全文获取类型
收费全文 | 369篇 |
免费 | 21篇 |
专业分类
化学 | 242篇 |
晶体学 | 3篇 |
力学 | 6篇 |
数学 | 40篇 |
物理学 | 99篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 11篇 |
2021年 | 9篇 |
2020年 | 17篇 |
2019年 | 13篇 |
2018年 | 18篇 |
2017年 | 16篇 |
2016年 | 33篇 |
2015年 | 12篇 |
2014年 | 16篇 |
2013年 | 25篇 |
2012年 | 32篇 |
2011年 | 32篇 |
2010年 | 16篇 |
2009年 | 6篇 |
2008年 | 16篇 |
2007年 | 13篇 |
2006年 | 20篇 |
2005年 | 15篇 |
2004年 | 8篇 |
2003年 | 10篇 |
2002年 | 4篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1981年 | 1篇 |
1975年 | 1篇 |
1956年 | 2篇 |
1939年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有390条查询结果,搜索用时 31 毫秒
131.
132.
Motivated by questions about square-free monomial ideals in polynomial rings, in 2010 Francisco et al. conjectured that for every positive integer k and every k-critical (i.e., critically k -chromatic) graph, there is a set of vertices whose replication produces a (k+1)-critical graph. (The replication of a set W of vertices of a graph is the operation that adds a copy of each vertex w in W, one at a time, and connects it to w and all its neighbours.) 相似文献
133.
Amir Reza Sadrolhosseini Mohd Maarof Moksin W. Mahmood Mat Yunus Zainal Abidin Talib Mahnaz M. Abdi 《Optical Review》2011,18(4):331-337
Copper corrosion is one of the important parameters used for evaluating the quality of biodiesel. In this work, a polypyrrole-chitosan
sensing layer was utilized for the detection of Cu2+ in biodiesel using the surface plasmon resonance technique. With the sensitivity of this sensor being about 0.1 ppm, different
corrosion levels could be recognized in samples that were classified as class 1a according to the standard copper strip test. 相似文献
134.
A time-domain model of sound wave propagation in the branching airways of the subglottal system is presented. The model is formulated as an extension to an acoustic transmission-line modeling scheme originally developed for simulating the supraglottal system in the time-domain during speech production [Maeda (1982). Speech Commun. 1, 199-229; Mokhtari et al. (2008). Speech Commun. 50, 179-190]. The approach allows for predictions of time-varying acoustic pressure and volume velocity at any point along the various generations of subglottal airways from trachea to alveoli. In addition, the model can be configured so that its overall structure simulates different geometric forms, including airways that branch in a symmetric or asymmetric pattern. Three subglottal configurations, two symmetric and one asymmetric, were represented based on reported anatomical dimensions of the subglottal airways. Estimates of the acoustic input impedances of these subglottal configurations revealed resonant characteristics similar to those found in the previous studies. Simulations of voiced sound propagation into the subglottal airways, achieved by coupling the subglottal model to a two-mass vocal fold model and a supraglottal tract configured for different vowels, yielded predictions of time-domain sound pressure waveforms below the vocal folds that compare favorably to previous measurements in human subjects. 相似文献
135.
Temporal effects in the growth of networks 总被引:1,自引:0,他引:1
We show that to explain the growth of the citation network by preferential attachment (PA), one has to accept that individual nodes exhibit heterogeneous fitness values that decay with time. While previous PA-based models assumed either heterogeneity or decay in isolation, we propose a simple analytically treatable model that combines these two factors. Depending on the input assumptions, the resulting degree distribution shows an exponential, log-normal or power-law decay, which makes the model an apt candidate for modeling a wide range of real systems. 相似文献
136.
Aqueous Self‐Assembly and Cation Selectivity of Cobaltabisdicarbollide Dianionic Dumbbells
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Màrius Tarrés Prof. Clara Viñas Patricia González‐Cardoso Dr. Mikko M. Hänninen Prof. Reijo Sillanpää Vladimír Ďorďovič Dr. Mariusz Uchman Prof. Francesc Teixidor Dr. Pavel Matějíček 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(22):6786-6794
The anion [3,3′‐Co(C2B9H11)2]? ([COSAN]?) produces aggregates in water. These aggregates are interpreted to be the result of C?H???H?B interactions. It is possible to generate aggregates even after the incorporation of additional functional groups into the [COSAN]? units. The approach is to join two [COSAN]? anions by a linker that can adapt itself to act as a crown ether. The linker has been chosen to have six oxygen atoms, which is the ideal number for K+ selectivity in crown ethers. The linker binds the alkaline metal ions with different affinities; thus showing a distinct degree of selectivity. The highest affinity is shown towards K+ from a mixture containing Li+, Na+, K+, Rb+ and Cs+; this can be indicative of pseudo‐crown ether performance of the dumbbell. One interesting possibility is that the [COSAN]? anions at the two ends of the linker can act as a hook‐and‐loop fastener to close the ring. This facet is intriguing and deserves further consideration for possible applications. The distinct affinity towards alkaline metal ions is corroborated by solubility studies and isothermal calorimetry thermograms. Furthermore, cryoTEM micrographs, along with light scattering results, reveal the existence of small self‐assemblies and compact nanostructures ranging from spheres to single‐/multi‐layer vesicles in aqueous solutions. The studies reported herein show that these dumbbells can have different appearances, either as molecules or aggregates, in water or lipophilic phases; this offers a distinct model as drug carriers. 相似文献
137.
The maxima and minima of Neumann eigenfunctions of thin tubular neighbourhoods of curves on surfaces are located in terms of the maxima and minima of Neumann eigenfunctions of the underlying curves. In particular, the hot spots conjecture for a new large class of domains (possibly non-convex and non-Euclidean) is proved. 相似文献
138.
Alkaline solid polymer electrolyte films have been prepared by the solvent-casting method. Gamma radiation treatment and propylene
carbonate plastisizer were used to improve the ionic conductivity of the electrolytes at ambient temperature. The structure
of the irradiated electrolytes changes from semi-crystalline to amorphous, indicating that the crosslinking of the polymer
has been achieved at a dose of 200 kGy. The ionic conductivity at room temperature of PVA/KOH blend increases from 10−7 to 10−3 Scm−1 after the PVA crosslinking and when the plasticizer concentration was increased from 20 to 30%.
Paper presented at the International Conference on Functional Materials and Devices 2005, Kuala Lumpur, Malaysia, June 6 –
8, 2005. 相似文献
139.
Neutron Activation Analysis (NAA) and Inductively Coupled Plasma (ICP) spectrometry were used to determine the concentration of trace metals in marine bivalveAnadara
granosa. A total of 11 elements: Mg, Cl, Mn, K, Se, Br, Zn, Co, Fe, Rb, Cd and Cu were detected. Analyses were performed to examine the relationship between metal concentration and body weight. Results from both techniques show linear relationship between total metal concentration and body weight. 相似文献
140.
Camacho C Matías JC Cao R Matos M Chico B Hernández J Longo MA Sanromán MA Villalonga R 《Langmuir : the ACS journal of surfaces and colloids》2008,24(15):7654-7657
A new sensor design is reported for the construction of an amperometric enzyme biosensor toward H (2)O(2). It was based in the supramolecular immobilization of alternating layers of horseradish peroxidase (either modified with 1-adamantane or beta-cyclodextrin-branched carboxymethylcellulose residues) on Au electrodes coated with polythiolated beta-cyclodextrin polymer. The analytical response of the electrodes, using 1 mM hydroquinone as an electrochemical mediator, increases when the number of enzyme layers increases. The biosensor having three enzyme layers showed a sensitivity of 720 microA/M cm (2) and a detection limit of 2 microM and retained 96% of its initial activity after 30 days of storage. The host-guest supramolecular nature of the immobilization method was confirmed by cyclic voltammetry. 相似文献