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   5191篇
  免费   326篇
  国内免费   8篇
耳鼻咽喉   55篇
儿科学   158篇
妇产科学   138篇
基础医学   706篇
口腔科学   127篇
临床医学   470篇
内科学   873篇
皮肤病学   277篇
神经病学   526篇
特种医学   269篇
外国民族医学   3篇
外科学   836篇
综合类   38篇
一般理论   4篇
预防医学   322篇
眼科学   126篇
药学   320篇
中国医学   3篇
肿瘤学   274篇
  2021年   72篇
  2020年   40篇
  2019年   44篇
  2018年   75篇
  2017年   84篇
  2016年   99篇
  2015年   125篇
  2014年   124篇
  2013年   161篇
  2012年   242篇
  2011年   275篇
  2010年   143篇
  2009年   147篇
  2008年   228篇
  2007年   255篇
  2006年   211篇
  2005年   252篇
  2004年   182篇
  2003年   192篇
  2002年   195篇
  2001年   182篇
  2000年   155篇
  1999年   138篇
  1998年   62篇
  1997年   55篇
  1996年   43篇
  1995年   50篇
  1994年   44篇
  1993年   28篇
  1992年   64篇
  1991年   74篇
  1990年   83篇
  1989年   81篇
  1988年   75篇
  1987年   82篇
  1986年   83篇
  1985年   73篇
  1984年   62篇
  1983年   48篇
  1980年   27篇
  1979年   45篇
  1977年   32篇
  1975年   32篇
  1974年   30篇
  1973年   25篇
  1972年   40篇
  1971年   30篇
  1970年   32篇
  1969年   25篇
  1968年   29篇
排序方式: 共有5525条查询结果,搜索用时 30 毫秒
1.
2.
Antioxidant preservatives prolong the quality of food and ensure the nutritional adequacy, palatability and safety of many processed foods and beverages. Effects of sodium sulfite (E221) and sorbic acid (E200) were investigated in human peripheral blood mononuclear cells (PBMC) which were purified from blood of healthy donors. Cells were stimulated with the mitogen phytohaemagglutinin in vitro, which induces proliferation of T-cells and the production of Th1-type cytokines like interferon-γ. The latter triggers enzyme indoleamine (2,3)-dioxygenase, which degrades tryptophan, and GTP cyclohydrolase I, which leads to increased neopterin production, in monocyte-derived macrophages. Sodium sulfite and sorbic acid suppressed both these biochemical changes in a dose-dependent way (P < 0.01 at 1 mM sodium sulfite and 50 mM sorbic acid). Data demonstrate a suppressive influence of sodium sulfite and sorbic acid on the activated Th1-type immune response.  相似文献   
3.
4.
J Winkler  M Neuman-Levin  G Boner 《JAMA》1991,265(5):631-632
A 37-year-old woman patient, known to have poorly controlled arterial hypertension that was diagnosed following a cerebrovascular accident at the age of 15 years, was referred to our outpatient clinic for investigation in 1987. An intrarenal arteriovenous fistula was diagnosed by selective renal angiography. Embolization of the fistula was performed using four 15-mm/5-cm coils, which induced thrombosis and obstructed the fistula. The vascularization of the affected kidney improved immediately. During the following 4 months, the antihypertensive treatment was stopped gradually, and the patient remained normotensive. This is an unusual case of a large intrarenal arteriovenous fistula, whose etiology was not clear, that was successfully treated by percutaneous embolization.  相似文献   
5.
PURPOSE: To compare commercial treatment-planning systems (TPS) for inverse planning (IP) and to assess constraint variations for specific IMRT indications. MATERIAL AND METHODS: For IP, OTP, XiO and BrainSCAN were used and step-and-shoot intensity-modulated radiotherapy (IMRT) delivery was assumed. Based on identical constraints, IP was performed for a prostate, head and neck, brain, and gynecologic case. IMRT plans were compared in terms of conformity/homogeneity, dose-volume histograms (DVHs), and delivery efficiency. For ten patients each of a class of indications, constraint variations were evaluated. RESULTS: IMRT plans were comparable concerning minimum target dose, homogeneity, conformity, and maximum doses to organs at risk. Larger differences were seen in dose gradients outside the target, monitor units, and segment number. Using help structures proved efficient to shape isodoses and to reduce segmentation workload. For IMRT class solutions, IP constraint variations depended on anatomic site. CONCLUSION: IP systems requiring doses as input and having objective functions based on physical parameters had a very similar performance. Constraint templates can be established for a class of IMRT indications.  相似文献   
6.
The value of a long-term treatment with clonazepam in the prophylaxis of affective disorder is discussed controversially in the scientific literature. Altogether there are only a few reports on the use of this compound as a mood stabilizer, most of them describing patients suffering from bipolar affective disorder. The aim of this investigation was to evaluate clonazepam as a phase prophylactic medication in affective disorder. We conducted a retrospective chart review in 34 out-patients of our lithium clinic (15 suffering from unipolar depression, 15 from bipolar disorder, four from schizoaffective disorder), who had been treated with clonazepam as a long-term medication. Clonazepam was either given as monotherapy, or as in the case of lithium non-responders, as adjunctive therapy. Patients with unipolar depression had significantly (P=0.026) less depressive episodes after initiation of treatment with clonazepam. Patients with bipolar disorder did not benefit from this therapy. Neither manic/hypomanic phases nor depressive episodes were reduced in this group of patients. Interestingly, clonazepam also reduced affective phases in our four schizoaffective patients on a trend level. Our results indicate that patients with unipolar depression may benefit from a maintenance treatment with clonazepam. Due to methodological limitations our results need to be replicated in controlled double-blind randomized clinical trials.  相似文献   
7.
Little is known about the effects of immunosuppression on patients with hereditary nonpolyposis colorectal cancer (HNPCC). We describe a kidney transplant recipient with unrecognized Muir-Torre syndrome in whom the administration of a tacrolimus-based regimen led to the eruption of multiple sebaceous tumors. The patient was later found to harbor an MSH2 mutation. Switching to a sirolimus-based regimen resulted in arrest of the disease. When the patient was switched back to tacrolimus, new facial lesions rapidly appeared. Switching again to sirolimus resulted again in halting the appearance of new lesions. This finding is in line with the known antiangiogenic activity of sirolimus and reports on the regression of cutaneous Kaposi's sarcoma in kidney transplant recipients switched from another immunosuppressive regimen to sirolimus. Further studies on the potential use of sirolimus for the treatment of de novo tumors in immunosuppressed kidney transplant recipients with HNPCC are warranted.  相似文献   
8.
9.
The temporal courses of dipeptidyl peptidase IV gamma-glutamyltransferase and alanine aminopeptidase were followed over 70 days in the morning urine of 15 healthy persons. Subsequent to basic statistical analysis a two-step procedure was performed, including spectral analysis and the fit of a cosine function by non-linear regression. The excretion of the 3 enzymes followed an infradian biorhythm with a mean period length of 10.04 for dipeptidyl peptidase IV, 13.34 for gamma-glutamyltransferase and 10.17 for alanine aminopeptidase. In addition to the basic rhythmic process described by the fitted cosine functions, in most of the enzyme patterns steap peaks of very high excretory activity appeared which was verified in repeated measurements. These infradian biorhythms with changes in the range of 100% and more, as well as their interindividual variations, have to be considered in assessing the excretion of enzymes.  相似文献   
10.
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