全文获取类型
收费全文 | 3588篇 |
免费 | 182篇 |
国内免费 | 17篇 |
专业分类
化学 | 2390篇 |
晶体学 | 37篇 |
力学 | 84篇 |
数学 | 627篇 |
物理学 | 649篇 |
出版年
2023年 | 37篇 |
2022年 | 28篇 |
2021年 | 57篇 |
2020年 | 81篇 |
2019年 | 92篇 |
2018年 | 46篇 |
2017年 | 51篇 |
2016年 | 139篇 |
2015年 | 141篇 |
2014年 | 147篇 |
2013年 | 198篇 |
2012年 | 247篇 |
2011年 | 285篇 |
2010年 | 140篇 |
2009年 | 133篇 |
2008年 | 229篇 |
2007年 | 159篇 |
2006年 | 158篇 |
2005年 | 141篇 |
2004年 | 138篇 |
2003年 | 105篇 |
2002年 | 95篇 |
2001年 | 72篇 |
2000年 | 61篇 |
1999年 | 43篇 |
1998年 | 37篇 |
1997年 | 42篇 |
1996年 | 59篇 |
1995年 | 52篇 |
1994年 | 43篇 |
1993年 | 40篇 |
1992年 | 34篇 |
1991年 | 27篇 |
1990年 | 25篇 |
1989年 | 20篇 |
1988年 | 18篇 |
1987年 | 21篇 |
1986年 | 19篇 |
1985年 | 34篇 |
1984年 | 16篇 |
1983年 | 21篇 |
1982年 | 26篇 |
1981年 | 18篇 |
1980年 | 17篇 |
1979年 | 15篇 |
1978年 | 20篇 |
1977年 | 18篇 |
1976年 | 14篇 |
1975年 | 12篇 |
1973年 | 15篇 |
排序方式: 共有3787条查询结果,搜索用时 14 毫秒
71.
72.
Stephan Schwarz 《Physics in Perspective (PIP)》2011,13(4):401-432
I argue that research in the basic sciences during the German occupation of Denmark, which began on April 9, 1940, suffered
considerably, while research and development in technology enjoyed improved conditions as Danish industry moved toward the
requirements of the German wartime economy. Several organizations were created to further Danish–German scientific and cultural
collaboration or to manifest Danish cultural identity. The staff of the Danish Technical College and the number of their publications
remained largely constant although no papers appeared in British or American journals after 1941. Danish universities massively
resisted collaboration and maintained an illusion of “business as usual.” At the Niels Bohr Institute, laboratory equipment
continued to be constructed and developed and scientists continued to publish in Danish and other Scandinavian journals, although
they were increasingly isolated owing to their inability to obtain foreign scientific journals and to correspond with foreign
scientists. The Niels Bohr Institute was occupied from December 6, 1943, to February 3, 1944, a surprisingly short period,
owing, I argue, to strategic compromises in following incompatible orders from the German army, security police, and civilian
administration. Finally, I offer an interpretation of Niels Bohr’s vehemently negative reaction to Werner Heisenberg in their
meeting in Copenhagen in September 1941. 相似文献
73.
Sebastian Illes Stephan Theiss Hans-Peter Hartung Mario Siebler Marcel Dihné 《BMC neuroscience》2009,10(1):93
Background
The present work was performed to investigate the ability of two different embryonic stem (ES) cell-derived neural precursor populations to generate functional neuronal networks in vitro. The first ES cell-derived neural precursor population was cultivated as free-floating neural aggregates which are known to form a developmental niche comprising different types of neural cells, including neural precursor cells (NPCs), progenitor cells and even further matured cells. This niche provides by itself a variety of different growth factors and extracellular matrix proteins that influence the proliferation and differentiation of neural precursor and progenitor cells. The second population was cultivated adherently in monolayer cultures to control most stringently the extracellular environment. This population comprises highly homogeneous NPCs which are supposed to represent an attractive way to provide well-defined neuronal progeny. However, the ability of these different ES cell-derived immature neural cell populations to generate functional neuronal networks has not been assessed so far. 相似文献74.
Philipp Wagener Marcus Lau Sandra Breitung-Faes Arno Kwade Stephan Barcikowski 《Applied Physics A: Materials Science & Processing》2012,108(4):793-799
Combination of wet-grinding and laser fragmentation is a promising approach to advance both methods: Laser fragmentation will be more efficient when combined with mechanical treatment and wet-grinding may take advance of the abrasion-free laser process to achieve fabrication of smaller particles. By mechanical pre-treatment of zinc oxide microparticles in a stirred-media mill, the starting material is activated by generation of crystallographic defects, which strongly enhance the efficiency of subsequent laser fragmentation. Picosecond-laser irradiation of mechanically treated and untreated microparticles suspended in water yielded in colloidal zinc oxide nanoparticles. Furthermore, nanoparticle productivity and properties can be controlled by variation of anionic surfactant concentration. 相似文献
75.
Thomas Ihn Susanne Dröscher Stephan Schnez Helena Knowles Johannes Güttinger Magdalena Huefner Christoph Stampfer Yigal Meir Klaus Ensslin 《Solid State Communications》2012,152(15):1306-1310
We report two experiments on graphene nanostructures. The first was performed on a graphene nanoribbon, where the nature of electronic transport was investigated in detail. Electrons or holes are found to localize in pockets of the potential along the ribbon. Transport is governed by the joint action of localization and Coulomb interaction. The temperature-dependence of the conductance shows activated behavior at temperatures above a few Kelvin. The activation energy retraces the edges of Coulomb blockade diamonds found in nonlinear transport. In the second experiment the metallic tip of a low-temperature scanning force microscope was scanned above a graphene quantum dot. In addition to the familiar Coulomb blockade fringes, localized states are detected forming in the constrictions connecting the dot to source and drain. 相似文献
76.
Wonsuk Cha Wenjun Liu Ross Harder Ruqing Xu Paul H. Fuoss Stephan O. Hruszkewycz 《Journal of synchrotron radiation》2016,23(5):1241-1244
A method is presented to simplify Bragg coherent X‐ray diffraction imaging studies of complex heterogeneous crystalline materials with a two‐stage screening/imaging process that utilizes polychromatic and monochromatic coherent X‐rays and is compatible with in situ sample environments. Coherent white‐beam diffraction is used to identify an individual crystal particle or grain that displays desired properties within a larger population. A three‐dimensional reciprocal‐space map suitable for diffraction imaging is then measured for the Bragg peak of interest using a monochromatic beam energy scan that requires no sample motion, thus simplifying in situ chamber design. This approach was demonstrated with Au nanoparticles and will enable, for example, individual grains in a polycrystalline material of specific orientation to be selected, then imaged in three dimensions while under load. 相似文献
77.
78.
Gerhard Gompper Clemens Bechinger Stephan Herminghaus Rolf Isele-Holder U. Benjamin Kaupp Hartmut Löwen Holger Stark Roland G. Winkler 《The European physical journal. Special topics》2016,225(11-12):2061-2064
Locomotion of autonomous microswimmers is a fascinating field at the cutting edge of science. It combines the biophysics of self-propulsion via motor proteins, artificial propulsion mechanisms, swimming strategies at low Reynolds numbers, the hydrodynamic interaction of swimmers, and the collective motion and synchronisation of large numbers of agents. The articles of this Special Issue are based on the lecture notes of an international summer school, which was organized by the DFG Priority Programme 1726 “Microswimmers – From Single Particle Motion to Collective Behaviour” in the fall of 2015. The minireviews provide a broad overview of the field, covering both elementary and advanced material, as well as selected areas from current research. 相似文献
79.
Lordi V Gambin V Friedrich S Funk T Takizawa T Uno K Harris JS 《Physical review letters》2003,90(14):145505
Ga(1-x)In(x)N(y)As(1-y) is a promising material system for the fabrication of inexpensive "last-mile" optoelectronic components. However, details of its atomic arrangement and the relationship to observed optical properties is not fully known. Particularly, a blueshift of emission wavelength is observed after annealing. In this work, we use x-ray absorption fine structure to study the chemical environment around N atoms in the material before and after annealing. We find that as-grown molecular beam epitaxy material consists of a nearly random distribution of atoms, while postannealed material shows segregation of In toward N. Ab initio simulations show that this short-range ordering creates a more thermodynamically stable alloy and is responsible for blueshifting the emission. 相似文献
80.
Jrg Lambert Stephan Haiber Helmut Herzog 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2001,150(2):175
A new two-dimensional pulse sequence for T2* measurement of protons directly coupled to 13C spins is proposed. The sequence measures the tranverse relaxation time of heteronuclear proton single-quantum coherence under conditions of free precession and is therefore well suited to evaluate relaxation losses of proton magnetization during preparation delays of heteronuclear pulse experiments in analytical NMR. The relevant part of the pulse sequence can be inserted as a “building block” into any direct or inverse detecting H,C correlation pulse sequence if proton spin–spin relaxation is to be investigated. In this contribution, the building block is inserted into a HETCOR as well as into a HMQC pulse sequence. Experimental results for the HETCOR-based sequence are given. 相似文献