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   997468篇
  免费   75308篇
  国内免费   2618篇
耳鼻咽喉   12962篇
儿科学   34467篇
妇产科学   28460篇
基础医学   145306篇
口腔科学   27714篇
临床医学   90265篇
内科学   193625篇
皮肤病学   22913篇
神经病学   79115篇
特种医学   38386篇
外国民族医学   305篇
外科学   149497篇
综合类   23740篇
一般理论   385篇
预防医学   77817篇
眼科学   22608篇
药学   71863篇
  3篇
中国医学   2034篇
肿瘤学   53929篇
  2018年   10557篇
  2017年   8235篇
  2016年   9373篇
  2015年   10596篇
  2014年   14416篇
  2013年   22001篇
  2012年   28987篇
  2011年   30828篇
  2010年   18487篇
  2009年   17439篇
  2008年   28790篇
  2007年   30466篇
  2006年   30962篇
  2005年   29638篇
  2004年   28927篇
  2003年   27801篇
  2002年   26817篇
  2001年   46924篇
  2000年   48036篇
  1999年   40263篇
  1998年   11182篇
  1997年   10097篇
  1996年   10161篇
  1995年   9775篇
  1994年   9090篇
  1993年   8480篇
  1992年   32248篇
  1991年   31459篇
  1990年   31006篇
  1989年   29874篇
  1988年   27167篇
  1987年   27325篇
  1986年   25434篇
  1985年   24601篇
  1984年   18397篇
  1983年   15515篇
  1982年   9288篇
  1981年   8375篇
  1979年   16859篇
  1978年   12218篇
  1977年   10314篇
  1976年   9755篇
  1975年   10178篇
  1974年   12317篇
  1973年   11843篇
  1972年   10884篇
  1971年   10113篇
  1970年   9375篇
  1969年   8725篇
  1968年   8104篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
101.
Serum bone-gla protein after fracture   总被引:2,自引:1,他引:1  
Serum bone Gamma-carboxyglutamic acid (bone-gla) protein (BGP), a marker of bone formation, was measured in serial blood samples drawn from 14 patients who had fractured at least one of their tibial or femoral diaphyses and from two other patients who had sustained major trauma without fracture but who had been immobilized. A total of 85 samples were taken and analyzed during the first three months after the fractures occurred. Serum BGP significantly increased and positively correlated with the time that had elapsed after the fracture, with an average twofold increase after two months. The fracture site and the duration of immobilization had no influence on the serum BGP levels. Serum BGP levels from the two non-fractured cases increased in the first two weeks with no subsequent consistent trend. These data suggest that serum BGP increases one to two months after a major fracture, possibly as a manifestation of bone repair. Further studies are required to determine the potential clinical value of serum BGP in the management of such patients.  相似文献   
102.
Study Objective . To characterize cytochrome P450 (CYP) 3A4 activity in premenopausal and postmenopausal women by evaluating the urinary 6-β-hydroxycortisokcortisol ratio. Design . Prospective study. Subjects . Thirteen premenopausal and 13 postmenopausal women who were healthy and not receiving drugs known to affect CYP3A4 activity. Interventions . Beginning on day 2 of menses, premenopausal women collected first morning urine samples every other day for a complete menstrual cycle. Postmenopausal women collected first morning urine every other day for 28 days. Measurements and Main Results . Mean weekly 6-β-hydroxycortisol:cortisol ratios did not differ during the phase (week) of the menstrual cycle. Daily ratios did not differ in postmenopausal women. No difference between premenopausal and postmenopausal women was found on comparing overall median ratios. Conclusion . Cytochrome P450 3A4 activity as measured by 6-β-hydroxy cortisol:cortisol ratio did not differ by week of menstrual cycle, suggesting no menstrual cycle-related changes. Menopause does not appear to be associated with differences in CYP3A4 activity, compared with premenopause.  相似文献   
103.
OBJECTIVE: To determine the most frequent clinical causes of a prolonged activated partial thromboplastin time (APTT) result, and to determine whether a new heparin-removal device (the Hepchek, Pall Biomedical, Glen Cove, NY 11542) is capable of efficiently detecting the causes of these values. DESIGN: A combination of chart review and laboratory testing comparing the criterion standard--the heparin chromogenic substrate assay--with the Hepchek. Laboratory investigations were blinded and controlled. SETTING: Inpatient, acute-care hospital. PATIENTS: A total of 1,000 hospital patients with a variety of hemostatic disorders. MAIN OUTCOME MEASURE: The extent to which the Hepchek accurately identified the etiology of a prolonged APTT result. RESULTS: The APTT was prolonged in 25.2% of samples. The presence of heparin in the sample was confirmed by chromogenic assay or by using the Hepchek heparin-removal filter. The presence of heparin was confirmed in 12.8% of all samples and in more than 50% of all abnormal samples. The cause of the abnormal APTT was often unappreciated by the clinician. Bayesian analysis of the Hepchek's ability to diagnose heparin correctly as the cause of the abnormal APTT showed a sensitivity of 100% and specificity of 99.9%. CONCLUSION: Use of the Hepchek in the routine clinical laboratory is an efficient and rapid method of detecting heparin as a cause of isolated prolonged APTT results, and should reduce demands for unwarranted coagulation analyses and inappropriate treatment with blood products.  相似文献   
104.
Depression continues to be a major cause of morbidity and mortality in the elderly. It is estimated that 1–5% of elderly persons who live in the community and 5–43% of nursing–home patients have major depression. Symptoms of depression in the elderly do not differ substantially from younger patients. Tricyclic antidepressants continue to be the drugs of choice in the elderly because of their long record of use with proven efficacy, known adverse effect profile and availability of less expensive generic formulations. The newer secondgeneration antidepressants, including serotonin reuptake inhibitors, appear to offer a major advantage of fewer serious adverse effects in the elderly. This review will highlight recent developments regarding the prevalence and treatment of depression in the elderly.  相似文献   
105.
In contrast with cross-sectional designs used in previous studies, this exploratory study compared survey data from 127 matched pairs of clinical pharmacists and physicians working together. Physicians' perceptions of the importance of clinical pharmacy activities for patient care and the competence of pharmacists performing the activities were examined for their influence on prescribing behavior in an institutional setting. Data from a national survey showed that physicians rated pharmacists higher regarding recommendations based on drug use evaluations (p = 0.004) and competency to provide all clinical pharmacy services. Scores for pharmacokinetics ratings were similar between pharmacists and physicians (p = 0.168). Pharmacists rated the importance of recommendations based on cost-effectiveness higher than physicians (p = 0.012). Overall, physicians' perceptions of activity importance for patient care and pharmacist competency appear to dictate pharmacists' influence on physician prescribing behavior (R = 0.723).  相似文献   
106.
Anti-HPA-1a platelet antibody levels in pregnant women with a history of fetomaternal alloimmune thrombocytopenia (FMAIT) were monitored longitudinally using the monoclonal antibody immobilisation of platelet antigens (MAIPA) assay, in order to examine any variation in optical density (OD) readings obtained over the course of pregnancy and after delivery. Seven women were selected; 4 were studied retrospectively and 3 prospectively (the latter being treated with intravenous gammaglobulin; IVGG). Levels of anti-HPA-1a were measured at various intervals after delivery of the first affected infant, to post delivery of the following affected infant. A decrease in MAIPA OD was demonstrated in all patients during the course of these pregnancies. This assay is a useful tool for monitoring anti-HPA-1a in women with a history of infants affected with FMAIT. A maternal antibody 'resting' level prior to, or early in the first trimester, must be established for comparison.  相似文献   
107.
SUMMARY. Samples from 1828 donations were screened for anti-HBc at seven sites in the UK using kits supplied by 10 manufacturers. Only 10 (0.55%) donations were considered to have true anti-HBc reactivity and these were detected by all 10 kits. Additional markers of HBV infection were found in nine of these 10 donations. Additional reactives were found by all kits, the number ranging from 1 to 43.
In the four more specific kits, the 10 true reactives were clearly distinguished from the 'false reactives' by the strength of the reaction. It is concluded that the reliance on a single ELISA test for anti-HBc diagnosis is unwise. The use of a second test known to be more specific than the screening ELISA is recommended.  相似文献   
108.
109.
A mouse monoclonal antibody (MAb 6B9, isotype IgM) was raised against autopsy tissue samples from the central nervous system (CNS) of multiple sclerosis (MS) patients. By immunofluorescence microscopy, MAb 6B9 intensely stains most or all cells in fetal rats. However, MAb 6B9 differentially stains various cell types in adult rats. Neurons, ependymal cells, and adrenal chromaffin cells are stained intensely, whereas astrocytes and oligodendrocytes are not stained. The 6B9-reactive antigen (6B9 antigen) is sensitive to periodic acid, but insensitive to treatment with protease, RNase, or hyaluronidase. Results from immunofluorescence microscopy on semithin sections and cultured neuroblastoma cells indicate that 6B9 antigen is intracellular. This is supported by immunoelectron microscopy, where labeling for 6B9 antigen appears in the cytoplasm distinct from any identifiable organelle. Further studies on 6B9 antigen should reveal its chemical nature as well as the significance of developmental changes in its distribution.  相似文献   
110.
To determine the potential effect of screening on referral patterns, an adult population sample (4,404 men, 5,164 women, 20-69 years of age) was systematically recruited and screened for hypercholesterolemia and then analyzed by different cholesterol referral recommendations. Using levels suggested by the Lipid Research Clinics Coronary Primary Prevention Trial (greater than or equal to 265 mg/dL), 7.3% of men and 5.8% of women would be referred for follow-up. With the suggested recommendations of the National Cholesterol Education Program (NCEP), (greater than or equal to 200 mg/dL), 49.2% of men and 40.2% of women would be referred. The use of age-related definitions of the NIH Consensus Conference on Lipid Lowering results in 28.0% referrals in men and 21.8% in women. From this population, hypercholesterolemia subjects (greater than or equal to 265 mg/dL at screening; n = 624) were invited for a second cholesterol determination (58% returned), which found 36% below the 265 mg/dL level. Population screening for cholesterol is likely to produce large numbers of patients for follow-up, with the actual numbers strongly dependent on cutoff levels and age-sex distributions. Referral and follow-up of these patients may place a significant load on an unprepared health care community.  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