全文获取类型
收费全文 | 131712篇 |
免费 | 8528篇 |
国内免费 | 6941篇 |
专业分类
化学 | 63831篇 |
晶体学 | 1447篇 |
力学 | 9520篇 |
综合类 | 545篇 |
数学 | 38188篇 |
物理学 | 33650篇 |
出版年
2024年 | 105篇 |
2023年 | 973篇 |
2022年 | 1311篇 |
2021年 | 1619篇 |
2020年 | 2006篇 |
2019年 | 1982篇 |
2018年 | 11712篇 |
2017年 | 11435篇 |
2016年 | 8157篇 |
2015年 | 3123篇 |
2014年 | 3088篇 |
2013年 | 4140篇 |
2012年 | 8338篇 |
2011年 | 15051篇 |
2010年 | 8908篇 |
2009年 | 9214篇 |
2008年 | 10159篇 |
2007年 | 11952篇 |
2006年 | 3394篇 |
2005年 | 3984篇 |
2004年 | 3683篇 |
2003年 | 3767篇 |
2002年 | 2779篇 |
2001年 | 1666篇 |
2000年 | 1556篇 |
1999年 | 1473篇 |
1998年 | 1266篇 |
1997年 | 1091篇 |
1996年 | 1153篇 |
1995年 | 936篇 |
1994年 | 844篇 |
1993年 | 785篇 |
1992年 | 675篇 |
1991年 | 601篇 |
1990年 | 535篇 |
1989年 | 421篇 |
1988年 | 355篇 |
1987年 | 280篇 |
1986年 | 308篇 |
1985年 | 283篇 |
1984年 | 187篇 |
1983年 | 147篇 |
1982年 | 155篇 |
1981年 | 114篇 |
1980年 | 107篇 |
1979年 | 110篇 |
1978年 | 75篇 |
1976年 | 54篇 |
1974年 | 52篇 |
1973年 | 70篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
FTIR光谱遥测红外药剂的燃烧温度 总被引:2,自引:0,他引:2
本文利用遥感FTIR光谱,对红外药剂的燃烧特性进行了研究。在分辨率为4cm^-1时,收集4700-740cm^-1波段的光谱。从HF等燃烧产物发射的分子振转基带精细结构的谱线强度分布,可以对燃烧温度进行遥感测定,并给出了燃烧温度随时间的变化关系,实验结果表明燃烧表面附近温度梯度很大,存在着急剧的变化温度场,同时也说明,在不干扰火焰温度场的情况下,利用遥感FTIR光谱对剧烈的、非稳态快速燃烧的火焰温度进行连续实时的遥感测量,是一种快速、准确、灵敏度高的测温方法,显示了它在燃烧温度测量、产物浓度测试以及燃烧机理研究等方面的应用前景。 相似文献
102.
A pressure sensitive paint (PSP) measurement has been known as a pressure field measurement technique based on the oxygen quenching phenomenon of luminescence of specific luminophores. A PSP measurement was applied for pressure field measurement in a low-solidity circular cascade diffuser of a single-stage transonic centrifugal compressor with 5 in pressure ratio for HFC134a gas. The oxygen concentration was about 500 ppm. Ru (bath-phen) was adsorbed on a silica-gel thinlayer chromatography sheet, and the sheet was pasted onto the side-wall between the cascade vanes. A drastic change in luminescent intensity was recognized during a surge condition. Also the pressure variations based on luminescent intensity agreed well with the pressure fluctuations measured using a semiconductor pressure sensor with high-frequency-response. It was shown that a PSP measurement worked well to investigate the unsteady pressure fields in a circular cascade diffuser of a transonic centrifugal compressor. Moreover, the time response of PSP becomes clear as a problem to be overcome for the present. 相似文献
103.
网络环境下的物理实验教学模式 总被引:4,自引:2,他引:2
目前网络环境下的物理实验教学新模式主要有物理实验专题网站、实验教学网络管理、实验类网络课程及远程控制物理实验.本文简要介绍了各个模式的特点及实施方法. 相似文献
104.
105.
Dual fractional cutting plane algorithms, in which cutting planes are used to iteratively tighten a linear relaxation of an integer program,
are well-known and form the basis of the highly successful branch-and-cut method. It is rather less well-known that various primal cutting plane algorithms were developed in the 1960s, for example by Young. In a primal algorithm, the main role of the cutting
planes is to enable a feasible solution to the original problem to be improved. Research on these algorithms has been almost
non-existent.
In this paper we argue for a re-examination of these primal methods. We describe a new primal algorithm for pure 0-1 problems based on strong valid inequalities and give some encouraging computational results. Possible extensions to the case of general
mixed-integer programs are also discussed. 相似文献
106.
107.
108.
Yasuyuki Kawahigashi 《Communications in Mathematical Physics》2002,226(2):269-287
We study the recent construction of subfactors by Rehren which generalizes the Longo–Rehren subfactors. We prove that if
we apply this construction to a non-degenerately braided subfactor N⊂M and α±-induction, then the resulting subfactor is dual to the Longo–Rehren subfactor M⊗M
opp⊂R arising from the entire system of irreducible endomorphisms of M resulting from αplusmn;-induction. As a corollary, we solve a problem on existence of braiding raised by Rehren negatively. Furthermore, we generalize
our previous study with Longo and Müger on multi-interval subfactors arising from a completely rational conformal net of factors
on S
1 to a net of subfactors and show that the (generalized) Longo–Rehren subfactors and α-induction naturally appear in this context.
Received: 11 September 2001 / Accepted: 7 October 2001 相似文献
109.
The structural evolution in amorphous silicon and germanium thin films has been investigated by high-resolution transmission electron microscopy (HRTEM) in conjunction with autocorrelation function (ACF) analysis. The results established that the structure of as-deposited semiconductor films is of a high density of nanocrystallites embedded in the amorphous matrix. In addition, from ACF analysis, the structure of a-Ge is more ordered than that of a-Si. The density of embedded nanocrystallites in amorphous films was found to diminish with annealing temperature first, then to increase. The conclusions also corroborate well with the results of diminished medium-range order in annealed amorphous films determined previously by a variable coherence microscopy method. 相似文献
110.
Julio Castellanos 《Mathematische Zeitschrift》2002,239(4):777-802
We consider complete ideals supported on finite sequences of infinitely near points, in regular local rings with dimensions
greater than two. We study properties of factorizations in Lipman special *-simple complete ideals. We relate it to a type
of proximity, linear proximity, of the points, and give conditions in order to have unique factorization. Several examples
are presented.
Received: 2 February 2000 / in final form: 14 March 2001 / Published online: 18 January 2002 相似文献