全文获取类型
收费全文 | 38114篇 |
免费 | 2463篇 |
国内免费 | 106篇 |
专业分类
耳鼻咽喉 | 295篇 |
儿科学 | 1263篇 |
妇产科学 | 1035篇 |
基础医学 | 4308篇 |
口腔科学 | 603篇 |
临床医学 | 6632篇 |
内科学 | 6712篇 |
皮肤病学 | 403篇 |
神经病学 | 3660篇 |
特种医学 | 784篇 |
外国民族医学 | 1篇 |
外科学 | 3824篇 |
综合类 | 404篇 |
现状与发展 | 1篇 |
一般理论 | 66篇 |
预防医学 | 5248篇 |
眼科学 | 495篇 |
药学 | 2282篇 |
中国医学 | 35篇 |
肿瘤学 | 2632篇 |
出版年
2023年 | 212篇 |
2022年 | 371篇 |
2021年 | 695篇 |
2020年 | 486篇 |
2019年 | 757篇 |
2018年 | 927篇 |
2017年 | 638篇 |
2016年 | 717篇 |
2015年 | 762篇 |
2014年 | 1139篇 |
2013年 | 1811篇 |
2012年 | 2552篇 |
2011年 | 2721篇 |
2010年 | 1450篇 |
2009年 | 1272篇 |
2008年 | 2473篇 |
2007年 | 2660篇 |
2006年 | 2478篇 |
2005年 | 2474篇 |
2004年 | 2300篇 |
2003年 | 2201篇 |
2002年 | 2113篇 |
2001年 | 454篇 |
2000年 | 400篇 |
1999年 | 485篇 |
1998年 | 450篇 |
1997年 | 382篇 |
1996年 | 314篇 |
1995年 | 339篇 |
1994年 | 276篇 |
1993年 | 256篇 |
1992年 | 315篇 |
1991年 | 322篇 |
1990年 | 308篇 |
1989年 | 274篇 |
1988年 | 256篇 |
1987年 | 243篇 |
1986年 | 215篇 |
1985年 | 228篇 |
1984年 | 214篇 |
1983年 | 214篇 |
1982年 | 205篇 |
1981年 | 200篇 |
1980年 | 171篇 |
1979年 | 126篇 |
1978年 | 141篇 |
1977年 | 100篇 |
1976年 | 67篇 |
1975年 | 58篇 |
1974年 | 66篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Nonsteroidal anti-inflammatory drug use and increased risk for peptic ulcer disease in elderly persons 总被引:25,自引:0,他引:25
M R Griffin J M Piper J R Daugherty M Snowden W A Ray 《Annals of internal medicine》1991,114(4):257-263
OBJECTIVE: To evaluate the relative risk for peptic ulcer disease that is associated with the use of nonaspirin nonsteroidal anti-inflammatory drugs. DESIGN: Nested case-control study. SETTING: Tennessee Medicaid program. PARTICIPANTS: Medicaid enrollees 65 years of age or older were included in the study. The 1415 case patients had been hospitalized for confirmed peptic ulcer disease at some point from 1984 through 1986. The 7063 control persons represented a stratified random sample of other Medicaid enrollees. MEASUREMENTS AND MAIN RESULTS: The estimated relative risk for the development of peptic ulcer disease among current users of nonaspirin nonsteroidal anti-inflammatory drugs, compared with that among nonusers, was 4.1 (95% CI, 3.5 to 4.7). For current users, the risk increased with increasing dose, from a relative risk of 2.8 (CI, 1.8 to 4.3) for the lowest to a relative risk of 8.0 (CI, 4.4 to 14.8) for the highest dose category. The risk was greatest in the first month of use (relative risk, 7.2; CI, 4.9 to 10.5). If the association is fully causal, 29% of peptic ulcers in the study sample resulted from the use of these drugs, and the excess risk associated with such use was 17.4 hospitalizations for ulcer disease per 1000 person-years of exposure. CONCLUSIONS: These data support other findings indicating that a clinically significant risk for serious ulcer disease is associated with the use of nonaspirin nonsteroidal anti-inflammatory drugs. The data show that this risk increases with dose and recency of use and that use of these drugs may be responsible for a large proportion of peptic ulcer disease among elderly persons. 相似文献
102.
This is the third report of a metabolic study on 56 long-term users (24 for 2-5 yr; 32 for over 5 yr) of the injectable contraceptive norethisterone enanthate (Net-En) and deals with the effects on the blood levels of lipoprotein fractions. There was no significant difference between this group and a group of 30 non-users in serum concentrations of triglycerides, total cholesterol, low density and very low density lipoproteins. There was a significant reduction in mean high density lipoprotein levels between the controls and the user groups (16% for the intermediate duration and 12% for the longer duration). Age, ethnic group, body-mass index and a close family history of cardiovascular disease were taken into account, as were various lifestyle factors: diet, exercise, alcohol consumption and smoking. In a smaller group, levels of apoproteins A and B were also assayed. There was a significant reduction in apoprotein A between controls and all users, but the significance was lost on adjusting for confounding variables. Consideration was given to the ratio of total cholesterol to high density lipoprotein cholesterol as an index of coronary risk. There were no significant differences in the total cholesterol:HDL-C ratio between controls and user groups. There was a significant interaction with ethnic group (Caucasian or Afro-Caribbean) in the response to duration of use. 相似文献
103.
104.
Linda R White Lars Jacob Stovner Maurice B Vincent Ole Petter Løbben Yara D Fragoso Kristian S Bjerve Ottar Sjaastad 《Cephalalgia : an international journal of headache》1992,12(2):107-110
Our group has previously reported significant changes in the incorporation of precursors into glycerophospholipids, particularly phosphatidylserine, in polymorphonuclear cells obtained from the peripheral blood of cluster headache patients, when compared with controls. The potential of these results led to further work using both the previous methodology and a modified isolation technique to obtain polymorphonuclear cells in as pure a state as possible. Neither the new results obtained using the original technique, nor the results with high purity polymorphonuclear cells from controls and cluster headache patients, confirm the marked changes in precursor uptake into glycerophospholipids originally reported. 相似文献
105.
Anucha Apisarnthanarak Pilaipan Puthavathana Linda M Mundy 《Infection control and hospital epidemiology》2007,28(4):479-482
We conducted a cohort study to identify the risks and outcomes of influenza A (H3N2) pneumonia. Of the 145 patients studied, 10 (7%) had influenza A pneumonia. Logistic regression identified multiple comorbidities (P<.001) and diarrhea at the initial presentation (P=.001) as associated risks. Infection with influenza A (P=.01) and receipt of inadequate antimicrobial therapy (P=.005) were predictors of mortality. 相似文献
106.
107.
108.
109.
Adopting an information management approach to the design and implementation of information systems.
As the NHS adopts an information management approach to coordinated handling of total information resources, methods of systems analysis and design require assessment to ensure that they are appropriate. Mandatory use of Structured Systems Analysis and Design Methodology (SSADM) may be encouraging a damagingly narrow view of information systems. Research is described in which an holistic view of information systems is applied, allowing the needs of information users to play a stronger role in determining how information will be supplied to them. The techniques may also assist the training activities associated with implementing new systems. 相似文献
110.
Linda Laatsch Thomas Jobe Jerry Sychra Qing Lin Michael Blend 《Brain injury : [BI]》1997,11(12):851-864
Three patients,with known brain injury and neuropsychological impairments, are followed through an individualized cognitive rehabilitation programme and post discharge from the treatment programme. Single Photon Emission Computed Tomography (SPECT) of the brain was employed to evaluate resting relative cerebral blood flow (rCBF) during the process of recovery from brain injury. All patients experienced significant improvements on measures of neuropsychological functioning and improvements in rCBF during this longitudinal study. The specific changes in rCBF appear to be related to the location of the patient s brain injury and strategies particular to cognitive rehabilitation therapy. Continued improvements in rCBF, functional abilities, and cognitive skills were documented in these three cases up to 45 months post brain injury. 相似文献