全文获取类型
收费全文 | 49647篇 |
免费 | 3201篇 |
国内免费 | 155篇 |
专业分类
耳鼻咽喉 | 653篇 |
儿科学 | 1422篇 |
妇产科学 | 856篇 |
基础医学 | 5895篇 |
口腔科学 | 803篇 |
临床医学 | 5051篇 |
内科学 | 10696篇 |
皮肤病学 | 860篇 |
神经病学 | 4633篇 |
特种医学 | 1997篇 |
外国民族医学 | 1篇 |
外科学 | 8710篇 |
综合类 | 474篇 |
一般理论 | 48篇 |
预防医学 | 3126篇 |
眼科学 | 807篇 |
药学 | 3044篇 |
中国医学 | 45篇 |
肿瘤学 | 3882篇 |
出版年
2023年 | 245篇 |
2022年 | 414篇 |
2021年 | 1082篇 |
2020年 | 625篇 |
2019年 | 1099篇 |
2018年 | 1304篇 |
2017年 | 952篇 |
2016年 | 990篇 |
2015年 | 1171篇 |
2014年 | 1820篇 |
2013年 | 2319篇 |
2012年 | 3742篇 |
2011年 | 3895篇 |
2010年 | 2179篇 |
2009年 | 1863篇 |
2008年 | 3406篇 |
2007年 | 3581篇 |
2006年 | 3562篇 |
2005年 | 3465篇 |
2004年 | 3333篇 |
2003年 | 3100篇 |
2002年 | 2848篇 |
2001年 | 378篇 |
2000年 | 263篇 |
1999年 | 398篇 |
1998年 | 567篇 |
1997年 | 456篇 |
1996年 | 349篇 |
1995年 | 347篇 |
1994年 | 327篇 |
1993年 | 268篇 |
1992年 | 209篇 |
1991年 | 197篇 |
1990年 | 174篇 |
1989年 | 160篇 |
1988年 | 161篇 |
1987年 | 144篇 |
1986年 | 138篇 |
1985年 | 142篇 |
1984年 | 181篇 |
1983年 | 180篇 |
1982年 | 202篇 |
1981年 | 176篇 |
1980年 | 124篇 |
1979年 | 83篇 |
1978年 | 77篇 |
1977年 | 69篇 |
1976年 | 43篇 |
1975年 | 30篇 |
1974年 | 43篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
122.
The authors describe their preliminary experience with the use of superparamagnetic magnetic resonance (MR) imaging contrast media for suppression of signal from flowing blood. The goal of this work was to determine if a superparamagnetic contrast agent could successfully eliminate blood signal during cardiac-gated MR imaging, thereby eliminating or reducing flow artifacts associated with the complex and variable hemodynamics within the heart chambers. Imaging and data analysis were performed in 17 dogs subjected to experimental myocardial infarction as part of a parallel project. Six doses (0.2, 1, 2, 3.5, 4, 5, and 10 mg/kg) of AMI-25, an experimental contrast agent, were used in the study. Spin-echo imaging was performed immediately before and every 5 minutes (for an average of 25 minutes) after bolus injection of the contrast agent. Variations in the image signal-to-noise ratio relative to a baseline (before injection of contrast agent) image were assessed as a function of dose and time. Preliminary results suggest that a considerable reduction in blood flow artifacts and, hence, increases in image signal-tonoise ratio can be achieved at doses greater than or equal to 3.5 mg/kg, for approximately 20 minutes after injection. Doses equal to or less than 2 mg/kg and images obtained more than 20 minutes after injection (regardless of dose) did not reliably show hemodynamic artifact suppression. 相似文献
123.
Abdulmassih S. Iskandrian Jeffrey Johnson Tung T. Le Valerie Wasserleben Virginia Cave Jaekyeong Heo 《Journal of nuclear cardiology》1994,1(2):144-149
Background
This study compared the prognostic value of exercise single-photon emission computed tomographic (SPECT) thallium imaging with that of treadmill exercise score in medically treated patients with coronary artery disease (CAD) 相似文献124.
Is colonoscopic screening appropriate in asymptomatic patients with family history of colon cancer? 总被引:1,自引:0,他引:1
Martin A. Luchtefeld M.D. Dale Syverson M.D. Mark Solfelt M.D. John M. MacKeigan M.D. Randall Krystosek M.D. James Waller M.D. Jeffrey W. Milsom M.D. 《Diseases of the colon and rectum》1991,34(9):763-768
Colonoscopy has been advocated by some investigators as the most appropriate means of screening asymptomatic patients with a positive family history of colorectal cancer. However, results of such screening have been widely disparate. The purpose of this study was to evaluate the yield of colonoscopy in a cohort of completely asymptomatic individuals with one or two first-degree relatives with a history of colorectal cancer and to compare this yield with that of colonoscopy in a group of patients with apparent anal bleeding. Patients with possible genetic disorders, such as familial polyposis, were excluded. A total of 160 asymptomatic patients and a comparison group of 137 patients with nonacute anorectal bleeding underwent colonoscopy. Colonoscopy was completed in 143 of the 160 study patients (89 percent) and in all of the comparison patients and did not result in any complications. Twenty-two adenomas were found in 17 study patients (10.6 percent); 16 of the 22 adenomas were less than 1 cm in size. In the comparison group, eight adenomas were identified (5.8 percent of patients). No cancers were identified. The difference in polyp frequency between groups was not significant. The relatively low yield of colorectal neoplasms discovered at colonoscopy in this study may in part be due to the small sample size or to the strict criteria used to define these asymptomatic patients but does not lend strong support to the notion that colonoscopy is an appropriate first step in screening the asymptomatic patient with one or two first-degree relatives with colon cancer. 相似文献
125.
126.
This study describes a method for determining the number of radiographic rooms devoted to emergency radiology that would be
required to keep mean patient waiting time at a desired level.
A desired mean waiting time for patients must be determined. In our setting, a mean waiting time of 8 minutes resulted in
few complaints. The waiting time then sets the required utilization rate of available capacity. Daily and hourly volume and
variability in volume of examinations were measured over a 3-month period. This represents the demand. The needed number of
rooms is determined by comparing demand with effective available capacity for different numbers of rooms.
To maintain an 8-minute mean waiting time, 50% utilization of capacity is required. Mean demand on Sundays is 176 examinations.
Five rooms are required, since this gives a 180-examination effective capacity.
Using waiting time as the primary decision criterion for making capacity decisions in emergency radiology has several advantages:
the method is easy to use, volume variability is taken into account, and the focus is on service to patients. 相似文献
127.
Josef Parvizi Jeffrey Joseph Daniel Z Press Jeremy D Schmahmann 《Movement disorders》2007,22(6):798-803
In the cerebellar type of multiple system atrophy (MSA-C), the burden of pathological changes involves the cerebellum and its associated brainstem structures in the basis pontis and the inferior olivary nucleus, and as a result, the clinical phenotype is dominated early on by the cerebellar dysfunction. We report our clinical and post mortem findings in a patient with MSA-C who exhibited pathological laughter in the absence of any congruent changes of mood. A review of the clinical notes of 27 other patients with MSA-C revealed a problem with pathological laughter, or crying, or both in 9 more patients. Our finding of about 36% occurrence suggests that the problem of dysregulation of emotional expression is more prevalent in MSA-C than the paucity of reports in the literature suggests. Our findings are consistent with the view that the cerebellum and its interconnected structures may be involved in the regulation of emotional expression. 相似文献
128.
Jeffrey R Suchard Marc A Suchard Jennifer L Steinfeldt 《European journal of emergency medicine》2004,11(4):193-197
OBJECTIVE: To determine how knowledgeable physicians are regarding the toxic effects and drug interactions of herbal remedies. METHODS: An anonymous voluntary demographic survey and 16-question, multiple-choice quiz was distributed at educational meetings of emergency medicine and internal medicine physicians. The primary outcome measures were to determine whether significant associations existed between quiz scores and the amount of clinical experience, or between quiz scores and self-assessed familiarity with the topic of herbal toxicities and adverse herb-drug interactions. RESULTS: A total of 142 surveys and quizzes were completed by 59 attending physicians, 57 resident physicians, and 26 medical students. The mean subject score on the quiz was only slightly higher than would have occurred from random guessing. Neither the amount of the subjects' clinical experience, nor their self-assessed familiarity with herbal toxicities and drug interactions correlated significantly with the score on the quiz. CONCLUSION: The physicians and medical students surveyed had little training in herbal toxicities and drug interactions. They generally rated their familiarity with these topics as 'poor', and their scores on the quiz bore out this assessment as correct. Educational efforts might improve physician knowledge of the adverse effects of herbal remedies. 相似文献
129.
130.
Michael S. Runyon MD Peter B. Richman MD Jeffrey A. Kline MD 《Academic emergency medicine》2007,14(1):53-57
Background Several clinical decision rules (CDRs) have been validated for pretest probability assessment of pulmonary embolism (PE), but the authors are unaware of any data quantifying and characterizing their use in emergency departments. Objectives To characterize clinicians' knowledge of and attitudes toward two commonly used CDRs for PE. Methods By using a modified Delphi approach, the authors developed a two‐page paper survey including 15 multiple‐choice questions. The questions were designed to determine the respondents' familiarity, frequency of use, and comprehension of the Canadian and Charlotte rules. The survey also queried the frequency of use of unstructured (gestalt) pretest probability assessment and reasons why physicians choose not to use decision rules. The surveys were sent to physicians, physician assistants, and medical students at 32 academic and community hospitals in the United States and the United Kingdom. Results Respondents included 555 clinicians; 443 (80%) work in academic practice, and 112 (20%) are community based. Significantly more academic practitioners (73%) than community practitioners (49%) indicated familiarity with at least one of the two decision rules. Among all respondents familiar with a rule, 50% reported using it in more than half of applicable cases. A significant number of these respondents could not correctly identify a key component of the rule (23% for the Charlotte rule and 43% for the Canadian rule). Fifty‐seven percent of all respondents indicated use of gestalt rather than a decision rule in more than half of cases. Conclusions Academic clinicians were more likely to report familiarity with either of these two specific decision rules. Only one half of all clinicians reporting familiarity with the rules use them in more than 50% of applicable cases. Spontaneous recall of the specific elements of the rules was low to moderate. Future work should consider clinical gestalt in the evaluation of patients with possible PE. 相似文献