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   10629篇
  免费   530篇
  国内免费   56篇
耳鼻咽喉   115篇
儿科学   188篇
妇产科学   224篇
基础医学   1205篇
口腔科学   273篇
临床医学   803篇
内科学   2840篇
皮肤病学   148篇
神经病学   1128篇
特种医学   304篇
外科学   1378篇
综合类   27篇
一般理论   3篇
预防医学   476篇
眼科学   204篇
药学   874篇
中国医学   14篇
肿瘤学   1011篇
  2024年   9篇
  2023年   64篇
  2022年   145篇
  2021年   266篇
  2020年   164篇
  2019年   213篇
  2018年   243篇
  2017年   214篇
  2016年   244篇
  2015年   262篇
  2014年   354篇
  2013年   543篇
  2012年   772篇
  2011年   793篇
  2010年   428篇
  2009年   413篇
  2008年   725篇
  2007年   775篇
  2006年   762篇
  2005年   714篇
  2004年   706篇
  2003年   634篇
  2002年   572篇
  2001年   81篇
  2000年   78篇
  1999年   58篇
  1998年   113篇
  1997年   79篇
  1996年   82篇
  1995年   80篇
  1994年   77篇
  1993年   71篇
  1992年   56篇
  1991年   49篇
  1990年   45篇
  1989年   44篇
  1988年   29篇
  1987年   27篇
  1986年   35篇
  1985年   21篇
  1984年   24篇
  1983年   25篇
  1982年   24篇
  1981年   28篇
  1980年   11篇
  1979年   8篇
  1978年   9篇
  1977年   6篇
  1976年   7篇
  1972年   5篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Four cases of ependymoma of the filum terminale occurring in childhood are reported. The clinical, therapeutic and prognostic features seen at this age and in adults were compared.  相似文献   
82.
4-N-Alkylamino derivatives and corresponding ammonium quaternary salts of tetrahydro-1,4-benzodiazepin-5-one were synthesized and evaluated for psychotropic activity in mice by ip via. This study was also extended to some nitro and amino derivatives of tetrahydro-1,4-benzodiazepin-5-one. Compounds were devoid of tranquilizing activity and in comparison with two classical benzodiazepines, chlordiazepoxide and diazepam, they showed high toxicity and little or no effect on motor coordination, motor activity, and maximal electroshock. On some "in vitro" tests the compounds exhibited pharmacological properties when they were used at high concentrations.  相似文献   
83.
84.
85.
We measured, by immunohistochemistry, HMGA1 protein expression in 212 breast tissue specimens: 6 normal samples, 28 hyperplastic lesions (13 with cellular atypia), 11 fibroadenomas, 10 in situ ductal carcinomas, 144 ductal carcinomas, and 13 lobular carcinomas. HMGA1 was not expressed in normal breast tissue; HMGA1 staining was intense in 40% of hyperplastic lesions with cellular atypia and in 60% of ductal carcinomas and weak in fibroadenomas and in hyperplastic lesions without cellular atypia. Because HMGA1 expression was similar among ductal breast carcinomas with different histologic grading, we evaluated the association between HMGA1 expression and that of other markers of breast carcinoma invasion (estrogen and progesterone receptors, Ki-67 antigen, and ErbB2) in 21 cases of grade 3 breast ductal carcinomas and 7 cases of breast lobular carcinomas. We found that HMGA1 expression tended to be associated only with c-erbB-2 expression (Spearman rho: 0.36; P=0.065). Taken together, these results suggest that HMGA1 expression might be a novel indicator for the diagnosis and prognosis of human breast cancer.  相似文献   
86.
PURPOSE: To assess potential new prognostic factors and to validate the AIDS Clinical Trials Group (ACTG) for AIDS-related Kaposi's sarcoma (AIDS-KS) staging system in the highly active antiretroviral therapy (HAART) era. PATIENTS AND METHODS: We collected epidemiologic, clinical, staging, and survival data from 211 patients with AIDS-KS enrolled in two prospective Italian human immunodeficiency virus (HIV) cohort studies. We included in the analysis all patients with the diagnosis of KS made from January 1996, the time at which HAART became available in Italy. RESULTS: In the univariate analysis, survival was not influenced by sex, age, level of HIV viremia at KS diagnosis, HAART at KS diagnosis (HAART-na?ve v HAART-experienced), or type of HAART combination. Regarding ACTG classification, the 3-year survival rate was 85% for T0 patients and 69% for T1 patients (P =.007), 83% for S0 patients and 63% for S1 patients (P =.003), and 83% for I0 patients and 71% for I1 patients (P =.06). In the multivariate analysis, only the combination of poor tumor stage (T1) and poor systemic disease (S1) risk identified patients with unfavorable prognosis. The 3-year survival rate of patients with T1S1 was 53%, which was significantly lower compared with the 3-year survival rates of patients with T0S0, T1S0, and T0S1, which were 88%, 80%, and 81%, respectively (P =.0001). CONCLUSION: In the era of HAART, a refinement of the original ACTG staging system is needed. CD4 level does not seem to provide prognostic information. Two different risk categories are identified: a good risk (T0S0, T1S0, T0S1) and a poor risk (T1S1).  相似文献   
87.
PURPOSE: Malignant peripheral nerve sheath tumor (MPNST) can arise sporadically or in association with neurofibromatosis type 1. Deletions at the 9p21 locus have been reported in these tumors. To additionally characterize the status of this chromosomal region, in this study we performed a comprehensive, mostly PCR-based molecular analysis of the three tumor suppressor genes p15(INK4b), p14(ARF) and p16(INK4a) located at the 9p21 locus in 26 cryopreserved MPNSTs. EXPERIMENTAL DESIGN: Fourteen neurofibromatosis type 1-related and 12 sporadic cases were investigated for homozygous deletion coupled with fluorescent in situ hybridization, promoter methylation, and mutational analysis, as well as m-RNA expression. RESULTS: The results showed that an inactivation of one or more genes occurred in 77% of MPNSTs and was mainly achieved through homozygous deletion (46%), which, in turn, encompassed all of the three tandemly linked genes in 83% of the deleted cases. Promoter methylation was at a less extent involved in gene silencing (18%), and no mutations were found. Loss of function at DNA level strongly correlated with loss of mRNA expression accounting for 80% of the cases. Because of the close relationship between p14(ARF) and TP53 and between p15(INK4b)/p16(INK4a) and Rb, these results support a model of a coinactivation of TP53 and Rb pathways in 75% of MPNSTs, with functional consequences on cell growth control and apoptosis. CONCLUSIONS: The inactivation of the 9p21 locus is a frequent and peculiar hallmark of MPNST genetic profile leading also to an impaired apoptosis that could be taken into account in treatment planning of these tumors.  相似文献   
88.
PURPOSE: Imatinib (Glivec) is a potent inhibitor of bcr/abl, an oncogenic fusion protein that causes chronic myelogenous leukemia (CML). alpha1 acid glycoprotein (AGP) binds to imatinib with high affinity and inhibits imatinib activity in vitro and in vivo in an animal model. A pharmacokinetics analysis of imatinib was undertaken in CML patients. EXPERIMENTAL DESIGN: Imatinib plasma concentrations were measured in 19 CML patients treated with imatinib (400 or 600 mg/day). Five patients received a concomitant short-term course of clindamycin (CLI). RESULTS: A positive correlation between AGP and imatinib plasma levels was observed. CLI administration decreased imatinib plasma concentrations, evaluated as area under the curve (AUC) and peak concentrations (C(max)). The effects of a bolus of CLI was studied in three patients on imatinib 23 h after the last imatinib dose. Within 5-10 min in three of three cases, CLI caused a decrease in imatinib plasma concentrations of 2.6-, 2.7-, and 4.7-fold, respectively. In vitro experiments using fresh blasts from CML patients showed that AGP, at concentrations observed in the patients, decreased imatinib intracellular concentrations up to 10 times and blocked imatinib activity. The incubation with CLI restored imatinib intracellular concentrations and biological activity. CONCLUSION: AGP exerts significant effects of the pharmacokinetics, plasma concentrations, and intracellular distribution of imatinib in CML patients; these data indicate that plasma imatinib levels represent unreliable indicators of the cellular concentrations of this molecule.  相似文献   
89.
In vitro exposure to ecstasy (3,4-methylenedioxymethamphetamine, MDMA) alters some immune parameters such as T-cell regulatory function, cytotoxic T-lymphocyte activity, natural killer cell activity and macrophage function. Administration of MDMA in rats produces a suppression of lympho-proliferation response and a decrease in circulating lymphocytes, accompanied by an increase in plasma corticosterone. It was postulated a direct action of MDMA on lymphocytes or rather an indirect action mediated by the hypothalamic pituitary adrenal axis (HPA-AXIS) and/or the sympathetic nervous system (SNS). Acute MDMA treatment effected on healthy-volunteers produces an immune dysfunction associated with pharmaceutical characteristics and so with MDMA plasma concentrations. There is a decrease in CD4+ T-cells and functional responsiveness of lymphocytes, while percentage of natural killer cells increases. A contemporary rise of cortisol plasma concentrations supports the hypothesis of MDMA-induced release of corticotrophin-releasing factor from the hypothalamus and subsequent HPA-axis and SNS activation.  相似文献   
90.
OBJECTIVE: Retrospective study and review of the complications other than those related to the facial nerve and hearing, encountered in acoustic neuroma surgery. Also, an evaluation of hospital stay and its relation with various factors. STUDY DESIGN: Retrospective case review. SETTING: Tertiary neurotologic and skull base referral center. PATIENTS: A series of 707 patients who underwent surgical removal of acoustic neuroma from April 1987 to December 2001. INTERVENTIONS: The surgical approaches used were the enlarged translabyrinthine approach, the enlarged middle fossa approach, and the retrosigmoid approach. In a small number of cases, the operations were performed through other approaches. MAIN OUTCOME MEASURES: The duration of hospital stay and appearance of complications in the perioperative period along with their management. Results related to the facial nerve and hearing were not considered in this study. RESULTS: The most frequent complication was abdominal subcutaneous hematoma (site of fat harvest), which occurred in 23 patients (3.2%). Cerebrospinal fluid leak was present in 20 patients (2.8%), 15 of whom needed revision surgery. Other complications included VIth cranial nerve dysfunction in 12 cases (1.68%), subdural hematoma in 3 cases (0.4%), cerebellopontine angle hematoma in 4 cases (0.6%), cerebellar edema in 2 cases (0.28%), brainstem hematoma in 1 case (0.14%), transitory aphasia in 1 case (0.14%), and lower cranial nerve dysfunction in 1 case (0.14%). Mortality occurred in only one case (0.14%). Medical complications seldom occurred. The postoperative hospital stay ranged from 2 to 36 days, with an average of 6.4 days. The overall hospital stay diminished over time from 10.2 days in 1987 to 1990, to 4.9 days in 2001. There was a significant relation between hospital stay and tumor size, approach used, and presence/absence of complications. CONCLUSIONS: Perioperative complications in acoustic neuroma surgery do exist, but this study demonstrated how low the incidence is. The authors believe that the low percentage of complications is mainly attributable to the majority of operations being carried out in specialized clinics, where they are considered routine operations. They believe that following individualized approaches, depending on tumor size and on the preoperative function of the cranial nerves, is the proper way to reach a significant reduction in complications while maintaining a high percentage of total tumor removal. The results of this study, considered as a basis of comparison with other studies, will certainly be useful in preoperative patient counseling.  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