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   7604篇
  免费   564篇
  国内免费   28篇
耳鼻咽喉   88篇
儿科学   295篇
妇产科学   178篇
基础医学   1104篇
口腔科学   176篇
临床医学   861篇
内科学   1483篇
皮肤病学   171篇
神经病学   775篇
特种医学   213篇
外科学   596篇
综合类   67篇
一般理论   5篇
预防医学   934篇
眼科学   169篇
药学   544篇
中国医学   10篇
肿瘤学   527篇
  2024年   12篇
  2023年   105篇
  2022年   161篇
  2021年   285篇
  2020年   197篇
  2019年   250篇
  2018年   291篇
  2017年   231篇
  2016年   263篇
  2015年   266篇
  2014年   322篇
  2013年   463篇
  2012年   629篇
  2011年   594篇
  2010年   331篇
  2009年   293篇
  2008年   499篇
  2007年   476篇
  2006年   434篇
  2005年   398篇
  2004年   346篇
  2003年   298篇
  2002年   244篇
  2001年   55篇
  2000年   54篇
  1999年   57篇
  1998年   63篇
  1997年   46篇
  1996年   40篇
  1995年   31篇
  1994年   27篇
  1993年   26篇
  1992年   34篇
  1991年   32篇
  1990年   31篇
  1989年   21篇
  1988年   41篇
  1987年   17篇
  1986年   20篇
  1985年   21篇
  1984年   18篇
  1983年   18篇
  1982年   13篇
  1981年   10篇
  1979年   11篇
  1978年   8篇
  1977年   14篇
  1974年   17篇
  1973年   11篇
  1971年   12篇
排序方式: 共有8196条查询结果,搜索用时 15 毫秒
1.
The purpose of this study was to evaluate a single-session peer-led safer sex intervention, based on the Information-Motivation-Behavioral Skills theoretical model, for college students residing in campus residence halls. Participants (N = 108) were assigned to either an hour long control or 5-module intervention session. Compared to the control condition, the intervention increased participants’ information and women’s subjective norms about preventative behavior. Both the control and intervention sessions increased intentions to perform preventative behaviors (e.g., keep condoms available). These preliminary results suggest that this intervention is promising for increasing constructs associated with safer sexual behavior and could easily be implemented by residence hall staff.  相似文献   
2.
3.
The objective of this study is to compare the effects of three different anesthetic combinations on the electroretinogram in the same animals under similar laboratory conditions. Thiopental–isoflurane (TI), medetomidine–ketamine (MK), and xylazine–ketamine (XK) were used on each of 12 healthy miniature schnauzer dogs (MS) with a period of at least 3 weeks in between subsequent anesthesia protocols, using the Dog Standard Protocol. The scotopic ERGs consisted of scotopic low stimulus strength (S) responses designated S1, S2, S3, S4, and S5, at 1, 5, 10, 15, and 20 min after dark adaptation, respectively, and scotopic standard stimulus strength (S-ST) responses. The photopic ERGs consisted of a photopic single flash (P) response and 31 Hz flicker (P-FL) responses. For S-ST (2.5 cd s/m2), the amplitude of the a-wave using TI was significantly lower than that using MK (adjusted P = 0.05) and XK (adjusted P = 0.03), and the implicit time of the a-wave was significantly shorter than that using MK (adjusted P = 0.04). For P (2.5 cd s/m2), the amplitude of the b-wave using XK was significantly higher than that using MK (adjusted P = 0.01). The implicit times of the b-wave using TI was significantly longer and shorter than that of MK for S1, S2 and P-FL and for S4 and S-ST, respectively, and than that of XK for S2 and P-FL and for S5 and S-ST, respectively. The results of the present study showed that TI affected both the amplitude and the implicit time of the a-wave for S-ST and the implicit time of the b-wave relatively more so than was the case when using XK or MK. Therefore, it appears that either XK or MK could be advantageous to use rather than TI for clinical studies.  相似文献   
4.
5.
BACKGROUND: Caecal intubation is a necessary step in the complete endoscopic evaluation of the colon. Studies have estimated that experienced colonoscopists may fail to reach the caecum in up to 10% of cases. AIMS: To evaluate the utility of the double balloon enteroscope used for complete examination of the colon in patients with incomplete standard colonoscopy. PATIENTS: Twenty consecutive patients with incomplete colonoscopies within the Veterans Affairs Palo Alto Health Care System. Mean age of 66 years (S.D.+/-12 years, range 46-84), 16 men. METHODS: Prospective single-centre case series on the caecal intubation rate using standard double balloon enteroscope technique in patients with previous incomplete conventional colonoscopy. RESULTS: Use of the standard double balloon enteroscope technique permitted complete colonoscopy to be achieved in 95% of the patients (19/20). Seven patients (35%) had significant pathology beyond the extent of the prior incomplete colonoscopy. We performed endoscopic mucosal resection, polypectomy or biopsy. The mean time to reach the caecum was 28 min (S.D.+/-20 min, range 6-90 min). The sedation was similar to conventional colonoscopy. No complications occurred. CONCLUSIONS: The double balloon enteroscope technology and technique can be used to complete examination of the colon in patients who were referred because of incomplete standard colonoscopy.  相似文献   
6.
7.
Summary This study was carried out in order: (1) to examine the effects of isolated and combined prolonged exposures to noise and whole-body vibration on hearing, vision and subjectively experienced strain, and (2) to check the combined effects with repeated exposures. Six male subjects were exposed twice to noise (N) at 92 dBA, whole-body vibration (V) in the Z-axis at 4 Hz and 1.0 ms–2 rms, and noise and vibration (NV) for 90 min with each condition. Temporary threshold shifts of hearing (TTS) and their integrals (ITTS) were measured at 4, 6, 10, and 12 kHz. Visual acuity was examined by means of a very sensitive test. Cross-modality matching (CMM) of the handgrip force was used to judge the subjectively experienced strain. NV induced a clear tendency of higher TTS and ITTS than N, with several significant differences most pronounced at 10 kHz. With repeated exposures, the effect of NV decreased, while the reactions to N and V remained unchanged. The individual reactions to NV differed. The influence of the duration of exposures on vision depended on the condition; N caused time-dependent changes, whereas V did not. CMM-data increased with the duration of the exposure during V and NV. N was generally judged to be more straining than V; NV caused higher strain than V during the first 30 min of exposure only. Correlations between different effects suggest certain links between them. Additionally, less motivation — daily obtained by a questionnaire — often correlated with higher ITTS during N and NV. The results also illustrate the combined effects on the individual susceptibility, repetition of exposure, the kind of response, and, possibly, the actual psychic state.Abbreviations CMM cross-modality matching - MVC maximum voluntary contraction force - N exposure condition: noise level 92dBA, no whole-body vibration - NV exposure condition: combined exposure to noise with a level of 92 dBA and wholebody vibration with 4 Hz, 1 ms–2 rms - V exposure condition: whole-body vibration with 4 Hz, 1 ms–2 rms - TTS temporary threshold shift - ITTS integral of temporary threshold shift - WBV whole-body vibration in the common sense This work was done in the Temporary International Research Team on Combined Effects of Noise and Vibration of the Council of Mutual Economic Assistance of the Socialist Countries. The authors gratefully acknowledge the help and assistance of L.-M. Brumm, Y. Bening, M. Godau, G. Weber, and R. Vizcaino.  相似文献   
8.
JC virus (JCV) infection is regularly asymptomatic in healthy individuals. In contrast, in immunocompromised individuals, highly activated virus replication may lead to PML. Peripheral blood cells (PBCs) are found to habor JCV DNA in healthy and diseased individuals and it is discussed that they might be responsible for dissemination of the virus to the central nervous system (CNS) during persistence. To better understand the role of JCV DNA in PBCs for persistent infection and pathogenesis, the authors characterized the extent of JCV infection in Ficoll-gradient purified blood cells (peripheral blood mononuclear cells [PBMCs]) of healthy and human immunodeficiency virus type 1 (HIV-1)-infected individuals. Virus activation in PBMCs from healthy JCV-infected individuals was found at a rate of 0% to 38% at low polymerase chain reaction (PCR) sensitivity. In progressive multifocal leukoencephalopathy (PML) patients, a stronger signal was found, indicating increased virus activation. JCV DNA was regularly detected in T and B lymphocytes and in monocytes at low levels. However, granulocytes were shown to be the predominant reservoir of JCV DNA harboring high copy numbers. Although the overall distribution of viral genomes holds true for the population studied, in the individual, a markedly changed pattern of distribution can be found.  相似文献   
9.
This paper presents two unusual fistulae between the rectum and the lower urinary tract in adults, one a posttraumatic fistula following dilatation of a sigmoid colon stricture and the other a congenital anomaly. In both cases a contrast enema was negative; in one case a voiding cystourethrogram was negative. The fistula was demonstrated in case 1 by repeating the enema and having the patient raise his intraabdominal pressure, and in case 2 by having the patient hold while attempting to pass flatus during a cystogram, which demonstrated gas bubbles entering the bladder.  相似文献   
10.
We evaluated the efficacy of murine monoclonal antibodies (Mabs) targeted to beta/A4 amyloid for development of procedures for the in vivo identification of amyloid angiopathy (AA) in Alzheimer's disease (AD). Mabs to beta/A4 amyloid were prepared and screened for effectiveness in visualizing AA and senile plaques in postmortem AD brain sections. They were assessed again after enzymatic cleavage to produce Fab fragments and after labeling with 99mTc using a diamide dimercaptide ligand system. Modified and radiolabeled Fab fragments retained activity and specificity towards amyloid-laden blood vessels and senile plaques. A highly specific murine Mab, 10H3, was identified and characterized that fulfills criteria necessary for the development of a diagnostic imaging agent. Expansion and adaptation of these strategies may provide the methods and materials for the noninvasive analysis of AA in living patients, and permit assessment of the contribution of AA to the clinical and pathological features of AD.  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