全文获取类型
收费全文 | 8490篇 |
免费 | 1384篇 |
国内免费 | 1250篇 |
专业分类
化学 | 6586篇 |
晶体学 | 144篇 |
力学 | 456篇 |
综合类 | 77篇 |
数学 | 865篇 |
物理学 | 2996篇 |
出版年
2024年 | 30篇 |
2023年 | 190篇 |
2022年 | 313篇 |
2021年 | 358篇 |
2020年 | 440篇 |
2019年 | 443篇 |
2018年 | 322篇 |
2017年 | 352篇 |
2016年 | 415篇 |
2015年 | 439篇 |
2014年 | 506篇 |
2013年 | 676篇 |
2012年 | 733篇 |
2011年 | 804篇 |
2010年 | 566篇 |
2009年 | 493篇 |
2008年 | 583篇 |
2007年 | 461篇 |
2006年 | 417篇 |
2005年 | 350篇 |
2004年 | 264篇 |
2003年 | 233篇 |
2002年 | 269篇 |
2001年 | 189篇 |
2000年 | 169篇 |
1999年 | 134篇 |
1998年 | 103篇 |
1997年 | 103篇 |
1996年 | 103篇 |
1995年 | 105篇 |
1994年 | 97篇 |
1993年 | 81篇 |
1992年 | 56篇 |
1991年 | 48篇 |
1990年 | 44篇 |
1989年 | 50篇 |
1988年 | 29篇 |
1987年 | 25篇 |
1986年 | 27篇 |
1985年 | 36篇 |
1984年 | 19篇 |
1983年 | 15篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1959年 | 2篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
941.
We study the adaptive decomposition of functions in the monogenic Hardy spaces H2by higher order Szeg kernels under the framework of Clifford algebra and Clifford analysis,in the context of unit ball and half space.This is a sequel and a higher-dimensional generalization of our recent study on the complex Hardy spaces. 相似文献
942.
钱莲芬 《浙江大学学报(理学版)》1991,18(1):7-15
本文证 明了孙东初在 〕 中提 出的条件密度双重核 估计。川 幻 在样 本为甲一混 合时的渐近正态性 相似文献
943.
Xiang-Yang Zhang Gilles Févotte Liang Zhong Gang Qian Xing-Gui Zhou Wei-Kang Yuan 《Journal of Crystal Growth》2010,312(19):2747-2755
The influence of malic acid, which acts as an impurity on the cooling crystallization of zinc lactate is investigated in this paper by monitoring the relative supersaturation and the number of crystals during crystallization. The presence of malic acid increases the solution solubility and makes the metastable zone wider; it also changes the habit of the crystal. The purity of the final products is shown to be influenced by the amount and size of seed crystals, cooling rate, seeding temperature and final temperature, but appears to depend mainly on the particle size and level of supersaturation. Residual supersaturation thresholds are observed that depend on the final temperature. A model is proposed to predict the steady-state supersaturation value from the final temperature at a given impurity concentration. This model is based on Kubota and Gibbs equations. 相似文献
944.
An experimental study has been conducted to assess the structural refinement of magnesium and its alloys by ultrasonic irradiation during solidification. It is shown that (i) ultrasonic irradiation leads to significant refinement only in the presence of adequate solute, which is alloy dependent; (ii) the attendant grain density increases linearly with increase in solute content at a given irradiation level; (iii) increasing the solute content at a low irradiation level above the cavitation threshold is more effective than substantially increasing the irradiation intensity; and (iv) the difference in the grain size between two ultrasonicated magnesium alloys is mainly determined by the solute content rather than the irradiation intensity. In view of these, the effect of ultrasonic irradiation on solute redistribution in a solidifying magnesium alloy seems rather limited even at a substantial intensity level such as 1700 W cm−2. The implications of these findings are discussed and a mechanism is proposed to account for the experimental observations. 相似文献
945.
946.
947.
A [3+3+3]-fragment coupling strategy was successfully applied in the synthesis of the nonacyclopeptide of chlorofusin, a potent natural antagonist against p53-MDM2 interactions. The accomplished convergent synthesis includes parallel syntheses of three tripeptides and their sequential assembly, and macrocyclization of the linear precursor to the required 27-membered nonacyclopeptide. 相似文献
948.
1INTRODUCTIONCoppercomplexeshavealargevarietyofstericstructuresandplayanimportantroleincatalysingtheenzymaticactivities,which... 相似文献
949.
Prof. Dr. Karen Hemelsoet Qingyun Qian Thierry De Meyer Kristof De Wispelaere Dr. Bart De Sterck Prof. Dr. Bert M. Weckhuysen Prof. Dr. Michel Waroquier Prof. Dr. Veronique Van Speybroeck 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(49):16595-16606
The optical absorption properties of (poly)aromatic hydrocarbons occluded in a nanoporous environment were investigated by theoretical and experimental methods. The carbonaceous species are an essential part of a working catalyst for the methanol‐to‐olefins (MTO) process. In situ UV/Vis microscopy measurements on methanol conversion over the acidic solid catalysts H‐SAPO‐34 and H‐SSZ‐13 revealed the growth of various broad absorption bands around 400, 480, and 580 nm. The cationic nature of the involved species was determined by interaction of ammonia with the methanol‐treated samples. To determine which organic species contribute to the various bands, a systematic series of aromatics was analyzed by means of time‐dependent density functional theory (TDDFT) calculations. Static gas‐phase simulations revealed the influence of structurally different hydrocarbons on the absorption spectra, whereas the influence of the zeolitic framework was examined by using supramolecular models within a quantum mechanics/molecular mechanics framework. To fully understand the origin of the main absorption peaks, a molecular dynamics (MD) study on the organic species trapped in the inorganic host was essential. During such simulation the flexibility is fully taken into account and the effect on the UV/Vis spectra is determined by performing TDDFT calculations on various snapshots of the MD run. This procedure allows an energy absorption scale to be provided and the various absorption bands determined from in situ UV/Vis spectra to be assigned to structurally different species. 相似文献
950.