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   1259篇
  免费   68篇
  国内免费   9篇
耳鼻咽喉   8篇
儿科学   46篇
妇产科学   25篇
基础医学   144篇
口腔科学   44篇
临床医学   100篇
内科学   375篇
皮肤病学   50篇
神经病学   48篇
特种医学   155篇
外国民族医学   1篇
外科学   96篇
综合类   43篇
预防医学   84篇
眼科学   5篇
药学   66篇
中国医学   2篇
肿瘤学   44篇
  2021年   8篇
  2019年   12篇
  2018年   12篇
  2017年   14篇
  2016年   16篇
  2015年   29篇
  2014年   19篇
  2013年   41篇
  2012年   30篇
  2011年   38篇
  2010年   37篇
  2009年   54篇
  2008年   44篇
  2007年   28篇
  2006年   31篇
  2005年   41篇
  2004年   55篇
  2003年   37篇
  2002年   27篇
  2001年   31篇
  2000年   24篇
  1999年   34篇
  1998年   61篇
  1997年   66篇
  1996年   60篇
  1995年   48篇
  1994年   43篇
  1993年   40篇
  1992年   13篇
  1991年   20篇
  1990年   24篇
  1989年   30篇
  1988年   30篇
  1987年   32篇
  1986年   27篇
  1985年   15篇
  1984年   8篇
  1983年   14篇
  1982年   18篇
  1981年   9篇
  1980年   10篇
  1979年   8篇
  1978年   6篇
  1977年   15篇
  1976年   10篇
  1973年   5篇
  1972年   5篇
  1971年   5篇
  1969年   8篇
  1968年   8篇
排序方式: 共有1336条查询结果,搜索用时 15 毫秒
31.
Fifty women with polycystic ovaries took part in a prospective randomized study. All women required treatment by in-vitro fertilization (IVF) for reasons other than anovulation. They had all previously undergone ovarian stimulation with gonadotrophin therapy which had failed to result in pregnancy or had been abandoned due to high risk of developing ovarian hyperstimulation syndrome (OHSS). Twenty-five women were treated by long-term pituitary desensitization followed by gonadotrophin therapy, oocyte retrieval and embryo transfer (group 1). Twenty-five women underwent laparoscopic ovarian electrocautery after pituitary desensitization followed by gonadotrophin therapy, oocyte retrieval and embryo transfer (group 2). A significantly higher number of women in group 1 had to have the treatment cycle abandoned due to impending or actual OHSS, determined by endocrine and clinical findings. In addition, the development of moderate or severe OHSS in completed cycles was higher in group 1. The pregnancy rate and miscarriage rates in the two treatment groups were similar. The authors propose that laparoscopic ovarian electrocautery is a potentially useful treatment for women who have previously had an IVF treatment cycle cancelled due to risk of OHSS or who have suffered OHSS in a previous treatment cycle.   相似文献   
32.
The bias favoring deletion over inversion in DH-JH rearrangement has been known for years, but the underlying mechanism has yet to be fully defined. It has been suggested that the ratio of deletion/inversion is determined by the combined effect of two factors: (i) the relative strengths of 5' and 3' recombination signal sequences (RSS) of a DH segment, and (ii) the efficiency with which the deletional product (one joint) forms relative to the inversional product (two joints). In this study, we analyzed for the first time the effect of factor 1 alone on the biased 3' RSS utilization in DH-JH joining by using deletional plasmids in an extrachromosomal substrate V(D)J recombination assay. It was found that the 3' RSS and associated coding end (12 bp) mediate recombination more efficiently than the 5' RSS/coding end DH-JH plasmids. These results demonstrate that the effect of the RSS/coding end alone can account, at least partially, for the predominant deletion in DH-JH recombination. The potential effect of the relative strength of RSS and associated coding end on the ordered rearrangement of DH-JH followed by VH to DH-JH was also assessed. When recombination frequencies of D-->J (3' DH to J3) were compared with frequencies of V-- >D (VHPJ14 to 3' DH or VHOX2 to 3' DH), it was found that V-->D joining was, if anything, more efficient than D-->J joining. Therefore, if all three segments were accessible, RSS/coding end effects would not contribute to the ordered rearrangement of the IgH locus.   相似文献   
33.
A unifying feature of the CAG expansion diseases is the formation of intracellular aggregates composed of the mutant polyglutamine-expanded protein. Despite the presence of aggregates in affected patients, the precise relationship between aggregates and disease pathogenesis is unresolved. Results from in vivo and in vitro studies of mutant huntingtin have lead to the hypothesis that nuclear localization of aggregates is critical for the pathology of Huntington's disease (HD). We tested this hypothesis using a 293T cell culture model system that compared the frequency and toxicity of cytoplasmic and nuclear huntingtin aggregates. We first assessed the mode of nuclear transport of N-terminal fragments of huntingtin, and show that the predicted endogenous NLS is not functional, providing data in support of passive nuclear transport. This result suggests that proteolysis is a necessary step for nuclear entry of huntingtin. Additionally, insertion of nuclear import or export sequences into huntingtin fragments containing 548 or 151 amino acids was used to reverse the normal localization of these proteins. Changing the subcellular localization of the fragments did not influence their total aggregate frequency. There were also no significant differences in toxicity associated with the presence of nuclear compared with cytoplasmic aggregates. The findings of nuclear and cytoplasmic aggregates in affected brains, together with these in vitro data, support the nucleus and cytosol as subcellular sites for pathogenesis in HD.   相似文献   
34.
35.
Central thrombi in pulmonary arterial hypertension detected by MR imaging   总被引:1,自引:0,他引:1  
Fisher  MR; Higgins  CB 《Radiology》1986,158(1):223-226
Differentiation of thrombi from slow flow in the pulmonary arteries, sometimes observed in the presence of pulmonary arterial hypertension, can be equivocal. Magnetic resonance (MR) imaging was performed in a patient with chronic pulmonary thromboembolism and pulmonary arterial hypertension using an electrocardiographically gated technique that allowed visualization of the pulmonary arteries at the end of diastole and multiple times during systole. These images were compared with those of a patient with primary pulmonary hypertension and those of healthy subjects. Thrombi were discrete structures, seen throughout the cardiac cycle on both the first and second spin-echo images, and decreased in signal intensity on the second image. Slow flow increased in signal intensity and changed in structure during the cardiac cycle and was seen best on the second image. MR may play an important role in excluding large central thrombi as the cause of pulmonary arterial hypertension. It is a noninvasive method for defining pulmonary arterial wall thickness and for direct visualization of chronic pulmonary thrombus.  相似文献   
36.
Pulmonary manifestations of AIDS: review of 106 episodes   总被引:9,自引:0,他引:9  
Suster  B; Akerman  M; Orenstein  M; Wax  MR 《Radiology》1986,161(1):87-93
We reviewed the clinical records and chest radiographs of all patients admitted to our institution between 1982 and 1984 who had pulmonary disease and who were later proved to have acquired immunodeficiency syndrome (AIDS) (95 patients). Diffuse parenchymal lung disease was the most common finding. These infiltrates were usually interstitial and caused by Pneumocystis carinii pneumonia or P. carinii combined with cytomegalovirus infection. Focal, multilobar, interstitial infiltrates were also often seen and usually caused by P. carinii or P. carinii and cytomegalovirus infections. Rarely, well-defined, multiple, interstitial nodules less than 10 mm in diameter were the only or predominant characteristic and were seen only in association with Mycobacterium tuberculosis or Cryptococcus neoformans infections or Kaposi sarcoma. Hilar or mediastinal adenopathy occurred in 17 of the 21 patients with M. tuberculosis or C. neoformans infections. In contrast, only 4% of patients with P. carinii infections presented with these findings. We also found that hilar or mediastinal adenopathy was not significantly associated with peripheral adenopathy. Lung cavitation, pleural effusion, or a normal chest radiograph was uncommon.  相似文献   
37.
Checketts  MR; Wildsmith  JAW 《CEACCP》2004,4(2):48-51
The last few years have seen increasing concerns among anaesthetistsabout the risks of pharmacological prophylaxis for thromboembolicdisease. Increased bleeding during or after surgery is one concern,but of greater significance is the possibility of an increasedpredisposition to haematoma formation when regional block isused. Most of the recent consideration of this problem has beenin relation to vertebral canal haematoma formation after centralnerve block. Some thought must be given also to the possibilityof haematoma formation after peripheral techniques when thetarget nerve is deeply placed so that pressure cannot be usedto control bleeding after needle insertion. However, this reviewwill be focused on vertebral canal haematoma.  相似文献   
38.
It is highly recommended to conduct a prophylactic check for any dental problems on patients who suffer from leukaemia before chemotherapy begins. Bacteraemia caused by oral microflora may be very dangerous for patients with haematological malignancies. However, it should be noted that the prophylactic process itself might bring about life-threatening complications if there is only a short interval between dental treatment and the beginning of chemotherapy, or if the dental treatment is too aggressive. We present a case where this prophylactic procedure produced life-threatening complications for a patient with acute myeloid leukaemia.  相似文献   
39.
Background Subcutaneous zygomycosis is an uncommon condition observed in tropics. Few series have been published, particularly from the northern regions of India. Objectives The aim of this study was to describe clinical, investigative and therapeutic details in subcutaneous zygomycosis observed in two teaching hospitals in Delhi. Patients and methods Ten patients seen over a period of 10 years (1999–2009) form the material for this report. Results There were four children and six adults. In four children, the presentation was a subcutaneous localized mass or gradually spreading plaque. In the others, it was observed over nasal region of face, spreading inward into mucosal sites and paranasal sinuses, and outward to the contiguous areas. Regional lymphadenopathy was present in two with facial lesions. Majority showed a granulomatous infiltrate with admixture of other cells, mainly eosinophils. Aseptate or poorly septate hyphae were observed in seven. In one patient in whom no hyphae were observed, there was dense perivascular inflammation. Organisms were cultured from four patients, Basidiobolus ranarum in two and Syncephalastrum racemosum in two. The main therapy used was a saturated solution of potassium iodide (KI). Four received only KI of which two attained cure after 3 months and 9 months respectively, and the other two showed signs of regression. In one boy subsidence was associated with reduced circumference of thigh. Ketoconazole or itraconazole was given with KI to hasten regression when response was slow or there were side‐effects to KI. Conclusion Awareness and early recognition will prevent disfigurement produced by advanced disease, misdiagnosis and unnecessary surgical intervention.  相似文献   
40.
目的探讨敏感性编码技术(SENSE)前瞻性门控螺旋相位对比MR检查序列在儿童与成人先天性心脏病检查的可行性。材料与方法当地伦理委员会批准该项研究,所有  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