全文获取类型
收费全文 | 12630篇 |
免费 | 400篇 |
国内免费 | 503篇 |
专业分类
化学 | 3144篇 |
晶体学 | 250篇 |
力学 | 111篇 |
综合类 | 63篇 |
数学 | 8646篇 |
物理学 | 1319篇 |
出版年
2023年 | 54篇 |
2022年 | 107篇 |
2021年 | 121篇 |
2020年 | 120篇 |
2019年 | 288篇 |
2018年 | 266篇 |
2017年 | 185篇 |
2016年 | 180篇 |
2015年 | 193篇 |
2014年 | 327篇 |
2013年 | 759篇 |
2012年 | 441篇 |
2011年 | 820篇 |
2010年 | 754篇 |
2009年 | 883篇 |
2008年 | 924篇 |
2007年 | 951篇 |
2006年 | 750篇 |
2005年 | 573篇 |
2004年 | 499篇 |
2003年 | 428篇 |
2002年 | 514篇 |
2001年 | 275篇 |
2000年 | 284篇 |
1999年 | 303篇 |
1998年 | 265篇 |
1997年 | 195篇 |
1996年 | 255篇 |
1995年 | 232篇 |
1994年 | 208篇 |
1993年 | 161篇 |
1992年 | 140篇 |
1991年 | 76篇 |
1990年 | 59篇 |
1989年 | 59篇 |
1988年 | 47篇 |
1987年 | 47篇 |
1986年 | 35篇 |
1985年 | 107篇 |
1984年 | 62篇 |
1983年 | 59篇 |
1982年 | 69篇 |
1981年 | 86篇 |
1980年 | 47篇 |
1979年 | 42篇 |
1978年 | 42篇 |
1977年 | 52篇 |
1976年 | 51篇 |
1975年 | 29篇 |
1974年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
1.
2.
Kai Cheng Xiao-Shuai Zhang Jie An Cheng Li Ruo-Yun Zhang Run Ye Prof. Dr. Bang-Jiao Ye Prof. Dr. Bo Liu Prof. Dr. Yuan-Di Zhao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(31):7553-7560
Given their superior penetration depths, photosensitizers with longer absorption wavelengths present broader application prospects in photodynamic therapy (PDT). Herein, Ag2S quantum dots were discovered, for the first time, to be capable of killing tumor cells through the photodynamic route by near-infrared light irradiation, which means relatively less excitation of the probe compared with traditional photosensitizers absorbing short wavelengths. On modification with polydopamine (PDA), PDA-Ag2S was obtained, which showed outstanding capacity for inducing reactive oxygen species (increased by 1.69 times). With the addition of PDA, Ag2S had more opportunities to react with surrounding O2, which was demonstrated by typical triplet electron spin resonance (ESR) analysis. Furthermore, the PDT effects of Ag2S and PDA-Ag2S achieved at longer wavelengths were almost identical to the effects produced at 660 nm, which was proved by studies in vitro. PDA-Ag2S showed distinctly better therapeutic effects than Ag2S in experiments in vivo, which further validated the enhanced regulatory effect of PDA. Altogether, a new photosensitizer with longer absorption wavelength was developed by using the hitherto-unexplored photodynamic function of Ag2S quantum dots, which extended and enhanced the regulatory effect originating from PDA. 相似文献
3.
4.
G. Panina 《Central European Journal of Mathematics》2003,1(2):157-168
All 3-dimensional convex polytopes are known to be rigid. Still their Minkowski differences (virtual polytopes) can be flexible
with any finite freedom degree. We derive some sufficient rigidity conditions for virtual polytopes and present some examples
of flexible ones. For example, Bricard's first and second flexible octahedra can be supplied by the structure of a virtual
polytope. 相似文献
5.
6.
7.
For z1,z2,z3∈Zn, the tristance d3(z1,z2,z3) is a generalization of the L1-distance on Zn to a quantity that reflects the relative dispersion of three points rather than two. A tristance anticodeAd of diameter d is a subset of Zn with the property that d3(z1,z2,z3)?d for all z1,z2,z3∈Ad. An anticode is optimal if it has the largest possible cardinality for its diameter d. We determine the cardinality and completely classify the optimal tristance anticodes in Z2 for all diameters d?1. We then generalize this result to two related distance models: a different distance structure on Z2 where d(z1,z2)=1 if z1,z2 are adjacent either horizontally, vertically, or diagonally, and the distance structure obtained when Z2 is replaced by the hexagonal lattice A2. We also investigate optimal tristance anticodes in Z3 and optimal quadristance anticodes in Z2, and provide bounds on their cardinality. We conclude with a brief discussion of the applications of our results to multi-dimensional interleaving schemes and to connectivity loci in the game of Go. 相似文献
8.
In this paper we give a realization of some symmetric space G/K as a closed submanifold P of G. We also give several equivalent representations of the submanifold P. Some properties of the set gK∩P are also discussed, where gK is a coset space in G. 相似文献
9.
P Vincent A BrioudeC Journet S RabasteS.T Purcell J Le BrusqJ.C Plenet 《Journal of Non》2002,311(2):130-137
We report here the successful inclusion of carbon nanotubes (CNs) into a TiO2 matrix prepared by a sol-gel method. The presence of CNs in the sol-gel matrix and the structure of the film were analyzed principally by transmission electron microscopy. Complementary information about the behavior of embedded carbon nanotubes versus heat treatment and ion irradiation were obtained by X-ray photoelectron spectroscopy. The elaboration of an inorganic matrix containing embedded carbon nanotubes leads to a new nanocomposite. The possible applications of this nanocomposite are discussed. 相似文献
10.
Balázs Szendröi 《Mathematische Zeitschrift》2002,240(2):233-241
This note shows that a certain toric quotient of the quintic Calabi-Yau threefold in provides a counterexample to a recent conjecture of Cox and Katz concerning nef cones of toric hypersurfaces.
Received: 8 February 2001; in final form: 17 September 2001 / Published online: 1 February 2002 相似文献