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   10878篇
  免费   675篇
  国内免费   20篇
耳鼻咽喉   129篇
儿科学   419篇
妇产科学   383篇
基础医学   1474篇
口腔科学   203篇
临床医学   914篇
内科学   2604篇
皮肤病学   214篇
神经病学   867篇
特种医学   455篇
外科学   1608篇
综合类   53篇
一般理论   2篇
预防医学   729篇
眼科学   186篇
药学   663篇
中国医学   40篇
肿瘤学   630篇
  2023年   33篇
  2022年   86篇
  2021年   162篇
  2020年   117篇
  2019年   193篇
  2018年   205篇
  2017年   145篇
  2016年   146篇
  2015年   207篇
  2014年   288篇
  2013年   381篇
  2012年   502篇
  2011年   562篇
  2010年   315篇
  2009年   292篇
  2008年   555篇
  2007年   604篇
  2006年   580篇
  2005年   584篇
  2004年   553篇
  2003年   511篇
  2002年   514篇
  2001年   419篇
  2000年   453篇
  1999年   367篇
  1998年   140篇
  1997年   127篇
  1996年   128篇
  1995年   109篇
  1994年   94篇
  1993年   103篇
  1992年   227篇
  1991年   211篇
  1990年   174篇
  1989年   147篇
  1988年   154篇
  1987年   145篇
  1986年   120篇
  1985年   107篇
  1984年   71篇
  1983年   60篇
  1982年   45篇
  1981年   52篇
  1979年   55篇
  1978年   35篇
  1977年   38篇
  1976年   37篇
  1975年   32篇
  1970年   36篇
  1968年   43篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
AIMS: The aims of this observational study were to identify the special needs of children with Type 1 diabetes in schools from the parents' point of view and the difficulties experienced with full integration, and to define a series of interventions which may improve the situation. METHODS: Parents of children aged 3-18 years with Type 1 diabetes were eligible. Those who agreed to participate completed a self-reporting questionnaire which determined the effects of the disease on children, parents and school personnel, and addressed aspects including children's integration, glycaemic control, insulin administration, meals, sports, trips and attitudes of teachers and school colleagues to their disease. RESULTS: A total of 499 questionnaires were completed and validated. Median age of children was 11.5 years (95% CI 7.8-15.2). Only 34% of parents believed that teachers could recognize the symptoms of a mild hypoglycaemic episode. Seventeen per cent of parents experienced problems at their schools when they informed staff about their children's disease, 5% were finally not accepted and 8% were forced to change school. In some cases, they had to modify glucose monitoring (9%) and treatment administration (16%) because of a lack of cooperation from the school. CONCLUSIONS: Training sessions on Type 1 diabetes, an increase in the number of nurses, better availability of resources from diabetic associations to schools and improved communication between school personnel and parents were identified as key factors that may improve the full integration of the diabetic child in this setting.  相似文献   
42.
Objective The objective of the study was to determine the outcomes for primary gastrointestinal melanomas (PGIM). Material and methods The Surveillance, Epidemiology, and End Results database (1973–2004) was queried. Results Overall, 659 cases of PGIM were identified. The annual incidence of PGIM was approximately 0.47 cases per million in 2000. Overall median survival time was 17 months. Tumors were identified in the oral–nasopharynx (32.8%), anal canal (31.4%), rectum (22.2%), esophagus (5.9%), stomach (2.7%), small bowel (2.3%), gallbladder (1.4%), and large bowel (0.9%). Univariate analysis demonstrated age, tumor location, stage, surgery, and lymph node status were significant predictors of improved survival. MST has not been reached for tumors located in the large bowel, while tumors located in the stomach demonstrated the shortest median survival (5 months). Improvement in MST was observed for those patients undergoing surgical resection. The presence of lymph node involvement conferred a poorer prognosis. Multivariate analysis of the cohort identified that location, advanced tumor stage, failure to undertake surgical resection, positive lymph node status, and age were all independent predictors of poorer outcome. Conclusion PGIM occurs most often in the oral–nasopharynx and anal canal. Surgical extirpation is the only identifiable treatment modality that significantly improves survival.  相似文献   
43.
Crosslineage T-cell receptor delta (TCR delta) rearrangements are widely used as tumor markers for the follow up of minimal residual disease in childhood B-precursor acute lymphoblastic leukemia (ALL) by polymerase chain reaction (PCR). The major drawback of this approach is the risk of false-negative results due to clonal evolution. We investigated the stability of V delta 2D delta 3 rearrangements in a group of 56 childhood B-precursor ALL patients by PCR and Southern blot analysis. At the PCR level, V delta 2D delta 3-to-J alpha rearranged subclones (one pathway for secondary TCR delta recombination) were demonstrated in 85.2% of V delta 2D delta 3-positive patients tested, which showed that small subclones are present in the large majority of patients despite apparently monoclonal TCR delta Southern blot patterns. Sequence analysis of V delta 2D delta 3J alpha rearrangements showed a biased J alpha gene usage, with HAPO5 and J alpha F in 26 of 32 and 6 of 32 clones, respectively. Comparison of V delta 2D delta 3 rearrangement status between diagnosis and first relapse showed differences in seven of eight patients studied. In contrast, from first relapse onward, no clonal changes were observed in six patients studied. To investigate the occurrence of crosslineage TCR delta rearrangements in normal B and T cells, fluorescence-activated cell sorter-sorted peripheral blood CD19+/CD3- and CD19-/CD3+ cell populations from three healthy donors were analyzed. V delta 2D delta 3 rearrangements were detected at low frequencies in both B and T cells, which suggests that V delta 2-to-D delta 3 joining also occurs during normal B-cell differentiation. A model for crosslineage TCR delta rearrangements in B-precursor ALL is deduced that explains the observed clonal changes between diagnosis and relapse and is compatible with multistep leukemogenesis of B-precursor ALL.  相似文献   
44.
N C Inestrosa  J Alvarez 《Brain research》1988,441(1-2):331-338
Caliber and microtubular density of myelinated fibers, acetylcholinesterase (AChE) content and its accumulation at a ligature were studied in the phrenic nerve of mature (3-4 months) and aging (2-year-old) rats. The number of axons remained constant. The cross-sectional area of the nerve was 67% greater in the older group; the axoplasm, though, constituted about 20% of the nerve tissue irrespective of age. The mean cross-sectional area of myelinated axons was twice as big in aging compared to mature rats. All axons grew in the same proportion irrespective of their original caliber. The microtubular density of 3-microns axons was about 22 microtubules/micron2 in mature and aging rats. The AChE activity of aging rats was half as much as that of mature rats if it was expressed per wet weight of nerve tissue but did not change if it was expressed per nerve fiber. Twenty-four hours after ligation of the nerve, total AChE activity rose in mature and aging rats by ca. 168%; the molecular forms--asymmetric and globular--accumulated in the same proportion in both age groups. We conclude that myelinated axons grow in the adult stage of life but the structure of axoplasm, content of AChE per axon, and rate of fast transport remain lifelong features of nerve fibers.  相似文献   
45.
Intracerebral vascular reactivity induced by the nitric oxide (NO) donor isosorbide dinitrate (IDN, 5 mg sublingually) is more major and longer-lasting in migraine patients who develop delayed headache in response to the drug. The headache is purportedly due to neuronally-mediated vascular mechanisms. Indomethacin inhibits prostaglandin synthesis, which is involved in NO generation. Indomethacin also decreases cerebral blood flow by constricting precapillary resistance vessels. In the present study, the hemodynamic effects of indomethacin were evaluated in migraine patients and healthy controls by means of transcranial Doppler monitoring. Indomethacin caused a significant decrease in mean flow velocity in the middle cerebral artery. This was an additional effect to the mean velocity decrease induced by IDN. The interactions between the two drugs suggest that their effects on cerebral hemodynamics (and pain) may be of relevance both in understanding the role of NO in migraine pathogenesis and in evaluating symptomatic treatments for migraine attacks.  相似文献   
46.
The effects were studied of a toxin (Bainh) isolated from the secretion of the Caribbean sea anemone Bunodosoma granulifera on electrical and mechanical activities of rat ventricular muscle. The effects on the ionic currents of single rat and dog ventricular cardiomyocytes were studied using the whole-cell recording patch-clamp technique. In the concentration range from 1 to 10 mg/ml, Bainh increased the force of contraction and induced an increase in action potential duration of ventricular multicellular preparations. In single cardiomyocytes, at concentrations up to 10 mg/ml Bainh showed no significant effects on the sodium current. However, at 0.5–1 mg/ml it increased the L-type Ca current (ICaL) by 25–50%. This increase in ICaL was not voltage dependent and was reversible after washout. The transient outward current was not significantly affected by Bainh (1–10 mg/ml). In this concentration range, Bainh markedly (≈75%) increased the inward-going rectifier current, IK1. This effect that was not voltage dependent and was fully reversible upon returning to control solution. It is suggested that these effects on ionic currents could explain the positive inotropic action of Bainh on cardiac multicellular preparations.  相似文献   
47.
Myoclonic movements have been observed in depressed patients receiving therapeutic doses of clomipramine. Such movements, which appear in states of deep muscular relaxation such as sleep, do not appear to have any repercussion in the outcome of the depression and are reversible following withdrawal of the drug. In this study the plasma levels of clomipramine and desmethylclomipramine were determined and their possible relationship with myoclonus studied. No statistically significant relationships were found.  相似文献   
48.
Rupture of an intra-aortic balloon counterpulsator (IABCP) demands immediate removal. We report a case of thrombus formation within a Datascope IABCP secondary to IABCP rupture, necessitating surgical exploration for removal. There is a disturbing pattern of balloon ruptures with this type of IABCP.  相似文献   
49.
To evaluate the potential advantages of the administration of extradural morphine to control postoperative pain and its effects on respiratory function, 39 patients were randomly assigned to one of two groups before aortic surgery. The first group (20 patients) received intravenous analgesia as required (control group). The second group (19 patients) received extradural morphine in a programmed fashion. During the immediate postoperative period the following parameters were measured in both groups: respiratory rate, vital capacity, peak expiratory volume in the first second, PaO2, PaCO2, arterial pH, heart rate, and systolic and diastolic blood pressure. In the group treated with morphine the postoperative increase in heart and respiratory rate was significantly smaller than in the control group (p less than 0.01). Postoperative forced pulmonary volumes were higher in the morphine group (p less than 0.01). However, there were no differences in time of hospitalization between both groups. There were more complications in the control group, but the difference did not reach statistical significance.  相似文献   
50.
We evaluated the effects of the use of 1.2% isoflurane (group A) in a group of patients (n = 13) referred for mitral valve surgery, with pulmonary hypertension and right ventricular failure. We evaluated the hemodynamic status in baseline conditions, after isoflurane ++ administration and in relative hyper- and hypovolemia. We compared the results with those in 17 patients (group B) in identical clinical state who did not receive isoflurane during anesthesia. The evaluated parameters were: mixed venous Hb saturation (SvO2), heart rate (HR), pulmonary capillary pressure (PCP), central venous pressure (CVP), mean blood pressure (mBP), mean pulmonary arterial pressure (mPAP), cardiac index (CI), arteriolar pulmonary resistances (APR), peripheral vascular resistances (SVR), stroke index (SI), left ventricular work (LVW), right ventricular work (RVW), and O2 consumption (VO2). In group A, after isoflurane ++ administration, CI was 107.05% and 80% of baseline values in relative hypervolemia and hypovolemia, respectively. In group B (control), CI was 121.48% and 88.28% of basal values in relative hypervolemia and hypovolemia, respectively. In group A, SVR were 73.59% and 76.72% in hypervolemia and hypovolemia, respectively, while in group B they were 86.21% and 106.80%. In group A, APR were 90.85% and 89.96% in hypervolemia and hypovolemia, while they were 80.72% and 102.34% in group B. We found that isoflurane results in a greater peripheral than pulmonary vasodilation with a greater impairment in right ventricular function.  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