全文获取类型
收费全文 | 358068篇 |
免费 | 2535篇 |
国内免费 | 860篇 |
专业分类
化学 | 187766篇 |
晶体学 | 5187篇 |
力学 | 16608篇 |
综合类 | 13篇 |
数学 | 42192篇 |
物理学 | 109697篇 |
出版年
2020年 | 3340篇 |
2019年 | 3961篇 |
2018年 | 5591篇 |
2017年 | 5644篇 |
2016年 | 7305篇 |
2015年 | 3781篇 |
2014年 | 6485篇 |
2013年 | 14723篇 |
2012年 | 11143篇 |
2011年 | 13396篇 |
2010年 | 10283篇 |
2009年 | 10309篇 |
2008年 | 13044篇 |
2007年 | 13008篇 |
2006年 | 12002篇 |
2005年 | 10796篇 |
2004年 | 9942篇 |
2003年 | 8999篇 |
2002年 | 9080篇 |
2001年 | 9875篇 |
2000年 | 7634篇 |
1999年 | 5792篇 |
1998年 | 5129篇 |
1997年 | 5029篇 |
1996年 | 4664篇 |
1995年 | 4034篇 |
1994年 | 4065篇 |
1993年 | 4142篇 |
1992年 | 4314篇 |
1991年 | 4621篇 |
1990年 | 4445篇 |
1989年 | 4491篇 |
1988年 | 4326篇 |
1987年 | 4332篇 |
1986年 | 4123篇 |
1985年 | 5300篇 |
1984年 | 5422篇 |
1983年 | 4505篇 |
1982年 | 4841篇 |
1981年 | 4624篇 |
1980年 | 4263篇 |
1979年 | 4708篇 |
1978年 | 5005篇 |
1977年 | 5078篇 |
1976年 | 5131篇 |
1975年 | 4856篇 |
1974年 | 4778篇 |
1973年 | 5047篇 |
1972年 | 3746篇 |
1971年 | 3327篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
901.
ALEPH Collaboration D. Buskulic D. Casper I. De Bonis D. Decamp P. Ghez C. Goy J. -P. Lees A. Lucotte M. -N. Minard et al. 《Zeitschrift fur Physik C Particles and Fields》1995,69(1):379-392
A data sample of about 3.0 million hadronicZ decays collected by the ALEPH experiment at LEP in the years 1991 through 1994 is used to make an inclusive selection of
B hadron events. In this event sample 4227±140±252B* mesons in the decayB*→Bγ and 1944±108±161B**
u,d
mesons decaying into a B meson and a charged pion are reconstructed. Here and in the followingB**
u,d
denotes the eightL=1(bū) and (bd) states and their charge conjugate.
For the well establishedB* meson the following quantities are obtained:ΔM=M
B*−MB=(45.30±0.35±0.87) MeV/c2 andN
B*/(N
B+N
B*)=(77.1±2.6±7.0)%. The angular distribution of the photons in theB* rest frame is used to measure the relative contribution of longitudinalB* polarization states to beσ
L/(σ
L+σ
T)=(33±6±5)%. 相似文献
902.
V. O. Kur'yanov T. F. Zhelobetskaya A. E. Zemlyakov V. Ya. Chirva 《Chemistry of Natural Compounds》1993,29(1):103-106
The synthesis has been effected of derivatives of MDP having a spacer with an amino or carboxy group. The final stage of the synthesis was the condensation of Boc-L-Ala-D-iGln with 6-aminohexanol (followed by the two-stage replacement of the hydroxy by an azido group) or with benzyl 6-aminohexanoate.Simferopol' State University. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 122–125, January–February, 1993. 相似文献
903.
A PULSED LASER AND PULSE RADIOLYSIS STUDY OF AMPHIPHILIC CHLOROPHYLL DERIVATIVES WITH PDT ACTIVITY TOWARD MALIGNANT MELANOMA 总被引:1,自引:0,他引:1
L. Fiedor A. A. Gorman I. Hamblett V. Rosenbach-Belkin Y. Salomon A. Scherz I. Tregub 《Photochemistry and photobiology》1993,58(4):506-511
Two amphiphilic derivatives of chlorophyll, which have high potential as photodynamic therapy sensitizers for malignant melanoma have been investigated by a combination of laser flash photolysis and pulse radiolysis. It is shown that direct excitation of monomeric forms of these molecules in both hydrophilic and hydrophobic environments produces significant yields of the corresponding triplet states, which have been characterized in terms of spectral and kinetic parameters. In both environments, scavenging of the triplets by oxygen produces singlet oxygen, O2 (l Δ8 ), with essentially unit efficiency as evidenced by time-resolved IR luminescence measurements. 相似文献
904.
O. A. Rakitin E. A. Khaibullina T. I. Godovikova V. A. Ogurtsov L. I. Khimel'nitskii 《Chemistry of Heterocyclic Compounds》1993,29(8):952-954
Previously unreported furoxanenitrolic acids have been synthesized.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1117–1119, August, 1993. 相似文献
905.
Published in Teoreticheskaya i Matematicheskaya Fizika, Vol. 95, No. 2, pp. 183–186, May, 1993. 相似文献
906.
907.
S. Albeverio S. N. Lakaev J. I. Abdullaev 《Functional Analysis and Its Applications》2002,36(3):212-216
A Hamiltonian describing four bosons that move on a lattice and interact by means of pair zero-range attractive potentials is considered. A stronger version of the Hunziker–Van Vinter–Zhislin theorem on the essential spectrum is established. It is proved that the set of eigenvalues lying to the left of the essential spectrum is finite for any interaction energy of two bosons and is empty if this energy is sufficiently small. 相似文献
908.
909.
Yu. V. Belovitskaya I. V. Pekov E. R. Gobechiya N. A. Yamnova Yu. K. Kabalov N. V. Chukanov J. Schneider 《Crystallography Reports》2002,47(2):223-228
The crystal structures of two ancylite specimens from Khibiny massif (the Kola Peninsula, Russia)—ancylite-(Ce) from alkali hydrothermalites (Sr1.01Ca0.02Ba0.01)Σ1.04(Ce0.52La0.28Nd0.11Pr0.04 Sm0.01)Σ0.96(CO3)2(OH0.83F0.13)Σ0.96 · 0.9H2O and ancylite-(Ce) from carbonatites—have (Sr0.80Ca0.05Ba0.01)Σ0.86(Ce0.62La0.40Nd0.09Pr0.03) Σ1.14(CO3)2(OH0.99F0.15)Σ1.14 · 1.0H2O been refined by the Rietveld method. A focusing STOE-STADIP diffractometer with a bent Ge(111) primary monochromator was used (λ MoK α 1 radiation, 2.16° < 2θ < 54.98°; reflection number 237–437). All the computations for ancylite from alkali hydrothermalites were performed within the sp. gr. Pmc21, a = 5.0634(1) Å, b = 8.5898(1) Å, c = 7.2781(1) Å, V = 316.55(1) Å3, R wp = 1.90; the computations for ancylite from carbonatites were performed within the sp. gr. Pmcn, a = 5.0577(1) Å, b = 8.5665(2) Å, c = 7.3151(2) Å, V = 316.94(1) Å3, R wp = 2.38 in the anisotropic approximation of thermal vibrations of cations and oxygen atoms. 相似文献
910.
A generalization of strong regularity around a vertex subset C of a graph Γ, which makes sense even if Γis non-regular, is studied. Such a structure appears, together with a kind of distance-regularity around C , when an spectral bound concerning the so-called predistance polynomial of C is attained. As a main consequence of these results, it is shown that a regular (connected) graph Γwith d + 1 distinct eigenvalues is distance-regular, and its distance- d graph Γ d is strongly regular with parameters a = c , if and only if the number of vertices at distance d from each vertex satisfies an expression which depends only on the order of Γand the different eigenvalues of Γ. 相似文献