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   6358篇
  免费   492篇
  国内免费   23篇
耳鼻咽喉   76篇
儿科学   165篇
妇产科学   149篇
基础医学   993篇
口腔科学   101篇
临床医学   629篇
内科学   1411篇
皮肤病学   150篇
神经病学   373篇
特种医学   334篇
外国民族医学   1篇
外科学   1165篇
综合类   68篇
一般理论   3篇
预防医学   250篇
眼科学   156篇
药学   402篇
中国医学   15篇
肿瘤学   432篇
  2021年   80篇
  2020年   58篇
  2019年   69篇
  2018年   97篇
  2017年   89篇
  2016年   113篇
  2015年   154篇
  2014年   176篇
  2013年   211篇
  2012年   310篇
  2011年   331篇
  2010年   179篇
  2009年   194篇
  2008年   310篇
  2007年   331篇
  2006年   307篇
  2005年   307篇
  2004年   256篇
  2003年   263篇
  2002年   231篇
  2001年   189篇
  2000年   221篇
  1999年   204篇
  1998年   87篇
  1997年   90篇
  1996年   73篇
  1995年   67篇
  1994年   56篇
  1993年   55篇
  1992年   110篇
  1991年   112篇
  1990年   107篇
  1989年   123篇
  1988年   72篇
  1987年   70篇
  1986年   77篇
  1985年   67篇
  1984年   58篇
  1983年   43篇
  1982年   43篇
  1981年   36篇
  1980年   34篇
  1979年   77篇
  1978年   42篇
  1976年   36篇
  1975年   34篇
  1974年   52篇
  1973年   40篇
  1972年   47篇
  1971年   49篇
排序方式: 共有6873条查询结果,搜索用时 31 毫秒
1.
2.
3.
4.
Objective: Electroporation mediated transfer of plasmid DNA into peripheral muscle results in high transfection efficiency. The aim of this study was to investigate the effect of gene transfer of human IL-10 (hIL-10) into the tibialis anterior muscle (MTA) in combination with low dose Cyclosporine A (CsA) on acute rejection of lung allografts in the rat. Methods: Lung allotransplantation was performed from male BN donor to male Fisher F344 rats. Gene transfer was achieved by intramuscular injection into the MTA of the recipient followed by electroporation (4×20 ms impulses at 200 V/cm) 24 h prior to the transplantation. Group A (n=5) received CsA (2.5 mg/kg bw ip) for 5 days post-transplant and group B (n=5) 2.5 μg of PCIK hIL-10 (plasmid expression vector containing human CMV immediate early gene promoter and enhancer) and a low dose CsA (2.5 mg/kg bw i.p.). Graft function was assessed by blood gas at day 5 after exclusion of the native lung. Animals were sacrificed and blood was drawn to measure serum hIL-10 levels (ELISA) and tissue was sampled for histological grading of rejection. Results: Local expression of hIL-10 was confirmed at the mRNA level by in situ hybridization. All group A control animals showed severe signs of rejection. At day 5 all grafts in group B showed good gas exchange mean PaO2 233±123 mmHg, vs 44±8 mmHg in group A. Histological examination revealed moderate to severe rejection in all animals in group A (IIIB, ISHLT) in contrast to low moderate rejection in group B (II–IIIA). hIL-10 serum levels on day 5 were 14±7 pg/ml in group B vs. 0 in group A. Conclusions: Electroporation mediated hIL-10 overexpression in a peripheral muscle of the recipient in combination with low dose CsA reduces acute rejection in this model of rat lung allotransplantation.  相似文献   
5.
6.
The effect of ciclosporin (CS) and methotrexate (MTX) on the development of graft-versus-host (GvH) disease was examined after small bowel allotransplantation in the rat. The drugs were tested either alone or in combination. Lewis small bowel allografts were transplantated into Brown Norway recipients in a heterotopic position. The native small bowel, spleen, liver, skin, mesenteric lymph nodes and the kidney of the recipients were examined histologically 5, 10 and 20 days after allotransplantation. Intraepithelial lymphocyte numbers were determined quantitatively in the native small bowel. The relative spleen weight of the host was determined after sacrifice for estimation of the severity of GvH disease. Grade I GvH reaction of the native small bowel occurred in the animals without immunosuppression, but graft rejection predominated in this group. Treatment with CS was effective in the early postoperative periods; after 10 and 20 days GvH lesions in the native small bowel were comparable to those observed in the allogeneic combinations. MTX had a detrimental effect on the allografts and the GvH reaction was augmented. When CS and MTX were combined, GvH lesions were comparable to those in the animals treated solely with CS. Animals, however, suffered from heavy side effects. The spleen, liver, lymph nodes and kidney exhibited only unspecific histologic changes, which could not unequivocally be recognized as a GvH reaction. This was true for all groups. As a conclusion it can be said that GvH reaction occurs in the early postoperative period in a fully allogeneic model and cannot be prevented by CS in the dosae used. MTX was not seen to be of any value in this regard.  相似文献   
7.
8.
A H Schmid 《Psychiatry》1991,54(4):358-367
Many of the terms used to describe conditions in elderly individuals, whether medical (deterioration, involution, degeneration) or neurobehavioral (impairment, dysfunction), imply deficiency. The complex of distorted views of real impairment, illness, or disability may be described as the deficiency model. Although developmental theory has expanded explosively and could offer an alternative frame of reference to dispel denigration of the elderly condition, late life continues to be viewed as lacking all redeeming aspects, while mortality is considered an obstacle to prolonging life rather than one of its determinants. Deficiency-model thinking has influenced the conduct of epidemiologic, neurobiologic and clinical research, whose results in turn have often been interpreted to reinforce such thinking. It can also distort clinical approaches to diagnosis and treatment of late-life disorders. This paper offers instead an alternative approach that focuses on late life as a developmental task.  相似文献   
9.
OBJECTIVE: The primary objectives of this study were to compare the effect of spinal manipulation vs. sham manipulation on a) circulating plasma levels of the prostaglandin F2a metabolite, 15-keto-13,14-dihydroprostaglandin (KDPGF2a), b) perceived abdominal and back pain and c) perceived menstrual distress in women with primary dysmenorrhea. DESIGN: This randomized clinical pilot study investigated the outcome measures before and after either a spinal manipulation treatment (SMT) or a sham manipulation. SETTING: All subjects were treated at the National College Chiropractic clinic, a private chiropractic clinic in the suburban Chicago area. PARTICIPANTS: Forty-five women with a history of primary dysmenorrhea were recruited from the local community. The volunteers ranged in age from 20-49 (mean age = 30.3 yr), and were entered into the study between April 1990 and January 1991. Twenty-four were randomly assigned to the spinal manipulation group and 21 were assigned to the sham group. INTERVENTIONS: Subjects treated with spinal manipulation were placed in a side-lying position with the bottom leg straight and the top leg flexed at the knee and hip. They received a high-velocity, short lever, low-amplitude thrust to all clinically relevant vertebral levels within T10 and L5-S1 and the sacroiliac joints. In the sham manipulation, subjects were placed in a side-lying position with both hips and knees flexed. Their manipulation consisted of a similar thrust administered to the midline base of the sacrum. OUTCOME MEASURES: Perceived abdominal and back pain were measured with a visual analog scale, and menstrual distress was measured with the Menstrual Distress Questionnaire. Both were administered 15 min before and 60 min after treatment. Blood samples were collected by venipuncture for the determination of plasma levels of KDPGF2a at the same times. The plasma was then assayed for KDPGF2a by radioimmunoassay. RESULTS: Analysis of covariance and paired Student's t tests were used for the statistical evaluation. Immediately after treatment, the perception of pain and the level of menstrual distress were significantly reduced by SMT. This reduction was associated with a significant reduction in plasma levels of KDGPF2a in the SMT group. A significant and similar reduction in plasma KDPGF2a also occurred in the sham group, indicating that a placebo effect was associated with a single sham intervention. CONCLUSIONS: This randomized pilot study suggests that SMT may be an effective and safe nonpharmacological alternative for relieving the pain and distress of primary dysmenorrhea. However, the large change in KDPGF2a observed in both treatment groups clearly indicates that further studies with more subjects, studied over a longer time frame, are needed to resolve the question of a placebo effect.  相似文献   
10.
Positron emission tomography (PET) using [(11)C]PK 11195, a ligand for peripheral benzodiazepine receptor binding sites, offers the opportunity to image activated microglia in vivo. This tool may therefore be used to display the occurrence of microglial activation in the course of neurodegeneration. A patient with the clinical diagnosis of corticobasal degeneration (CBD) and left-sided symptoms was studied using fluorodeoxyglucose (FDG) and [(11)C]PK 11195 PET. We found a marked right hemispheric hypometabolism and asymmetric microglial activation in corresponding areas of the basal ganglia and right temporal and parietal cortex. [(11)C]PK 11195 PET suggests involvement of microglial activation in the pathogenesis of CBD.  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