全文获取类型
收费全文 | 16238篇 |
免费 | 1683篇 |
国内免费 | 2056篇 |
出版年
2024年 | 59篇 |
2023年 | 241篇 |
2022年 | 516篇 |
2021年 | 889篇 |
2020年 | 648篇 |
2019年 | 823篇 |
2018年 | 689篇 |
2017年 | 560篇 |
2016年 | 727篇 |
2015年 | 1072篇 |
2014年 | 1252篇 |
2013年 | 1299篇 |
2012年 | 1544篇 |
2011年 | 1415篇 |
2010年 | 898篇 |
2009年 | 811篇 |
2008年 | 929篇 |
2007年 | 828篇 |
2006年 | 751篇 |
2005年 | 669篇 |
2004年 | 594篇 |
2003年 | 615篇 |
2002年 | 527篇 |
2001年 | 301篇 |
2000年 | 247篇 |
1999年 | 197篇 |
1998年 | 126篇 |
1997年 | 107篇 |
1996年 | 96篇 |
1995年 | 65篇 |
1994年 | 98篇 |
1993年 | 54篇 |
1992年 | 55篇 |
1991年 | 39篇 |
1990年 | 41篇 |
1989年 | 33篇 |
1988年 | 30篇 |
1987年 | 22篇 |
1986年 | 18篇 |
1985年 | 32篇 |
1984年 | 13篇 |
1983年 | 15篇 |
1982年 | 15篇 |
1981年 | 3篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1973年 | 2篇 |
1971年 | 2篇 |
1961年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 897 毫秒
141.
Yawei Chen Jianming Li Zhanwu Lei Yakun Huo Lanlan Yang Suyuan Zeng Honghe Ding Yi Qin Yulin Jie Fanyang Huang Qi Li Junfa Zhu Ruiguo Cao Genqiang Zhang Shuhong Jiao Dongsheng Xu 《Liver Transplantation》2020,10(7)
Transition metal sulfides hold promising potentials as Li‐free conversion‐type cathode materials for high energy density lithium metal batteries. However, the practical deployment of these materials is hampered by their poor rate capability and short cycling life. In this work, the authors take the advantage of hollow structure of CuS nanoboxes to accommodate the volume expansion and facilitate the ion diffusion during discharge–charge processes. As a result, the hollow CuS nanoboxes achieve excellent rate performance (≈371 mAh g?1 at 20 C) and ultra‐long cycle life (>1000 cycles). The structure and valence evolution of the CuS nanobox cathode are identified by scanning electron microscopy, transmission electron microscopy, and X‐ray photoelectron spectroscopy. Furthermore, the lithium storage mechanism is revealed by galvanostatic intermittent titration technique and operando Raman spectroscopy for the initial charge–discharge process and the following reversible processes. These results suggest that the hollow CuS nanobox material is a promising candidate as a low‐cost Li‐free cathode material for high‐rate and long‐life lithium metal batteries. 相似文献
142.
Ligang Wang Xinxuan Duan Xijun Liu Jing Gu Rui Si Yi Qiu Yaming Qiu Dier Shi Fanhong Chen Xiaoming Sun Jianhua Lin Junliang Sun 《Liver Transplantation》2020,10(4)
Water splitting requires development of cost‐effective multifunctional materials that can catalyze both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) efficiently. Currently, the OER relies on the noble‐metal catalysts; since with other catalysts, its operation environment is greatly limited in alkaline conditions. Herein, an advanced water oxidation catalyst based on metallic Co9S8 decorated with single‐atomic Mo (0.99 wt%) is synthesized (Mo‐Co9S8@C). It exhibits pronounced water oxidization activity in acid, alkali, and neutral media by showing positive onset potentials of 200, 90, and 290 mV, respectively, which manifests the best Co9S8‐based single‐atom Mo catalyst till now. Moreover, it also demonstrates excellent HER performance over a wide pH range. Consequently, the catalyst even outperforms noble metal Pt/IrO2‐based catalysts for overall water splitting (only requiring 1.68 V in acid, and 1.56 V in alkaline). Impressively, it works under a current density of 10 mA cm?2 with no obvious decay during a 24 h (0.5 m H2SO4) and 72 h (1.0 m KOH) durability experiment. Density functional theory (DFT) simulations reveal that the synergistic effects of atomically dispersed Mo with Co‐containing substrates can efficiently alter the binding energies of adsorbed intermediate species and decrease the overpotentials of the water splitting. 相似文献
143.
The emodin anthraquinone derivatives are generally used in traditional Chinese medicine due to their various pharmacological activities. In the present study, a series of emodin anthraquinone derivatives have been designed and synthesized, among which 1,3‐dihydroxy‐6,8‐dimethoxyanthracene‐9,10‐dione is a natural compound that has been synthesized for the very first time, and 1,3‐dimethoxy‐5,8‐dimethylanthracene‐9,10‐dione is a compound that has never been reported earlier. Interestingly, while total seven of these compounds showed neuraminidase inhibitory activity in influenza virus with inhibition rate more than 50 %, specific four compounds exhibited significant inhibition of tumor cell proliferation. The further results demonstrate that 1,3‐dimethoxy‐5,8‐dimethylanthracene‐9,10‐dione showed the best anticancer activity among all the synthesized compounds by inducing highest apoptosis rate to HCT116 cancer cells and arresting their G0/G1 cell cycle phase, through elevation of intracellular level of reactive oxygen species (ROS). Moreover, the binding of 1,3‐dimethoxy‐5,8‐dimethylanthracene‐9,10‐dione with BSA protein has thoroughly been investigated. Altogether, this study suggests the neuraminidase inhibitory activity and antitumor potential of the new emodin anthraquinone derivatives. 相似文献
144.
A series of aryloxyethylamine derivatives were designed, synthesized and evaluated for their biological activity. Their structures were confirmed by 1H‐NMR, 13C‐NMR, FT‐IR and HR‐ESI‐MS. The preliminary screening of neuroprotection of compounds in vitro was detected by MTT, and the anti‐ischemic activity in vivo was tested using bilateral common carotid artery occlusion in mice. Most of these compounds showed potential neuroprotective effects against the glutamate‐induced cell death in differentiated rat pheochromocytoma cells (PC12 cells), especially for (4‐fluorophenyl){1‐[2‐(4‐methoxyphenoxy)ethyl]piperidin‐4‐yl}methanone, {1‐[2‐(4‐methoxyphenoxy)ethyl]piperidin‐4‐yl}(4‐methoxyphenyl)methanone, (4‐bromophenyl){1‐[2‐(4‐methoxyphenoxy)ethyl]piperidin‐4‐yl}methanone, {1‐[2‐(4‐chlorophenoxy)ethyl]piperidin‐4‐yl}(4‐chlorophenyl)methanone, (4‐chlorophenyl)(1‐{2‐[(naphthalen‐2‐yl)oxy]ethyl}piperidin‐4‐yl)methanone, (4‐chlorophenyl){1‐[2‐(4‐methoxyphenoxy)ethyl]piperidin‐4‐yl}methanone and {1‐[2‐(4‐bromophenoxy)ethyl]piperidin‐4‐yl}(4‐chlorophenyl)methanone, which exhibited potent protection of PC12 cells at three doses (0.1, 1.0, 10 μM). Compounds (4‐fluorophenyl){1‐[2‐(4‐methoxyphenoxy)ethyl]piperidin‐4‐yl}methanone, (4‐fluorophenyl){1‐[2‐(naphthalen‐2‐yloxy)ethyl]piperidin‐4‐yl}methanone, {1‐[2‐(4‐methoxyphenoxy)ethyl]piperidin‐4‐yl}(4‐methoxyphenyl)methanone and {1‐[2‐(4‐chlorophenoxy)ethyl]piperidin‐4‐yl}(4‐chlorophenyl)methanone possessed the significant prolongation of the survival time of mice subjected to acute cerebral ischemia and decreased the mortality rate at all five doses tested (200, 100, 50, 25, 12.5 mg/kg) and had significant neuroprotective activity. In addition, (4‐fluorophenyl){1‐[2‐(4‐methoxyphenoxy)ethyl]piperidin‐4‐yl}methanone, {1‐[2‐(4‐methoxyphenoxy)ethyl]piperidin‐4‐yl}(4‐methoxyphenyl)methanone and {1‐[2‐(4‐chlorophenoxy)ethyl]piperidin‐4‐yl}(4‐chlorophenyl)methanone possessed outstanding neuroprotection in vitro and in vivo. These compounds can be used as a promising neuroprotective agents for future development of new anti‐ischemic stroke agents. Basic structure–activity relationships are also presented. 相似文献
145.
Chen Lu Zhongti Sun Lianghao Yu Xueyu Lian Yuyang Yi Jie Li Zhongfan Liu Shixue Dou Jingyu Sun 《Liver Transplantation》2020,10(28)
Carbonaceous materials have emerged as promising anode candidates for potassium‐ion batteries (PIBs) due to overwhelming advantages including cost‐effectiveness and wide availability of materials. However, further development in this realm is handicapped by the deficiency in their in‐target and large‐scale synthesis, as well as their low specific capacity and huge volume expansion. Herein the precise and scalable synthesis of N/S dual‐doped graphitic hollow architectures (NSG) via direct plasma enhanced chemical vapor deposition is reported. Thus‐fabricated NSG affording uniform nitrogen/sulfur co‐doping, possesses ample potassiophilic surface moieties, effective electron/ion‐transport pathways, and high structural stability, which bestow it with high rate capability (≈100 mAh g?1 at 20 A g?1) and a prolonged cycle life (a capacity retention rate of 90.2% at 5 A g?1 after 5000 cycles), important steps toward high‐performance K‐ion storage. The enhanced kinetics of the NSG anode are systematically probed by theoretical simulations combined with operando Raman spectroscopy, ex situ X‐ray photoelectron spectroscopy, and galvanostatic intermittent titration technique measurements. In further contexts, printed NSG electrodes with tunable mass loading (1.84, 3.64, and 5.65 mg cm?2) are realized to showcase high areal capacities. This study demonstrates the construction of a printable carbon‐based PIB anode, that holds great promise for next‐generation grid‐scale PIB applications. 相似文献
146.
Jin Zhao Yi‐Zhou Zhang Jianyu Chen Wenli Zhang Du Yuan Rodney Chua Husam N. Alshareef Yanwen Ma 《Liver Transplantation》2020,10(18)
The pursuit of more efficient carbon‐based anodes for sodium‐ion batteries (SIBs) prepared from facile and economical methods is a very important endeavor. Based on the crystallinity difference within carbon materials, herein, a low‐temperature selective burning method is developed for preparing oxygen and nitrogen codoped holey graphene aerogel as additive‐free anode for SIBs. By selective burning of a mixture of graphene and low‐crystallinity carbon at 450 °C in air, an elastic porous graphene monolith with abundant holes on graphene sheets and optimized crystallinity is obtained. These structural characteristics lead to an additive‐free electrode with fast charge (ions and electrons) transfer and more abundant Na+ storage active sites. Moreover, the heteroatom oxygen/nitrogen doping favors large interlayer distance for rapid Na+ insertion/extraction and provides more active sites for high capacitive contribution. The optimized sample exhibits superior sodium‐ion storage capability, i.e., high specific capacity (446 mAh g?1 at 0.1 A g?1), ultrahigh rate capability (189 mAh g?1 at 10 A g?1), and long cycle life (81.0% capacity retention after 2000 cycles at 5 A g?1). This facile and economic strategy might be extended to fabricating other superior carbon‐based energy storage materials. 相似文献
147.
148.
Yinglin Xiao Bing Han Yi Zeng Shang‐Sen Chi Xianzhe Zeng Zijian Zheng Kang Xu Yonghong Deng 《Liver Transplantation》2020,10(14)
Lithium–sulfur batteries (LSBs) are considered promising candidates for the next‐generation energy‐storage systems due to their high theoretical capacity and prevalent abundance of sulfur. Their reversible operation, however, encounters challenges from both the anode, where dendritic and dead Li‐metal form, and the cathode, where polysulfides dissolve and become parasitic shuttles. Both issues arise from the imperfection of interphases between electrolyte and electrode. Herein, a new lithium salt based on an imide anion with fluorination and unsaturation in its structure is reported, whose interphasial chemistries resolve these issues simultaneously. Lithium 1, 1, 2, 2, 3, 3‐hexafluoropropane‐1, 3‐disulfonimide (LiHFDF) forms highly fluorinated interphases at both anode and cathode surfaces, which effectively suppress formation of Li‐dendrites and dissolution/shuttling of polysulfides, and significantly improves the electrochemical reversibility of LSBs. In a broader context, this new Li salt offers a new perspective for diversified beyond Li‐ion chemistries that rely on a Li‐metal anode and active cathode materials. 相似文献
149.
Sun Weifeng Wu Yuanming Ding Wenwu Wang Li Wu Lunjie Lin Lu Che Zhenming Zhu Longbao Liu Yi Chen Xiaohua 《Bioprocess and biosystems engineering》2020,43(4):701-710
Bioprocess and Biosystems Engineering - Currently, some cases about the expression of flavor peptides with microorganisms were reported owing to the obvious advantages of biological expression over... 相似文献
150.
Zhan Yijing Zhu Ping Liang Jinfeng Xu Zheng Feng Xiaohai Liu Yi Xu Hong Li Sha 《Bioprocess and biosystems engineering》2020,43(1):75-84
Bioprocess and Biosystems Engineering - A safe, efficient, environmentally friendly process for producing isomaltulose is needed. Here, the biocatalyst, sucrose isomerase (SIase) from Erwinia... 相似文献