全文获取类型
收费全文 | 93160篇 |
免费 | 3312篇 |
国内免费 | 2688篇 |
专业分类
化学 | 35961篇 |
晶体学 | 1023篇 |
力学 | 7675篇 |
综合类 | 138篇 |
数学 | 33786篇 |
物理学 | 20577篇 |
出版年
2024年 | 47篇 |
2023年 | 301篇 |
2022年 | 556篇 |
2021年 | 598篇 |
2020年 | 703篇 |
2019年 | 726篇 |
2018年 | 10925篇 |
2017年 | 10741篇 |
2016年 | 6850篇 |
2015年 | 1809篇 |
2014年 | 1264篇 |
2013年 | 1564篇 |
2012年 | 5187篇 |
2011年 | 11832篇 |
2010年 | 6680篇 |
2009年 | 7028篇 |
2008年 | 7625篇 |
2007年 | 9588篇 |
2006年 | 1029篇 |
2005年 | 2036篇 |
2004年 | 2152篇 |
2003年 | 2504篇 |
2002年 | 1663篇 |
2001年 | 772篇 |
2000年 | 647篇 |
1999年 | 466篇 |
1998年 | 417篇 |
1997年 | 317篇 |
1996年 | 349篇 |
1995年 | 254篇 |
1994年 | 170篇 |
1993年 | 188篇 |
1992年 | 131篇 |
1991年 | 136篇 |
1990年 | 97篇 |
1989年 | 96篇 |
1988年 | 99篇 |
1987年 | 78篇 |
1986年 | 83篇 |
1985年 | 74篇 |
1984年 | 72篇 |
1983年 | 56篇 |
1982年 | 62篇 |
1981年 | 58篇 |
1980年 | 59篇 |
1979年 | 62篇 |
1978年 | 47篇 |
1914年 | 45篇 |
1909年 | 42篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Wen Zhang Hui Huang Yu Ding Margherita Gavagnin Ernesto Mollo Guido Cimino Yue‐Wei Guo 《Helvetica chimica acta》2006,89(4):813-820
Three new polyoxygenated steroids, muricesteroid ( 1 ), and menellsteroids A ( 2 ) and B ( 3 ), were isolated from two species of the South China Sea gorgonian Muricella flexuosa and Menella verrucosa Brundin , respectively. The structures of these new compounds were elucidated on the basis of extensive spectroscopic analysis, chemical methods and comparison with known related compounds. 相似文献
52.
在不同激光脉宽下的高次谐波 总被引:3,自引:2,他引:1
用数值计算方法计算了不同强激光脉冲宽度下高次谐波的产生.我们发现对于激光场强度不高,不能有效电离初态的激光场,长脉冲宽度可以更有效产生高次谐波;而对于高场强的激光场,由于它能够在几个光学周期之内把原子的初态全部电离,所以短脉冲的激光场能够更有效产生高次谐波. 相似文献
53.
In this paper we suggest a unique model for estimating the operating cost of each of three waste-collection systems. Under the traditional system, which is widely used, waste is typically collected in plastic bags and a three-man crew is needed on each vehicle. The other two systems require a one-man crew for vehicle collecting street containers. The side-loader system with fixed body automatically empties street containers into the vehicle body and empties the load at the disposal site. The side-loader system with demountable body allows the separation of the waste collection phase from transport to the disposal site, since the vehicle body can be demounted. We also present two case studies and show how the estimation of operating costs is a critical issue in decisions regarding the type of system to be used for waste collection. 相似文献
54.
A nonlinear, compressible, non-isothermal gravity wave model that involves photochemistry is used to study the effects of gravity wave on atmospheric chemical species distributions in this paper. The changes in the distributions of oxygen compound and hydrogen compound density induced by gravity wave propagation are simulated. The results indicate that when a gravity wave propagates through a mesopause region, even if it does not break, it can influence the background distributions of chemical species. The effect of gravity wave on chemical species at night is larger than in daytime. 相似文献
55.
56.
Using elementary graded automorphisms of polytopal algebras (essentially the coordinate rings of projective toric varieties)
polyhedral versions of the group of elementary matrices and the Steinberg and Milnor groups are defined. They coincide with
the usual K-theoretic groups in the special case when the polytope is a unit simplex and can be thought of as compact/polytopal substitutes
for the tame automorphism groups of polynomial algebras. Relative to the classical case, many new aspects have to be taken
into account. We describe these groups explicitly when the underlying polytope is 2-dimensional. Already this low-dimensional
case provides interesting classes of groups.
Received: 13 December 2001 / Revised version: 24 June 2002
The second author was supported by the Deutsche Forschungsgemeinschaft, INTAS grant 99-00817 and TMR grant ERB FMRX CT-97-0107
Mathematics Subject Classification (2000): 14L27, 14M25, 19C09, 52B20 相似文献
57.
王巨平 《中国科学A辑(英文版)》2002,45(7):827-835
This paper verifies the singularity conjecture for Jacobi forms with higher degree in some typical cases, and gives constructions
for the Jacobi cusp forms whose Fourier coefficients can be expressed by some kind of Rankin-typeL-series. 相似文献
58.
It is explicitly shown that if phase transition occurs at the core of a newborn neutron star with moderately strong magnetic
field strength, which populates only the electron’s Landau levels, then in the β -equilibrium condition, the quark core is
energetically much more unstable than the neutron matter of identical physical condition. 相似文献
59.
Dimitar I. Pushkarov 《Central European Journal of Physics》2004,2(3):420-455
Basic ideas and results which characterize quantum diffusion of defects in quantum crystals like solid helium as a new phenomenon
are presented. Quantum effects in such media lead to a delocalization of point defects (vacancies, impurities etc.) and they
turn into quasiparticles of a new type—defectons, which are characterized not by their position in the crystal lattice but
by their quasimomentum and dispersion law. Defecton-defecton and defecton-phonon scattering are considered and an interpolation
formula for the diffusion coefficient valid in all interesting temperature and concentration regions is presented. A comparison
with the experimental data is made. Some alternative points of view are discussed in detail and the inconsistency of the Kisvarsanyi-Sullivan
theory is shown. 相似文献