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   5165篇
  免费   401篇
  国内免费   27篇
耳鼻咽喉   19篇
儿科学   232篇
妇产科学   200篇
基础医学   707篇
口腔科学   111篇
临床医学   454篇
内科学   1160篇
皮肤病学   87篇
神经病学   393篇
特种医学   550篇
外科学   664篇
综合类   54篇
一般理论   2篇
预防医学   353篇
眼科学   64篇
药学   220篇
中国医学   7篇
肿瘤学   316篇
  2022年   51篇
  2021年   111篇
  2020年   69篇
  2019年   88篇
  2018年   115篇
  2017年   87篇
  2016年   105篇
  2015年   123篇
  2014年   146篇
  2013年   208篇
  2012年   272篇
  2011年   204篇
  2010年   206篇
  2009年   142篇
  2008年   180篇
  2007年   181篇
  2006年   172篇
  2005年   151篇
  2004年   142篇
  2003年   157篇
  2002年   140篇
  2001年   126篇
  2000年   134篇
  1999年   129篇
  1998年   169篇
  1997年   151篇
  1996年   154篇
  1995年   111篇
  1994年   100篇
  1993年   111篇
  1992年   93篇
  1991年   94篇
  1990年   79篇
  1989年   121篇
  1988年   87篇
  1987年   104篇
  1986年   94篇
  1985年   87篇
  1984年   47篇
  1983年   49篇
  1982年   46篇
  1981年   29篇
  1980年   47篇
  1979年   37篇
  1978年   40篇
  1977年   35篇
  1976年   32篇
  1975年   40篇
  1971年   26篇
  1969年   26篇
排序方式: 共有5593条查询结果,搜索用时 15 毫秒
91.
92.
A method to measure the "in vitro" RNA release from rat brain cell nuclei was described. Nuclear RNA was prelabelled "in vivo" for 30 or 120 min. In the first case the released RNA was heterogeneous and its electrophoretic mobility was similar to that of cytoplasmic messenger RNAs; nuclei prelabelled for 120 min mostly released the two major species of ribosomal RNAs. The release of mRNAs from the nuclei increased during cerebral development while that of the ribosomal RNAs did not. The increased capacity of the nuclei to release "radidly labelled" RNA with age neither determined an increase of the polysomal population, nor seemed to be dependent on cytoplasmic macromolecules.  相似文献   
93.
The vasa vasorum and angioplasty   总被引:2,自引:0,他引:2  
Interruption of flow in the vasa vasorum may lead to medial necrosis and aneurysm formation. The purpose of this study was to determine whether angioplasty produces significant alterations in the morphology or blood flow of the vasa vasorum of the dilated artery. The morphology of the canine vasa vasorum was studied before and after angioplasty; in a separate experiment vessel wall blood flow (VWBF) in canine carotid arteries was measured after angioplasty to determine whether physiologic regulation of the blood flow was disrupted by arterial dilation. No morphologic changes could be demonstrated in the vasa vasorum of the dilated artery; however, VWBF was increased by 1194 +/- 215% (mean +/- standard error, p less than 0.01) between 90 and 120 minutes after angioplasty. VWBF in the adjacent nondilated arterial segment was also increased (720 +/- 177% between 10-30 minutes, p less than 0.01) but returned toward normal after 60 minutes. Adenosine caused a "paradoxical" decrease in VWBF (p less than 0.05) of the dilated arterial segment while causing increased VWBF (p less than 0.05) in the thoracic aorta. Angioplasty appears to produce persistent hyperemia in the dilated arterial wall. A paradoxical response to adenosine suggests that vasa vasorum in the dilated arterial segment are maximally vasodilated. This may be due to mechanical disruption of vasomotor tone or to release of vasoactive substances.  相似文献   
94.
O M Ramirez 《Annals of plastic surgery》1992,28(3):218-32; discussion 233-4
The subperiosteal frontal rhytidectomy described by Tessier was the departure point for a new approach for facial rejuvenation. Psillakis described the subperiosteal face-lift "as an improved concept for correction of the aging face." However, this technique has a high incidence of frontal nerve injury and because of the limitations in the subperiosteal dissection, the facial soft tissues cannot be lifted reliably to the desired position. Other authors have repeated the Psillakis experience with the same frustrations and complication rate. In this report, I describe the evolution of the subperiosteal face-lift and the significant modifications that I have introduced, making this procedure safer and improving results in the degree of facial rejuvenation. My approach of subperiosteal rhytidectomy has been used in 34 patients with a minimal complication rate. This technique also addresses the rejuvenation of the central portion of the face and the restoration of tension of the facial mimetic musculature not obtained by current brow/face-lift procedures.  相似文献   
95.
Summary A new treatment for Burkitt's lymphoma (BL) has been devised with coordinated intrathecal (IT) methotrexate (MTX) + high-dose intravenous (IV) MTX with citrovorum factor (CF) rescue and high-dose Cytoxan (CYT). Six patients have been entered on the study. Five patients continue in complete remission at 13+–31+ months (median, 29+ months). One died of septicemia during myelosuppression. Only minor toxicity was seen in four patients. Two patients had severe metabolic disturbances following initial CYT therapy; one of these patients also had reversible, moderately severe hepatorenal MTX toxicity. No neurotoxicity was observed. Results of therapy are impressive in this limited patient group, four of whom were poor-prognosis (Stage C or D) and two of whom were good-prognosis patients (Stage B or AR). The potential for severe toxicity is great; adherence to the criteria for drug administration and close surveillance of the patient in the post-treatment period are mandatory.Plasma and cerebrospinal fluid (CSF) MTX pharmacokinetics were studied in three patients. CSF MTS levels exceeded 10-6 M with coordinated IT-IV MTX (150 mg/kg body wt.) With MTX infusions at the 200 mg/kg level, therapeutic concentrations were maintained in the CSF for approximately 60 h. Plasma MTX concentrations exceeded 10-6 M at all infusion dose levels, the duration of the therapeutic concentration increasing with the dose level. Priming IT MTX followed in 24 h by IV MTX, 200 mg/kg assured therapeutic concentrations in plasma and CSF of sufficient duration to cover two generation times of the BL cell.  相似文献   
96.
OBJECTIVE: This study determined the extent to which adding structured procedures improved diagnostic accuracy for outpatients with severe mental illness in a community mental health setting. METHOD: The Structured Clinical Interview for DSM-III-R (SCID) was used to interview 200 psychiatric outpatients. A research nurse reviewed medical records and amended the SCID diagnoses accordingly. A research psychiatrist or psychologist reviewed the diagnostic data and interviewed each patient to verify or further modify the previous findings. Diagnostic outcomes at each step of the procedure were compared to determine whether adding additional data improved diagnostic accuracy. The additional time required for each element of the diagnostic procedure was also assessed. RESULTS: Kappa comparisons of the different diagnostic levels showed that adding additional data significantly improved accuracy. Diagnoses rendered by combining the SCID and review of the medical record were the most accurate, followed by the SCID alone, and then diagnoses made by psychiatrists during routine care. In addition, the SCID alone identified five times as many current and past secondary diagnoses as were documented routinely in patients' charts. CONCLUSIONS: Combining structured interviewing with a review of the medical record appears to produce more accurate primary diagnoses and to identify more secondary diagnoses than routine clinical methods. The patients' knowledge of their diagnoses was limited, suggesting a need for patient education in this setting. Whether use of structured interviewing in routine practice improves patient outcomes deserves further study.  相似文献   
97.
Although recruitment of ethnic and racial minorities in medical research has been evaluated in several studies, much less is known about the methods used to recruit these populations to participate in cancer genetics research. This report reviews the resources that have been used to identify and recruit ethnic and racial minorities to participate in hereditary breast cancer research. Overall, hospital-based resources were used most often to identify potential subjects, and active recruitment methods were used most frequently to enroll eligible subjects. This review suggests that there appears to be a finite number of resources and strategies to identify and recruit potential subjects to participate in cancer genetics research; however, options for improving awareness about cancer genetics research among ethnic and racial minorities have not been extensively evaluated. To study ethnic and racial minority participation in cancer genetics research, stronger evaluation components will need to be integrated into research methods. Both observational and experimental studies are needed to determine resources that are most effective for identifying potential subjects who are ethnic and racial minorities and to evaluate the effects of different recruitment strategies on enrollment decisions among these populations.  相似文献   
98.
99.
The influence of reported paternal attitudes on the decision to breast-feed   总被引:1,自引:0,他引:1  
Objective: To identify factors that influence a woman's decision to breast-feed.
Methodology: Five hundred and fifty-six women were recruited from the maternity wards of two Perth hospitals. Data were collected from a self-administered questionnaire completed by participants prior to discharge. Logistic regression analysis was used to determine factors influencing the initiation of breast-feeding.
Results: At discharge from hospital 83.8% of women were breast-feeding, including 6% who were giving complementary formula feeds. After controlling for potentially confounding demographic and biomedical factors, the father's reported preference for breast-feeding was found to be the most important factor influencing a woman's decision to breast-feed (OR 10.18).
Conclusion: Fathers participate in and influence the choice of infant feeding method and should be included in breast-feeding discussions.  相似文献   
100.
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