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   2794篇
  免费   218篇
  国内免费   4篇
耳鼻咽喉   12篇
儿科学   117篇
妇产科学   61篇
基础医学   370篇
口腔科学   131篇
临床医学   257篇
内科学   669篇
皮肤病学   60篇
神经病学   195篇
特种医学   49篇
外科学   460篇
综合类   10篇
预防医学   244篇
眼科学   42篇
药学   153篇
中国医学   9篇
肿瘤学   177篇
  2023年   19篇
  2022年   44篇
  2021年   78篇
  2020年   34篇
  2019年   72篇
  2018年   105篇
  2017年   55篇
  2016年   60篇
  2015年   83篇
  2014年   106篇
  2013年   119篇
  2012年   176篇
  2011年   179篇
  2010年   125篇
  2009年   99篇
  2008年   150篇
  2007年   138篇
  2006年   148篇
  2005年   171篇
  2004年   124篇
  2003年   134篇
  2002年   135篇
  2001年   71篇
  2000年   72篇
  1999年   75篇
  1998年   26篇
  1997年   17篇
  1996年   13篇
  1994年   17篇
  1993年   8篇
  1992年   30篇
  1991年   31篇
  1990年   30篇
  1989年   21篇
  1988年   15篇
  1987年   23篇
  1986年   20篇
  1985年   19篇
  1984年   12篇
  1982年   11篇
  1981年   6篇
  1980年   8篇
  1979年   11篇
  1978年   7篇
  1977年   9篇
  1976年   14篇
  1975年   6篇
  1974年   9篇
  1973年   6篇
  1968年   6篇
排序方式: 共有3016条查询结果,搜索用时 15 毫秒
91.

OBJECTIVES:

Myeloid-derived suppressor cells contribute to the immunosuppressive microenvironment during tumor development and limit the efficacy of cancer immunotherapy. Identifying myeloid-derived suppressor cells and associated factors is the first step in creating strategies to reverse the suppressive effects of these cells on the immune system.

METHODS:

To induce lung cancer, we administered 2 doses of urethane to BALB/c mice and observed these animals for 120 days. After this period, we evaluated the percentage of myeloid-derived suppressor cells in the blood, lung and bone marrow. The expression of alpha-smooth muscle actin, transforming growth factor-β, Toll-like receptor 2, Toll-like receptor 4, and interleukin-6 was also determined in the lung tissue.

RESULTS:

Myeloid-derived suppressor cells were increased in all evaluated tissues after lung cancer development in association with increased Toll-like receptor 4 expression and decreased interleukin-6 expression in the lung. We observed alpha-smooth muscle actin and transforming growth factor-β expression in lung nodules.

CONCLUSIONS:

We believe that the early diagnosis of cancer through determining the blood levels of myeloid-derived suppressor cells followed by the depletion of these cells should be further investigated as a possible approach for cancer treatment.  相似文献   
92.
93.
The aims of this study were to determine the presence of respiratory syncytial virus (RSV) and to assess the clinical features of the disease in infants with acute low respiratory tract infection hospitalized at pediatric intensive care units (PICU) of two university teaching hospitals in S?o Paulo State, Brazil. Nasopharyngeal secretions were tested for the RSV by the polymerase chain reaction. Positive and negative groups for the virus were compared in terms of evolution under intensive care (mechanical pulmonary ventilation, medications, invasive procedures, complications and case fatality). Statistical analysis was performed using the Mann Whitney and Fisher's exact tests. A total of 21 infants were assessed, 8 (38.1%) of whom were positive for RSV. The majority of patients were previously healthy while 85.7% required mechanical pulmonary ventilation, 20/21 patients presented with at least one complication, and the fatality rate was 14.3%. RSV positive and negative groups did not differ for the variables studied. Patients involved in this study were critically ill and needed multiple PICU resources, independently of the presence of RSV. Further studies involving larger cohorts are needed to assess the magnitude of the impact of RSV on the clinical evolution of infants admitted to the PICU in our settings.  相似文献   
94.
Analysis of impurities is an important step in the quality control of pharmaceutical ingredients and final products. From drug synthesis or excipients, even in small concentrations, impurities may affect efficacy and safety. The method was developed following Quality by Design (QbD) for the analysis of the antidiabetic empagliflozin. The concept of QbD is used as a tool for the development of methods and formulations. Through predefined objectives and risk analysis, robust methodologies and reduced solvent consumption are developed. A simple HPLC method was developed and validated for the quantitative determination of empagliflozin and its organic impurities from the synthesis process. The method was carried out in a Shim-pack phenyl column with a mobile phase consisting of an acetonitrile/water mixture (72 : 28), with isocratic elution and the detector wavelength was 230 nm. The validation process, in accordance with international guidelines, shows that the method was linear, precise and accurate for empagliflozin, impurity 1 and impurity 2. Limits of detection (0.01, 0.02 and 0.01 μg mL−1) and quantification (0.10, 0.10 and 0.05 μg mL−1) were determined for EMPA, IMP1 and IMP2, respectively. The HPLC method for impurity determination in empagliflozin was linear, precise, accurate and robust. It can be successfully applied in the quality control of empagliflozin and the synthesis of impurities, being adequate for routine analysis.

Analysis of impurities is an important step in the quality control of pharmaceutical ingredients and final products.  相似文献   
95.
96.
Vascularized composite tissue allotransplantation is a viable treatment option for injuries and defects that involve multiple layers of functional tissue. In the past 15 yr, more than 150 vascularized composite allotransplantation (VCA) surgeries have been reported for various anatomic locations including – but not limited to – trachea, larynx, abdominal wall, face, and upper and lower extremities. VCA can achieve a level of esthetic and functional restoration that is currently unattainable using conventional reconstructive techniques. Although the risks of lifelong immunosuppression continue to be an important factor when evaluating the benefits of VCA, reported short‐ and long‐term outcomes have been excellent, thus far. Acute rejections are common in the early post‐operative period, and immunosuppression‐related side effects have been manageable. A multidisciplinary approach to the management of VCA has proven successful. Reports of long‐term graft losses have been rare, while several factors may play a role in the pathophysiology of chronic graft deterioration in VCA. Alternative approaches to immunosuppression such as cellular therapies and immunomodulation hold promise, although their role is so far not defined. Experimental protocols for VCA are currently being explored. Moving forward, it will be exciting to see whether VCA‐specific aspects of allorecognition and immune responses will be able to help facilitate tolerance induction.  相似文献   
97.
In this prospective study we analyzed pretransplant interferon‐γ secretion by cytomegalovirus (CMV)‐specific CD8+ T cells to assess its possible utility in determining the risk of CMV replication after solid organ transplantation. A total of 113 lung and kidney transplant patients were enrolled in the study but only 55 were evaluable. All CMV‐seronegative recipients were pretransplant “nonreactive” (IFNγ <0.2 IU/mL) (11/11), whereas 30/44 (68.2%) CMV‐seropositive (R+) recipients were “reactive” (IFNγ ≥0.2 IU/mL) and 14/44 (31.8%) were “nonreactive”. In the R(+) “nonreactive” group, 7/14 (50%) developed posttransplant CMV replication, whereas the virus replicated only in 4/30 (13.3%) of the R(+) “reactive” patients (p = 0.021). According to the best multivariate model, pretransplant “nonreactive” recipients receiving an organ from a CMV‐seropositive donor had a 10‐fold increased risk of CMV replication compared to pretransplant “reactive” recipients (adjusted OR 10.49, 95% CI 1.88–58.46). This model displayed good discrimination ability (AUC 0.80) and calibration (Hosmer–Lemeshow test, p = 0.92). Negative and positive predictive values were 83.7% and 75%, respectively. The accuracy of the model was 82%. Therefore, assessment of interferon‐γ secretion by cytomegalovirus (CMV)‐specific CD8+ T cells prior to transplantation is useful in informing the risk of posttransplant CMV replication in solid organ transplant patients.  相似文献   
98.
99.
International Journal of Mental Health and Addiction - The presence of COVID-19 has had psychological consequences among health personnel; these include fear, anxiety, and depression. In the...  相似文献   
100.

Introduction and hypothesis

Complications of pelvic organ prolapse and urinary incontinence surgery have gained increasing attention from both lay media and medical societies. The International Urogynecological Association and International Continence Society proposed the category–time–site system to classify complications in 2011. Our objective is to assess the usage of the category–time–site system in the literature.

Methods

We conducted a systematic review and identified records using PubMed search terms “mesh” and “prolapse or incontinence” and “complication or excision” (February 2011 to December 2015) to select publications following the introduction of category–time–site system. Relevant publications were included and reviewed for study design, initial procedure, number of patients assigned codes, number of unique codes applied, purpose of assigning codes, and duration of clinical follow-up.

Results

Of 167 eligible records, 23 (14 %) used the system, 137 (82 %) used no system, and 7 (4 %) used another system. They included three study designs: randomized control trials, case reports, and case series. Given the very limited amount of data, no statistical tests were performed, but trends were noted.

Conclusions

Fourteen percent of the reports in the literature describing complications related to prosthesis/graft use in pelvic surgery utilize the category–time–site system. The system’s limited and inconsistent use hinders the ability to draw conclusions useful for clinical practice. Effort should be directed toward improving appropriate usage or revising the system to increase its exposure in related publications. An improved system will better prepare pelvic surgeons for assessing future generations of prostheses/grafts.
  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