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   1886篇
  免费   80篇
  国内免费   15篇
耳鼻咽喉   12篇
儿科学   23篇
妇产科学   64篇
基础医学   138篇
口腔科学   52篇
临床医学   133篇
内科学   525篇
皮肤病学   39篇
神经病学   149篇
特种医学   57篇
外科学   449篇
综合类   2篇
预防医学   42篇
眼科学   25篇
药学   57篇
中国医学   2篇
肿瘤学   212篇
  2023年   9篇
  2022年   20篇
  2021年   49篇
  2020年   24篇
  2019年   37篇
  2018年   59篇
  2017年   30篇
  2016年   43篇
  2015年   62篇
  2014年   60篇
  2013年   81篇
  2012年   122篇
  2011年   117篇
  2010年   73篇
  2009年   72篇
  2008年   111篇
  2007年   133篇
  2006年   113篇
  2005年   92篇
  2004年   86篇
  2003年   66篇
  2002年   61篇
  2001年   53篇
  2000年   37篇
  1999年   40篇
  1998年   10篇
  1997年   13篇
  1996年   9篇
  1995年   12篇
  1994年   12篇
  1993年   5篇
  1992年   22篇
  1991年   32篇
  1990年   26篇
  1989年   22篇
  1988年   20篇
  1987年   16篇
  1986年   18篇
  1985年   16篇
  1984年   10篇
  1983年   6篇
  1979年   6篇
  1978年   5篇
  1976年   5篇
  1975年   5篇
  1974年   7篇
  1973年   6篇
  1972年   9篇
  1970年   4篇
  1967年   5篇
排序方式: 共有1981条查询结果,搜索用时 15 毫秒
131.
132.
We evaluated the possible association between smoking, coffee drinking, and alcohol consumption and Parkinson's disease (PD). The FRAGAMP study is a large Italian multicenter case–control study carried out to evaluate the possible role of environmental and genetic factors in PD. Adjusted ORs were estimated using unconditional logistic regression. Smoking, coffee, and alcohol consumption were also considered as surrogate markers of lifestyle and analysis was carried out considering the presence of at least one, two, or three factors. This latter analysis was separately performed considering Tremor‐Dominant (TD) and Akinetic‐Rigid (AR) patients. Four hundred ninety‐two PD patients (292 men and 200 women) and 459 controls (160 men and 299 women) were enrolled in the study. Multivariate analysis showed a significant negative association between PD and cigarette smoking (OR 0.51; 95%CI 0.36–0.72), coffee drinking (OR 0.61; 95%CI 0.43–0.87) and wine consumption (OR 0.62; 95%CI 0.44–0.86); a significant trend dose‐effect (P < 0.05) has been found for all the factors studied. We have also found a trend dose‐effect for the presence of at least one, two or three factors with a greater risk reduction (83%) for the presence of three factors. However, a different strength of association between TD and AR was found with a greater risk reduction for the AR patients. We found a significant inverse association between PD smoking, coffee, and alcohol consumption. When analysis was carried out considering the association of these factors as possible surrogate markers of a peculiar lifestyle the association was stronger for the AR phenotype. © 2010 Movement Disorder Society.  相似文献   
133.
Totaro A  Volpe A  Sacco E  Pinto F  Palma M  Bassi P 《Urologia》2010,77(4):232-239
The role of statistics in medical research starts at the planning stage of a clinical trial or laboratory experiment to establish the design and size of an experiment that will ensure a good prospect of detecting effects of clinical or scientific interest. Statistics is again used during data analysis (sample data) to make inferences valid in a wider population. In simple situations, computation of simple quantities such as P-values, confidence intervals, standard deviations, standard errors or application of some standard parametric or nonparametric tests may suffice. Moreover, despite the wide use of statistics in medical research, simple notions are sometimes misunderstood or misinterpreted by medical research workers, who have only a limited knowledge of statistics. This article, written for non-statisticians, is to explain what are the most common statistical tests used today in the field of medical research, tracing the evolution of statistical tests over time, in particular the introduction of nonparametric methods and, more recently, the NonParametric Combination (NPC) methodology. At the same time, this work seeks to identify some of the errors associated with their use, that often lead to an incorrect assessment and interpretation of results of medical research.  相似文献   
134.
Several substances such as growth hormone (GH), erythropoietin (Epo), and anabolic steroids (AS) are improperly utilized to increase the performance of athletes. Evaluating the potential cancer risk associated with doping agents is difficult since these drugs are often used at very high doses and in combination with other licit or illicit drugs. The GH, via its mediator, the insulin-like growth factor 1 (IGF-1), is involved in the development and progression of cancer. Animal studies suggested that high levels of GH/IGF-1 increase progression of androgen-independent prostate cancer. Clinical data regarding prostate cancer are mostly based on epidemiological studies or indirect data such as IGF-1 high levels in patients with prostate cancer. Even if experimental studies showed a correlation between Epo and cancer, no clinical data are currently available on cancer development related to Epo as a doping agent. Androgens are involved in prostate carcinogenesis modulating genes that regulate cell proliferation, apoptosis and angiogenesis. Most information on AS is anecdotal (case reports on prostate, kidney and testicular cancers). Prospective epidemiologic studies failed to support the hypothesis that circulating androgens are positively associated with prostate cancer risk. Currently, clinical and epidemiological studies supporting association between doping and urological neoplasias are not available. Nowadays, exposure to doping agents starts more prematurely with a consequent longer exposition period; drugs are often used at very high doses and in combination with other licit or illicit drugs. Due to all these elements it is impossible to predict all the side effects, including cancer; more detailed studies are therefore necessary.  相似文献   
135.
Background  A new procedure of hemostasis during laparoscopic total mesorectal excision is described. Methods  In our surgical department, from January 2004 to December 2007, 128 patients underwent laparoscopic total mesorectal excision. Among them, 47 patients underwent laparoscopic anterior resection after preoperative radiotherapy, 68 patients underwent laparoscopic anterior resection without preoperative radiotherapy, and 13 patients underwent laparoscopic abdominal perineal amputation. Results  In seven laparoscopic rectal surgery cases, we encountered unstoppable presacral bleeding, not amenable by conventional hemostatic solutions. In these cases we applied a simple staging hemostatic procedure. We first performed local compression: tamponing with a small gauze or absorbable fabric hemostat. If bleeding did not stop, we localized an epiploic or omental scrap and excised it by using bipolar forceps and use it as a plug on the tip of a grasping forceps. This plug is then put on the bleeding source and monopolar coagulation is applied by electrified dissecting forceps through the interposed grasping forceps. If bleeding did not stop, we used a little scrap of bovine pericardium graft and tacked it to the bleeding site using endoscopic helicoidal protack. Conclusions  Our experience suggests that this hemostatic step-by-step procedure is a valid option to control persistent presacral hemorrhages.  相似文献   
136.

Background

The appropriate surgical approach of a pancreatic multifocal disease that skips the body of the gland remains unknown. We sought to analyze a parenchyma-sparing surgical technique consisting of a middle-preserving pancreatectomy (MPP) evaluating feasibility, safety, and oncological and functional outcomes.

Patients and methods

Between 1999 and 2007, 5 patients affected by pancreatic benign or slow malignant multicentric body-sparing disease underwent MPP.

Results

There were 3 men and 2 women with a median age of 35 years (range 28-70 years). The median operative time was 365 minutes (range 330-440 minutes). Postoperative mortality was nil and postoperative morbidity was 1 (20%). At a median follow-up of 20 months (range 14-118 months) all of the patients are alive and disease-free. Overall, 2 patients developed insulin-dependent diabetes mellitus, as well as exocrine insufficiency. One patient developed only exocrine insufficiency.

Conclusions

MPP is a feasible procedure and might reduce the risk of both endocrine and exocrine insufficiency.  相似文献   
137.

Background  

The 1-year disease-related mortality after resection for pancreatic cancer is approximately 30%. This study examined potential preoperative parameters that would help avoid unnecessary surgery.  相似文献   
138.

Background/Aim

The definition of an extended criteria donor for orthotopic liver transplantation (OLT) remains controversial. The donor risk index (DRI) has become the main tool to define the marginality of hepatic grafts in the United States. The aim of this study was to prospectively evaluate the prognostic ability of DRI among a cohort of Italian patients undergoing OLT.

Methods

From December 2006 to March 2008, we prospectively calculated DRI in all consecutive cadaveric grafts. Recipient inclusion criteria were: adult patients with chronic liver disease enlisted for primary OLT. The primary end point was the incidence of primary graft dysfunction (PDF), namely, aspartate aminotransferase (AST) >2000 U/mL and prothrombin time <40% on postoperative days 2-7.

Results

We enrolled 74 donor-recipient pairs fulfilling the inclusion criteria. Donor characteristics included DRI 1.7 (range, 0.9-3.0); age 57 years (range, 18-81); ultrasound signs of steatosis in 22 donors (30%); and ischemia time was 536 minutes (range, 290-690). Recipient characteristics are: age 55 years (range, 27-68); hepatocellular carcinoma in 36 subjects (49%); MELD was 16 (range, 7-39); and Child-Pugh score was 8 (range, 6-14). In terms of the primary end points, the DRI did not provide a significant PDF predictor (P = .84). Among all evaluated donor and recipient variables, the following were related to the incidence of graft PDF: donor age (P = .07), ultrasound signs of steatosis (P = .02), donor AST (P = .05), cell saver infusion (P = .07), and warm (P = .04) and cold ischemia (P = .07) times.

Conclusion

The preliminary data of this study showed a poor correlation between DRI and PDF incidence after OLT.  相似文献   
139.
140.
Housing conditions change the emotional state of the animals. Ultrasound vocalizations (USVs) termed as 22 kHz are the usual components of the defensive responses of rats exposed to threatening conditions such as isolation. The amount of emission of 22 kHz USVs depends on the intensity of the aversive stimuli. While short periods of isolation caused an anxiolytic-sensitive enhancement of the defensive responses, long-term isolation tended to reduce the defensive performance of the animals to aversive stimuli. The dorsal periaqueductal gray (dPAG) is an important vocal center and a crucial structure for the expression of defensive response. While it has been shown that Substance P (SP) at this midbrain level is involved in the modulation of the defensive response, its role in the emission of ultrasound vocalizations has not been evaluated. In this study we examined whether the resocialization and local injections of SP into the dPAG have an influence on the isolation-induced 22 kHz USVs recorded within the frequency range of 18-26 kHz. Rats isolated for 1 day showed a significant increase in the number and duration of USVs, which were reversed by resocialization. On the other hand, 2-week isolation reduced the number and duration of 22 kHz USVs, which could not be reversed by resocialization. SP injections into the dPAG (35 pmol/0.2 microL) caused a reduction in the 22 kHz USVs. Pretreatment with the NK-1 receptor antagonist spantide (100 pmol/0.2 microL) blocked these effects but exhibited no effect when given alone. These findings suggest that 1-day and 2-week isolation recruit distinct brain defensive systems. Also, in agreement with the notion that intense fear is associated with the neural substrates of fear of the dPAG, activation of NK-1 receptors of this midbrain structure reduces the 22 kHz USVs.  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