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   3640篇
  免费   328篇
  国内免费   40篇
耳鼻咽喉   43篇
儿科学   129篇
妇产科学   118篇
基础医学   394篇
口腔科学   97篇
临床医学   393篇
内科学   785篇
皮肤病学   126篇
神经病学   197篇
特种医学   260篇
外科学   402篇
综合类   113篇
一般理论   2篇
预防医学   334篇
眼科学   198篇
药学   268篇
中国医学   3篇
肿瘤学   146篇
  2021年   39篇
  2020年   22篇
  2019年   42篇
  2018年   37篇
  2017年   38篇
  2016年   38篇
  2015年   60篇
  2014年   70篇
  2013年   147篇
  2012年   131篇
  2011年   150篇
  2010年   119篇
  2009年   126篇
  2008年   134篇
  2007年   132篇
  2006年   141篇
  2005年   118篇
  2004年   116篇
  2003年   84篇
  2002年   106篇
  2001年   87篇
  2000年   89篇
  1999年   96篇
  1998年   100篇
  1997年   105篇
  1996年   101篇
  1995年   68篇
  1994年   88篇
  1993年   67篇
  1992年   66篇
  1991年   59篇
  1990年   54篇
  1989年   85篇
  1988年   74篇
  1987年   66篇
  1986年   73篇
  1985年   86篇
  1984年   59篇
  1983年   32篇
  1982年   43篇
  1981年   37篇
  1980年   26篇
  1979年   54篇
  1978年   36篇
  1977年   31篇
  1976年   25篇
  1974年   21篇
  1973年   32篇
  1972年   34篇
  1969年   24篇
排序方式: 共有4008条查询结果,搜索用时 984 毫秒
71.
Bioavailability was measured by rifapentine (RPE) serum concentrations and by the urinary ratio between RPE and creatinine, in specimens obtained 4-50 h after 600 mg RPE preceded by food. The bioavailabilities of RPEs manufactured in China and by a Western manufacturer were similar after a standard English breakfast, and serum concentrations were also similar to those obtained in an earlier Italian study following a complex meal. Although absorption of RPE was unsatisfactory after lipid-rich biscuits or shortbread, absorption after egges and toast was excellent and was nearly as good after a fast-food sandwich. The urinary measure of bioavailability at 26 h appeared as efficient as peak serum estimations at 6, 8 and 26 h. Fast-food sandwiches are being taken before RPE in a current clinical trial of Chinese RPE in Hong Kong.  相似文献   
72.
One million individuals in the United States alone are estimated to be current or past users of anabolic-androgenic steroids. In the United States fifty-percent of anabolic-androgenic steroid users administer their compounds intramuscularly, and twenty-five percent of adolescent anabolic-androgenic steroid users share needles, placing these young adults at risk for infections related to injection. To examine the medical literature for reports of infections attributable to anabolic-androgenic steroids, we conducted a MEDLINE (1966-1998) and AIDSLINE (1980-1998) world literature review to examine all references that attributed infections to anabolic-androgenic steroid injection. Infections associated with anabolic-androgenic steroid injection include three cases of HIV, one case of hepatitis B, one case of hepatitis C, eight abscesses, and a case of fungal endophthalmitis. No cross-sectional or prospective studies exist that document the risk of infections related to anabolic-androgenic steroid injection. These serious infectious complications of anabolic-androgenic steroid injection may be avoided with education and prevention techniques. Infections occurring in anabolic-androgenic steroid users are not as common as in intravenous drug users.  相似文献   
73.
74.
BACKGROUND AND OBJECTIVE: Recent developments in fiber laser technology have introduced highly efficient, compact sources with high output beam quality. The first laser-tissue interaction studies with a high-power 2-microm fiber laser were conducted. STUDY DESIGN/MATERIALS AND METHODS: Chicken breast and porcine muscle tissue samples were subjected to continuous wave (cw) irradiation at 800-mW and 5-W output power levels, with spot sizes of approximately 150 microm. After laser irradiation, samples were inspected with an optical microscope and prepared for histologic processing. RESULTS: Evaluation of surface changes in tissue samples indicated an interaction similar in nature to those previously demonstrated with other cw lasers, but with photothermal ablation characteristics typical of strongly absorbed lasers operating in the infrared wavelength region. An ablation velocity of 0.27 mm.sec(-1) in porcine tissue was determined at 800-mW incident power. Histopathologic analysis demonstrated the formation of lesions with minimal damage at boundaries and no evidence of carbonization. CONCLUSIONS: Results indicate that this fiber laser has the potential to fulfill applications in the medical field.  相似文献   
75.
OBJECTIVE: This panel study examined the relations between alcohol-specific socialization by parents (monitoring of alcohol use by children, allowing alcohol use by children at home, communicating against alcohol use and setting rules against alcohol use), general dimensions of parenting behavior (responsiveness and demandingness) and alcohol use by children. METHOD: A sample of 488 fifth-grade children reported their perceptions of alcohol-specific socialization by parents, parental responsiveness and parental demandingness. These variables were used to predict alcohol use when children in the panel were in seventh grade. RESULTS: Nineteen percent of seventh-grade children reported alcohol use in the past 30 days. Logistic regression analyses indicated that, after accounting for children's age, sex, single parent status, prior use of alcohol and exposure to parental modeling of alcohol use, the odds of alcohol use were significantly greater among children who perceived no parental monitoring of alcohol use, who had been allowed by parents to have a drink with alcohol at home and who perceived relatively low levels of parental demandingness. Rules against alcohol use, parental communication against alcohol use and parental responsiveness were unrelated to the study outcome. CONCLUSIONS: Parental monitoring of alcohol use by children, family norms regarding alcohol use by children at home and parental ability to set and enforce behavioral rules merit consideration as factors that should be modified by prevention programs. There is a need, however, for additional research that further examines the relations between exposure to such parenting behaviors during childhood and alcohol use during adolescence.  相似文献   
76.
The purpose of this study is to demonstrate that by using a proven method of stratifying open-heart operations into levels of predicted mortality, hospitals can closely monitor trends of their open-heart programs and possibly improve the health planning decisions for their institution. A proven method of uniform risk stratification utilizing objective and readily available preoperative patient data was implemented at our institution for a 12 month period (September 1, 1991 through August 31, 1992). A total of 367 patients were included in this study. The patients were categorized into four risk ranges (0 to 4% good risk, 5 to 9% fair risk, 10 to 14% poor risk, and greater than or equal to 15% high risk) indicating a predictive percent probability of operative mortality. The number of patients categorized as either 0 to 4% good risk, 5 to 9% fair risk, 10 to 14% poor risk, and greater than or equal to 15% high risk were 46, 74, 84 and 163, respectively. The patient's average post-operative length of stay in each risk category was 7.6 days, 8.2 days, 10 days, and 12 days, respectively. The patient's average total hospital charges in each risk category were $48,241, $53,531, $60,416 and $75,555, respectively. This information has helped our hospital administration make relevant and objective decisions concerning our open-heart program. Uniform risk stratification (outcomes research) should be incorporated into all adult open-heart surgery programs because it is simple, inexpensive, and can evaluate the outcomes and cost of open-heart surgery.  相似文献   
77.
78.
79.
BACKGROUND: Graft-versus-host disease (GVHD) is a major and sometimes fatal complication of allogeneic bone marrow transplantation (BMT). The prediction of GVHD remains an important issue in preventing morbidity and mortality after allogeneic BMT. In the past 10 years, there has been great interest in using the frequency analysis of alloreactive helper and cytotoxic T lymphocyte precursors (HTLp and CTLp) to detect recipient-specific alloreactivity and thus predict GVHD in HLA-matched related and unrelated BMT. However, the results remain controversial. The intention of the present study was to investigate whether alloreactive HTLp and CTLp frequencies measured in donor peripheral blood before BMT would be a useful predictor for the occurrence of acute GVHD after HLA-matched sibling BMT. METHOD: A combined limiting dilution assay was used to determine alloreactive HTLp and CTLp frequencies for 42 HLA-matched sibling patient/donor pairs. The pretransplantation host-reactive HTLp and CTLp frequencies were then correlated with post-transplantation clinical outcomes of acute GVHD. The association between HTLp/CTLp frequencies and the incidence of acute GVHD was determined using the Fisher's exact test. RESULTS: The mean values of HTLp and CTLp frequencies for this cohort of HLA-matched sibling patient/donor pairs were 1:321,322 (range 1:71,000 to 1:1000,000) and 1:195,260 (range 1:3,717 to 1:1000,000), respectively. Acute GVHD (> or =II) was observed in one of four patients with high (>1:100,000) HTLp frequencies and 20 of 36 patients with low (<1:100,000) HTLp frequencies. Similarly, 6 of 10 patients with high (>1: 100,000) CTLp frequencies and 14 of 29 patients with low (<1:100,000) CTLp frequencies developed acute GVHD (> or =II). The overall correlation between hostreactive HTLp/CTLp frequencies and the incidence of acute GVHD in this cohort of patients was 42.5% and 53.9%, respectively. There was no significant difference in the incidence of acute GVHD between the patients with either high or low host-reactive HTLp/ CTLp frequencies (P=0.331 and 0.716, respectively). The data were also analyzed separately for the adult patient group based on GVHD prophylaxis with either cyclosporine alone or the combination of cyclosporine and methotrexate. Within these two prophylaxis groups, neither HTLp nor CTLp frequencies correlated with acute GVHD. CONCLUSION: Host-reactive HTLp and CTLp frequency analysis did not provide informative prediction for the occurrence of acute GVHD after HLA-matched sibling BMT.  相似文献   
80.
Immune deficiencies in chronic intestinal pseudo-obstruction   总被引:1,自引:0,他引:1  
Aim: Chronic intestinal pseudo-obstruction has been associated with urinary disorders, myopathy, and ophthalmoplegia in adults and cholelithiasis in children. We observed a high percentage of total-parenteral-nutrition-dependent patients with pseudo-obstruction and recurrent infections requiring gammaglobulin infusions. Methods: AH records for 23 children with chronic intestinal pseudo-obstruction (10 females and 13 males, mean age 9.8 y ± 4.9 y, range 4–24 y) referred for a nutritional evaluation from 1992 to 1995 were reviewed. Chronic intestinal pseudo-obstruction was diagnosed by clinical, radiographic findings and antroduodenal manometry. Intestinal full-thickness biopsies were performed in seven children. Results: Hypogammaglobulinemia was diagnosed in 18 patients (78%): 16 patients had various immunoglobulin deficiencies and 2 had selective antibody deficiency. Intravenous gammaglobulin was administered in 14 patients. Other medical conditions affecting the children are summarized as follows: autonomic dysfunction in 10 patients (43%), recurrent hypoglycemia in 9 (39%), asthma in 9 (39%), cholecystitis in 7 (30%), low serum carnitine level in 6 (26%), urinary dysfunction in 6 (26%), pancreatitis in 5 (22%), behavioral problems in 5 (22%), myopathy in 2 (9%), idiopathic thrombocytopenia in 2 (8%), velopharyngeal insufficiency in 1 (4%), oculocutaneous albinism in 1 (4%), Pierre-Robin syndrome in 1 (4%), and protein C deficiency in 1 (4%). Munchausen syndrome was suspected in two patients. Conclusions: Chronic intestinal pseudo-obstruction appears to be associated with immune deficiencies. It is unclear if the immune deficiencies, intestinal pseudo-obstruction, and the other medical conditions have a common underlying etiology. Repeated infections may be due to impaired immune function in children with chronic intestinal pseudo-obstruction. We recommend screening for immune deficiencies in children with chronic intestinal pseudo-obstruction.  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