全文获取类型
收费全文 | 16976篇 |
免费 | 2661篇 |
国内免费 | 1705篇 |
专业分类
化学 | 12558篇 |
晶体学 | 210篇 |
力学 | 886篇 |
综合类 | 72篇 |
数学 | 1648篇 |
物理学 | 5968篇 |
出版年
2024年 | 62篇 |
2023年 | 325篇 |
2022年 | 592篇 |
2021年 | 592篇 |
2020年 | 658篇 |
2019年 | 669篇 |
2018年 | 600篇 |
2017年 | 528篇 |
2016年 | 783篇 |
2015年 | 815篇 |
2014年 | 1036篇 |
2013年 | 1279篇 |
2012年 | 1496篇 |
2011年 | 1591篇 |
2010年 | 1153篇 |
2009年 | 970篇 |
2008年 | 1133篇 |
2007年 | 1021篇 |
2006年 | 891篇 |
2005年 | 787篇 |
2004年 | 598篇 |
2003年 | 507篇 |
2002年 | 473篇 |
2001年 | 334篇 |
2000年 | 327篇 |
1999年 | 266篇 |
1998年 | 236篇 |
1997年 | 203篇 |
1996年 | 196篇 |
1995年 | 155篇 |
1994年 | 192篇 |
1993年 | 135篇 |
1992年 | 128篇 |
1991年 | 100篇 |
1990年 | 95篇 |
1989年 | 89篇 |
1988年 | 47篇 |
1987年 | 32篇 |
1986年 | 36篇 |
1985年 | 34篇 |
1984年 | 23篇 |
1983年 | 15篇 |
1982年 | 22篇 |
1981年 | 11篇 |
1980年 | 20篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 8篇 |
1976年 | 11篇 |
1974年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 890 毫秒
141.
Jin Sun Yihu Song Qiang Zheng Hong Tan Jie Yu Hong Li 《Journal of Polymer Science.Polymer Physics》2007,45(18):2594-2602
The reinforcement and nonlinear viscoelastic behavior have been investigated for silica (SiO2) filled solution‐polymerized styrene butadiene rubber (SSBR). Experimental results reveal that the nonlinear viscoelastic behavior of the filled rubber is similar to that of unfilled SSBR, which is inconsistent with the general concept that this characteristic comes from the breakdown and reformation of the filler network. It is interesting that the curves of either dynamic storage modulus (G′) or loss tangent (tan δ) versus strain amplitude (γ) for the filled rubber can be superposed, respectively, on those for the unfilled one, suggesting that the primary mechanism for the Payne effect is mainly involved in the nature of the entanglement network in rubbery matrix. It is believed there exists a cooperation between the breakdown and reformation of the filler network and the molecular disentanglement, resulting in enhancing the Payne effect and improving the mechanical hysteresis at high strain amplitudes. Moreover, the vertical and the horizontal shift factors for constructing the master curves could be well understood on the basis of the reinforcement factor f(φ) and the strain amplification factor A(φ), respectively. The surface modification of SiO2 causes a decrease in f(φ), which is ascribed to weakeness of the filler–filler interaction and improvement of the filler dispersion. However, the surface nature of SiO2 hardly affects A(φ). © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2594‐2602, 2007 相似文献
142.
143.
Ki Sik Ha 《Semigroup Forum》1989,38(1):215-221
LetZ be a generator of an exponentially boundedC-semigroup {S
t
}
t≥0 in a Banach space and letT
t
=C
−1
S
t
. We show that the spectral mapping theorems such as exp(tσ(Z)) ⊂ σ(T
t
) and exp(tσ
p
(Z)) ⊂ tσ
p
(T
t
) ⊂ exp(tσ
p
(Z)) ⋃ {0} for everyt≥0 hold.
The present studies were supported by the Basic Science Research Institute Program, Ministry of Education, 1987. 相似文献
144.
Using the Ward-Takahashi identity, on-shell condition, bound Dirac equation and off-shell expansion, a reduced version of half off-shell virtual photon nucleon vertex has been suggested. The vertex are decomposed into several different order terms: the on-shell terms, first and second off-shell terms. The off-shell behaviour of the form factors is discussed in the one meson loop model. Using the reduced vertex and parametrized off-shell form factors the quasielastic response functions are calculated for several nuclei at ¦q¦–kf and for56Fe at large ¦q¦ up to 1.14 GeV/c and at ?q2=0.9 (GeV/c)2. The Coulomb sums are evaluated and a comparison of the theoretical prediction with data is given. The off-shell electron nucleon cross section is calculated and compared with the “cc1” off-shell extrapolation. 相似文献
145.
中国六种管巢蛛记述(蜘蛛目:管巢蛛科) 总被引:2,自引:0,他引:2
本文记述我国管巢蛛6种,即白马管巢蛛Clubiona baimaensis sp. nov.、朝鲜管巢蛛C. corena Paik 金氏管巢蛛C. kimyongkii Paik、琴形管巢蛛C. lyriformis sp. nov.、臼齿管巢蛛C. moralis sp. nov.和江原管巢蛛C. wolchongsensis Paik。其中3种为新种,3种为我国新纪录。文中并提出,乌苏里管巢蛛C. ussurica Michailov(♀)可能与金氏管巢蛛(♂)为同种,因而乌苏里管巢蛛的拉丁字名应为后一种的同物异名。 相似文献
146.
NongYueHE JianXinTANG SongLI HongCHEN AnCunZHOU 《中国化学快报》2005,16(3):397-400
Polypropylene microporous membranes were treated with plasma in a mixture of N2 and H2 (1:2 in volume). Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and ultra-violet (UV) spectra demonstrated the success of grafting amino groups. The density of the polar amino groups on the membrane surface is about 0.59 μmol/cm^2. The as-treated membranes were successively applied to the in situ synthesis of oligonucleotides and an average coupling yield was more than 98%. The surface feature of the treated membrane is suggested to be responsible for its advantage over a glass slide. 相似文献
147.
148.
A stage-structured predator–prey system with delays for prey and predator, respectively, is proposed and analyzed. Mathematical analysis of the model equations with regard to boundedness of solutions, permanence and stability are analyzed. Some sufficient conditions which guarantee the permanence of the system and the global asymptotic stability of the boundary and positive equilibrium, respectively, are obtained. 相似文献
149.
150.
The main objects of study in this article are two classes of Rankin–Selberg L-functions, namely L(s,f×g) and L(s, sym2(g)× sym2(g)), where f,g are newforms, holomorphic or of Maass type, on the upper half plane, and sym2(g) denotes the symmetric square lift of g to GL(3). We prove that in general, i.e., when these L-functions are not divisible by L-functions of quadratic characters (such divisibility happening rarely), they do not admit any LandauSiegel zeros. Such zeros, which are real and close to s=1, are highly mysterious and are not expected to occur. There are corollaries of our result, one of them being a strong lower bound for special value at s=1, which is of interest both geometrically and analytically. One also gets this way a good bound onthe norm of sym2(g). 相似文献