全文获取类型
收费全文 | 3346篇 |
免费 | 80篇 |
国内免费 | 20篇 |
专业分类
化学 | 2178篇 |
晶体学 | 37篇 |
力学 | 123篇 |
数学 | 493篇 |
物理学 | 615篇 |
出版年
2022年 | 23篇 |
2021年 | 24篇 |
2020年 | 36篇 |
2019年 | 34篇 |
2018年 | 29篇 |
2017年 | 20篇 |
2016年 | 71篇 |
2015年 | 66篇 |
2014年 | 51篇 |
2013年 | 121篇 |
2012年 | 176篇 |
2011年 | 199篇 |
2010年 | 105篇 |
2009年 | 89篇 |
2008年 | 179篇 |
2007年 | 187篇 |
2006年 | 158篇 |
2005年 | 160篇 |
2004年 | 146篇 |
2003年 | 121篇 |
2002年 | 118篇 |
2001年 | 76篇 |
2000年 | 56篇 |
1999年 | 37篇 |
1998年 | 39篇 |
1997年 | 30篇 |
1996年 | 58篇 |
1995年 | 42篇 |
1994年 | 48篇 |
1993年 | 42篇 |
1992年 | 50篇 |
1991年 | 46篇 |
1990年 | 42篇 |
1989年 | 44篇 |
1988年 | 32篇 |
1987年 | 33篇 |
1986年 | 35篇 |
1985年 | 43篇 |
1984年 | 51篇 |
1983年 | 38篇 |
1982年 | 51篇 |
1981年 | 43篇 |
1980年 | 36篇 |
1979年 | 25篇 |
1978年 | 35篇 |
1977年 | 29篇 |
1976年 | 30篇 |
1975年 | 38篇 |
1974年 | 19篇 |
1973年 | 37篇 |
排序方式: 共有3446条查询结果,搜索用时 0 毫秒
1.
2.
3.
Graham Smith 《The Journal of the Operational Research Society》1989,40(9):761-770
Courses which teach discrete-event simulation are based on many different simulation languages. The requirements for a language to support teaching simulation are discussed. In particular, it is recommended that such languages separate into distinct modules those aspects of simulation which are taught as separate topics. Implementation of the separation is discussed. The SEESIM language, developed as a teaching aid, is described, and examples of its use are given. Straightforward use of SEESIM can be learned quickly, yet the language provides facilities for a staged introduction to advanced concepts of simulation. 相似文献
4.
Philip A. Wheeler Michael Brungs Graham R. Atkins 《Journal of Sol-Gel Science and Technology》2003,27(3):321-326
Organically modified silicates (ormosils) have been viewed as possible materials for optical signal processing devices for communications networks. One significant problem obstructing their use in this application is the absorption of infrared light by hydroxy species (present for example in silanol groups (SiOH) and water) around the communications wavelengths (1310 and 1550 nm). We have investigated several ormosil compositions, synthesised via an aqueous sol-gel method, to determine if residual hydroxy groups can be removed more effectively via reducing the connectivity of the material by increasing the number of organic groups (such as Si—CH3). Furthermore, we have investigated the effect of different inert atmospheres on the drying process. It was found that reducing the connectivity does promote the removal of hydroxy absorption, mainly via the condensation of residual silanol groups, but also by removal of residual water, depending on the other precursors in the system. It was also found that the drying atmosphere used (nitrogen or helium) had no effect on the drying process. 相似文献
5.
6.
Optimized prefactored compact schemes 总被引:1,自引:0,他引:1
The numerical simulation of aeroacoustic phenomena requires high-order accurate numerical schemes with low dispersion and dissipation errors. In this paper we describe a strategy for developing high-order accurate prefactored compact schemes, requiring very small stencil support. These schemes require fewer boundary stencils and offer simpler boundary condition implementation than existing compact schemes. The prefactorization strategy splits the central implicit schemes into forward and backward biased operators. Using Fourier analysis, we show it is possible to select the coefficients of the biased operators such that their dispersion characteristics match those of the original central compact scheme and their numerical wavenumbers have equal and opposite imaginary components. This ensures that when the forward and backward stencils are added, the original central compact scheme is recovered. To extend the resolution characteristic of the schemes, an optimization strategy is employed in which formal order of accuracy is sacrificed in preference to enhanced resolution characteristics across the range of wavenumbers realizable on a given mesh. The resulting optimized schemes yield improved dispersion characteristics compared to the standard sixth- and eighth-order compact schemes making them more suitable for high-resolution numerical simulations in gas dynamics and computational aeroacoustics. The efficiency, accuracy and convergence characteristics of the new optimized prefactored compact schemes are demonstrated by their application to several test problems. 相似文献
7.
Graham R. Knox Peter L. Pauson Debra Willison 《Journal of organometallic chemistry》1993,450(1-2):177-184
Phenylazoferrocene undergoes nickelation and palladation exclusively on the phenyl group. Lithium phenylazocyclopentadienide has been converted into derivatives of Mo, Mn, Fe, Ru and Rh. 相似文献
8.
The electron-stimulated desorption (ESD) of D− and H− ions from condensed D2O and H2O films is investigated. Three low-energy peaks are observed in the ESD anion yield, which are identified as arising from excitation of 2B1, 2A1 and 2B2 dissociative electron attachment (DEA) resonances. Additional structure is observed between 18 and 32 eV, which may be due to ion pair formation or to DEA resonances involving the 2a1 orbital. The ion yield resulting from excitation of the 2B1 resonance increases as the film is heated. We attribute the increase in the ion yield to thermally induced hydrogen bond breaking near the surface, which enhances the lifetimes of the excited states that lead to desorption. 相似文献
9.
10.
Massively parallel computational paradigms can mitigate many issues associated with the analysis of large and complex remotely sensed data sets. Recently, the Beowulf cluster has emerged as the most attractive, massively parallel architecture due to its low cost and high performance. Whereas most Beowulf designs have emphasized numerical modeling applications, the Parallel Image Processing Environment (PIPE) specifically addresses the unique requirements of remote sensing applications. Automated, parallelization of user-defined analyses is fully supported. A neural network application, applied to Along Track Scanning Radiometer-2 (ATSR-2) data shows the advantages and performance characteristics of PIPE. 相似文献