全文获取类型
收费全文 | 3587篇 |
免费 | 264篇 |
国内免费 | 6篇 |
专业分类
耳鼻咽喉 | 61篇 |
儿科学 | 171篇 |
妇产科学 | 66篇 |
基础医学 | 409篇 |
口腔科学 | 105篇 |
临床医学 | 352篇 |
内科学 | 556篇 |
皮肤病学 | 62篇 |
神经病学 | 558篇 |
特种医学 | 303篇 |
外科学 | 538篇 |
综合类 | 55篇 |
一般理论 | 2篇 |
预防医学 | 219篇 |
眼科学 | 39篇 |
药学 | 176篇 |
1篇 | |
中国医学 | 10篇 |
肿瘤学 | 174篇 |
出版年
2021年 | 60篇 |
2020年 | 37篇 |
2019年 | 55篇 |
2018年 | 55篇 |
2017年 | 59篇 |
2016年 | 58篇 |
2015年 | 68篇 |
2014年 | 97篇 |
2013年 | 101篇 |
2012年 | 144篇 |
2011年 | 155篇 |
2010年 | 114篇 |
2009年 | 98篇 |
2008年 | 131篇 |
2007年 | 129篇 |
2006年 | 153篇 |
2005年 | 130篇 |
2004年 | 124篇 |
2003年 | 113篇 |
2002年 | 98篇 |
2001年 | 109篇 |
2000年 | 108篇 |
1999年 | 85篇 |
1998年 | 71篇 |
1997年 | 64篇 |
1996年 | 68篇 |
1995年 | 75篇 |
1994年 | 66篇 |
1993年 | 62篇 |
1992年 | 71篇 |
1991年 | 59篇 |
1990年 | 70篇 |
1989年 | 83篇 |
1988年 | 73篇 |
1987年 | 90篇 |
1986年 | 70篇 |
1985年 | 64篇 |
1984年 | 55篇 |
1983年 | 42篇 |
1982年 | 37篇 |
1981年 | 34篇 |
1980年 | 31篇 |
1979年 | 36篇 |
1978年 | 39篇 |
1977年 | 31篇 |
1976年 | 27篇 |
1975年 | 28篇 |
1973年 | 16篇 |
1970年 | 16篇 |
1968年 | 16篇 |
排序方式: 共有3857条查询结果,搜索用时 31 毫秒
61.
Trimetrexate for the treatment of Pneumocystis carinii pneumonia in patients with the acquired immunodeficiency syndrome 总被引:12,自引:0,他引:12
C J Allegra B A Chabner C U Tuazon D Ogata-Arakaki B Baird J C Drake J T Simmons E E Lack J H Shelhamer F Balis 《The New England journal of medicine》1987,317(16):978-985
Preclinical studies have demonstrated that trimetrexate is a potent inhibitor of dihydrofolate reductase from Pneumocystis carinii. On the basis of this evidence, this lipid-soluble antifolate was used as an antipneumocystis agent in 49 patients with the acquired immunodeficiency syndrome (AIDS) and pneumocystis pneumonia. Simultaneous treatment with the reduced folate leucovorin was used as a specific antidote to protect host tissues from the toxic effects of the antifolate without affecting the antipneumocystis action of trimetrexate. Patients were assigned to three groups and treated for 21 days: in Group I, trimetrexate with leucovorin was used as salvage therapy in patients in whom standard treatments (both pentamidine isethionate and trimethoprim-sulfamethoxazole) could not be tolerated or had failed (16 patients); in Group II, trimetrexate with leucovorin was used as initial therapy in patients with a history of sulfonamide inefficacy or intolerance (16 patients); and in Group III, trimetrexate with leucovorin plus sulfadiazine was used as initial therapy (17 patients). The response and survival rates were, respectively, 69 percent and 69 percent in Group I; 63 percent and 88 percent in Group II; and 71 percent and 77 percent in Group III. Trimetrexate therapy had minimal toxicity; transient neutropenia or thrombocytopenia occurred in 12 patients and mild elevation of serum aminotransferases in 4. We conclude that the combination of trimetrexate and leucovorin is safe and effective for the initial treatment of pneumocystis pneumonia in patients with AIDS and for the treatment of patients with intolerance or lack of response to standard therapies. 相似文献
62.
Patrik Pipkorn Candy Costantini Curt Reynolds Michael Wall Margaret Drake Alvin Sanico David Proud Alkis Togias 《Annals of allergy, asthma & immunology》2008,101(1):82-89
BACKGROUND: Olopatadine, an antihistamine used in allergic conjunctivitis, is under development as a nasal preparation for the treatment of allergic rhinitis. OBJECTIVES: To evaluate the efficacy of olopatadine in suppressing symptoms and biomarkers of the immediate reaction induced by nasal allergen provocation and to compare olopatadine with azelastine in the same model. METHODS: The study was approved by the Johns Hopkins University institutional review board, and all subjects gave written consent. We studied 20 asymptomatic subjects with seasonal allergic rhinitis. The study had 2 randomized, double-blind, placebo-controlled, crossover phases that evaluated 2 concentrations of olopatadine, 0.1% and 0.2%. In a third exploratory phase, olopatadine, 0.1%, was compared with topical azelastine, 0.1%, in a patient-masked design. Efficacy variables were the allergen-induced sneezes, other clinical symptoms, and the levels of histamine, tryptase, albumin, lysozyme, and cysteinyl-leukotrienes (third study only) in nasal lavage fluids. RESULTS: Both concentrations of olopatadine produced significant inhibition of all nasal symptoms, compared with placebo. Olopatadine, 0.1%, inhibited lysozyme levels, but olopatadine, 0.2%, inhibited histamine, albumin, and lysozyme. The effects of olopatadine, 0.1%, were comparable to those of azelastine, 0.1%. CONCLUSIONS: Olopatadine, at 0.1% and 0.2% concentrations, was effective in suppressing allergen-induced nasal symptoms. At 0.2%, olopatadine provided evidence suggestive of inhibition of mast cell degranulation. 相似文献
63.
Thrombin enhancement of interleukin-1 and tumor necrosis factor-alpha induced polymorphonuclear leukocyte migration. 总被引:3,自引:0,他引:3
W T Drake N N Lopes J W Fenton A C Issekutz 《Laboratory investigation; a journal of technical methods and pathology》1992,67(5):617-627
BACKGROUND: Cytokines such as IL-1 alpha and tumor necrosis factor-alpha (TNF-alpha) activate vascular endothelium to express leukocyte adhesion molecules that promote polymorphonuclear leukocyte (PMNL) migration and to synthesize tissue factor, thus making the endothelium a procoagulant surface. alpha-Thrombin, generated during coagulation, also activates endothelial cells. Since all these processes are likely involved in inflammation, the effect of alpha-thrombin on PMNL interaction with cytokine activated endothelium was investigated. EXPERIMENTAL DESIGN: Human umbilical vein endothelium was grown on polycarbonate filters to investigate the effects interleukin-1 alpha (IL-1 alpha), TNF-alpha, and alpha-thrombin on PMNL transendothelial migration quantitated with 51Cr-labeled PMNL, and on endothelial monolayer permeability, quantitated with 125I-labeled albumin (HSA). To evaluate the expression of endothelial-leukocyte adhesion molecules, enzyme-linked immunosorbent assay was performed on human umbilical vein endothelium monolayers. The effect of thrombin on PMNL accumulation and plasma exudation in inflammation was studied in a rabbit dermal model, using 51Cr-labeled blood leukocytes and [125I]HSA respectively. RESULTS: On resting human umbilical vein endothelium, alpha-thrombin induced a transient increase (2.5- to 4-fold) in monolayer permeability lasting 30 minutes. Slight but significant transendothelial migration of 51Cr-labeled PMNL was induced by alpha-thrombin (7.4 +/- 0.6% of cells added, unstimulated = 1.9 +/- 0.4%), although this response was less than that induced by f-norLeu-Leu-Phe (17%), IL-1 alpha (29%) or TNF-alpha (21%). alpha-Thrombin enhanced the initial rate of IL-1, TNF-alpha and f-norLeu-Leu-Phe induced PMNL transendothelial migration in an additive or supradditive manner (e.g., with IL-1 alpha+alpha-thrombin, migration was 58% greater than additive at 15 to 30 minutes, p < 0.001). Catalytically inactivated alpha-thrombin, D-phenylalanyl-L-propyl-L-arginine chloromethyl ketone and diisopropyl-fluorophosphate alpha-thrombin, did not enhance migration or permeability. In dermal inflammation in rabbits, alpha-thrombin (10 units/site) induced an increase in plasma protein exudation, with only a mild infiltration of PMNL. However, alpha-thrombin synergistically enhanced the PMNL infiltration induced by IL-1 alpha, TNF-alpha, but not that induced by zymosan activated plasma (C5a) or IL-8 (neutrophil-activating peptide-1). These measurements were confirmed histologically. Investigations into the mechanisms of the enhancement of PMNL migration indicated that individually vascular permeability changes, prostaglandins, platelet activating factor, and P-selectin expression did not account for the observation effects. CONCLUSIONS: Alpha-thrombin may have a role in synergistically enhancing PMNL infiltration at sites of inflammation, in part via enzymatic action on the cytokine activated endothelium. The mechanisms involved in this effect are likely a complex interaction. 相似文献
64.
C J Allegra B A Chabner P W Sholar C Bagley J C Drake M E Lippman 《NCI monographs : a publication of the National Cancer Institute》1987,(5):199-202
The active metabolite of FUra, 5-fluorodeoxyuridine monophosphate (5-FdUMP), requires the presence of reduced folates to form a covalent ternary complex with the target enzyme thymidylate synthase (TS). In vitro and in vivo studies have demonstrated a potentiation of the cytotoxic effects of FUra when combined with the reduced folate, leucovorin. We have applied this concept to the treatment of metastatic breast cancer in a phase II trial, as recent clinical studies on patients with colorectal carcinoma have suggested an enhanced efficacy for the combination of FUra plus leucovorin. Patients entered on the present study are undergoing treatment with a 5-day daily regimen of leucovorin (500 mg/m2, iv) followed by FUra (375 mg/m2, iv). Toxicity and response data are currently being collected on patients who have failed "standard" combination regimens that included FUra. In patients with accessible tumor, serial biopsies are being obtained during treatment with the combination of FUra and leucovorin and during therapy with FUra alone to assess the degree of 5-FdUMP binding to the target enzyme, TS, in the presence and absence of exogenously administered leucovorin. Preliminary results from the biochemical studies suggest an enhanced saturation of TS by the fluorinated pyrimidine when administered with leucovorin. 相似文献
65.
66.
67.
68.
Frederick Thurston Drake Melanie L. Lyden Jennifer H. Kuo Wen T. Shen Lilah F. Morris-Wiseman Sally E. Carty Tracy S. Wang 《Surgery》2021,169(3):488-495
BackgroundApproximately 80% of general surgery residents undertake some form of fellowship training. Our objective was to characterize goals and burdens of the interview process among applicants to Comprehensive Endocrine Surgery Fellowship programs.MethodsParticipants included trainees from 2013 to 2019. Results for ranking questions are presented as a mean rank reported out of the total number of selections.ResultsResponse rate was 54% (n = 75). The most important goal for interviews was meeting the faculty (mean rank 2.4/9), followed by “behind the scenes information” and “make a good impression” (mean rank 3.6 and 3.7, respectively). The most substantial burden for the applicant was expense (mean rank 2.1/7), followed by time away from residency (mean rank 3.1/7). The economic burden of 51% of the applicants was $2,500 to $7,500. Geographic location and expense were the top 2 reasons applicants declined offers of interviews. Despite the process, 76% of respondents indicated that no improvements to the interview process are necessary. Alternative strategies such as videoconferencing or centralized interviews received little support (<10%).ConclusionDespite identifying several burdens, survey respondents believed that in-person interviews are an integral component of the fellowship application process. Indeed, 70% of applicants do not have a first-choice program before interviews, and meeting the faculty is ranked as the greatest priority goal. Our data illustrate the importance of individual specialties evaluating and optimizing their own processes for fellowship interviews. 相似文献
69.
70.