全文获取类型
收费全文 | 36768篇 |
免费 | 888篇 |
国内免费 | 637篇 |
专业分类
化学 | 14472篇 |
晶体学 | 212篇 |
力学 | 2178篇 |
数学 | 10151篇 |
物理学 | 11280篇 |
出版年
2021年 | 345篇 |
2020年 | 454篇 |
2019年 | 301篇 |
2018年 | 392篇 |
2017年 | 486篇 |
2016年 | 592篇 |
2015年 | 700篇 |
2014年 | 846篇 |
2013年 | 1835篇 |
2012年 | 1552篇 |
2011年 | 1903篇 |
2010年 | 1219篇 |
2009年 | 1140篇 |
2008年 | 1789篇 |
2007年 | 1842篇 |
2006年 | 1922篇 |
2005年 | 1710篇 |
2004年 | 1400篇 |
2003年 | 1251篇 |
2002年 | 1137篇 |
2001年 | 1049篇 |
2000年 | 807篇 |
1999年 | 700篇 |
1998年 | 494篇 |
1997年 | 524篇 |
1996年 | 535篇 |
1995年 | 289篇 |
1994年 | 297篇 |
1993年 | 347篇 |
1992年 | 345篇 |
1991年 | 325篇 |
1990年 | 279篇 |
1989年 | 277篇 |
1988年 | 286篇 |
1987年 | 278篇 |
1986年 | 268篇 |
1985年 | 494篇 |
1984年 | 540篇 |
1983年 | 508篇 |
1982年 | 571篇 |
1981年 | 539篇 |
1980年 | 525篇 |
1979年 | 509篇 |
1978年 | 533篇 |
1977年 | 485篇 |
1976年 | 472篇 |
1975年 | 463篇 |
1974年 | 473篇 |
1973年 | 529篇 |
1972年 | 264篇 |
排序方式: 共有10000条查询结果,搜索用时 30 毫秒
61.
Rahul S. Patil Dr. Debasis Banerjee Cory M. Simon Prof. Jerry L. Atwood Dr. Praveen K. Thallapally 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(36):12618-12623
Separation of xenon and krypton is of industrial and environmental concern; the existing technologies use cryogenic distillation. Thus, a cost‐effective, alternative technology for the separation of Xe and Kr and their capture from air is of significant importance. Herein, we report the selective Xe uptake in a crystalline porous organic oligomeric molecule, noria, and its structural analogue, PgC‐noria, under ambient conditions. The selectivity of noria towards Xe arises from its tailored pore size and small cavities, which allows a directed non‐bonding interaction of Xe atoms with a large number of carbon atoms of the noria molecular wheel in a confined space. 相似文献
62.
Synthesis of Structurally Varied 1,3‐Disiloxanediols and Their Activity as Anion‐Binding Catalysts 下载免费PDF全文
Kayla M. Diemoz Sean O. Wilson Prof. Dr. Annaliese K. Franz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(51):18349-18353
A series of new 1,3‐disiloxanediols has been synthesized, including naphthyl‐substituted and unsymmetrical siloxanes, and demonstrated as a new class of anion‐binding catalysts. In the absence of anions, diffusion‐ordered spectroscopy (DOSY) displays self‐association of 1,3‐disiloxanediols through hydrogen‐bonding interactions. Binding constants determined for 1,3‐disiloxanediol catalysts indicate strong hydrogen‐bonding and anion‐binding abilities with unsymmetrical siloxanes displaying different hydrogen‐bonding abilities for each silanol group. 相似文献
63.
A Self‐Assembled Superhydrophobic Electrospun Carbon–Silica Nanofiber Sponge for Selective Removal and Recovery of Oils and Organic Solvents 下载免费PDF全文
Ming Hang Tai Benny Yong Liang Tan Jermyn Juay Dr. Darren D. Sun Prof. James O. Leckie 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(14):5395-5402
An oil spill needs timely cleanup before it spreads and poses serious environmental threat to the polluted area. This always requires the cleanup techniques to be efficient and cost‐effective. In this work, a lightweight and compressible sponge made of carbon–silica nanofibers is derived from electrospinning nanotechnology that is low‐cost, versatile, and readily scalable. The fabricated sponge has high porosity (>99 %) and displays ultra‐hydrophobicity and superoleophilicity, thus making it a suitable material as an oil adsorbent. Owing to its high porosity and low density, the sponge is capable of adsorbing oil up to 140 times its own weight with its sorption rate showing solution viscosity dependence. Furthermore, sponge regeneration and oil recovery are feasible by using either cyclic distillation or mechanical squeezing. 相似文献
64.
65.
A Series of Diamagnetic Pyridine Monoimine Rhenium Complexes with Different Degrees of Metal‐to‐Ligand Charge Transfer: Correlating 13C NMR Chemical Shifts with Bond Lengths in Redox‐Active Ligands 下载免费PDF全文
Dr. Daniel Sieh Prof. Dr. Clifford P. Kubiak 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(30):10638-10650
A set of pyridine monoimine (PMI) rhenium(I) tricarbonyl chlorido complexes with substituents of different steric and electronic properties was synthesized and fully characterized. Spectroscopic (NMR and IR) and single‐crystal X‐ray diffraction analyses of these complexes showed that the redox‐active PMI ligands are neutral and that the overall electronic structure is little affected by the choices of the substituent at the ligand backbone. One‐ and two‐electron reduction products were prepared from selected starting compounds and could also be characterized by multiple spectroscopic methods and X‐ray diffraction. The final product of a one‐electron reduction in THF is a diamagnetic metal–metal‐bonded dimer after loss of the chlorido ligand. Bond lengths in and NMR chemical shifts of the PMI ligand backbone indicate partial electron transfer to the ligand. Two‐electron reduction in THF also leads to the loss of the chlorido ligand and a pentacoordinate complex is obtained. The comparison with reported bond lengths and 13C NMR chemical shifts of doubly reduced free pyridine monoaldimine ligands indicates that both redox equivalents in the doubly reduced rhenium complex investigated here are located in the PMI ligand. With diamagnetic complexes varying over three formal reduction stages at the PMI ligand we were, for the first time, able to establish correlations of the 13C NMR chemical shifts with the relevant bond lengths in redox‐active ligands over a full redox series. 相似文献
66.
67.
68.
PAUL SOBAJE 《Transformation Groups》2015,20(4):1141-1153
69.
70.
A model for the mechanics of woven fabrics is developed in the framework of two-dimensional elastic surface theory. Thickness effects are modeled indirectly in terms of appropriate constitutive equations. The model accounts for the strain of the fabric and additional effects associated with the normal bending, geodesic bending, and twisting of the constituent fibers. 相似文献