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   1807篇
  免费   131篇
  国内免费   36篇
耳鼻咽喉   6篇
儿科学   172篇
妇产科学   66篇
基础医学   228篇
口腔科学   44篇
临床医学   237篇
内科学   288篇
皮肤病学   35篇
神经病学   124篇
特种医学   207篇
外科学   108篇
综合类   39篇
预防医学   120篇
眼科学   57篇
药学   122篇
中国医学   1篇
肿瘤学   120篇
  2021年   14篇
  2019年   19篇
  2018年   23篇
  2017年   24篇
  2016年   22篇
  2015年   32篇
  2014年   32篇
  2013年   47篇
  2012年   66篇
  2011年   53篇
  2010年   60篇
  2009年   51篇
  2008年   40篇
  2007年   71篇
  2006年   59篇
  2005年   88篇
  2004年   63篇
  2003年   41篇
  2002年   36篇
  2001年   44篇
  2000年   51篇
  1999年   48篇
  1998年   67篇
  1997年   69篇
  1996年   67篇
  1995年   43篇
  1994年   58篇
  1993年   56篇
  1992年   50篇
  1991年   43篇
  1990年   40篇
  1989年   44篇
  1988年   69篇
  1987年   49篇
  1986年   39篇
  1985年   48篇
  1984年   20篇
  1983年   16篇
  1982年   14篇
  1981年   15篇
  1980年   16篇
  1979年   20篇
  1978年   15篇
  1977年   17篇
  1976年   20篇
  1975年   12篇
  1974年   10篇
  1973年   13篇
  1971年   9篇
  1967年   8篇
排序方式: 共有1974条查询结果,搜索用时 31 毫秒
11.
Cryopreserved spermatozoa from men having treatment for lymphoma or testicular tumour have been reported to function sub-optimally. We report on three successful pregnancies following gamete intra-Fallopian transfer (GIFT) using such cryopreserved sperm samples. In one case, ovum donation was required since the woman had premature ovarian failure.  相似文献   
12.
13.
Glucose is the principal energy substrate for the brain, and alterations in glucose availability can alter neuronal function, including cognitive performance. Investigators have previously demonstrated glucose-induced memory and attentional improvements in humans, including a previous report from this group in subjects with schizophrenia. However, the age- and dose-dependence of this effect in schizophrenia has not been addressed. This within-subjects, double-blind experiment evaluated the cognitive effects of placebo-controlled, multiple fixed-dose oral glucose administration (0 g, 25 g, 50 g, 75 g) in younger and older patients with schizophrenia (n = 20) and healthy age-matched controls (n = 20). Each dose condition was administered on a different morning after a 9-h fast, with cognitive testing and plasma sampling following dose administration on each day. Older patients demonstrated dose-dependent improvements in recall performance on a spatial delayed response task and reaction time on a delayed match to sample task, while younger patients had decreases in attentional performance at the 75-g dose compared to placebo. As in previous reports, patients demonstrated higher plasma glucose and insulin concentrations than controls in response to fixed glucose dosing. The results provide further evidence that glucose and/or insulin can regulate brain functions relevant to memory and attention, and suggest that systemic changes in glucose regulation in schizophrenia deserve further study.  相似文献   
14.
15.
We compared analgesia to the T4 dermatomal level with analgesia to the T7 level with and without prophylactic intramuscular administration of ephedrine 25 mg to determine the adequacy and side effects of such analgesia for caesarean section. Unmedicated patients were prehydrated (727 ± 303 ml of saline solution) and kept in a left lateral tilt position. Sufficient three per cent chloroprocaine was given to obtain analgesia to the T7 (T6-T8) dermatomal level (455 ± 128 mg) or to the T4 (T3-T5) dermatomal level (758 ± 168 mg). Patients who received analgesia to the higher level required less narcotic than those who received analgesia to the lower level (21 per cent versus 48 per cent) (p < 0.05). The incidence of hypotension in patients with analgesia at the T4 level was 21 per cent for those receiving ephedrine and 64 per cent for those who did not receive ephedrine (p < 0.05). Intramuscular administration of ephedrine 25 mg was not associated with increased plasma levels of norepinephrine, epinephrine or dopamine. There was no difference in Apgar score, behavioural test scores, neonatal acid-base status or oxygenation in children of mothers in the different groups. We conclude that a T4 dermatomal level of analgesia, combined with intramuscular administration of ephedrine 25 mg, provides more maternal comfort than a T7 level of analgesia does, with or without ephedrine, and is without significant maternal or foetal side effects.  相似文献   
16.
17.
Purpose: Our purpose was to determine if embryo cell stage at the time of intrauterine transfer correlates with pregnancy rate in patients treated with intracytoplasmic sperm injection (ICSI). Methods: We conducted a retrospective analysis of 455 embryo transfer cycles following ICSI and 304 conventional in vitro fertilization (IVF) and embryo transfer cycles in women aged 40 years or less. Abstracted information included grading of the embryo cell stage and quality at the time of transfer. Results: The overall ICSI pregnancy rate was 30.8%, while that of conventional IVF was 29.3%. However, the ICSI pregnancy rate fell to 9.3% for embryo transfers taking place at the two-cell stage but increased to 35.8% when at least one embryo had more than two cells, and this difference was statistically significant (P≤0.0001). The pregnancy rate following conventional IVF was 22.0% when only two-cell embryos were transferred and 32.0% when at least one of the embryos had more than two cells, but this difference in pregnancy rates was not significant (P>0.05). Conclusions: The stage of embryo development at transfer appears to exert a powerful influence on the successful establishment of pregnancy after ICSI.  相似文献   
18.
Background: In the multicenter European Intergroup Cooperative Ewing's Sarcoma Studies, localized Ewing tumors of bone were treated by combination chemotherapy with surgery and/or radiotherapy. Patients with primary metastases (pm-pts) were treated in high risk protocols.Patients and methods: One hundred seventy-seven pm-pts were registered from January 1990 to December 1995, 171 were evaluable for survival analyses. Thirty-six pm-pts received myeloablative megatherapy with stem cell rescue following conventional treatment. Bilateral whole lung irradiation (WLI) was administered in 57 pm-pts with pulmonary involvement. Event-free survival (EFS) rates were estimated by Kaplan–Meier analysis. Prognostic factors were identified by log-rank statistics, Cox procedures and logistic regression.Results: Eighty-nine deaths were recorded by 1 February 1997, EFS four years after diagnosis for all 171 pm-pts was 0.27. EFS for isolated lung metastases was 0.34, for bone/bone marrow (BM) metastases, 0.28, and for combined lung plus bone/BM metastases, 0.14 (P < 0.005). WLI improved outcome in case of isolated pulmonary involvement (0.40 vs. 0.19, P < 0.05). In pm-pts with combined pulmonary/skeletal metastases, intensification by megatherapy and/or WLI improved EFS from 0.00 to 0.27 (P = 0.0001).Conclusions: EFS four years after diagnosis in patients with disseminated Ewing tumors is 0.27. Whole lung irradiation and megatherapy improve outcome in subgroups of patients with disseminated Ewing disease.  相似文献   
19.
20.
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