全文获取类型
收费全文 | 68531篇 |
免费 | 3447篇 |
国内免费 | 852篇 |
学科分类
数理化 | 72830篇 |
出版年
2023年 | 563篇 |
2022年 | 533篇 |
2021年 | 842篇 |
2020年 | 1180篇 |
2019年 | 1118篇 |
2018年 | 1502篇 |
2017年 | 1352篇 |
2016年 | 2555篇 |
2015年 | 2138篇 |
2014年 | 2207篇 |
2013年 | 4610篇 |
2012年 | 4460篇 |
2011年 | 4264篇 |
2010年 | 2849篇 |
2009年 | 2451篇 |
2008年 | 3688篇 |
2007年 | 3425篇 |
2006年 | 3138篇 |
2005年 | 2968篇 |
2004年 | 2610篇 |
2003年 | 2117篇 |
2002年 | 1916篇 |
2001年 | 1485篇 |
2000年 | 1354篇 |
1999年 | 1027篇 |
1998年 | 807篇 |
1997年 | 733篇 |
1996年 | 914篇 |
1995年 | 657篇 |
1994年 | 761篇 |
1993年 | 661篇 |
1992年 | 662篇 |
1991年 | 575篇 |
1990年 | 616篇 |
1989年 | 517篇 |
1988年 | 488篇 |
1987年 | 449篇 |
1986年 | 441篇 |
1985年 | 602篇 |
1984年 | 563篇 |
1983年 | 434篇 |
1982年 | 424篇 |
1981年 | 452篇 |
1980年 | 406篇 |
1979年 | 353篇 |
1978年 | 363篇 |
1977年 | 351篇 |
1976年 | 362篇 |
1975年 | 317篇 |
1973年 | 333篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
1.
2.
Dominik Vítek Prof. Aleš Růžička Lise Vermeersch Dr. Libor Dostál Dr. Jan Turek Prof. Roman Jambor 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(70):e202202639
Reactivity studies of the GeII→B complex L(Cl)Ge⋅BH3 ( 1 ; L=2-Et2NCH2-4,6-tBu2-C6H2) were performed to determine the effect on the GeII→B donation. N-coordinated compounds L(OtBu)Ge⋅BH3 ( 2 ) and [LGe⋅BH3]2 ( 3 ) were prepared. The possible tuning of the GeII→B interaction was proved experimentally, yielding compounds 1-PPh2-8-(LGe)-C10H6 ( 4 ) and L(Cl)Ge⋅GaCl3 ( 5 ) without a GeII→B interaction. In 5 , an unprecedented GeII→Ga coordination was revealed. The experimental results were complemented by a theoretical study focusing on the bonding in 1 − 5 . The different strength of the GeII→E (E=B, Ga) donation was evaluated by using energy decomposition analysis. The basicity of different L(X)Ge groups through proton affinity is also assessed. 相似文献
3.
Peralta Cecilia Mariana Acosta Gimena Henestrosa Cecilia Gil Raúl Andrés Fernández Liliana Patricia 《Journal of Analytical Chemistry》2022,77(3):308-317
Journal of Analytical Chemistry - The present development involved a flow injection strategy using a mini-column of multiwalled carbon nanotubes and fluorescent detection (λex of 283 nm,... 相似文献
4.
Bazarra Noelia Castejón Alberto Fernández José R. Quintanilla Ramón 《Meccanica》2021,56(12):3025-3037
Meccanica - In this work we study, from the numerical point of view, a one-dimensional thermoelastic problem where the thermal law is of type III. Quasi-static microvoids are also assumed within... 相似文献
5.
Verdecho María-José Alarcón-Valero Faustino Pérez-Perales David Alfaro-Saiz Juan-José Rodríguez-Rodríguez Raúl 《Central European Journal of Operations Research》2021,29(4):1231-1251
Central European Journal of Operations Research - Sustainability practice within supply chains remains in an early development phase. Enterprises still need tools that support the integration of... 相似文献
6.
Set-Valued and Variational Analysis - In a Hilbert framework ℌ, we study the convergence properties of a Newton-like inertial dynamical system governed by a general maximally monotone... 相似文献
7.
8.
A numerical model was developed and validated to investigate the fluid–structure interactions between fully developed pipe flow and core–shell-structured microcapsule in a microchannel. Different flow rates and microcapsule shell thicknesses were considered. A sixth-order rotational symmetric distribution of von Mises stress over the microcapsule shell can be observed on the microcapsule with a thinner shell configuration, especially at higher flow rate conditions. It is also observed that when being carried along in a fully developed pipe flow, the microcapsule with a thinner shell tends to accumulate stress at a higher rate compared to that with a thicker shell. In general, for the same microcapsule configuration, higher flow velocity would induce a higher stress level over the microcapsule shell. The deformation gradient was used to capture the microcapsule's deformation in the present study. The effect of Young's modulus on the microcapsule shell on the microcapsule deformation was investigated as well. Our findings will shed light on the understanding of the stability of core–shell-structured microcapsule when subjected to flow-induced shear stress in a microfluidic system, enabling a more exquisite control over the breakup dynamics of drug-loaded microcapsule for biomedical applications. 相似文献
9.
10.
Interactions of the vector breathers for the coupled Hirota system with $$4\times 4$$ 4 × 4 Lax pair
Nonlinear Dynamics - In this paper, we investigate the interactions of the vector breathers for the coupled Hirota system with $$4\times 4$$ Lax pair. Firstly, we give the first-order breather... 相似文献