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   11241篇
  免费   1235篇
  国内免费   20篇
耳鼻咽喉   98篇
儿科学   389篇
妇产科学   217篇
基础医学   1490篇
口腔科学   197篇
临床医学   1427篇
内科学   2188篇
皮肤病学   128篇
神经病学   1110篇
特种医学   329篇
外科学   1347篇
综合类   730篇
一般理论   13篇
预防医学   1138篇
眼科学   338篇
药学   731篇
中国医学   3篇
肿瘤学   623篇
  2022年   79篇
  2021年   213篇
  2020年   132篇
  2019年   181篇
  2018年   285篇
  2017年   173篇
  2016年   177篇
  2015年   166篇
  2014年   257篇
  2013年   452篇
  2012年   502篇
  2011年   499篇
  2010年   333篇
  2009年   279篇
  2008年   457篇
  2007年   524篇
  2006年   541篇
  2005年   524篇
  2004年   470篇
  2003年   438篇
  2002年   440篇
  2001年   418篇
  2000年   405篇
  1999年   380篇
  1998年   145篇
  1997年   123篇
  1996年   155篇
  1995年   133篇
  1994年   97篇
  1993年   123篇
  1992年   287篇
  1991年   272篇
  1990年   284篇
  1989年   230篇
  1988年   207篇
  1987年   230篇
  1986年   182篇
  1985年   148篇
  1984年   150篇
  1983年   130篇
  1982年   96篇
  1981年   62篇
  1980年   67篇
  1979年   108篇
  1978年   97篇
  1977年   81篇
  1976年   66篇
  1975年   70篇
  1973年   56篇
  1970年   56篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
31.
During the past 10 years, numerous phase I-II studies were conducted and provided clinical experience with combined radiation therapy and hyperthermia treatments. Among the rare complications reported in these combined radiation therapy-hyperthermia trials were myonecrosis and peripheral neuropathy which were felt, mainly on a clinical basis, to be caused by local heat damage. Recently, such complications were noted in two patients with recurrent prostatic cancer treated in our department with radiation therapy combined with deep regional hyperthermia delivered by the Sigma-60 applicator of the BSD 2000 hyperthermia system (Salt Lake City, UT, USA). Analysis of the results of three-dimensional modelling of the SAR (specific absorption rate, W/kg) pattern in these patients indicated high SAR at the sites of the complications. Pretreatment three-dimensional modelling or other methods of predicting potential areas of high power deposition may have a role for future hyperthermia treatment planning aiding in the prevention of possible local heat damage and providing improved delivery of heat to the target volume.  相似文献   
32.
This cross-sectional study used a semi-automated analysis technique to quantify regional brain cerebrospinal fluid (CSF) volumes derived from computed tomography (CT) in 84 healthy men ranging from 21 to 82 years of age and 28 patients meeting Research Diagnostic Criteria for alcohol dependence. The goals were to replicate an earlier CT study of an independent sample of alcoholic and control subjects (Pfefferbaum et al., 1988a; Zipursky et al., 1988) and to compare CT assessments of brain changes with magnetic resonance imaging (MRI) assessments made in the same alcoholic patients (Pfefferbaum et al., 1992). Regional brain changes associated with normal aging were derived by regression analysis, using CT data collected from the healthy control subjects. As in the earlier CT study and in the concurrent MRI study, ventricular and sulcal CSF volumes in alcoholic patients were greater than would be expected for their age. Furthermore, the present CT study replicated the previous CT and MRI findings of a positive relationship between age and CSF volume enlargement in alcoholic patients over and above the normal age-related increase in CSF volume, suggesting greater vulnerability of the aging brain to alcohol. Comparison of CT-and MRI-derived estimates of ventricular and cortical sulcal volume revealed high correlations (>0.80). MRI and CT produced similar absolute ventricular volumes, while MRI produced larger sulcal volume estimates than did CT. The difference in sulcal volume estimate may be due to differences between CT and MRI in slice thickness and sensitivity to partial volume effects.  相似文献   
33.
A series of new 9-N-alkyl derivatives of 9(S)-erythromycylamine has been synthesized by reductive alkylation of erythromycylamine with aliphatic aldehydes and sodium cyanoborohydride. Alternative syntheses employing hydrogenation methods have also been developed. These new 9-N-alkyl derivatives possess excellent antimicrobial activity in vitro and in vivo, especially when administered orally to treat experimental infections in mice. From structure-activity studies, 9-N-(1-propyl)erythromycylamine (LY281389) was selected as the most efficacious derivative. These methods have also been extended to the synthesis of some 9-N,N-dialkyl derivatives of erythromycylamine.  相似文献   
34.
The resazurin reduction test provides an assessment of sperm activity   总被引:1,自引:0,他引:1  
OBJECTIVE: The objective of the study was to determine if reduction of the dye resazurin by semen could be correlated with the concentration of motile sperm. DESIGN: After assessment of sperm count and motility, specimens were incubated for 1 hour with resazurin (25 micrograms/mL of semen) and visual color changes indicative of dye reduction noted. SETTING: Specimens were obtained from men seeking care for infertility at one of four sites: (1) University of California, San Francisco (UCSF) In Vitro Fertilization Program; (2) UCSF Andrology Laboratory; (3) a gynecological practice in Maine; and (4) a private andrology laboratory in Southern California. PATIENTS: Individuals were self-selected by their desire to have a semen analysis in conjunction with the diagnosis or treatment of infertility. INTERVENTIONS: None. MAIN OUTCOME MEASURE: The reduction of the dye resazurin and its correlation with motile sperm density. RESULTS: When the motile sperm concentration was greater than or equal to 20 X 10(6)/mL, 86% of specimens produced a positive color change. Conversely, 86% of specimens with a motile sperm concentration of less than 20 X 10(6)/mL either did not change color or changed only over a narrow range. CONCLUSION: Reduction of resazurin offers an assessment of the active sperm in a specimen without the need to do a sperm count or evaluation of motility.  相似文献   
35.
Treatment with the monoclonal antibody OKT3 specific for the CD3 complex associated with the T cell antigen receptor can reverse acute rejection of human renal allografts. However, efficacy of anti-CD3 antibodies for treatment of patients with acute graft-versus-host disease after marrow transplantation has not been established. The dose-limiting side effects resulting from T cell activation induced by some anti-CD3 antibodies in vivo have discouraged their use for this application. We now report a phase I-II study of GVHD treatment with the anti-CD3 antibody BC3, a monoclonal murine IgG2b that, unlike OKT3, does not activate T cells. Fourteen patients were treated with BC3 after progression of acute GVHD despite treatment with cyclosporine and corticosteroids, and three patients received BC3 as primary treatment for GVHD. BC3 was administered at a dose of 0.1 or 0.2 mg/kg/day for seven or eight days. Five patients achieved complete resolution of GVHD, eight patients had partial improvement, two patients had no change, and two patients had progression of GVHD on therapy. Responses were sustained in 8 of 13 patients. Mild chills, fever, hypertension, and chest discomfort occurred in various combinations following 6 of 17 (35%) initial infusions of BC3 and following 4 of 99 (4%) subsequent infusions. In each instance it was possible to continue BC3 therapy without adjusting the dose or treatment schedule. In each patient treated, the absolute count of peripheral blood lymphocytes decreased transiently but returned to baseline within 22 hr after the first infusion. Circulating T cells had surface CD3 molecules saturated by the infused antibody in all but one patient. Four patients survived longer than one year after treatment with antibody BC3, and 13 patients died of infection or organ failure. Administration of the nonmitogenic anti-CD3 antibody BC3 was associated with improvement in the clinical manifestations of GVHD with minimal acute toxicity. Efficacy of antibody treatment did not depend on depletion of circulating T cells. Therefore, antibody BC3 may be achieving therapeutic immunosuppression by modulating T cell function. Controlled studies in patients treated earlier in the course of GVHD should determine whether antibody BC3 can improve survival.  相似文献   
36.
BACKGROUND--Women appear to be increasingly susceptible to snoring and sleep disordered breathing after the menopause. This observation, coupled with the considerable sex difference in sleep apnoea, may be explained on the basis of a protective effect of female hormones. This study was carried out to determine whether hormone replacement therapy has a role in the management of obstructive sleep apnoea in postmenopausal women. METHODS--The effect of short-term (mean (SE) 50 (3) days) hormone replacement therapy with either oestrogen alone or in combination with progesterone on sleep disordered breathing was investigated in 15 postmenopausal women with moderate obstructive sleep apnoea. The effect of treatment on the ventilatory response to hypoxia and hypercapnia was assessed in 10 patients. RESULTS--There was no reduction in the clinical severity of obstructive sleep apnoea after hormone treatment despite an increase in the serum oestrogen level from 172 (23) to 322 (33) pmol/l. There was a small but clinically insignificant reduction in the apnoea/hypopnoea index during REM sleep from 58 (6) to 47 (7). There was no difference in response between the oestrogen only group and the oestrogen plus progesterone group. Hypercapnic ventilatory responsiveness did not change with hormone treatment, but an change with hormone treatment, but an increase in hypoxic ventilatory responsiveness was observed. CONCLUSIONS--These data indicate that short-term hormone replacement is unlikely to have an effective role in the clinical management of postmenopausal women with obstructive sleep apnoea. The observed reduction in the apnoea/hypopnoea index during REM sleep, however, suggests that longer term treatment, or the use of higher doses, may have an effect.  相似文献   
37.
The type and frequency of spinal therapeutic work being undertaken in the United Kingdom (UK) by clinicians with an interest in the surgcial treatment of disorders of the spine (primary and secondary subspecialty interest) were evaluated by means of a postal questionnaire. The willingness of respondents to take part in postgraduate spinal training was determined along with issues regarding accessibility of spinal services to non-specialist physicians in the health service in the UK. The results of 450 respondents provided insight into the types of procedures taking place, for example: primary spinal decompression was regularly carried out by 76% of surgeons, while at least 20% of respondents regularly carried out 66% of the procedures surveyed. We found that 10% of surgeons indicated that they were prepared to participate actively in postgraduate spinal surgical training.  相似文献   
38.
The complications of diabetes continue to present significant health risks despite improvements in conventional insulin therapy. Transplantation of pancreatic islet tissue has the potential to provide more precise glucose regulation and possibly minimize these implications. Recent advances in pancreatic islet isolation technology have facilitated investigation of islet allograft function in large animal models. These studies are fundamental to the development of methods for transplantation of allogeneic or xenogeneic islets in diabetic patients. This paper reviews the approaches which have been taken to prevent rejection and allow assessment of islet allograft function in the pancreatectomized dog model. These approaches include immunosuppression, immunomodulation of the donor tissue and isolation of allogeneic tissue within an immunoprotective membrane.  相似文献   
39.
Background Down syndrome is one of the commonest causes of intellectual disability. As life expectancy improves with early and more intensive surgical and medical treatments, people with the disorder are more likely to exhibit classic morbidity and mortality patterns and be diagnosed with diseases such as cancer. Methods A profile of cancer cases among people with Down syndrome has been compiled, based on the analysis of a linked data set that included information from the Disability Services Commission of Western Australian and the State Cancer Registry. Results and conclusions Although the total age‐ and sex‐standardized incidence ratios (SIRs) for people with Down syndrome were similar to that for the general population, SIRs for leukaemia were significantly higher while the incidence of certain other types of cancers was reduced. Overall, there was a lower incidence of solid tumours in Down syndrome, possibly reflecting the age profile of the study cohort.  相似文献   
40.
Pharmacy and therapeutics committees commonly cite a lack of generalizability as a reason for not incorporating cost-effectiveness information into decision making. To address this concern, many committees undertake site-specific economic evaluations, which are often limited by small sample sizes and nonrandomized designs. We show how 2 complementary approaches were used to minimize these limitations in an economic evaluation of abciximab at 1 institution. Using a propensity score methodology, we selected patients who did not receive abciximab for the comparison cohort. Then, we adopted a Bayesian, hierarchical, random-effects model to integrate site-specific and clinical trial data. We applied the posterior distributions of effectiveness with local cost data in a traditional decision-analytic model. In 74% of the simulations, abciximab was cost-effective at 1 institution at the $50,000 per life year saved threshold, assuming a 50:50 split of patients undergoing coronary stenting and angioplasty. Among patients undergoing coronary stenting, the cost-effectiveness ratio of the addition of abciximab was at or below the $50,000 per life year saved threshold in 66.0% of the simulations.  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