首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   22805篇
  免费   1646篇
  国内免费   89篇
耳鼻咽喉   153篇
儿科学   774篇
妇产科学   523篇
基础医学   3316篇
口腔科学   329篇
临床医学   2782篇
内科学   5016篇
皮肤病学   481篇
神经病学   2398篇
特种医学   386篇
外科学   2028篇
综合类   131篇
一般理论   28篇
预防医学   2536篇
眼科学   246篇
药学   1532篇
中国医学   43篇
肿瘤学   1838篇
  2024年   20篇
  2023年   215篇
  2022年   387篇
  2021年   763篇
  2020年   510篇
  2019年   763篇
  2018年   786篇
  2017年   580篇
  2016年   656篇
  2015年   717篇
  2014年   910篇
  2013年   1191篇
  2012年   1938篇
  2011年   1949篇
  2010年   1040篇
  2009年   875篇
  2008年   1517篇
  2007年   1570篇
  2006年   1545篇
  2005年   1424篇
  2004年   1316篇
  2003年   1163篇
  2002年   1020篇
  2001年   142篇
  2000年   90篇
  1999年   151篇
  1998年   192篇
  1997年   138篇
  1996年   133篇
  1995年   121篇
  1994年   82篇
  1993年   86篇
  1992年   44篇
  1991年   43篇
  1990年   42篇
  1989年   48篇
  1988年   34篇
  1987年   23篇
  1986年   31篇
  1985年   27篇
  1984年   39篇
  1983年   26篇
  1982年   24篇
  1981年   25篇
  1980年   19篇
  1979年   13篇
  1978年   15篇
  1976年   16篇
  1973年   12篇
  1971年   10篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
51.
Lipoprotein(a) [Lp(a)] is an atherogenic and prothrombotic molecule formed by the covalent binding of the highly polymorphic apolipoprotein(a) [apo(a)] to apoprotein B-100 of LDL. High Lp(a) concentrations are a recognized genetic risk factor for coronary heart disease (CHD) and have been shown to be related with a familial clustering of ischemic cardiac events. Nevertheless, the association between apolipoprotein(a) isoforms and a positive familial history of CHD has received far less attention. In this report, we explored the distribution of apo(a) phenotypes in 127 CHD subjects with a family history of coronary events and in 92 CHD patients without such a history. Twenty-two apo(a) isoforms were detected by a high-resolution immunoblotting method. In univariate analysis, the percentage of subjects with at least one small sized apo(a) isoform was significantly higher in CHD patients with a positive family history than in those without (P<0.01). Multivariate analysis showed that apo(a) isoforms of low molecular weight were the best predictors of familial aggregation of cardiac ischemia. We conclude that apo(a) size polymorphism is strongly associated with a familial history of CHD and is more efficient than Lp(a) plasma concentrations in predicting the familial clustering of coronary disease. When detected by high-resolution techniques, apo(a) phenotypes are objective laboratory markers that can substitute for a knowledge of a positive family history of CHD and should be used, together with Lp(a) levels, to better assess the familial predisposition to coronary events.  相似文献   
52.
Isolation of Neisseria lactamicus from the nasopharynx   总被引:2,自引:1,他引:2       下载免费PDF全文
During 1971 and 1972, 71 cultures of neisseriae that attacked lactose were received by this laboratory. All strains except one from an eye swab were from the nasopharynx of healthy subjects. Nineteen similar strains from the nasopharynx were isolated in this laboratory.The characteristics of these strains were compared with those of Neisseria meningitidis, Neisseria pharyngis, Neisseria catarrhalis, and Neisseria lactamicus. The 90 strains under investigation closely resembled Neisseria meningitidis but could be differentiated by production of acid from lactose and beta-galactosidase activity and were therefore classified as Neisseria lactamicus.  相似文献   
53.
54.
Yersinia enterocolitica is an enteric pathogen that consists of six biotypes: 1A, 1B, 2, 3, 4, and 5. Strains of the latter five biotypes can carry a virulence plasmid, known as pYV, and several well-characterized chromosomally encoded virulence determinants. Y. enterocolitica strains of biotype 1A lack the virulence-associated markers of pYV-bearing strains and were once considered to be avirulent. There is growing epidemiological, clinical, and experimental evidence, however, to suggest that some biotype 1A strains are virulent and can cause gastrointestinal disease. To identify potential virulence genes of pathogenic strains of Y. enterocolitica biotype 1A, we used genomic subtractive hybridization to determine genetic differences between two biotype 1A strains: an environmental isolate, Y. enterocolitica IP2222, and a clinical isolate, Y. enterocolitica T83. Among the Y. enterocolitica T83-specific genes we identified were three, tcbA, tcaC, and tccC, that showed homology to the insecticidal toxin complex (TC) genes first discovered in Photorhabdus luminescens. The Y. enterocolitica T83 TC gene homologues were expressed by Y. enterocolitica T83 and were significantly more prevalent among clinical biotype 1A strains than other Yersinia isolates. Inactivation of the TC genes in Y. enterocolitica T83 resulted in mutants which were attenuated in the ability to colonize the gastrointestinal tracts of perorally infected mice. These results indicate that products of the TC gene complex contribute to the virulence of some strains of Y. enterocolitica biotype 1A, possibly by facilitating their persistence in vivo.  相似文献   
55.
Complement studies in membranoproliferative glomerulonephritis   总被引:1,自引:2,他引:1       下载免费PDF全文
Detailed studies of the complement system were carried out in fifteen patients with membranoproliferative glomerulonephritis. The findings of reduced levels of C3 and C7 and of circulating breakdown products of C3 in fresh plasma suggested in vivo complement activation. Low C3 levels were associated with the presence of a serum factor (the C3 nephritic factor C3NeF) which was capable of breaking down C3 in normal serum in vitro. Metabolic studies using radioactive iodine labelled C3 showed no evidence of accelerated in vivo breakdown of parenterally administered C3 suggesting that hypocomplementaemia is either maintained by diminished C3 synthesis or that accelerated catabolism is occurring in a pool that does not freely exchange with parenterally given C3. The C3 nephritic factor has so far only been identified in patients with membranoproliferative nephritis and is therefore of major diagnostic significance in patients with glomerular disease.  相似文献   
56.
57.
Traumatic brain injury (TBI) often results in a myriad of symptoms across physical, cognitive, and neurobehavioral domains. Despite inherent limitations associated with physical or cognitive impairments, the extant literature suggests that neurobehavioral symptoms tend to be the most distressing symptoms for the family and are more strongly related to poor outcome for the patient. The Neuropsychology Behavior and Affect Profile (NBAP) along with the General Functioning subscale of the Family Assessment Device (FAD-GF) and the Perceived Stress Scale were administered to 153 family members of persons who had sustained a TBI. The results provide new normative data and statistical support for the NBAP as a promising measure of neurobehavioral symptomatology following TBI. The correlation of.54 (p <.01) between FAD-GF and Full Scale NBAP scores provides powerful support for the hypothesis that family dysfunction is related to the presence of neurobehavioral symptoms in the patient. NBAP domains of Depression, Inappropriateness, Pragnosia, and Indifference appear most strongly related to family functioning and also bear a significant relationship to caregiver stress level and patient unemployment, whereas injury severity had little impact on either family functioning or neurobehavioral symptoms. The findings reinforce the significance of neurobehavioral symptoms and fortify their proposed link to family dysfunction post-TBI.  相似文献   
58.

Background  

The desired outcome of cancer vaccination is to induce a potent T cell response which can specifically recognize and eliminate autologous tumor cells in vivo. Accordingly, immunological assays that demonstrate recognition of native tumor cells (tumor-specific) may be more clinically relevant than assays that demonstrate recognition of tumor protein or peptide (antigen-specific).  相似文献   
59.
Anophthalmia or microphthalmia occur in approximately one in 10 children who have severe visual impairment. These eye malformations are often of unknown aetiology, but can be inherited in autosomal dominant, recessive or X-linked forms, and can also occur in association with specific chromosome abnormalities. Four children are described in the medical literature with microphthalmia or anophthalmia in association with chromosome rearrangements involving distal 3q, suggesting the presence of a micro/anophthalmia gene in this region. We have identified two further patients with micro/anophthalmia and chromosome rearrangements involving 3q26-->3q27 and identified a 6.7 MB common deleted region. Patient 1 had multiple abnormalities including bilateral anophthalmia, abnormalities of the first and second cranial nerves and partial absence of the corpus callosum. His karyotype was 46,XY,del(3)(q26.33q28). Patient 2 had right anophthalmia and left extreme microphthalmia. Her karyotype was 46,XX,del(3)(q26.33q28)t(3;7)(q28;q21.1). Both patients had intrauterine growth retardation (IUGR) and strikingly similar dysmorphic facies consisting of bossed forehead, downward-slanting palpebral fissures, grooved bridge of the nose, prominent low-set ears, small down-turned mouth and small mandible. We identified BAC clones mapping to distal 3q from the ENSEMBL and NCBI Entrez databases. These BAC clones were used as fluorescence in situ hybridisation (FISH) probes to identify the minimum deleted region common to both patients. This interval, between clones RPC11-134F2 and RPC11-132N15, was estimated to be 6.7 MB. We conclude that there is an anophthalmia locus within this interval. Candidate genes mapping to this region include Chordin and DVL3, a homologue of the Drosophila Dishevelled gene.  相似文献   
60.
Fifty-four subjects, aged between 20 and 35 years, divided into two subgroups, respectively 30 healthy subjects (17 males and 13 females) and 24 subjects with "gonalgia sine materia" (13 males and 11 females) underwent isokinetic exercise test in order to compare their dominant limb with the not dominant one as regard as the strength of extensor and flexor muscles of the knee. No statistically significant difference was found in any of the studied parameters in the comparison between the dominant limb and the not dominant one, both within the subgroup of healthy subjects and within the subgroup of subjects with "gonalgia sine materia". Authors conclude that psychological features may play a preeminent role in the genesis, as well as in the maintenance of "gonalgia sine materia", thus confirming previous data available in medical literature.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号