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   2825篇
  免费   173篇
  国内免费   27篇
耳鼻咽喉   2篇
儿科学   173篇
妇产科学   43篇
基础医学   308篇
口腔科学   81篇
临床医学   227篇
内科学   694篇
皮肤病学   50篇
神经病学   90篇
特种医学   507篇
外科学   312篇
综合类   43篇
预防医学   196篇
眼科学   29篇
药学   106篇
中国医学   8篇
肿瘤学   156篇
  2023年   9篇
  2022年   30篇
  2021年   35篇
  2020年   36篇
  2019年   49篇
  2018年   68篇
  2017年   45篇
  2016年   51篇
  2015年   63篇
  2014年   62篇
  2013年   101篇
  2012年   77篇
  2011年   85篇
  2010年   112篇
  2009年   91篇
  2008年   90篇
  2007年   98篇
  2006年   109篇
  2005年   83篇
  2004年   73篇
  2003年   63篇
  2002年   72篇
  2001年   58篇
  2000年   59篇
  1999年   66篇
  1998年   139篇
  1997年   123篇
  1996年   132篇
  1995年   93篇
  1994年   75篇
  1993年   86篇
  1992年   31篇
  1991年   33篇
  1990年   31篇
  1989年   70篇
  1988年   52篇
  1987年   54篇
  1986年   67篇
  1985年   52篇
  1984年   29篇
  1983年   39篇
  1982年   37篇
  1981年   24篇
  1980年   36篇
  1979年   15篇
  1978年   19篇
  1977年   21篇
  1976年   23篇
  1975年   27篇
  1970年   6篇
排序方式: 共有3025条查询结果,搜索用时 15 毫秒
61.
OBJECTIVE: To identify risk factors that are associated with the development of scar endometriosis after obstetric hysterotomies. The hypothesis is that early hysterotomy in pregnancy (before 22nd week) is the main risk factor for the development of scar endometriosis. METHODS: The authors conducted a case-control study between April 2000 and June 2003. A total of 117 women were selected, including 39 cases and 78 controls. Exposure and confounding variables were measured by a standardized questionnaire, which included sociodemographic characteristics, reproductive/physiologic history, past pathological history, history of obstetric surgeries, family history, and social history. The odds ratio (OR) and its 95% confidence interval (CI) were calculated using bivariate analysis for each possible risk factor. These estimates were obtained by multivariate analysis using unconditional logistic regression. Tests were made to assess the fit of the final model. RESULTS: In the multivariate analysis, positive associations were observed between scar endometriosis and hysterotomy type (early versus late: OR = 42.99; CI 8.77-210.81), amount of the menstrual blood flow (heavy versus light/normal: OR = 11.97; CI 2.35-60.82), and alcoholic consumption (yes versus no: OR = 5.31; CI 1.22-23.11). Negative association was observed between scar endometriosis and parity (OR = 0.61; CI 0.31-1.23), however it was not statistically significant (p>0.05). CONCLUSIONS: Early hysterotomy in pregnancy is the main risk factor for scar endometriosis. Increased menstrual flow and alcohol consumption are also risk factors, while high parity may be a protecting factor.  相似文献   
62.
Staphylococcus epidermidis has emerged as the most important pathogen in infections related to indwelling medical devices, and although these infections are not life-threatening, their frequency and the fact that they are extremely difficult to treat represent a serious burden on the public health system. Treatment is complicated by specific antibiotic resistance genes and the formation of biofilms. Hence, novel therapeutic strategies are needed to fight these infections. A novel bacteriophage CUB-EPI_14 specific to the bacterial species S. epidermidis was isolated from sewage and characterized genomically and phenotypically. Its genome contains a total of 46,098 bp and 63 predicted genes, among which some have been associated with packaging and lysis-associated proteins, structural proteins, or DNA- and metabolism-associated proteins. No lysogeny-associated proteins or known virulence proteins were identified in the phage genome. CUB-EPI_14 showed stability over a wide range of temperatures (from −20 °C to 50 °C) and pH values (pH 3–pH 12) and a narrow host range against S. epidermidis. Potent antimicrobial and antibiofilm activities were observed when the phage was tested against a highly susceptible bacterial isolate. These encouraging results open the door to new therapeutic opportunities in the fight against resilient biofilm-associated infections caused by S. epidermidis.  相似文献   
63.
64.
The permanent ice cover of Lake Vida (Antarctica) encapsulates an extreme cryogenic brine ecosystem (−13 °C; salinity, 200). This aphotic ecosystem is anoxic and consists of a slightly acidic (pH 6.2) sodium chloride-dominated brine. Expeditions in 2005 and 2010 were conducted to investigate the biogeochemistry of Lake Vida’s brine system. A phylogenetically diverse and metabolically active Bacteria dominated microbial assemblage was observed in the brine. These bacteria live under very high levels of reduced metals, ammonia, molecular hydrogen (H2), and dissolved organic carbon, as well as high concentrations of oxidized species of nitrogen (i.e., supersaturated nitrous oxide and ∼1 mmol⋅L−1 nitrate) and sulfur (as sulfate). The existence of this system, with active biota, and a suite of reduced as well as oxidized compounds, is unusual given the millennial scale of its isolation from external sources of energy. The geochemistry of the brine suggests that abiotic brine-rock reactions may occur in this system and that the rich sources of dissolved electron acceptors prevent sulfate reduction and methanogenesis from being energetically favorable. The discovery of this ecosystem and the in situ biotic and abiotic processes occurring at low temperature provides a tractable system to study habitability of isolated terrestrial cryoenvironments (e.g., permafrost cryopegs and subglacial ecosystems), and is a potential analog for habitats on other icy worlds where water-rock reactions may cooccur with saline deposits and subsurface oceans.  相似文献   
65.
Tumor angiogenesis pathways have been identified as important therapeutic targets in non-small cell lung cancer. However, no biomarkers have been described as predictors of response to antiangiogenic therapy in these patients. In this study, plasma levels of VEGF, bFGF, E-selectin, and S-ICAM and gene expression profiles of peripheral blood mononuclear cells from non-small cell lung cancer patients treated with chemotherapy plus bevacizumab were analyzed before and after treatment. Values were correlated with clinicopathological characteristics and treatment response. Plasma factor levels were measured using commercially available ELISA kits. The TaqMan® human angiogenesis array was used to investigate the effect of treatment on gene expression profiles. Kyoto Encyclopedia of Genes and Genomes and Gene Ontology enrichment analysis was performed for differentially expressed genes using WEB-based GEne SeT AnaLysis Toolkit. Our results suggest a benefit for patients with increased plasma levels of VEGF, E-selectin, and S-ICAM in the course of bevacizumab treatment. Also, we identified differentially expressed genes between paired blood samples from patients before and after treatment, and significantly perturbed pathways were predicted. These changes in gene expression and levels of plasma factors could be used to assess the effectiveness of antiangiogenic therapy, in addition to standard clinical and radiological evaluations.  相似文献   
66.
67.
The elbow joint is a complex joint, which, when impaired in function, leads to severe disability. In some cases however, an arthroplasty might be an appropriate treatment. In the past four decades, large steps havebeen taken to optimize this treatment in order to achieve better post-operative outcomes. To understand these progresses and to discover aspects for upcoming improvements, we present a review on the past developments, the present state of affairs and future developments which may improve patient care further.  相似文献   
68.
69.
70.
Gay  JC; Beckman  JK; Brash  AR; Oates  JA; Lukens  JN 《Blood》1984,64(4):780-785
Leukotriene B4 (LTB4) is a potent primary stimulator of neutrophil chemotaxis, aggregation, and degranulation and induces superoxide production at higher concentrations. In order to determine whether LTB4 modulates neutrophil responses to oxidative stimuli, human neutrophils (PMNs) were incubated with LTB4 prior to stimulation with f-Met-Leu-Phe (fMLP, 10(-7) mol/L), opsonized zymosan (OZ, 250 micrograms/mL), or phorbol myristate acetate (PMA, 32 nmol/L). Superoxide (O2-) production by stimulated PMNs was assessed by the superoxide dismutase-inhibitable reduction of cytochrome c. LTB4 alone did not stimulate O2- production in concentrations below 10(-7) mol/L and had no effect on the O2- assay. In the concentration range of 10(-12) to 10(-8) mol/L, LTB4 did not alter O2- release induced by OZ or PMA. In contrast, LTB4-treated cells demonstrated enhanced O2- production following exposure to fMLP, and in the presence of 10 nmol/LLTB4, generated 180% +/- 41% of O-2 quantities produced by control cells (n = 23). Enhancement was LTB4 dose-dependent, was maximal in the range of 1 to 10 nmol/L LTB4, was not reversed by removal of the lipid from the medium prior to fMLP stimulation, and was not dependent on the presence of Ca++ or Mg++ in the suspending medium. Chemiluminescence of fMLP-stimulated neutrophils was increased to 323% of controls in neutrophils preincubated with 10 nmol/L LTB4. Unlike augmentation of oxidative responses to fMLP seen with other degranulating stimuli, enhancement by LTB4 was not correlated with an increase in 3H-fMLP receptor binding. These results indicate that, in addition to its primary effects on neutrophil function, LTB4 modulates PMN oxidative responses to the chemotactic peptide and, thus, may amplify the release of oxygen metabolites at inflammatory foci.  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