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   22352篇
  免费   1465篇
  国内免费   41篇
耳鼻咽喉   150篇
儿科学   708篇
妇产科学   738篇
基础医学   2820篇
口腔科学   303篇
临床医学   3613篇
内科学   3825篇
皮肤病学   203篇
神经病学   2335篇
特种医学   401篇
外科学   1980篇
综合类   257篇
一般理论   32篇
预防医学   3318篇
眼科学   334篇
药学   1291篇
中国医学   23篇
肿瘤学   1527篇
  2024年   13篇
  2023年   140篇
  2022年   154篇
  2021年   418篇
  2020年   289篇
  2019年   442篇
  2018年   544篇
  2017年   409篇
  2016年   458篇
  2015年   553篇
  2014年   758篇
  2013年   1129篇
  2012年   1662篇
  2011年   1807篇
  2010年   942篇
  2009年   846篇
  2008年   1544篇
  2007年   1680篇
  2006年   1561篇
  2005年   1546篇
  2004年   1548篇
  2003年   1405篇
  2002年   1396篇
  2001年   219篇
  2000年   141篇
  1999年   178篇
  1998年   261篇
  1997年   225篇
  1996年   159篇
  1995年   180篇
  1994年   160篇
  1993年   121篇
  1992年   107篇
  1991年   81篇
  1990年   58篇
  1989年   65篇
  1988年   59篇
  1987年   55篇
  1986年   35篇
  1985年   64篇
  1984年   60篇
  1983年   58篇
  1982年   61篇
  1981年   58篇
  1980年   36篇
  1979年   25篇
  1978年   24篇
  1977年   17篇
  1974年   13篇
  1973年   13篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
This study was designed to investigate the expression of cyclooxygenase (COX)-2 in ovarian serous tumors (benign, borderline tumors, and carcinomas) and primary peritoneal serous carcinomas. Cases diagnosed between 1995 and 2001 were reviewed; 47 benign tumors, 6 borderline tumors, and 39 carcinomas were examined, as well as 12 normal ovaries that served as controls. Blocks were stained with anti COX-2 polyclonal antibody and staining was graded qualitatively. The staining intensity was assessed as weak (score of 1), moderate (score of 2), or strong (score of 3). Normal ovarian and tubal epithelium, inclusion cysts, benign serous tumors, and borderline tumors had a uniform score 3 staining pattern. Serous ovarian carcinomas had variable staining scores, tending to correlate with the level of tumor differentiation. Well-differentiated carcinomas had more intense COX-2 staining than poorly differentiated carcinomas, which had only weak COX-2 staining. The degree of COX-2 staining was not significantly related to overall survival. In conclusion, COX-2 expression is present in serous tumors, including benign tumors, borderline tumors, and carcinomas. Similar to the findings in other neoplasms, COX-2 expression is strongest in well-differentiated tumors and is much less evident in those that are poorly differentiated. The clinical utility of these findings is related to the potential role of nonsteroidal anti-inflammatory drugs, which are COX-2 inhibitors, in treating and/or preventing some forms of ovarian carcinoma.  相似文献   
102.
BACKGROUND: Evidence suggests that prenatal insult may play a role in the etiology of psychotic disorders. Minor physical anomalies (MPA) are an indicator of abnormal fetal development and are elevated in individuals at genetic and behavioral risk for psychosis. Yet, there has been little empirical research on the relationships between MPAs and other neurobiological risk indicators. We hypothesized that the frequency of MPAs (an external marker of prenatal central nervous system [CNS] disruption) would be associated with two other biomarkers suggestive of disruptions in fetal neurodevelopment: movement abnormalities (an indicator of striatal abnormalities) and heightened cortisol secretion (an indicator of hypothalamic-pituitary-adrenal [HPA]/hippocampal function). METHODS: Participants with schizotypal personality disorder (SPD; n = 39) and both normal (n = 47) and other personality disorders (n = 28) control subjects were administered structured diagnostic interviews and assessed for MPAs, movement abnormalities, and salivary cortisol. RESULTS: Schizotypal personality disorder participants showed significantly greater MPAs and movement abnormalities and higher cortisol than both the normal and other personality disorders groups. Hierarchical linear regression analyses revealed that higher rates of MPAs were linked with greater movement abnormalities and salivary cortisol. CONCLUSIONS: The findings suggest that MPAs serve as a marker of neurodevelopmental abnormalities that affect striatal and hippocampal regions.  相似文献   
103.
104.
(111)In-DTPA-human epidermal growth factor ((111)In-DTPA-hEGF [DTPA is diethylenetriaminepentaacetic acid]) is an Auger electron-emitting radiopharmaceutical that targets EGF receptor (EGFR)-positive cancer. The purpose of this study was to determine the effect of EGFR inhibition by gefitinib on the internalization, nuclear translocation, and cytotoxicity of (111)In-DTPA-hEGF in EGFR-overexpressing MDA-MB-468 human breast cancer cells. METHODS: Western blot analysis was used to determine the optimum concentration of gefitinib to abolish EGFR activation. Internalization and nuclear translocation of fluorescein isothiocyanate-labeled hEGF were evaluated by confocal microscopy in MDA-MB-468 cells (1.3 x 10(6) EGFRs/cell) in the presence or absence of 1 microM gefitinib. The proportion of radioactivity partitioning into the cytoplasm and nucleus of MDA-MB-468 cells after incubation with (111)In-DTPA-hEGF for 24 h at 37 degrees C in the presence or absence of 1 microM gefitinib was measured by cell fractionation. DNA double-strand breaks caused by (111)In were quantified using the gamma-H2AX assay, and radiation-absorbed doses were estimated. Clonogenic survival assays were used to measure the cytotoxicity of (111)In-DTPA-hEGF alone or in combination with gefitinib. RESULTS: Gefitinib (1 microM) completely abolished EGFR phosphorylation in MDA-MB-468 cells. Internalization and nuclear translocation of fluorescein isothiocyanate-labeled EGF were not diminished in gefitinib-treated cells compared with controls. The proportion of internalized (111)In that localized in the nucleus was statistically significantly greater when (111)In-DTPA-hEGF was combined with gefitinib compared with (111)In-DTPA-hEGF alone (mean +/- SD: 26.0% +/- 5.5% vs. 14.6% +/- 4.0%, respectively; P < 0.05). Induction of gamma-H2AX foci was greater in MDA-MB-468 cells that were treated with (111)In-DTPA-hEGF (250 ng/mL, 1.5 MBq/mL) plus gefitinib (1 microM ) compared with those treated with (111)In-DTPA-hEGF alone (mean +/- SD: 35 +/- 4 vs. 24 +/- 5 foci per nucleus, respectively). In clonogenic assays, a significant reduction in the surviving fraction was observed when (111)In-DTPA-hEGF (5 ng/mL, 6 MBq/microg) was combined with gefitinib (1 microM ) compared with (111)In-DTPA-hEGF alone (42.9% +/- 5.7% vs. 22.9% +/- 3.6%, respectively; P < 0.01). CONCLUSION: The efficacy of (111)In-DTPA-hEGF depends on internalization and nuclear uptake of the radionuclide. Nuclear uptake, DNA damage, and cytotoxicity are enhanced when (111)In-DTPA-hEGF is combined with gefitinib. These results suggest a potential therapeutic role for peptide receptor radionuclide therapy in combination with tyrosine kinase inhibitors.  相似文献   
105.
106.
Francisella tularensis, the causative agent of tularemia, is a highly infectious gram-negative coccobacillus. Due to its high infectivity it is of major concern to public health officials as a possible biological weapon. Although accidental exposure can occur through arthropod bites, handling infected animals, or breathing in aerosols, cases are usually isolated and contained. In the event of an intentional exposure such as in a bioterrorist attack, inhalation of aerosols can result in devastating consequences with much causality. Although a vaccine is available, sufficient quantities may not be readily accessible in an actual attack. Therefore, it is very important for both medical professionals and public health officials to be prepared to contain and control the situation should it actually occur.  相似文献   
107.
Community-acquired viral respiratory tract infections (RTI) in lung transplant recipients may have a high rate of progression to pneumonia and can be a trigger for immunologically mediated detrimental effects on lung function. A cohort of 100 patients was enrolled from 2001 to 2003 in which 50 patients had clinically diagnosed viral RTI and 50 were asymptomatic. All patients had nasopharyngeal and throat swabs taken for respiratory virus antigen detection, culture and RT-PCR. All patients had pulmonary function tests at regular intervals for 12 months. Rates of rejection, decline in forced expiratory volume (L) in 1 s (FEV-1) and bacterial and fungal superinfection were compared at the 3-month primary endpoint. In the 50 patients with RTI, a microbial etiology was identified in 33 of 50 (66%) and included rhinovirus (9), coronavirus (8), RSV (6), influenza A (5), parainfluenza (4) and human metapneumovirus (1). During the 3-month primary endpoint, 8 of 50 (16%) RTI patients had acute rejection versus 0 of 50 non-RTI patients (p=0.006). The number of patients experiencing a 20% or more decline in FEV-1 by 3 months was 9 of 50 (18%) RTI versus 0 of 50 non-RTI (0%) (p=0.003). In six of these nine patients, the decline in FEV-1 was sustained over a 1-year period consistent with bronchiolitis obliterans syndrome (BOS). Community-acquired respiratory viruses may be associated with the development of acute rejection and BOS.  相似文献   
108.
Weight loss after gastric bypass procedures has been well studied, but the long-term metabolic sequelae are not known. Data on bone mineral density (BMD), calcium, parathyroid hormone, and vitamin D were collected preoperatively and at yearly intervals after gastric bypass procedures. A total of 230 patients underwent preoperative BMD scans. Fifteen patients were osteopenic preoperatively, and three patients subsequently developed osteopenia postoperatively within the first year. No patient had or developed osteoporosis. At 1 year, total forearm BMD decreased by 0.55% (n = 91; P = .03) and radius BMD had increased overall by 1.85% (n = 23; P = .008); both total hip and lumbar spine BMD decreased by 9.27% (n = 22; P < .001) and 4.53% (n = 31; P < .001), respectively. By the second postoperative year, BMD in the total forearm had decreased an additional 3.62% (n = 14; P<.001), whereas radius BMD remained unchanged. Although total hip and lumbar spine BMD significantly decreased at 1 year, by year 2 both total hip and lumbar spine BMD only slightly decreased and were not significantly different from before the operation. Serum calcium decreased from 9.8 mg/dL to 9.2 during the first year (not significant [NS]) and then to 8.8 (NS) by the second year. Parathyroid hormone increased from 59.7 pg/mL (nl 10-65 pg/mL) preoperatively to 63.1 during year 1 (NS) and continued to increase to 64.7 by year 2 (NS). No difference was noted among levels of 25-hydroxy vitamin D preoperatively (25.2 ng/mL; nl 10-65 ng/mL), at 1 year (34.4), and at 2 years (35.4). Our data indicate that bone loss is highest in the first year after gastric bypass with stabilization, and that, in some cases, there is an increase in bone density after the first year. Presented at the Forty-Sixth Annual Meeting of The Society for Surgery of the Alimentary Tract, Chicago, Illinois, May 14–18, 2005 (oral presentation).  相似文献   
109.
In this observational study, we sought to assess the usefulness of pH values from residuals in intensive care unit (ICU) patients with small-bore feeding tubes. A review of the literature demonstrated that most critically ill patients were excluded in previous studies on gastric pH testing, suggesting that pH testing in critical care is not warranted. Our results demonstrated that 21% of intestinal testing and 64% of gastric testing yielded potential misinformation to the bedside nurse with regards to possible tube location. In conclusion, pH testing for small-bore tube placement and maintenance was not deemed meaningful in our critical care unit.  相似文献   
110.
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