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   3048篇
  免费   276篇
  国内免费   10篇
耳鼻咽喉   66篇
儿科学   86篇
妇产科学   48篇
基础医学   437篇
口腔科学   65篇
临床医学   362篇
内科学   634篇
皮肤病学   61篇
神经病学   306篇
特种医学   137篇
外科学   461篇
综合类   28篇
一般理论   3篇
预防医学   200篇
眼科学   141篇
药学   186篇
中国医学   7篇
肿瘤学   106篇
  2023年   25篇
  2022年   32篇
  2021年   94篇
  2020年   31篇
  2019年   70篇
  2018年   65篇
  2017年   61篇
  2016年   66篇
  2015年   54篇
  2014年   76篇
  2013年   92篇
  2012年   152篇
  2011年   149篇
  2010年   90篇
  2009年   80篇
  2008年   130篇
  2007年   144篇
  2006年   156篇
  2005年   141篇
  2004年   131篇
  2003年   122篇
  2002年   120篇
  2001年   102篇
  2000年   82篇
  1999年   77篇
  1998年   48篇
  1997年   38篇
  1996年   40篇
  1995年   20篇
  1994年   24篇
  1993年   19篇
  1992年   64篇
  1991年   53篇
  1990年   47篇
  1989年   48篇
  1988年   51篇
  1987年   42篇
  1986年   43篇
  1985年   42篇
  1984年   37篇
  1983年   36篇
  1982年   29篇
  1981年   16篇
  1980年   22篇
  1979年   23篇
  1978年   18篇
  1974年   18篇
  1973年   27篇
  1971年   24篇
  1969年   16篇
排序方式: 共有3334条查询结果,搜索用时 31 毫秒
71.
72.
73.
74.
75.
Breast carcinoma originating in cystosarcoma phyllodes   总被引:1,自引:0,他引:1  
Only three cases of carcinoma infiltrating the stroma of cystosarcoma phyllodes have been reported. An additional case is presented. Unlike the treatment of cystosarcoma phyllodes which is limited to complete removal of the tumor, carcinosarcomas should be treated in the same manner as carcinoma by mastectomy and axillary dissection.  相似文献   
76.
To further elucidate the role of proteases capable of cleaving N-terminal proopiomelanocortin (N-POMC)-derived peptides, we have cloned two cDNAs encoding isoforms of the airway trypsin-like protease (AT) from mouse (MAT) and rat (RAT), respectively. The open reading frames comprise 417 amino acids (aa) and 279 aa. The mouse AT gene was located at chromosome 5E1 and contains 10 exons. The longer isoform, which we designated MAT1 and RAT1, has a simple type II transmembrane protein structure, consisting of a short cytoplasmic domain, a transmembrane domain, a SEA (63-kDa sea urchin sperm protein, enteropeptidase, agrin) module, and a serine protease domain. The human homolog of MAT1 and RAT1 is the human AT (HAT). The shorter isoform, designated MAT2 and RAT2, which contains an alternative N terminus, was formerly described in the rat as adrenal secretory serine protease (AsP) and has been shown to be involved in the processing of N-POMC-derived peptides. In contrast to the long isoform, neither MAT2 and RAT2 (AsP) contain a transmembrane domain nor a SEA domain but an N-terminal signal peptide to direct the enzyme to the secretory pathway. The C terminus, covering the catalytic triad, is identical in both isoforms. Immunohistochemically, MAT/RAT was predominantly expressed in tissues of the upper gastrointestinal and the respiratory tract-but also in the adrenal gland. Moreover, isoform-specific RT-PCR and quantitative PCR analysis revealed a complex expression pattern of the two isoforms with differences between mice and rats. These findings indicate a multifunctional role of these proteases beyond adrenal proliferation.  相似文献   
77.
Our aim was to analyze the existing body of evidence about inpatient care of patients suffering from rheumatoid arthritis (RA). The report was induced by the executive board of the German Society of Rheumatology which assigned the "Oliver-Sangha committee" to dissect and point out the tasks of inpatient care during the next few years. A systemic search of the literature was performed covering the years 1966 to 2001. A total of 16 studies were selected and thoroughly appraised in a systematic way. Four randomized controlled trials addressing the question could be identified. All of them included only patients in a clinical condition allowing outpatient care as well. Two studies indicate some advantage of inpatient care in comparison to outpatient treatment. Two studies, both equivalence studies from design, reveal that RA patients do not generally experience additional benefit from hospitalization. Consideration of two additional cohort studies demonstrates the increased need of inpatient care in RA patients. None of the studies was derived from the German health care system. Emergency cases were not the subject of any of these trials. General statements about the value of inpatient care of RA patients can not be drawn from the analyzed studies. The committee makes suggestions for future investigations that may help to answer this important question considering the special circumstances of the German health care system.  相似文献   
78.
As the effects of anthropogenic climate change become more severe, several approaches for deliberate climate intervention to reduce or stabilize Earth’s surface temperature have been proposed. Solar radiation modification (SRM) is one potential approach to partially counteract anthropogenic warming by reflecting a small proportion of the incoming solar radiation to increase Earth’s albedo. While climate science research has focused on the predicted climate effects of SRM, almost no studies have investigated the impacts that SRM would have on ecological systems. The impacts and risks posed by SRM would vary by implementation scenario, anthropogenic climate effects, geographic region, and by ecosystem, community, population, and organism. Complex interactions among Earth’s climate system and living systems would further affect SRM impacts and risks. We focus here on stratospheric aerosol intervention (SAI), a well-studied and relatively feasible SRM scheme that is likely to have a large impact on Earth’s surface temperature. We outline current gaps in knowledge about both helpful and harmful predicted effects of SAI on ecological systems. Desired ecological outcomes might also inform development of future SAI implementation scenarios. In addition to filling these knowledge gaps, increased collaboration between ecologists and climate scientists would identify a common set of SAI research goals and improve the communication about potential SAI impacts and risks with the public. Without this collaboration, forecasts of SAI impacts will overlook potential effects on biodiversity and ecosystem services for humanity.  相似文献   
79.
BACKGROUND: A substantial proportion of patients with HIV infection will not respond to antiretroviral therapy. Early predictors of response to treatment are needed to identify patients who are at risk for treatment failure. OBJECTIVE: To determine predictors of virologic and clinical response to indinavir, zidovudine, and lamivudine therapy. DESIGN: Observational analysis of one treatment group in a phase III trial. SETTING: 40 AIDS Clinical Trials units. PATIENTS: 489 patients receiving indinavir, zidovudine, and lamivudine who had 1) a CD4 count of 0.200 x 10(9) cells/L or less after 8 or more weeks of study therapy and 2) plasma HIV-1 RNA measurements obtained at baseline and week 8. MEASUREMENTS: HIV-1 RNA level and CD4 cell count at weeks 0, 4, 8, 24, and 40. Clinical progression was defined as a new AIDS-defining illness or death. RESULTS: Patients' levels of HIV-1 RNA at the 8th study week of therapy predicted whether patients would achieve virologic suppression to below 500 (or 50) copies/mL at study week 24. An HIV-1 RNA level less than 500 copies/mL at week 24 was achieved in 71% of patients whose level at week 8 had been less than 500 copies/mL, 53% of those with a level of 500 copies/mL or more and at least 2-log(10) copies/mL reduction since baseline, 29% of those with a level of 500 copies/mL or more with a 1- to 1.99-log(10) copies/mL reduction, and 9% of those with a level of 500 copies/mL or greater and less than 1-log(10) copies/mL reduction since baseline (P < 0.001). HIV-1 RNA level at week 8 also predicted clinical progression. HIV-1 disease progressed in 2.2% of the patients with a week-8 HIV-1 RNA level less than 500 copies/mL, 2.3% of patients with 500 copies/mL or greater and at least 2-log(10) copies/mL reduction since baseline, 4.9% of patients with 500 copies/mL or greater and 1- to 1.99-log(10) copies/mL reduction since baseline, and 10.6% of patients with 500 copies/mL or greater and less than 1-log(10) copies/mL decrease since baseline (P = 0.009). After adjustment for HIV-1 RNA level, patients with a higher week-8 CD4 cell count were more likely to have a week-24 HIV-1 RNA level less than 500 copies/mL (relative risk for patients with a week-8 CD4 count >/= 0.10 x 10(9) cells/L, 1.47 [95% CI, 1.00 to 2.16] compared with <0.050 x 10(9) cells/L; relative risk for patients with a week-8 CD4 count of 0.05 to 0.099 x 10(9) cells/L, 0.98 [CI, 0.61 to 1.57] compared with <0.050 x 10(9) cells/L). After adjustment for HIV-1 RNA level, patients with a week-8 CD4 count of 0.05 x 10(9) cells/L or greater (compared with <0.05 x 10(9) cells/L) had a decreased hazard for clinical progression (hazard ratio, 0.25 [CI, 0.09 to 0.67]). CONCLUSIONS: The HIV-1 RNA level and CD4 cell count achieved at 8 weeks of treatment are important predictors of subsequent virologic and clinical outcomes.  相似文献   
80.

Context

Studies on multiple dimensions of the symptom experience of patients with gastrointestinal cancers are extremely limited.

Objective

Purpose was to evaluate for changes over time in the occurrence, severity, and distress of seven common symptoms in these patients.

Methods

Patients completed Memorial Symptom Assessment Scale, six times over two cycles of chemotherapy (CTX). Changes over time in occurrence, severity, and distress of pain, lack of energy, nausea, feeling drowsy, difficulty sleeping, and change in the way food tastes were evaluated using multilevel regression analyses. In the conditional models, effects of treatment group (i.e., with or without targeted therapy), age, number of metastatic sites, time from cancer diagnosis, number of prior cancer treatments, cancer diagnosis, and CTX regimen on enrollment levels, as well as the trajectories of symptom occurrence, severity, and distress were evaluated.

Results

Although the occurrence rates for pain, lack of energy, feeling drowsy, difficulty sleeping, and change in the way food tastes declined over the two cycles of CTX, nausea and numbness/tingling in hands/feet had more complex patterns of occurrence. Severity and distress ratings for the seven symptoms varied across the two cycles of CTX.

Conclusions

Demographic and clinical characteristics associated with differences in enrollment levels as well as changes over time in occurrence, severity, and distress of these seven common symptoms were highly variable. These findings can be used to identify patients who are at higher risk for more severe and distressing symptoms during CTX and to enable the initiation of preemptive symptom management interventions.  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