全文获取类型
收费全文 | 46202篇 |
免费 | 4737篇 |
国内免费 | 5556篇 |
专业分类
化学 | 29060篇 |
晶体学 | 920篇 |
力学 | 3038篇 |
综合类 | 380篇 |
数学 | 9818篇 |
物理学 | 13279篇 |
出版年
2024年 | 129篇 |
2023年 | 410篇 |
2022年 | 753篇 |
2021年 | 1030篇 |
2020年 | 1442篇 |
2019年 | 1351篇 |
2018年 | 1279篇 |
2017年 | 1685篇 |
2016年 | 2006篇 |
2015年 | 1694篇 |
2014年 | 2245篇 |
2013年 | 4086篇 |
2012年 | 3011篇 |
2011年 | 3199篇 |
2010年 | 2637篇 |
2009年 | 2964篇 |
2008年 | 2938篇 |
2007年 | 3086篇 |
2006年 | 2637篇 |
2005年 | 2303篇 |
2004年 | 2134篇 |
2003年 | 1916篇 |
2002年 | 1810篇 |
2001年 | 1318篇 |
2000年 | 1230篇 |
1999年 | 1122篇 |
1998年 | 996篇 |
1997年 | 793篇 |
1996年 | 708篇 |
1995年 | 608篇 |
1994年 | 566篇 |
1993年 | 432篇 |
1992年 | 376篇 |
1991年 | 236篇 |
1990年 | 199篇 |
1989年 | 146篇 |
1988年 | 155篇 |
1987年 | 111篇 |
1986年 | 111篇 |
1985年 | 106篇 |
1984年 | 103篇 |
1983年 | 53篇 |
1982年 | 99篇 |
1981年 | 74篇 |
1980年 | 42篇 |
1979年 | 47篇 |
1978年 | 27篇 |
1977年 | 19篇 |
1976年 | 16篇 |
1973年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Patrick Imrie Jianyong Jin 《Journal of polymer science. Part A, Polymer chemistry》2022,60(2):149-174
4D printing is an exciting branch of additive manufacturing. It relies on established 3D printing techniques to fabricate objects in much the same way. However, structures which fall into the 4D printed category have the ability to change with time, hence the “extra dimension.” The common perception of 4D printed objects is that of macroscopic single-material structures limited to point-to-point shape change only, in response to either heat or water. However, in the area of polymer 4D printing, recent advancements challenge this understanding. A host of new polymeric materials have been designed which display a variety of wonderful effects brought about by unconventional stimuli, and advanced additive manufacturing techniques have been developed to accommodate them. As a result, the horizons of polymer 4D printing have been broadened beyond what was initially thought possible. In this review, we showcase the many studies which evolve the very definition of polymer 4D printing, and reveal emerging areas of research integral to its advancement. 相似文献
2.
Shilin Jiang Dr. Yalan Liu Dr. Lin Wang Prof. Zhifang Chai Prof. Wei-Qun Shi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(60):e202201145
The coordination chemistry of f-block elements (lanthanide and actinide) in molten salts has become a resounding topic in view of its great importance to the research and development (R&D) of molten salt reactors and pyroprocessing. In this Review article, a general overview of the coordination chemistry of f-block elements in molten salts is provided including past achievements and recent advances. Particular emphases are placed on the oxidation state, speciation, and solution structure of f-block metal ions in molten salts, as well as their relationships with the salt composition. Furthermore, this review briefly discusses the spectroscopic and theoretical methods that complement each other in revealing the coordination properties. 相似文献
3.
Dr. Yolimar Gil Dr. Alejandro Castro-Alvarez Dr. Pablo Fuentealba Prof. Evgenia Spodine Dr. Daniel Aravena 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(48):e202200336
Enhancement of axial magnetic anisotropy is the central objective to push forward the performance of Single-Molecule Magnet (SMM) complexes. In the case of mononuclear lanthanide complexes, the chemical environment around the paramagnetic ion must be tuned to place strongly interacting ligands along either the axial positions or the equatorial plane, depending on the oblate or prolate preference of the selected lanthanide. One classical strategy to achieve a precise chemical environment for a metal centre is using highly structured, chelating ligands. A natural approach for axial-equatorial control is the employment of macrocycles acting in a belt conformation, providing the equatorial coordination environment, and leaving room for axial ligands. In this review, we present a survey of SMMs based on the macrocycle belt motif. Literature systems are divided in three families (crown ether, Schiff-base and metallacrown) and their general properties in terms of structural stability and SMM performance are briefly discussed. 相似文献
4.
Tomoyuki Nakatsuka 《Mathematische Nachrichten》2021,294(1):98-117
We study the existence of a time‐periodic solution with pointwise decay properties to the Navier–Stokes equation in the whole space. We show that if the time‐periodic external force is sufficiently small in an appropriate sense, then there exists a time‐periodic solution of the Navier–Stokes equation such that and uniformly in as . Our solution decays faster than the time‐periodic Stokes fundamental solution and the faster decay of its spatial derivatives of higher order is also described. 相似文献
5.
Jiraya Kiriratnikom Xun Zhang Xiaohan Cao Bo Chu Chengjian Zhang Xinghong Zhang 《Journal of polymer science. Part A, Polymer chemistry》2022,60(15):2262-2268
Facile construction of sulfur-rich polymers using readily available raw chemicals is an area aggressively pursued but challenging. Herein we use common feedstocks of ethylene oxide (EO), propylene oxide (PO), and carbonyl sulfide (COS) to synthesize copoly(thioether)s which are traditionally produced from unpleasant and difficult to store episulfides. In this protocol, the EO/COS coupling selectively generates a pure poly(ethylene sulfide) (PES) with melting temperature (Tm) values up to 172°C and high yields up to 98%. The EO/PO/COS terpolymerization leads to the incorporation of soft poly(propylene sulfide) (PPS) and hard PES segments together, affording a random PES-co-PPS copoly(thioether) with the complete consumption of EO and PO. Additionally, by simply varying the EO/PO feeding ratio, the obtained copoly(thioether)s possess tunable thermal properties, Tm values in the range of 76–144°C, and excellent solubility. These copolymerizations are conducted in one-pot/one-step at industrially favored reaction temperatures of 100–120°C using catalysts of common organic bases, suggesting a facile and practical manner. Especially, the copoly(thioether) exhibits high refractive indices up to 1.68 owing to its high sulfur content, suggesting a broad application prospect in optical materials. 相似文献
6.
《Mendeleev Communications》2022,32(1):105-108
A mixed-metal 1D coordination polymer [CaCu(HBTC)2(H2O)8]n (where H3BTC – benzene-1,3,5-tric arboxylic acid) was obtained in a solvothermal synthesis of a well-known copper-containing metal–organic framework [Cu3(BTC)2(H2O)3]n (HKUST-1) in autoclaves 3D-printed from commercial polypropylene. This material was a source of calcium ions, apparently, leaking from a colorant (calcium carbonate) promoted by glacial acetic acid as a modulator used to produce large single crystals of HKUST-1. This finding was confirmed by elemental analysis and a model experiment that resulted in a new calcium-based 1D coordination polymer [Ca(H2BTC)2(H2O)5]n under the same solvothermal conditions with no copper or calcium salts put into a 3D-printed autoclave. 相似文献
7.
Tapasi Chand Laxmikanta Khamari Deepak Chopra Saptarshi Mukherjee Manmohan Kapur 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(43):e202200723
A one-step Rh-catalyzed site-selective ortho-C−H alkynylation of perylene as well as naphthalene mono- and diimides is reported. A single step regioselective access to ortho-C−H alkynylated derivatives of these ryleneimides not only increases the step economy of the ortho-functionalization on these dyes but also provides a quick access route towards highly functionalized dyes that have potential optoelectronic applications. Increased solubility of tetra(triisopropylsilyl)acetylenyl PDIs in organic solvents greatly enhances their utility for further derivatization. 相似文献
8.
9.
10.