全文获取类型
收费全文 | 10974篇 |
免费 | 1183篇 |
国内免费 | 34篇 |
专业分类
耳鼻咽喉 | 69篇 |
儿科学 | 340篇 |
妇产科学 | 433篇 |
基础医学 | 1034篇 |
口腔科学 | 141篇 |
临床医学 | 3019篇 |
内科学 | 1933篇 |
皮肤病学 | 138篇 |
神经病学 | 825篇 |
特种医学 | 200篇 |
外科学 | 1076篇 |
综合类 | 128篇 |
一般理论 | 13篇 |
预防医学 | 1293篇 |
眼科学 | 136篇 |
药学 | 552篇 |
中国医学 | 1篇 |
肿瘤学 | 860篇 |
出版年
2023年 | 155篇 |
2022年 | 93篇 |
2021年 | 195篇 |
2020年 | 179篇 |
2019年 | 141篇 |
2018年 | 278篇 |
2017年 | 228篇 |
2016年 | 269篇 |
2015年 | 257篇 |
2014年 | 394篇 |
2013年 | 520篇 |
2012年 | 627篇 |
2011年 | 792篇 |
2010年 | 487篇 |
2009年 | 515篇 |
2008年 | 655篇 |
2007年 | 706篇 |
2006年 | 679篇 |
2005年 | 698篇 |
2004年 | 640篇 |
2003年 | 578篇 |
2002年 | 574篇 |
2001年 | 153篇 |
2000年 | 145篇 |
1999年 | 175篇 |
1998年 | 152篇 |
1997年 | 148篇 |
1996年 | 123篇 |
1995年 | 125篇 |
1994年 | 111篇 |
1993年 | 69篇 |
1992年 | 125篇 |
1991年 | 81篇 |
1990年 | 81篇 |
1989年 | 56篇 |
1988年 | 71篇 |
1987年 | 66篇 |
1986年 | 65篇 |
1985年 | 78篇 |
1984年 | 62篇 |
1983年 | 61篇 |
1982年 | 49篇 |
1981年 | 42篇 |
1980年 | 34篇 |
1979年 | 38篇 |
1978年 | 30篇 |
1977年 | 55篇 |
1976年 | 40篇 |
1975年 | 37篇 |
1970年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
We have developed a highly sensitive cytolysis test, the fluorolysis assay, as a simple nonradioactive and inexpensive alternative to the standard 51Cr-release assay. P815 cells were stably transfected with a plasmid expressing the enhanced green fluorescent protein (EGFP) gene. These target cells were coated with or without cognate peptide or anti-CD3 Ab and then incubated with CD8(+) T cells to allow antigen-specific or nonspecific lysis. The degree of target cell lysis was measured using flow cytometry to count the percentage of viable propidium iodide(-) EGFP(+) cells, whose numbers were standardized to a reference number of fluorochrome-linked beads. By using small numbers of target cells (200-800 per reaction) and extended incubation times (up to 2 days), the antigen-specific cytolytic activity of one to two activated CD8(+) T cells of a CTL line could be detected. The redirected fluorolysis assay also measured the activity of very few (> or =6) primary CD8(+) T cells following polyclonal activation. Importantly, antigen-specific lysis by small numbers (> or =25) of primary CD8(+) T cells could be directly measured ex vivo. This exquisite sensitivity of the fluorolysis assay, which was at least 8-33-folds higher than an optimized 51Cr-release assay, allows in vitro and ex vivo studies of immune responses that would otherwise not be possible due to low CTL numbers or frequencies. 相似文献
92.
Comorbid psychiatric disorders in depressed outpatients: demographic and clinical features 总被引:2,自引:0,他引:2
Rush AJ Zimmerman M Wisniewski SR Fava M Hollon SD Warden D Biggs MM Shores-Wilson K Shelton RC Luther JF Thomas B Trivedi MH 《Journal of affective disorders》2005,87(1):43-55
BACKGROUND: This study evaluated the clinical and sociodemographic features associated with various degrees of concurrent comorbidity in adult outpatients with nonpsychotic major depressive disorder (MDD). METHODS: Outpatients enrolled in the STAR*D trial completed the Psychiatric Diagnostic Screening Questionnaire (PDSQ). An a priori 90% specificity threshold was set for PDSQ responses to ascertain the presence of 11 different concurrent DSM-IV Axis I disorders. RESULTS: Of 1376 outpatients, 38.2% had no concurrent comorbidities, while 25.6% suffered one, 16.1% suffered two, and 20.2% suffered three or more comorbid conditions. Altogether, 29.3% met threshold for social anxiety disorder, 20.8% for generalized anxiety disorder, 18.8% for posttraumatic stress disorder, 12.4% for bulimia, 11.9% for alcohol abuse/dependence, 13.4% for obsessive-compulsive disorder, 11.1% for panic disorder, 9.4% for agoraphobia, 7.3% for drug abuse/dependence, 3.7% for hypochondriasis, and 2.2% for somatoform disorder. Those with more concurrent Axis I conditions had earlier ages at first onset of MDD, longer histories of MDD, greater depressive symptom severity, more general medical comorbidity (even though they were younger than those with fewer comorbid conditions), poorer physical and mental function, health perceptions, and life satisfaction; and were more likely to be seen in primary care settings. LIMITATIONS: Participants had to meet entry criteria for STAR*D. Ascertainment of comorbid conditions was not based on a structured interview. CONCLUSIONS: Concurrent Axis I conditions (most often anxiety disorders) are very common with MDD. Greater numbers of concurrent comorbid conditions were associated with increased severity, morbidity, and chronicity of their MDD. 相似文献
93.
Comparison of serum vitamin B12 estimation by saturation analysis with intrinsic factor and with R-protein as binding agents.
下载免费PDF全文
![点击此处可从《Journal of clinical pathology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
It has been reported that serum vitamin B12 levels assayed by saturation analysis methods may give misleadingly high results, so much so that the diagnosis of vitamin B12 deficiency may be obscured. This defect was ascribed largely to assays using a vitamin B12 binder other than pure intrinsic factor. To test out this hypothesis two assays were set up, one using saliva (non-intrinsic factor R-binder) and the other using human gastric (intrinsic factor) as B12-binding agents. Both assays were able to differentiate sera from patients with pernicious anaemia from those from control subjects. Published results accumulated over the past 10 years indicate that properly designed and performed saturation analysis vitamin B12 assays are as reliable as microbiological assay methods for detecting low serum B12 levels. The failure of some methods to do does not appear to be due to the nature of the B12-binding agent. 相似文献
94.
G Millgan R Graham S Hanratty W Muir R Mitchell 《Journal of clinical pathology》1981,34(10):1091-1093
Concentration of factor VIII from fresh plasma by cryoprecipitation remains the basis for preparation of products used to treat haemophilia A. This paper describes the preparation of a factor VIII concentrate from small plasma pools in transfusion centres with drying facilities. The dried concentrate from one litre of plasma dissolves very well in 50 or 100 ml of distilled water and contains around 500 IU per bottle. The specific activity per mg protein is 0.19 IU and the fibrinogen concentration is half that in frozen cryoprecipitate. This method of drying causes no appreciable loss in the factor VIIIC activity and little denaturation as shown by the factor-VIII-related antigen/factor VIIIC ratio of 1.7. 相似文献
95.
Acrocentric interconnections and NOR (nucleolus organizer region) variants are frequently observed in silver-stained metaphase preparations from lymphocytes of phenotypically normal individuals. The types of interconnections and of NOR variants are outlined. It is speculated that the satellite acrocentrics (both normal and variant) are the consequence of breakage and recoiling of these interconnections. Awareness of these two features of the human genome may facilitate understanding of the NOR/nucleolus interaction(s) in such important processes as nucleolus formation and in development and/or diagnosis of disease states (i.e., malignancy). 相似文献
96.
Robert J. Calsyn Gary A. Morse Robert D. Yonker Joel P. Winter Kathy J. Pierce Matthew J. Taylor 《Journal of community psychology》2003,31(4):339-348
Participants in this study suffered from severe mental illness and were homeless at baseline. They were given their choice of five different treatment programs. The current study investigated two major questions: (1) what is the impact of positive expectancies about the efficacy of the chosen program on number of contacts with the chosen program and client outcomes; and (2) what is the impact of positive views about nonchosen programs (alternative choice variables) on contact with the chosen program and client outcomes. Client outcomes assessed were psychotic symptoms, days homeless, and client satisfaction. Positive expectancy variables were the number of reasons for choosing a program and confidence that the program would help. Alternative choice variables were the number of nonchosen programs visited and the attractiveness of a nonchosen program. Only the number of reasons for choosing the program was significantly related to program contact with the chosen program. Both of the positive expectancy variables and program contact were significantly correlated with consumer satisfaction. In general, neither the positive expectancy variables nor the alternative choice variables predicted changes in psychotic symptoms nor days homeless. © 2003 Wiley Periodicals, Inc. J Comm Psychol 31: 339–348, 2003. 相似文献
97.
98.
Monica Fonseca-Aten Pamela J Okada Karen L Bowlware Susana Chavez-Bueno Asuncion Mejias Ana Maria Rios Kathy Katz Kurt Olsen Simon Ng Hasan S Jafri George H McCracken Octavio Ramilo R Doug Hardy 《Annals of allergy, asthma & immunology》2006,97(4):457-463
BACKGROUND: Clarithromycin is postulated to possess immunomodulatory properties in addition to its antimicrobial activity. OBJECTIVE: To evaluate the effect of clarithromycin on serum and nasopharyngeal cytokine and chemokine concentrations in children with an acute exacerbation of recurrent wheezing. METHODS: Children with a history of recurrent wheezing or asthma and who presented with an acute exacerbation of wheezing were enrolled in a double-blind, randomized trial of clarithromycin vs placebo. Concentrations of tumor necrosis factor alpha (TNF-alpha), interferon-gamma (IFN-gamma), interleukin-1beta (IL-1beta), IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, granulocyte-macrophage colony-stimulating factor, RANTES, eotaxin, macrophage inflammatory protein 1alpha, macrophage inflammatory protein 1beta, and monocyte chemoattractant protein 1 were measured in serum and/or nasopharyngeal aspirates before, during, and after therapy. Mycoplasma pneumoniae and Chlamydophila pneumoniae infection were evaluated for by polymerase chain reaction and serologic testing. RESULTS: Nasopharyngeal concentrations of TNF-alpha, IL-1beta, and IL-10 were significantly and persistently lower in children treated with clarithromycin compared with placebo. There tended to be a greater effect of clarithromycin on nasopharyngeal cytokine concentrations in patients with evidence of M. pneumoniae or C. pneumoniae infection. No significant differences were detected in serum cytokines for children treated with clarithromycin compared with placebo. CONCLUSION: Clarithromycin therapy reduces mucosal TNF-alpha, IL-1beta, and IL-10 concentrations in children with an acute exacerbation of recurrent wheezing. 相似文献
99.
We studied whether cytokine receptors (Rs) on T cells associate with lipid microdomains ("rafts"). Low-dose phytohemagglutinin (PHA)-stimulated human T cells were separated into cytoplasmic, membrane, and raft fractions by buoyant density centrifugation. Examination of these fractions for the presence of interleukin (IL)-2- and -15R chains and associated signaling molecules by Western blotting revealed marked, selective enrichment of the IL-2/15R beta-chain in rafts before IL-2 stimulation. After IL-2 stimulation, a substantial amount of the beta-chain was found in the membrane fraction. This partial translocation was also observed for the beta-chain-associated molecules JAK-1, p56(lck), and grb-2. Finally, raft disruption with methyl-beta-cyclodextrin (MBCD) attenuated IL-2-induced tyrosine phosphorylation events and selectively decreased the surface expression of the IL-2/15R beta-chain detected by flow cytometry. These results show that the IL-2/15R beta-chain is enriched in rafts obtained from low-dose, PHA-stimulated T cells, that IL-2 binding alters this enrichment, and that this enrichment may be functionally relevant as a possible mechanism to ensure cytokine selectivity and specificity. 相似文献
100.
Inaccurate reporting of the absence of an endocervical (EC) component on Pap smears often results in slide rescreens, amended reports, clinician dissatisfaction, and sometimes unnecessary repeat smears. Therefore, the accuracy of reporting EC component adequacy was selected as a quality indicator for the laboratory continuous quality improvement program (CQI). The process consisted of problem identification, analysis of the situation, collection of data, implementation of solutions, and evaluation of results. The objective of the study was to determine if the accuracy of reporting EC component adequacy on Pap smears improved after application of such a program. During the first phase, 150 Pap smears originally reported with the absence of an adequate EC component and 150 smears reported with the presence of an adequate EC component were rescreened to measure the baseline accuracy of EC component adequacy reporting. The improvement process was then implemented. A cause-and-effect diagram was developed and root cause was determined. A presentation was then made to the cytology staff. Criteria for EC component adequacy were reviewed, examples were shown, and standardized marking of EC component was implemented. Following improvement actions, a second audit of 150 Pap smears reported with the absence of an adequate EC component as well as 150 smears reported with the presence of an adequate EC component was undertaken to measure change in performance in assessing EC component adequacy. For the baseline rescreening, before initiation of the CQI program, 98% accuracy was achieved with smears that were reported as adequate for EC component present. However, the accuracy with smears reported as absence of an adequate EC component was only 71%, i.e., an adequate EC component was identified in almost 1/3 of these cases on rescreen. After the implementation of improvement actions, the accuracy with smears reported with the presence of EC component remained high (98%) and the accuracy of reporting the absence of EC component was 90%. The difference of the latter before and after the implementation was statistically significant (P = 0.015, z-test). The accuracy of reporting EC component adequacy increased following the CQI process. Using reporting EC component adequacy as an example, we demonstrate that by treating clinical problems as quality control issues and applying basic quality improvement tools, a positive outcome can be effected. 相似文献