全文获取类型
收费全文 | 4777篇 |
免费 | 343篇 |
国内免费 | 1篇 |
专业分类
5121篇 |
出版年
2023年 | 24篇 |
2022年 | 58篇 |
2021年 | 92篇 |
2020年 | 63篇 |
2019年 | 71篇 |
2018年 | 100篇 |
2017年 | 91篇 |
2016年 | 175篇 |
2015年 | 216篇 |
2014年 | 240篇 |
2013年 | 334篇 |
2012年 | 388篇 |
2011年 | 373篇 |
2010年 | 233篇 |
2009年 | 198篇 |
2008年 | 295篇 |
2007年 | 309篇 |
2006年 | 268篇 |
2005年 | 255篇 |
2004年 | 223篇 |
2003年 | 199篇 |
2002年 | 202篇 |
2001年 | 46篇 |
2000年 | 26篇 |
1999年 | 40篇 |
1998年 | 65篇 |
1997年 | 28篇 |
1996年 | 37篇 |
1995年 | 49篇 |
1994年 | 23篇 |
1993年 | 39篇 |
1992年 | 28篇 |
1991年 | 23篇 |
1990年 | 16篇 |
1988年 | 13篇 |
1987年 | 21篇 |
1986年 | 15篇 |
1985年 | 16篇 |
1984年 | 15篇 |
1983年 | 15篇 |
1982年 | 14篇 |
1981年 | 17篇 |
1980年 | 17篇 |
1979年 | 8篇 |
1977年 | 10篇 |
1976年 | 12篇 |
1975年 | 16篇 |
1974年 | 10篇 |
1973年 | 10篇 |
1972年 | 11篇 |
排序方式: 共有5121条查询结果,搜索用时 31 毫秒
81.
Pavel A. Abramov Rita Hernandez-Molina Alexander V. Virovets Pedro Gili Vladimir P. Fedin 《Inorganica chimica acta》2010,363(13):3330-3337
Reaction of [Mo2O2(μ-S)2(H2O)6]2+ with Mo(CO)6 or metallic Mo under hydrothermal conditions (140 °C, 4 M HCl) gives oxido-sulfido cluster aqua complex [Mo3(μ3-S)(μ-O)2(μ-S)(H2O)9]4+ (1). Similarly, [W3(μ3-S)(μ-O)2(μ-S)(H2O)9]4+ (2) is obtained from [W2O2(μ-S)2(H2O)6]2+ and W(CO)6. While reaction of [Mo2O2(μ-S)2(H2O)6]2+ with W(CO)6 mainly proceeds as simple reduction to give 1, [W2O2(μ-S)2(H2O)6]2+ with Mo(CO)6 produces new mixed-metal cluster [W2Mo(μ3-S)(μ-O)2(μ-S)(H2O)9]4+ (3) as main product. From solutions of 1 in HCl supramolecular adduct with cucurbit[6]uril (CB[6]) {[Mo3O2S2(H2O)6Cl3]2CB[6]}Cl2⋅18H2O (4) was isolated and structurally characterized. The aqua complexes were converted into acetylacetonates [M3O2S2(acac)3(py)3]PF6 (M3 = Mo3, W3, W2Mo; 5a-c), which were characterized by X-ray single crystal analysis, electrospray ionization mass spectrometry and 1H NMR spectroscopy. Crystal structure of (H5O2)(Me4N)4[W3(μ3-S)(μ2-S)(μ2-O)2(NCS)9] (6), obtained from 2, is also reported. 相似文献
82.
José S. Ramalho Vanda S. Lopes Abul K. Tarafder Miguel C. Seabra Alistair N. Hume 《Pigment cell & melanoma research》2009,22(4):461-473
Myrip is a Rab27a and MyosinVIIa (MyoVIIa) linking protein that may regulate melanosome transport in the retinal pigment epithelium (RPE). Myrip also binds MyosinVa (MyoVa) in vitro however it is unclear whether this interaction is of sufficient affinity to be physiologically relevant. Here, we addressed the questions of whether Myrip interacts with MyoVa in cells and the molecular basis of cellular activation of MyoVa and MyoVIIa by Myrip. To answer these questions we used melanosome transport in skin melanocytes and RPE cells as read‐outs of MyoVa and MyoVIIa activity. We found that Myrip recruits and activates MyoVa on skin melanosomes with similar efficiency to the established MyoVa activator Melanophilin (Mlph). Mutagenesis showed that a Myrip–Mlph conserved amphipathic helix (MMAH) is essential for MyoVa interaction while other Myrip regions, including the MyoVa exon F binding domain equivalent, play non‐essential roles in this interaction. This suggests that, in contrast to Mlph, Myrip interacts with MyoVa lacking melanocyte‐specific exon F. Parallel studies of RPE melanosome transport reveal that Myrip‐specific inserts, but not the MMAH, are essential for MyoVIIa activation. We conclude that Myrip is a versatile Rab27a‐associated myosin‐activating protein that mediates cellular activation of MyoVa and MyoVIIa via non‐overlapping domains. 相似文献
83.
84.
Lorenzo Tancioni Tommaso Russo Stefano Cataudella Valentina Milana Anne Kathrin Hett Elisa Corsi Anna Rita Rossi 《PloS one》2013,8(4)
Leuciscine fishes represent an important component of freshwater ichthyofauna endemic to northern Mediterranean areas. This lineage shows high intra-specific morphological variability and exhibits high levels of hybridization, two characteristics that contribute to systematic uncertainties, misclassification of taxa and, potentially, the mismanagement of biodiversity. This study focused on brook chub, Squalius lucumonis, an endemic taxon of Central Italy. The taxonomic status of this species has long been questioned, and a hybrid origin from sympatric leusciscines (S. squalus x Rutilus rubilio, or S. squalus x Telestes muticellus) has been hypothesised. A phenotypic (evaluating shape and meristic counts) and genetic (using mitochondrial and nuclear markers) investigation of these four taxa was conducted to test species delimitation in sympatric areas and to evaluate the taxonomic status of S. lucumonis. One hundred and forty-five individuals of all four taxa were collected within streams of the lowest portion of the Tiber River basin and analysed; this region encompasses a large portion of the S. lucumonis distribution. The different morphological and genetic approaches were individually examined, compared, and then combined in a quantitative model to both investigate the limits of each approach and to identify cases of misclassification. The results obtained confirm the cladogenetic non-hybrid origin of S. lucumonis, highlight the need for immediate conservation actions and emphasise the value of an integrated approach in the study of leuciscines evolution. 相似文献
85.
Background
Microscopic colitis (MC) is a disease manifested by diarrhoea and is divided into collagenous and lymphocytic colitis. The aetiology is unknown, but auto-immunity is suggested. Auto-antibodies have been only rarely examined in this entity. The aim of the study was to examine the prevalence of auto-antibodies, and to examine associations between the presence of antibodies and clinical findings.Methods and Findings
Women with MC verified by biopsy and younger than 73 years, at any Department of Gastroenterology, in the district of Skåne, between 2002 and 2010 were invited to participate in this study. The patients were asked to complete both a questionnaire describing their medical history and the Gastrointestinal Symptom Rating Scale (GSRS). Blood samples were collected. Anti-nuclear antibodies (ANA), anti-neutrophil cytoplasmic antibodies (ANCA), anti-Saccharomyces cerevisiae antibodies (ASCA), and antibodies against glutamic acid decarboxylase (anti-GAD), islet antigens-like insulin 2 (anti-IA2), thyroid peroxidase (anti-TPO), and thyrotropin receptor (TRAK) were analysed. Of 240 women identified, 133 were finally included in the study, median age 63 (59–67) years. Apart from the MC diagnosis, 52% also suffered from irritable bowel syndrome, 31% from hypertension and 31% from allergy. The prevalence of ANA (14%), ASCA IgG (13%), and anti-TPO antibodies (14%) for these patients was slightly higher than for the general population, and were found together with other concomitant diseases. Patients had more of all gastrointestinal symptoms compared with norm values, irrespective of antibody expression.Conclusions
Women with MC have a slightly increased prevalence of some auto-antibodies. These antibodies are not associated with symptoms, but are expressed in patients with concomitant diseases, obscuring the pathophysiology and clinical picture of MC. 相似文献86.
Altilia S Pisciotta L Garuti R Tarugi P Cantafora A Calabresi L Tagliabue J Maccari S Bernini F Zanotti I Vergani C Bertolini S Calandra S 《Journal of lipid research》2003,44(2):254-264
Two point mutations of ABCA1 gene were found in a patient with Tangier disease (TD): i) G>C in intron 2 (IVS2 +5G>C) and ii) c.844 C>T in exon 9 (R282X). The IVS2 +5G>C mutation was also found in the brother of another deceased TD patient, but not in 78 controls and 33 subjects with low HDL. The IVS2 +5G>C mutation disrupts ABCA1 pre-mRNA splicing in fibroblasts, leading to three abnormal mRNAs: devoid of exon 2 (Ex2-/mRNA), exon 4 (Ex4-/mRNA), or both these exons (Ex2-/Ex4-/mRNA), each containing a translation initiation site. These mRNAs are expected either not to be translated or generate short peptides. To investigate the in vitro effect of IVS2 +5G>C mutation, we constructed two ABCA1 minigenes encompassing Ex1-Ex3 region, one with wild-type (WTgene) and the other with mutant (MTgene) intron 2. These minigenes were transfected into COS1 and NIH3T3, two cell lines with a different ABCA1 gene expression. In COS1 cells, WTgene pre-mRNA was spliced correctly, while the splicing of MTgene pre-mRNA resulted in Ex2-/mRNA. In NIH3T3, no splicing of MTgene pre-mRNA was observed, whereas WTgene pre-mRNA was spliced correctly. These results stress the complexity of ABCA1 pre-mRNA splicing in the presence of splice site mutations. 相似文献
87.
Sandrine Lagarrigue Lisa Martin Farhad Hormozdiari Pierre-Fran?ois Roux Calvin Pan Atila van Nas Olivier Demeure Rita Cantor Anatole Ghazalpour Eleazar Eskin Aldons J. Lusis 《Genetics》2013,195(3):1157-1166
We report an analysis of allele-specific expression (ASE) and parent-of-origin expression in adult mouse liver using next generation sequencing (RNA-Seq) of reciprocal crosses of heterozygous F1 mice from the parental strains C57BL/6J and DBA/2J. We found a 60% overlap between genes exhibiting ASE and putative cis-acting expression quantitative trait loci (cis-eQTL) identified in an intercross between the same strains. We discuss the various biological and technical factors that contribute to the differences. We also identify genes exhibiting parental imprinting and complex expression patterns. Our study demonstrates the importance of biological replicates to limit the number of false positives with RNA-Seq data. 相似文献
88.
—N-Acetyl-β-hexosaminidase A was purified to homogeneity from human and monkey brains by the conventional procedures followed by concanavalin A–Sepharose affinity chromatography. The optimal activity was observed at pH 4·5 for both enzyme preparations with both the aglycones N-acetylglucosamine and N-acetylgalactosamine derivatives. The Km values for hexosaminidase A from monkey brain were 0·26 mm and 0·04 mm respectively for N-acetylglucosamine and N-acetylgalactosamine. Km values obtained for glucosamine and galactosamine derivatives for the human brain hexosaminidase A were of the same order. The glycoprotein nature of the enzymes was established by the affinity towards concanavalin A as well as by the presence of sialic acid, galactose, glucose, mannose and hexosamines in the enzyme molecule from monkey brain. 相似文献
89.
Sudhir Chandra Joshi Vishal Diwan Ashok J. Tamhankar Rita Joshi Harshada Shah Megha Sharma Ashish Pathak Ragini Macaden Cecilia St?lsby Lundborg 《PloS one》2015,10(5)
Background
Health care or biomedical waste, if not managed properly, can be of high risk to the hospital staff, the patients, the community, public health and the environment, especially in low and middle income settings where proper disposal norms are often not followed. Our aim was to explore perceptions of staff of an Indian rural tertiary care teaching hospital on hospital waste management.Method
A qualitative study was conducted using 10 focus group discussions (FGDs), with different professional groups, cleaning staff, nurses, medical students, doctors and administrators. The FGD guide included the following topics: (i) role of Health Care Waste Management (HCWM) in prevention of health care associated infections, (ii) awareness of and views about HCWM-related guidelines/legislation, (iii) current HCWM practices, (iv) perception and preparedness related to improvements of the current practices, and (v) proper implementation of the available guidelines/legislation. The FGDs were recorded, transcribed verbatim, translated to English (when conducted in Hindi) and analysed using content analysis.Results
Two themes were identified: Theme (A), ‘Challenges in integration of HCWM in organizational practice,’ with the categories (I) Awareness and views about HCWM, (II) Organizational practices regarding HCWM, and (III) Challenges in Implementation of HCWM; and Theme (B), ‘Interventions to improve HCWM,’ with three categories, (I) Educational and motivational interventions, (II) Organizational culture change, and (III) Policy-related interventions.Conclusion
A gap between knowledge and actual practice regarding HCWM was highlighted in the perception of the hospital staff. The participants suggested organizational changes, training and monitoring to address this. The information generated is relevant not merely to the microsystem studied but to other institutions in similar settings. 相似文献90.