全文获取类型
收费全文 | 8581篇 |
免费 | 453篇 |
国内免费 | 108篇 |
专业分类
化学 | 6275篇 |
晶体学 | 70篇 |
力学 | 227篇 |
综合类 | 11篇 |
数学 | 845篇 |
物理学 | 1714篇 |
出版年
2023年 | 42篇 |
2022年 | 117篇 |
2021年 | 142篇 |
2020年 | 150篇 |
2019年 | 177篇 |
2018年 | 113篇 |
2017年 | 116篇 |
2016年 | 256篇 |
2015年 | 233篇 |
2014年 | 309篇 |
2013年 | 506篇 |
2012年 | 624篇 |
2011年 | 743篇 |
2010年 | 459篇 |
2009年 | 341篇 |
2008年 | 582篇 |
2007年 | 487篇 |
2006年 | 469篇 |
2005年 | 480篇 |
2004年 | 381篇 |
2003年 | 302篇 |
2002年 | 310篇 |
2001年 | 169篇 |
2000年 | 195篇 |
1999年 | 113篇 |
1998年 | 86篇 |
1997年 | 64篇 |
1996年 | 74篇 |
1995年 | 82篇 |
1994年 | 80篇 |
1993年 | 75篇 |
1992年 | 55篇 |
1991年 | 54篇 |
1990年 | 52篇 |
1989年 | 41篇 |
1988年 | 45篇 |
1987年 | 38篇 |
1986年 | 28篇 |
1985年 | 44篇 |
1984年 | 38篇 |
1983年 | 25篇 |
1982年 | 37篇 |
1981年 | 43篇 |
1980年 | 29篇 |
1979年 | 48篇 |
1978年 | 40篇 |
1977年 | 44篇 |
1976年 | 35篇 |
1975年 | 27篇 |
1974年 | 29篇 |
排序方式: 共有9142条查询结果,搜索用时 0 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.
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
3.
4.
Quantitative analysis of polyhexamethylene guanidine (PHMG) oligomers via matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry with an ionic‐liquid matrix 下载免费PDF全文
5.
6.
Jong Uhn Kim 《Transactions of the American Mathematical Society》2002,354(3):1117-1135
In this paper we discuss an initial-boundary value problem for a stochastic nonlinear equation arising in one-dimensional viscoelasticity. We propose to use a new direct method to obtain a solution. This method is expected to be applicable to a broad class of nonlinear stochastic partial differential equations.
7.
8.
In this paper, we shall find the uniquerational price associated with the exchange option. Also, we find the decomposition of Snell envelope and value function of the American exchange option. 相似文献
9.
Jong Chan Lee Jin Young Park So Young Yoon Yong Hun Bae Seung Jun Lee 《Tetrahedron letters》2004,45(1):191-193
A novel and direct method for the synthesis of α-halocarbonyl compounds using sequential treatment of carbonyl compounds with [hydroxy(tosyloxy)iodo]benzene followed by magnesium halides under solvent-free microwave irradiation conditions is described. 相似文献
10.
Ching Sum Hui Lillian Sze Man Lam Chun Yin Wai Kin Chan Aleksandra B. Djurii 《Journal of polymer science. Part A, Polymer chemistry》2003,41(11):1708-1715
Polyurethanes incorporated with rhenium diimine complexes were synthesized. The polymers exhibited interesting morphologies and solution properties. Results from gel permeation chromatography suggested the formation of polymer aggregates in solutions. The polymers could act as probes for metal ions. The addition of metal ions to polymer solutions led to significant changes in the electronic absorption properties of the polymer solutions. This was attributed to the interactions between the polyether moieties and metal ions. The metal complexes could also act as efficient photosensitizers. After doping with charge‐transport viologens, the photoconductivity of the polymers was greatly enhanced. The experimental quantum efficiency was simulated with Onsager's theory. The thermalization distances and the primary yields were typically 12–14 Å and 10?3, respectively. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1708–1715, 2003 相似文献