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   21631篇
  免费   1831篇
  国内免费   60篇
耳鼻咽喉   220篇
儿科学   636篇
妇产科学   486篇
基础医学   2835篇
口腔科学   506篇
临床医学   2558篇
内科学   3921篇
皮肤病学   317篇
神经病学   1987篇
特种医学   778篇
外科学   2683篇
综合类   615篇
一般理论   24篇
预防医学   2186篇
眼科学   494篇
药学   1650篇
中国医学   16篇
肿瘤学   1610篇
  2021年   267篇
  2020年   184篇
  2019年   258篇
  2018年   347篇
  2017年   262篇
  2016年   311篇
  2015年   348篇
  2014年   443篇
  2013年   734篇
  2012年   1006篇
  2011年   965篇
  2010年   570篇
  2009年   510篇
  2008年   903篇
  2007年   994篇
  2006年   913篇
  2005年   884篇
  2004年   872篇
  2003年   810篇
  2002年   825篇
  2001年   648篇
  2000年   596篇
  1999年   546篇
  1998年   340篇
  1997年   291篇
  1996年   322篇
  1995年   274篇
  1994年   256篇
  1993年   256篇
  1992年   432篇
  1991年   422篇
  1990年   459篇
  1989年   441篇
  1988年   421篇
  1987年   401篇
  1986年   394篇
  1985年   338篇
  1984年   293篇
  1983年   221篇
  1982年   166篇
  1981年   157篇
  1980年   159篇
  1979年   258篇
  1978年   184篇
  1977年   167篇
  1976年   160篇
  1975年   178篇
  1974年   172篇
  1973年   133篇
  1972年   141篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
This paper reports the results of a survey in which pregnant women in London and Edinburgh were asked about their knowledge and understanding of the recent recommendations of expert committees (James, 1983; DHSS, 1984). In general, Londoners had a better understanding, although in both regions manual groups were less knowledgeable, with the Edinburgh manual group the least well informed.  相似文献   
72.
1. The kidney bean lectin, phytohaemagglutinin (PHA), induced a marked atrophy of skeletal muscle which was evident from the changes in tissue composition (protein, RNA, DNA and polyamine content) and from the reduction in weight and protein synthesis of hind leg muscles of rats fed on kidney bean-diets for four days. The beta-adrenoceptor agonist, clenbuterol, induced skeletal muscle hypertrophy by transiently stimulating protein synthesis. As a consequence, the muscle loss caused by a short exposure to PHA was, in part, ameliorated by clenbuterol treatment. 2. Cardiac muscle was affected to a lesser extent than skeletal muscle by both clenbuterol and the lectin. However, there was evidence that protein synthesis in heart was reduced by PHA. 3. PHA had opposite effects on the gut, the lectin-induced hyperplasia of the jejunum was accompanied by a large increase in protein synthesis. Clenbuterol alone had no effect on the jejunum whereas a combination of PHA and clenbuterol appeared to exacerbate the effect of the lectin on gut. 4. Both the lectin-induced gut growth and the hypertrophy of skeletal muscle caused by clenbuterol were preceded by the accumulation of polyamines in the respective tissues. Of particular note was the observation that a significant increase in the proportion of the intraperitoneally injected 14C-labelled spermidine or putrescine taken up by the growing tissues could be detected by the second day. Therefore, the measurement of uptake of labelled polyamines may be used as a sensitive indicator of early alterations in tissue metabolism.  相似文献   
73.
OBJECTIVE: This study prospectively evaluates the effectiveness and patient acceptability of professionally-led support groups in alleviating psychologic distress in infertility patients. METHOD: Sixty-four consecutive patients in a university hospital infertility program were administered a battery of psychologic tests before and after attendance at an 8 weekly session support group. The comparison group consisted of 35 consecutive infertility referrals to the same unit who were not initially offered the support group and were similarly tested over an 8 week period. RESULTS: Support group patients had significantly greater (p less than or equal to 0.01) entry than exit scores on several measures of psychologic distress and depression (the Beck Depression Inventory, the Hamilton Rating Scale for Depression, and the Global Severity Index, Anxiety, Depression, Hostility and Obsessive Compulsive Subscales of the Brief Symptom Inventory). The Avoidance Coping Style on the Moos Coping Responses Inventory was correlated with a higher Global Severity Index (p less than or equal to 0.01). Comparison group patients had similar psychometric scores to the support group patients at entry but showed no change over 8 weeks. Attenders expressed a high rate of satisfaction with the support group. CONCLUSIONS: Professionally-led support groups are a highly acceptable and effective intervention in self-referred patients in alleviating psychological distress related to infertility.  相似文献   
74.
OBJECTIVES: The purpose of this study was to develop and evaluate models for public health surveillance of illnesses among children in out-of-home child care facilities. METHODS: Between July 1992 and March 1994, 200 Seattle-King County child care facilities participated in active or enhanced passive surveillance, or both. Reporting was based on easily recognized signs, symptoms, and sentinel events. Published criteria were used in evaluating surveillance effectiveness, and notifiable disease reporting of participating and nonparticipating facilities was compared. RESULTS: Neither surveillance model was well accepted by child care providers. Enhanced passive and active surveillance had comparable sensitivity. Reporting delays and the large amount of time needed for data entry led to problems with timeliness, especially in terms of written reporting during active surveillance. CONCLUSIONS: Widespread active public health surveillance in child care facilities is not feasible for most local health departments. Improvements in public health surveillance in child care settings will depend on acceptability to providers.  相似文献   
75.
D Stewart  R B Leman  J Kaiser  D L Mann 《Chest》1991,99(3):651-655
The incidence and severity of catheter-induced tricuspid regurgitation has not been studied extensively. Given the frequency with which right heart catheters are employed to measure cardiac output, it is important to know whether the severity of catheter-induced tricuspid regurgitation is sufficient to invalidate the measurement of thermodilution cardiac output. Accordingly, the purpose of the present prospective study was to determine the incidence and severity of catheter-induced tricuspid regurgitation in 25 men (mean age, 58.1 +/- 1.4 years) using Doppler ultrasound. The tricuspid valve was interrogated from two orthogonal views using pulsed-wave and color flow Doppler, either in the presence or absence of a 7-French catheter across the tricuspid valve. The severity of catheter-induced tricuspid regurgitation was graded semiquantitatively using a validated scoring system. Pulsed-wave Doppler studies showed that the incidence of catheter-induced tricuspid regurgitation was 48 percent, and that the average tricuspid regurgitation score increased from 0.41 +/- 0.16 to 0.61 +/- 0.17 (p less than 0.01). Color flow Doppler studies showed similar findings. Further, the incidence of catheter-induced tricuspid regurgitation was not related to the patient's underlying hemodynamic status or right ventricular geometry. In conclusion, this study shows for the first time that the quantitative extent of catheter-induced tricuspid regurgitation is small, and is therefore unlikely to be important clinically, particularly with regard to the assessment of thermodilution cardiac output.  相似文献   
76.
Pediatric knee MR imaging: pattern of injuries in the immature skeleton   总被引:3,自引:0,他引:3  
  相似文献   
77.
Alcoholics admitted to the hospital solely for detoxication have been studied by flow cytometry to evaluate changes in the surface markers of peripheral blood leukocytes. As we have shown previously, such patients have an elevated percentage of CD8hl lymphocytes that are HLA DR+; we now demonstrate that they also have striking alterations in the quantitative relationships of the fine T-cell subsets. Both CD4+ and CD8hl lymphocytes have a sharply reduced percentage of the l -selectin+ CD45RA+ subset, increased percentages of the CD45RA-subsets, and several other fine subset alterations. The fine subset profile suggests, according to current correlations of phenotype and function, that both CD4+ suppressor inducer and CD4-dependent CD8+ suppressor effector cells are reduced, whereas other subsets, including CD8+ CTL or their precursors, are increased in relative percentages. Some of the phenotypic changes are reversible over the several days following withdrawal. In other results, the percentage of CD8hl lymphocytes expressing CD11b (β-integrin) is shown to be reciprocal with the percentage expressing l -selectin both in normals and alcoholics. However, the regression function of CD11b vs. l -selectin on CD8hl cells is different for the alcoholics than for the normals, indicating an abnormality in the regulation of the expression of these two adhesion markers. Taken together, this abnormality of adhesion molecules and the fine subset alterations previously described indicate widespread changes in the peripheral lymphocytes of currently drinking alcoholics. These changes suggest functional deficiencies that may include alterations of lymphocyte traffic and other adhesion-dependent functions, and a shift in the balance of regulatory interactions.  相似文献   
78.
Treatment with the monoclonal antibody OKT3 specific for the CD3 complex associated with the T cell antigen receptor can reverse acute rejection of human renal allografts. However, efficacy of anti-CD3 antibodies for treatment of patients with acute graft-versus-host disease after marrow transplantation has not been established. The dose-limiting side effects resulting from T cell activation induced by some anti-CD3 antibodies in vivo have discouraged their use for this application. We now report a phase I-II study of GVHD treatment with the anti-CD3 antibody BC3, a monoclonal murine IgG2b that, unlike OKT3, does not activate T cells. Fourteen patients were treated with BC3 after progression of acute GVHD despite treatment with cyclosporine and corticosteroids, and three patients received BC3 as primary treatment for GVHD. BC3 was administered at a dose of 0.1 or 0.2 mg/kg/day for seven or eight days. Five patients achieved complete resolution of GVHD, eight patients had partial improvement, two patients had no change, and two patients had progression of GVHD on therapy. Responses were sustained in 8 of 13 patients. Mild chills, fever, hypertension, and chest discomfort occurred in various combinations following 6 of 17 (35%) initial infusions of BC3 and following 4 of 99 (4%) subsequent infusions. In each instance it was possible to continue BC3 therapy without adjusting the dose or treatment schedule. In each patient treated, the absolute count of peripheral blood lymphocytes decreased transiently but returned to baseline within 22 hr after the first infusion. Circulating T cells had surface CD3 molecules saturated by the infused antibody in all but one patient. Four patients survived longer than one year after treatment with antibody BC3, and 13 patients died of infection or organ failure. Administration of the nonmitogenic anti-CD3 antibody BC3 was associated with improvement in the clinical manifestations of GVHD with minimal acute toxicity. Efficacy of antibody treatment did not depend on depletion of circulating T cells. Therefore, antibody BC3 may be achieving therapeutic immunosuppression by modulating T cell function. Controlled studies in patients treated earlier in the course of GVHD should determine whether antibody BC3 can improve survival.  相似文献   
79.
To determine whether dilation of large coronary arteries normalizes shear during increased flow following brief occlusion, six dogs were instrumented to measure aortic and left ventricular pressures, left circumflex coronary artery external diameter, and coronary blood flow. The coronary artery was occluded for 15 or 30 s. Data were obtained before and after blockade of EDRF synthesis with nitro-L-arginine. Internal coronary artery diameter and wall shear were calculated on a moment-to-moment basis and the area under the flow curve was measured. Peak flow and shear rate were unaffected by NLA or by the occlusion duration. Flow curve area increased with the duration of occlusion. Internal and external diameters increased significantly for 15 s occlusions before NLA (by 4 ± 1% in external diameter and by 11 ± 4% in internal diameter) and for 30 s occlusions before NLA (by 5 ± 1% in external diameter and by 14 ± 5% in internal diameter) but not after NLA. Adenosine infusions of 0.05, 0.10, 0.50, and 1.0 μmol/kg/min were also used to dilate the coronary arteries. With each infusion, flow, shear and diameter were allowed to reach steady state. Steady state shear was reduced only slightly and did not approach the baseline state. We conclude that increased shear rate causes an increase in coronary artery diameter which is EDRF dependent. Increased coronary artery diameter during reactive hyperemia and adenosine infusions did not normalize wall shear.  相似文献   
80.
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