全文获取类型
收费全文 | 1807篇 |
免费 | 84篇 |
国内免费 | 8篇 |
专业分类
化学 | 1128篇 |
晶体学 | 11篇 |
力学 | 107篇 |
数学 | 327篇 |
物理学 | 326篇 |
出版年
2023年 | 12篇 |
2022年 | 30篇 |
2021年 | 48篇 |
2020年 | 48篇 |
2019年 | 34篇 |
2018年 | 33篇 |
2017年 | 37篇 |
2016年 | 68篇 |
2015年 | 75篇 |
2014年 | 62篇 |
2013年 | 100篇 |
2012年 | 120篇 |
2011年 | 147篇 |
2010年 | 68篇 |
2009年 | 81篇 |
2008年 | 131篇 |
2007年 | 105篇 |
2006年 | 90篇 |
2005年 | 91篇 |
2004年 | 76篇 |
2003年 | 57篇 |
2002年 | 51篇 |
2001年 | 22篇 |
2000年 | 24篇 |
1999年 | 11篇 |
1998年 | 12篇 |
1997年 | 20篇 |
1996年 | 14篇 |
1995年 | 10篇 |
1994年 | 15篇 |
1993年 | 15篇 |
1992年 | 11篇 |
1991年 | 12篇 |
1990年 | 13篇 |
1989年 | 16篇 |
1988年 | 12篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1981年 | 13篇 |
1980年 | 9篇 |
1979年 | 11篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1974年 | 5篇 |
1973年 | 3篇 |
1970年 | 3篇 |
排序方式: 共有1899条查询结果,搜索用时 15 毫秒
121.
Ortiz W Krueger BP Kleiman VD Krause JL Roitberg AE 《The journal of physical chemistry. B》2005,109(23):11512-11519
We present a theoretical investigation of energy transfer in the phenylene ethynelene dendrimer known as the nanostar. Data from extensive molecular dynamics simulations are used to model the dynamical effects caused by torsional motion of the phenyl groups. We compare rate constants for energy transfer between the two-ring chromophore and the three-ring chromophore obtained via the F?rster model, the ideal dipole approximation (IDA), and the transition density cube (TDC) method, which has as its limit an exact representation of the Coulombic coupling. We find that the rate constants obtained with the TDC are extremely sensitive to the phenyl group rotation, whereas the constants computed with the F?rster model and the IDA are not. The implications of these results for the interpretation of recent pump-probe experiments on the nanostar are discussed in detail. Finally, we predict the temperature dependence of the rate constant for energy transfer. 相似文献
122.
123.
We have developed a dual-channel optical coherence tomography-Indocyanine Green dye (OCT-ICG) fluorescence system based on a previously reported ophthalmic OCT confocal imaging system. The confocal channel is tuned to the fluorescence wavelength range of the ICG, and light from the same optical source is used to generate the OCT image and to excite the ICG fluorescence. The system enables the clinician to visualize simultaneously en face OCT slices and corresponding ICG angiograms of the ocular fundus, displayed side by side. C-scan (constant depth) and B-scan (cross section) images are collected by a fast en face scan (T scan). The pixel-to-pixel correspondence between the OCT and angiography images allows the user to capture OCT B scans precisely at selected points on the ICG confocal images. 相似文献
124.
We consider an interacting particle system given by the Glauber + Kawasaki dynamics. It is known that this process has a reaction diffusion equation as hydrodynamic limit. The ergodicity of this process in the presence of a metastable state (double well potential) was recently proved by S. Brassesco et al. In this Letter we prove that, in the limit, as ε → 0, the expected value of each spin converges to the global minimizer of the potential. We also prove decay of correlations of the ergodic measure.AMS Subject Classification (2000). 60K35 (82C22, 82C31)This work was partially supported by CNPq 相似文献
125.
We define cheat sensitive cryptographic protocols between mistrustful parties as protocols which guarantee that, if either cheats, the other has some nonzero probability of detecting the cheating. We describe an unconditionally secure cheat sensitive nonrelativistic bit commitment protocol which uses quantum information to implement a task which is classically impossible; we also describe a simple relativistic protocol. 相似文献
126.
127.
Ian J.S. Fairlamb Anant R. Kapdi Jason M. Lynam Richard J.K. Taylor Adrian C. Whitwood 《Tetrahedron》2004,60(27):5711-5718
A new palladium(II) precatalyst for Suzuki cross-coupling of aryl halides and organoboronic acids has been identified, namely bis(triphenylphosphine)palladium(II)succinimide [(Ph3P)2Pd(N-Succ)2] 2. The precatalyst is easily prepared from palladium(0) precursors, such as (Ph3P)4Pd or Pd2dba3·CHCl3/Ph3P and succinimide, is air, light and moisture stable, and may be employed with a variety of substrates to give the cross-coupled products, in good yields and in reasonable time, at relatively low catalyst loadings. 相似文献
128.
Brown EJ Whitwood AC Walton PH Duhme-Klair AK 《Dalton transactions (Cambridge, England : 2003)》2004,(16):2458-2462
The butoxy- and methoxy-derivatives (HLc, and HLb, respectively) of 1-[(ethoxycarbonyl)methyl]-3-hydroxy-2-(1H)-pyridinone, HLa, were synthesized by transesterification and the mononuclear complexes [MoO2(L(a-c))2] were obtained by the reaction of the ligands with molybdenyl acetylacetonate. The three complexes were fully characterized by (1)H and (13)C NMR spectroscopy, mass spectrometry and elemental analyses. A variable temperature NMR study showed that the N-substituents do not have a significant influence on the racemisation process of the complexes. The comparison of the crystal structure of [MoO2(Lb)2] with [MoO2(La)2] confirmed that an additional methylene group does not affect the immediate coordination environment of the molybdenum centre. The methoxy-derivative HLb was also found to produce a dinuclear complex of composition [(MoO2(Lb)O)2], the structure of which was determined by X-ray diffraction. 相似文献
129.
Let L be a number field containing the r–th roots of unity. Starting with the Rankin-Selberg convolution of a metaplectic Eisenstein series on the r–fold cover of GL(2) with itself, we construct a Dirichlet series defined over L whose coefficients involve the r–th order twists of a fixed Hecke L–function. We then observe that a group of functional equations can be naturally associated with this construction. Combining this with the convexity theorem for holomorphic functions of several complex variables, we show that this object, as a function of two complex variables, admits meromorphic continuation to 2. As an application, we obtain asymptotic formulae for mean square values of the r–th order twists of an arbitrary Hecke L–function defined over L. Mathematics Subject Classification (1991) 11R42, 11F66, 11F67, 11F70, 11M41, 11R47 相似文献
130.
We report a system capable of sequentially acquiring two en-face images of different depth resolutions. The two images are generated by use of different principles, optical coherence tomography (OCT) and confocal microscopy, and have depth resolutions, at present, of better than 20 microm and over 0.12 mm, respectively. The lower-depth-resolution image is ideal for target positioning before collection of stacks of en-face OCT images. Switching between the two types of image by flipping an opaque screen in the reference arm, coupled with self-adjusting gain operation of avalanche photodiodes in the receiver. We illustrate the usefulness of the system by imaging a leaf and an optic nerve in vivo. 相似文献