全文获取类型
收费全文 | 4666篇 |
免费 | 258篇 |
国内免费 | 20篇 |
专业分类
化学 | 3249篇 |
晶体学 | 20篇 |
力学 | 99篇 |
数学 | 645篇 |
物理学 | 931篇 |
出版年
2024年 | 6篇 |
2023年 | 49篇 |
2022年 | 65篇 |
2021年 | 97篇 |
2020年 | 136篇 |
2019年 | 133篇 |
2018年 | 90篇 |
2017年 | 74篇 |
2016年 | 217篇 |
2015年 | 159篇 |
2014年 | 192篇 |
2013年 | 257篇 |
2012年 | 394篇 |
2011年 | 486篇 |
2010年 | 233篇 |
2009年 | 147篇 |
2008年 | 314篇 |
2007年 | 327篇 |
2006年 | 298篇 |
2005年 | 281篇 |
2004年 | 194篇 |
2003年 | 124篇 |
2002年 | 109篇 |
2001年 | 46篇 |
2000年 | 31篇 |
1999年 | 27篇 |
1998年 | 23篇 |
1997年 | 19篇 |
1996年 | 39篇 |
1995年 | 35篇 |
1994年 | 31篇 |
1993年 | 33篇 |
1992年 | 28篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1989年 | 11篇 |
1987年 | 7篇 |
1986年 | 10篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1983年 | 11篇 |
1982年 | 16篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 15篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1976年 | 15篇 |
1974年 | 8篇 |
1973年 | 33篇 |
排序方式: 共有4944条查询结果,搜索用时 31 毫秒
141.
D. Wade Abbott Dallas Thomas Benjamin Pluvinage Alisdair B. Boraston 《Applied biochemistry and biotechnology》2013,171(7):1911-1923
Polysaccharide lyases (PLs) are enzymes that cleave glycosidic linkages in hexuronate polysaccharides, such as homogalacturonan (HG), using a β-elimination mechanism. Traditionally, PL activities on HG have been associated with catalytic calcium cofactors, unusually high pH optima, and arginine Brønstead bases. Recently, however, PL families that harness transition metal cofactors, utilize lysine and histidine Brønstead bases, and display more neutral pH optima have been described. One such family is PL2, which has members found primarily in phytopathogenic (e.g., Dickeya spp. and Pectobacterium spp.) or enteropathogenic (e.g., Yersinia spp.) bacterial species. PL2 is divided into two major subfamilies that are correlated with either an endolytic or exolytic activity. This study has focused on the activity of a PL2 member, which is not classified within either subfamily and helps to illuminate the origin of enzyme activities within the family. In addition, the role of Mg2+ as a preferential catalytic metal for an intracellular PL2 (PaePL2) is described. The implications for the relationship between catalytic metal selectivity and the cellular location of pectate lyase-mediated catalysis are discussed. 相似文献
142.
143.
144.
145.
Benjamin H. Strudwick Mark A. J. Koenis Hans J. Sanders Valentin P. Nicu Sander Woutersen Prof. Wybren Jan Buma 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(54):12560-12566
Vibrational circular dichroism (VCD) studies are reported on a chiral compound in which a fullerene C60 moiety is used as an electron acceptor and local VCD amplifier for an alanine-based peptide chain. Four redox states are investigated in this study, of which three are reduced species that possess low-lying electronic states as confirmed by UV/Vis spectroelectrochemistry. VCD measurements in combination with (TD)DFT calculations are used to investigate (i) how the low-lying electronic states of the reduced species modulate the amplification of VCD signals, (ii) how this amplification depends on the distance between oscillator and amplifier, and (iii) how the spatial extent of the amplifier influences amplification. These results pave the way for further development of tailored molecular VCD amplifiers. 相似文献
146.
147.
Hirzinger Benjamin Adam Christoph Salcher Patrick Oberguggenberger Michael 《Meccanica》2019,54(9):1385-1402
Meccanica - The scope of this paper is to evaluate the performance and computational efficiency of various stochastic simulation methods for a stochastic based reliability assessment of railway... 相似文献
148.
Malte Braack Martin F. Quaas Benjamin Tews Boris Vexler 《Journal of Optimization Theory and Applications》2018,178(3):950-972
The behavior of a fishing fleet and its impact onto the biomass of fish can be described by a nonlinear parabolic diffusion–reaction equation. Looking for an optimal fishing strategy leads to a non-convex optimal control problem with a bilinear control action. In this work, we present such an optimal control formulation, prove its well-posedness and derive first- and second-order optimality conditions. These results provide a basis for tailored finite element discretization as well as for Newton type optimization algorithms. First numerical test problems show typical features as so-called No-Take-Zones and maximal fishing quota (total allowable catches) as parts of an optimal fishing strategy. 相似文献
149.
Benjamin Klemmed Dr. Lucas V. Besteiro Dr. Albrecht Benad Maximilian Georgi Prof. Zhiming Wang Prof. Alexander Govorov Prof. Alexander Eychmüller 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(4):1713-1719
Solar radiation is a versatile source of energy, convertible to different forms of power. A direct path to exploit it is the generation of heat, for applications including passive building heating, but it can also drive secondary energy-conversion steps. We present a novel concept for a hybrid material which is both strongly photo-absorbing and with superior characteristics for the insulation of heat. The combination of that two properties is rather unique, and make this material an optical superheater. To realize such a material, we are combining plasmonic nanoheaters with alumina aerogel. The aerogel has the double function of providing structural support for plasmonic nanocrystals, which serve as nanoheaters, and reducing the diffusion rate of the heat generated by them, resulting in large local temperature increases under a relatively low radiation intensity. This work includes theoretical discussion on the physical mechanisms impacting the system's balanced thermal equilibrium. 相似文献
150.
Benjamin Radel Edme H. Hardy Zorana Djuric Markus Mahlbacher Michael Haist Harald S. Müller 《Magnetic resonance in chemistry : MRC》2019,57(10):836-844
Not only in low-field nuclear magnetic resonance, Laplace inversion is a relevant and challenging topic. Considerable conceptual and technical progress has been made, especially for the inversion of data encoding two decay dimensions. Distortion of spectra by overfitting of even moderate noise is counteracted requiring a priori smooth spectra. In this contribution, we treat the case of simple and fast one-dimensional decay experiments that are repeated many times in a series in order to study the evolution of a sample or process. Incorporating the a priori knowledge that also in the series dimension evolution should be smooth, peak position can be stabilized and resolution improved in the decay dimension. It is explained how the standard one-dimensional regularized Laplace inversion can be extended quite simply in order to include regularization in the series dimension. Obvious improvements compared with series of one-dimensional inversions are presented for simulated as well as experimental data. For the latter, comparison with multiexponential fitting is performed. 相似文献