全文获取类型
收费全文 | 15023篇 |
免费 | 308篇 |
国内免费 | 83篇 |
专业分类
化学 | 9317篇 |
晶体学 | 159篇 |
力学 | 491篇 |
数学 | 2297篇 |
物理学 | 3150篇 |
出版年
2022年 | 91篇 |
2021年 | 107篇 |
2020年 | 144篇 |
2019年 | 151篇 |
2018年 | 104篇 |
2017年 | 99篇 |
2016年 | 194篇 |
2015年 | 213篇 |
2014年 | 265篇 |
2013年 | 716篇 |
2012年 | 617篇 |
2011年 | 710篇 |
2010年 | 426篇 |
2009年 | 428篇 |
2008年 | 685篇 |
2007年 | 708篇 |
2006年 | 707篇 |
2005年 | 636篇 |
2004年 | 592篇 |
2003年 | 506篇 |
2002年 | 492篇 |
2001年 | 292篇 |
2000年 | 299篇 |
1999年 | 203篇 |
1998年 | 171篇 |
1997年 | 168篇 |
1996年 | 227篇 |
1995年 | 182篇 |
1994年 | 240篇 |
1993年 | 260篇 |
1992年 | 231篇 |
1991年 | 163篇 |
1990年 | 194篇 |
1989年 | 188篇 |
1988年 | 146篇 |
1987年 | 174篇 |
1986年 | 158篇 |
1985年 | 257篇 |
1984年 | 236篇 |
1983年 | 152篇 |
1982年 | 205篇 |
1981年 | 200篇 |
1980年 | 230篇 |
1979年 | 208篇 |
1978年 | 211篇 |
1977年 | 191篇 |
1976年 | 201篇 |
1975年 | 166篇 |
1974年 | 170篇 |
1973年 | 186篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Dr. Chenge Li Dr. Alison G. Tebo Marion Thauvin Marie-Aude Plamont Prof. Dr. Michel Volovitch Dr. Xavier Morin Prof. Dr. Sophie Vriz Prof. Dr. Arnaud Gautier 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(41):18073-18079
Far-red emitting fluorescent labels are highly desirable for spectral multiplexing and deep tissue imaging. Here, we describe the generation of frFAST (far-red Fluorescence Activating and absorption Shifting Tag), a 14-kDa monomeric protein that forms a bright far-red fluorescent assembly with (4-hydroxy-3-methoxy-phenyl)allylidene rhodanine (HPAR-3OM). As HPAR-3OM is essentially non-fluorescent in solution and in cells, frFAST can be imaged with high contrast in presence of free HPAR-3OM, which allowed the rapid and efficient imaging of frFAST fusions in live cells, zebrafish embryo/larvae, and chicken embryos. Beyond enabling the genetic encoding of far-red fluorescence, frFAST allowed the design of a far-red chemogenetic reporter of protein–protein interactions, demonstrating its great potential for the design of innovative far-red emitting biosensors. 相似文献
2.
3.
4.
5.
6.
7.
Peter T. Smith Younghoon Kim Dr. Bahiru Punja Benke Prof. Kimoon Kim Prof. Christopher J. Chang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(12):4932-4937
We report a supramolecular strategy for promoting the selective reduction of O2 for direct electrosynthesis of H2O2. We utilized cobalt tetraphenylporphyrin (Co-TPP), an oxygen reduction reaction (ORR) catalyst with highly variable product selectivity, as a building block to assemble the permanently porous supramolecular cage Co-PB-1(6) bearing six Co-TPP subunits connected through twenty-four imine bonds. Reduction of these imine linkers to amines yields the more flexible cage Co-rPB-1(6). Both Co-PB-1(6) and Co-rPB-1(6) cages produce 90–100 % H2O2 from electrochemical ORR catalysis in neutral pH water, whereas the Co-TPP monomer gives a 50 % mixture of H2O2 and H2O. Bimolecular pathways have been implicated in facilitating H2O formation, therefore, we attribute this high H2O2 selectivity to site isolation of the discrete molecular units in each supramolecule. The ability to control reaction selectivity in supramolecular structures beyond traditional host–guest interactions offers new opportunities for designing such architectures for a broader range of catalytic applications. 相似文献
8.
Sensitivity analysis is a mathematical tool, first developed for optimization methods, which aim is to characterize a system response through the variations of its output parameters following modifications imposed on the input parameters of the system. Such an analysis may quickly become laborious when the thermal model under consideration is complex or the number of input parameters is high. In this paper, we develop a mathematical model to analyse the heat exchanges in four different types of solar air collectors. When building this thermal model we show that for each collector, at quasi-steady state, the energy balance equations of the components of the collector cascade into a single first-order non-linear differential equation that is able to predict the thermal behaviour of the collector. Our heat transfer model clearly demonstrates the existence of an important dimensionless parameter, referred to as the thermal performance factor of the collector, that compares the useful thermal energy which can be extracted from the heater to the overall thermal losses of that collector for a given set of input parameters. A sensitivity analysis of our thermal model has been performed for the most significant input parameters such as the incident solar irradiation, the inlet fluid temperature, the air mass flow rate, the depth of the fluid channel, the number and nature of the transparent covers in order to measure the impact of each of these parameters on our model. An important result which can be drawn from this study is that the heat transfer model developed is robust enough to be used for thermal design studies of most known flat plate solar air heaters, but also of flat plate solar water collectors and linear solar concentrators. 相似文献
9.
10.
Abstract
In this note, we consider a Frémond model of shape memory alloys. Let us imagine a piece of a shape memory alloy which is
fixed on one part of its boundary, and assume that forcing terms, e.g., heat sources and external stress on the remaining
part of its boundary, converge to some time-independent functions, in appropriate senses, as time goes to infinity. Under
the above assumption, we shall discuss the asymptotic stability for the dynamical system from the viewpoint of the global
attractor. More precisely, we generalize the paper [12] dealing with the one-dimensional case. First, we show the existence
of the global attractor for the limiting autonomous dynamical system; then we characterize the asymptotic stability for the
non-autonomous case by the limiting global attractor.
* Project supported by the MIUR-COFIN 2004 research program on “Mathematical Modelling and Analysis of Free Boundary Problems”. 相似文献