全文获取类型
收费全文 | 24360篇 |
免费 | 1177篇 |
国内免费 | 669篇 |
专业分类
化学 | 16866篇 |
晶体学 | 229篇 |
力学 | 928篇 |
综合类 | 46篇 |
数学 | 3199篇 |
物理学 | 4938篇 |
出版年
2023年 | 167篇 |
2022年 | 359篇 |
2021年 | 457篇 |
2020年 | 493篇 |
2019年 | 470篇 |
2018年 | 391篇 |
2017年 | 360篇 |
2016年 | 626篇 |
2015年 | 556篇 |
2014年 | 680篇 |
2013年 | 1339篇 |
2012年 | 1461篇 |
2011年 | 1728篇 |
2010年 | 974篇 |
2009年 | 867篇 |
2008年 | 1385篇 |
2007年 | 1335篇 |
2006年 | 1357篇 |
2005年 | 1223篇 |
2004年 | 1092篇 |
2003年 | 972篇 |
2002年 | 941篇 |
2001年 | 392篇 |
2000年 | 324篇 |
1999年 | 280篇 |
1998年 | 293篇 |
1997年 | 281篇 |
1996年 | 317篇 |
1995年 | 253篇 |
1994年 | 232篇 |
1993年 | 201篇 |
1992年 | 201篇 |
1991年 | 210篇 |
1990年 | 158篇 |
1989年 | 136篇 |
1988年 | 170篇 |
1987年 | 162篇 |
1985年 | 228篇 |
1984年 | 246篇 |
1983年 | 179篇 |
1982年 | 252篇 |
1981年 | 225篇 |
1980年 | 229篇 |
1979年 | 209篇 |
1978年 | 200篇 |
1977年 | 184篇 |
1976年 | 183篇 |
1975年 | 154篇 |
1974年 | 163篇 |
1973年 | 159篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
Jin-Mok Hur Chung-Seok Seo Sun-Seok Hong Dae-Seung Kang Seong-Won Park 《Reaction Kinetics and Catalysis Letters》2003,80(2):217-222
The concept of a novel electrochemical reduction process for the treatment of spent nuclear fuels in Li2O-LiCl molten salt was proposed and fresh tests using U3O8 powder were carried out to elucidate the reaction mechanism and verify the feasibility of the process. Electrolysis of Li2O and reduction of U3O8 powder took place simultaneously at the cathode part of the electrolysis cell via a catalytic EC mechanism and the conversion of U3O8 to U metal was more than 99%.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
32.
Huimin Xie Biao Li Robert Geer Bai Xu James Castracane 《Optics and Lasers in Engineering》2003,40(3):163-177
A focused ion beam (FIB) Moiré method is proposed to measure the in-plane deformation of object in a micrometer scale. The FIB Moiré is generated by the interference between a prepared specimen grating and FIB raster scan lines. The principle of the FIB Moiré is described. The sensitivity and accuracy of deformation measurement are discussed in detail. Several specimen gratings with 0.14 and 0.20 μm spacing are used to generate FIB Moiré patterns. The FIB Moiré method is successfully used to measure the residual deformation in a micro-electro-mechanical system structure after removing the SiO2 sacrificial layer with a 5000 lines/mm grating. The results demonstrate the feasibility of this method. 相似文献
33.
34.
由“从正则分布出发,在小涨落近似下得出的能量涨落分布公式”求得的能量涨落的二次矩与直接由正则分布求得的二次矩完全相同,但分别由二求得的高次矩并不完全相同。 相似文献
35.
Jilly James Chidambaram Ramalechume Asit Baran Mandal 《Journal of Polymer Science.Polymer Physics》2007,45(17):2410-2420
The shape, size, aggregation, hydration, and correlation times of water insoluble PEO‐PPO‐PEO triblock copolymer micelles with sodium dodecylsulfate (SDS) micelles were investigated using transport studies and dynamic light scattering technique. From the conductance of micellar solutions of the polymer in 25 mM SDS and 5 mM NaCl, the hydration of polymer micelles were determined using the principle of obstruction of electrolyte migration by the polymer. The asymmetry of the micellar particles of polymer and polymer‐SDS mixed micellar systems in 5 mM NaCl and their average axial ratios were calculated using intrinsic viscosity and hydration data obeying Simha–Einstein equation. Hydration number and micellar sizes were variable with temperature. The shape of the polymer micelles has been ellipsoidal rather than spherical. The micellar volume, hydrodynamic radius, radius of gyration, diffusional coefficients as well as translational, rotational and effective correlation times have been calculated from the absolute values of the axes. The partial molal volume of polymer micelles has also been determined and its comparison with the molar volume of pure polymer suggested a volume contraction due to immobilization of the water phase by the hydrophilic head groups of the polymer. The thermodynamic activation parameters for viscous flow favor a more ordered water structure around polymer micelles at higher temperatures. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2410–2420, 2007 相似文献
36.
Young-Bae Seu Taeg-Kyeong Lim Chang-Jin Kim Sun-Chul Kang 《Tetrahedron: Asymmetry》1995,6(12):3009-3014
Optically active epoxy alcohol, (R)-2-butyryloxymethylglycidol3 which is the precursor of a tert-alcohol chiral building block was obtained in high enantiomeric purity, 98.7% e.e., by lipase-catalyzed asymmetric hydrolysis using a phosphate buffer and organic co-solvent system in 95% of chemical yield. 相似文献
37.
38.
Past cellular automata models of self-replication have always been initialized with an original copy of the structure that will replicate, and have been based on a transition function that only works for a single, specific structure. This article demonstrates for the first time that it is possible to create cellular automata models in which a self-replicating structure emerges from an initial state having a random density and distribution of individual components. These emergent self-replicating structures employ a fairly general rule set that can support the replication of structures of different sizes and their growth from smaller to larger ones. This rule set also allows “random” interactions of self-replicating structures with each other and with other structures within the cellular automata space. Systematic simulations show that emergence and growth of replicants occurs often and is essentially independent of the cellular space size, initial random pattern of components, and initial density of components, over a broad range of these parameters. The number of replicants and the total number of components they incorporate generally approach quasi-stable values with time. 相似文献
39.
40.
Miklos Ajtai James Aspnes Moni Naor Yuval Rabani Leonard J Schulman Orli Waarts 《Journal of Algorithms in Cognition, Informatics and Logic》1998,29(2):306-357
On-line machine scheduling has been studied extensively, but the fundamental issue of fairness in scheduling is still mostly open. In this paper we explore the issue in settings where there are long-lived processes which should be repeatedly scheduled for various tasks throughout the lifetime of a system. For any such instance we develop a notion ofdesiredload of a process, which is a function of the tasks it participates in. Theunfairnessof a system is the maximum, taken over all processes, of the difference between the desired load and the actual load.An example of such a setting is thecarpool problemsuggested by Fagin and Williams [IBM Journal of Research and Development27(2) (1983), 133–139]. In this problem, a set ofnpeople form a carpool. On each day a subset of the people arrive and one of them is designated as the driver. A scheduling rule is required so that the driver will be determined in a “fair” way.We investigate this problem under various assumptions on the input distribution. We also show that the carpool problems can capture several other problems of fairness in scheduling. 相似文献