全文获取类型
收费全文 | 1412篇 |
免费 | 120篇 |
国内免费 | 90篇 |
专业分类
化学 | 201篇 |
晶体学 | 4篇 |
力学 | 155篇 |
综合类 | 40篇 |
数学 | 852篇 |
物理学 | 370篇 |
出版年
2024年 | 2篇 |
2023年 | 11篇 |
2022年 | 21篇 |
2021年 | 26篇 |
2020年 | 31篇 |
2019年 | 33篇 |
2018年 | 36篇 |
2017年 | 36篇 |
2016年 | 45篇 |
2015年 | 33篇 |
2014年 | 102篇 |
2013年 | 120篇 |
2012年 | 64篇 |
2011年 | 80篇 |
2010年 | 63篇 |
2009年 | 85篇 |
2008年 | 92篇 |
2007年 | 76篇 |
2006年 | 75篇 |
2005年 | 72篇 |
2004年 | 61篇 |
2003年 | 62篇 |
2002年 | 50篇 |
2001年 | 43篇 |
2000年 | 34篇 |
1999年 | 31篇 |
1998年 | 30篇 |
1997年 | 29篇 |
1996年 | 23篇 |
1995年 | 13篇 |
1994年 | 15篇 |
1993年 | 16篇 |
1992年 | 11篇 |
1991年 | 11篇 |
1990年 | 15篇 |
1989年 | 9篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 8篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有1622条查询结果,搜索用时 756 毫秒
121.
J. P. Geiger B. Huguenin M. Nicole D. Nandris 《Applied biochemistry and biotechnology》1986,13(2):97-110
A laccase that has been isolated previously (1) from the Basidiomycete,Rigidoporus lignosus, a white rot fungus of rubber tree, was used in the present study. When a thioglycolic lignin (TGL) was incubated in the
presence of this enzyme, pronounced changes in the UV spectrum and size distribution of the substrate were observed. Sephadex
gel filtration indicated that two types of reactions occurred: (1) A degradation of the polymer, as evidenced by the production
of low-molecular-weight material; and (2) a condensation of some of the TGL molecules, as revealed by an increase in the fractions
of higher molecular weight. 相似文献
122.
The Jokulhlaup of the Yarkant River (Yarkant He) is usually csused by the sudden discharge of the glacier-dammed lake and the mode of the discharge is the rapid expansion of the subglacial channel. Keyajir (Kyagar) Glacier and Telamukanli Glacier are on the upper reaches of the Keleqin (Shaksgam) River, the chief birthplaces of this kind of flood. Up to the end of this century, since the global climate has become warmer, the glaciers have accordingly shrunk and become thinner, with the result that the size and dimensions of the glacier-dammed lakes and their outburst floods have diminished. All these simply reveal the mystery of the Jokulhlaups of the Yarkant River in Xinjiang. 相似文献
123.
We consider a finite-horizon control model with additive input. There are two convex functions which describe the running cost and the terminal cost within the system. The cost of input is proportional to the input and can take both positive and negative values. It is shown that there exists a deterministic control problem whose optimal cost is the same as the one in the stochastic control problem. The optimal policy for the stochastic problem consists of keeping the process as close to the optimal deterministic trajectory as possible.This research is supported by NSERC Grant A4619, MRCO, NSF Grant DMS-86-01510, and AFOSR Grant 87-0278. 相似文献
124.
K. Madhavi Latha 《Journal of Quantitative Spectroscopy & Radiative Transfer》2006,101(2):367-379
The extent to which airborne particles penetrate into the human respiratory system is determined mainly by their size, with possible health effects. The research over the scientific evidence of the role of airborne particles in adverse health effects has been intensified in recent years. In the present study, seasonal variations of PM10 and its relation with anthropogenic activities have been studied by using the data from UK National Air Quality Archive over Reading, UK. The diurnal variation of PM10 shows a morning peak during 7:00-10:00 LT and an evening peak during 19:00-22:00 LT. The variation between 12:00 and 17:00 LT remains more or less steady for PM10 with the minimum value of ∼16 μg m−3. PM10 and black smoke (BS) concentrations during weekdays were found to be high compared to weekends. A reduction in the concentration of PM10 has been found during the Christmas holidays compared to normal days during December. Seasonal variations of PM10 showed high values during spring compared to other seasons. A linear relationship has been found between PM10 and NOx during March, July, November and December suggesting that most of the PM10 is due to local traffic exhaust emissions. PM10 and SO2 concentrations showed positive correlation with the correlation coefficient of R2=0.65 over the study area. Seasonal variations of SO2 and NOx showed high concentrations during winter and low concentrations during spring. Fraction of BS in PM10 has been found to be 50% during 2004 over the study area. 相似文献
125.
《中国科学A辑(英文版)》2008,(10)
We discuss the relations among the best approximation En(f) and the Fourier coeffcients of a function, f(n) ∈ C,n = 0,±1,±2,..., under the conditions that {f (n)}∞n=0 ∈ MVBVS* and {f (n) f(n)}∞n=0 ∈ MVBVS*, where MVBVS* is the class of the so-called Strong Mean Value Bounded Variation Sequences. 相似文献
126.
Scott A. Sarra 《Numerical Algorithms》2006,41(1):17-33
Digital total variation filtering is analyzed as a fast, robust, post-processing method for accelerating the convergence of
pseudospectral approximations that have been contaminated by Gibbs oscillations. The method, which originated in image processing,
can be combined with spectral filters to quickly post-process large data sets with sharp resolution of discontinuities and
with exponential accuracy away from the discontinuities. 相似文献
127.
给出了弹性系统瞬时势能泛函的一般表达式,得到了其关于任意挠曲输液管道的具体表达式,根据瞬时最小势能原理建立了该结构的有限元动力方程,并首次推导出其离心力载荷公式,讨论了管道结构静平衡位置的发散流速的确定,最后,用简单的实验结果对理论分析作了验证。 相似文献
128.
耦合热弹性问题的分区变分原理及其广义变分原理 总被引:4,自引:0,他引:4
本文在文献[1]和[2]的基础上建立并论证了耦合热弹性问题的分区变分原理及其分区广义变分原理 相似文献
129.
Anneli Kruve Riin Rebane Karin Kipper Maarja-Liisa Oldekop Hanno Evard Koit Herodes Pekka Ravio Ivo Leito 《Analytica chimica acta》2015
This is the part I of a tutorial review intending to give an overview of the state of the art of method validation in liquid chromatography mass spectrometry (LC–MS) and discuss specific issues that arise with MS (and MS/MS) detection in LC (as opposed to the “conventional” detectors). The Part I briefly introduces the principles of operation of LC–MS (emphasizing the aspects important from the validation point of view, in particular the ionization process and ionization suppression/enhancement); reviews the main validation guideline documents and discusses in detail the following performance parameters: selectivity/specificity/identity, ruggedness/robustness, limit of detection, limit of quantification, decision limit and detection capability. With every method performance characteristic its essence and terminology are addressed, the current status of treating it is reviewed and recommendations are given, how to determine it, specifically in the case of LC–MS methods. 相似文献
130.
本文基于计算结构力学概念提出了刚架结构连续变更定理,用数值分析与递推公式相结合的方法连续生成结构极限状态函数,给出了结构退化为机构的新判据。由于引用了计算结构力学方法,重分析不必重新形成结构刚度阵,不必反复求逆矩阵,大大提高了计算效率。 相似文献