首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   87238篇
  免费   2145篇
  国内免费   1778篇
化学   30975篇
晶体学   1005篇
力学   7226篇
综合类   121篇
数学   33056篇
物理学   18778篇
  2023年   276篇
  2022年   325篇
  2021年   372篇
  2020年   505篇
  2019年   496篇
  2018年   10770篇
  2017年   10539篇
  2016年   6478篇
  2015年   1332篇
  2014年   840篇
  2013年   1008篇
  2012年   4624篇
  2011年   11267篇
  2010年   6141篇
  2009年   6578篇
  2008年   7173篇
  2007年   9292篇
  2006年   706篇
  2005年   1742篇
  2004年   1835篇
  2003年   2247篇
  2002年   1265篇
  2001年   453篇
  2000年   463篇
  1999年   328篇
  1998年   327篇
  1997年   260篇
  1996年   341篇
  1995年   242篇
  1994年   177篇
  1993年   196篇
  1992年   153篇
  1991年   134篇
  1990年   127篇
  1989年   133篇
  1988年   112篇
  1987年   104篇
  1986年   101篇
  1985年   95篇
  1984年   84篇
  1983年   78篇
  1982年   62篇
  1981年   54篇
  1980年   65篇
  1979年   71篇
  1978年   51篇
  1973年   57篇
  1914年   45篇
  1909年   41篇
  1908年   40篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Transport in Porous Media - Membrane filtration of feed containing multiple species of particles is a common process in the industrial setting. In this work, we propose a model for filtration of a...  相似文献   
2.
We report, for the first time, a detailed crystallographic study of the supramolecular arrangement for a set of zinc(II) Schiff base complexes containing the ligand 2,6-bis((E)-((2-(dimethylamino)ethyl)imino)methyl)-4-R-phenol], where R=methyl/tert-butyl/chloro. The supramolecular study acts as a pre-screening tool for selecting the compartmental ligand R of the Schiff base for effective binding with a targeted protein, bovine serum albumin (BSA). The most stable hexagonal arrangement of the complex [Zn − Me] (R=Me) stabilises the ligand with the highest FMO energy gap (ΔE=4.22 eV) and lowest number of conformations during binding with BSA. In contrast, formation of unstable 3D columnar vertebra for [Zn − Cl] (R=Cl) tend to activate the system with lowest FMO gap (3.75 eV) with highest spontaneity factor in molecular docking. Molecular docking analyses reported in terms of 2D LigPlot+ identified site A, a cleft of domains IB, IIIA and IIIB, as the most probable protein binding site of BSA. Arg144, Glu424, Ser428, Ile455 and Lys114 form the most probable interactions irrespective of the type of compartmental ligands R of the Schiff base whereas Arg185, Glu519, His145, Ile522 act as the differentiating residues with ΔG=−7.3 kcal mol−1.  相似文献   
3.
Cai  Peng  Yue  Xiaokui  Wang  Mingming  Cui  Yao 《Nonlinear dynamics》2022,108(3):2309-2322
Nonlinear Dynamics - A capacitive micromachined ultrasonic transducer (CMUT) due to many benefits is being considered as an imaging and therapeutic technology recently. The critical challenge is to...  相似文献   
4.
We investigate the possibility of phantom crossing in the dark energy sector and the solution for the Hubble tension between early and late universe observations. We use robust combinations of different cosmological observations, namely the Cosmic Microwave Background (CMB), local measurement of Hubble constant (H0), Baryon Acoustic Oscillation (BAO) and SnIa for this purpose. For a combination of CMB+BAO data that is related to early universe physics, phantom crossing in the dark energy sector was confirmed at a 95% confidence level and we obtained the constraint H0=71.03.8+2.9 km/s/Mpc at a 68% confidence level, which is in perfect agreement with the local measurement by Riess et al. We show that constraints from different combinations of data are consistent with each other and all of them are consistent with phantom crossing in the dark energy sector. For the combination of all data considered, we obtained the constraint H0=70.25±0.78 km/s/Mpc at a 68% confidence level and the phantom crossing happening at the scale factor am=0.8510.031+0.048 at a 68% confidence level.  相似文献   
5.
Xu  Fei  Xie  Hehu  Xie  Manting  Yue  Meiling 《BIT Numerical Mathematics》2021,61(2):645-663
BIT Numerical Mathematics - In this paper, a new kind of multigrid method is proposed for the ground state solution of Bose–Einstein condensates based on Newton iteration scheme. Instead of...  相似文献   
6.
Yue  Feilong  Li  Peichao  Zhao  Changying 《Transport in Porous Media》2021,136(2):639-655
Transport in Porous Media - This paper numerically investigates the heat transfer performance of thermally developing non-Darcy forced convection in a fluid-saturated porous medium tube under...  相似文献   
7.
求全局最优化问题的填充函数算法被提出以来,参数的选取和调整一直是制约算法有效性的因素。如何在实际的计算过程中选取合适的参数,直接影响和决定了运算速度和效率。因此,构造不含参数的填充函数就显得极为重要。提出一个新的无参数的填充函数,对其理论性质进行了分析,并给出相应的填充函数算法,数值计算验证了算法的有效性。  相似文献   
8.
Measuring angles in the Euclidean plane is a well-known topic, but for general normed planes there exists a variety of different concepts. These can be of a special kind, e.g. also preserving special orthogonality types. But these concepts are no angle measures in the sense of measure theory since they are not additive. This motivates us to define a new angle measure for normed planes that is in fact a measure in the sense of measure theory. Furthermore, we look at related types of rotation and reflection.  相似文献   
9.
We analyze isolated resonance curves (IRCs) in single-degree-of-freedom systems possessing nonlinear damping. Through the combination of singularity theory and the averaging method, the onset and merging of IRCs, which coincide to isola and simple bifurcation singularities, respectively, can be analytically predicted. Numerical simulations confirm the accuracy of the analytical developments. Another important finding of this paper is that we unveil a geometrical connection between the topology of the damping force and IRCs. Specifically, we demonstrate that extremas and zeros of the damping force correspond to the appearance and merging of IRCs. Considering a damping force possessing several minima and maxima confirms the general validity of the analytical result. It also evidences a very complex scenario for which different IRCs are created, co-exist and then merge together to form a super IRC which eventually merges with the main resonance peak.  相似文献   
10.
We give the parameter version of a localization theorem for the Bergman metric near the boundary points of strictly pseudoconvex domains. The approximation theorem for square integrable holomorphic functions on such domains in the spirit of Graham-Kerzman is proved in the hereby paper, as well.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号