全文获取类型
收费全文 | 5264篇 |
免费 | 395篇 |
国内免费 | 489篇 |
专业分类
6148篇 |
出版年
2024年 | 10篇 |
2023年 | 73篇 |
2022年 | 176篇 |
2021年 | 311篇 |
2020年 | 206篇 |
2019年 | 232篇 |
2018年 | 256篇 |
2017年 | 181篇 |
2016年 | 236篇 |
2015年 | 319篇 |
2014年 | 396篇 |
2013年 | 391篇 |
2012年 | 487篇 |
2011年 | 436篇 |
2010年 | 276篇 |
2009年 | 267篇 |
2008年 | 279篇 |
2007年 | 256篇 |
2006年 | 195篇 |
2005年 | 146篇 |
2004年 | 164篇 |
2003年 | 134篇 |
2002年 | 91篇 |
2001年 | 76篇 |
2000年 | 81篇 |
1999年 | 73篇 |
1998年 | 43篇 |
1997年 | 47篇 |
1996年 | 46篇 |
1995年 | 40篇 |
1994年 | 30篇 |
1993年 | 27篇 |
1992年 | 26篇 |
1991年 | 17篇 |
1990年 | 17篇 |
1989年 | 19篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 10篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1979年 | 8篇 |
1975年 | 7篇 |
1974年 | 4篇 |
1971年 | 4篇 |
1970年 | 4篇 |
1969年 | 2篇 |
1966年 | 3篇 |
1965年 | 3篇 |
排序方式: 共有6148条查询结果,搜索用时 15 毫秒
121.
The current Whale Optimization Algorithm(WOA)has several drawbacks,such as slow convergence,low solution accuracy and easy to fall into the local optimal soluti... 相似文献
122.
123.
Jordan Bai Muhammad Farid Abdul-Rahman Anne Rifkin-Graboi Yap-Seng Chong Kenneth Kwek Seang-Mei Saw Keith M. Godfrey Peter D. Gluckman Marielle V. Fortier Michael J. Meaney Anqi Qiu 《PloS one》2012,7(10)
We studied a sample of 75 Chinese, 73 Malay, and 29 Indian healthy neonates taking part in a cohort study to examine potential differences in neonatal brain morphology and white matter microstructure as a function of ethnicity using both structural T2-weighted magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI). We first examined the differences in global size and morphology of the brain among the three groups. We then constructed the T2-weighted MRI and DTI atlases and employed voxel-based analysis to investigate ethnic differences in morphological shape of the brain from the T2-weighted MRI, and white matter microstructure measured by fractional anisotropy derived from DTI. Compared with Malay neonates, the brains of Indian neonates’ tended to be more elongated in anterior and posterior axis relative to the superior-inferior axis of the brain even though the total brain volume was similar among the three groups. Although most anatomical regions of the brain were similar among Chinese, Malay, and Indian neonates, there were anatomical variations in the spinal-cerebellar and cortical-striatal-thalamic neural circuits among the three populations. The population-related brain regions highlighted in our study are key anatomical substrates associated with sensorimotor functions. 相似文献
124.
125.
Zheng Yang Xinmeng Qi Neil Gross Xiujuan Kou Yunlong Bai Yaru Feng Bochun Wang Mark E. Zafereo Guojun Li Chuanzheng Sun Huihui Li Xiaohong Chen Zhigang Huang 《Journal of cellular and molecular medicine》2020,24(22):13163
Genetic analysis for germline mutations of RET proto‐oncogene has provided a basis for individual management of medullary thyroid carcinoma (MTC) and pheochromocytoma. Most of compound mutations have more aggressive phenotypes than single point mutations, but the compound C634Y/V292M variant in MTC has never been reported. Thus, we retrospectively investigated synergistic effect of C634Y and V292M RET germline mutations in family members with multiple endocrine neoplasia type 2A. Nine of 14 family members in a northern Chinese family underwent RET mutation screening using next‐generation sequencing and PCR followed by direct bidirectional DNA sequencing. Clinical features of nine individuals were retrospectively carefully reviewed. In vitro, the scratch‐wound assay was used to investigate the difference between the cells carrying different mutations. We find no patients died of MTC. All 3 carriers of the V292M variant were asymptomatic and did not have biochemical or structural evidence of disease (age: 82, 62 and 58). Among 4 C634Y mutation carriers, 2 patients had elevated calcitonin with the highest (156 pg/mL) in an 87‐year‐old male. Two carriers of compound C634Y/V292M trans variant had bilateral MTC with pheochromocytoma or lymph node metastasis (age: 54 and 41 years, respectively). Further, the compound C634Y/V292M variant had a faster migration rate than either single point mutation in vitro (P < .05). In conclusion, the V292M RET variant could be classified as ‘likely benign’ according to ACMG (2015). The compound variant V292M/C634Y was associated with both more aggressive clinical phenotype and faster cell growth in vitro than was either single mutation. 相似文献
126.
127.
Yizhi Jiang Dongping Huang Yuji Kondo Miao Jiang Zhenni Ma Lu Zhou Jian Su Xia Bai Changgeng Ruan Zhaoyue Wang Lijun Xia 《Journal of cellular and molecular medicine》2020,24(7):4356-4361
Hereditary thrombotic thrombocytopenic purpura (TTP) is an autosomal recessive thrombosis disorder, caused by loss-of-function mutations in ADAMTS13. Mutations in the CUB domains of ADAMTS13 are rare, and the exact mechanisms through which these mutations result in the development of TTP have not yet been fully elucidated. In this study, we identified two novel mutations in the CUB domains in a TTP family with an acceptor splice-site mutation (c.3569−1, G>A, intron 25) and a point missense mutation (c.3923, G>A, exon 28), resulting in a glycine to aspartic acid substitution (p.G1308D). In vitro splicing analysis revealed that the intronic mutation resulted in abnormal pre-mRNA splicing, and an in vitro expression assay revealed that the missense mutation significantly impaired ADAMTS13 secretion. Although both the patient and her brother displayed significantly reduced ADAMTS13 activity and increased levels of ultra-large VWF (ULVWF) multimers in plasma, only the female developed acute episodes of TTP. Our findings indicate the importance of the CUB domains for the protein stability and extracellular secretion of ADAMTS13. 相似文献
128.
The unique physicochemical properties of (2D) nanomaterials make them well‐suited for use in sustainable energy applications. Many of these materials can be further improved with vacancy engineering. This review details recent progress in the vacancy engineering of ultrathin 2D nanomaterials. For clarity, it mainly focuses on various ultrathin 2D materials in three categories: Xa&XaYb‐, MaXb‐, or MaXbYc‐structured materials. Recently developed vacancies in different types of ultrathin 2D materials, as well as their preparation and characterization, are described. Emphasis is placed on the potential electrochemical energy storage and conversion applications of these materials. This review considers the relationship between vacancy properties and material categories of various ultrathin 2D materials in terms of application requirements, preparation, and characterization techniques. The challenges and future outlook of this promising field are summarized. 相似文献
129.
Junjie Yu Yunfei Xing Chaoliang Hu Zhijie Huang Qinyi Qiu Chao Wang Kaiyang Xia Zhenyi Wang Shengqiang Bai Xinbing Zhao Lidong Chen Tiejun Zhu 《Liver Transplantation》2020,10(25)
Half‐Heusler (HH) compounds have shown great potential in waste heat recovery. Among them, p‐type NbFeSb and n‐type ZrNiSn based alloys have exhibited the best thermoelectric (TE) performance. However, TE devices based on NbFeSb‐based HH compounds are rarely studied. In this work, bulk volumes of p‐type (Nb0.8Ta0.2)0.8Ti0.2FeSb and n‐type Hf0.5Zr0.5NiSn0.98Sb0.02 compounds are successfully prepared with good phase purity, compositional homogeneity, and matchable TE performance. The peak zTs are higher than 1.0 at 973 K for Hf0.5Zr0.5NiSn0.98Sb0.02 and at 1200 K for (Nb0.8Ta0.2)0.8Ti0.2FeSb. Based on an optimal design by a full‐parameters 3D finite element model, a single stage TE module with 8 n‐p HH couples is assembled. A high conversion efficiency of 8.3% and high power density of 2.11 W cm?2 are obtained when hot and cold side temperatures are 997 and 342 K, respectively. Compared to the previous TE module assembled by the same materials, the conversion efficiency is enhanced by 33%, while the power density is almost the same. Given the excellent mechanical robustness and thermal stability, matchable thermal expansion coefficient and TE properties of NbFeSb and ZrNiSn based HH alloys, this work demonstrates their great promise for power generation with both high conversion efficiency and high power density. 相似文献
130.
Tao Wang Huimin Luo Yaocai Bai Jianlin Li Ilias Belharouak Sheng Dai 《Liver Transplantation》2020,10(30)
Ionic liquids (ILs) are a family of nonconventional molten salts that offer many advantages, such as negligible vapor pressures, negligible flammability, wide liquidus ranges, good thermal stability, and much synthesis flexibility. The unique solvation environment of these ILs provides new reaction or flux media for controlling formation of solid‐state materials with a minimum perturbation of morphologies. A successful lithiation via ionothermal synthesis using a cost‐effective Li halide as Li source and recyclable ILs as solvents is reported here for the direct recycling of LiNi1/3Co1/3Mn1/3O2 (NCM 111) cathodes. In addition, the ionic liquids can be readily recycled and reused after ionothermal lithiation. The lithiation of spent cathodes can enable the direct recycling of spent cathode materials in lithium‐ion batteries. 相似文献