全文获取类型
收费全文 | 3772篇 |
免费 | 110篇 |
国内免费 | 14篇 |
学科分类
数理化 | 3896篇 |
出版年
2021年 | 36篇 |
2020年 | 61篇 |
2019年 | 44篇 |
2018年 | 44篇 |
2017年 | 23篇 |
2016年 | 69篇 |
2015年 | 49篇 |
2014年 | 48篇 |
2013年 | 179篇 |
2012年 | 156篇 |
2011年 | 206篇 |
2010年 | 120篇 |
2009年 | 88篇 |
2008年 | 169篇 |
2007年 | 172篇 |
2006年 | 183篇 |
2005年 | 152篇 |
2004年 | 154篇 |
2003年 | 107篇 |
2002年 | 139篇 |
2001年 | 76篇 |
2000年 | 78篇 |
1999年 | 54篇 |
1998年 | 49篇 |
1997年 | 49篇 |
1996年 | 67篇 |
1995年 | 78篇 |
1994年 | 59篇 |
1993年 | 67篇 |
1992年 | 61篇 |
1991年 | 64篇 |
1990年 | 50篇 |
1989年 | 52篇 |
1988年 | 37篇 |
1987年 | 36篇 |
1986年 | 43篇 |
1985年 | 64篇 |
1984年 | 50篇 |
1983年 | 46篇 |
1982年 | 47篇 |
1981年 | 36篇 |
1980年 | 52篇 |
1979年 | 50篇 |
1978年 | 41篇 |
1977年 | 45篇 |
1976年 | 22篇 |
1975年 | 41篇 |
1974年 | 45篇 |
1973年 | 43篇 |
1970年 | 21篇 |
排序方式: 共有3896条查询结果,搜索用时 171 毫秒
1.
2.
Crosslinked poly(ethylene oxide) containing siloxanes fabricated through thiol‐ene photochemistry 下载免费PDF全文
Victor A. Kusuma Elliot A. Roth William P. Clafshenkel Steven S. Klara Xu Zhou Surendar R. Venna Erik Albenze David R. Luebke Meagan S. Mauter Richard R. Koepsel Alan J. Russell David Hopkinson Hunaid B. Nulwala 《Journal of polymer science. Part A, Polymer chemistry》2015,53(13):1548-1557
Homogenous amphiphilic crosslinked polymer films comprising of poly(ethylene oxide) and polysiloxane were synthesized utilizing thiol‐ene “ click ” photochemistry. A systematic variation in polymer composition was Carried out to obtain high quality films with varied amount of siloxane and poly(ethylene oxide). These films showed improved gas separation performance with high gas permeabilities with good CO2/N2 selectivity. Furthermore, the resulting films were also tested for its biocompatibility, as a carrier media which allow human adult mesenchymal stem cells to retain their capacity for osteoblastic differentiation after transplantation. The obtained crosslinked films were characterized using differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis, FTIR, Raman‐IR , and small angle X‐ray scattering. The synthesis ease and commercial availability of the starting materials suggests that these new crosslinked polymer networks could find applications in wide range of applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1548–1557 相似文献
3.
4.
Chromatographia - The reversed phase behaviour of high molecular mass polystyrenes was investigated on C18 bonded phase columns with ethyl acetate-methanol and ethyl acetateacetonitrile mobile... 相似文献
5.
6.
J.R. Cooper 《Journal of Molecular Spectroscopy》2006,239(1):51-58
The ν9 fundamental band of ethane occurs in the 12 μm region. It is the strongest band of ethane in a terrestrial window and is commonly used for the identification of ethane in the Jovian planets. The ν9 + ν4 − ν4 band occurs in the same region; neither can be analysed as an isolated band, since both are embedded in the torsional bath of the ground vibrational state. We report here two global fit models including data from both of these bands as well as the ν3 fundamental and the ν4, 2ν4 − ν4, and 3ν4 torsional transitions. The first is restricted to −5 ? KΔK ? 15 in the hot band and gives an excellent fit to the included data. Three resonant interactions are identified in this fit—a Coriolis interaction with two resonant cases between the ν9 torsional stack and that of the ground vibrational state (gs) and a resonant Fermi interaction between the ν3 fundamental and the gs. Hot band lines with KΔK < −5 are influenced by a fourth perturbation, with a crossing at −11 < KΔK < −10, which has been attributed to an interaction with the ν12 fundamental. A second fit, demonstrating a promising treatment of this interaction, is also presented. 相似文献
7.
I. M. Kolthoff S. R. Cooper V. J. Tulane F. Reimers H. A. J. Pieters K. Höppner V. H. Matula C. B. Macek W. N. Skworzow J. S. Schepelewa F. Čuta K. Kámen S. Cohen R. E. Oesper D. S. Narayanamurthi T. R. Seshadri H. M. State A. W. Kirssanow W. M. Tscherkassow D. M. Mukherjee T. Akiyama Y. Mine S. Yabe Y. Volmar M. Déribéré 《Analytical and bioanalytical chemistry》1937,111(5-6):192-197
8.
Ohne Zusammenfassung 相似文献
9.
K Cooper S C Brailsford R Davies 《The Journal of the Operational Research Society》2007,58(2):168-176
Economic evaluation, such as cost effectiveness analysis, provides a method for comparing healthcare interventions. These evaluations often use modelling techniques such as decision trees, Markov processes and discrete event simulations (DES). With the aid of examples from coronary heart disease, the use of these techniques in different health care situations is discussed. Guidelines for the choice of modelling technique are developed according to the characteristics of the health care intervention.The choice of modelling technique is shown to depend on the acceptance of the modelling technique, model ‘error’, model appropriateness, dimensionality and ease and speed of model development. Generally decision trees are suitable for acute interventions but they cannot model recursion and Markov models are suitable for simple chronic interventions. It is further recommended that population based models be used in order to provide health care outcomes for the likely cost, health benefits and cost effectiveness of the intervention. The population approach will complicate the construction of the model. DES will allow the modeller to construct more complex, dynamic and accurate systems but these may involve a corresponding increase in development time and expense. The modeller will need to make a judgement on the necessary complexity of the model in terms of interaction of individuals and model size and whether queuing for resources, resource constraints or the interactions between individuals are significant issues in the health care system. 相似文献
10.
Using a generalization of the classical ballot theorem, Niu and Cooper [7] established a duality relation between the joint
distribution of several variables associated with the busy cycle inM/G/1 (with a modified first service) and the corresponding joint distribution of several related variables in its dualGI/M/1. In this note, we generalize this duality relation toGI/G/1 queues with modified first services; this clarifies the original result, and shows that the generalized ballot theorem
is superfluous for the duality relation. 相似文献