全文获取类型
收费全文 | 1618篇 |
免费 | 215篇 |
国内免费 | 201篇 |
专业分类
化学 | 272篇 |
晶体学 | 12篇 |
力学 | 543篇 |
综合类 | 41篇 |
数学 | 556篇 |
物理学 | 610篇 |
出版年
2024年 | 5篇 |
2023年 | 17篇 |
2022年 | 84篇 |
2021年 | 78篇 |
2020年 | 59篇 |
2019年 | 46篇 |
2018年 | 50篇 |
2017年 | 73篇 |
2016年 | 64篇 |
2015年 | 66篇 |
2014年 | 93篇 |
2013年 | 127篇 |
2012年 | 78篇 |
2011年 | 97篇 |
2010年 | 88篇 |
2009年 | 79篇 |
2008年 | 76篇 |
2007年 | 94篇 |
2006年 | 106篇 |
2005年 | 92篇 |
2004年 | 71篇 |
2003年 | 68篇 |
2002年 | 58篇 |
2001年 | 50篇 |
2000年 | 52篇 |
1999年 | 39篇 |
1998年 | 35篇 |
1997年 | 36篇 |
1996年 | 33篇 |
1995年 | 33篇 |
1994年 | 18篇 |
1993年 | 11篇 |
1992年 | 12篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 3篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1957年 | 2篇 |
排序方式: 共有2034条查询结果,搜索用时 21 毫秒
101.
1 引言 我国耕地严重缺磷的面积所占比例高达2/3,而目前施肥的磷/氮比例又远远低于国际平均水平,如此的比例失调将严重影响农业增产.在当前施用的磷肥中,普钙和重钙占了很大的比例.由于重钙是用磷酸而非硫酸酸解磷矿,所以不含硫酸钙杂质,有效五氧化二磷的含量也由16~21%提高到45~52%,肥效比普钙提高两到三倍.为此国家"八五"重点项目引进了Hy dro GTSP工艺2×40万吨/年重钙装置.该装置于1999年3月试车以来难以达到满负荷生产. 作者通过对生产工艺各环节的分析,指出反应料浆含水量偏高是影响装置生产负荷的主要因素.料浆中水分的重要来源之一是二次球磨. 相似文献
102.
A quantum-mechanical theory of joint nonideal measurement of incompatible polarization observables is applied to an EPR-like experiment. It is demonstrated that this experiment yields both information satisfying and information violating the Bell inequalities. The measurement is also discussed in the context of a local hidden-variables theory. It is argued that the violation of an additional assumption of reproducibility of the hidden variable rather than violation of locality may be responsible for the violation of the Bell inequalities. 相似文献
103.
104.
105.
In this paper two new architectures for optical image verification are proposed. Both architectures are based on conventional joint transform correlators (JTCs) adopting a Fourier hologram and can significantly improve the recovered image quality. First, an input phase-only function is Fourier transformed and then interferes with a reference wave that is diffracted from a plane wave incident on another random phase mask. Second, two phase-only functions are placed at the two input sides of a beamsplitter such that the interference pattern of their Fourier transforms can be detected. To obtain a predefined target image in the output plane, one of the input phase functions is iteratively retrieved by the use of the projection onto constraint sets algorithm. Simulation results show that the less mean squared error and better image quality are obtained for both the binary and grayscale images. 相似文献
106.
A Littlewood-Paley type
inequality 总被引:2,自引:0,他引:2
In this note we prove the following theorem: Let u be a
harmonic function in the unit ball
and
. Then there is a
constant C =
C(p,
n) such that
. 相似文献
107.
108.
When the stagnation temperature of a perfect gas increases, the specific heats and their ratio do not remain constant any
more and start to vary with this temperature. The gas remains perfect and its state equation always remains valid, except
it will be called a calorically imperfect gas. The aim of this research is to develop the relations of the necessary thermodynamics
and geometrical ratios and to study the supersonic flow at high temperature (lower than the threshold of dissociation). The
results are found by the resolution of nonlinear algebraic equations and integration of complex analytical functions where
the exact calculation is impossible. The dichotomy method is used to solve the nonlinear equation, and the Simpson algorithm
is used for the numerical integration of the found integrals. A condensation of the nodes is used, since the functions to
be integrated have a high gradient at the extremity of the interval of integration. A comparison is made with a calorifcally
perfect gas to determine the error of this. An application is made for air in a supersonic nozzle.
The text was submitted by the authors in English. 相似文献
109.
110.
Hirokazu Sato Shusaku Hamada Roberto M. Sertkawa Tatsuya Nishimura Takashi Usui Hideo Sekino 《高压研究》2013,33(1-6):403-413
Abstract Continuous flames have been observed in Supercritical water oxidation (scWO) of isopropyl alcohol (IPA), using a vertical continuous reactor with sapphire windows and a mixing nozzle. Two types of continuous flame were confirmed: the one was long pale blue colored and the other was red short cone shaped, changing blue to red at around air ratio 2.0. The flame was strongly influenced by IPA concentration, air ratio and design of the mixing nozzle. Results for decomposition of PA are presented for IPA concentrations ranging from 600 up to 28260 ppm as TOC and initial reactor temperatures, were mostly around 490°C, at 25 MPa. Decomposition rate at steady state was over 99.9%. Experimentally measured CO2 and O2 concentrations at the flue gas were in good agreement with theoretically calculated values. Even for low air ratio as 1.1, high decomposition rate without CO, NO, NO2 was achieved. 相似文献