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   3382篇
  免费   208篇
  国内免费   81篇
耳鼻咽喉   16篇
儿科学   209篇
妇产科学   113篇
基础医学   412篇
口腔科学   111篇
临床医学   346篇
内科学   846篇
皮肤病学   117篇
神经病学   155篇
特种医学   419篇
外科学   222篇
综合类   82篇
预防医学   225篇
眼科学   49篇
药学   145篇
  2篇
中国医学   2篇
肿瘤学   200篇
  2023年   15篇
  2022年   28篇
  2021年   47篇
  2020年   39篇
  2019年   47篇
  2018年   66篇
  2017年   56篇
  2016年   53篇
  2015年   78篇
  2014年   95篇
  2013年   112篇
  2012年   117篇
  2011年   128篇
  2010年   131篇
  2009年   123篇
  2008年   117篇
  2007年   148篇
  2006年   118篇
  2005年   112篇
  2004年   82篇
  2003年   58篇
  2002年   81篇
  2001年   78篇
  2000年   85篇
  1999年   65篇
  1998年   143篇
  1997年   169篇
  1996年   140篇
  1995年   114篇
  1994年   124篇
  1993年   102篇
  1992年   59篇
  1991年   55篇
  1990年   59篇
  1989年   79篇
  1988年   63篇
  1987年   59篇
  1986年   64篇
  1985年   57篇
  1984年   33篇
  1983年   28篇
  1982年   25篇
  1981年   38篇
  1980年   32篇
  1979年   11篇
  1978年   13篇
  1977年   18篇
  1976年   27篇
  1975年   17篇
  1971年   10篇
排序方式: 共有3671条查询结果,搜索用时 15 毫秒
101.
Assessing the delivery of neutrophils to tissues in neutropenia   总被引:2,自引:2,他引:2  
Wright  DG; Meierovics  AI; Foxley  JM 《Blood》1986,67(4):1023-1030
Studies of neutrophil kinetics in neutropenic individuals, as well as clinical observations of variability in the occurrence of infection among patients with neutropenia, have suggested that blood neutrophil counts may not uniformly reflect the effective delivery of neutrophils to extravascular tissues where the cells perform their principal host defense functions. To evaluate this possibility we developed a sensitive, reproducible method of measuring the extravascular delivery of neutrophils to a normal mucosal site of neutrophil turnover. This method is based upon the quantification of neutrophils recoverable from saline mouth wash specimens. Twenty-five mL specimens, obtained in a controlled manner from neutropenic patients and normal subjects, were centrifuged and the sediments resuspended in 1.0 mL Hank's buffer with 2 micrograms acridine orange, incubated at 37 degrees C for 15 minutes, and then examined in a hemocytometer chamber by fluorescence microscopy. Neutrophils could be clearly distinguished by their characteristic fluorescence and were counted. With this method as few as 1,500 neutrophils were detected reliably in mouth wash specimens. Mucosal neutrophil counts varied less than 10% with repeated sampling of individual subjects over 5-day periods and were consistently greater than 1.3 X 10(5)/specimen in non-neutropenic individuals. Although profound neutropenia was generally reflected by lower than normal oral mucosal neutrophil counts, these counts were significantly higher in individuals with chronic severe neutropenia (blood neutrophils less than 300/mm3) than in patients with acute neutropenia of comparable severity that had developed following chemotherapy. Also, in individuals recovering from profound neutropenia, neutrophils usually reappeared earlier in mouth wash specimens than in blood, and oral mucosal neutrophil counts attained recovery levels more rapidly than did blood counts. This phenomenon was particularly evident in an individual with cyclic neutropenia. Moreover, mucosal neutrophils could occasionally be detected in profoundly neutropenic patients when neutrophils were not present in blood samples. These findings indicate that mucosal neutrophil counts in individuals with neutropenia provide information about the delivery of neutrophils to tissues that may not be apparent from blood neutrophil counts alone.  相似文献   
102.
Background : How tissue patterns form in development and regeneration is a fundamental issue remaining to be fully understood. The integument often forms repetitive units in space (periodic patterning) and time (cyclic renewal), such as feathers and hairs. Integument patterns are visible and experimentally manipulatable, helping us reveal pattern formative processes. Variability is seen in regional phenotypic specificities and temporal cycling at different physiological stages. Results: Here we show some cellular/molecular bases revealed by analyzing integument patterns. (1) Localized cellular activity (proliferation, rearrangement, apoptosis, differentiation) transforms prototypic organ primordia into specific shapes. Combinatorial positioning of different localized activity zones generates diverse and complex organ forms. (2) Competitive equilibrium between activators and inhibitors regulates stem cells through cyclic quiescence and activation. Conclusions: Dynamic interactions between stem cells and their adjacent niche regulate regenerative behavior, modulated by multi‐layers of macro‐environmental factors (dermis, body hormone status, and external environment). Genomics studies may reveal how positional information of localized cellular activity is stored. In vivo skin imaging and lineage tracing unveils new insights into stem cell plasticity. Principles of self‐assembly obtained from the integumentary organ model can be applied to help restore damaged patterns during regenerative wound healing and for tissue engineering to rebuild tissues. Developmental Dynamics 244:905–920, 2015. © 2015 Wiley Periodicals, Inc.  相似文献   
103.
Immunoreactive tissue kallikrein was co-localized with prolactin in all the eleven prolactin-secreting adenomas of the human anterior pituitary gland examined in this study. The intracellular distribution of immunoreactivity in the prolactin-secreting cells suggests that tissue kallikrein is located within the Golgi complex of these cells. Both the intracellular hormone-processing action and the kininogenase activity of tissue kallikrein may be of functional importance in human prolactinomas.  相似文献   
104.
OBJECTIVES: To analyze the clinical features of uveitis in psoriatic arthritis (PsA) and to investigate the factors predicting its appearance. PATIENTS AND METHODS: Retrospective cohort study (1991-2000) of 71 patients diagnosed with PsA according to the criteria of Moll and Wright. All patients were studied according to a standard protocol. The group was divided into 3 articular categories: axial, oligoarticular, and polyarticular. Human leukocyte antigen (HLA)-Cw typing was performed by the polymerase chain reaction-sequence specific oligonucleotide probes (PCR-SSOP) method in 65 patients and in 177 healthy donors. HLA-DR typing was done by serologic methods in the 71 patients and in 82 healthy donors from the same racial and geographic origin. The HLA-B27 allele also was tested among the study population. All subjects with possible inflammatory ocular disease received a complete ophthalmologic examination at the Ophthalmology Department of our hospital. Only patients with uveitis were analyzed. Univariate and multivariate analyses were applied. RESULTS: Thirteen patients had uveitis (18% of this series), 4 (31%) had an insidious onset, and the remaining had acute-onset uveitis. Five cases (39%) had bilateral-simultaneous uveitis. Ten (77%) presented with anterior uveitis only, 2 with anterior and posterior pole involvement, and only 1 case with isolated posterior pole involvement. Four patients needed oral corticosteroids; 2 of them also used immunosuppresive drugs. None of our patients developed sequelae or complications. In univariate analysis, uveitis was associated with inflammatory back pain (P =.02), sacroiliac pain (P =.001), syndesmophytes (P =.001), bilateral sacroileitis (P =.0001), HLA-DR13 (P =.002), and HLA-B27 (P =.026). In multivariate analysis, the predictive factors for uveitis were bilateral sacroileitis (OR 17, 95% CI: 3.7-76, P =.0002), HLA-DR13 (OR 24, 95% CI: 3.78-150, P =.0056), and syndesmophytes (OR 9.7, 95% CI: 0.97-97, P =.05). CONCLUSIONS: Insidious onset, bilaterality, posterior pole involvement, and chronicity are common in PsA patients with uveitis. In this study, extensive axial involvement (bilateral sacroileitis and syndesmophytes), and the HLA-DR13 antigen were the best predictors for the appearance of uveitis.  相似文献   
105.
Summary Between 1988 and 1995, 1832 HIV positive patients were evaluated in our institution. We studied the epidemiologic, immunologic and bacteriologic data, laboratory tests, and X-Ray films in those with musculoskeletal infection. We reviewed twenty-one cases of musculoskeletal infection in twenty patients aged 23–35 years (mean 28,6 years, M:F=15:5). In all of them risk factor for HIV was intravenous drug abuse. The number of CD4 positive lymphocytes ranged from 0,003 to 0,5 109/l. Staphylococcus aureus was the organism responsible of the infection in twelve cases, all active intravenous drug abusers at the time the diagnosis was done. The remaining causative agents were: Mycobacterium tuberculosis (3 cases), Candida albicans (2 cases), Salmonella subgroup 1 (1 case), Neisseria gonorrhoeae (1 case), Pseudomona aeruginosa (1 case) and Streptococcus agalactiae (1 case). Fifteen infections were diagnosed between 1988 and 1991 and 6 between 1992 and 1995. Musculoskeletal infectious lesions in HIV positive patients in our country are related in the majority of cases to intravenous drug abuse. In the last four years due to a National medical health care plan conducted to educate this group of people the number of musculoskeletal infections is decreasing.  相似文献   
106.
A subsample (1.6%; n = 13,260) of a healthy Jamaican population of food-handlers, studied by Murphy et al. (1991), who were serologically positive (n = 99) or negative (n = 113) for HTLV-I was investigated for intestinal parasitic infection using coprological methods. Helminth infection included Ascaris lumbricoides (2.8%), Trichuris trichiura (7.1%) and hookworms (6.1%). Entamoeba coli was found in 21.8% of samples, while E. hartmanni, Giardia lamblia, Endolimax nana, Iodamoeba bütschlii and Chilomastix mesnili each occurred in less than 10% of responders. T. trichiura displayed a higher prevalence (10.6 vs 3%) (chi 2 = 4.623; P = 0.03) in the HTLV-I negative group. G. lamblia was detected more frequently among HTLV-I carriers compared to controls (9.1 and 3.5%, respectively), but the association was not statistically significant (chi 2 = 2.825; P = 0.09). Infection with intestinal parasites is likely to occur independent of HTLV-I status: however, possible HTLV-I-induced immunosuppression may lead to higher intensity infections of certain organisms thus facilitating easier detection using parasitological methods. The immunomodulatory potential of HTLV-I infection in the aetiology of non-malignant diseases requires further investigation.  相似文献   
107.
108.
109.
Look  AT; Peiper  SC; Douglass  EC; Trent  JM; Sherr  CJ 《Blood》1986,67(3):637-645
Spontaneous amplification of genes encoding two different human myeloid surface antigens was observed after DNA-mediated gene transfer of cellular DNA from the human myeloid cell line HL-60 into NIH-3T3 mouse fibroblasts. Transformed recipient cells with highly amplified expression of either of two donor membrane polypeptides, gp150 or p67, were isolated with a fluorescence-activated cell sorter (FACS), using monoclonal antibodies specific for human myeloid cells. Immunoprecipitation of enzymatically radioiodinated polypeptides from the surface of transformed NIH-3T3 cells confirmed that expression of these proteins was amplified tenfold to 20-fold in comparison to their expression on human myeloid cell lines. The cellular DNA of cloned secondary and tertiary transformants expressing high levels of gp150 and p67 contained amplified sets of DNA restriction fragments that hybridized with human repetitive DNA sequences. Cytogenetic analysis of subclones overexpressing gp150 revealed extrachromosomal double minutes (DMs), whose presence correlated with the unstable expression of the membrane polypeptide. Human sequences in gp150-positive clones did not localize to chromosomes, consistent with their association with extrachromosomal DMs. By contrast, p67-positive subclones stably expressed the antigen, and in situ hybridization to metaphase spreads demonstrated that amplified human DNA sequences were integrated into a specific marker chromosome. Cytogenetic analysis of the parental NIH- 3T3 subclone used in these studies disclosed DMs in a low percentage of metaphases, suggesting that the recipient cells have a propensity for amplifying donor DNA.  相似文献   
110.
Molecular heterogeneity in acute leukemia lineage switch   总被引:1,自引:0,他引:1  
Six cases of acute leukemia that underwent lineage switch from acute lymphocytic leukemia to acute myelogenous leukemia are reported. The mean age of the patients was 24 years, time to conversion was 36 months, and survival after conversion was only 3 months. Of the three cases which showed abnormal metaphases at both diagnosis and conversion, two (cases 2, 5) showed related cytogenetic abnormalities, and the third showed (case 3) independent chromosomal changes. Molecular analysis for immunoglobulin heavy chain and T-cell receptor beta chain genes showed that five of the six cases had rearrangement of at least one of these lymphoid associated genes at conversion to acute myelogenous leukemia. The single case (case 3) in which there were no lymphoid gene rearrangements at conversion was also the only case in which independent karyotypic abnormalities at diagnosis and conversion were demonstrated. Our findings suggest that lineage switch can represent either relapse of the original clone with heterogeneity at the molecular level or the emergence of a second new leukemic clone without molecular heterogeneity.  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