全文获取类型
收费全文 | 2205篇 |
免费 | 88篇 |
专业分类
2293篇 |
出版年
2024年 | 4篇 |
2023年 | 11篇 |
2022年 | 38篇 |
2021年 | 48篇 |
2020年 | 27篇 |
2019年 | 51篇 |
2018年 | 57篇 |
2017年 | 36篇 |
2016年 | 87篇 |
2015年 | 118篇 |
2014年 | 125篇 |
2013年 | 159篇 |
2012年 | 216篇 |
2011年 | 208篇 |
2010年 | 140篇 |
2009年 | 111篇 |
2008年 | 163篇 |
2007年 | 145篇 |
2006年 | 91篇 |
2005年 | 97篇 |
2004年 | 81篇 |
2003年 | 69篇 |
2002年 | 42篇 |
2001年 | 29篇 |
2000年 | 29篇 |
1999年 | 27篇 |
1998年 | 8篇 |
1997年 | 10篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 11篇 |
1991年 | 4篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1969年 | 2篇 |
1968年 | 1篇 |
1967年 | 3篇 |
1965年 | 1篇 |
排序方式: 共有2293条查询结果,搜索用时 15 毫秒
91.
92.
93.
Geon Ha Kim Seun Jeon Kiho Im Hunki Kwon Byung Hwa Lee Ga Young Kim Hana Jeong Noh Eul Han Sang Won Seo Hanna Cho Young Noh Sang Eon Park Hojeong Kim Jung Won Hwang Cindy W. Yoon Hee Jin Kim Byoung Seok Ye Ju Hee Chin Jung-Hyun Kim Mee Kyung Suh Jong Min Lee Sung Tae Kim Mun-Taek Choi Mun Sang Kim Kenneth M Heilman Jee Hyang Jeong Duk L. Na 《PloS one》2015,10(4)
The purpose of this study was to investigate if multi-domain cognitive training, especially robot-assisted training, alters cortical thickness in the brains of elderly participants. A controlled trial was conducted with 85 volunteers without cognitive impairment who were 60 years old or older. Participants were first randomized into two groups. One group consisted of 48 participants who would receive cognitive training and 37 who would not receive training. The cognitive training group was randomly divided into two groups, 24 who received traditional cognitive training and 24 who received robot-assisted cognitive training. The training for both groups consisted of daily 90-min-session, five days a week for a total of 12 weeks. The primary outcome was the changes in cortical thickness. When compared to the control group, both groups who underwent cognitive training demonstrated attenuation of age related cortical thinning in the frontotemporal association cortices. When the robot and the traditional interventions were directly compared, the robot group showed less cortical thinning in the anterior cingulate cortices. Our results suggest that cognitive training can mitigate age-associated structural brain changes in the elderly.
Trial Registration
ClnicalTrials.gov NCT01596205 相似文献94.
Daemin Kim Kevin W. Conway Hyung-Bae Jeon Ye-Seul Kwon Yong-Jin Won 《Conservation Genetics》2013,14(4):757-769
The dwarf loach, Kichulchoia brevifasciata, is a primary freshwater fish endemic to South Korea (Republic of Korea). Due to its limited geographic range, special habitat requirements, and scarcity, this species has been considered one of the most endangered cobitid loaches in the world. Gene tree and species tree reconstruction derived from mitochondrial and nuclear sequence data supports the exclusivity of K. brevifasciata and the existence of two highly distinct genetic lineages (eastern and western lineages). Intraspecific genetic variation based on the corrected genetic distance ranged from 0.0013 to 0.0017 (cytochrome b) and 0–0.0012 (nuclear loci) within each lineage and 0.0349 (cytochrome b) and 0.0037–0.0104 (nuclear loci) between the lineages. Although morphologically homogeneous, eastern and western lineages were estimated to have diverged roughly 2.79 million years ago (4.25–1.42, 95 % HPD). Future conservation efforts for K. brevifasciata should consider these genetically distinct lineages as separate evolutionary entities and adopt conservation efforts accordingly. 相似文献
95.
96.
Emerging solar cells, namely, organic solar cells and perovskite solar cells, are the thin‐film photovoltaics that have light to electricity conversion efficiencies close to that of silicon solar cells while possessing advantages in having additional functionalities, facile‐processability, and low fabrication cost. To maximize these advantages, the electrode components must be replaced by materials that are more flexible and cost‐effective. Researchers around the globe have been looking for the new electrodes that meet these requirements. Among many candidates, single‐walled carbon nanotubes have demonstrated their feasibility as the new alternative to conventional electrodes, such as indium tin oxide and metals. This review discusses various growth methods of single‐walled carbon nanotubes and their electrode applications in thin‐film photovoltaics. 相似文献
97.
Alkynyl Pd(II) azido complexes of the type [Pd(N3)(CCR)L2] (1-3) were obtained by reactions of aqueous NaN3 with [Pd(Cl)(CCR)L2] (R = Ph or C(O)OMe). Treating compounds 1-3 with organic isocyanides (R-NC) afforded novel complexes, trans-[Pd(CCPh)(NCNR)(PMe3)2] (R = 2,6-Me2C6H3 (4) or 2,6-Et2C6H3 (5)) and trans-[Pd(CCR)(CN4-t-Bu)L2] (6: L = PMe3, R = Ph; 7: L = PEt3, R = C(O)OMe; 8: L = PMe3, R = C(O)OMe), which contain either a carbodiimido or a C-coordinated tetrazolato group. Reactions of compounds 1 and 2 with R-NCS (R = 2,6-Me2C6H3 or CH2CH3) and 1,4-phenylene diisothiocyanate (C6H4(NCS)2) smoothly proceeded to give tetrazole-thiolato complexes, trans-[Pd(CCPh)(SCN4-R)L2] (L = PMe3, R = Et (9) or 2,6-Me2C6H3 (10); L = PEt3, R = 2,6-Me2C6H3 (11)), and a phenylene-bridged dinuclear Pd(II) tetrazole-thiolato complex, [(PEt3)2(CCPh)Pd(SCN4-(μ-C6H4)-SCN4)Pd(CCPh)(PEt3)2] (12), respectively. Complexes 9-12 contain the Pd-S bond that is formed by the dipolar cycloaddition of the organic isothiocyanate to the Pd-azido bond. In contrast, the corresponding reactions of compounds 1and 2 with C6F5CN and Me3SiCN (organic nitriles, R-CN) gave an N-coordinated Pd(II)-tetrazolato compound {trans-[Pd(CCPh)(N4C-C6F5)(PMe3)2] (13)} and a mixture of Pd(II)-cyano complexes {trans-[Pd(CCPh)(CN)(PEt3)2] (14) and [Pd(CN)2(PEt3)2] (15)}, respectively. Bis(phosphine) bis(cyano) complexes of Pd and Ni, [M(CN)2L2] (L = PEt3, PMe3; L2 = DEPE), could be obtained independently by the reactions of [M(N3)2L2] with excess Me3SiCN in organic solvents. 相似文献
98.
Yun YR Kim HW Kang W Jeon E Lee S Lee HY Kim CH Jang JH 《Protein expression and purification》2012,83(1):47-51
Dentin sialoprotein (DSP) is cleaved from dentin sialophosphoprotein (DSPP) and most abundant dentinal non-collagenous proteins in dentin. DSP is believed to participate in differentiation and mineralization of cells. In this study, we first constructed recombinant human DSP (rhDSP) in Escherichia coli (E. coli) and investigated its odontoblastic differentiation effects on human dental pulp cells (hDPCs). Cell adhesion activity was measured by crystal violet assay and cell proliferation activity was measured by MTT assay. To assess mineralization activity of rhDSP, Alizarin Red S staining was performed. In addition, the mRNA levels of collagen type ? (Col ?), alkaline phosphatase (ALP), and osteocalcin (OCN) were measured due to their use as mineralization markers for odontoblast-/osteoblast-like differentiation of hDPCs. The obtained rhDSP in E. coli was approximately identified by SDS-PAGE and Western blot. Initially, rhDSP significantly enhanced hDPCs adhesion activity and proliferation (p<0.05). In Alizarin Red S staining, stained hDPCs increased in a time-dependent manner. This odontoblastic differentiation activity was also verified through mRNA levels of odontoblast-related markers. Here, we first demonstrated that rhDSP may be an important regulatory ECM in determining the hDPCs fate including cell adhesion, proliferation, and odontoblastic differentiation activity. These findings indicate that rhDSP can induce growth and differentiation on hDPCs, leading to improve tooth repair and regeneration. 相似文献
99.
Seo-Jung Han Jae Eun Jung Do Hee Oh Minsup Kim Jae-Min Kim Kyung-Sook Chung Hee-Soo Han Jeong-Hun Lee Kyung-Tae Lee Hee Jin Jeong In Ho Park Eunkyeong Jeon Jeon-Soo Shin Dongkeun Hwang Art E. Cho Duck-Hyung Lee Taebo Sim 《Journal of enzyme inhibition and medicinal chemistry》2022,37(1):1257
Identification of highly selective type II kinase inhibitors is described. Two different chiral peptidomimetic scaffolds were introduced on the tail region of non-selective type II kinase inhibitor GNF-7 to enhance the selectivity. Kinome-wide selectivity profiling analysis showed that type II kinase inhibitor 7a potently inhibited Lck kinase with great selectivity (IC50 of 23.0 nM). It was found that 7a and its derivatives possessed high selectivity for Lck over even structurally conserved all Src family kinases. We also observed that 7a inhibited Lck activation in Jurkat T cells. Moreover, 7a was found to alleviate clinical symptoms in DSS-induced colitis mice. This study provides a novel insight into the design of selective type II kinase inhibitors by adopting chiral peptidomimetic moieties on the tail region. 相似文献
100.
Amino acid-sugar alcohol conjugates were synthesized by a commercial serine protease, Optimase M-440, in organic media. Optimase M-440 showed broad substrate specificity towards N-t-Boc-protected l-amino acids as acyl donors and sugar alcohols as nucleophiles. Among various solvents tested Optimase M-440 showed the highest activity in pyridine. The regioselective acylation of the primary –OH groups of sugar alcohols gave the amino acid conjugates in good yields without byproducts. 相似文献