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   39952篇
  免费   2981篇
  国内免费   105篇
耳鼻咽喉   368篇
儿科学   1384篇
妇产科学   1095篇
基础医学   4691篇
口腔科学   613篇
临床医学   6720篇
内科学   7558篇
皮肤病学   542篇
神经病学   3666篇
特种医学   864篇
外国民族医学   1篇
外科学   3848篇
综合类   578篇
现状与发展   1篇
一般理论   54篇
预防医学   5322篇
眼科学   553篇
药学   2591篇
中国医学   45篇
肿瘤学   2544篇
  2023年   223篇
  2022年   214篇
  2021年   686篇
  2020年   504篇
  2019年   781篇
  2018年   939篇
  2017年   679篇
  2016年   777篇
  2015年   835篇
  2014年   1187篇
  2013年   1851篇
  2012年   2645篇
  2011年   2843篇
  2010年   1495篇
  2009年   1326篇
  2008年   2496篇
  2007年   2724篇
  2006年   2644篇
  2005年   2576篇
  2004年   2370篇
  2003年   2259篇
  2002年   2170篇
  2001年   518篇
  2000年   472篇
  1999年   514篇
  1998年   487篇
  1997年   392篇
  1996年   330篇
  1995年   381篇
  1994年   300篇
  1993年   303篇
  1992年   326篇
  1991年   334篇
  1990年   306篇
  1989年   285篇
  1988年   276篇
  1987年   264篇
  1986年   279篇
  1985年   274篇
  1984年   265篇
  1983年   227篇
  1982年   235篇
  1981年   221篇
  1980年   191篇
  1979年   177篇
  1978年   149篇
  1977年   131篇
  1976年   116篇
  1974年   119篇
  1973年   110篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
The trypanosome responsible for the majority of cases of human trypanosomiasis in Africa is Group 1 Trypanosoma brucei gambiense. Currently the most reliable test for the parasite is based on a single gene, which encodes a 47 kDa receptor-like T. b. gambiense-specific glycoprotein, TgsGP, expressed in the flagellar pocket of bloodstream forms. Although TgsGP has been demonstrated in T. b. gambiense throughout its geographic range, similar genes have been demonstrated in other T. brucei sspp. isolates, and there are no data on the extent of sequence variation in TgsGP. Here we have carried out a comparison of TgsGP sequences in a range of Group 1 T. b. gambiense isolates and compared the gene to homologues in other T. brucei sspp. in order to provide information to support the use of this gene as the key identification target for Group 1 T. b. gambiense. We demonstrate that the sequence of TgsGP is well conserved in Group 1 T. b. gambiense across the endemic range of gambian human trypanosomiasis and confirm that this gene is a suitable target for specific detection of this parasite. The TgsGp-like genes in some isolates of T. b. brucei, T. b. rhodesiense and Group 2 T. b. gambiense are closely similar to VSG Tb10.v4.0178, which may be the ancestral gene from which TgsGP was derived.  相似文献   
42.
43.
Background  Cardiac resynchronization therapy (CRT) is approved for the treatment of patients with advanced systolic heart failure and evidence of dyssynchrony on electrocardiograms. However, a significant percentage of patients do not demonstrate improvement with CRT. Echocardiographic techniques have been used for more accurate determination of dyssynchrony. Single photon emission computed tomography (SPECT) myocardial perfusion imaging has not previously been used to evaluate cardiac dyssynchrony. The objective of this study is to evaluate mechanical dyssynchrony as described by phase analysis of gated SPECT images in patients with left ventricular dysfunction, conduction delays, and ventricular paced rhythms. Methods and Results  A novel count-based method is used to extract regional systolic wall thickening amplitude and phase from gated SPECT images. Five indices describing the phase dispersion of the onset of mechanical contraction are determined: peak phase, phase SD, bandwidth, skewness, and kurtosis. These indices were determined in consecutive patients with left ventricular dysfunction (n=120), left bundle branch block (n=33), right bundle branch block (n=19), and ventricular paced rhythms (n=23) and were compared with normal control subjects (n=157). Phase SD, bandwidth, skewness, and kurtosis were significantly different between patients with left ventricular dysfunction, left bundle branch block, right bundle branch block, and ventricular paced rhythms and normal control subjects (all P<.001) Peak phase was significantly different between patients with right ventricular paced rhythms and normal control subjects (P=.001). Conclusions  A novel SPECT technique for describing left ventricular mechanical dyssyn-chrony has been developed and may prove useful in the evaluation of patients for CRT. This study was funded in part by a research grant from the Medtronic-Duke Strategic Alliance, of which Dr Borges-Neto is the primary investigator.  相似文献   
44.
Childbearing women and infants in developing countries continue to experience unacceptably high rates of mortality and morbidity in spite of targeted initiatives to address the problem. The aim of this study was to identify the beliefs and rituals of traditional birth attendants (TBAs) in one indigenous Guatemalan community to better understand the cultural influences on perinatal care practices. Ethnographic methods were used to increase understanding of the practice of 10 Mayan TBAs. Three themes were constructed: sacred calling, sacred knowledge and sacred ritual.  相似文献   
45.
The use of epidemiologic research designs and analytical methods is common in dietetics research. Food and nutrition professionals who seek to perform evidence-based practice or participate in research design, analysis, and communication need skills in the essentials of epidemiology. This is one of a series of monographs on research methodology that addresses these needs and supports the goals of the Board of Editors of the Journal of the American Dietetic Association to further enhance competency and skills. This monograph focuses on statistical approaches for univariate analyses used with the primary observational study designs associated with epidemiology. Tables illustrating the presentation and interpretation of these results are included.  相似文献   
46.
G J Gibson 《Primary care respiratory journal》2004,13(4):225; author reply 227-225; author reply 228
  相似文献   
47.
OBJECTIVE: The purpose of this study was to compare learning of a functional living skill in two contexts for individuals with long-term schizophrenia. METHOD: Forty-four people with schizophrenia were matched on cognitive level. One of each pair was randomly designated to either a clinic or home cooking group, with the other assigned to the remaining group. Cooking skill was assessed using the Kitchen Task Assessment-Modified (KTA-M) both before and after the intervention. Learning for each group was analyzed using t tests. A multiple regression analysis to control for baseline differences was used to compare the learning of the two groups. RESULTS: Participants in both groups scored significantly higher on the KTA-M after cooking lessons (t = 5.57, df = 21, p < .0001--clinic; t = 7.81. df = 21, p < .0002--home) reflecting learning of cooking skill; there was no statistically significant difference in scores on the KTA-M between the two groups based on where the learning took place (beta = -1.8, df = 42, p < 0.23). Qualitative differences between the learning environments provide suggestions for teaching functional living skills to this population. CONCLUSIONS: Learning new skills in the home was not better than learning in the clinic for people with schizophrenia in this study. Further research on the effect of context on learning for people with cognitive dysfunction and schizophrenia is recommended.  相似文献   
48.
BACKGROUND: To ascertain survival of ischemic advanced heart failure patients by treatment allocation, we examined the outcome of transplant assessment patients allocated to medical therapy, high-risk conventional surgery, or transplantation. METHODS: Patients were identified from the Papworth transplant database and excluded if primary etiology was not ischemic. Grouping was undertaken according to treatment allocation at initial assessment, and analysis was performed by intention to treat. Survival was computed from the time of assessment and Cox regression used to stratify patients according risk with the Heart Failure Survival Score. RESULTS: From May 1993 to September 2001, a total of 755 patients were admitted for transplant assessment, with 348 (46.1%) identified as having heart failure of ischemic origin. Variables required for calculation of the Heart Failure Survival Score was available in 273 patients (78.4%), and 20 patients (7.3%) were lost to follow-up. Of the remaining 253 patients, 89 (35.2%) were allocated to medical therapy, 32 (12.6%) to surgery, and 132 (52.2%) to transplantation. The relative risk (95% confidence limit) of death compared with medical therapy was 0.62 (0.28, 1.40) for surgery and 0.38 (0.24, 0.61) for transplantation in medium- to high-risk patients. For low-risk patients, the relative risks for death compared with medical therapy were 1.87 (0.63, 5.60) for surgery and 1.97 (0.79, 4.96) for transplantation. CONCLUSIONS: Transplantation improved survival of medium- and high-risk patients compared with medical therapy. In the low-risk group, this was not evident. However, repeated assessment of risk is required because the hazard for death rises steadily after the third year in these patients.  相似文献   
49.
PURPOSE: Currently, no drug treatment is available for strengthening underacting extraocular muscles (EOM) in strabismus. We showed previously that single injections of insulin-like growth factor (IGF-1) result in significant but short-term increases in muscle force generation. This study examined the effects of sustained release of IGF-1 on force generation in rabbit superior rectus muscles. METHODS: In adult rabbits, slow-release pellets containing IGF-1 were implanted on the global side of one superior rectus muscle. After 1 week, or 1, 2, 3, or 6 months, treated and control muscles were examined for force generation using an in vitro physiology apparatus. All muscles were prepared for histology and mean myofiber cross-sectional areas were determined. RESULTS: One and 3 months after pellet implantation, treated muscles generated significantly greater force than contralateral control muscles, whereas at 2 months, no significant difference was found. Force per cross-sectional area (mN/cm(2)) at 3 months also increased significantly in the treated muscles. Mean muscle cross-sectional area increased significantly after 1, 2, and 3 months of sustained exposure to IGF-1 compared with controls. After an additional 3 months without IGF-1 exposure, mean cross-sectional areas were significantly greater than controls but significantly reduced compared with areas at 1, 2, and 3 months. CONCLUSIONS: IGF-1 appears to be highly effective in increasing muscle force generation. Because slow release of IGF-1 results in sustained increases in EOM force generation, it may be a potentially useful alternative to surgical resection procedures because it avoids many of the potential long-term biomechanical hazards of resection surgery.  相似文献   
50.
A quantitative analysis of unpredictable saccadic and smooth pursuit ocular motor and manual tracking was performed in 15 mildly affected, previously untreated subjects suffering from Parkinson's disease and in age-matched normal controls. The patients' ocular saccades were characterised by an increased variability of their latencies and reduced accuracy, with normal velocity profiles apart from saccadic duration. Their smooth pursuit had a decreased velocity gain. Similar abnormalities were found with manual tracking. Clinical improvement with dopaminergic drugs was associated with an improvement of saccadic accuracy and smooth pursuit gain. It is postulated that the ocular motor changes seen in Parkinson's disease are contingent upon functional dopamine levels in the basal ganglia.  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