全文获取类型
收费全文 | 5299篇 |
免费 | 479篇 |
国内免费 | 691篇 |
专业分类
化学 | 1653篇 |
晶体学 | 13篇 |
力学 | 362篇 |
综合类 | 149篇 |
数学 | 3574篇 |
物理学 | 718篇 |
出版年
2023年 | 54篇 |
2022年 | 91篇 |
2021年 | 136篇 |
2020年 | 147篇 |
2019年 | 128篇 |
2018年 | 115篇 |
2017年 | 149篇 |
2016年 | 212篇 |
2015年 | 129篇 |
2014年 | 237篇 |
2013年 | 367篇 |
2012年 | 276篇 |
2011年 | 323篇 |
2010年 | 310篇 |
2009年 | 344篇 |
2008年 | 361篇 |
2007年 | 387篇 |
2006年 | 355篇 |
2005年 | 317篇 |
2004年 | 247篇 |
2003年 | 255篇 |
2002年 | 209篇 |
2001年 | 185篇 |
2000年 | 136篇 |
1999年 | 137篇 |
1998年 | 123篇 |
1997年 | 117篇 |
1996年 | 84篇 |
1995年 | 63篇 |
1994年 | 63篇 |
1993年 | 48篇 |
1992年 | 45篇 |
1991年 | 32篇 |
1990年 | 29篇 |
1989年 | 21篇 |
1988年 | 26篇 |
1987年 | 20篇 |
1986年 | 19篇 |
1985年 | 27篇 |
1984年 | 17篇 |
1983年 | 9篇 |
1982年 | 29篇 |
1981年 | 17篇 |
1980年 | 17篇 |
1979年 | 16篇 |
1978年 | 9篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1973年 | 5篇 |
1972年 | 5篇 |
排序方式: 共有6469条查询结果,搜索用时 218 毫秒
1.
宋显花 《数学的实践与认识》2021,(3):182-185
设B(X)是维数大于等于3的复Banach空间X上有界线性算子全体构成的代数.设A∈B(X),若Ax=x,则称x∈X是算子A的固定点.Fix(A)表示A的所有固定点的集合.本文刻画了B(X)上保持算子的Jordan积的固定点的满射. 相似文献
2.
本文通过固结磨料球与KDP晶体对磨的单因素试验探究固结磨料球中反应物种类、磨粒浓度、反应物浓度、基体硬度对摩擦系数、磨痕截面积和磨痕处粗糙度的影响,试验结果表明:KHCO3固结磨料球对磨后磨痕对称性好,磨痕处的粗糙度值低;磨痕截面积随磨粒和反应物浓度的增加而增大,随基体硬度的增大而降低;磨痕处粗糙度随磨粒和反应物浓度的增加先降低后上升,随基体硬度的增大先上升后降低;摩擦系数受磨粒和反应物浓度影响不明显,随基体硬度的增大而降低。选择KHCO3作为反应物,Ⅰ基体,磨粒浓度为基体质量的100%,反应物浓度为15%制备固结磨料球与KDP晶体对磨后的磨痕轮廓对称度好且磨痕处粗糙度值低,以该组分制备固结磨料垫干式抛光KDP晶体,可实现晶体表面粗糙度Sa值为18.50 nm,材料去除率为130 nm/min的高效精密加工。 相似文献
3.
SongIl Ri 《Indagationes Mathematicae》2018,29(3):962-971
The aim of this paper is to present a new idea to construct the nonlinear fractal interpolation function, in which we exploit the Matkowski and the Rakotch fixed point theorems. Our technique is different from the methods presented in the previous literatures. 相似文献
4.
Phan Quoc Khanh 《Numerical Functional Analysis & Optimization》2018,39(1):100-125
We propose a definition of a generalized type of Knaster–Kuratowski–Mazurkiewicz (KKM) mappings, called a weak T-KKM mapping, and a corresponding weak KKM property. A new extension of the Fan–Glicksberg fixed-point theorem is established. Sufficient conditions for the existence of a continuous selection, a fixed point of a composition, and a coincidence point are also provided. Then, we use the obtained results to study the existence of solutions to various optimization-related problems. Discussions and detailed examples are included as well to compare our results with existing ones and to explain their advantages in many situations. 相似文献
5.
6.
在完备的度量空间中,讨论了一类新型的非线性压缩映射ρ(Tx,Ty)≤a(ρ(x,y))ρ(x,Tx)+b(ρ(x,y))ρ(y,Ty)+c(ρ(x,y))ρ(x,y)通过构造迭代序列,指出该映射的不动点的存在性和唯一性,并给出相应的误差估计式,拓展和改进了有关文献的范围. 相似文献
7.
This study investigated the effects of different treatment of alkaline pH-shifting on milk protein concentrate (MPC), micellar casein concentrate (MCC) and whey protein isolate (WPI) assisted by the same ultrasound conditions, including changes in the physicochemical properties, solubility and foaming capacity. The solubility of milk proteins had a significant increase with gradual enhancement of ultrasound-assisted alkaline pH-shifting (p < 0.05), especially for MCC up to 99.50 %. Also, treatment made a significant decline in the particle size of MPC and MCC, as well as the turbidity of the proteins (p < 0.05). The foaming capacity of MPC, MCC, and WPI was all improved, especially at pH 11, and at this pH, the milk protein also showed the highest surface hydrophobicity. The best foaming capacity at pH 11 was the result of the combined effect of particle size, potential, protein conformation, solubility, and surface hydrophobicity. In conclusion, ultrasound-assisted pH-shifting treatment was found to be effective in improving the physicochemical properties and solubility and foaming capacity of milk proteins, especially MCC, with promising application prospect in food industry. 相似文献
8.
9.
《Mathematical Methods in the Applied Sciences》2018,41(2):697-704
This work presents a new model of the fractional Black‐Scholes equation by using the right fractional derivatives to model the terminal value problem. Through nondimensionalization and variable replacements, we convert the terminal value problem into an initial value problem for a fractional convection diffusion equation. Then the problem is solved by using the Fourier‐Laplace transform. The fundamental solutions of the derived initial value problem are given and simulated and display a slow anomalous diffusion in the fractional case. 相似文献
10.
《Mathematical Methods in the Applied Sciences》2018,41(10):3976-3997
A generalized non‐linear nonautonomous model for the haematopoiesis (cell production) with several delays and an oscillating circulation loss rate is studied. We prove a fixed point theorem in abstract cones, from which different results on existence and uniqueness of positive almost periodic solutions are deduced. Moreover, some criteria are given to guarantee that the obtained positive almost periodic solution is globally exponentially stable. 相似文献