全文获取类型
收费全文 | 87032篇 |
免费 | 11173篇 |
国内免费 | 8158篇 |
专业分类
化学 | 60554篇 |
晶体学 | 805篇 |
力学 | 4986篇 |
综合类 | 526篇 |
数学 | 10686篇 |
物理学 | 28806篇 |
出版年
2024年 | 239篇 |
2023年 | 1527篇 |
2022年 | 2647篇 |
2021年 | 2786篇 |
2020年 | 2805篇 |
2019年 | 2752篇 |
2018年 | 2455篇 |
2017年 | 2212篇 |
2016年 | 3579篇 |
2015年 | 3591篇 |
2014年 | 4231篇 |
2013年 | 6096篇 |
2012年 | 7236篇 |
2011年 | 7488篇 |
2010年 | 4922篇 |
2009年 | 5079篇 |
2008年 | 5248篇 |
2007年 | 4818篇 |
2006年 | 4443篇 |
2005年 | 4002篇 |
2004年 | 3654篇 |
2003年 | 2724篇 |
2002年 | 2441篇 |
2001年 | 1898篇 |
2000年 | 1730篇 |
1999年 | 1797篇 |
1998年 | 1537篇 |
1997年 | 1349篇 |
1996年 | 1418篇 |
1995年 | 1233篇 |
1994年 | 1126篇 |
1993年 | 1007篇 |
1992年 | 886篇 |
1991年 | 743篇 |
1990年 | 637篇 |
1989年 | 547篇 |
1988年 | 432篇 |
1987年 | 406篇 |
1986年 | 362篇 |
1985年 | 390篇 |
1984年 | 293篇 |
1983年 | 243篇 |
1982年 | 203篇 |
1981年 | 171篇 |
1980年 | 134篇 |
1979年 | 81篇 |
1978年 | 84篇 |
1977年 | 87篇 |
1975年 | 81篇 |
1974年 | 76篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
Dr. Wan‐Ling Liu Ni‐Shin Yang Ya‐Ting Chen Stephen Lirio Cheng‐You Wu Prof. Chia‐Her Lin Prof. Hsi‐Ya Huang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(1):115-119
A green and sustainable strategy synthesizes clinical medicine warfarin anticoagulant by using lipase‐supported metal–organic framework (MOF) bioreactors (see scheme). These findings may be beneficial for future studies in the industrial production of chemical, pharmaceutical, and agrochemical precursors. 相似文献
73.
74.
Sha Xia Dan Wang Nian-Ke Chen Dong Han Xian-Bin Li Hong-Bo Sun 《Annalen der Physik》2020,532(3):1900318
Defects play a central role in controlling the electronic properties of two-dimensional (2D) materials and realizing the industrialization of 2D electronics. However, the evaluation of charged defects in 2D materials within first-principles calculation is very challenging and has triggered a recent development of the WLZ (Wang, Li, Zhang) extrapolation method. This method lays the foundation of the theoretical evaluation of energies of charged defects in 2D materials within the first-principles framework. Herein, the vital role of defects for advancing 2D electronics is discussed, followed by an introduction of the fundamentals of the WLZ extrapolation method. The ionization energies (IEs) obtained by this method for defects in various 2D semiconductors are then reviewed and summarized. Finally, the unique defect physics in 2D dimensions including the dielectric environment effects, defect ionization process, and carrier transport mechanism captured with the WLZ extrapolation method are presented. As an efficient and reasonable evaluation of charged defects in 2D materials for nanoelectronics and other emerging applications, this work can be of benefit to the community. 相似文献
75.
Aequationes mathematicae - We discuss equivalence conditions for the non-existence of non-trivial meromorphic solutions to the Fermat Diophantine equation $$f^m(z)+g^n(z)=1$$ with integers $$m,n\ge... 相似文献
76.
77.
78.
He Haidong Yang Haifeng Zhou Longpeng Chen Tianchi 《Journal of Russian Laser Research》2015,36(3):292-299
Ni–Co alloys have a wide range of applications in various fields owning to their excellent physical, chemical, and mechanical properties. In this paper, we prepare Ni–Co alloy coatings on 316L stain steel surfaces by electroplating. We present a novel approach utilizing a nanosecond laser to induce microtextures on Ni–Co alloy coatings. We study experimentally the effects of laser power and scanning rate on the surface morphologies of Ni–Co alloy coatings. The results indicate that the shape and size of induced microtextures can be controlled by the laser power and scanning rate. The size of grains increases with increase in the work current of the laser (WCL) at a certain scanning rate. With the WCL constant, the size of grains decreases with increase in scanning rate while their average height increases. It is a simple and easily-controlled method for the fabrication of microstructures on Ni–Co alloy coatings, which has promising applications in investigations of the properties of microtextured surfaces, such as friction, adhesion, and wetting. 相似文献
79.
Metabolic profiles of dioscin in rats revealed by ultra‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometry
下载免费PDF全文
![点击此处可从《Biomedical chromatography : BMC》网站下载免费的PDF全文](/ch/ext_images/free.gif)
He Zhu Jin‐Di Xu Qian Mao Hong Shen Ming Kong Jian‐Ping Chen Song‐Lin Li 《Biomedical chromatography : BMC》2015,29(9):1415-1421
Dioscin (DIS), one of the most abundant bioactive steroidal saponins in Dioscorea sp., is used as a complementary medicine to treat coronary disease and angina pectoris in China. Although the pharmacological activities and pharmacokinetics of DIS have been well demonstrated, information regarding the final metabolic fates is very limited. This study investigated the in vivo metabolic profiles of DIS after oral administration by ultra‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometry method. The structures of the metabolites were identified and tentatively characterized by means of comparing the molecular mass, retention time and fragmentation pattern of the analytes with those of the parent compound. A total of eight metabolites, including seven phase I and one phase II metabolites, were detected and tentatively identified for the first time. Oxidation, deglycosylation and glucuronidation were found to be the major metabolic processes of the compound in rats. In addition, a possible metabolic pathway on the biotransformation of DIS in vivo was proposed. This study provides valuable and new information on the metabolism of DIS, which will be helpful for further understanding its mechanism of action. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
80.
Mariusz Marć Marek Tobiszewski Bożena Zabiegała Miguel de la Guardia Jacek Namieśnik 《Analytica chimica acta》2015
This review summarizes the different tools and concepts that are commonly applied in air quality monitoring. The monitoring of atmosphere is extremely important as the air quality is an important problem for large communities. Main requirements for analytical devices used for monitoring include a long period of autonomic operation and portability. These instruments, however, are often characterized by poor analytical performance. Monitoring networks are the most common tools used for monitoring, so large-scale monitoring programmes are summarized here. Biomonitoring, as a cheap and convenient alternative to traditional sample collection, is becoming more and more popular, although its main drawback is the lack of standard procedures. Telemonitoring is another approach to air monitoring, which offers some interesting opportunities, such as ease of coverage of large or remote areas, constituting a complementary approach to traditional strategies; however, it requires huge costs. 相似文献