全文获取类型
收费全文 | 969篇 |
免费 | 44篇 |
国内免费 | 2篇 |
专业分类
化学 | 571篇 |
晶体学 | 11篇 |
力学 | 46篇 |
数学 | 64篇 |
物理学 | 323篇 |
出版年
2023年 | 10篇 |
2022年 | 6篇 |
2021年 | 19篇 |
2020年 | 15篇 |
2019年 | 14篇 |
2018年 | 16篇 |
2017年 | 12篇 |
2016年 | 36篇 |
2015年 | 17篇 |
2014年 | 25篇 |
2013年 | 55篇 |
2012年 | 45篇 |
2011年 | 49篇 |
2010年 | 27篇 |
2009年 | 27篇 |
2008年 | 47篇 |
2007年 | 37篇 |
2006年 | 42篇 |
2005年 | 37篇 |
2004年 | 23篇 |
2003年 | 22篇 |
2002年 | 26篇 |
2001年 | 23篇 |
2000年 | 25篇 |
1999年 | 24篇 |
1998年 | 14篇 |
1997年 | 10篇 |
1996年 | 18篇 |
1995年 | 18篇 |
1994年 | 9篇 |
1993年 | 14篇 |
1992年 | 15篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1989年 | 13篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 14篇 |
1985年 | 8篇 |
1984年 | 15篇 |
1983年 | 10篇 |
1982年 | 21篇 |
1981年 | 12篇 |
1980年 | 16篇 |
1979年 | 12篇 |
1978年 | 16篇 |
1977年 | 12篇 |
1976年 | 13篇 |
1975年 | 5篇 |
1972年 | 5篇 |
排序方式: 共有1015条查询结果,搜索用时 62 毫秒
991.
S. M. Godfrey N. A. Barnes P. Bhattacharyya R. T. A. Halton I. Mushtaq R. G. Pritchard 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4):783-786
Adducts of selenium and tellurium donor molecules with dihalogens, interhalogens, and pseudohalogens exhibit a remarkable structural diversity. Some interesting examples of these materials and key factors influencing their formation, structures, and bonding are discussed. 相似文献
992.
Piotr Berman Arnab Bhattacharyya Elena Grigorescu Sofya Raskhodnikova David P. Woodruff Grigory Yaroslavtsev 《Combinatorica》2014,34(3):255-277
Given a directed graph G=(V, E) and an integer k ≥ 1, a k-transitive-closure spanner (k-TC-spanner) of G is a directed graph H=(V, E H ) that has (1) the same transitive closure as G and (2) diameter at most k. In some applications, the shortcut paths added to the graph in order to obtain small diameter can use Steiner vertices, that is, vertices not in the original graph G. The resulting spanner is called a Steiner transitive-closure spanner (Steiner TC-spanner). Motivated by applications to property reconstruction and access control hierarchies, we concentrate on Steiner TC-spanners of directed acyclic graphs or, equivalently, partially ordered sets. In these applications, the goal is to find a sparsest Steiner k-TC-spanner of a poset G for a given k and G. The focus of this paper is the relationship between the dimension of a poset and the size of its sparsest Steiner TC-spanner. The dimension of a poset G is the smallest d such that G can be embedded into a d-dimensional directed hypergrid via an order-preserving embedding. We present a nearly tight lower bound on the size of Steiner 2-TC-spanners of d- dimensional directed hypergrids. It implies better lower bounds on the complexity of local reconstructors of monotone functions and functions with small Lipschitz constant. The lower bound is derived from an explicit dual solution to a linear programming relaxation of the Steiner 2-TC-spanner problem. We also give an efficient construction of Steiner 2-TC-spanners, of size matching the lower bound, for all low-dimensional posets. Finally, we present a lower bound on the size of Steiner k-TC-spanners of d-dimensional posets. It shows that the best-known construction, due to De Santis et al., cannot be improved significantly. 相似文献
993.
994.
We devise a three-parameter random search strategy to obtain accurate estimates of the large-coupling amplitude and exponent of an observable from its divergent Taylor expansion, known to some desired order. The endeavor exploits the power of fractional calculus, aided by an auxiliary series and subsequent construction of Padé approximants. Pilot calculations on the ground-state energy perturbation series of the octic anharmonic oscillator reveal the spectacular performance. 相似文献
995.
Small‐Angle Neutron Scattering Studies of Hemoglobin Confined Inside Silica Tubes of Varying Sizes
下载免费PDF全文
![点击此处可从《Chemphyschem》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Soumit S. Mandal Dr. Viviana Cristiglio Dr. Peter Lindner Prof. Aninda J. Bhattacharyya 《Chemphyschem》2014,15(2):302-309
In addition to the chemical nature of the surface, the dimensions of the confining host exert a significant influence on confined protein structures; this results in immense biological implications, especially those concerning the enzymatic activities of the protein. This study probes the structure of hemoglobin (Hb), a model protein, confined inside silica tubes with pore diameters that vary by one order of magnitude (≈20–200 nm). The effect of confinement on the protein structure is probed by comparison with the structure of the protein in solution. Small‐angle neutron scattering (SANS), which provides information on protein tertiary and quaternary structures, is employed to study the influence of the tube pore diameter on the structure and configuration of the confined protein in detail. Confinement significantly influences the structural stability of Hb and the structure depends on the Si‐tube pore diameter. The high radius of gyration (Rg) and polydispersity of Hb in the 20 nm diameter Si‐tube indicates that Hb undergoes a significant amount of aggregation. However, for Si‐tube diameters greater or equal to 100 nm, the Rg of Hb is found to be in very close proximity to that obtained from the protein data bank (PDB) reported structure (Rg of native Hb=23.8 Å). This strongly indicates that the protein has a preference for the more native‐like non‐aggregated state if confined inside tubes of diameter greater or equal to 100 nm. Further insight into the Hb structure is obtained from the distance distribution function, p(r), and ab initio models calculated from the SANS patterns. These also suggest that the Si‐tube size is a key parameter for protein stability and structure. 相似文献
996.
Md Raja Sk Arya Bhattacharyya Shuvendu Saha Arpita Brahma Dr. Modhu Sudan Maji 《Angewandte Chemie (International ed. in English)》2023,62(30):e202305258
Annulative π-extension (APEX) reaction has become a powerful tool for the precise synthesis of well-defined polycyclic aromatic hydrocarbons (PAHs) such as nanographene, graphene, and other PAHs possessing unique structure. Herein, an APEX reaction has been realized at the masked bay-region for the efficient and rapid synthesis of valuable PAH, pyrene, bearing substitutions at the most challenging K-region. RhIII-catalyzed ketone-directed C−H activation at the peri-position of a naphthyl-derived ketone, alkyne-insertion, intramolecular nucleophilic attack at the carbonyl-group, dehydration, and aromatization steps occurred in one-pot to effectuate the protocol. Employing this strategy, a two-fold APEX reaction on enantiopure BINOL-derived ketones provided access to axially-chiral bipyrene derivatives. The detailed DFT study to support proposed mechanism, and synthesis of helical PAHs like dipyrenothiophene and dipyrenofuran are other highlights of the present study. 相似文献
997.
Hao Nguyen Tran In Gul Kim Jong Heon Kim Amitava Bhattacharyya Eun-Jae Chung Insup Noh 《Macromolecular bioscience》2023,23(11):2300316
In extrusion-based 3D printing, the use of synthetic polymeric hydrogels can facilitate fabrication of cellularized and implanted scaffolds with sufficient mechanical properties to maintain the structural integrity and physical stress within the in vivo conditions. However, synthetic hydrogels face challenges due to their poor properties of cellular adhesion, bioactivity, and biofunctionality. New compositions of hydrogel inks have been designed to address this limitation. A viscous poly(maleate-propylene oxide)-lipoate-poly(ethylene oxide) (MPLE) hydrogel is recently developed that shows high-resolution printability, drug-controlled release, excellent mechanical properties with adhesiveness, and biocompatibility. In this study, the authors demonstrate that the incorporation of cell-adhesive proteins like gelatin and albumin within the MPLE gel allows printing of biologically functional 3D scaffolds with rapid cell spreading (within 7 days) and high cell proliferation (twofold increase) as compared with MPLE gel only. Addition of proteins (10% w/v) supports the formation of interconnected cell clusters (≈1.6-fold increase in cell areas after 7-day) and spreading of cells in the printed scaffolds without additional growth factors. In in vivo studies, the protein-loaded scaffolds showed excellent biocompatibility and increased angiogenesis without inflammatory response after 4-week implantation in mice, thus demonstrating the promise to contribute to the printable tough hydrogel inks for tissue engineering. 相似文献
998.
Effect of gamma irradiation on X‐ray absorption and photoelectron spectroscopy of Nd‐doped phosphate glass
下载免费PDF全文
![点击此处可从《Journal of synchrotron radiation》网站下载免费的PDF全文](/ch/ext_images/free.gif)
V. N. Rai Parasmani Rajput S. N. Jha D. Bhattacharyya B. N. Raja Shekhar U. P. Deshpande T. Shripathi 《Journal of synchrotron radiation》2016,23(6):1424-1432
X‐ray absorption near‐edge structure (XANES) and X‐ray photoelectron spectroscopy (XPS) of Nd‐doped phosphate glasses have been studied before and after gamma irradiation. The intensity and the location of the white line peak of the L3‐edge XANES of Nd are found to be dependent on the ratio O/Nd in the glass matrix. Gamma irradiation changes the elemental concentration of atoms in the glass matrix, which affects the peak intensity of the white line due to changes in the covalence of the chemical bonds with Nd atoms in the glass (structural changes). Sharpening of the Nd 3d5/2 peak profile in XPS spectra indicates a deficiency of oxygen in the glasses after gamma irradiation, which is supported by energy‐dispersive X‐ray spectroscopy measurements. The ratio of non‐bridging oxygen to total oxygen in the glass after gamma radiation has been found to be correlated to the concentration of defects in the glass samples, which are responsible for its radiation resistance as well as for its coloration. 相似文献
999.
Adhikari A Dey S Mandal U Das DK Ghosh S Bhattacharyya K 《The journal of physical chemistry. B》2008,112(11):3575-3580
Solvation dynamics of coumarin 480 (C480) in the secondary aggregate of a bile salt (sodium deoxycholate, NaDC) is studied using femtosecond up-conversion. The secondary aggregate resembles a long (approximately 40 A) hollow cylinder with a central water-filled tunnel. Different regions of the aggregate are probed by variation of the excitation wavelength (lambdaex) from 375 to 435 nm. The emission maximum of C480 displays an 8 nm red shift as the lambdaex increases from 345 to 435 nm. The 8 nm red edge excitation shift (REES) suggests that the probe (C480) is distributed over regions of varied polarity. Excitation at a short wavelength (375 nm) preferentially selects the probe molecule in the buried locations and exhibits slow dynamics with a major (84%) slow component (3500 ps) and a small (16%) contribution of the ultrafast component (2.5 ps). Excitation at lambdaex=435 nm (red end) corresponds to the exposed sites where solvation dynamics is very fast with a major (73%) ultrafast component (相似文献
1000.
Shiva K Rajendra HB Subrahmanyam KS Bhattacharyya AJ Rao CN 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(15):4489-4494
On the wire: Mesoporous tin dioxide (SnO(2)) wired with very low amounts (≤1?%) of reduced graphene oxide (rGO) exhibits a remarkable improvement in lithium-ion battery performance over bare mesoporous or solid nanoparticles of SnO(2). Reversible lithium intercalation into SnO(2)/SnO over several cycles was demonstrated in addition to conventional reversible lithium storage by an alloying reaction. 相似文献