全文获取类型
收费全文 | 409篇 |
免费 | 12篇 |
国内免费 | 1篇 |
专业分类
化学 | 177篇 |
晶体学 | 3篇 |
力学 | 11篇 |
数学 | 56篇 |
物理学 | 175篇 |
出版年
2022年 | 9篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 7篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 16篇 |
2015年 | 6篇 |
2014年 | 13篇 |
2013年 | 23篇 |
2012年 | 11篇 |
2011年 | 20篇 |
2010年 | 11篇 |
2009年 | 12篇 |
2008年 | 23篇 |
2007年 | 16篇 |
2006年 | 7篇 |
2005年 | 15篇 |
2004年 | 14篇 |
2003年 | 7篇 |
2002年 | 7篇 |
2001年 | 10篇 |
2000年 | 12篇 |
1999年 | 11篇 |
1998年 | 9篇 |
1996年 | 13篇 |
1995年 | 9篇 |
1994年 | 16篇 |
1993年 | 10篇 |
1992年 | 7篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1981年 | 7篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 10篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 6篇 |
1973年 | 4篇 |
1972年 | 5篇 |
1970年 | 2篇 |
1969年 | 3篇 |
排序方式: 共有422条查询结果,搜索用时 31 毫秒
81.
Sun Y. petersen J. N. Bear J. Clement T. P. Hooker B. S. 《Transport in Porous Media》1999,35(1):49-65
A mathematical model describing microbial transport and growth in a heterogeneous aquifer domain, composed of overlapping subdomains of high-permeability and low-permeability materials, is developed. Each material is conceptually visualized as a continuum which occupies the entire considered spatial aquifer domain. Based on the assumption that advection in the low-permeability domain is negligible, the mathematical model is solved by using a publically available reactive transport code. The importance of modeling microbial transport and growth in such a dual-porosity system is demonstrated through a hypothetical case study. 相似文献
82.
David J. Heldebrant Dr. Clement R. Yonker Dr. Philip G. Jessop Dr. Lam Phan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(31):7619-7627
CO2‐binding organic liquids (CO2BOLs) are mixtures of a base (typically an amidine or guanidine) and an alcohol, and have been shown to reversibly capture and release CO2 with low reaction energies and high gravimetric CO2 capacity. We now report the ability of such liquid blends to chemically bind and release other acid gases such as CS2, COS, and SO2 analogously to CO2. These systems bind with sulfur‐containing acid gases to form colored ionic liquids with new O‐alkylxanthate, O‐alkylthiocarbonyl, and O‐alkylsulfite anions. The capture and thermal stripping of each acid gas from these systems and their applicability towards flue gas desulfurization is discussed. 相似文献
83.
Luke Geever Ciaran Cooney Declan Devine Sinead Devery Michael Nugent Clement Higginbotham 《Macromolecular Symposia》2008,266(1):53-58
Summary: PVP/PNIPAAm copolymers exhibit a temperature sensitive nature that makes them an attractive candidate for controlled drug delivery devices. Diclofenac sodium was added to the monomeric mixture, which included an initiator and crosslinking agent (where appropriate), prior to UV photopolymerisation. It was found that the xerogels retained similar properties as the original samples (not containing drug) at lower levels of drug integration. In all cases, drug dissolution analysis showed that the active agent was released at a slower rate at temperatures above the Lower Critical Solution Temperature (LCST). Interestingly, the drug release trends were almost identical for both the physically and chemically crosslinked hydrogels, when the decrease in transition temperature caused by the incorporated crosslinking agent is taken into consideration. It is believed that both types of copolymers reached a constant maximum swollen weight at a set of temperatures above their transition temperatures. When this swollen plateau is attained, the hydrophilic-hydrophobic interactions are balanced, thus the gel does not swell or shrink further and the drug diffuses out at a constant rate. 相似文献
84.
85.
U. Siodlaczek P. Achenbach J. Ahrens J.R.M. Annand H.-J. Arends R. Beck R. Bilger H. Clement V. Hejny M. Kotulla B. Krusche V. Kuhr R. Leukel J.C. McGeorge V. Metag R. Novotny V. Olmos de León F. Rambo M. Schepkin A. Schmidt I. Seluzhenkov H. Ströher G.J. Wagner Th. Walcher J. Weiß F. Wissmann M. Wolf 《The European Physical Journal A - Hadrons and Nuclei》2001,10(3):365-371
Differential cross-sections for the reactions d (γ,π0)d and d (γ,π0)pn have been measured at MAMI with the TAPS detector setup in the energy range 140 MeV < E
γ < 306 MeV. By use of the Glasgow tagging spectrometer an 0.8 MeV energy resolution for photons incident on the target was
achieved. The π0 missing energy resolution was sufficient for a reliable separation of coherent and incoherent channels. The data for the
break-up channel exhibit very strong final state interaction effects, whereas the observed angular dependence of the inclusive
process d (γ,π0)X is in quantitative agreement with predictions for a quasi-free process. The observed absolute d (γ,π0)X cross-sections, on the other hand, are significantly smaller than predicted by the quasi-free process for E
γ >∼ 250 MeV. Associating this failure with the π0 photoproduction on the neutron would suggest that its cross-section is up to 25% below the presently believed value.
Received: 13 February 2001 / Accepted: 13 April 2001 相似文献
86.
Jonas D. Huyeng Raphael Efinger David Bruge Oliver Doll Roman J. Keding Florian Clement 《Molecules (Basel, Switzerland)》2022,27(17)
The use of sol-gel materials can simplify the industrial fabrication of high-efficiency silicon solar cells if a suitable deposition method is established. In this work, we investigate the possibilities to adapt a borosilicate glass sol-gel to provide a stable screen printing process. This material has previously been used as a boron dopant source for silicon solar cells. We now use an adjusted synthesis process, with an increased gelling time and different additives. This changes the rheological properties (i.e., the elastic and viscous moduli G′ and G″) in a way that avoids the dripping of paste through the screen and that stabilizes the material transfer in subsequent printing steps. Using this synthesis process, we were able to show a printing process with long-term stability of more than 500 prints. When comparing the adjusted to the initial paste, we show that, after thermal treatment, the obtained thin films are very similar in terms of their constitution, with a refractive index between n = 1.47 (initial) and n = 1.55 (adjusted). We also show that they provide the same amount of doping under the tested conditions (950 °C, 30 min), resulting in sheet resistances of R□ = (42.5 ± 2.6) Ω/□ (initial) and R□ = (46.4 ± 3.6) Ω/□ (adjusted). 相似文献
87.
88.
We present a generalization for the procedure of taking Bruck-Reilly extensions, and we characterize abstractly the regular
semigroups which can be obtained in this way. We shall in particular characterize the regular semigroups which can be obtained
by considering the usual Bruck-Reilly extensions. Our procedure generalizes Munn’s construction [3] which in its turn combines
ideas used by Bruck [1] and Reilly [4]. 相似文献
89.
90.
V. J. B. Torres A. M. Stoneham C. J. Sofield A. H. Harker C. F. Clement 《Interface Science》1995,3(2):133-141
Experiments have shown that the early stages of silicon oxidation proceed layer by layer, so that one layer is essentially complete before another develops. Other experiments show that the mechanism does not involve step growth, the most obvious mechanism. We use a new approach to modelling the growth to show that these two observations can be understood when there is a rate-determining step which depends strongly on the local oxide thickness. The rate in question might be the sticking probability, or the rate of incorporation of adsorbed oxygen species into the oxide network. Such mechanisms are possible when transport by an ionic species dominates, contrary to the situation for thicker films. Our modelling suggests the mechanisms are driven by the image interaction, as in earlier suggestions by Stoneham and Tasker, rather than an effect of the electric field central to the Mott-Cabrera mechanism. 相似文献