全文获取类型
收费全文 | 6026篇 |
免费 | 384篇 |
国内免费 | 118篇 |
出版年
2023年 | 48篇 |
2022年 | 62篇 |
2021年 | 78篇 |
2020年 | 130篇 |
2019年 | 182篇 |
2018年 | 204篇 |
2017年 | 135篇 |
2016年 | 122篇 |
2015年 | 114篇 |
2014年 | 265篇 |
2013年 | 299篇 |
2012年 | 202篇 |
2011年 | 209篇 |
2010年 | 132篇 |
2009年 | 166篇 |
2008年 | 216篇 |
2007年 | 263篇 |
2006年 | 208篇 |
2005年 | 202篇 |
2004年 | 128篇 |
2003年 | 144篇 |
2002年 | 113篇 |
2001年 | 83篇 |
2000年 | 70篇 |
1999年 | 73篇 |
1998年 | 80篇 |
1997年 | 70篇 |
1996年 | 54篇 |
1995年 | 52篇 |
1994年 | 57篇 |
1993年 | 66篇 |
1992年 | 63篇 |
1991年 | 43篇 |
1990年 | 50篇 |
1989年 | 60篇 |
1988年 | 46篇 |
1987年 | 46篇 |
1986年 | 44篇 |
1985年 | 144篇 |
1984年 | 283篇 |
1983年 | 223篇 |
1982年 | 274篇 |
1981年 | 254篇 |
1980年 | 171篇 |
1979年 | 169篇 |
1978年 | 134篇 |
1977年 | 108篇 |
1976年 | 64篇 |
1975年 | 42篇 |
1974年 | 34篇 |
排序方式: 共有6528条查询结果,搜索用时 15 毫秒
951.
Harihara Padhy Yingqian Chen Johann Lüder Satyanarayana Reddy Gajella Sergei Manzhos Palani Balaya 《Liver Transplantation》2018,8(7)
A combined experimental and computational study of disodium pyridine‐2,5‐dicarboxylate (Na2PDC) is presented exploring the possibility of using it as a potential anode for organic sodium‐ion batteries. This electrode material can reversibly insert/release two Na cations per formula unit, resulting in high reversible capacity of 270 mA h g?1 (236 mA h g?1 after accounting for the contribution from Super P carbon) with excellent cyclability 225 mA h g?1, with retention of 83% capacity after 100 cycles, and good rate performance with reversible capacity of 138 mA h g?1 at a 5 C rate. The performance of disodium pyridine dicarboxylate is therefore found to be superior to that of the related and well investigated disodium terephthalate. The material shows two voltage plateaus at about 0.6 V up to Na2+1PDC and then 0.4 V up to full sodiation, Na2+2PDC. The first plateau is attributed to the coordination of inserted Na to nitrogen atoms with bond formation, i.e., a different mechanism from the terephthalate analog. The subsequent plateau is due to coordination to the carboxylic groups. 相似文献
952.
Ying‐Ying Wang Bao‐Hua Hou Jin‐Zhi Guo Qiu‐Li Ning Wei‐Lin Pang Jiawei Wang Chang‐Li Lü Xing‐Long Wu 《Liver Transplantation》2018,8(18)
Presently, commercialization of sodium‐ion batteries (SIBs) is still hindered by the relatively poor energy‐storage performance. In addition, low‐temperature (low‐T) Na storage is another principal concern for the wide application of SIBs. Unfortunately, the Na‐transfer kinetics is extremely sluggish at low‐T, as a result, there are few reports on low‐T SIBs. Here, an advanced low‐T sodium‐ion full battery (SIFB) assembled by an anode of 3D Se/graphene composite and a high‐voltage cathode (Na3V2(PO4)2O2F) is developed, exhibiting ultralong lifespan (over even 15 000 cycles, the capacity retention is still up to 86.3% at 1 A g?1), outstanding low‐T energy storage performance (e.g., all values of capacity retention are >75% after 1000 cycles at temperatures from 25 to ?25 °C at 0.4 A g?1), and high‐energy/power properties. Such ultralong lifespan signifies that the developed sodium‐ion full battery can be used for longer than 60 years, if batteries charge/discharge once a day and 80% capacity retention is the standard of battery life. As a result, the present study not only promotes the practicability and commercialization of SIBs but also points out the new developing directions of next‐generation energy storage for wider range applications. 相似文献
953.
CuS Microspheres with Tunable Interlayer Space and Micropore as a High‐Rate and Long‐Life Anode for Sodium‐Ion Batteries 下载免费PDF全文
Yuanhua Xiao Dangcheng Su Xuezhao Wang Shide Wu Liming Zhou Ying Shi Shaoming Fang Hui‐Ming Cheng Feng Li 《Liver Transplantation》2018,8(22)
Layered transition metal sulfides (LTMSs) have tremendous commercial potential in anode materials for sodium‐ion batteries (SIBs) in large‐scale energy storage application. However, it is a great challenge for most LTMS electrodes to have long cycling life and high‐rate capability due to their larger volume expansion and the formation of soluble polysulfide intermediates caused by the conversion reaction. Herein, layered CuS microspheres with tunable interlayer space and pore volumes are reported through a cost‐effective interaction method using a cationic surfactant of cetyltrimethyl ammonium bromide (CTAB). The CuS–CTAB microsphere as an anode for SIBs reveals a high reversible capacity of 684.6 mAh g?1 at 0.1 A g?1, and 312.5 mAh g?1 at 10 A g?1 after 1000 cycles with high capacity retention of 90.6%. The excellent electrochemical performance is attributed to the unique structure of this material, and a high pseudocapacitive contribution ensures its high‐rate performance. Moreover, in situ X‐ray diffraction is applied to investigate their sodium storage mechanism. It is found that the long chain CTAB in the CuS provides buffer space, traps polysulfides, and restrains the further growth of Cu particles during the conversion reaction process that ensure the long cycling stability and high reversibility of the electrode material. 相似文献
954.
A Novel Graphene Oxide Wrapped Na2Fe2(SO4)3/C Cathode Composite for Long Life and High Energy Density Sodium‐Ion Batteries 下载免费PDF全文
Mingzhe Chen David Cortie Zhe Hu Huile Jin Shun Wang Qinfen Gu Weibo Hua Enhui Wang Weihong Lai Lingna Chen Shu‐Lei Chou Xiao‐Lin Wang Shi‐Xue Dou 《Liver Transplantation》2018,8(27)
The cathode materials in the Na‐ion battery system are always the key issue obstructing wider application because of their relatively low specific capacity and low energy density. A graphene oxide (GO) wrapped composite, Na2Fe2(SO4)3@C@GO, is fabricated via a simple freeze‐drying method. The as‐prepared material can deliver a 3.8 V platform with discharge capacity of 107.9 mAh g?1 at 0.1 C (1 C = 120 mA g?1) as well as offering capacity retention above 90% at a discharge rate of 0.2 C after 300 cycles. The well‐constructed carbon network provides fast electron transfer rates, and thus, higher power density also can be achieved (75.1 mAh g?1 at 10 C). The interface contribution of GO and Na2Fe2(SO4)3 is recognized and studied via density function theory calculation. The Na storage mechanism is also investigated through in situ synchrotron X‐ray diffraction, and pseudocapacitance contributions are also demonstrated. The diffusion coefficient of Na+ ions is around 10?12–10?10.8 cm2 s?1 during cycling. The higher working voltage of this composite is mainly ascribed to the larger electronegativity of the element S. The research indicates that this well‐constructed composite would be a competitive candidate as a cathode material for Na‐ion batteries. 相似文献
955.
Xun Guo Guozhao Fang Wenyu Zhang Jiang Zhou Lutong Shan Liangbing Wang Chao Wang Tianquan Lin Yan Tang Shuquan Liang 《Liver Transplantation》2018,8(27)
Rechargeable aqueous zinc‐ion batteries (ZIBs) with high safety and low‐cost are highly desirable for grid‐scale energy storage, yet the energy storage mechanisms in the current cathode materials are still complicated and unclear. Hence, several sodium vanadates with NaV3O8‐type layered structure (e.g., Na5V12O32 and HNaV6O16·4H2O) and β‐Na0.33V2O5‐type tunneled structure (e.g., Na0.76V6O15) are constructed and the storage/release behaviors of Zn2+ ions are deeply investigated in these two typical structures. It should be mentioned that the 2D layered Na5V12O32 and HNaV6O16·4H2O with more effective path for Zn2+ diffusion exhibit higher ion diffusion coefficients than that of tunneled Na0.76V6O15. As a result, Na5V12O32 delivers higher capacity than that of Na0.76V6O15, and a long‐term cyclic performance up to 2000 cycles at 4.0 A g?1 in spite of its capacity fading. This work provides a new perspective of Zn2+ storage mechanism in aqueous ZIB systems. 相似文献
956.
Jun Zhang Da‐Wei Wang Wei Lv Lei Qin Shuzhang Niu Siwei Zhang Tengfei Cao Feiyu Kang Quan‐Hong Yang 《Liver Transplantation》2018,8(26)
Sodium‐ion batteries (SIBs) have the potential to be practically applied in large‐scale energy storage markets. The rapid progress of SIBs research is primarily focused on electrodes, while electrolytes attract less attention. Indeed, the improvement of electrode performance is arguably correlated with the electrolyte optimization. In conventional lithium‐ion batteries (LIBs), ether‐based electrolytes are historically less practical owing to the insufficient passivation of both anodes and cathodes. As an important class of aprotic electrolytes, ethers have revived with the emerging lithium‐sulfur and lithium‐oxygen batteries in recent years, and are even booming in the wave of SIBs. Ether‐based electrolytes are unique to enabling these new battery chemistries in terms of producing stable ternary graphite intercalation compounds, modifying anode solid electrolyte interphases, reducing the solubility of intermediates, and decreasing polarization. Better still, ether‐based electrolytes are compatible with specific inorganic cathodes and could catalyze the assembly of full SIBs prototypes. This Research News article aims to summarize the recent critical reports on ether‐based electrolytes in sodium‐based batteries, to unveil the uniqueness of ether‐based electrolytes to advancing diverse electrode materials, and to shed light on the viability and challenges of ether‐based electrolytes in future sodium‐based battery chemistries. 相似文献
957.
958.
Sodium Acetate,Sodium Acid Pyrophosphate,and Citric Acid Impacts on Isolated Peripheral Lymphocyte Viability,Proliferation, and DNA Damage 下载免费PDF全文
Yasmina M. Abd‐Elhakim Abeer Anwar Mohamed M. Hashem Gihan G. Moustafa Khaled Abo‐El‐Sooud 《Journal of biochemical and molecular toxicology》2018,32(8)
The present study examined the impacts of sodium acetate (SA), sodium acid pyrophosphate (SAPP), and citric acid (CA) on the viability, proliferation, and DNA damage of isolated lymphocytes in vitro. 3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide (MTT) and lactate dehydrogenase (LDH) release assays were adopted to evaluate cell viability, while comet assay was employed to assess the genotoxic effects. The cells were incubated with different levels of SA (50, 100, and 200 mM), SAPP (25, 50, and 100 mM/L), or CA (100, 200, and 300 μg/mL). The lymphocytes treated with the tested food additives showed concentration‐dependent decreases in both cell viability and proliferation. A concentration‐dependent increase in LDH release was also observed. The comet assay results indicated that SA, SAPP, and CA increased DNA damage percentage, tail DNA percentage, tail length, and tail moment in a concentration‐dependent manner. The current results showed that SA, SAPP, and CA are cytotoxic and genotoxic to isolated lymphocytes in vitro. 相似文献
959.
目的:探索孟鲁司特钠联合布地奈德混悬液对哮喘急性发作患儿血清嗜酸性粒细胞(EOS)、嗜酸性粒细胞阳离子蛋白(ECP)水平和肺功能的影响。方法:选择自2015年10月至2016年10月我院收治的200例支气管哮喘急性发作患儿,按照随机数表法分成观察组和对照组各100例。对照组患儿口服孟鲁司特钠,观察组患儿在对照组基础上给予布地奈德气雾剂进行雾化治疗,两组均治疗1周。统计分析两组患儿的临床有效率,肺功能指标,包括第1秒用力呼气容积(FEV1)、用力肺活量(FVC)及FEV1/FVC,对比治疗前后两组患儿血清中EOS、ECP水平的变化。结果:治疗后,观察组的总有效率为97.00%,显著高于对照组的81.00%(P0.05);经治疗后两组患儿肺功能指标均较治疗前明显改善,且观察组患儿优于对照组(P0.05);两组患儿治疗后EOS、ECP水平均低于治疗前,而观察组患儿低于对照组,差异均有统计学意义(P0.05)。结论:孟鲁司特钠联合布地奈德对于小儿哮喘的急性发作具有良好的临床疗效,能显著改善患儿肺功能和血清中炎症因子的水平,减轻患儿体内的炎症反应,值得在临床上推广应用。 相似文献
960.
Sodium bicarbonate‐gelled chitosan beads as mechanically stable carriers for the covalent immobilization of enzymes 下载免费PDF全文
Marwa I. Wahba 《Biotechnology progress》2018,34(2):347-361
The poor mechanical stability of chitosan has long impeded its industrial utilization as an immobilization carrier. In this study, the mechanical properties of chitosan beads were greatly improved through utilizing the slow rate of the sodium bicarbonate‐induced chitosan gelation and combining it with the chemical cross‐linking action of glutaraldehyde (GA). The GA‐treated sodium bicarbonate‐gelled chitosan beads exhibited much better mechanical properties and up to 2.45‐fold higher observed activity of the immobilized enzyme (β‐D‐galactosidase (β‐gal)) when compared to the GA‐treated sodium tripolyphosphate (TPP)‐gelled chitosan beads. The differences between the sodium bicarbonate‐gelled and the TPP‐gelled chitosan beads were proven visually and also via scanning electron microscopy, elemental analysis, and differential scanning calorimetry. Moreover, the optimum pH, the optimum temperature, the apparent Km, and the apparent Vmax of the β‐gals immobilized onto the two aforementioned types of chitosan beads were determined and compared. A reusability study was also performed. This study proved the superiority of the sodium bicarbonate‐gelled chitosan beads as they retained 72.22 ± 4.57% of their initial observed activity during the 13th reusability cycle whereas the TPP‐gelled beads lost their activity during the first four reusability cycles, owing to their fragmentation. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:347–361, 2018 相似文献