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   5741篇
  免费   445篇
  国内免费   16篇
耳鼻咽喉   37篇
儿科学   241篇
妇产科学   114篇
基础医学   651篇
口腔科学   140篇
临床医学   636篇
内科学   1275篇
皮肤病学   60篇
神经病学   452篇
特种医学   431篇
外科学   802篇
综合类   97篇
一般理论   3篇
预防医学   399篇
眼科学   115篇
药学   320篇
中国医学   7篇
肿瘤学   422篇
  2021年   80篇
  2020年   57篇
  2019年   64篇
  2018年   84篇
  2017年   75篇
  2016年   60篇
  2015年   80篇
  2014年   114篇
  2013年   220篇
  2012年   209篇
  2011年   217篇
  2010年   162篇
  2009年   133篇
  2008年   185篇
  2007年   211篇
  2006年   194篇
  2005年   202篇
  2004年   191篇
  2003年   184篇
  2002年   162篇
  2001年   177篇
  2000年   175篇
  1999年   139篇
  1998年   95篇
  1997年   97篇
  1996年   113篇
  1995年   98篇
  1994年   106篇
  1993年   97篇
  1992年   148篇
  1991年   140篇
  1990年   129篇
  1989年   174篇
  1988年   162篇
  1987年   149篇
  1986年   134篇
  1985年   138篇
  1984年   94篇
  1983年   83篇
  1982年   56篇
  1981年   47篇
  1980年   59篇
  1979年   78篇
  1978年   47篇
  1977年   54篇
  1976年   65篇
  1975年   58篇
  1972年   39篇
  1971年   39篇
  1970年   33篇
排序方式: 共有6202条查询结果,搜索用时 5 毫秒
61.
Malignant melanomas of soft parts from 4 patients were studied by light microscopy, immunocytochemistry for S-100 protein, and electron microscopy. Each patient presented with a deep soft tissue mass in an extremity. Histologically, the tumors were composed of epithelioid and spindle cells, and in one, neoplastic giant cells were present. The tumors did not stain for melanin but were all positive for S-100 protein. Ultrastructurally, premelanosomes were identified in every tumor and in a cell line established from one tumor. Schwann cell features were present in one of the tumors. Although the clinical presentation of malignant melanoma of soft parts is similar to that of epithelioid sarcoma and synovial sarcoma, the combined light microscopic, immunocytochemical, and ultrastructural features should serve to distinguish it from other soft tissue sarcomas.  相似文献   
62.
Summary An investigation was made into the sensitivity of cells in the macaque superior temporal sulcus (STS) to the sight of different perspective views of the head. This allowed assessment of (a) whether coding was viewer-centred (view specific) or object-centred (view invariant) and (b) whether viewer-centred cells were preferentially tuned to characteristic views of the head. The majority of cells (110) were found to be viewer-centred and exhibited unimodal tuning to one view. 5 cells displayed object-centred coding responding equally to all views of the head. A further 5 cells showed mixed properties, responding to all views of the head but also discriminating between views. 6 out of 56 viewer and object-centred cells exhibited selectivity for face identity or species. Tuning to view varied in sharpness. For most (54/73) cells the angle of perspective rotation reducing response to half maximal was 45–70° but for 19/73 it was >90°. More cells were optimally tuned to characteristic views of the head (the full face or profile) than to other views. Some cells were, however, found tuned to intermediate views throughout the full 360 degree range. This coding of many distinct head views may have a role in the analysis of social signals based on the interpretation of the direction of other individuals' attention.  相似文献   
63.
64.
BACKGROUND: Treatment with local glucocorticoids (GCs) decreases symptoms and the size of nasal polyps. This might depend on the downregulation of proinflammatory genes, as well as the upregulation of anti-inflammatory genes. OBJECTIVE: We sought to identify GC-regulated anti-inflammatory genes in nasal polyps. METHODS: Affymetrix DNA microarrays were used to analyze the expression of 22,283 genes in 4 nasal polyps before and after local treatment with fluticasone (400 microg/d). Expression of uteroglobin and mammaglobin B was analyzed with real-time PCR in 6 nasal polyps and in nasal biopsy specimens from 6 healthy control subjects. RESULTS: Two hundred three genes had changed in expression in treated polyps, and 139 had known functions: 54 genes were downregulated, and 85 were upregulated. Genes associated with inflammation constituted the largest single functional group. These genes affected key steps in inflammation (eg, immunoglobulin production; antigen processing and presentation; and the chemoattraction and activation of granulocytes, T cells, and B cells). Several proinflammatory genes were downregulated. In contrast, some anti-inflammatory genes were upregulated. The gene that increased most in terms of expression was uteroglobin. This was confirmed with real-time PCR. By contrast, expression of uteroglobin was lower in untreated polyps than in healthy nasal mucosa. Immunohistochemical investigation showed staining of uteroglobin in the epithelium and in seromucous glands in control subjects and in nasal polyps. CONCLUSION: Upregulation of anti-inflammatory genes, such as uteroglobin, might contribute to the effects of local treatment with GCs in nasal polyps.  相似文献   
65.
In a 2-year hospital-based study of paediatric gastroenteritis in Blantyre, Malawi, astroviruses were detected by enzyme immunoassay in 15 (1.9%) of 786 inpatients and in 9 (2.3%) of 400 outpatients. Greater disease severity was noted in children coinfected with human immunodeficiency virus (HIV). Six human astrovirus (HAstV) genotypes were identified, including HAstV-1 (25%), HAstV-2 (21%), HAstV-3 (25%), HAstV-4 (13%), HAstV-5 (4%), and HAstV-8 (13%). Although astroviruses are not major causes of gastroenteritis among children admitted to hospital in Blantyre, concomitant HIV infection appears to be a risk factor for increased severity of disease.  相似文献   
66.
The survey of manpower in community hospital and private laboratory practice of pathology of 1988 presented herein verifies the conclusions of the 1986 survey that a growing deficit of manpower in this sphere of practice is highly likely in the next few years. It appears that the deficit will be even larger than that predicted by the 1986 survey. Steps are urgently needed to increase the flow of graduating medical students, especially those of top quality, into our specialty.  相似文献   
67.
Communication skills training is now internationally accepted as an essential component of medical education. However, learners and teachers in communication skills programs continue to experience problems integrating communication with other clinical skills, ensuring that clinical faculty support and teach communication beyond the formal communication course, extending communication training coherently into clerkship and residency, and applying communication skills in medical practice at a professional level of competence. One factor contributing to these problems is that learners confront two apparently conflicting models of the medical interview: a communication model describing the process of the interview and the "traditional medical history" describing the content of the interview. The resulting confusion exacerbates the above dilemmas and interferes with learners using communication skills training to advantage in real-life practice. The authors propose a comprehensive clinical method that explicitly integrates traditional clinical method with effective communication skills. To implement this more comprehensive approach, they have modified their own Calgary-Cambridge guides to the medical interview by developing three diagrams that visually and conceptually improve the way communication skills teaching is introduced and that place communication process skills within a comprehensive clinical method; devising a content guide for medical interviewing that is more closely aligned with the structure and process skills used in communication skills training; and incorporating patient-centered medicine into both process and content aspects of the medical interview. These enhancements help resolve ongoing difficulties associated with both teaching communication skills and applying them effectively in medical practice.  相似文献   
68.

Background  

Genetic polymorphisms of the TCF7L2 gene are strongly associated with large increments in type 2 diabetes risk in different populations worldwide. In this study, we aimed to confirm the effect of the TCF7L2 polymorphism rs7903146 on diabetes risk in a Brazilian population and to assess the use of this genetic marker in improving diabetes risk prediction in the general population.  相似文献   
69.
To test the hypothesis that maximal androgen blockade improves the effectiveness of the treatment of prostatic cancer, we conducted a randomized, double-blind trial in patients with disseminated, previously untreated prostate cancer (stage D2). All 603 men received leuprolide, an analogue of gonadotropin-releasing hormone that inhibits the release of gonadotropins, in combination with either placebo or flutamide, a nonsteroidal antiandrogen that inhibits the binding of androgens to the cell nucleus. As compared with the 300 patients receiving leuprolide and placebo, the 303 patients randomly assigned to receive leuprolide and flutamide had a longer progression-free survival (16.5 vs. 13.9 months; P = 0.039) and an increase in the median length of survival (35.6 vs. 28.3 months; P = 0.035). The differences between the treatments were particularly evident for men with minimal disease and good performance status; however, further studies should be conducted in this subgroup. Symptomatic improvement was greatest during the first 12 weeks of the combined androgen blockade, when leuprolide alone often produces a painful flare in the disease. We conclude that in patients with advanced prostate cancer, treatment with leuprolide and flutamide is superior to treatment with leuprolide alone.  相似文献   
70.
In a series of 13 elderly patients with proven prealbumin-related senile systemic amyloidosis (SSA), depressed serum prealbumin values (110.7 +/- 14.1 micrograms/ml) were found as compared to an age-matched control group (175.1 +/- 20.3 micrograms/ml). As expected, there was a significant correlation between serum prealbumin and serum retinol-binding proteins in both groups of patients. Patients with reactive amyloid protein AA amyloidosis had slightly depressed serum prealbumin concentrations, whereas patients with prealbumin-related familial amyloidosis of Swedish type had prealbumin values within normal limits. Since the serum levels of the acute phase reactants, haptoglobin and amyloid-related serum protein AA, were higher in the group of patients with reactive amyloidosis than in patients with SSA, the depression of the prealbumin levels in SSA is not a result of inflammation. Since SSA is known to contain prealbumin, it is possible that a disturbed prealbumin metabolism in old age results in low prealbumin serum values and deposition of amyloid.  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