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   2690篇
  免费   178篇
  国内免费   33篇
耳鼻咽喉   11篇
儿科学   79篇
妇产科学   37篇
基础医学   520篇
口腔科学   24篇
临床医学   223篇
内科学   620篇
皮肤病学   38篇
神经病学   270篇
特种医学   187篇
外科学   361篇
综合类   37篇
一般理论   1篇
预防医学   133篇
眼科学   11篇
药学   168篇
中国医学   1篇
肿瘤学   180篇
  2022年   27篇
  2021年   32篇
  2020年   26篇
  2019年   34篇
  2018年   37篇
  2017年   30篇
  2016年   43篇
  2015年   48篇
  2014年   60篇
  2013年   97篇
  2012年   149篇
  2011年   122篇
  2010年   114篇
  2009年   81篇
  2008年   133篇
  2007年   105篇
  2006年   106篇
  2005年   106篇
  2004年   93篇
  2003年   95篇
  2002年   77篇
  2001年   92篇
  2000年   80篇
  1999年   69篇
  1998年   63篇
  1997年   54篇
  1996年   49篇
  1995年   42篇
  1994年   35篇
  1993年   28篇
  1992年   49篇
  1991年   45篇
  1990年   63篇
  1989年   43篇
  1988年   59篇
  1987年   57篇
  1986年   37篇
  1985年   39篇
  1984年   37篇
  1983年   35篇
  1982年   18篇
  1981年   23篇
  1980年   27篇
  1979年   28篇
  1978年   21篇
  1977年   20篇
  1976年   24篇
  1975年   19篇
  1972年   16篇
  1971年   19篇
排序方式: 共有2901条查询结果,搜索用时 15 毫秒
91.
The immune mechanisms underlying delayed induction of Th1‐type immunity in the lungs following pulmonary mycobacterial infection remain poorly understood. We have herein investigated the underlying immune mechanisms for such delayed responses and whether a selected innate immune‐modulating strategy can accelerate Th1‐type responses. We have found that, in the early stage of pulmonary infection with attenuated Mycobacterium tuberculosis (M.tb H37Ra), the levels of infection in the lung continue to increase logarithmically until days 14 and 21 postinfection in C57BL/6 mice. The activation of innate immune responses, particularly DCs, in the lung is delayed. This results in a delay in the subsequent downstream immune responses including the migration of antigen‐bearing DCs to the draining lymph node (dLN), the Th1‐cell priming in dLN, and the recruitment of Th1 cells to the lung. However, single lung mucosal exposure to the TLR agonist FimH postinfection is able to accelerate protective Th1‐type immunity via facilitating DC migration to the lung and draining lymph nodes, enhancing DC antigen presentation and Th1‐cell priming. These findings hold implications for the development of immunotherapeutic and vaccination strategies and suggest that enhancement of early innate immune activation is a viable option for improving Th1‐type immunity against pulmonary mycobacterial diseases.  相似文献   
92.
The aim of the present study was to describe subsets of cells with regulatory properties in primary Sjögren's syndrome (pSS), and to correlate these cell populations with clinical symptoms. Among the 32 investigated patients, 23 had extraglandular manifestations (EGMs), while nine had only glandular symptoms. Twenty healthy individuals served as controls. The percentages of natural killer (NK), natural killer T cells (NK T), interleukin (IL)‐10 producing T regulatory type 1 (Tr1) cells and CD4+CD25+ regulatory T cells (Treg) cells were determined by flow cytometry and serum cytokine levels of IL‐4, IL‐6, IL‐10, tumour necrosis factor (TNF)‐α and interferon (IFN)‐γ were evaluated by enzyme‐linked immunosorbent assay (ELISA). Functional tests were carried out to assess the suppressor properties of Treg cells in patients and controls. Peripheral NK, NK T and Tr1 cell percentages were elevated in pSS, while CD4+CD25+ Treg cells showed reduced frequencies in patients compared to controls. In pSS, elevated percentages of NK T, Tr1 and CD4+CD25+ Treg cells were observed in patients with EGMs, when compared to patients with sicca symptoms only. CD4+CD25+ Treg cell percentages showed a negative correlation with sialometry values. The in vitro functional assay demonstrated lower suppression activity of CD4+CD25+ Treg cells in patients compared to controls. Serum IL‐6 and TNF‐α levels were elevated, while IL‐10 was decreased in patients compared to controls. Negative correlation was found between IL‐10 levels and the percentages of Tr1 cells. Changes in the investigated subsets of regulatory cells in pSS may contribute to the development and progression of the disease.  相似文献   
93.
94.
95.
The Cleveland Clinic CorAide left ventricular assist system consists of a permanently implantable centrifugal pump in which the rotating assembly is completely suspended and noncontacting. A series of chronic animal in vivo studies were conducted to evaluate the biologic effects of CorAide circulatory support without the use of anticoagulation therapy. The CorAide pump was implanted in six calves (five calves for 21 to 32 days and one calf for 95 days). The first five calves received intravenous heparin during the early postoperative periods (2-7 days). Heparin administration was then discontinued and no other anticoagulant drugs were used for the duration of the experiments. The last calf did not receive any anticoagulant except for a bolus dose of heparin (200 U/kg) during surgery. Hemodynamics were stable in all six calves, with a mean pump flow of 5.6+/-1.2 L/min and mean arterial pressure of 100+/-4 mm Hg. The blood pump surfaces were clean of thrombus in all six calves. Significant findings at autopsy were limited to one case of renal infarction. There was no incidence of mechanical failure, bleeding, or device infection. The CorAide pump can be safely run with minimal or no anticoagulant therapy.  相似文献   
96.
97.
BACKGROUND: Mizolastine is a nonsedating H1 histamine receptor antagonist with additional antiallergic properties currently marketed in Europe for the treatment of seasonal and perennial allergic rhinitis (PAR) and urticaria. OBJECTIVE: This multicenter, randomized, double-blind, parallel-group study was conducted to evaluate the efficacy and safety of mizolastine in PAR compared with loratadine and placebo. METHODS: After a 1-week placebo run-in period, 428 adult PAR patients received placebo (146 of 428), mizolastine 10 mg (141 of 428), or loratadine 10 mg (141 of 428) once daily for 28 days. Symptoms were evaluated by patients and physicians using a total nasal score, evaluating itching, rhinorrhea, nasal blockade, and sneezing severity. RESULTS: Mizolastine treatment resulted in a significantly greater decrease in patient-rated total nasal score than placebo after 2 weeks (D14; -42%, P < 0.001) and at the end of the treatment period (-46%, P = 0.01), and significantly greater than that observed with loratadine at D14 (P = 0.031). No significant difference in change in total nasal score was observed between loratadine and placebo at 2- and 4-week visits. The global safety was satisfactory and the incidence of adverse events was similar in the three treatment groups. CONCLUSIONS: Mizolastine provides effective symptom relief in PAR together with a satisfactory safety profile. Improvement with mizolastine was significantly greater than placebo throughout the study despite a large placebo effect. Also mizolastine's effects were greater those observed with loratadine after 2 weeks of treatment.  相似文献   
98.
Defects of mitochondrial polymerase gamma (POLG) underlie neurological diseases ranging from myopathies to parkinsonism and infantile Alpers syndrome. The most severe manifestations have been associated with mutations of the 'spacer' region of POLG, the function of which has remained unstudied in humans. We identified a family, segregating three POLG amino acid variants, A467T, R627Q and Q1236H. The first two affect the spacer region and the third is a polymorphism, allelic with R627Q. Three grades of disease severity appeared to correlate with the genotypes. The patient with the most severe outcome, cerebellar ataxia syndrome, had all three variants, those with R627Q and Q1236H had juvenile-onset ptosis and gait disturbance and those with a single A467T allele had late-onset ptosis. To evaluate the molecular pathogenesis of these spacer defects, we expressed and purified the mutant proteins and studied their catalytic properties in vitro. The A467T substitution resulted in clearly decreased activity, DNA binding and processivity of the polymerase. Our biochemical data, the dominant manifestation of A467T and its previously reported high frequency in the Belgian population (0.6%), emphasize the role of this mutation as a common cause of neurological disease. Further, biochemical evidence that a polymorphic variant may modify the function of a mutant POLG, if occurring in the same polypeptide, is shown here. Finally, and surprisingly, other pathogenic spacer mutants showed DNA-binding affinities and processivities similar to or higher than the controls, suggesting that the disease-causing mechanisms of spacer mutations extend beyond the basic catalytic functions of POLG.  相似文献   
99.
100.
Multiple hormones controlling energy homeostasis regulate the expression of neuropeptide Y (NPY) and agouti-related peptide (AgRP) in the arcuate nucleus of the hypothalamus. Nevertheless, inactivation of the genes encoding NPY and/or AgRP has no impact on food intake in mice. Here we demonstrate that induced selective ablation of AgRP-expressing neurons in adult mice results in acute reduction of feeding, demonstrating direct evidence for a critical role of these neurons in the regulation of energy homeostasis.  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