全文获取类型
收费全文 | 71971篇 |
免费 | 4409篇 |
国内免费 | 273篇 |
专业分类
耳鼻咽喉 | 1112篇 |
儿科学 | 2029篇 |
妇产科学 | 1335篇 |
基础医学 | 7985篇 |
口腔科学 | 1457篇 |
临床医学 | 7089篇 |
内科学 | 15024篇 |
皮肤病学 | 1115篇 |
神经病学 | 6946篇 |
特种医学 | 2496篇 |
外国民族医学 | 5篇 |
外科学 | 12480篇 |
综合类 | 856篇 |
一般理论 | 94篇 |
预防医学 | 5990篇 |
眼科学 | 1382篇 |
药学 | 4566篇 |
中国医学 | 115篇 |
肿瘤学 | 4577篇 |
出版年
2023年 | 394篇 |
2022年 | 649篇 |
2021年 | 1791篇 |
2020年 | 933篇 |
2019年 | 1559篇 |
2018年 | 1824篇 |
2017年 | 1317篇 |
2016年 | 1343篇 |
2015年 | 1484篇 |
2014年 | 2281篇 |
2013年 | 3213篇 |
2012年 | 4876篇 |
2011年 | 5074篇 |
2010年 | 2788篇 |
2009年 | 2461篇 |
2008年 | 4482篇 |
2007年 | 4740篇 |
2006年 | 4593篇 |
2005年 | 4579篇 |
2004年 | 4306篇 |
2003年 | 3968篇 |
2002年 | 3688篇 |
2001年 | 580篇 |
2000年 | 507篇 |
1999年 | 650篇 |
1998年 | 748篇 |
1997年 | 670篇 |
1996年 | 594篇 |
1995年 | 526篇 |
1994年 | 511篇 |
1993年 | 431篇 |
1992年 | 392篇 |
1991年 | 381篇 |
1990年 | 315篇 |
1989年 | 295篇 |
1988年 | 303篇 |
1987年 | 279篇 |
1986年 | 293篇 |
1985年 | 380篇 |
1984年 | 451篇 |
1983年 | 377篇 |
1982年 | 540篇 |
1981年 | 501篇 |
1980年 | 461篇 |
1979年 | 218篇 |
1978年 | 286篇 |
1977年 | 271篇 |
1976年 | 215篇 |
1975年 | 227篇 |
1973年 | 190篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
A 37-year-old male with history of alcohol abuse presented to us with nausea, vomiting, and abdominal pain with ascites. He was diagnosed with alcoholic liver disease with coagulopathy and pancreatitis. During hospitalization, the patient developed intra-abdominal hemorrhage. He was treated with platelets, packed red blood cells and fresh frozen plasma without any improvement. Following this he was treated with activated recombinant factor VII (90 microg/kg), which resulted in normalization of the prothrombin time and the activated partial thromboplastin time and stabilization of hematocrit within a few hours. We review the current literature on the approved and off-label use of activated recombinant factor VII. 相似文献
22.
Harold C. Lyon Jr. James C. Healy James R. Bell Joseph F. O'Donnell Edward K. Shultz Robert S. Wigton Frank Hirai J. Robert Beck 《Journal of medical systems》1991,15(2):117-132
Richard E. Clark in his widely published comprehensive studies and meta-analyses of the literature on computer assisted instruction (CAI) has decried the lack of carefully controlled research, challenging almost every study which shows the computer-based intervention to result in significant post-test proficiency gains over a non-computer-based intervention. We report on a randomized study in a medical school setting where the usual confounders found by Clark to plague most research, were carefully controlled. PlanAlyzer is a microcomputer-based, self-paced, case-based, event-driven system for medical education which was developed and used in carefully controlled trials in a second year medical school curriculum to test the hypothesis that students with access to the interactive programs could integrate their didactic knowledge more effectively and/or efficiently than with access only to traditional textual “nonintelligent” materials. PlanAlyzer presents cases, elicits and critiques a student's approach to the diagnosis of two common medical disorders: anemias and chest pain. PlanAlyzer uses text, hypertext, images and critiquing theory. Students were randomized, one half becoming the experimental group who received the interactive PlanAlyzer cases in anemia, the other half becoming the controls who received the exact same content material in a text format. Later in each year there was a crossover, the controls becoming the experimentals for a similar intervention with the cardiology PlanAlyzer cases. Preliminary results at the end of the first two full trials shows that the programs have achieved most of the proposed instructional objectives, plus some significant efficiency and economy gains. 96 faculty hours of classroom time were saved by using PlanAlyzer in their place, while maintaining high student achievement. In terms of student proficiency and efficiency, the 328 students in the trials over two years were able to accomplish the project's instructional objectives, and the experimentals accomplished this in 43% less time than the controls, achieving the same level of mastery. However, in spite of these significant efficiency findings, there have been no significant proficiency differences (as measured by current factual and higher order multiple choice post-tests) between the experimental and control groups. Very careful controls were used to avoid what Clark has found to be the most common confounders of CAI research. Accordingly, this research proved Clark's rival hypothesis, that the computer, in itself, does not appear to contribute to proficiency gains, at least as measured by our limited post-testing. Clark's position is that the computer is primarily a vehicle—as is either a pill or a hypodermic needle for delivering a drug. The hypodermic needle can deliver the drug more efficiently than can the pill, (as can the computer deliver the subject matter content more efficiently, as our research indicates), but the same content is delivered. At the same time, we proved our own hypothesis, as far as efficiency gains resulting from the computer are concerned. However, going beyond Clark's research, we may be teaching processes both more effectively and efficiently with the computer (experience in problem-solving or clinical reasoning and pattern recognition) which our current post-tests do not adequately measure. Our on-going research suggests additional inquiry in several areas: better evaluation instruments to measure the clinical reasoning skills PlanAlyzer was designed to teach; the addition of more advanced cases to determine if this might transform efficiency gains of the computer group into proficiency gains; the addition of enhanced graphic decision support tools and other pedagogical enhancements including cognitive feedback to strengthen PlanAlyzer's power to teach complex concepts of medical decision-making. 相似文献
23.
Skoug John W. Borin Marie T. Fleishaker Joseph C. Cooper Anne M. 《Pharmaceutical research》1991,8(12):1482-1488
The mechanism of release from sustained-release adinazolam mesylate tablets was assessed by the Higuchi equation and by analysis of drug release profiles through 60% released using the Peppas equation. Computed values of the diffusional exponent, n, ranged from 0.59 to 0.66. Values of n in this range are consistent with a mixed mechanism of release, with diffusion of drug through the hydrated polymer matrix and relaxation of this matrix being the principal processes controlling release. The rate of in vitro drug release was increased for half tablets relative to whole tablets and is attributed to an increase in the surface to volume ratio of half tablets of about 16%. This increase in surface-to-volume ratio of half tablets was reflected by an increase in the constant, k, from the Peppas equation of 20–23% and by an increase in the slope of Higuchi plots of 12–18% for four lots of tablets. In vivo/in vitro relationships from two bioavailability studies were thoroughly evaluated. Using either a linear or a quadratic relationship, an in vivo/in vitro correlation exists for sustained-release adinazolam mesylate tablets. 相似文献
24.
25.
26.
27.
Ophira Salomon Joseph Moisseiev Tamara Vilganski Rima Dardik Shimon Kurtz Eva Shpringer David M Steinberg Nurit Rosenberg 《Blood coagulation & fibrinolysis》2006,17(6):485-488
To determine whether polymorphisms of platelet surface glycoprotein associated with arterial thrombosis are risk factors for branch retinal vein occlusion. A case-control study in which 69 patients with branch retinal vein occlusion and 147 controls who attended the eye clinic for nonvascular complications participated. DNA was extracted from whole blood and analyzed for genotyping of platelet glycoprotein polymorphisms by polymerase chain reactions and specific restricted enzymes. No relationship was found between the four platelet glycoprotein polymorphisms i.e. GPIa C807T, VNTR and Kozak of glycoprotein Ibalpha, the HPA-1 of glycoprotein IIIa and the occurrence of branch retinal vein occlusion. The HPA-2 polymorphism was found in 18 out 60 (30%) patients with branch retinal vein occlusion in comparison with 27 out 142 (19%) of controls, with an estimated odds ratio of 1.8 (95% confidence interval, 0.91-3.65). The four platelet glycoprotein polymorphisms are not risk factors for branch retinal vein occlusion and therefore it seems unnecessary to screen those patients for it. A larger study is required, however, to determine whether HPA-2 is a novel risk factor for branch retinal vein occlusion. 相似文献
28.
29.
30.
Further evidence of dopamine transporter dysregulation in ADHD: a controlled PET imaging study using altropane. 总被引:4,自引:0,他引:4
Thomas J Spencer Joseph Biederman Bertha K Madras Darin D Dougherty Ali A Bonab Elijahu Livni Peter C Meltzer Jessica Martin Scott Rauch Alan J Fischman 《Neuropsychopharmacology》2007,62(9):1059-1061
BACKGROUND: The dopamine transporter (DAT) is known to be a key regulator of dopamine, and recent studies of genetics, treatment, and imaging have highlighted the role of DAT in attention-deficit/hyperactivity disorder (ADHD). The findings of in vivo neuroimaging of DAT in ADHD have been somewhat discrepant, however. METHOD: Dopamine transporter binding was measured using a highly selective ligand (C-11 altropane) and positron emission tomography (PET). The sample consisted of 47 well-characterized, treatment-na?ve, nonsmoking, non-comorbid adults with and without ADHD. Additionally, control subjects had few symptoms of ADHD. RESULTS: Results showed significantly increased DAT binding in the right caudate in adults with ADHD compared with matched control subjects without this disorder. CONCLUSIONS: These results confirm abnormal DAT binding in the striatum of adults with ADHD and provide further support that dysregulation of DAT may be an important component of the pathophysiology of ADHD. 相似文献