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   72696篇
  免费   5543篇
  国内免费   2102篇
耳鼻咽喉   1246篇
儿科学   1915篇
妇产科学   1227篇
基础医学   9833篇
口腔科学   723篇
临床医学   7103篇
内科学   10063篇
皮肤病学   628篇
神经病学   5074篇
特种医学   2524篇
外国民族医学   6篇
外科学   8270篇
综合类   9080篇
现状与发展   4篇
一般理论   1篇
预防医学   5190篇
眼科学   579篇
药学   7224篇
  36篇
中国医学   2193篇
肿瘤学   7422篇
  2024年   149篇
  2023年   1066篇
  2022年   1866篇
  2021年   2976篇
  2020年   2706篇
  2019年   2241篇
  2018年   2318篇
  2017年   2374篇
  2016年   2488篇
  2015年   2666篇
  2014年   4691篇
  2013年   5300篇
  2012年   4240篇
  2011年   4554篇
  2010年   3663篇
  2009年   3664篇
  2008年   3671篇
  2007年   3504篇
  2006年   3187篇
  2005年   2720篇
  2004年   2385篇
  2003年   2049篇
  2002年   1693篇
  2001年   1595篇
  2000年   1255篇
  1999年   1216篇
  1998年   1007篇
  1997年   920篇
  1996年   783篇
  1995年   757篇
  1994年   663篇
  1993年   522篇
  1992年   517篇
  1991年   449篇
  1990年   411篇
  1989年   362篇
  1988年   326篇
  1987年   294篇
  1986年   302篇
  1985年   421篇
  1984年   399篇
  1983年   257篇
  1982年   332篇
  1981年   255篇
  1980年   223篇
  1979年   215篇
  1978年   139篇
  1977年   108篇
  1976年   106篇
  1973年   61篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
This work was designed to study the proliferative response of tumor-associated lymphocytes (TAL) from neoplastic effusions against autologous tumor cells and the immunophenotype pattern of TAL from neoplastic effusions and that of PBMC of the same patients. We also compared the serum levels of the cytokines interleukin (IL) 1, 2 and 6, tumor necrosis factor- (TNF) and soluble IL-2 receptor (sIL-2R) with those present in neoplastic effusions of the same patients. Moreover, we examined the ability of TAL and peripheral blood mononuclear cells (PBMC) to produce and release the cytokines and sIL-2R and to express membrane CD25 following their stimulation with phytohemagglutinin (PHA) in vitro. Finally, we compared the cytokines/sIL-2R production and membrane CD25 expression by PHA-stimulated PBMC of the patients with neoplastic effusions with a series of 90 cancer patients without neoplastic effusions and 20 normal healthy subjects. Thirteen neoplastic pleural and eight peritoneal effusions were collected from 11 patients with primary lung cancer, 7 with primary epithelial ovarian cancer, 1 with breast cancer, 1 with pleural mesothelioma, and 1 with pancreatic cancer. The proliferative response of TAL from neoplastic effusions against autologous tumor cells was lower than the response to PHA, IL-2, and anti-CD3, but significant. The percentage distribution of CD3+ and CD8+ lymphocyte subpopulations was higher in peritoneal than in pleural effusions, while the CD16+ subset was higher in pleural than in peritoneal effusions. The percentage distribution of CD16+ was significantly lower in pleural effusions than in PBMC of patients with pleural effusions. The CD39 antigen was higher on TAL from peritoneal effusions than on PBMC of the same patients. The levels of IL-1 and sIL-2R in peritoneal effusions did not differ from those measured in the sera of the same patients, while the levels of IL-2, IL-6, and TNF were higher in the peritoneal effusions. The levels of IL-2, IL-6, TNF, and sIL-2R, but not IL-1, in pleural effusions were significantly higher than those found in the sera of the same patients. The amounts of IL-2 and IL-6 produced by TAL were generally higher than those released by PBMC. The secretion of cytokines IL-1, IL-2, and sIL2R by PHA-stimulated PBMC was lower, but IL-1 and IL-6 secretion was higher in cancer patients with neoplastic effusions than in either cancer patients without neoplastic effusions or normal subjects. The CD25 expression on PHA-stimulated PBMC derived from cancer patients with neoplastic effusions was in the same range as that of cancer patients without neoplastic effusions and normal subjects. These findings suggest that TAL may be able to produce cytokines and may be amenable to immune manipulation.Abbreviations FITC Fluorescein-isothiocyanate - IL Interleukin - mAb Monoclonal antibody - MHC Major histocompatibility complex - NK Natural killer - PBMC Peripheral blood mononuclear cells - PHA Phytohemagglutinin - TAL Tumor-associated lymphocytes - TIL Tumor-infiltrating lymphocytes - TNF Tumor necrosis factor- - sIL-2R Soluble interleukin-2 receptor  相似文献   
992.
We carried out a morphometric study on the myelinated fibers in the anterolateral funiculus (ALF) and lateral corticospinal tract (LCS) in the cervical segment of the spinal cord of 13 patients with classic amyotrophic lateral sclerosis (ALS), 6 of whom had been on a respirator: 5 age-matched subjects were used as controls. The results obtained revealed that: (1) the fiber-size distributions of the myelinated fibers in the ALF and LCS of the control subjects had peaks at 2 m; (2) there were marked and significant losses of large myelinated fibers in the ALF and LCS of ALS patients; (3) the patients who required respirator support showed more severe degeneration in the ALF than those who required none; and (4) the degree of myelinated fiber loss in the LCS did not correlate with either the illness duration or the history of respirator use.  相似文献   
993.
The effects of a combination regimen of metoprolol and 1-adrenoceptor agonist denopamine on resting and exercise heart rate have been studied in 10 normal volunteers. Maximal ramp upright bicycle exercise was performed three times at 1-week intervals. Two hours before each exercise test, 5 mg metoprolol plus 20 mg denopamine, 5 mg metoprolol plus a denopamine placebo, or two placebos were orally administered in a double-blind fashion.During exercise after placebo administration, heart rate increased in parallel with the exercise intensity. Compared to the placebo values, resting heart rate was significantly decreased by an average of 10 beats · min–1 by 5 mg metoprolol, whereas it was not altered by the combination regimen. During exercise, however, both the combination regimen and metoprolol alone showed a significant negative chronotropic effect, decreasing peak exercise heart rate by an average of 14 and 21 beats · min–1, respectively. Peak oxygen uptake was also significantly decreased by both regimens.We conclude that concomitant administration of 5 mg metoprolol and 20 mg denopamine exerts an effective -adrenoceptor blocking action during exercise but a minimal effect at rest in normal subjects. The combination regimen appears to have a favourable pharmacological profile for -adrenoceptor blocker therapy in patients with chronic heart failure.  相似文献   
994.
995.
T-lymphocytes expressing T -cell receptors (TCRs) of the / type have been suggested to play an important role in mucosal defense against infection and neoplastic transformation. In this study, an immunohistochemical investigation was performed on the distribution of / and / TCRs among tumor-infiltrating lymphocytes. Thirteen patients with squamous cell carcinomas of the upper aerodigestive tract were studied, using monoclonal antibodies and an avidin-biotin-peroxidase technique. Most of the T-cells had an / TCR. Only 1.6% of the T-cells within the cancer tissue and 1.2% of the T-cells in the parenchyma adjacent to the cancer tissue expressed /gd TCRs. These results are consistent with the results of similar studies in bronchial and breast carcinomas. Biopsies from normal oral mucosa in nine healthy individuals showed that 1.3% of the T -cells within the epithelium and 1.0% of those in the lamina propria adjacent to the epithelium expressed / TCRs. Quantitatively the results do not support the theory that / T-cells play an important role in the immunological response against cancer tissue in the mucosa of the upper aerodigestive tract. The functional role of these cells in the mucosa and in response to carcinomas is, however, still uncertain.  相似文献   
996.
Objectives: To examine physician responses to suspected prenatal substance exposure and the reasons underlying these responses. Methods: National mail survey of practicing obstetricians and pediatricians who see neonates. Response rate: 63%. Results: More than 70% of physicians reported having ever suspected prenatal substance exposure. Response rates did not vary by specialty. Twenty-seven percent reported that they had never suspected prenatal substance exposure. The most common lifetime pattern (60%) was some response whenever prenatal substance exposure was suspected; next most common was no suspicion (27%). Just over 10% had a discretionary response: acting in some cases of suspected prenatal substance exposure but ignoring others. Two percent consistently ignored their suspicions. Getting help for the patient and protecting the fetus were the most common reasons to act. Among those who had ignored their suspicions, lack of sufficient evidence of substance use was the most often cited reason. There were some important specialty differences in reasons for response and non-response and in specific responses likely to be taken. Obstetricians are far more likely to provide the patient with information and get a substance use history; pediatricians are more inclined to involve outsiders. Conclusions: Obstetricians and pediatricians seem quite willing to act on their suspicions of prenatal substance exposure, and generally respond by taking positive actions. Specialty differences are few and reflect practice differences.  相似文献   
997.
AS_2O_3对消化道肿瘤细胞凋亡作用的研究   总被引:4,自引:0,他引:4  
目的研究AS3O3对10种消化道肿瘤细胞株的致凋亡作用。方法采用形态学观察、流式细胞仪检测及DNA电泳分析。结果发现两株细胞经AS2O3作用后有明显凋亡,三株细胞无凋亡,其余有少量凋亡。结论AS2O3对不同的消化道肿瘤细胞有不同的作用,提示AS2O3对不同细胞的致凋亡作用可能存在不同的机理。  相似文献   
998.
999.
Oesophageal pressure (Pes) measurements are important in medical research and useful in clinical diagnosis. Measurements, however, are contaminated heavily by cardiac artifacts. The spectrum and waveform of the Pes signal is obtained from the oesophageal balloon. Adaptive finite impulse response (AFIR) filter and modified adaptive noise cancellation (MANC) methods are adopted to filter out cardiac beat interference. These results are compared. In the frequency domain, frequency variations and spectral overlap between the Pes components and cardiac beat signal components impact on the performance of the filter. From our experimental results on power strength, the fourth or higher harmonics did not have any significant effect on the filter performance. However, the second harmonics of these signals had a significant effect on the filtering result. Thus, in the design of AFIR filters, attention is needed to minimise these effects. In frequency analysis, these harmonics or overlapping frequencies do not affect MANC. MANC was the better method for eliminating cardiac beat artifact in Pes measurement. The dynamic compliance (Cdyn) was also used to evaluate the performance of MANC and AFIR. The standard deviation of Cdyn was less than 0.15 using MANC, compared with standard deviations as high as 0.57 for AFIR. We conclude that MANC performs better than AFIR.  相似文献   
1000.
纤维胆道镜在肝内胆管结石手术治疗中的应用价值   总被引:1,自引:0,他引:1  
目的:探讨纤维胆道镜在肝内胆管结石的外科手术治疗中的临床应用价值。方法:对我院1984 年11 月~1998 年6 月间术后用胆道镜取石治疗肝内胆管残余结石233 例作回顾性分析。结果:取净结石210 例(90.1% );23 例残石未取净(9.9% ),其中中转手术3 例(1.3% )。影响术后胆道镜取石疗效的主要因素,包括手术时机、手术中是否作胆道镜检查、残留结石大小和嵌顿与否,以及肝内胆管是否狭窄。结论:在肝内胆管结石的外科手术治疗中,纤维胆道镜(包括术中和术后胆道镜)具有相当重要的临床应用价值,但不能完全替代手术切除病肝  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