全文获取类型
收费全文 | 5611篇 |
免费 | 134篇 |
国内免费 | 27篇 |
专业分类
化学 | 3947篇 |
晶体学 | 30篇 |
力学 | 186篇 |
数学 | 862篇 |
物理学 | 747篇 |
出版年
2022年 | 29篇 |
2021年 | 49篇 |
2020年 | 51篇 |
2019年 | 66篇 |
2018年 | 58篇 |
2017年 | 44篇 |
2016年 | 99篇 |
2015年 | 83篇 |
2014年 | 112篇 |
2013年 | 319篇 |
2012年 | 269篇 |
2011年 | 288篇 |
2010年 | 207篇 |
2009年 | 204篇 |
2008年 | 293篇 |
2007年 | 283篇 |
2006年 | 292篇 |
2005年 | 317篇 |
2004年 | 271篇 |
2003年 | 231篇 |
2002年 | 239篇 |
2001年 | 93篇 |
2000年 | 86篇 |
1999年 | 74篇 |
1998年 | 73篇 |
1997年 | 84篇 |
1996年 | 75篇 |
1995年 | 50篇 |
1994年 | 72篇 |
1993年 | 64篇 |
1992年 | 44篇 |
1991年 | 59篇 |
1990年 | 38篇 |
1989年 | 41篇 |
1988年 | 31篇 |
1987年 | 35篇 |
1986年 | 29篇 |
1985年 | 69篇 |
1984年 | 76篇 |
1983年 | 49篇 |
1982年 | 70篇 |
1981年 | 70篇 |
1980年 | 83篇 |
1979年 | 69篇 |
1978年 | 78篇 |
1977年 | 76篇 |
1976年 | 70篇 |
1975年 | 71篇 |
1974年 | 61篇 |
1973年 | 51篇 |
排序方式: 共有5772条查询结果,搜索用时 15 毫秒
1.
Thermodynamic study of transthyretin association (wild‐type and senile forms) with heparan sulfate proteoglycan: pH effect and implication of the reactive histidine residue 下载免费PDF全文
Ambre Geneste Claire André Nadine Magy‐Bertrand Lydie Lethier Gharbi Tijani Yves Claude Guillaume 《Biomedical chromatography : BMC》2015,29(4):514-522
The tetramer destabilization of transthyretin into monomers and its fibrillation are phenomena leading to amyloid deposition. Heparan sulfate proteoglycan (HSPG) has been found in all amyloid deposits. A chromatographic approach was developed to compare binding parameters between wild‐type transthyretin (wtTTR) and an amyloidogenic transthyretin (sTTR). Results showed a greater affinity of sTTR for HSPG at pH 7.4 compared with wtTTR owing to the monomeric form of sTTR. Analysis of the thermodynamic parameters showed that van der Waals interactions were involved at the complex interface for both transthyretin forms. For sTTR, results from the plot representing the number of protons exchanged vs pH showed that the binding mechanism was pH‐dependent with a critical value at a pH 6.5. This observation was due to the protonation of a histidine residue as an imidazolium cation, which was not accessible when TTR was in its tetrameric structure. At pH >6.5, dehydration at the binding interface and several contacts between nonpolar groups of sTTR and HSPG were also coupled to binding for an optimal hydrogen‐bond network. At pH <6.5, the protonation of the His residue from sTTR monomer when pH decreased broke the hydrogen‐bond network, leading to its destabilization and thus producing slight conformational changes in the sTTR monomer structure. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
2.
3.
A new asymmetric synthesis of 2-substituted chiral chromanes has been achieved. The key step is the intramolecular conjugate addition of a phenolic nucleophile on a α,β-unsaturated ester catalyzed by Cinchona alkaloids. The high ee’s obtained with cinchonine and its derivatives have been rationalized by ab initio quantum chemistry calculations of transition state structures. 相似文献
4.
Using a double Suzuki cross-coupling reaction ortho- or para-bromobenzyl bromides are easily transformed into unsymmetrical diaryl (or heteroaryl) methanes 相似文献
5.
Jocelyn Sabatier Serge Poullain Patrick Latteux Jean Luc Thomas Alain Oustaloup 《Nonlinear dynamics》2004,38(1-2):383-400
Robust speed control of a low damped electromechanical system with backlash is studied, controlled load angular speed being not measured. The proposed control strategy combines a Luenberger observer (load angular speed and load torque disturbance estimations) and a robust CRONE controller. The observer provides estimation of the load angular speed and of the disturbance torque applied on the load. Through the computation of only three independent parameters (as many as a PID controller), the CRONE controller permits to ensure the robust speed control of the load in spite of plant parametric variations and speed observation errors. The proposed control strategy is applied to a four mass experimental test bench. 相似文献
6.
Bou-Huot Phe Véronique Bounor-Legare Laurent David Alain Michel 《Journal of Sol-Gel Science and Technology》2004,31(1-3):47-50
We study the synthesis of organic-inorganic hybrids in the molten state of the polymer without solvent, by reactive processing. The synthesis is based in a first step upon the crosslinking of ethylene vinyl acetate copolymer (EVA) through an exchange reaction between the pendant ester groups of EVA and tetrapropoxysilane (TPOS) in presence of dibutyltin oxide (DBTO) as an indispensable catalyst. Then in a second step the hydrolysis-condensation reactions of residual alkoxide groups results in silica network formation, which is covalently bonded with the organic network. An original approach was developed to correlate the evolution of the hydrolysis-condensation reactions through the assessment of propanol by gas chromatography and the evolution of the morphology through SAXS and TEM analysis. Silica-rich domains with a diameter close to 5 nm are obtained. 相似文献
7.
Parabolic Capacity and Soft Measures for Nonlinear Equations 总被引:2,自引:0,他引:2
We first introduce, using a functional approach, the notion of capacity related to the parabolic p-Laplace operator. Then we prove a decomposition theorem for measures (in space and time) that do not charge the sets of null capacity. We apply this result to prove existence and uniqueness of renormalized solutions for nonlinear parabolic initial boundary-value problems with such measures as right-hand side. 相似文献
8.
Alain Bachelot Eric Darrigrand Katherine Mer-Nkonga 《Comptes Rendus Mathematique》2003,336(6):505-510
The aim of this work is to propose an accurate and efficient numerical approximation for high frequency diffraction of electromagnetic waves. In the context of the boundary integral equations presented in F. Collino and B. Després, to be published in J. Comput. Appl. Math., the strategy we propose combines the microlocal discretization (T. Abboud et al., in: Third International Conference on Mathematical Aspects of Wave Propagation Phenomena, SIAM, 1995, pp. 178–187) and the multilevel fast multipole method (J.M. Song, W.C. Chew, Microw. Opt. Tech. Lett. 10 (1) (1995) 14–19). This leads to a numerical method with a reduced complexity, of order O(N4/3ln(N)+NiterN2/3), instead of the complexity O(NiterN2) for a classical numerical iterative solution of integral equations. Computations on an academic geometry show that the new method improves the efficiency, for a solution with a good level of accuracy. To cite this article: A. Bachelot et al., C. R. Acad. Sci. Paris, Ser. I 336 (2003). 相似文献
9.
Recently, Fishbum and Lavalle (1995) and Lefèvre and Utev (1996) have considered some stochastic order relations specific for arithmetic random variables. The present work is concerned with these orderings, together with two other classes of stochastic order relations closely related. First, attention is paid to characterizations and various properties of all these orderings. Then, sufficient conditions of crossing-type for the two new classes of orderings are derived and extrema among discrete random variables are deduced. This is applied in actuarial sciences to obtain new bounds for the classical single life premiums as well as for the probability of ruin in the compound binomial risk model. 相似文献
10.