全文获取类型
收费全文 | 4700篇 |
免费 | 298篇 |
国内免费 | 55篇 |
专业分类
耳鼻咽喉 | 103篇 |
儿科学 | 86篇 |
妇产科学 | 47篇 |
基础医学 | 714篇 |
口腔科学 | 106篇 |
临床医学 | 362篇 |
内科学 | 927篇 |
皮肤病学 | 173篇 |
神经病学 | 344篇 |
特种医学 | 398篇 |
外科学 | 704篇 |
综合类 | 36篇 |
预防医学 | 218篇 |
眼科学 | 56篇 |
药学 | 400篇 |
中国医学 | 55篇 |
肿瘤学 | 324篇 |
出版年
2023年 | 35篇 |
2022年 | 94篇 |
2021年 | 145篇 |
2020年 | 78篇 |
2019年 | 95篇 |
2018年 | 151篇 |
2017年 | 93篇 |
2016年 | 167篇 |
2015年 | 189篇 |
2014年 | 295篇 |
2013年 | 290篇 |
2012年 | 392篇 |
2011年 | 380篇 |
2010年 | 204篇 |
2009年 | 208篇 |
2008年 | 248篇 |
2007年 | 242篇 |
2006年 | 252篇 |
2005年 | 251篇 |
2004年 | 206篇 |
2003年 | 176篇 |
2002年 | 176篇 |
2001年 | 85篇 |
2000年 | 77篇 |
1999年 | 79篇 |
1998年 | 20篇 |
1997年 | 20篇 |
1996年 | 36篇 |
1995年 | 21篇 |
1994年 | 14篇 |
1993年 | 17篇 |
1992年 | 34篇 |
1991年 | 37篇 |
1990年 | 26篇 |
1989年 | 22篇 |
1988年 | 29篇 |
1987年 | 19篇 |
1986年 | 25篇 |
1985年 | 15篇 |
1984年 | 13篇 |
1983年 | 14篇 |
1982年 | 11篇 |
1979年 | 14篇 |
1978年 | 5篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1975年 | 7篇 |
1974年 | 8篇 |
1972年 | 4篇 |
1969年 | 3篇 |
排序方式: 共有5053条查询结果,搜索用时 15 毫秒
991.
There are no data on the relative accuracy and precision of regional bone mass measurement from whole-body dual energy X-ray absorptiometry (DXA) scans in small young subjects. Twelve domestic swine piglets (2550-17,660 g) were scanned on a single-beam and on a fan beam densitometer using each humerus and femur as the region of interest to determine the validity of five different scan modes: two infant whole body (IWB), two spine, and one rat whole body (RWB) scan mode in the determination of regional bone mass measurements. DXA bone mineral content (BMC( measurements from RWB and IWB fan beam and IWB single-beam scans were highly predictive of ash weight (adjusted r2 = 0.98, 0.94, 0.94, respectively). Correlation between left and right limbs was highly significant (p < 0.001 for all comparisons) for ash weight (r = 0.99) and for DXA measurements of BMC (r = 0.92-0.99), area (r = 0.92-0.99), and bone mineral density (r = 0.87-0.99) for all modes of DXA scan. Repeatability (as standard deviation of differences of repeated scans) varied with scan mode and DXA parameters and ranged from 1.5 to 7.6%and from 1.8 to 14.7% for intra-and interoperator, respectively. We conclude that regional DXA measurements from IWB and RWB scans can be assessed accurately and with adequate precision for clinical use in subjects with low bone mass comparable with infants and young children. The RWB scan is useful for research studies. However, appropriate training and documentation of precision errors is needed to minimize repeatability errors. 相似文献
992.
By means of a simple mixing procedure, we have constructed cationic Sendai virosomes consisting of fusogenic viral F/HN proteins and cationic lipids. Sendai virus F/HN proteins were purified by Triton X-100 treatment and sequential centrifugation, and then quantitatively added to cationic liposomes. The presence of HN proteins is essential for hemolytic activity of Sendai virus as well as efficient gene transfection. The amount of detergent added for purification of F/HN proteins was also crucial for hemolytic activity. The relevance of F/HN proteins in the gene-transfer capability of the cationic Sendai F/HN virosomes (CSVs) was verified by heat inactivation of the F/HN proteins, and cell-binding competition. DNA condensation by protamine sulfate was able to further enhance the transfection efficiency and serum resistance of CSV. The enhanced transfection efficiency of protamine-condensed DNA-encapsulating cationic Sendai F/HN virosomes (PCSVs) may result from specific and efficient cell binding mediated by F/HN proteins and efficient DNA encapsulation by protamine. The DNA condensation by protamine was crucial for systemic in vivo gene transfer by CSVs. The PCSVs exhibited a higher gene expression in various organs, especially the liver, compared to DOTAP/Chol lipoplexes. These results demonstrate the potential for the use of PCSV as gene delivery vehicles for systemic gene transfer. 相似文献
993.
Qi Ying Koo Asif M. Khan Keun-Ok Jung Shweta Ramdas Olivo Miotto Tin Wee Tan Vladimir Brusic Jerome Salmon J. Thomas August 《PLoS Clinical Trials》2009,4(4)
West Nile virus (WNV) has emerged globally as an increasingly important pathogen for humans and domestic animals. Studies of the evolutionary diversity of the virus over its known history will help to elucidate conserved sites, and characterize their correspondence to other pathogens and their relevance to the immune system. We describe a large-scale analysis of the entire WNV proteome, aimed at identifying and characterizing evolutionarily conserved amino acid sequences. This study, which used 2,746 WNV protein sequences collected from the NCBI GenPept database, focused on analysis of peptides of length 9 amino acids or more, which are immunologically relevant as potential T-cell epitopes. Entropy-based analysis of the diversity of WNV sequences, revealed the presence of numerous evolutionarily stable nonamer positions across the proteome (entropy value of ≤1). The representation (frequency) of nonamers variant to the predominant peptide at these stable positions was, generally, low (≤10% of the WNV sequences analyzed). Eighty-eight fragments of length 9–29 amino acids, representing ~34% of the WNV polyprotein length, were identified to be identical and evolutionarily stable in all analyzed WNV sequences. Of the 88 completely conserved sequences, 67 are also present in other flaviviruses, and several have been associated with the functional and structural properties of viral proteins. Immunoinformatic analysis revealed that the majority (78/88) of conserved sequences are potentially immunogenic, while 44 contained experimentally confirmed human T-cell epitopes. This study identified a comprehensive catalogue of completely conserved WNV sequences, many of which are shared by other flaviviruses, and majority are potential epitopes. The complete conservation of these immunologically relevant sequences through the entire recorded WNV history suggests they will be valuable as components of peptide-specific vaccines or other therapeutic applications, for sequence-specific diagnosis of a wide-range of Flavivivirus infections, and for studies of homologous sequences among other flaviviruses. 相似文献
994.
INTRODUCTION: Tacrolimus ointment is a nonsteroid treatment for atopic dermatitis which is both effective and has a minimal side-effect profile. However, some clinicians may be reluctant to use tacrolimus ointment due to the "unknown risks", meaning those that have not been uncovered in human studies conducted thus far. Therefore, the available animal data regarding the "unknown risks" of topical tacrolimus therapy are reviewed, and a discussion of the interpretation of this available but limited data is presented. ANIMAL STUDIES: Some of the fear on the part of clinicians regarding the use of topical tacrolimus may come from the results of animal studies which showed an increase in lymphoma and UV-induced skin cancer after treatment with topical tacrolimus in animal models of carcinogenesis. However, rigorous assessment of these studies suggest that it is somewhat likely that these represent a species-specific response to tacrolimus in an animal already predisposed to tumor formation, and therefore may not be relevant in assessing the possibility of an increased human health risk. CONCLUSIONS: Animal and human studies suggest that topical tacrolimus is a safe alternative to topical steroids, with the major known adverse effect being a transient burning sensation, compared with the known adverse effects of topical steroids, including long-lasting ones. Therefore, in the opinion of the authors, currently available data, including animal studies, does not suggest that "unknown risks" of topical tacrolimus need be any more concerning than the known side-effects of the topical steroids. 相似文献
995.
The authors studied human vagus nerve electrophysiology intraoperatively on 21 patients (age range: 4 to 31 years) during implantation of a vagus nerve stimulator for seizure control. The study was performed with direct electrical stimulation of the vagus nerve with various stimulation parameters resembling those employed by the Cyberonics NeuroCybernetic Prosthesis System (Houston, TX), which is used clinically for vagus nerve stimulation for treatment of seizures. Recordings were made directly from the rostral end of the vagus nerve. The response of the vagus nerve to various stimulus parameters in patients of different ages was studied. Based on the vagus nerve characteristics, age-related adjustments for stimulus parameters were recommended. 相似文献
996.
Hyun-Na Koo Seung-Hwan Yun HyunKyung Kim 《International journal of radiation biology》2013,89(3):360-367
AbstractPurpose: The objective of the present study was to elucidate the mode of indirect action of electron beam irradiation at the molecular level against a quarantine pest, Spodoptera litura (F.).Material and methods: Electron beam irradiation (50–200?Gy) was applied to S. litura eggs, larvae, pupae, and adults, after which the feeding area, body weight, deformity of pupae and adults, ovarian development, expression levels of vitellogenin (Vg) and vitellogenin receptor (VgR) genes, and protein levels were analyzed.Results: The amount of feeding by S. litura larvae and the synthesis level of 70?kDa storage protein significantly decreased as the electron beam dose increased. When larvae were treated with the electron beam, morphological deformities appeared in the pupae, and abnormal wing disc (AWD) expression significantly decreased. Ovarian development was completely inhibited in emerged adults that had undergone 200?Gy electron beam irradiation as pupae. Quantitative real-time PCR (qRT-PCR) assays showed significant downregulation of the Vg and VgR genes due to electron beam irradiation; whereas the synthesis level of Vg protein (190?kDa) did not decrease with time in eggs unlike in non-irradiated (control) S. litura eggs, exhibiting irradiation induced impairment of Vg functioning.Conclusions: These findings of radiation-induced abnormal development and sterility in S. litura together with the correlated changes at the molecular level may facilitate the development of a phytosanitary strategy against this quarantine pest using electron beam irradiation. 相似文献
997.
998.
999.
The purpose of this study was to investigate the association between the expression of hypoxia-inducible factor (HIF)-1α, insulin-like growth factor (IGF)-1, glucose transporter 1 (Glut-1), carbonic anhydrase IX (CAIX), and monocarboxylate transporter (MCT)4, which are metabolism-related proteins in phyllodes tumors (PTs), and clinicopathologic factors and its implication. We used tissue microarrays to analyze 207 PTs and performed immunohistochemical staining against the glycolysis-related molecules HIF-1α, IGF-1, Glut-1, CAIX, and MCT4. We then compared the immunohistochemical results and clinicopathologic parameters. The expressions of HIF-1α, Glut-1, CAIX, and MCT4 in the stromal component of PTs increased (P?=?0.019, P?<?0.001, P?=?0.045, and P?<?0.001, respectively) with increasing tumor grade. According to univariate analysis, factors associated with shorter disease-free survival were Glut-1 expression (P?=?0.001) and MCT4 expression (P?<?0.001) in the stromal component, and the factors associated with shorter overall survival were IGF-1 expression (P?=?0.012), Glut-1 expression (P?<?0.001), CAIX expression (P?=?0.039), and MCT4 expression (P?<?0.001) in the stromal component. Our investigation of stromal expression of the metabolism-related proteins HIF-1α, IGF-1, Glut-1, CAIX, and MCT4 revealed that, as the PT grade increased, the stromal expression of HIF-1α, Glut-1, CAIX, and MCT4 significantly increased. This result suggested that increasing PT grade is associated with increased glycolysis in the stromal component. 相似文献
1000.