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   937篇
  免费   74篇
  国内免费   2篇
耳鼻咽喉   7篇
儿科学   40篇
妇产科学   35篇
基础医学   167篇
口腔科学   7篇
临床医学   54篇
内科学   205篇
皮肤病学   32篇
神经病学   68篇
特种医学   14篇
外科学   76篇
综合类   5篇
预防医学   54篇
眼科学   29篇
药学   99篇
中国医学   3篇
肿瘤学   118篇
  2022年   9篇
  2021年   19篇
  2020年   10篇
  2019年   22篇
  2018年   21篇
  2017年   17篇
  2016年   20篇
  2015年   24篇
  2014年   34篇
  2013年   52篇
  2012年   62篇
  2011年   80篇
  2010年   53篇
  2009年   40篇
  2008年   79篇
  2007年   60篇
  2006年   66篇
  2005年   65篇
  2004年   52篇
  2003年   41篇
  2002年   34篇
  2001年   11篇
  2000年   6篇
  1999年   3篇
  1998年   7篇
  1997年   3篇
  1996年   3篇
  1995年   3篇
  1993年   4篇
  1992年   9篇
  1991年   6篇
  1990年   4篇
  1989年   7篇
  1988年   3篇
  1987年   4篇
  1986年   5篇
  1985年   9篇
  1984年   7篇
  1983年   7篇
  1980年   4篇
  1976年   3篇
  1974年   5篇
  1973年   5篇
  1972年   2篇
  1970年   4篇
  1969年   2篇
  1968年   3篇
  1966年   4篇
  1964年   2篇
  1961年   2篇
排序方式: 共有1013条查询结果,搜索用时 796 毫秒
1.
2.
The relationship between the use of cigarettes and other tobacco products and the risk of multiple myeloma was examined in a cohort of nearly 250,000 American veterans followed prospectively for 26 years. Compared with men who had never used tobacco, the risk of death from myeloma was not increased among current (relative risk [RR]=0.9, 95 percent confidence interval [CI]=0.8–1.2) or former (RR=1.0, CI=0.8–1.3) cigarette smokers, nor among users of chewing tobacco or snuff (RR=1.0, CI=0.4–2.3). Risk was only slightly and nonsignificantly increased among pipe or cigar smokers (RR=1.2, CI=0.9–1.5). There was no indication of increasing risk with amount of tobacco used or earlier age at first use. With over 90 percent power to detect a 30 percent increased risk of this tumor occuring among current cigarette smokers, this study provides the strongest evidence to date against an association of cigarette smoking with multiple myeloma.Epidemiology and Biometry Program, Division of Cancer Etiology, National Cancer Institute. Westat, Inc. Rockville, MD. National Cancer Institute, 6130 Executive Blvd, Room 418, Rockville, MD 20892, USA.  相似文献   
3.
A single-purpose analogue-computing device is described for the online assessment of the contractile state of the human myocardium from the left ventricular pressure (Plv) data available during routine cardiac catheterisation. Due attention has been paid to the design of the computer circuits so that they will not process pressure phenomena outside the isovolumic contractile period. Either a \(\left( {\frac{1}{{P_{lv} }}\frac{{dP_{lv} }}{{dt}}} \right)_{max} \) or a plain \(\left( {\frac{{dP_{lv} }}{{dt}}} \right)_{max} \) index is presented on a digitalvoltmeter display, thus obviating the need for any graphical extrapolation or additional computation.  相似文献   
4.
5.
The proposed dielectrical relaxation model of the myocardium in the microwave spectrum has been verified both on test solutions and on normal canine myocardium. Furthermore, the model was utilized to reconstruct the changes in tissue properties (including myocardial bulk resistance and water content) following myocardial acute ischemia and chronic infarction. It was shown that the reconstructed myocardial resistance and water content correlate dynamically with the process of the development of acute myocardial ischemic injury. In chronic cases the reconstructed resistance and water content of infarcted myocardium are significantly different from that of normal myocardium: the resistance is lower and water content is higher than in normal myocardium. © 2000 Biomedical Engineering Society. PAC00: 8764-t, 8719Xx  相似文献   
6.
Postnatal mice lacking neurotrophin-3 (NT3) are deficient in Merkel cells of touch domes and whisker follicles. We examined the mechanism of Merkel cell loss by immunocytochemistry and electron microscopy. Merkel cell of whisker follicles of NT3 null newborns exhibited decreased immunoreactivity for cytokeratin 8 and contained apoptotic bodies that were positive for cleaved caspase-3, a marker of active apoptosis. By electron microscopy, the Merkel cells displayed aggregation of chromatin along the nuclear membrane, with the marginated chromatin forming caps at the periphery of the nucleus. Ribosomes aggregated in the cytoplasm, while dense core granules characteristic of Merkel cells were still discernible. Finally, the Merkel cells and their nuclei fragmented into apoptotic bodies. None of the apoptotic Merkel cells were contacted by nerve fibers, and their desmosomal contacts with surrounding keratinocytes disappeared. After postnatal day 6 apoptotic Merkel cells were no longer observed, and the number of surviving Merkel cells was severely reduced. They were flat and contained few osmiophilic granules. We conclude that perinatal apoptosis is responsible for the loss of Merkel cells lacking innervation in NT3 null mice.  相似文献   
7.
This cooperative prospective study was designed to answer the following questions in cases with acute lymphoblastic leukemia induced to achieve complete remission with the combination of vincristine and prednisone (if by day 29 the bone marrow was not M1, daunorubicin was added to the former regimen) and who received preventive CNS therapy with 2400 rad of cobalt-60 to craniocervical region and simultaneously intrathecal methotrexate and dexamethasone: 1) Is a short intensification with cytosine-arabinoside and cyclophosphamide immediately after complete remission useful? 2) Does the use of weekly doses of 6-mercaptopurine and methotrexate have the same maintenance effect as daily 6-mercaptopurine and twice weekly methotrexate? and 3) Do further 3 month-doses of intrathecal methotrexate and dexamethasone help to decrease still more the incidence of meningeal leukemia? From October 1972 to December 1975, 473 previously untreated patients entered this study and 465 (390 children and 75 adults) are evaluated in this paper. Of them, 373 (80%) achieved complete remission (children 84% and adults 61%). Out of 109 "high risk" children (one or more of the following characteristics at diagnosis: marked organomegaly, mediastinal widening, leukocytosis above 50000/mm3 and CNS involvement) 83 (76%) and out of 281 "standard risk" children (all the others) 244 (87%) achieved complete remission. The median duration of complete remission according to different prognostic factors was as follows: "high risk" children 10 months, adults 24 months and "standard risk" children 25 months. Duration of complete remission of the "standard risk" children in relation to with or without intensification, daily or weekly maintenance and additional intrathecal therapy or none, showed no significant difference; however, those who received intensification, daily maintenance and further intrathecal therapy behaved slightly better. Median survival for all the cases of this study was as follows: adults 10 months, "high risk" children 12 months and "standard risk" children 26 months. At 36 months, 13% of "high risk" children, 25% of adults and 39% of "standard risk" children are still alive. We conclude that the variables studied in this protocol did not show significant extension of complete remission, however the sum of them seems to offer some advantage. Moreover, what appears clear is the importance of prognostic factors which must be taken into account in future studies.  相似文献   
8.
9.
This retrospective study assesses and compares perioperative parameters in two groups of patients treated by different operative techniques of laparoscopic surgical staging (LASS) for uterine cancer. Between April 1996 and May 2005, 119 consecutively selected women with cervical cancer (n=30) or clinical stage I endometrial cancer (n=89) underwent laparoscopic assisted vaginal hysterectomy (LAVH), total laparoscopic hysterectomy (TLH) or radical laparoscopic assisted vaginal hysterectomy (RALVH) plus bilateral salpingo-oophorectomy (BSO) and/or lymph node dissection (LND) during a primary surgical procedure using an electrosurgery (ELC, n=37) or ultrasonic (US, n=82) operative technique (harmonic shears, UltraCision). The UltraCision was used as a primary method of dissection and hemostasis from 1999. We were unable to perform prompt and thorough hemostasis in 2 patients from the US group (successful procedure rate 97.5%) because of ineffective post-ultrasonic coagulation of venous paravaginal varices (RALVH procedure) and of vena ovarica varices (LAVH, BSO procedure). The UltraCision was effective in all cases of lymphadenectomy. Successful procedure rate of the ELC operative technique was 100%. There were no statistically significant differences between the groups with regard to operation time, blood loss, hospital stay, and complications. There was a significant difference (P<0.001) in the number of lymph nodes harvested: a mean of 18.1 in the US group and 13.7 in the ELC group. We think that the difference was influenced by an increase in experience with laparoscopic lymph node dissection. The UltraCision operative technique ensures efficient dissection, coagulation, cutting, and grasping for LASS in women with cervical and endometrial cancer.  相似文献   
10.
Objective: Alendronate and calcitonin are antiresorptive drugs that were used for the treatment of postmenopausal osteoporosis and were shown to increase bone mineral density (BMD). However, the effect of both drugs in daily clinical practice may differ from that observed in clinical trials.Method: About 50 postmenopausal osteoporotic women were observed during their first year of treatment. Among them, 32 patients used alendronate and 18 used calcitonin. Lumbar spine and femoral neck BMD were measured by dual energy X-ray absorptiometry (DXA) at baseline and after 1 year of therapy. Biochemical markers (B-ALP – bone-specific alkaline phosphatase, OTC – osteocalcin and DPD/UCr – deoxypyridinoline/creatinine ratio) of bone metabolism were measured at baseline and 6 months later. Patient compliance was assumed by tablet counting and verified at interview. Each patient was further questioned about her attitude towards the treatment, as well as her dairy product intake, physical activity, use of other medications, smoking and social status.Main outcome measure: (1) Annual percent change in BMD in lumbar spine and femoral neck after the one-year treatment with either alendronate or calcitonin. (2) The change in biochemical markers of bone turnover.Results: The lumbar spine BMD significantly increased by 7.0% (P < 0.001), the femoral neck BMD by 4.3% (P < 0.01). OTC, B-ALP and DPD/UCr decreased significantly during the therapy with alendronate. Compliance with therapy was 79% (95% CI 68–90%). In the calcitonin-treated group, the lumbar spine BMD significantly increased by 3.1 % (P < 0.05), while the femoral neck BMD remained unchanged. OTC, B-ALP and DPD/UCr did not change significantly during the treatment with calcitonin. Compliance with calcitonin therapy was 87% (95% CI 63–110%). The annual change of BMD in both treatment groups was independent on all questioned factors.Conclusion: In daily practice, alendronate enhanced significantly BMD both in lumbar spine and femoral neck. Calcitonin showed increase only in the lumbar spine BMD.  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