全文获取类型
收费全文 | 21198篇 |
免费 | 3759篇 |
国内免费 | 2155篇 |
专业分类
化学 | 15062篇 |
晶体学 | 228篇 |
力学 | 1226篇 |
综合类 | 131篇 |
数学 | 2308篇 |
物理学 | 8157篇 |
出版年
2024年 | 44篇 |
2023年 | 447篇 |
2022年 | 508篇 |
2021年 | 780篇 |
2020年 | 866篇 |
2019年 | 878篇 |
2018年 | 824篇 |
2017年 | 701篇 |
2016年 | 1098篇 |
2015年 | 1004篇 |
2014年 | 1234篇 |
2013年 | 1622篇 |
2012年 | 1990篇 |
2011年 | 2023篇 |
2010年 | 1368篇 |
2009年 | 1297篇 |
2008年 | 1403篇 |
2007年 | 1220篇 |
2006年 | 1142篇 |
2005年 | 923篇 |
2004年 | 678篇 |
2003年 | 491篇 |
2002年 | 509篇 |
2001年 | 392篇 |
2000年 | 339篇 |
1999年 | 428篇 |
1998年 | 309篇 |
1997年 | 317篇 |
1996年 | 307篇 |
1995年 | 266篇 |
1994年 | 225篇 |
1993年 | 228篇 |
1992年 | 160篇 |
1991年 | 172篇 |
1990年 | 148篇 |
1989年 | 107篇 |
1988年 | 89篇 |
1987年 | 70篇 |
1986年 | 70篇 |
1985年 | 62篇 |
1984年 | 58篇 |
1983年 | 36篇 |
1982年 | 33篇 |
1981年 | 23篇 |
1980年 | 26篇 |
1978年 | 13篇 |
1976年 | 16篇 |
1975年 | 15篇 |
1973年 | 16篇 |
1968年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 810 毫秒
1.
Tian Xiu-Zhi Yang Rui Ma Jia-Jia Ni Yong-Hao Deng Hai-Bo Dai Lei Tan Jiao-Jun Zhang Mei-Yun Jiang Xue 《高分子科学》2022,40(7):789-798
Chinese Journal of Polymer Science - Antistatic and strength properties are of vital importance for polyurethane rubber used in moving parts of many industrial instruments. Herein, polyurethane was... 相似文献
2.
3.
Nonlinear Dynamics - This paper proposes an optimal parameter design of control scheme for mechanical systems by adopting the Stackelberg game theory. The goal of the control is to drive the... 相似文献
4.
Journal of Visualization - The increasing availability of spatiotemporal data provides unprecedented opportunities for understanding the structure of an urban area in terms of people’s... 相似文献
5.
Science China Mathematics - Linear factor models are familiar tools used in many fields. Several pioneering literatures established foundational theoretical results of the quasi-maximum likelihood... 相似文献
6.
The influence of different referencing methods on the accuracy of δ13C value measurement of ethanol fuel by gas chromatography/combustion/isotope ratio mass spectrometry 下载免费PDF全文
7.
Nanocomposite hydrogel consisting of Na‐montmorillonite with enhanced mechanical properties 下载免费PDF全文
Ting Li Shuangfei Xiang Piming Ma Huiyu Bai Weifu Dong Mingqing Chen 《Journal of Polymer Science.Polymer Physics》2015,53(14):1020-1026
A new kind of nanocomposite (NC) hydrogel with Na‐montmorillonite (MMT) is presented in this article. The NC hydrogels were synthesized by free radical copolymerization of acrylamide and (3‐acrylamidopropyl) trimethylammonium chloride (ATC) in the presence of MMT and N,N′‐methylene‐bis‐acrylamide used as chemical cross‐linker. Due to the cation‐exchange reaction between MMT and ATC (cationic monomer) during the synthesis of NC hydrogels, MMT platelets were considered chemical “plane” cross‐linkers, different from “point” cross‐linkers. With increasing amount of MMT, the crosslinking degree enhanced, causing a decrease of the swelling degree at equilibrium. Investigations of mechanical properties indicated that NC hydrogels exhibited enhanced strength and toughness, which resulted from chemical interaction between exfoliated MMT platelets and polymer chains in hydrogels. Dynamic shear measurements showed that both storage modulus and loss modulus increased with increasing MMT content. The idea described here provided a new route to prepare hydrogels with high mechanical properties by using alternative natural Na‐MMT. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1020–1026 相似文献
8.
9.
采用传统固相反应法制备了Ca0.9(NaCe)0.05Bi2 Nb2 O9铋层状无铅压电陶瓷.采用XRD、SEM、EDS及相关电学性能测试系统表征了样品的晶体结构、断面形貌、元素组成以及介电、压电、铁电等性能,探究不同烧结温度对于陶瓷性能的影响.结果表明:当烧结温度为1150℃时,样品的晶体结构单一均匀,呈现片层状结构,致密性较好,压电常数高达17 pC/N,介电损耗仅为0.42;,居里温度为908℃,并且具有很好的温度稳定性,说明固相反应法制备的Ca0.9(NaCe)0.05Bi2Nb2O9压电陶瓷最佳烧结温度为1150℃. 相似文献
10.
We investigate terahertz radiation(T-rays) from a pentacene organic diode at room temperature. The quantum chemistry calculation for frequency-related Huang–Rhys factor of pentacene is also carried out. The results demonstrate that the T-rays can come from a bending vibration of pentacene skeleton after the energy of pentacene exciton transferring to the vibrational excited state via electron–phonon coupling. Frequency and natural bond orbital analytics of pentacene and its derivatives are performed in order to explain the result and develop new materials to get higher emission. This work provides a new way to produce T-rays with a simple device at room temperature. 相似文献