全文获取类型
收费全文 | 2540篇 |
免费 | 65篇 |
国内免费 | 8篇 |
专业分类
化学 | 1725篇 |
晶体学 | 23篇 |
力学 | 32篇 |
数学 | 564篇 |
物理学 | 269篇 |
出版年
2020年 | 45篇 |
2019年 | 29篇 |
2018年 | 17篇 |
2017年 | 25篇 |
2016年 | 42篇 |
2015年 | 68篇 |
2014年 | 52篇 |
2013年 | 92篇 |
2012年 | 92篇 |
2011年 | 99篇 |
2010年 | 75篇 |
2009年 | 58篇 |
2008年 | 118篇 |
2007年 | 110篇 |
2006年 | 95篇 |
2005年 | 102篇 |
2004年 | 79篇 |
2003年 | 63篇 |
2002年 | 50篇 |
2001年 | 22篇 |
2000年 | 32篇 |
1999年 | 25篇 |
1998年 | 30篇 |
1997年 | 22篇 |
1996年 | 22篇 |
1995年 | 26篇 |
1994年 | 27篇 |
1993年 | 35篇 |
1992年 | 28篇 |
1991年 | 18篇 |
1989年 | 25篇 |
1988年 | 30篇 |
1987年 | 30篇 |
1985年 | 34篇 |
1984年 | 46篇 |
1983年 | 26篇 |
1982年 | 20篇 |
1981年 | 31篇 |
1980年 | 38篇 |
1979年 | 23篇 |
1978年 | 23篇 |
1977年 | 26篇 |
1976年 | 22篇 |
1975年 | 26篇 |
1974年 | 26篇 |
1967年 | 16篇 |
1966年 | 16篇 |
1965年 | 16篇 |
1964年 | 16篇 |
1956年 | 24篇 |
排序方式: 共有2613条查询结果,搜索用时 296 毫秒
961.
Electrophoretic methods for analysis of urinary polypeptides in IgA-associated renal diseases 总被引:2,自引:0,他引:2
Julian BA Wittke S Novak J Good DM Coon JJ Kellmann M Zürbig P Schiffer E Haubitz M Moldoveanu Z Calcatera SM Wyatt RJ Sýkora J Sládková E Hes O Mischak H McGuire BM 《Electrophoresis》2007,28(23):4469-4483
We evaluated the utility of SDS-PAGE/Western blot and CE coupled with MS (CE-MS) for detection of urinary polypeptide biomarkers of renal disease in patients with IgA-associated glomerulonephritides. In a reference cohort of 402 patients with various renal disorders and 207 healthy controls, we defined CE-MS patterns of renal damage and IgA nephropathy (IgAN). In a blinded analysis of a separate cohort of patients with IgAN (n = 10), Henoch-Schoenlein purpura (HSP) with nephritis (n = 10), and IgA-associated glomerulonephritis due to hepatitis C virus (HCV)-induced cirrhosis (n = 9), and healthy controls (n = 12), we compared SDS-PAGE/Western blot and CE-MS against clinical urinalysis for detection of urinary proteins/polypeptides. Urinalysis indicated proteinuria for 50, 90, and 33% of patients, respectively, and for none of the healthy controls. SDS-PAGE/Western blot showed urinary polypeptides abnormality for 90, 80, and 67% of patients, respectively, and for none of the healthy controls. CE-MS indicated a Renal Damage Pattern in 80, 80, and 100 of patients, respectively, and in 17% of healthy controls, with the more specific IgAN Pattern in 90, 90, and 1%, respectively, and in none of the healthy controls. Based on differences in CE-MS patterns, the disease mechanisms may differ among various IgA-associated glomerulonephritides. These exploratory findings should be evaluated in a prospective study with contemporaneous renal biopsy and urinary testing. If validated, it may be feasible to adapt the CE-MS methodology to develop novel tests to detect renal injury at earlier stages, assess clinical manifestations, and monitor responses to therapy in patients with IgA-associated renal diseases. 相似文献
962.
Przystawik A Radcliffe P Diederich T Döppner T Tiggesbäumker J Meiwes-Broer KH 《The Journal of chemical physics》2007,126(18):184306
Photoelectron spectra of neutral silver trimers, grown in ultracold helium nanodroplets, are recorded after ionization with laser pulses via a strong optical resonance of this species. Varying the photon energy reveals that direct vertical two-photon ionization is hindered by a rapid relaxation into the lower edge of a long-living excited state manifold. An analysis of the ionization threshold of the embedded trimer yields an ionization potential of 5.74+/-0.09 eV consistent with the value found in the gas phase. The asymmetrical form of the electron energy spectrum, which is broadened toward lower kinetic energies, is attributed to the influence of the matrix on the photoionization process. The lifetime of the excited state was measured in a two-color pump-probe experiment to be 5.7+/-0.6 ns. 相似文献
963.
The recently developed reduced multireference coupled-cluster method with singles and doubles (RMR CCSD), which is perturbatively corrected for triples [RMR CCSD(T)], is employed to compute binding energies of nine transition metal ions with CH2. Unlike analogous compounds involving main-group elements, the MCH2+ (M=Sc to Cu) transition metal complexes often exhibit a non-negligible multireference character. The authors thus employ the RMR CCSD(T) method, which represents an extension of the standard single-reference (SR) CCSD(T) method and can account for multireference effects, while employing only small reference spaces. In this way the role of quasidegeneracy effects on the binding energies of these complexes can be assessed at a higher SD(T) level than is possible with the widely used ab initio methods, namely, with the standard SR CCSD(T) approach, and provide a new benchmark for these quantities. The difference between the RMR and the standard CCSD(T) methods becomes particularly evident when considering nonequilibrium geometries. 相似文献
964.
We determined the isotropic, isothermal compressibility of ubiquitin by pressure tuning spectral holes burnt into the red edge of the absorption spectrum of the single tyrosine residue. The pressure shift is perfectly linear with burn frequency. From these data, a compressibility of 0.086 GPa(-1) in the local environment of the tyrosine residue could be determined. This value fits nicely into the range known for proteins. Although the elastic behavior at low temperatures does not show any unusual features, the pressure tuning behavior at room temperature is quite surprising: the pressure-induced spectral shift is close to zero, even up to very high pressure levels of 0.88 GPa, well beyond the denaturation point. The reason for this behavior is attributed to equally strong blue as well as red spectral pressure shifts resulting in an average pressure-induced solvent shift that is close to zero. 相似文献
965.
Microchimica Acta - Coherent anti-Stokes Raman scattering (CARS) was evaluated and applied to process monitoring in chip-based high-performance liquid chromatography (HPLC). By stimulating the... 相似文献
966.
David Urmann Charlotte Lorenz Stephanie M. Linker Markus Braun Josef Wachtveitl Christian Bamann 《Photochemistry and photobiology》2017,93(3):782-795
Color‐tuned variants of channelrhodopsins allow for selective optogenetic manipulation of different host cell populations. Chrimson is the channelrhodopsin with the longest wavelength absorbance maximum. We characterize its photochemical properties at different pH values corresponding to two protonation states of the counterion for the protonated Schiff base. Both states will lead to a functional channel opening, but the route is different as reflected in the photochemical states observed spectroscopically. The light‐induced isomerization kinetics change with the local electrostatic environment, becoming faster with the presence of an anionic counterion. The spectral effect is stronger on the ground‐state energy surface. From the excited state, a bifurcated pathway leads to the electronic ground state resulting in a pronounced excitation wavelength dependence. The subsequent steps in the photocycles at pH 6 and pH 9.5 differ in the accumulation of states with a protonated and deprotonated Schiff base, respectively, that can be correlated with the open channel. Therefore, different protonation states are preserved in the open and the initial states. Chrimson's photocycle at alkaline pH shows features observed in other rhodopsins without an internal proton donor to the Schiff base, but it accumulates an intermediate with an even longer lifetime reflecting slow recovery of the initial state. 相似文献
967.
968.
Ligia L. Cristea Josef Dick Gunther Leobacher Friedrich Pillichshammer 《Numerische Mathematik》2007,105(3):413-455
In this paper we investigate multivariate integration in reproducing kernel Sobolev spaces for which the second partial derivatives
are square integrable. As quadrature points for our quasi-Monte Carlo algorithm we use digital (t,m,s)-nets over which are randomly digitally shifted and then folded using the tent transformation. For this QMC algorithm we show that the
root mean square worst-case error converges with order for any ɛ > 0, where 2
m
is the number of points. A similar result for lattice rules has previously been shown by Hickernell.
Ligia L. Cristea is supported by the Austrian Research Fund (FWF), Project P 17022-N 12 and Project S 9609.
Josef Dick is supported by the Australian Research Council under its Center of Excellence Program.
Gunther Leobacher is supported by the Austrian Research Fund (FWF), Project S 8305.
Friedrich Pillichshammer is supported by the Austrian Research Fund (FWF), Project P 17022-N 12, Project S 8305 and Project
S 9609. 相似文献
969.
Doná E Loerting T Penner S Minca M Menzel A Bertel E Schoiswohl J Berkebile S Netzer FP Zucca R Redinger J 《Physical review letters》2007,98(18):186101
Phase transitions in a quasi-one-dimensional surface system on a metal substrate are investigated as a function of temperature. Upon cooling the system shows a loss of long-range order, fluctuations, and a transition into an inhomogeneous ground state due to competition of local adsorbate-adsorbate interactions with an incommensurate charge density wave. This agrees with a general phase diagram for correlated systems and high-temperature superconductors. The model surface system allows direct imaging of the fluctuations and the glassy inhomogeneous ground state by scanning tunneling microscopy. 相似文献
970.
Yoshifuku S Chen S McMahon EM Yoshikawa A Sengupta PP Korinek J Belohlavek M 《Ultrasonics》2007,46(2):109-118