全文获取类型
收费全文 | 346898篇 |
免费 | 3063篇 |
国内免费 | 1047篇 |
专业分类
化学 | 177369篇 |
晶体学 | 5884篇 |
力学 | 15505篇 |
综合类 | 7篇 |
数学 | 40400篇 |
物理学 | 111843篇 |
出版年
2021年 | 2646篇 |
2020年 | 2941篇 |
2019年 | 3289篇 |
2018年 | 4318篇 |
2017年 | 4300篇 |
2016年 | 6431篇 |
2015年 | 3911篇 |
2014年 | 6238篇 |
2013年 | 15620篇 |
2012年 | 11974篇 |
2011年 | 14431篇 |
2010年 | 10180篇 |
2009年 | 10083篇 |
2008年 | 13301篇 |
2007年 | 13274篇 |
2006年 | 12673篇 |
2005年 | 11343篇 |
2004年 | 10568篇 |
2003年 | 9398篇 |
2002年 | 9147篇 |
2001年 | 10495篇 |
2000年 | 7989篇 |
1999年 | 6198篇 |
1998年 | 5098篇 |
1997年 | 5027篇 |
1996年 | 4663篇 |
1995年 | 4389篇 |
1994年 | 4225篇 |
1993年 | 4027篇 |
1992年 | 4597篇 |
1991年 | 4533篇 |
1990年 | 4414篇 |
1989年 | 4162篇 |
1988年 | 4220篇 |
1987年 | 4252篇 |
1986年 | 3961篇 |
1985年 | 5200篇 |
1984年 | 5473篇 |
1983年 | 4654篇 |
1982年 | 4892篇 |
1981年 | 4700篇 |
1980年 | 4576篇 |
1979年 | 4771篇 |
1978年 | 4898篇 |
1977年 | 4838篇 |
1976年 | 4937篇 |
1975年 | 4686篇 |
1974年 | 4631篇 |
1973年 | 4894篇 |
1972年 | 3175篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
151.
The synthesis and characterization of a new homologous series of compounds, the 2-cyano-1,3-phenylene bis[4-(4-n-alkoxyphenyliminomethyl)benzoates] derived from 2-cyanoresorcinol is reported. All the compounds are enantiotropic mesogens and exhibit the fascinating B7 mesophase. The characterization of the mesophase was performed using polarizing optical microscopy, differential scanning calorimetry, X-ray diffraction and electro-optical studies. 相似文献
152.
It is shown that the three-dimensional Navier-Stokes equation for incompressible fluid can be represented as an equation including
only quaternions as co-ordinate operators and variables. Only the quaternion operations such as a quaternion product and a
quaternion conjugation over these variables are used. 相似文献
153.
S. F. Dubinin V. E. Arkhipov S. G. Teploukhov V. D. Parkhomenko 《Physics of the Solid State》2003,45(11):2147-2151
The {1/2, 0, 1/2} nuclear superstructure in an La0.93Sr0.07MnO3 manganite orthorhombic crystal is revealed using thermal-neutron diffraction. It is demonstrated that this superlattice belongs to the class of distortion-type structures and is directly associated with a 1/16-type ordering of Mn4+ and Mn3+ ions in a collinear ferromagnetic phase of the La0.93Sr0.07MnO3 manganite. 相似文献
154.
达草灭对莱茵衣藻(Chlamydomonas reinhardtii) 品系遗传后效应的研究 总被引:1,自引:0,他引:1
通过将莱菌衣藻(Chlamydomonas reinhardtii)6种达草灭抗性突变株分别与野生型株、丧失合成叶绿素b能力的cbnI-43等基因突变株和精氨酸依赖型突变株杂交对其后代进行四分析与随机分析,发现在Nfr-4-Nfr-7突变株中达草灭抗性状只有单一核基因遗传的性质,而在Nfr-1、Nfr-3~Nfr-7抗性株的抗性性状都是由同一个nfr-1基因(norflurazon resisanse)的突变所决定的,而Nfr-4抗性株的抗性性状是由另一滚突变等位基因nfr-2所决定的。在Nfr-1和Nfr-3抗性株中除了nfr-1基因的突变还有nfr-3基因突变的参与。 相似文献
155.
O. Perru F. Ibrahim O. Bajeat C. Bourgeois F. Clapier E. Cottereau C. Donzaud M. Ducourtieux S. Galès D. Guillemaud-Mueller C. Lau H. Lefort F. Le Blanc A. C. Mueller J. Obert N. Pauwels J. C. Potier F. Pougheon J. Proust B. Roussière J. Sauvage O. Sorlin D. Verney 《Physics of Atomic Nuclei》2003,66(8):1421-1427
The PARRNe facility has been used to produce neutron-rich isotopes 83,84Gaby the ISOL method. Their decay has been studied, and β-γ coincidence and γ-γ coincidence data were collected as a function of time. The first two excited levels in 83Ge and the first excited level in 84Ge have been measured for the first time. 相似文献
156.
B. F. Svaiter 《Proceedings of the American Mathematical Society》2003,131(12):3851-3859
Any maximal monotone operator can be characterized by a convex function. The family of such convex functions is invariant under a transformation connected with the Fenchel-Legendre conjugation. We prove that there exists a convex representation of the operator which is a fixed point of this conjugation.
157.
B.V. Raghavaiah 《Journal of Physics and Chemistry of Solids》2004,65(6):1153-1164
PbO-Sb2O3 glasses added with different concentrations of As2O3 (10-55 mol%) were prepared to understand their IR spectra, elastic properties (Young's modulus E, Shear modulus G, microhardness H), optical absorption and dielectric properties (constant ε, loss tan δ, ac conductivity σac over a moderately wide range of frequency and temperature and breakdown strength in air medium at room temperature). Results have indicated that the structure of the PbO-Sb2O3-As2O3 glass is more rigid when the concentration of As2O3 is around 40 mol%. 相似文献
158.
We examine several interesting relationships and expressions involving Fourier-Feynman transform, convolution product and
first variation for functionals in the Fresnel class F(B) of an abstract Wiener space B. We also prove a translation theorem and Parseval's identity for the analytic Feynman integral.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
159.
We present a practical polynomial-time algorithm for computing the
zeta function of a Kummer curve over a finite field of small
characteristic. Such algorithms have recently been obtained using a
method of Kedlaya based upon Monsky–Washnitzer cohomology, and are of
interest in cryptography. We take a different approach.
The problem is reduced to that of computing the L-function
of a multiplicative character sum. This latter task is achieved via a
cohomological formula based upon the work of Dwork and Reich. We show,
however, that our method and that of Kedlaya are very closely related.Dedicated to the memory of Gian-Carlo Rota 相似文献
160.