全文获取类型
收费全文 | 5304篇 |
免费 | 431篇 |
国内免费 | 4篇 |
专业分类
耳鼻咽喉 | 49篇 |
儿科学 | 236篇 |
妇产科学 | 109篇 |
基础医学 | 724篇 |
口腔科学 | 157篇 |
临床医学 | 559篇 |
内科学 | 983篇 |
皮肤病学 | 96篇 |
神经病学 | 315篇 |
特种医学 | 158篇 |
外科学 | 836篇 |
综合类 | 365篇 |
一般理论 | 2篇 |
预防医学 | 561篇 |
眼科学 | 50篇 |
药学 | 264篇 |
1篇 | |
中国医学 | 2篇 |
肿瘤学 | 272篇 |
出版年
2022年 | 32篇 |
2021年 | 99篇 |
2020年 | 37篇 |
2019年 | 74篇 |
2018年 | 78篇 |
2017年 | 58篇 |
2016年 | 80篇 |
2015年 | 96篇 |
2014年 | 149篇 |
2013年 | 204篇 |
2012年 | 229篇 |
2011年 | 239篇 |
2010年 | 190篇 |
2009年 | 168篇 |
2008年 | 256篇 |
2007年 | 239篇 |
2006年 | 265篇 |
2005年 | 252篇 |
2004年 | 256篇 |
2003年 | 217篇 |
2002年 | 190篇 |
2001年 | 172篇 |
2000年 | 161篇 |
1999年 | 179篇 |
1998年 | 74篇 |
1997年 | 68篇 |
1996年 | 70篇 |
1995年 | 69篇 |
1994年 | 69篇 |
1993年 | 54篇 |
1992年 | 109篇 |
1991年 | 117篇 |
1990年 | 101篇 |
1989年 | 108篇 |
1988年 | 89篇 |
1987年 | 70篇 |
1986年 | 84篇 |
1985年 | 68篇 |
1984年 | 65篇 |
1983年 | 48篇 |
1982年 | 42篇 |
1981年 | 32篇 |
1980年 | 30篇 |
1979年 | 45篇 |
1978年 | 47篇 |
1977年 | 27篇 |
1976年 | 30篇 |
1974年 | 35篇 |
1973年 | 30篇 |
1971年 | 26篇 |
排序方式: 共有5739条查询结果,搜索用时 15 毫秒
31.
Three patients had documented fundus changes conforming to those of the recently described multiple evanescent white dot (MEWD) syndrome. All three patients were unilaterally affected with variously sized, soft, single, and coalescent white lesions at the level of the RPE and the deep retina. Fluorescein angiography demonstrated early staining and hyperfluorescence of the white dots and delayed staining around the optic disc. Some degree of optic disc edema could be seen in all three eyes, two of which had corresponding field defects. In all three eyes, characteristic "stippling," or granularity, of the affected macula developed rapidly and vitreal cells were observed. One eye had signs of previous perivascular inflammation. ERG studies performed on one patient indicated a reduction in the a-wave and depression of the ERP, findings that correlated with the clinical observations of RPE affectation. 相似文献
32.
Physiological and psychological variables related to functional status in chronic obstructive pulmonary disease. 总被引:3,自引:0,他引:3
The relationship of selected physiological and psychological variables to functional status in patients with chronic obstructive pulmonary disease (COPD) was investigated in this study. There has been limited exploration of the relative contribution of these variables to the performance of activities of daily living in this population. A convenience sample of 104 outpatients with COPD participated in the study. The independent variables were causal attributions, depressed mood, self-esteem, pulmonary function, and exercise capacity, and the dependent variable was functional status. There was a significant difference in functional status between those who did and those who did not ask the question, "Why me?" (p = .03). In addition, the remaining psychological variables and both physiological variables were significantly correlated with functional status (p less than or equal to .01). To identify the combination of study variables most predictive of functional status a multiple regression analysis was performed. The combined variables of exercise capacity and depression best predicted functional status (p less than .0001). It is concluded that both physiological and psychological factors are important in understanding functional status in this population. 相似文献
33.
Eileen Mary Grealish Robert P. Hawkins Pamela Meadowcroft Pamela Weaver Sharon S. Frost Percilla Lynch 《Child & youth care forum》1989,18(1):49-61
Many youth, their parents, and social services regard the unification of the family as the most desirable outcome for youth in out-of-home placements. This goal is often difficult to achieve because the families of these troubled/troubling youths are often severely dysfunctional, with multiple problems. A group process model for serving natural parents of youth in placement is described which, in conjunction with one-on-one interactions with professionals, appears to have a positive impact on these families and on youths' return home. Group components that seem particularly important are described, including attendance by invitation only, public commitment to attend and participate, reminder prompts, transportation support, babysitting support, refreshments, opportunity to visit with their child, defined staff roles, an empowering approach, and starting where the parent is. The group process maintained a relatively high level of both attendance and participation by the targeted parents. Participants tended to achieve most goals that they set in the group. Our experience indicates that interventions with natural parents of troubled youth can enable even a very dysfunctional family to improve enough to receive youth back into their home.The authors are grateful for the assistance of Sharon Estill, Jim Bernardo, Anita Mentzer, Dave Walker, and Suni Dague-Lyman for assistance in collecting the data reported here. Debbie Buchanan and others have been a great assistance in transporting families. 相似文献
34.
Karen W. Gripp Lindsey A. Morse Marni Axelrad Kathryn C. Chatfield Aaron Chidekel William Dobyns Daniel Doyle Bronwyn Kerr Angela E. Lin David D. Schwartz Barbara J. Sibbles Dawn Siegel Suma P. Shankar David A. Stevenson Mihir M. Thacker K. Nicole Weaver Sue M. White Katherine A. Rauen 《American journal of medical genetics. Part A》2019,179(9):1725-1744
Costello syndrome (CS) is a RASopathy caused by activating germline mutations in HRAS. Due to ubiquitous HRAS gene expression, CS affects multiple organ systems and individuals are predisposed to cancer. Individuals with CS may have distinctive craniofacial features, cardiac anomalies, growth and developmental delays, as well as dermatological, orthopedic, ocular, and neurological issues; however, considerable overlap with other RASopathies exists. Medical evaluation requires an understanding of the multifaceted phenotype. Subspecialists may have limited experience in caring for these individuals because of the rarity of CS. Furthermore, the phenotypic presentation may vary with the underlying genotype. These guidelines were developed by an interdisciplinary team of experts in order to encourage timely health care practices and provide medical management guidelines for the primary and specialty care provider, as well as for the families and affected individuals across their lifespan. These guidelines are based on expert opinion and do not represent evidence‐based guidelines due to the lack of data for this rare condition. 相似文献
35.
Matthew J. Bassignani Samuel J. Dwyer III Jonathan M. Ciambotti Juan M Olazagasti Ruth Moran Sean Moynihan Alfred C. Weaver Andrew M. Snyder 《Journal of digital imaging》2004,17(1):18-27
Teleradiology allows contemporaneous interpretation of imaging exams performed at some distance from the interpreting radiologist. The transmitted images are usually static. However, there is benefit to real-time review of full-motion ultrasound (US) exams as they are performed. Telesonography is transmission of full-motion sonographic data to a remote site. We hypothesize that US exams, read after having been compressed utilizing Motion Picture Experts Group version 4 (MPEG-4) compression scheme, transmitted over the Internet as streaming multimedia, decompressed, and displayed, are equivalent in diagnostic accuracy to reading the examinations locally. MPEG-4 uses variable compression on each image frame to achieve a constant output bit rate. With less compression, the bit rate rises, and the only way the encoder can contain bit rate within the set bandwidth is by lowering frame rate or reducing image quality. We review the relevant technologies and industry standard components that will enable low-cost telesonography. 相似文献
36.
Human infections caused by Brevibacterium casei, formerly CDC groups B-1 and B-3. 总被引:3,自引:0,他引:3 下载免费PDF全文
E Gruner A G Steigerwalt D G Hollis R S Weyant R E Weaver C W Moss M Daneshvar J M Brown D J Brenner 《Journal of clinical microbiology》1994,32(6):1511-1518
Forty-one clinical strains of CDC coryneform groups B-1 and B-3 were compared biochemically, by analysis of cell wall sugars, amino acids, and cellular fatty acids, and by DNA relatedness to the type strains of Brevibacterium casei, Brevibacterium epidermidis, and Brevibacterium linens. Twenty-two strains were shown to be B. casei, while five other strains formed a phenotypically inseparable genomospecies in the same genus. The remaining isolates were genetically heterogeneous, and most are probably members of the genus Brevibacterium. They were not further identified, but they were biochemically distinguishable from B. casei. Eleven of the clinical strains of B. casei were isolated from blood, and two each were isolated from cerebrospinal fluid and from pleural fluid. At least five isolates were from multiple blood or cerebrospinal fluid cultures. To our knowledge, these strains are the first described clinical isolates identified as B. casei, which was previously considered to be a nonpathogenic species. 相似文献
37.
Follower neurons in lobster (Panulirus interruptus) pyloric network regulate pacemaker period in complementary ways 总被引:2,自引:0,他引:2
Distributed neural networks (ones characterized by high levels of interconnectivity among network neurons) are not well understood. Increased insight into these systems can be obtained by perturbing network activity so as to study the functions of specific neurons not only in the network's "baseline" activity but across a range of network activities. We applied this technique to study cycle period control in the rhythmic pyloric network of the lobster, Panulirus interruptus. Pyloric rhythmicity is driven by an endogenous oscillator, the Anterior Burster (AB) neuron. Two network neurons feed back onto the pacemaker, the Lateral Pyloric (LP) neuron by inhibition and the Ventricular Dilator (VD) neuron by electrical coupling. LP and VD neuron effects on pyloric cycle period can be studied across a range of periods by altering period by injecting current into the AB neuron and functionally removing (by hyperpolarization) the LP and VD neurons from the network at each period. Within a range of pacemaker periods, the LP and VD neurons regulate period in complementary ways. LP neuron removal speeds the network and VD neuron removal slows it. Outside this range, network activity is disrupted because the LP neuron cannot follow slow periods, and the VD neuron cannot follow fast periods. These neurons thus also limit, in complementary ways, normal pyloric activity to a certain period range. These data show that follower neurons in pacemaker networks can play central roles in controlling pacemaker period and suggest that in some cases specific functions can be assigned to individual network neurons. 相似文献
38.
Conformational change as one of the earliest alterations of tau in Alzheimer's disease 总被引:15,自引:0,他引:15
Paired helical filaments (PHFs) found in Alzheimer's disease (AD) are mainly comprised of an abnormal form of tau (PHF-tau) that has undergone several post-translational modifications. Previous studies have shown that the monoclonal antibody MCI identifies a distinct conformation of tau in AD. We have assessed the temporal and spatial occurrence of the tau conformation recognized by MC1, and found its appearance in hippocampal neurons vulnerable to neurofibrillary tangle (NFT) formation in Braak Stage I and II cases. Electron microscopy has clearly demonstrated that this conformation precedes the formation of PHF. MC1 immunoaffinity chromatography also has identified a nonfilamentous, soluble pool of this abnormal tau. ELISA and immunoblotting have shown that this material is indistinguishable from that found in NFTs. This soluble component has the ability to self-assemble into PHFs in a concentration-dependent manner. Because the conformational change recognized by MCI appears before the assembly of and is found in PHF, but is not present in the normal brain, we suggest that the formation of the MCI epitope is one of the earliest pathological alterations of tau in AD. 相似文献
39.
Two additional families with popliteal pterygium syndrome are presented. Using previously published pedigrees, as well as the ones reported here, evidence is presented that supports an autosomal dominant mode of inheritance for this syndrome. Analysis of previous familial cases showed a large degree of between and within-family variation. The segregation analysis supports the dominant hypothesis (P=0.5). 相似文献
40.