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   11439篇
  免费   864篇
  国内免费   20篇
耳鼻咽喉   172篇
儿科学   478篇
妇产科学   233篇
基础医学   1651篇
口腔科学   263篇
临床医学   1353篇
内科学   2008篇
皮肤病学   157篇
神经病学   1027篇
特种医学   326篇
外国民族医学   3篇
外科学   1259篇
综合类   107篇
一般理论   15篇
预防医学   1541篇
眼科学   132篇
药学   735篇
中国医学   19篇
肿瘤学   844篇
  2023年   88篇
  2022年   92篇
  2021年   347篇
  2020年   216篇
  2019年   332篇
  2018年   328篇
  2017年   270篇
  2016年   260篇
  2015年   304篇
  2014年   427篇
  2013年   579篇
  2012年   848篇
  2011年   840篇
  2010年   411篇
  2009年   427篇
  2008年   664篇
  2007年   722篇
  2006年   653篇
  2005年   682篇
  2004年   584篇
  2003年   530篇
  2002年   457篇
  2001年   160篇
  2000年   155篇
  1999年   136篇
  1998年   105篇
  1997年   78篇
  1996年   56篇
  1995年   76篇
  1994年   48篇
  1993年   41篇
  1992年   88篇
  1991年   81篇
  1990年   84篇
  1989年   78篇
  1988年   57篇
  1987年   56篇
  1986年   71篇
  1985年   55篇
  1984年   48篇
  1983年   44篇
  1982年   40篇
  1981年   41篇
  1980年   46篇
  1979年   54篇
  1978年   48篇
  1977年   54篇
  1974年   46篇
  1972年   53篇
  1970年   41篇
排序方式: 共有10000条查询结果,搜索用时 734 毫秒
11.
12.
PURPOSE: This study aims to determine the effect of loss of breast cancer metastasis suppressor 1 (BRMS1) protein expression on disease-free survival in breast cancer patients stratified by estrogen receptor (ER), progesterone receptor (PR), or HER2 status, and to determine whether loss of BRMS1 protein expression correlated with genomic copy number changes. EXPERIMENTAL DESIGN: A tissue microarray immunohistochemical analysis was done on tumors of 238 newly diagnosed breast cancer patients who underwent surgery at the Cleveland Clinic between January 1, 1995 and December 31, 1996, and a comparison was made with 5-year clinical follow-up data. Genomic copy number changes were determined by array-based comparative genomic hybridization in 47 breast cancer cases from this population and compared with BRMS1 staining. RESULTS: BRMS1 protein expression was lost in nearly 25% of cases. Patients with tumors that were PR negative (P=0.006) or HER2 positive (P=0.039) and <50 years old at diagnosis (P=0.02) were more likely to be BRMS1 negative. No overall correlation between BRMS1 staining and disease-free survival was observed. A significant correlation, however, was seen between loss of BRMS1 protein expression and reduced disease-free survival when stratified by either loss of ER (P=0.008) or PR (P=0.029) or HER2 overexpression (P=0.026). Overall, there was poor correlation between BRMS1 protein staining and copy number status. CONCLUSIONS: These data suggest a mechanistic relationship between BRMS1 expression, hormone receptor status, and HER2 growth factor. BRMS1 staining could potentially be used in patient stratification in conjunction with other prognostic markers. Further, mechanisms other than genomic deletion account for loss of BRMS1 gene expression in breast tumors.  相似文献   
13.
14.
Farming is an occupation that blends the work and home environments and traditionally involves active participation of all family members, including older farmers. The work patterns of older farmers, including typical work hours, range of activities, and health status, are not well documented. This study, surveying a random sample of older Illinois farmers (N=87), focused on these gaps in the literature. Older farmers were found to work long hours in many farm tasks, more than would be expected in other occupational groups. Further, older farmers were found to have several chronic diseases at higher rates than the general population of the same age and gender; mental health implications were also identified. Rural occupational health nurses are in an optimal position to positively impact older farmers' mental and physical health status.  相似文献   
15.
Automatic capture detection systems are currently available in several cardiac pacing devices. All current systems use low-polarization electrodes and no beat to beat detection system is available for all types of electrodes. In addition the success ratio for currently available systems is not always 100%. Failure to detect capture reliably is often related to the behaviour of the electrode-tissue interface under different circumstances. Pacemaker electrodes can be considered electrochemical cells with complicated characteristics depending on time, temperature and electrical charge. This electrochemical cell is disturbed when a charge is transferred across the electrode-tissue interface during pacing. Several measures can be taken in order to minimise this disturbance or pace polarization artefact (PPA) including the use of high active surface area electrodes and application of tri-phasic pacing pulses. Another factor influencing detection of evoked potentials is the input circuit of the pacemaker affecting the PPA and the evoked response. Positive PPAs can be falsely interpreted as evoked potentials due to the undershoot of the second order filters applied in modern cardiac pacemakers. This paper explains the behaviour of the interface between the electrode and the cardiac tissue in combination with the pacemaker output circuits and input amplifiers under different circumstances.  相似文献   
16.
Previous observations have suggested that differentiated functions of adult rat type II alveolar cells are affected in part by cell-matrix interactions. We examined several aspects of differentiated adult human type II cells cultured on either bovine corneal endothelial cell extracellular matrix (BCECM) or matrix derived from the Englebreth-Holm-Swarm tumor (EHS). Compared to cells cultured on BCECM, adult human type II cells grown on EHS assumed a more cuboidal shape, had a more defined apical-basal polarity, and appeared to contain a greater number of lamellar bodies and neutral lipid inclusions. These cells also incorporated a greater percentage of [14C]acetate into saturated phosphatidylcholine (SPC) than did their counterparts grown on BCECM. In contrast, the relative incorporation of [14C]acetate into phosphatidylglycerol (PG) was lower in cells grown on EHS than cells cultured on BCECM. The histochemical stain for alkaline phosphatase was useful in identification of human type II cells. Alkaline phosphatase expression was elevated in cells cultured on EHS compared to those cultured on BCECM. These results suggest that maintenance of a differentiated morphology, lipid synthesis, and expression of alkaline phosphatase activity by primary cultures of adult human type II cells are also influenced by cell-matrix interactions. All markers of differentiated function of type II cells except synthesis of PG are better maintained on EHS than on BCECM. Under the conditions of these experiments, synthesis of SPC and PG appears to be independently regulated.  相似文献   
17.
18.
Aspects of humoral and cell-mediated immunity that might characterize the continuation of symptoms in 25 patients with chronic Meniere's disease were examined. We found significant elevations of both humoral and cellular immune responses to viral antigens of herpes simplex I, varicella-zoster, rubella, and cytomegalovirus. Serum immunoglobulins were quantitatively abnormal in 24 of 25 patients, without a consistent pattern. These immune responses may be linked to persistent viral infection in chronic Meniere's disease.  相似文献   
19.
The short-term albumin affinity and thrombo-resistance of a polyether polyurethane vascular graft have been improved. The method is based on the C18 alkylation of the polymer. Thrombus formation by a planimetric technique and albumin retention on wire-reinforced polyurethane tubes, both C18 alkylated and untreated, were measured in short-term (4-h) exposure at femoral arterial sites in the dog. 125I-Albumin was preabsorbed on tubes and then exposed to blood for successive 2-h periods. Albumin uptake on alkylated tubes prior to blood exposure and retention following 2 h of blood exposure were significantly greater than on controls. Following a fast desorption phase in blood, the remaining albumin was more slowly desorbed from alkylated than from control tubes. Reincubation with albumin and blood reexposure produced a similar tendency, suggesting blood conditioning does not reduce the albumin affinity-enhancing property of C18 alkylation in the short term. Blood-preconditioning experiments suggested endogenous albumin has a high affinity for the C18-alkylated surface. Scanning electron microscopic examination showed thrombus and platelet densities were higher on control than on alkylated surfaces. These results suggest in vivo albumin affinity is increased for C18-alkylated polyurethane, which may be linked to decreased thrombus formation on these surfaces.  相似文献   
20.
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