全文获取类型
收费全文 | 10547篇 |
免费 | 260篇 |
国内免费 | 24篇 |
专业分类
化学 | 6114篇 |
晶体学 | 206篇 |
力学 | 218篇 |
数学 | 1744篇 |
物理学 | 2549篇 |
出版年
2022年 | 123篇 |
2021年 | 207篇 |
2020年 | 163篇 |
2019年 | 221篇 |
2018年 | 203篇 |
2017年 | 192篇 |
2016年 | 351篇 |
2015年 | 293篇 |
2014年 | 382篇 |
2013年 | 819篇 |
2012年 | 559篇 |
2011年 | 624篇 |
2010年 | 478篇 |
2009年 | 448篇 |
2008年 | 526篇 |
2007年 | 504篇 |
2006年 | 426篇 |
2005年 | 361篇 |
2004年 | 319篇 |
2003年 | 309篇 |
2002年 | 257篇 |
2001年 | 189篇 |
2000年 | 176篇 |
1999年 | 131篇 |
1998年 | 129篇 |
1997年 | 108篇 |
1996年 | 116篇 |
1995年 | 141篇 |
1994年 | 88篇 |
1993年 | 73篇 |
1992年 | 100篇 |
1991年 | 60篇 |
1990年 | 93篇 |
1989年 | 78篇 |
1988年 | 85篇 |
1987年 | 72篇 |
1986年 | 78篇 |
1985年 | 117篇 |
1984年 | 140篇 |
1983年 | 84篇 |
1982年 | 83篇 |
1981年 | 90篇 |
1980年 | 99篇 |
1979年 | 68篇 |
1978年 | 86篇 |
1977年 | 91篇 |
1976年 | 75篇 |
1975年 | 64篇 |
1974年 | 53篇 |
1973年 | 46篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
991.
Leszek Krzemień Krzysztof Brzozowski Marcin Witkowski Micha? Zawada 《Optics Communications》2011,284(5):1247-1253
We present a method of Doppler-free laser frequency stabilization based on magnetically assisted rotation spectroscopy (MARS) which combines the Doppler-free velocity-selective optical pumping (VSOP) and magnetic rotation spectroscopy. The stabilization is demonstrated for the atomic rubidium transitions at 780 nm. The proposed method is largely independent of stray magnetic fields and does not require any modulation of the laser frequency. Moreover, the discussed method allows one to choose between locking the laser exactly to the line center, or with a magnetically-controlled shift to an arbitrary frequency detuned by up to several natural linewidths. This feature is useful in many situations, e.g. for laser cooling experiments. In addition to presenting the principle of the method, its theoretical background and peculiarities inherent to the repopulation VSOP are discussed. 相似文献
992.
We identify conditions under which correlations resulting from quantum measurements performed on macroscopic systems (systems composed of a number of particles of the order of the Avogadro number) can be described by local realism. We argue that the emergence of local realism at the macroscopic level is caused by an interplay between the monogamous nature of quantum correlations and the fact that macroscopic measurements do not reveal properties of individual particles. 相似文献
993.
We study the adhesion of an elastic sheet on a rigid spherical substrate. Gauss's Theorema Egregium shows that this operation necessarily generates metric distortions (i.e., stretching) as well as bending. As a result, a large variety of contact patterns ranging from simple disks to complex branched shapes are observed as a function of both geometrical and material properties. We describe these different morphologies as a function of two nondimensional parameters comparing, respectively, bending and stretching energies to adhesion. A complete configuration diagram is finally proposed. 相似文献
994.
Miscellanea
Contents to volume 19 相似文献995.
J. Sarnecki G. Gawlik M. Teodorczyk O. Jeremiasz R. Kozłowski D. Lipiński K. Krzyżak A. Brzozowski 《Opto-Electronics Review》2011,19(4):486-490
A new concept of edge illuminated solar cells (EISC) based on silicon epitaxial technique has been proposed. In this kind
of photovoltaic (PV) devices, sun-light illuminates directly a p-n junction through the edge of the structure which is perpendicular
to junction surface. The main motivation of the presented work is preparation of a working model of an edge-illuminated silicon
epitaxial solar cell sufficient to cooperation with a luminescent solar concentrator (LSC) consisted of a polymer foil doped
with a luminescent material. The technological processes affecting the cell I–V characteristic and PV parameters are considered. 相似文献
996.
Tomasz Gubica Jadwiga Stroka Andrzej Temeriusz Marianna Kańska 《Journal of Physical Organic Chemistry》2011,24(12):1229-1234
Ten nitrophenyl N‐glycosides have been studied electrochemically in neutral (at pH 7) water–organic solutions by cyclic voltammetry using static mercury drop electrode. For all compounds under investigation the two electrochemical processes have been observed: the four‐electron irreversible reduction of their nitro groups to the corresponding phenylhydroxylamine derivatives, as well as the two‐electron quasi‐reversible process between phenylhydroxylamine and nitroso derivatives. For three compounds the additional electrochemical processes have been also observed, which can be connected with the formation of azoxybenzene derivatives. The potentials of both redox processes: a two‐electron quasi‐reversible R? NHOH/R? NO (Ef) and four‐electron irreversible R? NO2/R? NHOH (Epc(I)) systems have been determined and discussed according to crystal structures of selected compounds. Ef and Epc(I) depended strongly on the positive mesomeric effect (caused by glycosidic nitrogen atom), as well as on the intramolecular hydrogen bond between electroactive nitro group and the hydrogen atom at the glycosidic atom observed in N‐o‐nitrophenyl‐2,3,4,6‐tetra‐O‐acetyl‐β‐D ‐glucopyranosylamine. Moreover, the chirality of selected reactants has had the pronounced effect on the Epc(I). Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
997.
Radomir Jasiński Magdalena Kwiatkowska Andrzej Barański 《Journal of Physical Organic Chemistry》2011,24(9):843-853
In spite of diversified electrophilicity of E‐2‐arylnitroethenes, their [4 + 2] cycloaddition reactions with cyclopentadiene leads to the corresponding 6‐endo‐aryl‐5‐exo‐nitronorbornenes and 6‐exo‐aryl‐5‐endo‐nitronorbornenes as the only reaction products. Stereoselectivity, substituent and solvent effects, and activation parameters, suggest that these reactions occur via a synchronous concerted mechanism on both competing pathways. The experimental results obtained are consistent with the data from B3LYP/6‐31G(d) calculations. Due to high electrophilicity of E‐2‐arylnitroethenes, the reactions studied should be considered as polar [4 + 2] cycloadditions. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
998.
P. Zaleski K. SzymańskiW. Olszewski M. BiernackaK. Perzyńska D. Satu?aA. Go J. Przewo?nikD.A. Zaj?c M. PylakL. Dobrzyński 《Physica B: Condensed Matter》2011,406(17):3196-3205
The lattice site occupation of 3d-type impurities in Cr3Si doped with Fe, Co and Ni were studied using the Extended X-ray Absorption Fine Structure (EXAFS) technique, X-rays and magnetic susceptibility measurements. The EXAFS measurements were performed particularly carefully on the K-edge of chromium and cobalt. EXAFS data strengthened by simulations of the spectra show unambiguously that the impurities are occupying mostly Cr-sites. The magnetic state of the alloys has been studied theoretically using the Wien2k code. It is observed that if calculations are not carried out on an appropriately fine mesh of points in k-space, one can get the result indicating ferromagnetism although the overall magnetic moment per formula unit is weak. 相似文献
999.
Oleg L. Berman Roman Ya. Kezerashvili Yurii E. Lozovik David W. Snoke R. Balili B. Nelsen L. Pfeiffer K. West 《Superlattices and Microstructures》2011
The theoretical and experimental status of the Bose–Einstein Condensation (BEC) of trapped quantum well (QW) polaritons in a microcavity is presented. The results of recent experiments that have shown the possibility to create an in-plane harmonic potential trap for a two-dimensional (2D) exciton polaritons in a cavity are discussed. We report the theory of BEC and of the trapped QW exciton polaritons in a microcavity. In addition, we study the BEC of trapped magnetoexciton polaritons in a graphene layer (GL) embedded in an optical microcavity in high magnetic field. In both cases the polaritons are considered to be in a harmonic potential trap. We compare the theoretical results with the existing experiments and discuss the experimental observation of predicted phenomena. 相似文献
1000.
This paper presents a system that accurately measures the distance travelled by ultrasound waves through the air. The simple design of the system and its obtained accuracy provide a tool for non-contact distance measurements required in the laser’s optical system that investigates the surface of the eyeball. 相似文献