全文获取类型
收费全文 | 219962篇 |
免费 | 20244篇 |
国内免费 | 15476篇 |
专业分类
耳鼻咽喉 | 1903篇 |
儿科学 | 2191篇 |
妇产科学 | 2979篇 |
基础医学 | 26571篇 |
口腔科学 | 3684篇 |
临床医学 | 30824篇 |
内科学 | 32940篇 |
皮肤病学 | 2227篇 |
神经病学 | 12394篇 |
特种医学 | 8223篇 |
外国民族医学 | 138篇 |
外科学 | 21724篇 |
综合类 | 35400篇 |
现状与发展 | 55篇 |
一般理论 | 19篇 |
预防医学 | 13152篇 |
眼科学 | 6703篇 |
药学 | 22721篇 |
194篇 | |
中国医学 | 12387篇 |
肿瘤学 | 19253篇 |
出版年
2024年 | 698篇 |
2023年 | 3559篇 |
2022年 | 9200篇 |
2021年 | 11568篇 |
2020年 | 8606篇 |
2019年 | 7594篇 |
2018年 | 8035篇 |
2017年 | 7085篇 |
2016年 | 6655篇 |
2015年 | 10251篇 |
2014年 | 12549篇 |
2013年 | 10695篇 |
2012年 | 16003篇 |
2011年 | 17949篇 |
2010年 | 10514篇 |
2009年 | 8182篇 |
2008年 | 11113篇 |
2007年 | 11087篇 |
2006年 | 11227篇 |
2005年 | 11322篇 |
2004年 | 6998篇 |
2003年 | 6612篇 |
2002年 | 5498篇 |
2001年 | 4935篇 |
2000年 | 5344篇 |
1999年 | 5686篇 |
1998年 | 3524篇 |
1997年 | 3497篇 |
1996年 | 2813篇 |
1995年 | 2606篇 |
1994年 | 2142篇 |
1993年 | 1376篇 |
1992年 | 1891篇 |
1991年 | 1595篇 |
1990年 | 1290篇 |
1989年 | 1091篇 |
1988年 | 1014篇 |
1987年 | 890篇 |
1986年 | 726篇 |
1985年 | 525篇 |
1984年 | 336篇 |
1983年 | 242篇 |
1982年 | 149篇 |
1981年 | 145篇 |
1980年 | 111篇 |
1979年 | 142篇 |
1978年 | 49篇 |
1977年 | 53篇 |
1975年 | 57篇 |
1974年 | 56篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Lieqiang Liao Ruidong Liu Shuwen Hu Wenting Jiang Yali Chen Jinlian Zhong Xinjian Jia Huijin Liu Xuzhong Luo 《RSC advances》2022,12(31):20218
In this paper, we report self-assembled sonogels formed from 1,4-naphthalenedicarbonyldinicotinic acid hydrazide (NDC-NN3) in some liquids including ethanol, tetrahydrofuran (THF), 1,4-dioxane, n-propanol, n-butanol and n-pentanol. When the clear solution of NDC-NN3 in the selected liquids mentioned above at a suitable concentration was irradiated with ultrasound waves at room temperature, a sonogel was formed. Upon heating, the sonogel dissolved gradually and finally became a clear solution again. Upon cooling the hot solution to room temperature, the solution state did not change even after standing for a few days. Nevertheless, if the solution underwent sonication for a certain time, a stable gel was obtained again. The critical gelation concentrations (CGCs) of NDC-NN3 in ethanol, THF, 1,4-dioxane, n-propanol, n-butanol and n-pentanol are 10, 8, 6, 8, 6 and 8 mg mL−1, respectively. The obtained sonogels display excellent mechanical properties. The crystal structure of NDC-NN3 suggests that the naphthalene ring, hydrazide group and the position of N in the pyridine ring mediate the self-assembly process. Upon sonication, the formation of suitable π–π stacking and intermolecular hydrogen bonding drives the gelator molecules to self-assemble into fibers, spheres and micro-burdock-shaped balls in various solvents, which ultimately confine the liquids.Ultrasound-induced gelation of a novel type of gelator, 1,4-naphthalenedicarbonyl- dinicotinic acid hydrazide, is reported. The gelator self-assembled into various architectures in different solvents. 相似文献
962.
Xiurong Zhu Lousia J. Hope-Weeks Yi Yu Jvjun Yuan Xianke Zhang Huajun Yu Jiajun Liu Xiaofen Li Xianghua Zeng 《RSC advances》2022,12(31):20191
By using glycidol as a catalyst, high porosity, low-density resorcinol (R) and formaldehyde (F) aerogels and carbon aerogels (CAs) were synthesized via a sol-gel method. The effect of glycidol and water on the color, density, morphology, textual characteristics and adsorption properties of the resultant RF aerogels and CAs were investigated in detail. The results revealed that the properties of RF aerogels and CAs can be controlled by adjusting the amount of glycidol and water. The resultant RF aerogels and CAs were porous materials, the minimum densities of RF aerogels and CAs were 96 and 110 mg cm−3 respectively while the maximum specific surface areas of RF aerogels and CAs were 290 and 597 m2 g−1. The maximum adsorption capacity of CAs was about 125 mg g−1 on Rhodamine B, which was higher than that of some reported CAs catalyzed by base and acid catalysts. The sol-gel mechanisms of RF aerogels and CAs can be attributed to the opening of the epoxy group of glycidol in the mixture of R and F.The sol-gel mechanism of glycidol-catalyzed RF aerogels is the opening of the epoxy ring rather than the preservation the of epoxy ring. 相似文献
963.
964.
Longyu Wang Haoyang Li Xiao Wang Xiaofeng Liu Weiqing Ma Guangji Zhou Qiaochu Liang Huixia Lan 《RSC advances》2022,12(32):20983
In this study, the effect of pH shock during the treatment of sulfate-containing organic wastewater was investigated using an anaerobic fermentation system reinforced with graphene oxide (GO)/iron series systems. The results show that the anaerobic system with the GO/iron series systems exhibited enhanced resistance to pH shock. Among them, the GO/Fe0 system had the strongest resistance to pH shock, the systems of GO/Fe3O4 and GO/Fe2O3 followed close behind, while the blank system performed the worst. After pH shock, the CODCr removal rate, SO42− removal rate, and gas production of the GO/Fe0 group were significantly improved compared with those of the control group by 51.0%, 65.3%, and 34.6%, respectively, while the accumulation of propionic acid was the lowest. Further, detailed microbial characterization revealed that the introduction of the GO/iron series systems was beneficial to the formation of more stable anaerobic co-metabolic flora in the system, and the relative abundance of Geobacter, Clostridium, Desulfobulbus and Desulfovibrio increased after acidic and alkaline shock.In this paper, we studied the pH shock resistance mechanism of GO/iron series from the perspectives of the treatment effect, changes in effluent pH and VFA, and microbial co-metabolic stability, providing a reference for the practical application. 相似文献
965.
Heteroatom-doped carbon materials used in supercapacitors are low in cost and demonstrate extraordinary performance. Here, ethylenediamine tetraacetic acid (EDTA) with intrinsic N and O elements is selected as a raw material for the preparation of heteroatom self-doped porous carbon. Furthermore, N/O self-doped porous carbon with a large surface area has been successfully prepared using K2CO3 as the activator. The derived sample with a 1 : 2 molar ratio of EDTA to K2CO3 (EK-2) demonstrates a porous structure, rich defects, a large surface area of 2057 m2 g−1 and a micropore volume of 0.25 cm3 g−1. Benefiting from high N content (2.89 at%) and O content (10.75 at%), EK-2 exhibits superior performance, including high capacitance of 325 F g−1 at 1 A g−1 and outstanding cycling stability with 96.8% retention after 8000 cycles at 10 A g−1, which strongly confirms its immense potential toward many applications. Additionally, the maximum energy density of EK-2 reaches was 17.01 W h kg−1 at a power density of 350 W kg−1 in a two-electrode system. This facile and versatile strategy provides a scalable approach for the batch synthesis of N/O co-doped carbonaceous electrode materials for energy storage.Heteroatom-doped carbon materials used in supercapacitors are low in cost and demonstrate extraordinary performance. 相似文献
966.
967.
Polycystic ovary syndrome (PCOS) is associated with low-grade chronic inflammation.This was a retrospective case–control study.In the present study, the risk coefficients of neutrophil to lymphocyte ratio (NLR), high-sensitive C-reactive protein (hs-CRP), and mean platelet volume (MPV) in obese patients with PCOS were determined. This study was designed to investigate NLR, hs-CRP, and MPV levels in 68 obese patients with PCOS and 44 nonobese patients with PCOS, and our study group was matched with 47 obese and 43 nonobese controls, respectively.PCOS group had higher MPV, NLR, insulin, glucose, and HOMA-IR rates than those of the controls. Subgroup analyses revealed that the obese PCOS group had higher NLR, hs-CRP, and MPV levels compared to those of controls. The obese PCOS group had higher NLR, hs-CRP, and MPV levels compared to those of the nonobese PCOS group. The odds ratios and 95% confidence intervals of those variables (NLR, hs-CRP, MPV) were found significant (P < .05). NLR, hs-CRP, and MPV variables were found statistically significant in the analysis of receiver operating characteristics.Our study demonstrated that NLR, hs-CRP, and MPV levels are increased in patients with obese PCOS. 相似文献
968.
969.
970.
Coronavirus disease 2019 (COVID-19) was first detected in China in December 2019, and declared as a pandemic by the World Health Organization (WHO) on March 11, 2020.To study the clinical features of patients with COVID-19, we analyzed the correlation between some inflammation-related indicators in patients’ serum and the severity of the disease, especially PV (pneumonia volume under CT scan) and pneumonia volume ratio (PVR).Sixty-six COVID-19 patients in Huai’an, China were selected as the research subjects. We collected the clinical data, including general characteristics, clinical symptoms, serum test results and CT performance, explored the relationship between inflammation-related indexes, oxygenation index, PV, PVR, while indicators of mild to moderate patients and severe patients were compared.The most prominent manifestations of COVID-19 patients were fever (47, 71.2%); cough (41, 62.1%), with or without respiratory and other systemic symptoms; There was no difference in gender (P = .567) and age (P = .865) between mild to moderate and severe groups. High sensitivity C-reactive protein (hs-CRP), erythrocyte sedimentation rate (ESR), and interleukin-6 (IL-6) of overall patients were higher than the normal range (P < .001, respectively). hs-CRP was negatively correlated with oxygenation index (OI) (r = –0.55), whereas positively correlated with PV, PVR and ESR (r = 0.89; r = 0.87; r = 0.47, respectively); ESR was negatively correlated with OI (r = –0.45), meanwhile it was positively correlated with PV and PVR (r = 0.44; r = 0.46, respectively). OI was negatively correlated with PV and PVR (r = –0.6, respectively). PV had a clear correlation with PVR (r = 1). Severe patients’ hs-CRP, PV, PVR were higher than mild to moderate group (P = .006; P = .001; P < .001, respectively), but OI was lower (P < .001).The clinical features of COVID-19 were similar to general viral pneumonia. hs-CRP, ESR showed a certain correlation with the PV and PVR, which might play a certain role in assessing the severity of COVID-19. 相似文献