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   6737篇
  免费   430篇
  国内免费   131篇
耳鼻咽喉   28篇
儿科学   170篇
妇产科学   109篇
基础医学   543篇
口腔科学   158篇
临床医学   588篇
内科学   1110篇
皮肤病学   71篇
神经病学   794篇
特种医学   70篇
外科学   625篇
综合类   575篇
现状与发展   2篇
一般理论   1篇
预防医学   1320篇
眼科学   111篇
药学   479篇
  3篇
中国医学   151篇
肿瘤学   390篇
  2024年   21篇
  2023年   242篇
  2022年   227篇
  2021年   457篇
  2020年   323篇
  2019年   253篇
  2018年   213篇
  2017年   224篇
  2016年   207篇
  2015年   156篇
  2014年   298篇
  2013年   545篇
  2012年   272篇
  2011年   317篇
  2010年   265篇
  2009年   314篇
  2008年   303篇
  2007年   318篇
  2006年   252篇
  2005年   253篇
  2004年   219篇
  2003年   182篇
  2002年   160篇
  2001年   142篇
  2000年   99篇
  1999年   106篇
  1998年   106篇
  1997年   80篇
  1996年   87篇
  1995年   71篇
  1994年   78篇
  1993年   53篇
  1992年   43篇
  1991年   51篇
  1990年   35篇
  1989年   44篇
  1988年   32篇
  1987年   19篇
  1986年   28篇
  1985年   46篇
  1984年   38篇
  1983年   28篇
  1982年   25篇
  1981年   17篇
  1980年   15篇
  1979年   6篇
  1978年   12篇
  1976年   4篇
  1975年   4篇
  1968年   2篇
排序方式: 共有7298条查询结果,搜索用时 15 毫秒
61.
Trends in pubertal development in Europe   总被引:8,自引:0,他引:8  
The secular changes in growth and maturation can be seen as indicators of socio-economic and health status. In most European countries the age of onset of puberty and of menarcheal age has been decreasing during the past few decades. The duration of puberty seems also to decrease, though few studies provide sufficient data to support this postulation. The four Dutch nationwide growth surveys are useful examples assessing the secular trend in pubertal development over the past 45 years. Genetic and environmental factors contribute to the secular changes. Environmental factors seem to be the most important. Recently, attention has been given to substances with oestrogen-like actions that are present in nutrients. The possible role of these substances in growth and maturation is discussed.  相似文献   
62.
In a retrospective study, antibody to hepatitis C virus (anti-HCV antibody) was measured in 80 patients with acute viral hepatitis (type A, 18; type B, 21; type non-A,non-B, 41). Anti-HCV antibody was found in 12 of 20 patients (60%) with non-A,non-B post-transfusion hepatitis (NANB-PTH) and in 9 of 21 patients (43%) with sporadic NANB hepatitis (NANB-SPO). Patients with acute hepatitis type A or type B did not have anti-HCV antibody. The number of patients who developed chronic hepatitis was greater in the group with anti-HCV antibody than in the anti-HCV negative group in both NANB-PTH and NANB-SPO. The difference was significant in those with NANB-PTH (P less than 0.05). To investigate the relationship between the long-term prognosis of NANB-PTH and the course of anti-HCV, we studied anti-HCV antibody in 12 patients who developed chronic type C hepatitis (C-CH) after PTH and followed them for more than 5 years after the development of PTH. One year after the development of PTH, all 12 had anti-HCV antibody. Five lost anti-HCV antibody (group 1) while 7 remained positive (group 2) at the final examination. Four of the 5 patients in group 1 had normal serum transaminases; however, abnormal transaminase persisted in all 7 patients in group 2 until the end of follow-up (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
63.
Helper T cell signaling is initiated by the aggregation of TCRwith the induction of tyrosine kinase activity as one of theearliest consequences. Here, a theoretical model for antigen-inducedunresponsiveness is presented that relies on a cascade of tyrosinephosphorylation- dephoshorylation cycles. A mechanism is describedfor both desensitization in the presence of antigen and persistentlowering of cell responsiveness after stimulus removal. An importantcomponent of the model, leading to bistability, is the presenceof autophosphorylating protein tyrosine kinases in the earlysteps of TCR signaling. One of its predictions is that, followingstimulation, the net phosphorylative activity of these receptor-associatedtyrosine kinases will remain above background level after removalof the antigen. It is proposed that this residual tyrosine kinaseactivity is linked to a deficient signal transduction capacityof the TCR system that leads to a state of prolonged unresponsiveness.In addition, the present analysis defines the notion of a signalingthreshold for hyporesponsiveness induction, associated witha durable switch and amplification of the net tyrosine kinaseactivity. This approach emphasizes the role of tyrosine kinasesin the down-regulation of cellular competence.  相似文献   
64.
We aimed to assess prevalence, birth outcome, associated anomalies and prenatal diagnosis of congenital clubfoot in Europe using data from the EUROCAT network, and to validate the recording of congenital clubfoot as a major congenital anomaly by EUROCAT registries. Cases of congenital clubfoot were included from 18 EUROCAT registries covering more than 4.8 million births in 1995–2011. Cases without chromosomal anomalies born during 2005–2009, were randomly selected for validation using a questionnaire on diagnostic details and treatment. There was 5,458 congenital clubfoot cases of which 5,056 (93%) were liveborn infants. Total prevalence of congenital clubfoot was 1.13 per 1,000 births (95% CI 1.10–1.16). Prevalence of congenital clubfoot without chromosomal anomaly was 1.08 per 1,000 births (95% CI 1.05–1.11) and prevalence of isolated congenital clubfoot was 0.92 per 1,000 births (95% CI 0.90–0.95), both with decreasing trends over time and large variations in prevalence by registry. The majority of cases were isolated congenital clubfoot (82%) and 11% had associated major congenital anomalies. Prenatal detection rate of isolated congenital clubfoot was 22% and increased over time. Among 301 validated congenital clubfoot cases, diagnosis was confirmed for 286 (95%). In conclusion, this large population‐based study found a decreasing trend of congenital clubfoot in Europe after 1999–2002, an increasing prenatal detection rate, and a high standard of coding of congenital clubfoot in EUROCAT.  相似文献   
65.
With the application of liver transplantation for patients with biliary atresia (BA), we have had the opportunity to review the clinicopathologic features of the native livers from 10 transplanted BA patients. A single large nodule at porta hepatis (hilar nodule) was noted in three of 10 patients, and an ill-defined nodule-like lesion at porta hepatis was present in two other patients. The three BA patients with hilar nodules were long-term survivors, compared to the patients with nodule-like and those without nodules. The hilar nodules measured between 5.0 cm and 8.0 cm and histologically, they were partly surrounded by fibrous septa with relatively well-preserved liver architectures and fewer inflammatory cells at the portal triads when compared to the surrounding cirrhotic lesions. No nuclear or cellular atypia was observed. Proliferating cell nuclear antigen labeling index was higher in the surrounding cirrhotic lesions than the hilar nodules. The nodule-like lesions at porta hepatis also showed similar light microscopic and immunohistochemical features as the hilar nodules. These hilar nodules did not seem to contain any malignant potential. The benign histology with relatively well-preserved liver architecture and the preferential site of occurrence at porta hepatis where bile seemed to flow more smoothly, suggested possible residues of less-affected hepatic tissues.  相似文献   
66.
A variety of adverse reactions to local anesthetics has been described, some of which are thought to be allergic. Different protocols of prick and intradermal skin tests as well as subcutaneous challenge tests are used to select a local anesthetic which can safely be used. Their long-term effectiveness has not yet been assessed. Twenty-eight patients with a history of adverse reaction to local anesthetics were evaluated over a 3-year period. Loss of consciousness occurred in eight patients, skin reaction in nine, and vagal symptoms in eight. Various reactions were recorded in the remaining three patients. Rapid spontaneous recovery was the rule, suggesting that immediate allergic reaction and, in particular, anaphylactic reaction were unlikely. Investigation allowed the selection of a tolerated anesthetic in all cases. Reexposure occurred in 19 patients 16–50 months after evaluation and 6.8 ± 5.5 years after the first reaction. No patient presented a second reaction. In conclusion, adverse reactions to local anesthetics seem to be, in most cases, not allergic in nature. Evaluation protocols are effective in selecting an agent susceptible to tolerance, but are time consuming. However, they probably contribute to an important reassurance effect that is likely to increase tolerance to subsequent local anesthetic administration. Simplification of the protocols and better patient selection are proposed.  相似文献   
67.
Experiments were performed to investigate evoked focal potentials in slices of rat olfactory cortex. The results showed that 1 M corticotropin-releasing factor (CRF; corticoliberin) increases the frequency of posttetanic potentiation, which had a shorter delay phase than in control experiments. Posttetanic potentiation during perfusion with 0.1 M corticoliberin had a longer delay phase than in control experiments.  相似文献   
68.
Dendrites and spines undergo dynamic changes in physiological and pathological conditions. Dendritic outgrowth has been observed in surviving neurons months after ischemia, which is associated with the functional compensation. It remains unclear how dendrites in surviving neurons are altered shortly after ischemia, which might reveal the mechanisms underlying neuronal survival. Using primary cortical cultures, we monitored the dendritic changes in individual neurons after oxygen-glucose deprivation (OGD). Two to four hours of OGD induced approximately 30–50% cell death in 24 h. However, the total dendritic length in surviving neurons was significantly increased after OGD with a peak at 6 h after re-oxygenation. The increase of dendritic length after OGD was mainly due to the sprouting rather than the extension of the dendrites. The dendritic outgrowth after 2 h of OGD was greater than that after 4 h of OGD. Application of NMDA receptor blocker MK-801 abolished OGD-induced dendritic outgrowth, whereas application of AMPA receptor antagonist CNQX had no significant effects. These results demonstrate a NMDA receptor-dependent dendritic plasticity shortly after OGD, which provides insights into the early response of surviving neurons after ischemia.  相似文献   
69.
长期生存癌症患者的述情障碍   总被引:8,自引:1,他引:8  
目的:探讨长期生存癌症患者的述情障碍及其相关因素,方法:采用多伦多述情障碍量表及症状自评量表,对36例长期生存癌存患者测评,并与45例正常人进行对照比较,结果:(1)癌症组与对照组在SCL-90评价中无显著性差异(P>0.05)。(2)癌症组TAS总分值明显高于对照组,其中以Ⅱ、Ⅲ、Ⅳ因子尤为明显(P<0.05-0.01)。(3)Ⅰ因子与躯体化、焦虑、恐怖焦虑及精神病症呈显著性正相关(P<0.05)。Ⅲ因子与强迫性,人际关系敏感,敌意及精神病症呈显著性负相关(P<0.05)。Ⅳ因子与偏执化呈显著性负相关(P<0.05)。结论:长期生存癌症患者虽然SCL-90测评可正常,但存在较明显的述情障碍。  相似文献   
70.
目的:考察大、中学生对文化维度的知觉的情况和发展趋势。方法:用Trandis编制的个人主义-集体主义量表(Individualism-Collectivism Scale)对1760名大、中学生进行测量。结果:大、中学生对文化维度的知觉存在年龄效应;随着年龄增加,对集体主义维度的知觉从42.05%下降到27.40%,而对个人主义维度的知觉从5.01%上升到18.58%;水平维度的知觉从47.06%下降到40.71%;垂直维度的知觉从4.14%上升到6.19%。结论:大、中学生对文化维度的知觉的差异主要表现在个人主义和集体主义的维度,水平维度和垂直维度有轻微的波动。  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