全文获取类型
收费全文 | 600篇 |
免费 | 104篇 |
国内免费 | 5篇 |
专业分类
耳鼻咽喉 | 16篇 |
儿科学 | 11篇 |
妇产科学 | 8篇 |
基础医学 | 34篇 |
口腔科学 | 17篇 |
临床医学 | 77篇 |
内科学 | 166篇 |
皮肤病学 | 9篇 |
神经病学 | 40篇 |
特种医学 | 194篇 |
外科学 | 54篇 |
综合类 | 12篇 |
预防医学 | 17篇 |
眼科学 | 11篇 |
药学 | 25篇 |
肿瘤学 | 18篇 |
出版年
2023年 | 11篇 |
2022年 | 8篇 |
2021年 | 18篇 |
2020年 | 5篇 |
2018年 | 30篇 |
2017年 | 13篇 |
2016年 | 17篇 |
2015年 | 21篇 |
2014年 | 39篇 |
2013年 | 49篇 |
2012年 | 8篇 |
2011年 | 15篇 |
2010年 | 35篇 |
2009年 | 46篇 |
2008年 | 22篇 |
2007年 | 16篇 |
2006年 | 13篇 |
2005年 | 12篇 |
2004年 | 14篇 |
2003年 | 6篇 |
2002年 | 7篇 |
2001年 | 10篇 |
2000年 | 8篇 |
1999年 | 8篇 |
1998年 | 22篇 |
1997年 | 23篇 |
1996年 | 16篇 |
1995年 | 13篇 |
1994年 | 9篇 |
1993年 | 15篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 21篇 |
1988年 | 16篇 |
1987年 | 14篇 |
1986年 | 10篇 |
1985年 | 15篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 10篇 |
1979年 | 6篇 |
1977年 | 6篇 |
1976年 | 10篇 |
1975年 | 6篇 |
1974年 | 3篇 |
1971年 | 3篇 |
1968年 | 4篇 |
排序方式: 共有709条查询结果,搜索用时 15 毫秒
21.
Steven Appleby MD Kent Mcallister RT Morton J. Kern MD 《Catheterization and cardiovascular interventions》2008,71(6):800-802
After inserting a catheter into a vessel, guidewire exchange technique must be used to maintain vascular access. If the lumen of the catheter is blocked and the guidewire exchange cannot be used, the catheter can only be removed, vascular access is lost, and an alternate vascular approach attempted. We describe a technique to remove the blocked catheter and still maintain vascular access. © 2008 Wiley‐Liss, Inc. 相似文献
22.
A. Keshavarzian MD F. L. Iber MD P. Greer RT J. Wobbteton RNNP 《Alcoholism, clinical and experimental research》1986,10(4):432-435
Nausea and vomiting are common complaints in chronic alcoholics. Autonomic neuropathy and esophageal motor abnormalities are frequently observed in chronic alcoholics, but gastric emptying has not been studied in these patients. Gastric emptying of a solid meal was measured, using 99mTc-sulfur colloid cooked in a scrambled egg, in 10 male chronic alcoholics with upper gastrointestinal complaints of nausea and vomiting. All patients were adequately nourished, recently drinking, but just over withdrawal and free of clinical peripheral neuropathy. Gastric emptying in 10 alcoholics was similar to 5 normal controls (t 1/2 115 +/- 12 versus 107 +/- 8 min). These data suggest that upper gastrointestinal symptoms in chronic alcoholics are not related to gastric motor dysfunction. 相似文献
23.
B-chronic lymphocytic leukemia (CLL) patients frequently suffer from moderate to severe hypogammaglobulinemia. This complication is a serious cause of morbidity and mortality in this disorder. There is recent evidence that natural killer (NK) cells modulate B-cell immunoglobin (Ig) synthesis/secretion. The authors therefore evaluated the circulating NK cells from B-CLL patients on their ability to regulate mitogen-induced B-cell Ig synthesis. Blood, NK cells (CD16+, CD3-) from three B-CLL patients with hypogammaglobulinemia were able to clearly down-regulate the pokeweed mitogen (PWM)-induced-B-cell Ig secretion. In contrast, CD16+, CD3- cells from age-sex-matched controls or B-CLL patients with normal Ig were either nonregulatory or enhanced mitogen-induced B-cell Ig secretion. An alternative explanation for hypogammaglobulinemia in B-CLL patients is the immunomodulation of B- cell Ig production/secretion by CD16+, CD3- blood cells. 相似文献
24.
High resolution of heterogeneity among human neutrophil granules: physical, biochemical, and ultrastructural properties of isolated fractions 总被引:4,自引:1,他引:4
Previous studies on the fractionation of human neutrophil granules have identified two major populations: myeloperoxidase (MPO)-containing azurophil, or primary, granules and MPO-deficient specific, or secondary, granules. Peripheral blood neutrophils from individual donors were lysed in sucrose-free media by either hypotonic shock or nitrogen cavitation. Using a novel two-gradient Percoll density centrifugation system, the granule-rich postnuclear supernatant was rapidly (ten minutes) and reproducibly resolved into 13 granule fractions (L1 through L8 and H1 through H5). Granule flotation and recentrifugation experiments on both continuous, self-generated and multiple-step gradients using individual and mixed isolated fractions demonstrated that the banding patterns were isopycnic and nonartifactual. Isolated granules were intact based on the findings that biochemical latency of several granule enzymes was greater than 95%, and thin-sectioned electron micrographs demonstrated intact granule profiles. Biochemical analyses of the granule marker proteins MPO, beta-glucuronidase, lysozyme, and lactoferrin indicated that a number of the fractions were related to the major azurophil and specific granule populations. Lactoferrin was found in ten of 13 fractions (L1 through L8, H1 to H2), whereas MPO was found in every fraction. Consistent with these biochemical data, all fractions exhibited varying degrees of heterogeneity based on ultrastructural morphology and cytochemistry, including diaminobenzidine (DAB) reactivity for peroxidase and periodate-thiocarbohydrazide-silver proteinate (PA-TCH-SP) staining for complex glycoconjugates. A variable but significant percentage (23% to 70%) of the granules in fractions L1 through L8 and H1 and H2 showed DAB reactivity, while about 90% of the granules in fractions H3 through H5 were peroxidase positive. These results demonstrated that DAB-reactive granules spanned the entire range of granule size and density. Ultrastructural PA-TCH-SP staining of isolated granule fractions revealed patterns similar to those of granules in intact neutrophils at different stages of development. Granules from human acute promyelocytic leukemia cells (HL-60) exhibited a surprisingly low density compared with typical azurophil granules from normal, mature neutrophils. The data suggest that both functional and maturational differences contribute to granule heterogeneity, and provide a new practical and conceptual framework for further defining the phenomenon of neutrophil granule heterogeneity. 相似文献
25.
26.
Z Khalpey MH Yacoub RT Smolenski 《Annals of the Royal College of Surgeons of England》2013,95(1):9-14
Introduction
Human donor organ shortages have led surgeons and scientists to explore the use of animals as alternative organ sources. Acute thrombovascular rejection (AVR) is the main hurdle in xenotransplantation. Disparities in nucleotide metabolism in the vessels of different species may contribute significantly to the microvascular component of AVR.Methods
We evaluated the extent of nucleotide metabolism mismatch in selected organs and endothelial cells of different mammals with particular focus on the changes in activity of ecto-5’-nucleotidase (E5’N) elicited by exposure of porcine hearts or endothelial cells to human blood (ex vivo) or human plasma (in vitro).Results
E5’N activity in the rat heart was significantly higher than in other species. We noted a significant difference (p<0.001) in E5’N activity between human and pig endothelial cell lines. Initial pig aortic endothelial E5’N activity decreased in vitro after a three-hour exposure to human and porcine plasma while remaining constant in controls. Ex vivo perfusion with fresh human blood for four hours resulted in a significant decrease of E5’N activity in both wild type and transgenic pig hearts overexpressing human decay accelerating factor (p<0.001).Conclusions
This study provides evidence that mismatches in basal mammalian metabolic pathways and humoral immunity interact in a xenogeneic environment. Understanding the role of nucleotide metabolism and signalling in xenotransplantation may identify new targets for genetic modifications and may lead to the development of new therapies extending graft survival. 相似文献27.
Yoshifumi Noda MD Satoshi Goshima MD PhD Kaori Tanaka MD Shinji Osada MD PhD Hiroyuki Tomita MD PhD Akira Hara MD PhD Yukio Horikawa MD PhD Jun Takeda MD PhD Kimihiro Kajita RT Haruo Watanabe MD Hiroshi Kawada MD Nobuyuki Kawai MD Masayuki Kanematsu MD Kyongtae T. Bae MD PhD 《Journal of magnetic resonance imaging : JMRI》2016,43(3):680-687
28.
Yu Ueda PhD Satoru Takahashi MD PhD Naoki Ohno PhD Katsusuke Kyotani RT Hideaki Kawamitu MS Tosiaki Miyati PhD Nobukazu Aoyama RT Yoshiko Ueno MD PhD Kazuhiro Kitajima MD PhD Fumi Kawakami MD Tomoyuki Okuaki MS Ryuko Tsukamoto MT Emmy Yanagita MT Kazuro Sugimura MD PhD 《Journal of magnetic resonance imaging : JMRI》2016,43(1):138-148
29.
Within the broad group of Fe non-heme oxidases, our attention was focused on the catechol 1,2- and 2,3-dioxygenases, which catalyze the oxidative cleavage of aromatic rings. A large group of Fe complexes with N/O ligands, ranging from N3 to N2O2S, was developed to mimic the activity of these enzymes. The Fe complexes discussed in this work can mimic the intradiol/extradiol catechol dioxygenase reaction mechanism. Electronic effects of the substituents in the ligand affect the Lewis acidity of the Fe center, increasing the ability to activate dioxygen and enhancing the catalytic activity of the discussed biomimetic complexes. The ligand architecture, the geometric isomers of the complexes, and the substituent steric effects significantly affect the ability to bind the substrate in a monodentate and bidentate manner. The substrate binding mode determines the preferred mechanism and, consequently, the main conversion products. The preferred mechanism of action can also be affected by the solvents and their ability to form the stable complexes with the Fe center. The electrostatic interactions of micellar media, similar to SDS, also control the intradiol/extradiol mechanisms of the catechol conversion by discussed biomimetics. 相似文献
30.
Reconstruction of the facial skeleton is challenging for surgeons because of difficulties in proper shape restoration and maintenance of the proper long-term effect. ZrO2 implant application can be a solution with many advantages (e.g., osseointegration, stability, and radio-opaqueness) and lacks the disadvantages of other biomaterials (e.g., metalosis, radiotransparency, and no osseointegration) or autologous bone (e.g., morbidity, resorption, and low accuracy). We aimed to evaluate the possibility of using ZrO2 implants as a new application of this material for craniofacial bone defect reconstruction. First, osteoblast (skeleton-related cell) cytotoxicity and genotoxicity were determined in vitro by comparing ZrO2 implants and alumina particle air-abraded ZrO2 implants to the following: 1. a titanium alloy (standard material); 2. ultrahigh-molecular-weight polyethylene (a modern material used in orbital surgery); 3. a negative control (minimally cytotoxic or genotoxic agent action); 4. a positive control (maximally cytotoxic or genotoxic agent action). Next, 14 custom in vivo clinical ZrO2 implants were manufactured for post-traumatologic periorbital region reconstruction. The soft tissue position improvement in photogrammetry was recorded, and clinical follow-up was conducted at least 6 years postoperatively. All the investigated materials revealed no cytotoxicity. Alumina particle air-abraded ZrO2 implants showed genotoxicity compared to those without subjection to air abrasion ZrO2, which were not genotoxic. The 6-month and 6- to 8-year clinical results were aesthetic and stable. Skeleton reconstructions using osseointegrated, radio-opaque, personalized implants comprising ZrO2 material are the next option for craniofacial surgery. 相似文献