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   208047篇
  免费   3981篇
  国内免费   1783篇
耳鼻咽喉   1681篇
儿科学   7093篇
妇产科学   3798篇
基础医学   20349篇
口腔科学   2089篇
临床医学   16179篇
内科学   36302篇
皮肤病学   1453篇
神经病学   18147篇
特种医学   10028篇
外国民族医学   17篇
外科学   32110篇
综合类   6509篇
现状与发展   4篇
一般理论   7篇
预防医学   20164篇
眼科学   3489篇
药学   12861篇
  21篇
中国医学   2260篇
肿瘤学   19250篇
  2023年   422篇
  2022年   555篇
  2021年   1318篇
  2020年   1105篇
  2019年   1170篇
  2018年   23064篇
  2017年   18333篇
  2016年   20449篇
  2015年   2410篇
  2014年   2647篇
  2013年   2601篇
  2012年   9497篇
  2011年   23612篇
  2010年   20466篇
  2009年   12751篇
  2008年   21253篇
  2007年   23373篇
  2006年   2308篇
  2005年   3895篇
  2004年   4612篇
  2003年   5521篇
  2002年   3498篇
  2001年   1149篇
  2000年   1215篇
  1999年   894篇
  1998年   631篇
  1997年   594篇
  1996年   412篇
  1995年   401篇
  1994年   366篇
  1993年   252篇
  1992年   361篇
  1991年   365篇
  1990年   338篇
  1989年   244篇
  1988年   242篇
  1987年   188篇
  1986年   144篇
  1985年   145篇
  1984年   102篇
  1983年   64篇
  1982年   49篇
  1981年   34篇
  1980年   60篇
  1979年   34篇
  1974年   33篇
  1970年   36篇
  1938年   63篇
  1932年   57篇
  1930年   46篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
Abstract

Background

Latent tuberculosis infection (LTBI) is a huge reservoir for the deadlier TB disease. Accurate identification of LTBI is a key strategy to eliminate TB. Therefore, a systematic review and meta-analysis approach was used to assess diagnostic potential of IL-2 for LTBI.  相似文献   
103.
Cognitive pharmacy trials seek to identify interventions that benefit patients. The potential benefits of an intervention are primarily evaluated by outcome measures. The question then is: What is the optimal outcome measure? Unfortunately, the question remains unsolved. Several factors must be taken into consideration when conducting outcome research—particularly within cognitive pharmacy trials. The interventions are often complex and non-specific, and seek to improve symptom control, optimise the use of medications and reduce medication-related risks. “Hard” endpoints, such as mortality and hospital admissions, may not be the optimal outcome measures, since cognitive pharmacy interventions are unlikely to result in changes in these measures. Instead, adverse drug events or “soft” endpoints, such as quality of life, drug-related problems and patient satisfaction may be appropriate choices of outcome measures. Finally, it is not only outcome measures that may pose a challenge when conducting outcome research; other essential components include study design, type of intervention, the patient population, etc.  相似文献   
104.
Spigelian hernias, also called as lateral ventral hernias, are rare hernias to present themselves in clinical practice. The significance of these hernias lies in the fact that they are commonly intraparietal hernias and are, hence, difficult to diagnose clinically. Moreover, the neck of these hernias is usually small, posing a fair risk of strangulation. With the advancement in laparoscopic hernia repair, there is evidence that Spigelian hernias too can be repaired laparoscopically, thereby causing less morbidity and shorter hospital stay. Here, we present a rare case of large Spigelian hernia that posed to us as a diagnostic dilemma. The symptoms, clinical findings, and ultrasound of the patient were not specific, and a CT scan had to be used as the measure to confirm the diagnosis. The patient was then managed successfully with laparoscopic intraperitoneal onlay mesh repair. The details of the case and a brief discussion are included.  相似文献   
105.
Direct peroral cholangioscopy (POC) using an ultra‐slim upper endoscope is one modality of POC for intraductal endoscopic evaluation and treatment of the bile duct. Choledochoduodenostomy (CDS) is one modality of biliary bypass surgery that provides a new route to the bile duct. We carried out direct POC using an ultra‐slim upper endoscope without the use of accessories in 10 patients (four sump syndromes, three bile duct strictures and three intrahepatic duct stones) previously undergoing surgical CDS. Direct POC was successful in all patients. The use of an intraductal balloon catheter was required in one patient for advancement of the endoscope into the bile duct. Distal bile ducts with sump syndromes were cleared using baskets and water irrigation under direct POC. Cholangiocarcinoma was diagnosed in one patient with hilar bile duct stricture after cholangioscopic evaluation and a targeting forceps biopsy under direct POC. Intrahepatic duct stones were successfully extracted after intraductal fragmentation under direct POC. Oozing bleeding occurred during intraductal lithotripsy but stopped spontaneously. Direct POC using an ultra‐slim upper endoscope without the assistance of accessories can easily be carried out in patients undergoing CDS.  相似文献   
106.
This study investigated the hypocholesterolaemic effects of bitter melon aqueous extracts (BMAE) in vitro, the inhibitory effects of BMAE on pancreatic cholesterol esterase (CEase) and incorporation of cholesterol into micelles were investigated. BMAE decreased the in vitro micellar solubility of cholesterol in a dose-dependent manner. The conformation of CEase was investigated by means of circular dichroism (CD) and fluorescence. The result revealed the decrease of α-helix contents, increase of β-sheet and exposure of aromatic amino acid residuals. The incorporation of cholesterol into micelles was inhibited by BMAE. A complex was observed by transmission electron microscopy (TEM), which indicated interaction between cholesterol and BMAE. The result revealed that BMAE can play a role in decreased intestinal cholesterol absorption via inhibition of CEase, and of micelle formation.  相似文献   
107.
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   
108.
109.
The distribution patterns of perfluorinated compounds (PFCs) in the surface waters of Xixi wetland, China, were investigated for the first time. Among the eight PFCs investigated, only perfluorooctanoic acid (PFOA), perfluoroheptanoic acid (PFHpA) and perfluorononanoic acid (PFNA) were detected. PFOA was the most prominent PFC, and detected in all of the samples with higher PFOA concentrations (maximum: 197.8 ng L?1), followed by PFHpA (maximum: 3.97 ng L?1). Geographical differences in PFC levels were not observed among various sampling locations except for the YanShan River location, but seasonal changes have been observed for PFOA. The study suggested that the water diversion project from the Qiantang River to the Xixi Wetland may have significantly contributed to the increase of PFOA level, and that domestic sewage and farmland irrigation runoff are constant pollution sources to the Xixi Wetland.  相似文献   
110.
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