全文获取类型
收费全文 | 9541篇 |
免费 | 763篇 |
国内免费 | 1109篇 |
专业分类
化学 | 5814篇 |
晶体学 | 186篇 |
力学 | 84篇 |
综合类 | 61篇 |
数学 | 477篇 |
物理学 | 4791篇 |
出版年
2023年 | 34篇 |
2022年 | 241篇 |
2021年 | 213篇 |
2020年 | 127篇 |
2019年 | 149篇 |
2018年 | 197篇 |
2017年 | 179篇 |
2016年 | 253篇 |
2015年 | 222篇 |
2014年 | 258篇 |
2013年 | 791篇 |
2012年 | 403篇 |
2011年 | 427篇 |
2010年 | 349篇 |
2009年 | 549篇 |
2008年 | 522篇 |
2007年 | 605篇 |
2006年 | 578篇 |
2005年 | 497篇 |
2004年 | 446篇 |
2003年 | 437篇 |
2002年 | 406篇 |
2001年 | 370篇 |
2000年 | 354篇 |
1999年 | 336篇 |
1998年 | 281篇 |
1997年 | 242篇 |
1996年 | 252篇 |
1995年 | 266篇 |
1994年 | 221篇 |
1993年 | 177篇 |
1992年 | 239篇 |
1991年 | 132篇 |
1990年 | 86篇 |
1989年 | 82篇 |
1988年 | 87篇 |
1987年 | 58篇 |
1986年 | 44篇 |
1985年 | 40篇 |
1984年 | 40篇 |
1983年 | 29篇 |
1982年 | 37篇 |
1981年 | 21篇 |
1980年 | 24篇 |
1979年 | 25篇 |
1978年 | 13篇 |
1976年 | 18篇 |
1975年 | 13篇 |
1974年 | 13篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
For the NO molecule, modelled as a Morse oscillator, time-dependent (TD) nuclear Schr?dinger equation has been numerically
solved for the multiphoton vibrational dynamics of the molecule under a far-infrared laser of wavelength 10503 nm, and four
different intensities,I = 1 × 108, 1 × 1013, 5 × 1016, and 5 × 1018 W cm−2 respectively. Starting from the vibrational ground state at zero time, various TD quantities such as the norm, dissociation
probability, potential energy curve and dipole moment are examined. Rich high-harmonics generation (HHG) spectra and above-threshold
dissociation (ATD) spectra, due to the multiphoton interaction of vibrational motions with the laser field, and consequent
elevation to the vibrational continuum, have been obtained and analysed.
Dedicated to Professor C N R Rao on his 70th birthday
An erratum to this article is available at . 相似文献
12.
Orotic acid (vitamin B13) is a key intermediate in biosynthesis of the pyrimidine nucleotides in living organisms, moreover, it may serve as the biological carrier for some metal ions. cis-Diammine(orotato)platinum(II), cis-[Pt(C5H2N2O4)(NH3)2] can be considered as a new potential cisplatin analogue. The FT-Raman and FT-IR spectra of the title complex are reported, for the first time. The molecular structure, vibrational frequencies, and the theoretical infrared and Raman intensities have been calculated by the density functional mPW1PW91 method. The detailed vibrational assignment has been made on the basis of the calculated potential energy distribution. The theoretically predicted IR and Raman spectra show very good agreement with experiment. Natural bond orbital (NBO) analyses were performed for cisplatin, carboplatin and the title complex. The results provided new data on the nature of platinum–ligand bonding in these compounds. Strong intramolecular hydrogen bond between the orotate ligand and the coordinated ammonia group stabilizes the structure of the platinum(II) complex. Thus, it is suggested that the orotate ligand in the title complex is more inert to the substitution reactions than the chloride ligands in cisplatin. 相似文献
13.
ABSTRACT. Limiting adverse consequences of fishing on essential fish habitat has emerged as a key fishery management objective. The conventional approach to providing habitat protection is to create MPAs or marine reserves that prohibit all or certain types of fishing in specific areas. However, there may be more cost‐effective and flexible ways to provide habitat protection. We propose an individual habitat quota (IHQ) system for habitat conservation that would utilize economic incentives to achieve habitat conservation goals cost‐effectively. Individual quotas of habitat impact units (HIU) would be distributed to fishers with an aggregate quota set to maintain a target habitat “stock.” HIU use would be based on a proxy for marginal habitat damage. We use a dynamic, explicitly spatial fishery and habitat simulation model to explore how such a system might work. We examine how outcomes are affected by spatial heterogeneity in the fishery and the scale of habitat regulation. We find that the IHQ system is a highly cost‐effective means of ensuring a given level of habitat protection, but that spatial heterogeneity and the scale of regulation can have significant effects on the distribution of habitat protection. 相似文献
14.
15.
IR and Raman spectra of (NH4)3ZnCl5 have been recorded. The observed spectra have been analysed on the basis of the vibrations of ZnCl
4
2−
and NH
4
+
ions. The appearance of multiple Raman bands indicates the presence of two different types of ammonium ions. The effect of
anisotropic crystalline field over the ZnCl4 and NH4 tetrahedra is also discussed. The assignment of internal modes has been verified by the potential energy distribution calculations. 相似文献
16.
广义拟变分不等式解集的稳定性及本质连通区的存在性 总被引:3,自引:3,他引:0
在赋范线性空间下.讨论广义拟变分不等式解集的稳定性,证明了满足一定连续性和凸性条件的广义拟变分不等式问题构成的空间M中,大多数(在Baire分类意义下)广义拟变分不等式问题的解集是稳定的,并证明了M中每一个广义拟变分不等式的解集至少存在一个本质连通区。 相似文献
17.
A mapping from a subset of the real axis to a metric space with finite generalized variation is shown to admit extension to a mapping of the whole real axis with the same variation. This result leads to characterization of the generalized essential variation of a mapping. 相似文献
18.
环丙沙星在胶束体系中的荧光特性研究及应用 总被引:9,自引:1,他引:8
研究了环丙沙星在胶束体系中的荧光性质,发现十二烷基硫基酸对环丙沙星有较强的增敏作用。据此建立了胶束增敏荧光光谱法测定痕量环丙沙星的新方法,经样品测定,其线性范围为0.033-0.60μg.mL^-1,检出限为0.033μg.mL^-1,回收率为94.0%-98.1%相对标准偏差为1.5%-2.8%。 相似文献
19.
L. G. Mezhlumyan Sh. Kh. Rakhimova P. Kh. Yuldashev N. K. Aikhodzhaeva M. A. Saidkhodzhaeva A. I. Massino S. Makhmudova 《Chemistry of Natural Compounds》2004,40(1):59-62
The glutelin fraction was used as the food value index of local corn. The base-soluble fraction was used as a test of the glassiness of local strains of rice grain. The content of gliadins and glutelins did not change over 24 h after wheat grain cultivated in Uzbekistan was moistened. 相似文献
20.
We have used electronic spectroscopy in the 160–1100 nm range to study the polyvinyl alcohol-nickel(II) chloride system. Based
on the results obtained, we hypothesize formation of mixed-ligand complexes of the type [Ni(H2O)6-nCln]2-n (n = 0, 1,..., 5) in the polyvinyl alcohol matrix. Transformation of the coordination sphere as the NiCl2 concentration changes is apparent both in the region of the d-d transition bands (350–1100 nm) and in the region of the charge
transfer bands (160–250 nm). We propose assigning the absorption bands separated by mathematical treatment to complexes of
specific compositions.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 1, pp. 136–138, January–February, 2006. 相似文献