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   192458篇
  免费   2182篇
  国内免费   55篇
耳鼻咽喉   1273篇
儿科学   7280篇
妇产科学   3562篇
基础医学   18560篇
口腔科学   1737篇
临床医学   15072篇
内科学   33946篇
皮肤病学   901篇
神经病学   17807篇
特种医学   9177篇
外国民族医学   1篇
外科学   30083篇
综合类   2878篇
一般理论   37篇
预防医学   20717篇
眼科学   3051篇
药学   10343篇
中国医学   641篇
肿瘤学   17629篇
  2023年   114篇
  2022年   230篇
  2021年   509篇
  2020年   297篇
  2019年   494篇
  2018年   22394篇
  2017年   17651篇
  2016年   19830篇
  2015年   1360篇
  2014年   1390篇
  2013年   1709篇
  2012年   8242篇
  2011年   22288篇
  2010年   19453篇
  2009年   12161篇
  2008年   20474篇
  2007年   22768篇
  2006年   1614篇
  2005年   3226篇
  2004年   4435篇
  2003年   5337篇
  2002年   3435篇
  2001年   387篇
  2000年   504篇
  1999年   289篇
  1998年   399篇
  1997年   385篇
  1996年   263篇
  1995年   262篇
  1994年   227篇
  1993年   171篇
  1992年   113篇
  1991年   153篇
  1990年   200篇
  1989年   145篇
  1988年   126篇
  1987年   88篇
  1986年   84篇
  1985年   90篇
  1984年   89篇
  1983年   92篇
  1982年   96篇
  1981年   86篇
  1980年   115篇
  1979年   65篇
  1978年   56篇
  1976年   54篇
  1974年   58篇
  1938年   63篇
  1932年   56篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.

Background and objectives

A prompt and effective management of trauma patient is necessary. The aim of this case report is to highlight the importance of intraoperative echocardiography as a useful tool in patients suffering from refractory hemodynamic instability no otherwise explained.

Case report

A 41 year‐old woman suffered a car accident. At the emergency department, no abnormalities were found in ECG or chest X‐ray. Abdominal ultrasound revealed the presence of abdominal free liquid and the patient was submitted to urgent exploratory laparotomy. Nevertheless, she persisted suffering arterial hypotension and metabolic acidosis. Looking for the reason of her hemodynamic instability, intraoperative transthoracic echocardiography was performed, finding out the presence of pericardial effusion. Once the cardiac surgeon extracted pericardial clots, patient's situation improved clinically and analytically.

Conclusion

Every anesthesiologist should be able to use the intraoperative echocardiography as an effective tool in order to establish the appropriate measures to promote the survival of patients suffering severe trauma.  相似文献   
4.
Magnetic field generated by neuronal activity could alter magnetic resonance imaging (MRI) signals but detection of such signal is under debate. Previous researches proposed that magnitude signal change is below current detectable level, but phase signal change (PSC) may be measurable with current MRI systems. Optimal imaging parameters like echo time, voxel size and external field direction, could increase the probability of detection of this small signal change. We simulate a voxel of cortical column to determine effect of such parameters on PSC signal. We extended a laminar network model for somatosensory cortex to find neuronal current in each segment of pyramidal neurons (PN). 60,000 PNs of simulated network were positioned randomly in a voxel. Biot–savart law applied to calculate neuronal magnetic field and additional phase. The procedure repeated for eleven neuronal arrangements in the voxel. PSC signal variation with the echo time and voxel size was assessed. The simulated results show that PSC signal increases with echo time, especially 100/80 ms after stimulus for gradient echo/spin echo sequence. It can be up to 0.1 mrad for echo time = 175 ms and voxel size = 1.48 × 1.48 × 2.18 mm3. With echo time less than 25 ms after stimulus, it was just acquired effects of physiological noise on PSC signal. The absolute value of the signal increased with decrease of voxel size, but its components had complex variation. External field orthogonal to local surface of cortex maximizes the signal. Expected PSC signal for tactile detection in the somatosensory cortex increase with echo time and have no oscillation.  相似文献   
5.
6.
7.
ABSTRACT

Measuring hope reliably and accurately remains an important research objective, not least in less prosperous settings where ‘holding on to hope’ may be critically important in the struggle against adverse life conditions. The State Hope Scale was designed for use in the US. Despite reported application in diverse cultures and using translations the scale has not been extensively validated outside US populations. This study contributes to a larger project exploring the measurement of hope and provides a critique of Snyder’s scale as used in a Tanzanian female population of 1021 urban microfinance participants. We evaluate the scale’s validity through assessment of the empirical distribution of scores, item response profiles, internal consistency and discriminatory ability. Participants mostly scored very high and many reached very near the maximum attainable score. Hardly any endorsed the negative half of the response scale. Several problems are discussed including poor discrimination and strong evidence of acquiescence response bias. We also found little association of the scale scores with hypothesised correlates of hope. Future improvements on the measurement of hope are recommended, especially in studies outside the narrow Western context in which the scale was devised.  相似文献   
8.
ABSTRACT

This work collates data from the analysis of complex mixtures analysed in STRmix during routine no-suspect volume crime work. It interrogates the upload rate for these types of mixtures and which component of the profile has been able to be interpreted for upload. The number of profiles giving multiple uploads and the amount of replicate PCR analysis has been collated.  相似文献   
9.
10.
Farnesyltransferase (FTase) is one of the prenyltransferase family enzymes that catalyse the transfer of 15-membered isoprenoid (farnesyl) moiety to the cysteine of CAAX motif-containing proteins including Rho and Ras family of G proteins. Inhibitors of FTase act as drugs for cancer, malaria, progeria and other diseases. In the present investigation, we have developed two structure-based pharmacophore models from protein–ligand complex (3E33 and 3E37) obtained from the protein data bank. Molecular dynamics (MD) simulations were performed on the complexes, and different conformers of the same complex were generated. These conformers were undergone protein–ligand interaction fingerprint (PLIF) analysis, and the fingerprint bits have been used for structure-based pharmacophore model development. The PLIF results showed that Lys164, Tyr166, TrpB106 and TyrB361 are the major interacting residues in both the complexes. The RMSD and RMSF analyses on the MD-simulated systems showed that the absence of FPP in the complex 3E37 has significant effect in the conformational changes of the ligands. During this conformational change, some interactions between the protein and the ligands are lost, but regained after some simulations (after 2 ns). The structure-based pharmacophore models showed that the hydrophobic and acceptor contours are predominantly present in the models. The pharmacophore models were validated using reference compounds, which significantly identified as HITs with smaller RMSD values. The developed structure-based pharmacophore models are significant, and the methodology used in this study is novel from the existing methods (the original X-ray crystallographic coordination of the ligands is used for the model building). In our study, along with the original coordination of the ligand, different conformers of the same complex (protein–ligand) are used. It concluded that the developed methodology is significant for the virtual screening of novel molecules on different targets.  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