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   7259篇
  免费   1532篇
  国内免费   152篇
耳鼻咽喉   118篇
儿科学   124篇
妇产科学   47篇
基础医学   1681篇
口腔科学   351篇
临床医学   829篇
内科学   590篇
皮肤病学   38篇
神经病学   839篇
特种医学   231篇
外国民族医学   1篇
外科学   419篇
综合类   483篇
预防医学   1958篇
眼科学   109篇
药学   358篇
中国医学   403篇
肿瘤学   364篇
  2023年   368篇
  2022年   252篇
  2021年   204篇
  2020年   150篇
  2019年   157篇
  2018年   281篇
  2017年   36篇
  2016年   376篇
  2015年   691篇
  2014年   514篇
  2013年   493篇
  2012年   328篇
  2011年   153篇
  2010年   291篇
  2009年   291篇
  2008年   162篇
  2007年   22篇
  2006年   9篇
  2005年   99篇
  2004年   509篇
  2003年   81篇
  2002年   89篇
  2001年   84篇
  2000年   18篇
  1999年   41篇
  1998年   145篇
  1997年   240篇
  1996年   243篇
  1995年   207篇
  1994年   334篇
  1993年   215篇
  1992年   254篇
  1991年   257篇
  1990年   237篇
  1989年   172篇
  1988年   184篇
  1987年   75篇
  1986年   112篇
  1985年   104篇
  1984年   86篇
  1983年   60篇
  1982年   99篇
  1981年   71篇
  1980年   39篇
  1979年   31篇
  1978年   24篇
  1977年   21篇
  1976年   12篇
  1975年   12篇
  1973年   8篇
排序方式: 共有8943条查询结果,搜索用时 672 毫秒
21.
Forty-one cases of nasopharyngeal and 13 cases of nasal malignant lymphoma have been examined histologically and immunohistochemically. All of the cases were non-Hodgkin's lymphoma; one case was of follicular type and the remaining 53 were of diffuse type. Large cell lymphoma comprised 48% of cases and most of the immunoblastic lymphomas showing pleomorphism occurred in the nose. Twenty-seven cases were of T-cell and 21 of B-cell phenotype. The predominance of T-cell lymphoma was due to an increased incidence of these in the nose, the T:B ratio of 3.33:1 contrasting with a 1:1.05 ratio in the nasopharynx. Nasopharyngeal lymphomas seem to show an intermediate incidence between the T-cell predominance in the nose and a B-cell predominance in the oropharynx. Since the large cell type of lymphoma was predominant, the differential diagnosis from undifferentiated carcinoma is important and is facilitated by the use of immunostaining methods.  相似文献   
22.
A review of recent studies shows that physicians have a poor record in detection of cases of domestic violence, with only one battered woman in twenty-five diagnosed on physical examination. Emergency physicians who are more aware of the distinguishing features of the battering syndrome and provide appropriate crisis intervention may help victims to seek early legal and social aid, thereby preventing development of a chronic situation or a personal tragedy.  相似文献   
23.
Pneumocystis carinii pneumonia (PCP) is the most common opportunistic human immunodeficiency virus (HIV)-related infection, occurring in 85 % of HIV infected patients without prophylaxis. Preventive treatment is required when CD4 cell count falls below 200 cells per cubic millimeter. Cotrimoxazole has been shown to be highly effective but alternative drug regimens are often necessary because of the frequent drug hypersensitivity exhibited by HIV infected patients. The aim of this prospective, open, randomized, one-site study, involving HIV-infected patients with a CD4 cell count below 200/mm3, or a percentage under 20%, randomly assigned to receive either dapsone 50 mg daily or Fansidar® one tablet weekly, was to compare the efficacy and safety of these drugs in the primary prophylaxis of PCP. Both dapsone and Fansidar® appear to be safe and effective alternative agents for the prevention of PCP. Their role in Toxoplasma gondii prophylaxis requires further evaluation.  相似文献   
24.
The validity of a self-administered diet history questionnaire has been estimated using as the reference data the mean of three 4-day diet records collected over the year prior to the administration of the questionnaire, in 1985–1986. Subjects were women ages 45–70 years, participants in the Women's Health Trial Feasibility Study, a multi-center clinical trial in which some women were randomized to be taught to adopt and maintain a low-fat diet, while others maintained their usual diet. The questionnaire produced group mean nutrient estimates closely approximating the values obtained by three 4-day records, e.g. in the usual-diet group, 37.7% of calories from fat by both food records and by questionnaire, and in the low-fat, group, 21.3% of calories from fat by food records and 23.7% of calories from fat by questionnaire. Correlations between questionnaire and diet records for per cent of calories from fat were 0.67 and 0.65 respectively in the two groups; most correlations were in the 0.5–0.6 range, and were similar to those achievable by a single 4-day food record.  相似文献   
25.
Objective: To determine if uncooked cornstarch, as part of the evening snack, can avert nocturnal hypoglycemia in type 1 diabetes. Research Design and Methods: Fifty-one campers and counselors at the American Diabetes Association Camp in San Bernardino, CA were randomly assigned to receive 5 g of uncooked cornstarch as part of the 21:00 evening snack vs. a standard snack of equivalent carbohydrate content. Each snack was given for five nights and the participants and medical personnel were blinded as to assignment. Midnight and 07:00 finger stick blood glucose levels were compared with values <60 mg/dl defined as hypoglycemia and values >250 mg/dl defined as hyperglycemia. Results: There were 218 midnight and 222 07:00 values for comparison. There were six episodes of hypoglycemia at midnight and nine episodes of hypoglycemia at 07:00 for the cornstarch snack nights vs. 30 hypoglycemia episodes at midnight and 21 at 07:00 for the standard snack nights (P < 0.001 and < 0.05, respectively). There was no difference in the number of hyperglycemic events at midnight or 07:00 for the cornstarch vs. standard snack nights. At midnight, 12% of campers had hypoglycemia after the cornstarch snack vs. 46% after the standard snack (P < 0.001), and at 07:00, 16% had hypoglycemia after cornstarch vs. 26% after the standard snack (P = 0.327). Conclusions: These data suggest that uncooked cornstarch, as part of the evening snack, can diminish the nighttime and morning hypoglycemia associated with type 1 diabetes, without causing hyperglycemia.  相似文献   
26.
Mature (average patient age = 29.5 yr, closed apical foramen) and immature (average patient age = 17.5 yr, open apical foramen) root shards were placed in dialysis tubing and demineralized to completion using either 10% disodium EDTA plus protease inhibitors or 0.6 N HCl. The demineralized shards were re-extracted (five times) with 0.05 M tris-HCl, 1.0 M NaCl and then collagenase digested. No major differences were observed in chromatograms of extracts, re-extracts or collagenase digests from root shards demineralized in either way. In contrast, chromatograms of immature and mature roots showed qualitative differences. Chromatograms of mature roots demineralized in either way showed broader protein peaks and less organic phosphorus than those from immature tooth roots. A distinct band amid degraded phosphoprotein (150 K) was found in SDS-PAGE gels (7.5%) from EDTA-extracted immature tooth roots but not from mature tooth roots. Electroelution of this band revealed a typical phosphoprotein amino-acid profile containing increased aspartic acid and serine residues. Comparison of the total phosphoprotein and amino acid composition of extracts, re-extracts and collagenase digests revealed that phosphoprotein, serine and to a lesser extent aspartic acid were recovered in greater quantities from immature roots than mature tooth roots. These data suggest that the degree of maturation is crucial to the isolation of an intact phosphoprotein and provides additional evidence that human dentine phosphoprotein undergoes amino acid compositional changes during maturation.  相似文献   
27.
In this study, skin-infiltrating cells were characterized in both the active and remission phases of post-burn hypertrophic scar biopstes. Immunohistochemistry examination of active phase samples showed an abundant presence of Langerhans cells, T cells, macrophages, a low presence of natural killer cells and the lack of B lymphocytes. In active hypertrophic scars T lymphocytes infiltrate deep into the superficial dermis and are also observed in the epidermis: CD3+ cells were present at about 222±107 per 0.25 mm2. In particular the analysis of lymphocyte subpopulations showed that CD4+ T cells predominate in the dermis as well as in the epidermis of active hypertrophic scars whereas CD8+ cells were less well represented (CD4/CD8 ratio is 2.06). This distribution was also shown in remission phase samples and in normotrophic scar specimens, although the lymphocyte number was significantly lower. Approximately 70 per cent of T lymphocytes present in the tissue involved in active phase hypertrophic scar samples were activated (positive with anti-HLA-DR and IL-2 receptor antibodies) which is significantly higher than remission phase hypertrophic and normotrophic scars, in which positivity was 40 and 38 per cent, respectively. Upon activation, the lesional lymphocytes release several cytokines, locally and transiently, that interact with specific receptors in response to different stimulation. Central to the immune hypothesis of hypertrophic scars is that some of the T-cell lymphokines act on keratinocytes, fibroblasts and other cell types to induce changes characteristic of these scars. The presence and close proximity of activated T lymphocytes and antigen-presenting cells of various phenotypes in both the epidermis and dermis of hypertrophic tissues provides strong circumstantial evidence of a local immune response. However, the manner in which T cells achieve and maintain their activated state in hypertrophic tissues in not yet known, and both antigen-dependent and independent mechanisms may contribute.  相似文献   
28.
Purified secretory acetylcholinesterase (sAChE) from Trichostrongylus colubriformis was used as a candidate vaccine against mixed T. colubriformis, Haemonchus contortus and C. oncophora challenge infections of sheep. Cross species protection was achieved with an average reduction in worm burden of all species of 31%, rising to 58% in individual cases. There was no consistent reduction in faecal egg counts and increases in anti-T. colubriformis sAChE IgG antibody levels following vaccination were modest. We suggest that improved antigen delivery systems will result in increased host protection.  相似文献   
29.
Diversion colitis refers to the inflammatory changes that occur in the defunctioned segment of the large intesting following diversion of the faecal stream. We report the histological features in the defunctioned rectums from seven patients: one each with severe constipation and Behcet's disease, two with Crohn's disease with rectal sparing and three with ulcerative colitis. The appearances of diversion colitis in a previously normal rectum are compared with diversion colitis with superimposed inflammatory bowel disease. Lymphoid follicular hyperplasia was found in all cases. This was marked in patients with inflammatory bowel disease. with or without initial rectal involvement. Other changes comprised surface epithelial degeneration and ulceration, mucosal inflammation including crypt abscesses, and crypt branching. Inflammatory and crypt changes were mild, except in ulcerative colitis where changes were marked and resembled those of the proximal colon. Lymphoid hyperplasia is a distinctive feature in diversion colitis. The term follicular proctitis, previously used to indicate chronic ulcerative colitis exclusively, should be re-examined.  相似文献   
30.
Necrotizing sialometaplasia is a benign condition first described in minor salivary glands of the soft palate with morphological changes which can be misinterpreted as squamous-cell carcinoma. Similar lesions have been subsequently reported in other locations including major salivary glands, lip, breast and skin (the term syringometaplasia has been applied for the latter). We report three cases of such a process involving submucosal glands in the trachea following prolonged translaryngeal intubation.  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