇 |
数学 | 9360篇 |
物理学 | 8365篇 |
出版年
2022年 | 73篇 |
2021年 | 79篇 |
2020年 | 72篇 |
2019年 | 60篇 |
2018年 | 1238篇 |
2017年 | 1489篇 |
2016年 | 782篇 |
2015年 | 594篇 |
2014年 | 540篇 |
2013年 | 794篇 |
2012年 | 3240篇 |
2011年 | 2444篇 |
2010年 | 1906篇 |
2009年 | 1614篇 |
2008年 | 658篇 |
2007年 | 713篇 |
2006年 | 699篇 |
2005年 | 4511篇 |
2004年 | 3967篇 |
2003年 | 2342篇 |
2002年 | 527篇 |
2001年 | 305篇 |
2000年 | 112篇 |
1999年 | 179篇 |
1998年 | 126篇 |
1997年 | 89篇 |
1996年 | 68篇 |
1995年 | 51篇 |
1994年 | 52篇 |
1993年 | 35篇 |
1992年 | 179篇 |
1991年 | 170篇 |
1990年 | 144篇 |
1989年 | 112篇 |
1988年 | 110篇 |
1987年 | 63篇 |
1986年 | 57篇 |
1985年 | 53篇 |
1984年 | 35篇 |
1983年 | 36篇 |
1982年 | 38篇 |
1981年 | 36篇 |
1976年 | 81篇 |
1975年 | 40篇 |
1974年 | 42篇 |
1973年 | 50篇 |
1972年 | 40篇 |
1969年 | 38篇 |
1968年 | 35篇 |
1966年 | 37篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Mohammad A. Khalilzadeh Soo Young Kim Ho Won Jang Rafael Luque Rajender S. Varma Richard A. Venditti Mohammadreza Shokouhimehr 《Materials Today Chemistry》2022
The requirement of green and sustainable materials to prepare heterogeneous catalysts has intensified for practical reasons over the past few decades. Carbohydrates are possibly the most plentiful and renewable organic materials in nature with inimitable physiochemical properties, plausible low-cost and large-scale production, and sustainability features could be exploited in the generation of nanostructured heterogeneous catalysts. This review article outlines the organic transformations catalyzed by diverse carbohydrate-based nanostructured catalysts in greener and environmentally friendly processes. Selected examples are highlighted for a variety of organic reactions exploiting the proposed catalysts’ reactivity and reusability, and interactions with the intrinsic nature of the applied carbohydrate supports; advantages and speculated challenges of the introduced catalysts are deliberated as well. 相似文献
2.
BIT Numerical Mathematics - In this article we address the problem of minimizing a strictly convex quadratic function using a novel iterative method. The new algorithm is based on the well-known... 相似文献
3.
4.
Nonlinear Dynamics - Introduction of stiffness nonlinearities to broaden the frequency bandwidth of vibratory energy harvesters has the adverse influence of complicating the response behavior of... 相似文献
5.
Rafael López 《Annals of Global Analysis and Geometry》1997,15(3):201-210
In this paper we study constant mean curvature compact surfaces with two Jordan curves in parallel planes as boundary and we investigate the point at which the surface inherits the symmetries of its boundary. 相似文献
6.
Julia K Pruns Jens-Peter Vietzke Manfred Strassner Claudius Rapp Ulrich Hintze Wilfried A K?nig 《Rapid communications in mass spectrometry : RCM》2002,16(3):208-211
A new solvent-free sample preparation method using silver trifluoroacetate (AgTFA) was developed for the analysis of low molecular weight paraffins and microcrystalline waxes by laser desorption/ionization time-of-flight mass spectrometry (LDI-TOFMS). Experiments show that spectral quality can be enhanced by dispersing AgTFA directly in liquid paraffins without the use of additional solvents. This preparation mixture is applied directly to the MALDI probe. Solid waxes could be examined by melting prior to analysis. The method also provides sufficiently reproducible spectra that peak area ratios between mono- and bicyclic alkane peaks indicated variations in the cycloalkane content of paraffin samples. Dehydrogenation of hydrocarbons observed during the desorption/ionization process was studied by analysis of alkane standards. 相似文献
7.
The versatile behavior of a trihydrazidophosphoradamantane allowing the synthesis of a variety of neutral, mono- or di-cationic water-soluble molecules of potential interest for biphasic catalysis is reported. 相似文献
8.
In this paper we construct an example of a word metric on an infinite cyclic subgroup. This example shows that subexponential
distortion does not obstruct non-trivial growth of connected radii. This answers a question of Gromov [6]. The constructed
metric has other pathological properies. Specifically, its asymptotic cone depends on the choice of ultrafilter and scaling
sequence.
The work has been partially supported by the Swiss National Science Foundation. 相似文献
9.
We build a metric space which is homeomorphic to a Cantor set but cannot be realized as the attractor of an iterated function system. We give also an example of a Cantor set K in R3 such that every homeomorphism f of R3 which preserves K coincides with the identity on K. 相似文献
10.
Milan Medved? 《Journal of Mathematical Analysis and Applications》2002,267(2):643-650
A criterion for the nonexplosion of solutions to semilinear evolution equations on Banach spaces is proved. The result is obtained by applying a modification of the Bihari type inequality to the case of a weakly singular nonlinear integral inequality. 相似文献