全文获取类型
收费全文 | 33070篇 |
免费 | 1540篇 |
国内免费 | 231篇 |
专业分类
耳鼻咽喉 | 414篇 |
儿科学 | 636篇 |
妇产科学 | 768篇 |
基础医学 | 3841篇 |
口腔科学 | 1566篇 |
临床医学 | 2638篇 |
内科学 | 8948篇 |
皮肤病学 | 465篇 |
神经病学 | 3111篇 |
特种医学 | 1169篇 |
外科学 | 4888篇 |
综合类 | 123篇 |
一般理论 | 8篇 |
预防医学 | 1677篇 |
眼科学 | 441篇 |
药学 | 1777篇 |
中国医学 | 122篇 |
肿瘤学 | 2249篇 |
出版年
2023年 | 209篇 |
2022年 | 467篇 |
2021年 | 917篇 |
2020年 | 515篇 |
2019年 | 705篇 |
2018年 | 921篇 |
2017年 | 647篇 |
2016年 | 778篇 |
2015年 | 916篇 |
2014年 | 1250篇 |
2013年 | 1679篇 |
2012年 | 2522篇 |
2011年 | 2689篇 |
2010年 | 1558篇 |
2009年 | 1407篇 |
2008年 | 2345篇 |
2007年 | 2391篇 |
2006年 | 2214篇 |
2005年 | 2249篇 |
2004年 | 1998篇 |
2003年 | 1716篇 |
2002年 | 1610篇 |
2001年 | 235篇 |
2000年 | 163篇 |
1999年 | 228篇 |
1998年 | 279篇 |
1997年 | 232篇 |
1996年 | 208篇 |
1995年 | 169篇 |
1994年 | 154篇 |
1993年 | 114篇 |
1992年 | 128篇 |
1991年 | 115篇 |
1990年 | 92篇 |
1989年 | 97篇 |
1988年 | 84篇 |
1987年 | 66篇 |
1986年 | 86篇 |
1985年 | 61篇 |
1984年 | 104篇 |
1983年 | 64篇 |
1982年 | 81篇 |
1981年 | 49篇 |
1980年 | 34篇 |
1979年 | 26篇 |
1978年 | 32篇 |
1977年 | 34篇 |
1976年 | 29篇 |
1974年 | 21篇 |
1973年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
Armando J. Parodi Ph.D. Edward W. Blank M.A. Jerry A. Peterson Ph.D. Roberto L. Ceriani M.D. Ph.D. 《Breast cancer research and treatment》1982,2(3):227-237
Summary The main dolichol diphosphate-bound oligosaccharides present in primary cultures of both normal and tumor mouse mammary epithelial cells had the same size, yielded the same pattern after acetolysis and paper chromatography, had the same number of mannose residues susceptible to-mannosidase degradation, and were composed of the same monosaccharide residues. This is the first demonstration that normal and tumor mammary cells have dolichol diphosphate-bound oligosaccharides with very similar, if not identical, structures. These compounds are intermediates in the synthesis of asparagine-linked oligosaccharides. On the other hand, normal and tumor cells showed differences in the specific activities of the enzymes involved in the transfer of the distal monosaccharides from the sugar nucleotides to glycoproteins. Sialyl- and fucosyl-transferases were elevated and galactosyl- and N-acetylglucosaminyltransferases were diminished in mammary tumor cells. The intact tumor cells showed an increased fucosylation of glycoproteins of the asparagine-linkage type.
Address for reprints: Roberto L. Ceriani, M.D., Ph.D., Bruce Lyon Memorial Research Laboratory, Children's Hospital Medical Center, 51st and Grove Streets, Oakland, CA 94609, USA. 相似文献
132.
Francesco Castelli Maria Grazia Sarpietro Chiara Messina Alessandra De Lazzari Dario Di Rosa Antonino Giannetto 《European journal of pharmaceutical sciences》2003,19(4):237-243
Nimesulide release from micronized and unmicronized drug particles was tested at pH 7.4 by measuring the transfer to dimyristoylphosphatidylcholine liposomes (multilamellar and unilamellar vesicles), chosen as a biomembrane model. The perturbing effect of increasing molar fractions of pure nimesulide on the thermotropic behaviour of dimyristoylphosphatidylcholine liposomes was investigated by differential scanning calorimetry. In order to study the drug dissolution process by its uptake into void liposomes, measurements were carried out on suspensions of blank liposomes added to weighed amounts of free powdered nimesulide (micronized and unmicronized). The amount of drug transferred was quantified by comparing the effect caused by the dissolved and released drug to that caused by the free drug that had been previously molecularly dissolved in the liposomes. The calorimetric results show that the dissolution rate depends on the nimesulide form (micronized or unmicronized), and that the transfer to the void liposomes is quicker when the drug is in a micronized form. The uptake was faster when unilamellar vesicles were used instead of multilamellar vesicles because of the greater lipid surface. The calorimetric technique could represent an alternative 'in vitro' method that can be applied to the study of the dissolution kinetics directly at the site of drug uptake, mimicking a biological system. 相似文献
133.
NIV indications and application in critically ill patients have considerably expanded in the last few years: the aim of this paper is to shortly review NIV main indications, on the basis of data from the current scientific literature. 相似文献
134.
Marco Herling George Z Rassidakis L Jeffrey Medeiros Theodoros P Vassilakopoulos Kay-Oliver Kliche Gianpaolo Nadali Simonetta Viviani Valeria Bonfante Roberto Giardini Marco Chilosi Christos Kittas Alessandro M Gianni Gianni Bonadonna Giovanni Pizzolo Gerassimos A Pangalis Fernando Cabanillas Andreas H Sarris 《Clinical cancer research》2003,9(6):2114-2120
PURPOSE: EBV-latent membrane protein-1 (LMP-1) is often expressed in Hodgkin and Reed-Sternberg (HRS) cells of classical Hodgkin's lymphoma (cHL), but its clinical significance is controversial. We correlated LMP-1 with presenting features, including serum interleukin 10 levels and clinical outcome. EXPERIMENTAL DESIGN: Patients were eligible if they had biopsy-proven cHL, were untreated, HIV-1 negative, and had available archival tissue. LMP-1 expression was determined by immunohistochemistry. RESULTS: We identified 577 patients with cHL with a median age of 30 years, 55% of whom were male. LMP-1 was expressed in HRS cells of 124 patients (21%) and was detected in 78 of 461 (17%) patients with nodular sclerosis compared with 44 of 112 (39%) with mixed cellularity (P < 0.001 by Fisher's exact test). Patients with tumors with LMP-1-positive HRS cells had higher serum interleukin 10 levels (P = 0.009 by Mann-Whitney test). For the 303 patients treated with doxorubicin, bleomycin, vinblastine, and dacarbazine or equivalent regimens, the 5-year failure-free survival (FFS) for those with LMP-1-positive tumors was 74% compared with 81% for those with LMP-1-negative tumors (P = 0.23, by log-rank test). Overall survival (OS) at 5 years for patients with LMP-1-positive tumors was 90 versus 91% for patients with LMP-1-negative tumors (P = 0.8 by log-rank test). Expression of LMP-1 was not associated with different FFS and OS in patients treated with other regimens or with radiotherapy alone. CONCLUSIONS: LMP-1 was expressed by HRS cells in 21% of cHL and correlated with mixed cellularity type and higher serum interleukin 10 levels. The presence of LMP-1 was not associated with FFS or OS in uniformly treated patients. 相似文献
135.
136.
Mauro Calvani Claudia Alessandri Giuseppe Paolone Luciano Rosengard Antonino Di Caro David De Franco 《Pediatric allergy and immunology》1997,8(2):91-96
It is currently accepted that vinil infections may influence the development of atopy. In the present study we evaluated serum IgE levels as well as the prevalence of symptom-, indicative of utopic disease and EBV antibodies in 353 children aged from I month to 19 years. Antibodies against EBV were detected by immunofluorescence. IgE levels in serum were measured by en/. yme imimmoassay. Dividing ihe study population according to EBV seropositivity and age, we noted that the prevalence of high IgE levels (> 2 s. d.) was, in total, more frequent in the EBV negative (32. 9%) than in the positive subjects (27. 6%). Interestingly, this higher prevalence was found only in the groups aged under six, especially in the 7 to 29 month group, where it was statistically significant (p=0.037), whereas in the 6-19 year group the situation was reversed. Furthermore, selecting only the atopic children younger than 3 years of age with high IgE levels and clinical symptoms of atopy (wheezing and/or dermatitis) it was possible to demonstrate lower EBV seropositivity compared with the normal IgE controls for each group, even though these differences were not statistically significant. In conclusion, the results of our study suggest that, in our selected population, EBV infection in the first years of life is associated with a lower prevalence of high IgE levels. 相似文献
137.
The relationship between dietary fat intake and risk of colorectal cancer: evidence from the combined analysis of 13 case-control studies 总被引:3,自引:0,他引:3
Geoffrey R. Howe Kristan J. Aronson Enrique Benito Roberto Castelleto Jacqueline Cornée Stephen Duffy Richard P. Gallagher José M. Iscovich Jiao Deng-ao Rudolf Kaaks Gabriel A. Kune Susan Kune Hin P. Lee Marion Lee Anthony B. Miller Ruth K. Peters John D. Potter Elio Riboli Martha L. Slattery Dimitrios Trichopoulos Albert Tuyns Anastasia Tzonou Lyndsey F. Watson Alice S. Whittemore Anna H. Wu-Williams Zheng Shu 《Cancer causes & control : CCC》1997,8(2):215-228
The objective of this study was to examine the effects of the intakeof dietary fat upon colorectal cancer risk in a combined analysis of datafrom 13 case-control studies previously conducted in populations withdiffering colorectal cancer rates and dietary practices. Original datarecords for 5,287 cases of colorectal cancer and 10,470 controls werecombined. Logistic regression analysis was used to estimate odds ratios (OR)for intakes of total energy, total fat and its components, and cholesterol.Positive associations with energy intake were observed for 11 of the 13studies. However, there was little, if any, evidence of anyenergy-independent effect of either total fat with ORs of 1.00, 0.95, 1.01,1.02, and 0.92 for quintiles of residuals of total fat intake (P trend =0.67) or for saturated fat with ORs of 1.00, 1.08, 1.06, 1.21, and 1.06 (Ptrend = 0.39). The analysis suggests that, among these case-control studies,there is no energy-independent association between dietary fat intake andrisk of colorectal cancer. It also suggests that simple substitution of fatby other sources of calories is unlikely to reduce meaningfully the risk ofcolorectal cancer. 相似文献
138.
139.