全文获取类型
收费全文 | 2872篇 |
免费 | 241篇 |
国内免费 | 59篇 |
专业分类
耳鼻咽喉 | 18篇 |
儿科学 | 54篇 |
妇产科学 | 86篇 |
基础医学 | 436篇 |
口腔科学 | 41篇 |
临床医学 | 347篇 |
内科学 | 712篇 |
皮肤病学 | 27篇 |
神经病学 | 168篇 |
特种医学 | 146篇 |
外科学 | 305篇 |
综合类 | 66篇 |
一般理论 | 5篇 |
预防医学 | 133篇 |
眼科学 | 116篇 |
药学 | 267篇 |
中国医学 | 8篇 |
肿瘤学 | 237篇 |
出版年
2023年 | 21篇 |
2022年 | 37篇 |
2021年 | 66篇 |
2020年 | 47篇 |
2019年 | 61篇 |
2018年 | 96篇 |
2017年 | 64篇 |
2016年 | 59篇 |
2015年 | 71篇 |
2014年 | 90篇 |
2013年 | 120篇 |
2012年 | 211篇 |
2011年 | 185篇 |
2010年 | 100篇 |
2009年 | 101篇 |
2008年 | 157篇 |
2007年 | 199篇 |
2006年 | 152篇 |
2005年 | 176篇 |
2004年 | 157篇 |
2003年 | 118篇 |
2002年 | 99篇 |
2001年 | 77篇 |
2000年 | 69篇 |
1999年 | 54篇 |
1998年 | 37篇 |
1997年 | 37篇 |
1996年 | 17篇 |
1995年 | 28篇 |
1994年 | 23篇 |
1993年 | 24篇 |
1992年 | 38篇 |
1991年 | 36篇 |
1990年 | 40篇 |
1989年 | 26篇 |
1988年 | 25篇 |
1987年 | 31篇 |
1986年 | 29篇 |
1985年 | 25篇 |
1984年 | 22篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1980年 | 13篇 |
1979年 | 14篇 |
1978年 | 12篇 |
1977年 | 9篇 |
1976年 | 13篇 |
1975年 | 10篇 |
1973年 | 11篇 |
1972年 | 8篇 |
排序方式: 共有3172条查询结果,搜索用时 15 毫秒
11.
12.
Inhibition of human endothelial cell proliferation in vitro in response to n-butyrate and propionate
The study aimed to investigate the effects of n-butyrate and propionate on the proliferation and viability of human endothelial cells in culture. Proliferation was assessed by a 24-hour bromodeoxyuridine pulse labelling and immunoperoxidase method and viability was assessed by a colorimetric viability (MTT) assay. Endothelial cells were isolated from human umbilical vein by collagenase digestion. Experiments were performed on 96-well plates and cultures were exposed to different concentrations of n-butyrate and propionate for 2 days. n-butyrate and propionate caused significant reductions in the proliferation of endothelial cells at concentrations of 1.25 mM and 10 mM respectively (p less than 0.05); the reduction in proliferation was dose-dependent for both agents. n-butyrate was a more potent inhibitor of proliferation than propionate. However, there were no significant effects on the viability of the cells with both agents up to the highest concentrations tested (25 mM). The data indicate that n-butyrate and propionate inhibit endothelial cell proliferation which may contribute to the pathogenic effects of dental plaque in periodontal disease. 相似文献
13.
Stress-activated protein kinases mediate cell migration in human airway epithelial cells 总被引:1,自引:0,他引:1
White SR Tse R Marroquin BA 《American journal of respiratory cell and molecular biology》2005,32(4):301-310
Airway epithelial cell (AEC) repair immediately after injury requires coordinated cell spreading and migration at the site of injury. Stress-activated protein kinases such as p38 MAPK and c-Jun N-terminal Protein Kinase (JNK) modulate several responses to cell stress and injury, but their role in AEC migration is not clear. We examined migration in confluent 16HBE14o(-) human AEC lines and in primary AEC grown on collagen-IV. Wounds were created by mechanical abrasion and followed to closure using digital microscopy. Inhibitors of either p38 extracellular signal-regulated kinase (ERK)1/2 (PD98059), mitogen-activated protein kinase (MAPK) (SB203580), or JNK (SP600125) could block cell migration substantially. Inhibiting JNK but not p38 MAPK or ERK1/2 blocked extension of cells into the wound region from the original line of injury. Initial migration was associated with phosphorylation of ERK, p38 MAPK, and JNK within 5-15 min. The downstream effector of p38, heat shock protein 27, also was phosphorylated rapidly after injury; phosphorylation could be blocked by prior treatment with SB203580 but not SP600125. The downstream effector of JNK, c-Jun, likewise was phosphorylated rapidly after injury and could be blocked by inhibiting JNK. Our data demonstrate that p38 MAPK, JNK, and ERK1/2 participate in the early stages of AEC migration. 相似文献
14.
AIM: Development of a specific polymerase chain reaction (PCR) assay for detection of the pre-core, stop codon, mutant of hepatitis B virus (HBV). METHODS: PCR primers, specific at the 3'-end for nucleotide 1896 of either the pre-core, stop codon, mutant or wild type HBV, were synthesised using published sequence data. Positive control templates for both types of virus were synthesised by the PCR, incorporating sequences specific for each virus type at the appropriate position. These templates were used to optimise the specificity of the procedure. Formalin fixed, paraffin wax embedded human tissue from acute or fulminant HBV hepatitis from Hong Kong or Oxford was then investigated for presence of mutant or wild type virus. The HBV DNA was amplified from this tissue using a two step procedure, with an initial amplification phase followed by a second diagnostic phase on optimally diluted target DNA. RESULTS: Specific detection of mutant or wild type HBV was achieved. An important factor in determining specificity was the temperature of annealing, 70 degrees C proving to be highly specific. To overcome the inherent variation of target copy number in clinical samples and to provide an intrinsic positive control, it was important to generate and standardise the amount of target HBV used for the specific PCR. Two cases of fulminant hepatitis and four cases of acute hepatitis from Hong Kong, and one case of fulminant hepatitis from Oxford, contained only wild type HBV, with no evidence of a mutant virus. CONCLUSION: This method can be applied to FFPE tissues. It is rapid, non-radioactive, and specific for the stop codon mutation at nucleotide 1896 of HBV. Preliminary investigation of a small number of cases of fulminant hepatitis from Oxford and Hong Kong showed only wild type virus. The result differs from results published from Japan and Israel. 相似文献
15.
Calcium ionophore-induced acrosome reaction correlates with fertilization rates in vitro in patients with teratozoospermic semen 总被引:5,自引:3,他引:5
The aim of this study was to determine the relationship between calcium
ionophore A23187-induced acrosome reaction (AR) and sperm fertilizing
ability. Semen samples remaining after preparation for standard IVF were
studied in 109 patients who had sperm concentrations > or =20 x
10(6)/ml. Ionophore-induced AR was performed on motile spermatozoa selected
by centrifugation on a Percoll gradient. Semen analysis was performed using
standard methods. Patients with higher (>50%, n = 76) fertilization
rates had significantly higher ionophore-induced AR than patients with
lower (<50%, n = 33) fertilization rates (49 +/- 14 versus 38 +/- 21%, P
< 0.05). When the data from all patients were analysed by logistic
regression, only the percentage sperm motility in insemination medium and
ionophore-induced AR were significantly related to fertilization rates.
Similar results were also obtained when the data from a subgroup of
patients with poor (<15% normal) sperm morphology were analysed.
However, when patients with normal sperm morphology > or =15% were
analysed separately, only sperm count and the percentage of spermatozoa
with progressive motility in semen were significantly related to
fertilization rates. In conclusion, ionophore- induced AR was significantly
related to fertilization rates in vitro mainly in patients with
teratozoospermic semen. Tests for ionophore- induced AR may provide
additional information about sperm fertilizing ability but may not indicate
specific defects of the physiological AR.
相似文献
16.
Pulmonary pathological features in coronavirus associated severe acute respiratory syndrome (SARS) 总被引:5,自引:0,他引:5
Tse GM To KF Chan PK Lo AW Ng KC Wu A Lee N Wong HC Mak SM Chan KF Hui DS Sung JJ Ng HK 《Journal of clinical pathology》2004,57(3):260-265
BACKGROUND: Severe acute respiratory syndrome (SARS) became a worldwide outbreak with a mortality of 9.2%. This new human emergent infectious disease is dominated by severe lower respiratory illness and is aetiologically linked to a new coronavirus (SARS-CoV). METHODS: Pulmonary pathology and clinical correlates were investigated in seven patients who died of SARS in whom there was a strong epidemiological link. Investigations include a review of clinical features, morphological assessment, histochemical and immunohistochemical stainings, ultrastructural study, and virological investigations in postmortem tissue. RESULTS: Positive viral culture for coronavirus was detected in most premortem nasopharyngeal aspirate specimens (five of six) and postmortem lung tissues (two of seven). Viral particles, consistent with coronavirus, could be detected in lung pneumocytes in most of the patients. These features suggested that pneumocytes are probably the primary target of infection. The pathological features were dominated by diffuse alveolar damage, with the presence of multinucleated pneumocytes. Fibrogranulation tissue proliferation in small airways and airspaces (bronchiolitis obliterans organising pneumonia-like lesions) in subpleural locations was also seen in some patients. CONCLUSIONS: Viable SARS-CoV could be isolated from postmortem tissues. Postmortem examination allows tissue to be sampled for virological investigations and ultrastructural examination, and when coupled with the appropriate lung morphological changes, is valuable to confirm the diagnosis of SARS-CoV, particularly in clinically unapparent or suspicious but unconfirmed cases. 相似文献
17.
Pseudoangiomatous stromal hyperplasia (PASH) is an uncommon lesion usually found in premenopausal women. Histologically, it is characterized by complex, anatomosing, empty slit-like spaces in a dense collagenous stroma. These pseudoangiomatous spaces are lined by monomorphic spindle cells of myofibroblastic differentiation. Cytological features of PASH are rarely discussed and reported, and may pose diagnostic challenge to surgical pathologists. Two cases of PASH are reported with emphasis on the FNAC features and cytologic differentiation from other benign fibroepithelial lesions. 相似文献
18.
Stein TP; Oram-Smith JC; Leskiw MJ; Wallace HW; Long LC; Leonard JM 《The American journal of physiology》1976,230(5):1321-1325
19.
Laura McGillis Nimish Mittal Daniel Santa Mina Joyce So Medha Soowamber Aliza Weinrib Leslie Soever Dmitry Rozenberg Louis Liu Yvonne Tse Joel Katz George S Charames Kieran Murphy Peter Vadas Maxwell P Slepian Scott Walsh Lindsay Wilson Arnon Adler Alyssa Franzese Laura Hussey Dayna‐Lynn Nevay Juan Guzman Hance Clarke 《American journal of medical genetics. Part A》2020,182(3):484-492
The new 2017 diagnostic criteria for hypermobile Ehlers–Danlos Syndrome (hEDS) provide a framework for diagnosing hEDS but are more stringent than the previous Villefranche criteria. Our clinical experience at the GoodHope EDS clinic was that the 2017 criteria left many highly symptomatic patients without a diagnosis of hEDS. We conducted a retrospective cohort study to confirm our clinic experience and assess the accuracy of the 2017 diagnostic criteria for hEDS in patients who had a previous hEDS diagnosis based on the Villefranche criteria. Our study found that 15% (n = 20 of 131) of patients with a prior diagnosis of hEDS met the 2017 diagnostic criteria, and many of the traits used to distinguish hEDS were not significantly more frequent in patients who met 2017 criteria versus those who did not. In both groups objective systemic manifestations were found less frequently than subjective systemic manifestations. Beighton score (BS) as assessed by primary care practitioner was found to be higher than assessment by EDS practitioner in 81% (n = 74 of 91) of cases. Generalized joint hypermobility was confirmed in only 46% (n = 51 of 111) of patients who had a previous diagnosis of hEDS. Higher BS did not correlate with increased number of systemic manifestations in our cohort. Common comorbidities of hEDS were found with similar frequency in those who met 2017 criteria and those who did not. Based on our cohort, the 2017 hEDS diagnostic criteria require refinement to improve its diagnostic accuracy. 相似文献
20.
Studies on 50 nasal washings, 16 parotid salivas from ragweed-allergic patients, and 10 secretions from normal subjects showed considerable variation in protein and immunoglobulin concentrations. Only 2 immunoglobulins, A and G, were found in nasal washings. Of 26 parotid salivas studied (allergic and controls), IgA was found in 26, IgG in 4, and IgM in 3 specimens. Anti-ragweed antibodies in the serum and exocrine secretions of allergic patients were examined by means of Prausnitz-Küstner (PK) test, radioimmunoelectrophoresis, radioimmunodiffusion, and tanned cell hemagglutination (TH) tests. The incidence of IgE, IgA, and IgG antibodies to ragweed in the sera and nasal washings in a group of 22 patients with previous immunotherapy was compared to that of 28 patients without immunotherapy. The immunotherapy seemed to affect the incidence of serum IgE and IgG antibodies but has no influence on the incidence of anti-ragweed antibodies in the nasal washings. PK activity of nasal washings could be removed by absorption with anti-IgE but not anti-IgA or anti-IgG immunosorbents. Anti-ragweed antibodies could be detected in parotid salivas only by the TH test. 相似文献