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   10904篇
  免费   976篇
  国内免费   30篇
耳鼻咽喉   79篇
儿科学   266篇
妇产科学   280篇
基础医学   1570篇
口腔科学   270篇
临床医学   1257篇
内科学   2479篇
皮肤病学   79篇
神经病学   810篇
特种医学   574篇
外科学   1287篇
综合类   181篇
一般理论   6篇
预防医学   1306篇
眼科学   114篇
药学   771篇
中国医学   4篇
肿瘤学   577篇
  2021年   145篇
  2020年   92篇
  2019年   143篇
  2018年   164篇
  2017年   101篇
  2016年   149篇
  2015年   148篇
  2014年   258篇
  2013年   333篇
  2012年   455篇
  2011年   529篇
  2010年   301篇
  2009年   248篇
  2008年   510篇
  2007年   475篇
  2006年   465篇
  2005年   446篇
  2004年   372篇
  2003年   356篇
  2002年   342篇
  2001年   330篇
  2000年   324篇
  1999年   296篇
  1998年   154篇
  1997年   142篇
  1996年   139篇
  1995年   118篇
  1994年   93篇
  1993年   85篇
  1992年   272篇
  1991年   255篇
  1990年   252篇
  1989年   243篇
  1988年   244篇
  1987年   205篇
  1986年   237篇
  1985年   214篇
  1984年   196篇
  1983年   183篇
  1982年   135篇
  1981年   108篇
  1980年   98篇
  1979年   164篇
  1978年   126篇
  1977年   113篇
  1976年   101篇
  1974年   110篇
  1973年   105篇
  1972年   87篇
  1968年   88篇
排序方式: 共有10000条查询结果,搜索用时 20 毫秒
91.
Eighteen pediatric patients who sustained traumatic brain injury were enrolled in a double-blind, crossover study comparing the effects of 3% saline and 0.9% saline infusions on raised intracranial pressure (ICP). After resuscitation, each patient received a bolus of each saline concentration, and ICP was monitored for 2 h. Initial mean ICP before 0.9% saline infusions equaled 19.3 mm Hg and averaged 20.0 mm Hg during the subsequent 2-h trials (p = 0.32). Baseline mean ICP before 3% saline administration equaled 19.9 mm Hg and averaged 15.8 mm Hg for 2 h postinfusion (p = 0.003). Central venous pressure did not change significantly in either group, nor did measurements of renal function. Serum sodium concentrations increased in all 18 trials of 3% saline. Maximal concentrations of serum sodium occurred 30 min after bolus administration of 3% saline. Three percent saline significantly reduces raised ICP after traumatic brain injury when compared with normal saline. Intravascular dehydration, as measured by central venous pressure, did not occur during the study period.  相似文献   
92.
We report a variant of "guided exposure to mourning," designed for use with patients who have proved resistant to other treatments for unresolved, morbid grief. The work provides some indication as to when such behavioral techniques for resolution of morbid grief are likely to prove successful, and when not.  相似文献   
93.
94.
Summary The main dolichol diphosphate-bound oligosaccharides present in primary cultures of both normal and tumor mouse mammary epithelial cells had the same size, yielded the same pattern after acetolysis and paper chromatography, had the same number of mannose residues susceptible to-mannosidase degradation, and were composed of the same monosaccharide residues. This is the first demonstration that normal and tumor mammary cells have dolichol diphosphate-bound oligosaccharides with very similar, if not identical, structures. These compounds are intermediates in the synthesis of asparagine-linked oligosaccharides. On the other hand, normal and tumor cells showed differences in the specific activities of the enzymes involved in the transfer of the distal monosaccharides from the sugar nucleotides to glycoproteins. Sialyl- and fucosyl-transferases were elevated and galactosyl- and N-acetylglucosaminyltransferases were diminished in mammary tumor cells. The intact tumor cells showed an increased fucosylation of glycoproteins of the asparagine-linkage type. Address for reprints: Roberto L. Ceriani, M.D., Ph.D., Bruce Lyon Memorial Research Laboratory, Children's Hospital Medical Center, 51st and Grove Streets, Oakland, CA 94609, USA.  相似文献   
95.
Summary The uptake and fate of the daunorubicin-DNA complex have been studied in cultured rat embryo fibroblasts. 125I-DNA was digested by the cells and appeared as low molecular weight fragments in the incubation medium. Subcellular fractionation of fibroblasts, previously incubated with the complex, showed that daunorubicin was localized to nuclei and lysosomes. At a high incubation concentration (17.5 M), the accumulation of the free drug exceeded that of the complex. However, at a lower concentration (1.75 M), the accumulation of the complex was as high as that of the free drug.The results are consistent with an uptake of the complex into cultured rat embryo fibroblasts by endocytosis. However, it cannot be excluded that the complex partly dissociates in the incubation medium, and that daunorubicin and DNA thereafter enter the cells separately.  相似文献   
96.
97.
PURPOSE: The aim of this study is to compare glucose metabolism and hypoxia in four different tumor types using positron emission tomography (PET). (18)F-labeled fluorodeoxyglucose (FDG) evaluates energy metabolism, whereas the uptake of (18)F-labeled fluoromisonidazole (FMISO) is proportional to tissue hypoxia. Although acute hypoxia results in accelerated glycolysis, cellular metabolism is slowed in chronic hypoxia, prompting us to look for discordance between FMISO and FDG uptake. EXPERIMENTAL DESIGN: Forty-nine patients (26 with head and neck cancer, 11 with soft tissue sarcoma, 7 with breast cancer, and 5 with glioblastoma multiforme) who had both FMISO and FDG PET scans as part of research protocols through February 2003 were included in this study. The maximum standardized uptake value was used to depict FDG uptake, and hypoxic volume and maximum tissue:blood ratio were used to quantify hypoxia. Pixel-by-pixel correlation of radiotracer uptake was performed on coregistered images for each corresponding tumor plane. RESULTS: Hypoxia was detected in all four patient groups. The mean correlation coefficients between FMISO and FDG uptake were 0.62 for head and neck cancer, 0.47 for breast cancer, 0.38 for glioblastoma multiforme, and 0.32 for soft tissue sarcoma. The correlation between the overall tumor maximum standardized uptake value for FDG and hypoxic volume was small (Spearman r = 0.24), with highly significant differences among the different tumor types (P < 0.005). CONCLUSIONS: Hypoxia is a general factor affecting glucose metabolism; however, some hypoxic tumors can have modest glucose metabolism, whereas some highly metabolic tumors are not hypoxic, showing discordance in tracer uptake that can be tumor type specific.  相似文献   
98.
Although recruitment of ethnic and racial minorities in medical research has been evaluated in several studies, much less is known about the methods used to recruit these populations to participate in cancer genetics research. This report reviews the resources that have been used to identify and recruit ethnic and racial minorities to participate in hereditary breast cancer research. Overall, hospital-based resources were used most often to identify potential subjects, and active recruitment methods were used most frequently to enroll eligible subjects. This review suggests that there appears to be a finite number of resources and strategies to identify and recruit potential subjects to participate in cancer genetics research; however, options for improving awareness about cancer genetics research among ethnic and racial minorities have not been extensively evaluated. To study ethnic and racial minority participation in cancer genetics research, stronger evaluation components will need to be integrated into research methods. Both observational and experimental studies are needed to determine resources that are most effective for identifying potential subjects who are ethnic and racial minorities and to evaluate the effects of different recruitment strategies on enrollment decisions among these populations.  相似文献   
99.
BACKGROUND: Fetal pancreatic tissue has been suggested to be less immunogenic than adult islets. Thus, transplantation of human fetal pancreatic tissue as treatment for type 1 diabetes has been gaining interest. To investigate this question, we tested the peripheral blood mononuclear cell (PBMC) responses from different subject populations to human adult islet proteins (AIP) versus human fetal pancreatic proteins (FPP). METHODS: PBMC responses to FPP and AIP from normal controls (n=14), newly diagnosed type 1 diabetes patients (n=5), long-term type 1 diabetes patients (n=9), and subjects at-risk for development of type 1 diabetes (n=3) were studied. RESULTS: We observed that normal controls demonstrated PBMC reactivity to 0-3 molecular weight regions (mwr) for both the AIP (mean+/-SD, 0.8+/-1.1) and the FPP (0.6+/-0.7). In contrast, newly diagnosed type 1 diabetic patients (<1 year) demonstrated PBMC responses to 9-16 mwr for the AIP (12.8+/-2.5) and 0-14 mwr for the FPP (6.8+/-5.0). The PBMCs from long-term type 1 diabetes patients (> 3 years) were responsive to 2-11 mwr for AIP (6.0+/-2.8) and 0-11 mwr for FPP (4.9+/-4.0). Three nondiabetic ICA positive subjects at-risk for development of type 1 diabetes demonstrated positive PBMC reactivity to 9-18 mwr for the AIP (12.7+/-3.9) and 4-18 mwr for the FPP (10.0+/-5.9). CONCLUSIONS: We conclude that human fetal pancreatic proteins are not significantly less stimulatory than human adult islet proteins to PBMCs of subjects with or at risk for type 1 diabetes.  相似文献   
100.
AIMS: To define outcome measures for auditing the clinical care of children and adolescents with insulin dependent diabetes mellitus (IDDM) and to assess the benefit of appointing a dedicated paediatric trained diabetes specialist nurse (PDSN). METHODS: Retrospective analysis of medical notes and hospital records. Glycaemic control, growth, weight gain, microvascular complications, school absence, and the proportion of children undergoing an annual clinical review and diabetes education session were assessed. The effect of the appointment of a PDSN on the frequency of hospital admission, length of inpatient stay, and outpatient attendance was evaluated. RESULTS: Children with IDDM were of normal height and grew well for three years after diagnosis, but grew suboptimally thereafter. Weight gain was above average every year after diagnosis. Glycaemic control was poor at all ages with only 16% of children having an acceptable glycated haemoglobin. Eighty five per cent of patients underwent a formal annual clinical review, of whom 16% had background retinopathy and 20% microalbuminuria in one or more samples. After appointing the PDSN the median length of hospital stay for newly diagnosed patients decreased from five days to one day, with 10 of 24 children not admitted. None of the latter was admitted during the next year. There was no evidence of the PDSN affecting the frequency of readmission or length of stay of children with established IDDM. Non-attendance at the outpatient clinic was reduced from a median of 19 to 10%. CONCLUSIONS: Outcome measures for evaluating the care of children with IDDM can be defined and evaluated. Specialist nursing support markedly reduces the length of hospital stay of newly diagnosed patients without sacrificing the quality of care.  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