全文获取类型
收费全文 | 16567篇 |
免费 | 391篇 |
国内免费 | 96篇 |
专业分类
化学 | 9593篇 |
晶体学 | 97篇 |
力学 | 553篇 |
数学 | 2450篇 |
物理学 | 4361篇 |
出版年
2022年 | 82篇 |
2021年 | 158篇 |
2020年 | 223篇 |
2019年 | 163篇 |
2018年 | 179篇 |
2017年 | 146篇 |
2016年 | 291篇 |
2015年 | 273篇 |
2014年 | 343篇 |
2013年 | 715篇 |
2012年 | 732篇 |
2011年 | 922篇 |
2010年 | 545篇 |
2009年 | 462篇 |
2008年 | 764篇 |
2007年 | 822篇 |
2006年 | 811篇 |
2005年 | 819篇 |
2004年 | 650篇 |
2003年 | 509篇 |
2002年 | 438篇 |
2001年 | 399篇 |
2000年 | 380篇 |
1999年 | 201篇 |
1998年 | 196篇 |
1997年 | 204篇 |
1996年 | 254篇 |
1995年 | 225篇 |
1994年 | 218篇 |
1993年 | 262篇 |
1992年 | 245篇 |
1991年 | 234篇 |
1990年 | 176篇 |
1989年 | 186篇 |
1988年 | 214篇 |
1987年 | 192篇 |
1986年 | 160篇 |
1985年 | 209篇 |
1984年 | 189篇 |
1983年 | 145篇 |
1982年 | 196篇 |
1981年 | 176篇 |
1980年 | 159篇 |
1979年 | 158篇 |
1978年 | 161篇 |
1977年 | 122篇 |
1976年 | 139篇 |
1975年 | 106篇 |
1974年 | 122篇 |
1973年 | 101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.
Di Turo Francesca Parra Rafael Piquero-Cilla Joan Favero Gabriele Doménech-Carbó Antonio 《Journal of Solid State Electrochemistry》2019,23(3):771-781
Journal of Solid State Electrochemistry - Electrochemical impedance spectroscopy (EIS) and voltammetry of immobilized particles (VIMP) measurements using air-saturated mineral water and... 相似文献
4.
Set-Valued and Variational Analysis - Probability constraints are a popular modelling mechanism in applications. They help to model feasible decisions when the latter are taken prior to observing... 相似文献
5.
Journal of Statistical Physics - We consider the symmetric exclusion process on suitable random grids that approximate a compact Riemannian manifold. We prove that a class of random walks on these... 相似文献
6.
Ieva
Dauickait Amos S. Lawless Jennifer A. Scott Peter Jan van Leeuwen 《Numerical Linear Algebra with Applications》2020,27(5)
We consider the large sparse symmetric linear systems of equations that arise in the solution of weak constraint four‐dimensional variational data assimilation, a method of high interest for numerical weather prediction. These systems can be written as saddle point systems with a 3 × 3 block structure but block eliminations can be performed to reduce them to saddle point systems with a 2 × 2 block structure, or further to symmetric positive definite systems. In this article, we analyse how sensitive the spectra of these matrices are to the number of observations of the underlying dynamical system. We also obtain bounds on the eigenvalues of the matrices. Numerical experiments are used to confirm the theoretical analysis and bounds. 相似文献
7.
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
8.
9.
10.