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   19849篇
  免费   1260篇
  国内免费   36篇
耳鼻咽喉   120篇
儿科学   690篇
妇产科学   707篇
基础医学   2684篇
口腔科学   264篇
临床医学   3323篇
内科学   3717篇
皮肤病学   203篇
神经病学   1983篇
特种医学   290篇
外科学   1425篇
综合类   249篇
一般理论   31篇
预防医学   2798篇
眼科学   151篇
药学   1157篇
中国医学   13篇
肿瘤学   1340篇
  2023年   91篇
  2022年   160篇
  2021年   333篇
  2020年   214篇
  2019年   377篇
  2018年   388篇
  2017年   278篇
  2016年   355篇
  2015年   405篇
  2014年   602篇
  2013年   962篇
  2012年   1388篇
  2011年   1385篇
  2010年   768篇
  2009年   751篇
  2008年   1354篇
  2007年   1334篇
  2006年   1337篇
  2005年   1366篇
  2004年   1308篇
  2003年   1281篇
  2002年   1240篇
  2001年   152篇
  2000年   132篇
  1999年   167篇
  1998年   251篇
  1997年   219篇
  1996年   180篇
  1995年   190篇
  1994年   169篇
  1993年   164篇
  1992年   137篇
  1991年   117篇
  1990年   107篇
  1989年   110篇
  1988年   105篇
  1987年   107篇
  1986年   76篇
  1985年   82篇
  1984年   117篇
  1983年   89篇
  1982年   125篇
  1981年   103篇
  1980年   106篇
  1979年   57篇
  1978年   65篇
  1977年   43篇
  1976年   49篇
  1975年   30篇
  1974年   38篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
OBJECTIVE: To compare the number of surgical site infections (SSIs) registered after hospital discharge with respect to various surgical procedures and to identify the procedures for which postdischarge surveillance (PDS) is most important. DESIGN: Prospective SSI surveillance with voluntary PDS. Recommended methods for PDS in the Dutch national nosocomial surveillance network are addition of a special registration card to the outpatient medical record, on which the surgeon notes clinical symptoms and whether a patient developed an SSI according to the definitions; an alternative method is examination of the outpatient medical record. SETTING: Hospitals participating in the Dutch national nosocomial surveillance network between 1996 and 2004. RESULTS: We collected data on 131,798 surgical procedures performed in 64 of the 98 Dutch hospitals. PDS was performed according to one of the recommended methods for 31,134 operations (24%) and according to another active method for 32,589 operations (25%), and passive PDS was performed for 68,075 operations (52%). Relatively more SSIs were recorded after discharge for cases in which PDS was performed according to a recommended method (43%), compared with cases in which another active PDS method was used (30%) and cases in which passive PDS was used (25%). The highest rate of SSI after discharge was found for appendectomy (79% of operations), followed by knee prosthesis surgery (64%), mastectomy (61%), femoropopliteal or femorotibial bypass (53%), and abdominal hysterectomy (53%). CONCLUSIONS: For certain surgical procedures, most SSIs develop after discharge. SSI rates will be underestimated if no PDS is performed. We believe we have found a feasible and sensitive method for PDS that, if patients routinely return to the hospital for a postdischarge follow-up visit, might be suitable for use internationally.  相似文献   
992.

Background  

An increasing number of medical specialists prefer to work part-time. This development can be found worldwide. Problems to be faced in the realization of part-time work in medicine include the division of night and weekend shifts, as well as communication between physicians and continuity of care. People tend to think that physicians working part-time are less devoted to their work, implying that full-time physicians complete a greater number of tasks. The central question in this article is whether part-time medical specialists allocate their time differently to their tasks than full-time medical specialists.  相似文献   
993.
This contribution assesses who is at risk of osteoporosis, by delineating the key risk factors involved in the condition. Osteoporosis represents a major public health problem through its association with fragility fractures, primarily of the hip, spine and distal forearm. Some risk factors for fragility fracture act through bone mineral density (BMD), for example female gender, asian or Caucasian race, premature menopause, primary or secondary amenorrhoea, primary and secondary hypogonadism in men, prolongued immobilisation, low dietary calcium intake, vitamin D deficiency. However, a number of others contribute significantly to fracture risk over and above their association with BMD (age, high bone turnover, poor visual acuity, neuromuscular disorders, previous fragility fracture, glucocorticoid therapy, family history of hip fracture, low body weight, cigarette smoking, excess alcohol consumption).  相似文献   
994.
995.
Functional neuroimaging in child psychiatry   总被引:2,自引:0,他引:2  
Functional neuroimaging in child psychiatry presents unique scientific, ethical, and technical challenges. The study of childhood disorders presupposes knowledge of neurodevelopment and brain maturation. However, much of human brain science is based on inferences from animal work and indirect neurochemical measures from body fluids. Neuroimaging can examine brain development directly in humans. The benefits can be enormous for learning how and when to intervene to prevent or treat a disorder. These unprecedented potential gains are countered by complex and difficult ethical issues. Technical advances can reduce ethical concerns by minimizing risks. They also promise to enhance the sensitivity and specificity of the measures (eg, by improving spatial and temporal resolution). Judiciously designed investigations will permit the testing of a priori hypotheses built on rational models of neuropathology. Finally, it is the integration of scientific knowledge across the various fields of neuroscience and clinical research that will push the limits of our understanding of health and disease.  相似文献   
996.
The purpose of this analysis was to determine the prevalence and correlates of HIV infection among a street-recruited sample of heroin-and cocaine-using men who have sex with men (MSM). Injection (injecting ≦3 years) and non-injection drug users (heroin, crack, and/or cocaine use<10 years) between 18 and 40 years of age were simultaneously street-recruited into two cohort studies in New York City, 2000–2003, by using identical recruitment techniques. Baseline data collected among young adult men who either identified as gay/bisexual or reported ever having sex with a man were used for this analysis. Nonparametric statistics guided interpretation. Of 95 heroin/ cocaine-using MSM, 25.3% tested HIV seropositive with 75% reporting a previous HIV diagnosis. The majority was black (46%) or Hispanic (44%), and the median age was 28 years (range 18–40). HIV-seropositive MSM were more likely than seronegatives to be older and to have an HIV-seropositive partner but less likely to report current homelessness, illegal income, heterosexual identity, multiple sex partners, female partners, and sex for money/drug partners than seronegatives. These data indicate high HIV prevalence among street-recruited, drug-using MSM compared with other injection drug use (IDU) subgroups and drug-using MSM; however, lower risk behaviors were found among HIV seropositives compared with seronegatives. Large-scale studies among illicit drug-using MSM from more marginalized neighborhoods are warranted.  相似文献   
997.
Families of persons with mental illness often benefit from participating in interventions which provide education and support. The present study describes outcomes reported by 424 families who participated in one such intervention, the Journey of Hope (JOH) program. Hierarchical regression analyses found that program outcomes—increased knowledge of the causes and treatment of mental illness, increased understanding of the mental health service system, and improved morale—were predictive of one another. JOH therefore may provide families with the knowledge and support they need to strengthen their ability to cope with their relative's mental illness.  相似文献   
998.
Association studies on susceptibility to breast cancer using single nucleotide polymorphisms (SNP) in the progesterone receptor (PGR) gene have been previously published, but the results have been inconclusive. We used a comprehensive SNP-tagging approach to search for low-penetrance susceptibility alleles in a study of up to 4,647 cases and 4,564 controls, in a two-stage study design. We identified seven tagging SNPs using genotype data from the National Institute of Environmental Health Sciences (NIEHS) Environmental Genome Project and typed these, and an additional three SNPs, in 2,345 breast cancer cases and 2,284 controls (set 1). Three SNPs showed no evidence for association and were not studied further, whereas seven SNPs (rs11571171, rs7116336, rs660149, rs10895068, rs500760, rs566351, and rs1042838) exhibited significant associations at P < 0.1 using either a heterogeneity or trend test and progressed to be genotyped in set 2. After both stages, only one SNP was significantly associated with an increased risk of breast cancer - the PGR-12 (rs1042638) V660L valine to leucine polymorphism [VL heterozygotes (odds ratio, 1.13; 95% confidence interval, 1.03-1.24) and the LL homozygotes (odds ratio, 1.30; 95% confidence interval, 0.98-1.73), P(het) = 0.008, P(trend) = 0.002]. Similar estimates were obtained in a combined analysis of our data with those from three other published studies. We conclude that the 660L allele may be associated with a moderately increased risk of breast cancer, but that other common SNPs in the PGR gene are unlikely to be associated with a substantial risk of breast cancer.  相似文献   
999.
Previous studies have identified low patient accrual in large-scale cancer clinical trials, particularly for underrepresented groups, such as ethnic minorities, females, and patients >65 years. As there have been few studies examining participation in cancer genetics epidemiologic research, our objective was to identify clinical and demographic factors predicting enrollment in these studies. A total of 1,111 patients diagnosed with colorectal cancer presenting to a gastrointestinal oncology clinic were approached to enroll in a study investigating the role of the MSH6 gene in familial colorectal cancer. Patient consent was sought for providing a blood specimen for DNA analysis and review of medical records/tumor specimens and contacting family members to confirm the family history of cancer. Seven predictor variables for enrollment (age, sex, ethnicity, family history of colorectal cancer in a first-degree relative, presence of children, insurance type, and type of visit) were analyzed using logistic regression analysis to determine the effect on decision to enroll. Of 1,111 patients approached, 696 (62.6%) enrolled in the study. Of these approached individuals, 4.2% were of nonwhite ethnicity and 33.5% were age > or =65 years. Patients of white ethnicity [odds ratio (OR), 2.10; P = 0.018], males (OR, 1.47; P = 0.002), those ages < or =65 years (OR, 1.42; P = 0.009), and those with a first-degree relative with colorectal cancer (OR, 1.57; P = 0.005) were significantly more likely to enroll. Fewer than 4% of all participants denied permission for the study researchers to access information from medical records or to be recontacted by researchers to discuss the enrollment of additional family members. Our data suggest that, once subjects decided to enroll, the majority (88%) was comfortable with consenting to all study components, including the creation of cell lines and future recontact. Low participation rates for ethnic minorities, females, and elderly patients are similar for both cancer genetics and clinical trial studies.  相似文献   
1000.
CONTEXT: Through medical decision making, physicians in the U.S. influence the spending of >$1.3 trillion or 15% of the gross domestic product. U.S. physicians are challenged to identify areas of clinical practice to improve while cutting cost and increasing access. Primary screening for colorectal cancer is a good example to illustrate this point.OBJECTIVE: To apply a population-based method of medical decision making in the area of primary screening for colorectal cancer in order to illustrate a reduction in health care costs while increasing access and maintaining quality of care.DESIGN: We used a combination of (a) census population data, (b) National Cancer Institute Survey data on screening rates, and (c) charge data to estimate the current costs of colorectal cancer screening. We also estimated cost and capacity increases that would occur under various other screening scenarios. These included all currently screened subjects receiving annual fecal occult blood testing (FOBT), all currently unscreened individuals undergoing either colonoscopy every decade or annual FOBT, and all eligible subjects undergoing annual FOBT.Main outcome measures: Cost and access differences between current screening activity and other potential scenarios compliant with guidelines.RESULTS: Screening for colorectal cancer with yearly, six-window, rehydrated FOBT for all normal-risk individuals over the age of 50 has the potential to screen 3,813,095 more Americans for colon cancer yearly than are currently being screened, while costing $8.7 billion less per decade than what is currently being spent on screening a fraction of the population. Looking into the future, it is possible to increase screening rates from 50% to 100%, while saving almost $10 billion per decade by using FOBT for all eligible Americans. In practice, some proportion of these benefits would be realized as the calculations assume a 100% patient compliance rate.CONCLUSIONS: Considering a population-based approach and the balance among quality, accessibility, and cost parameters, we recommend primary screening for colorectal cancer to be based on yearly six-window, rehydrated FOBT. Colonoscopy due to cost and access issues should be relegated to secondary screening and case finding.  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