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   3740篇
  免费   242篇
  国内免费   12篇
耳鼻咽喉   98篇
儿科学   77篇
妇产科学   17篇
基础医学   580篇
口腔科学   80篇
临床医学   276篇
内科学   995篇
皮肤病学   169篇
神经病学   249篇
特种医学   138篇
外科学   499篇
综合类   19篇
预防医学   113篇
眼科学   70篇
药学   293篇
中国医学   8篇
肿瘤学   313篇
  2022年   38篇
  2021年   66篇
  2020年   29篇
  2019年   46篇
  2018年   83篇
  2017年   60篇
  2016年   53篇
  2015年   68篇
  2014年   98篇
  2013年   94篇
  2012年   154篇
  2011年   173篇
  2010年   101篇
  2009年   101篇
  2008年   152篇
  2007年   179篇
  2006年   176篇
  2005年   186篇
  2004年   165篇
  2003年   156篇
  2002年   149篇
  2001年   152篇
  2000年   130篇
  1999年   123篇
  1998年   42篇
  1997年   30篇
  1996年   26篇
  1995年   37篇
  1994年   24篇
  1992年   85篇
  1991年   93篇
  1990年   65篇
  1989年   64篇
  1988年   56篇
  1987年   57篇
  1986年   48篇
  1985年   58篇
  1984年   41篇
  1983年   23篇
  1982年   26篇
  1979年   39篇
  1978年   24篇
  1977年   23篇
  1972年   32篇
  1971年   36篇
  1970年   46篇
  1969年   33篇
  1968年   33篇
  1967年   27篇
  1966年   33篇
排序方式: 共有3994条查询结果,搜索用时 15 毫秒
1.
On the basis of data showing a bimodal distribution of values for extracellular pH (pHe), and a discontinuous delta PCO2/delta lactate relationship, Kraig et al. (1986) proposed that H+ is grossly compartmentalized between neurons and glia in the ischemic brain. We measured delta pHe during ischemia, varying ischemic lactate contents between 9 and 38 mmol kg-1. No bimodal distribution was found, but delta pHe varied linearly with lactate content. Because we have also failed to record a discontinuous delta PCO2/delta lactate relationship, we conclude that major compartmentation of H+ does not occur during ischemia.  相似文献   
2.
Bilateral cervical lymph node dissection was performed in 71 cases of papillary thyroid carcinoma, considered to be relatively early cases because of mobility, irrespective of the size of tumor or presence of node enlargement. Of these, 33 cases received additional node dissection of the anterosuperior mediastinum through longitudinal sternotomy. The number of lymph nodes examined per subject averaged 89.9, the number of metastatic nodes was 13.8, and metastasis was noted in 88.7% of all cases. Lymph node metastasis tended to be more frequent on the affected side, but was simultaneously scattered over the whole cervical area. As to sites, metastasis of paratracheal nodes on the affected side occurred at a frequency of 66.2%, inferior and superior jugular nodes at 62.0% and 59.0% respectively, pretracheal nodes at 50.7%, and tracheoesophageal nodes at 47.9%. The high incidence of para- and pretracheal nodes suggests that the lymph flow in this direction is of great importance in metastasis. In fact, lymph nodes in the mediastinum, which were directly continuous with these nodes, showed as high as 39.4% metastasis in cases of anterosuperior mediastinal extirpation. This extensive node dissection is considered to be very preferable as at least the agony of survival with carcinoma can be lessened.  相似文献   
3.
4.
A series of 8 rat and 16 mouse invasive bladder carcinomas were investigated for the presence of silverstained nucleolar organizer regions (AgNORs) to clarify whether this parameter is applicable to the estimation of their invasive character. With regard to number of AgNORs per cell, neither rat nor mouse carcinomas showed any difference between invasive and noninvasive sites within the same tumor. However, the frequency of cancer cells bearing bizarre dots, irregular in size and shape, was significantly higher at sites of actual invasion. Quantitative data generated using an image analyzer revealed significantly lower values for NOR roundness and significantly larger NOR size in invasive sites than in noninvasive sites in all groups. Double staining for the proliferation marker proliferating cell nuclear antigen (PCNA) and AgNORs was performed on eight rat carcinomas and a close correlation between the two was confirmed. Thus the number of AgNORs in PCNA-positive cells was significantly greater than in PCNA-negative cells. Furthermore, a particularly strong correlation was observed for incidences of PCNA-positive cells and bizarre dots (P<0.01). The quantitative data also demonstrated significant differences in size and shape of dots. It is concluded that AgNORs have diagnostic value for the invasive character of bladder carcinomas.  相似文献   
5.
6.
Carbon fibers with fibrin glue were used as electrodes for diaphragm pacing. The electrodes were applied to three mongrel dogs and the effectiveness was tested. The carbon leads were glued to phrenic nerves by means of the fibrinogen and thrombin bilaterally. The tidal volumes and threshold current level for stimulation were measured at various time up to 9 weeks after implantation. Effective contraction of diaphragm were observed for 9 weeks. By using this electrode, the exfoliation of the nerve is not necessary, the nerve can be maintained in an intact state, and the risk of the implanting operation can be minimized.  相似文献   
7.
The current study investigates the effect of megestrol acetate, a synthetic progestin, on the activity of interleukin-1. Murine thymocytes were suspended in vitro and stimulated with varying concentrations of interleukin-1. [3H]Thymidine uptake was observed as an index of thymocyte proliferation. A dose-dependent increase in [3H]thymidine uptake was observed with increasing concentrations of interleukin-1. When megestrol acetate was added to the solution, a marked suppressive effect was observed. Higher doses of megestrol acetate had a greater suppressive effect on thymocyte proliferation. Additional investigation is required to further delineate the potential systemic effects of megestrol acetate.  相似文献   
8.
Employing HPLC fluorometry, gas-liquid chromatography (GLC) and a novel enzymelinked immunosorbent assay (ELISA) based on a monoclonal antibody, 40 corn samples, each collected in 1993 from agricultural stocks for human consumption in Haimen (Jiangsu County) and Penlai (Shandong Province), high- and low-risk areas for primary liver cancer (PLC) in China, respectively, were analysed for fumonisins (FBs), aflatoxins (AFs) and trichothecenes. Levels and positive rates of FBs and deoxynivalenol (DON) were significantly higher in Haimen than in Penlai. ELISA of the 40 corn samples harvested in the two areas in 1994 revealed that FB contamination levels and rates in these areas were comparable to those observed in 1993 in Haimen. ELISA analysis of 1993 and 1994 products revealed a wide occurrence of AFB1 but the positive rates as well as levels were not significantly different between these areas. ELISA of the same sample number of corn harvested in 1995 revealed that FB contamination in Haimen was significantly higher than in Penlai. These 3-yearly surveys of corn samples (240 in total) demonstrated that corn harvested in Haimen was highly contaminated with FBs and that the contamination level, as well as positive rate in 1993 and 1995, were 10–50-fold higher than those in Penlai, suggesting FBs as a risk factor for promotion of PLC in endemic areas, along with the trichothecene DON. Co-contamination with AFs, potent hepatocarcinogens, was assumed to play an important role in the initiation of hepatocarcinogenesis.  相似文献   
9.
H Koyama  K Nishimura  T Mio  A Ikeda  N Sugiura    T Izumi 《Thorax》1994,49(6):540-544
BACKGROUND--Diffuse panbronchiolitis (DPB) is characterised clinically by chronic airflow limitation and respiratory tract infection, and pathologically by chronic bronchiolar inflammation. To elucidate the functional differences between chronic obstructive pulmonary disease (COPD) and DPB the bronchial responsiveness to methacholine was compared in 64 patients with COPD and 32 patients with DPB, and the bronchodilator response was compared in 72 patients with COPD and 49 with DPB. METHODS--Bronchial responsiveness to methacholine was determined by the dosimeter method and expressed as PD20FEV1, and bronchodilator response was measured as the change in percentage predicted response with 5 mg nebulised salbutamol. RESULTS--Baseline FEV1 was similar in the two groups of patients. Patients with COPD were more responsive to methacholine than were those with DPB (geometric mean PD20FEV1 8.87 v 48.0 cumulative units). Reversibility of air flow obstruction, expressed as the difference between the percentage predicted postbronchodilator FEV1 and prebronchodilator FEV1, was significantly larger in patients with COPD than in those with DPB (7.87 (6.52)% v 4.16 (4.43)%). CONCLUSIONS--The observation that patients with DPB differ substantially in bronchial responsiveness from those with COPD is thought to reflect the difference in the mechanisms of these two diseases--that is, airway disease in DPB and more parenchymal disease in the group of patients with COPD. The nature of bronchiolar inflammation in COPD and DPB is also different, possibly explaining the difference in bronchial responsiveness. More fixed airflow limitation as a result of structural bronchiolar lesions in DPB will explain the smaller reversibility of airflow obstruction.  相似文献   
10.
A case of repeated episodes of hypoventilatory respiratory failure accompanied with primary hypothyroidism was reported. A 76-year-old woman was admitted to our hospital due to both disturbance of consciousness and respiratory failure. A diagnosis of primary hypothyroidism complicated with hypoventilatory respiratory failure deterioration due to respiratory infection was made. Supplemental therapy of thyroid hormones improved her general condition, but respiratory failure recurred after interruption of a replacement drug. Cases of unexplained respiratory failure should be differentiated from respiratory failure induced by hypothyroidism.  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