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   17961篇
  免费   1078篇
  国内免费   37篇
耳鼻咽喉   370篇
儿科学   530篇
妇产科学   497篇
基础医学   2581篇
口腔科学   285篇
临床医学   1629篇
内科学   3024篇
皮肤病学   593篇
神经病学   1981篇
特种医学   855篇
外科学   2862篇
综合类   150篇
一般理论   22篇
预防医学   1162篇
眼科学   436篇
药学   931篇
中国医学   5篇
肿瘤学   1163篇
  2022年   130篇
  2021年   269篇
  2020年   153篇
  2019年   251篇
  2018年   312篇
  2017年   256篇
  2016年   351篇
  2015年   365篇
  2014年   485篇
  2013年   656篇
  2012年   910篇
  2011年   981篇
  2010年   578篇
  2009年   533篇
  2008年   840篇
  2007年   930篇
  2006年   840篇
  2005年   850篇
  2004年   743篇
  2003年   716篇
  2002年   731篇
  2001年   524篇
  2000年   526篇
  1999年   482篇
  1998年   230篇
  1997年   220篇
  1996年   188篇
  1995年   170篇
  1994年   161篇
  1993年   128篇
  1992年   347篇
  1991年   328篇
  1990年   279篇
  1989年   294篇
  1988年   254篇
  1987年   228篇
  1986年   259篇
  1985年   232篇
  1984年   176篇
  1983年   150篇
  1982年   95篇
  1981年   106篇
  1979年   135篇
  1978年   107篇
  1977年   94篇
  1976年   92篇
  1975年   91篇
  1974年   105篇
  1973年   112篇
  1971年   100篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
Children, and particularly neonates, often receive inadequate pain relief after surgery. In this review we describe the important physiological and pharmacological differences between babies and children, and discuss practical aspects of pain assessment and relief.  相似文献   
43.
The Australian Leukaemia Study Group myeloma study (MM1) aimed to determine the prognostic significance of clinical and immunophenotypic markers in patients with multiple myeloma. All patients were treated with standard dose melphalan and prednisone. Seventy-four patients were entered and the median survival was 27 months. Serum beta 2-microglobulin (βM) and albumin levels were the only significant clinical factors influencing survival (p = 0.007 and p = 0.008, respectively). Patients with raised levels of CD38+ lymphocytes at presentation had a significantly shorter survival than patients with normal levels (p = 0.01, logrank test, median 19 months vs 33 months). CD38 antigen expression was independent of β2M but patients with raised levels of CD38 had significantly lower levels of albumin than patients with normal levels (p = 0.001) which may explain their poorer survival. Salmon and Durie stage was not associated with antigen expression. No other B-cell antigens (CD10, CD19, CD20, CD21, CD22, CD23, FMC1 or FMC7) or plasma cell antigens tested (PCA-1) were found to be associated with prognosis. Patients who achieved plateau phase had a better prognosis than those who did not (p = 0.04 in a landmark analysis). Patients who achieved plateau phase following an objective response appeared to have a better prognosis than those who were in plateau phase at presentation (p = 0.09 in a landmark analysis). Light chain isotype suppression (LCIS) was not associated with a significant survival advantage and did not correlate with any known prognostic indicator. We conclude that phenotypic analysis of peripheral blood lymphocytes for CD38 antigen at diagnosis may be useful as a prognostic indicator in patients with myeloma.  相似文献   
44.
Cytokines (IL-1 alpha and IL-2) and soluble interleukin 2 receptors (sIL-2r) were evaluated in patients with rheumatoid arthritis (RA) and controls. In RA, serum sIL-2r and IL-1 alpha were increased, and sIL-2r were significantly higher in synovial fluid than in serum. Serum levels of sIL-1r but not IL-1 alpha were increased in patients with acute infections, suggesting additional discriminatory specificity for IL-1 alpha. Both tender and swollen joint scores were higher for patients with RA with serum sIL-2r levels greater than or equal to 700 U/ml. Quantitation of immune mediators may be useful in the clinical assessment of RA in addition to their implication regarding the pathogenesis of the disease.  相似文献   
45.
46.
Glucocorticoids (GCs, cortisol in human) are associated with impairments in declarative memory retrieval. Brain regions hypothesized to mediate these effects are the hippocampus and prefrontal cortex (PFC). Our aim was to use fMRI in localizing the effects of GCs during declarative memory retrieval. Therefore, we tested memory retrieval in 21 young healthy males in a randomized placebo-controlled crossover design. Participants encoded word lists containing neutral and emotional words 1 h prior to ingestion of 20 mg hydrocortisone. Memory retrieval was tested using an old/new recognition paradigm in a rapid event-related design. It was found that hydrocortisone decreased brain activity in both the hippocampus and PFC during successful retrieval of neutral words. These observations are consistent with previous animal and human studies suggesting that glucocorticoids modulate both hippocampal and prefrontal brain regions that are crucially involved in memory processing. Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   
47.
M E Wolf  R H Roth 《Neuropharmacology》1987,26(8):1053-1059
The ability of dopamine (DA) agonists and antagonists to modulate the K+-evoked overflow of radioactivity from superfused slices of prefrontal cortex of the rat, preincubated with [3H]DA in the presence of 1 microM desipramine, was examined. Apomorphine and the putative autoreceptor-selective DA agonist EMD 23 448 inhibited the K+-evoked overflow of radioactivity, while the DA antagonist sulpiride enhanced the evoked overflow in a dose-dependent and stereoselective manner. The latter effect was partially reversed by EMD 23 448. More than 95% of the radioactivity retained by the slices chromatographed with DA, while deaminated metabolites represented the majority of both the basal efflux (84% metabolites, 4-5% DA) and evoked overflow (84% metabolites, 14% DA) of radioactivity. These findings indicate that mesoprefrontal DA neurons possess release-modulating nerve terminal autoreceptors. Previous studies have shown that these neurons lack synthesis-modulating autoreceptors. Thus, autoreceptors on prefrontal DA terminals appear to be coupled to regulation of the release but not the synthesis of DA.  相似文献   
48.
A case-control study was conducted to test the hypothesis that chronic ingestion of trihalomethanes (THMs), occurring as chlorination byproducts in drinking water, carries a risk of colon cancer. Lifetime residential and water source histories and information on water-drinking habits, diet, sociodemographics, medical and occupation histories, lifestyle and other factors were obtained by questionnaire from a statewide sample of newly-diagnosed colon cancer cases (N = 347), controls with cancer of other sites (N = 639) and general population controls (N = 611). Since no data on past THM levels exists, it was necessary to devise a scheme to generate THM estimates for all Wisconsin water sources. For this, a statistical model based on quantitative THM measures and routinely-recorded data taken at 81 municipal water facilities was used in conjunction with individual residential histories to estimate lifetime and period-specific THM exposure for each case and control. Logistic regression was used to estimate odds ratios adjusted for age, sex and urban living, for colon cancer and THM exposure. The study results indicate that THM in Wisconsin drinking water does not pose a significant colon cancer risk. Odds ratios for exposure to the middle and highest category of lifetime cumulative THM were 1.05 (95% Cl = 0.66-1.68) and 0.93(95%Cl = 0.55-1.57) respectively, relative to the cancer control group, and 1.10 (95%Cl = 0.68-1.78) and 0.73 (95% Cl = 0.44-1.21) respectively, relative to the general population controls.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
49.
50.
Prior studies of alterations in tumor expression of normal blood group antigens and A9/alpha 6 beta 4 integrin, an extracellular matrix receptor, have suggested that these immunohistologic markers reflect the biologic aggressiveness of head and neck squamous carcinomas. To confirm these preliminary observations, prospective long-term follow-up of 82 previously untreated head and neck squamous carcinoma patients was performed. All patients were treated with conventional therapy. Median follow-up was 57 months. Tumor immunohistology for ABH blood group and A9/alpha 6 beta 4 integrin expression was performed and correlated with measures of host cellular immunity, disease-free survival, and overall survival. Loss of blood group expression and high A9/alpha 6 beta 4 integrin expression were each directly related to an increased frequency of early tumor recurrence. The combination of both variables was significantly associated with both disease-free (P = .029) and overall survival (P = .05). Increased expression of A9/alpha 6 beta 4 was associated with impaired T-lymphocyte function (P = .005), and loss of blood group expression was associated with decreased peripheral blood levels of CD8+ T-lymphocytes (P = .013). The findings suggest that these phenotypic characteristics of antigen expression in head and neck squamous carcinomas are important markers of biologically aggressive cancers and impaired host immune response. The clinical use of these biologic staging parameters in the initial assessment of patients should allow selection of more aggressive primary treatment strategies for individual patients.  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