全文获取类型
收费全文 | 3808篇 |
免费 | 448篇 |
国内免费 | 406篇 |
专业分类
化学 | 508篇 |
晶体学 | 10篇 |
力学 | 379篇 |
综合类 | 98篇 |
数学 | 3009篇 |
物理学 | 658篇 |
出版年
2024年 | 4篇 |
2023年 | 33篇 |
2022年 | 49篇 |
2021年 | 80篇 |
2020年 | 99篇 |
2019年 | 90篇 |
2018年 | 95篇 |
2017年 | 109篇 |
2016年 | 130篇 |
2015年 | 83篇 |
2014年 | 159篇 |
2013年 | 282篇 |
2012年 | 165篇 |
2011年 | 172篇 |
2010年 | 168篇 |
2009年 | 229篇 |
2008年 | 272篇 |
2007年 | 231篇 |
2006年 | 250篇 |
2005年 | 221篇 |
2004年 | 160篇 |
2003年 | 177篇 |
2002年 | 159篇 |
2001年 | 164篇 |
2000年 | 164篇 |
1999年 | 150篇 |
1998年 | 138篇 |
1997年 | 117篇 |
1996年 | 88篇 |
1995年 | 73篇 |
1994年 | 44篇 |
1993年 | 24篇 |
1992年 | 27篇 |
1991年 | 37篇 |
1990年 | 15篇 |
1989年 | 19篇 |
1988年 | 18篇 |
1987年 | 10篇 |
1986年 | 13篇 |
1985年 | 26篇 |
1984年 | 23篇 |
1983年 | 12篇 |
1982年 | 17篇 |
1981年 | 18篇 |
1980年 | 11篇 |
1979年 | 10篇 |
1978年 | 6篇 |
1977年 | 10篇 |
1976年 | 3篇 |
1975年 | 2篇 |
排序方式: 共有4662条查询结果,搜索用时 39 毫秒
121.
Explicit and partly sharp estimates are given of integrals over the square of Bessel functions with an integrable weight which can be singular at the origin. They are uniform with respect to the order of the Bessel functions and provide explicit bounds for some smoothing estimates as well as for the L2 restrictions of Fourier transforms onto spheres in which are independent of the radius of the sphere. For more special weights these restrictions are shown to be Hölder continuous with a Hölder constant having this independence as well. To illustrate the use of these results a uniform resolvent estimate of the free Dirac operator with mass in dimensions is derived. 相似文献
122.
Dr. Antoine Nitelet Dr. Damien Thevenet Dr. Bruno Schiavi Dr. Christophe Hardouin Dr. Jean Fournier Dr. Rodolphe Tamion Prof. Dr. Xavier Pannecoucke Prof. Dr. Philippe Jubault Prof. Dr. Thomas Poisson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(13):3262-3266
The copper-photocatalyzed borylation of aryl, heteroaryl, vinyl and alkyl halides (I and Br) was reported. The reaction proceeded using a new heteroleptic Cu complex under irradiation with blue LEDs, giving the corresponding boronic-acid esters in good to excellent yields. The reaction was extended to continuous-flow conditions to allow an easy scale-up. The mechanism of the reaction was studied and a mechanism based on a reductive quenching (CuI/CuI*/Cu0) was suggested. 相似文献
123.
124.
《佛山科学技术学院》2014,6(4):435-450
In the present paper, self-adjoint operator and completely continuous operator on soft inner product spaces have been introduced and some basic properties of such operators are studied. 相似文献
125.
Continuous‐Flow Microwave Synthesis of Metal–Organic Frameworks: A Highly Efficient Method for Large‐Scale Production 下载免费PDF全文
Dr. Marco Taddei Daniel Antti Steitz Prof. Dr. Jeroen Anton van Bokhoven Dr. Marco Ranocchiari 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(10):3245-3249
Metal–organic frameworks are having a tremendous impact on novel strategic applications, with prospective employment in industrially relevant processes. The development of such processes is strictly dependent on the ability to generate materials with high yield efficiency and production rate. We report a versatile and highly efficient method for synthesis of metal–organic frameworks in large quantities using continuous flow processing under microwave irradiation. Benchmark materials such as UiO‐66, MIL‐53(Al), and HKUST‐1 were obtained with remarkable mass, space–time yields, and often using stoichiometric amounts of reactants. In the case of UiO‐66 and MIL‐53(Al), we attained unprecedented space–time yields far greater than those reported previously. All of the syntheses were successfully extended to multi‐gram high quality products in a matter of minutes, proving the effectiveness of continuous flow microwave technology for the large scale production of metal–organic frameworks. 相似文献
126.
We discuss the motion of substance in a channel containing nodes of a network. Each node of the channel can exchange substance with: (i) neighboring nodes of the channel, (ii) network nodes which do not belong to the channel, and (iii) environment of the network. The new point in this study is that we assume possibility for exchange of substance among flows of substance between nodes of the channel and: (i) nodes that belong to the network but do not belong to the channel and (ii) environment of the network. This leads to an extension of the model of motion of substance and the extended model contains previous models as particular cases. We use a discrete-time model of motion of substance and consider a stationary regime of motion of substance in a channel containing a finite number of nodes. As results of the study, we obtain a class of probability distributions connected to the amount of substance in nodes of the channel. We prove that the obtained class of distributions contains all truncated discrete probability distributions of discrete random variable which can take values . Theory for the case of a channel containing infinite number of nodes is presented in Appendix A. The continuous version of the discussed discrete probability distributions is described in Appendix B. The discussed extended model and obtained results can be used for the study of phenomena that can be modeled by flows in networks: motion of resources, traffic flows, motion of migrants, etc. 相似文献
127.
小行星捕获对研究行星起源、地球生命来源、防御小行星撞击地球和开采行星矿产资源具有重要的意义。由于现有的推进器能力不足,小行星捕获任务中优化小行星捕获所需要的速度增量是任务成败的关键。本文分别从利用引力辅助轨道优化、连续小推力轨迹优化、小行星捕获任务轨道优化设计及小行星临时捕获等4 个方向介绍小行星捕获轨道优化方面国内外研究进展及现状。基于对上述研究现状的分析,尝试展望小行星捕获轨道优化研究的未来发展趋势。 相似文献
128.
129.
In this article, we study for the ‐realization of the vector‐valued Schrödinger operator . Using a noncommutative version of the Dore–Venni theorem due to Monniaux and Prüss, we prove that the ‐realization of , defined on the intersection of the natural domains of the differential and multiplication operators which form , generates a strongly continuous contraction semigroup on . We also study additional properties of the semigroup such as extension to L1, positivity, ultracontractivity and prove that the generator has compact resolvent. 相似文献
130.
A mixed hp FEM for the approximation of fourth‐order singularly perturbed problems on smooth domains
P. Constantinou S. Franz L. Ludwig C. Xenophontos 《Numerical Methods for Partial Differential Equations》2019,35(1):114-127
We consider fourth‐order singularly perturbed problems posed on smooth domains and the approximation of their solution by a mixed Finite Element Method on the so‐called Spectral Boundary Layer Mesh. We show that the method converges uniformly, with respect to the singular perturbation parameter, at an exponential rate when the error is measured in the energy norm. Numerical examples illustrate our theoretical findings. 相似文献