全文获取类型
收费全文 | 19460篇 |
免费 | 2230篇 |
国内免费 | 2053篇 |
专业分类
化学 | 14320篇 |
晶体学 | 219篇 |
力学 | 893篇 |
综合类 | 178篇 |
数学 | 2304篇 |
物理学 | 5829篇 |
出版年
2023年 | 257篇 |
2022年 | 359篇 |
2021年 | 446篇 |
2020年 | 600篇 |
2019年 | 595篇 |
2018年 | 520篇 |
2017年 | 479篇 |
2016年 | 748篇 |
2015年 | 761篇 |
2014年 | 960篇 |
2013年 | 1244篇 |
2012年 | 1468篇 |
2011年 | 1660篇 |
2010年 | 1190篇 |
2009年 | 1183篇 |
2008年 | 1307篇 |
2007年 | 1183篇 |
2006年 | 1078篇 |
2005年 | 950篇 |
2004年 | 910篇 |
2003年 | 757篇 |
2002年 | 780篇 |
2001年 | 627篇 |
2000年 | 518篇 |
1999年 | 379篇 |
1998年 | 269篇 |
1997年 | 207篇 |
1996年 | 251篇 |
1995年 | 195篇 |
1994年 | 184篇 |
1993年 | 162篇 |
1992年 | 148篇 |
1991年 | 120篇 |
1990年 | 129篇 |
1989年 | 94篇 |
1988年 | 103篇 |
1987年 | 73篇 |
1986年 | 75篇 |
1985年 | 98篇 |
1984年 | 71篇 |
1983年 | 69篇 |
1982年 | 51篇 |
1981年 | 48篇 |
1980年 | 48篇 |
1979年 | 35篇 |
1977年 | 37篇 |
1976年 | 37篇 |
1975年 | 34篇 |
1974年 | 48篇 |
1973年 | 44篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
In this article, a kind of auxiliary design BSA* for constructing BSAs is introduced and studied. Two powerful recursive constructions on BSAs from 3‐IGDDs and BSA*s are exploited. Finally, the necessary and sufficient conditions for the existence of a BSA(v, 3, λ; α) with α = 2, 3 are established. © 2006 Wiley Periodicals, Inc. J Combin Designs 15: 61–76, 2007 相似文献
82.
关于《一类奇异边值问题的正解》的注记 总被引:3,自引:0,他引:3
文[4]通过构造反例断言文[1]中定理的必要性证明有误,本文首先指出文[4] 的这个断言不正确,然后对文[4]中定理2.1作了本质性的改进. 相似文献
83.
Controllability of Functional Integro-Differential Inclusions with an Unbounded Delay 总被引:1,自引:0,他引:1
In this paper, a sufficient condition is established for the controllability of neutral functional integro-differential inclusions
with an unbounded delay in Banach spaces. The approach used is a fixed-point theorem for condensing maps due to Martelli and
the theory of analytic semigroup of linear operators.
Communicated by F. Zirilli
Research supported by NNSF of China, by the Teaching and Research Award Program for Outstanding Young Teachers in Higher Education
Institutions of the Ministry of Education of China, and by the Qing Lan Talent Engineering Fund QL-05-164 of Lanzhou Jiaotong
University. The authors are grateful to Professor F. Zirilli and two anonymous referees for valuable suggestions improving
this paper. 相似文献
84.
By introducing an imaginary space transform curvature ρs, a complex space called Riemannian space is constructed, in which the light propagating in free space has the trajectory
of straight line while propagating. Moreover, this curvature couples with that of the wave front of the paraxial beam ρw, and therefore a complex curvature ρc is constructed, which can be employed to investigate the behavior of the light transmission and to generalize the ABCD law.
Project supported by the National Hi-Tech Inertial Confinement Fusion Committee, the Guangdong Natural Science Foundation
the Postdoctoral Foundation of Guangdong and National Postdoctoral Foundation of China. 相似文献
85.
M.-C. Chang 《Geometric And Functional Analysis》1997,7(5):861-872
((Without abstract))
Submitted: October 1996, final version: April 1997 相似文献
86.
单糖的高效毛细管电泳间接紫外检测法研究 总被引:5,自引:1,他引:4
本文研究了单糖的毛细管电泳间接紫外检测法。实验发现选用β-哚吲乙酸-磷酸钠体系作为背景电解质比较理论想,用于9种未经衍生的单糖进行毛细管电泳分离和间接紫外检测可取得满意结果,对半乳糖,甘露糖和葡萄糖酸的检出极限为2-10pmol水平。本文还讨论了背景电解质浓度与样品响应值的关系以及各种操作条件的影响。 相似文献
87.
88.
89.
Quantitative dependence of MR signal intensity on tissue concentration of Gd(HP-DO3A) in the nephrectomized rat. 总被引:3,自引:0,他引:3
P Wedeking C H Sotak J Telser K Kumar C A Chang M F Tweedle 《Magnetic resonance imaging》1992,10(1):97-108
Cardiac-gated SE 20/224 +/- 20 MR images were obtained from nephrectomized rats before and after intravenously administering 153Gd-Gd(HP-DO3A). The concentration of Gd, [Gd], was linear in dose in myocardium, skeletal muscle, and blood. Under steady-state conditions, where d[Gd]/dt = 0, image intensities (IIN) in regions of interest were compared with the measured [Gd]. IIN was linear in myocardium at less than or equal to 0.61 mumol/g-myocardium (less than or equal to 0.5 mmol/kg dose) and in skeletal muscle at less than or equal to 0.63 mumol/g-muscle (less than or equal to 0.75 mmol/kg). Above 0.6 mumol Gd/g-tissue, IIN did not increase further. The in vivo data were consistent with measured ex vivo and in vivo relaxivities. A 29% greater slope for IIN versus [Gd] in myocardium [14,439 +/- 4350 IIN (mumol/g)] than in muscle [10,258 +/- 5,296 IIN/(mumol/g)] was attributed to a significant difference in blood content: 25% versus 2% weight blood in myocardium and skeletal muscle, respectively. Two components were apparent from plots of ex vivo 1/T1 versus [Gd] in myocardium and muscle, and only one for blood. 相似文献
90.