全文获取类型
收费全文 | 28483篇 |
免费 | 5134篇 |
国内免费 | 3807篇 |
专业分类
化学 | 21013篇 |
晶体学 | 361篇 |
力学 | 1709篇 |
综合类 | 266篇 |
数学 | 3369篇 |
物理学 | 10706篇 |
出版年
2024年 | 38篇 |
2023年 | 629篇 |
2022年 | 751篇 |
2021年 | 951篇 |
2020年 | 1280篇 |
2019年 | 1282篇 |
2018年 | 1064篇 |
2017年 | 950篇 |
2016年 | 1431篇 |
2015年 | 1462篇 |
2014年 | 1729篇 |
2013年 | 2198篇 |
2012年 | 2664篇 |
2011年 | 2671篇 |
2010年 | 1872篇 |
2009年 | 1806篇 |
2008年 | 1967篇 |
2007年 | 1760篇 |
2006年 | 1631篇 |
2005年 | 1413篇 |
2004年 | 1046篇 |
2003年 | 837篇 |
2002年 | 799篇 |
2001年 | 706篇 |
2000年 | 520篇 |
1999年 | 519篇 |
1998年 | 438篇 |
1997年 | 409篇 |
1996年 | 392篇 |
1995年 | 355篇 |
1994年 | 306篇 |
1993年 | 282篇 |
1992年 | 231篇 |
1991年 | 208篇 |
1990年 | 151篇 |
1989年 | 134篇 |
1988年 | 107篇 |
1987年 | 75篇 |
1986年 | 62篇 |
1985年 | 74篇 |
1984年 | 59篇 |
1983年 | 41篇 |
1982年 | 26篇 |
1981年 | 22篇 |
1980年 | 19篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1975年 | 5篇 |
1957年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
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
2.
The chiral phase transition and equation of state are studied within a novel self-consistent mean-field approximation of the two-flavor Nambu-Jona-Lasinio model. In this newly developed model, modifications to the chemical μ and chiral chemical \begin{document}$\mu_5$\end{document} ![]()
![]()
potentials are naturally included by introducing vector and axial-vector channels from Fierz-transformed Lagrangian to the standard Lagrangian. In the proper-time scheme, the chiral phase transition is a crossover in the \begin{document}$T-\mu$\end{document} ![]()
![]()
plane. However, when \begin{document}$\mu_5$\end{document} ![]()
![]()
is incorporated, our study demonstrates that a first order phase transition may emerge. Furthermore, the chiral imbalance will soften the equation of state of quark matter. The mass-radius relationship and tidal deformability of quark stars are calculated. The maximum mass and radius decrease as \begin{document}$\mu_5$\end{document} ![]()
![]()
increases. Our study also indicates that the vector and axial-vector channels exhibit an opposite influence on the equation of state. 相似文献
3.
合成了一种多级孔芳香骨架材料(PAF-70); 使用由氨基修饰过的单体, 应用该合成策略得到了同样具有窄分布介孔的含有氨基活性位点的PAF材料, 并通过硫脲单体与其氨基活性位点的反应, 将硫脲基团引入PAF-70材料中, 获得了含有硫脲催化位点的材料(PAF-70-thiourea). 氮气吸附-脱附测试结果显示, PAF-70存在孔径分布较窄的介孔, 介孔孔径为3.8 nm, 与模拟计算值(约3.7 nm)吻合. 热重分析结果表明, PAF-70具有很高的热稳定性. PAF-70在大多数溶剂中可以稳定存在, 具有良好的化学稳定性. 将PAF-70-thiourea作为催化剂, 应用在N-溴代琥珀酰亚胺(NBS)氧化醇类的反应中, 其表现出较高的催化活性、 较高的稳定性和广泛的底物适用性. 与含有相同硫脲催化位点的金属有机框架(MOF)材料(IRMOF-3-thiourea)作为催化剂对比, 进一步证实PAFs材料非常适合作为催化有机反应的固载平台. 相似文献
4.
5.
Herein, we successfully construct the 3D biocompatible graphene through crosslinking 2D graphene nanosheet onto carbon fiber paper with poly(diallyldimethylammonium chloride) (PDDA) as anode of the alcohol biofuel cell. Compared with the bioanode without 3D graphene, the current density and output power of PDDA-graphene-ADH bioanode is increased by 23 % and 41 % at a high concentration of ethanol at pH 8.9, suggesting the stabilization role of graphene in enzyme loading. The study provides us a deep analysis on structures and performances of the bioanode incl. electrochemistry, X-ray photoelectron spectra, and atomic force microscopy images, which is significant to develop the new methods to construct 3D porous electrodes in energy conversion device. 相似文献
6.
Jingqiu Zhang Mingrui Jiang Zhuzhu Yue Zhicheng Wang Huinan Wang Mengyu Chen Xiaotong Wei Shuanghui Shi Menglin Wang Yingzi Wang 《Biomedical chromatography : BMC》2022,36(8):e5394
Previous pharmacological studies have indicated that diterpenoids are the primary effective chemical cluster in the seeds of Euphorbia lathyris L. The seed products are used in traditional Chinese medicine in the forms of Semen Euphorbiae (SE) and Semen Euphorbiae Pulveratum (SEP). However, the metabolism of the plant's diterpenoids has not been well elucidated, which means that the in vivo metabolite products have not been identified. The current study screened the physiological metabolites of six diterpenes [Euphorbia factor L1 (L1), L2 (L2), L3 (L3), L7a (L7a), L7b (L7b), and L8 (L8)] in feces and urine of rats after oral administration of SE and SEP using UHPLC-Q-Exactive MS. A total of 22 metabolites were detected in feces and 8 in urine, indicating that the major elimination route of diterpenoids is via the colon. Hydrolysis, methylation, and glucuronidation served as the primary metabolic pathways of these diterpenoids. In sum, this study contributed to the elucidation of new metabolites and metabolic pathways of SE and SEP, and the new chemical identities can be used to guide further pharmacokinetic studies. 相似文献
7.
Huo Guang-Hua Cui Chao-Yu He Tian Yan Jun-Qing Peng Wen-Wen 《Chemistry of Natural Compounds》2022,58(3):468-470
Chemistry of Natural Compounds - A new carotane sesquiterpenoid, methyl gymnabloate (1), was isolated from the fermentation broth of the wild macrofungus Gymnopus sp. 0612-9. Its structure was... 相似文献
8.
Reaction of 4,4′,4″-nitrilotribenzoic acid (H3L), a C3-symmetric ligand, with the divalent Co(II) salt Co(NO3)2·6H2O in the present of the N-donor ligand 1,2-di(4-pyridyl)ethylene (DPE) affords a new mixed-ligand coordination polymer with the chemical formula of [Co3(TNB)(DPE)2]·2H2O·DMF (1). In this study, CCK-8 assay was used to determine the effect of novel compound on proliferation of gastric cancer cells. The VEGF signaling pathway in gastric cancer cells was determined through employing real-time PCR after treatment of the above complex. Further, molecular docking simulation confirmed that the biological activity was coming from the carboxyl groups through the hydrogen bonding interactions with the receptor protein, the pyridine group only bonded with the Co ion for the formation of the Co complex. 相似文献
9.
10.
Liu Wenbin Huang Yiwei Huang Guolin Fan Lijiao Xie Yuming Shi Jeffery 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(5):2055-2068
Journal of Radioanalytical and Nuclear Chemistry - Eco-friendly and low-cost composite, amidoxime-functionalized microcrystalline cellulose/mesoporous silica (MCC/MS-AO), were synthesized by... 相似文献