全文获取类型
收费全文 | 418797篇 |
免费 | 61676篇 |
国内免费 | 48651篇 |
专业分类
化学 | 186242篇 |
晶体学 | 3314篇 |
力学 | 18624篇 |
综合类 | 1448篇 |
数学 | 36751篇 |
物理学 | 121740篇 |
综合类 | 161005篇 |
出版年
2024年 | 1626篇 |
2023年 | 5760篇 |
2022年 | 9474篇 |
2021年 | 10378篇 |
2020年 | 10909篇 |
2019年 | 12692篇 |
2018年 | 12355篇 |
2017年 | 12679篇 |
2016年 | 16409篇 |
2015年 | 17477篇 |
2014年 | 21107篇 |
2013年 | 25708篇 |
2012年 | 28215篇 |
2011年 | 30170篇 |
2010年 | 27730篇 |
2009年 | 27287篇 |
2008年 | 22490篇 |
2007年 | 20901篇 |
2006年 | 18576篇 |
2005年 | 17274篇 |
2004年 | 15074篇 |
2003年 | 12283篇 |
2002年 | 11501篇 |
2001年 | 10954篇 |
2000年 | 9462篇 |
1999年 | 12441篇 |
1998年 | 10776篇 |
1997年 | 10462篇 |
1996年 | 10452篇 |
1995年 | 9663篇 |
1994年 | 9274篇 |
1993年 | 8266篇 |
1992年 | 7227篇 |
1991年 | 6497篇 |
1990年 | 5439篇 |
1989年 | 5021篇 |
1988年 | 4442篇 |
1987年 | 2965篇 |
1986年 | 2569篇 |
1985年 | 1708篇 |
1984年 | 1495篇 |
1983年 | 712篇 |
1982年 | 1176篇 |
1981年 | 939篇 |
1980年 | 918篇 |
1979年 | 610篇 |
1978年 | 593篇 |
1977年 | 700篇 |
1976年 | 1122篇 |
1972年 | 571篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
32.
Reza Kordnezhadian Bing-Yu Li Armir Zogu Dr. Joachim Demaerel Prof. Dr. Wim M. De Borggraeve Dr. Ermal Ismalaj 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(60):e202201491
Pentafluorosulfanyl (SF5)-containing compounds and corresponding analogs are a highly valuable class of fluorine-containing building blocks owing to their unique properties. The reason for that is the set of peculiar and tremendously beneficial characteristics they can impart on molecules once introduced onto them. Despite this, their application in distinct scientific fields remains modest, given the extremely harsh reaction conditions needed to access such compounds. The recent synthetic approaches via S−F, and C−SF5 bond formation as well as the use of SF5-containing building blocks embody a “stairway-to-heaven” loophole in the synthesis of otherwise-inaccessible chemical scaffolds only a few years ago. Herein, we report and evaluate the properties of the SF5 group and analogs, by summarizing synthetic methodologies available to access them as well as following applications in material science and medicinal chemistry since 2015. 相似文献
33.
进入新发展阶段后,科技创新创业活动对孵化服务提出了更高的要求,科技创业载体需要加快提升专业化、精准化服务能力.文章基于2016-2019年全国科技创业孵化载体发展数据,全面分析专业化科技创业孵化载体建设发展现状,剖析了科技创业孵化载体在专业化建设方面存在的方向不清、动力不足、能力不够、模式不明、机制不畅等问题,从建立评价指标体系、明确建设主体、提升服务能力、加强资源开放和政策供给等方面提出对策建议. 相似文献
34.
Journal of Optimization Theory and Applications - We distinguish two kinds of piecewise linear functions and provide an interesting representation for a piecewise linear function between two normed... 相似文献
35.
Li Y. Shi W. H. Dong L. M. Xu S. X. Huang H. J. Yin J. R. 《Journal of Applied Spectroscopy》2022,89(3):534-541
Journal of Applied Spectroscopy - Sr3B2O6:Dy3+, Eu3+ single-matrix white-light-emitting materials are prepared using the high-temperature solid-state method. The microstructure, emission spectrum,... 相似文献
36.
Dr. Ruijuan Yao Prof. Di Liu Dr. Huihui Wan Dr. Yongqiang Mei Jiahui Wang Dr. Rui Cai Dr. Huimin Zhang Dr. Yuzhen Zhao Dr. Zemin He 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(71):e202202269
By linking the carbazole unit to the nitrogen atom of acridone through phenyl or pyridyl, two compounds, named 10-(4-(9H-carbazol-9-yl)phenyl)acridin-9(10H)-one (AC-Ph-Cz) and 10-(5-(9H-carbazol-9-yl)pyridin-2-yl)acridin-9(10H)-one (AC-Py-Cz) were designed and synthesized. These two materials, characterized with highly twisted and rigid structure, good thermal stability, and balanced carrier-transporting properties, were employed as host materials for green phosphorescent and thermally activated delayed fluorescent organic light-emitting diodes (OLEDs). The carbazole group, despite its small contribution to the highest occupied molecular orbitals (HOMOs) of these two materials, plays an essential role as an intramolecular host in energy delivering and improving the hole transporting ability of these two hosts. The incorporation of the electron-deficient pyridyl group as a linking group slightly improves the electron transporting capability of AC-Py-Cz. The green phosphorescent OLED (PhOLED) based on AC-Py-Cz exhibited excellent device performance with a turn-on voltage of 2.5 V, a maximum power efficiency and an external quantum efficiency (ηext) of 89.8 lm W−1 and 25.2 %, respectively, benefitting from the better charge-balancing ability of AC-Py-Cz host due to the presence of the pyridyl bridge. More importantly, all the devices based on these two hosts showed low efficiency roll-off at high brightness due to the suppressed non-radiative transition in the emitting layer. In particular, the AC-Py-Cz-hosted green PhOLED exhibited an efficiency roll-off of 1.6 % from the maximum next at a high brightness of 1000 cd m−2 and a roll-off of 15.9 % at an extremely high brightness of 10000 cd m−2. This study manifests that acridone-based host materials have great potential in fabricating OLEDs with low efficiency roll-off. 相似文献
37.
Yi-Tong Xu Tian-Yang Zhang Zheng Li Xiang-Nan Liu Yuan-Cheng Zhu Wei-Wei Zhao Hong-Yuan Chen Jing-Juan Xu 《Electroanalysis》2022,34(6):947-955
Photoelectrochemical (PEC) cytosensors, a combination of the PEC process and the living-cell assay, have emerged as a powerful tool in the analytical and biological science. This mini review provides a brief introduction of this arena and summaries the key steps about the development of PEC cytosensors with representative examples, followed by future prospects based on our own opinions. 相似文献
38.
Li Quanxin Li Zheng He Cheng Sun Huilin Tan Shengheng Zhang Hua 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(5):2105-2115
Journal of Radioanalytical and Nuclear Chemistry - The simplified 8-oxide system (SiO2-B2O3-Na2O-Al2O3-CaO-TiO2-MoO3-La2O3) has been prepared under two types of cooling methods, and analyzed with... 相似文献
39.
Hongjin Wang Tengfei Long Hao Zhang Meng Li Qi Sun Xin Zhai Lixin Sun 《Biomedical chromatography : BMC》2022,36(4):e5301
3,4-Difluorobenzyl(1-ethyl-5-(4-((4-hydroxypiperidin-1-yl)-methyl)thiazol-2-yl)-1H-indol-3-yl)carbamate (NAI59), a small molecule with outstanding therapeutic effectiveness to anti-pulmonary fibrosis, was developed as an autotaxin inhibitor candidate compound. To evaluate the pharmacokinetics and plasma protein binding of NAI59, a UPLC–MS/MS method was developed to quantify NAI59 in plasma and phosphate-buffered saline. The calibration curve linearity ranged from 9.95 to 1990.00 ng/mL in plasma. The accuracy was −6.8 to 5.9%, and the intra- and inter-day precision was within 15%. The matrix effect and recovery, as well as dilution integrity, were within the criteria. The chromatographic and mass spectrometric conditions were also feasible to determine phosphate-buffered saline samples, and it has been proved that this method exhibits good precision and accuracy in the range of 9.95–497.50 ng/mL in phosphate-buffered saline. This study is the first to determine the pharmacokinetics, absolute bioavailability, and plasma protein binding of NAI59 in rats using this established method. Therefore, the pharmacokinetic profiles of NAI59 showed a dose-dependent relationship after oral administration, and the absolute bioavailability in rats was 6.3%. In addition, the results of protein binding showed that the combining capacity of NAI59 with plasma protein attained 90% and increased with the increase in drug concentration. 相似文献
40.