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   8981篇
  免费   431篇
  国内免费   98篇
耳鼻咽喉   176篇
儿科学   145篇
妇产科学   87篇
基础医学   1683篇
口腔科学   132篇
临床医学   817篇
内科学   1748篇
皮肤病学   204篇
神经病学   552篇
特种医学   503篇
外科学   1108篇
综合类   22篇
一般理论   2篇
预防医学   337篇
眼科学   254篇
药学   876篇
中国医学   92篇
肿瘤学   772篇
  2024年   3篇
  2023年   63篇
  2022年   242篇
  2021年   359篇
  2020年   181篇
  2019年   205篇
  2018年   268篇
  2017年   209篇
  2016年   259篇
  2015年   407篇
  2014年   518篇
  2013年   554篇
  2012年   788篇
  2011年   761篇
  2010年   451篇
  2009年   394篇
  2008年   539篇
  2007年   568篇
  2006年   497篇
  2005年   436篇
  2004年   315篇
  2003年   290篇
  2002年   229篇
  2001年   200篇
  2000年   199篇
  1999年   171篇
  1998年   45篇
  1997年   38篇
  1996年   25篇
  1995年   18篇
  1994年   19篇
  1993年   27篇
  1992年   34篇
  1991年   28篇
  1990年   26篇
  1989年   22篇
  1988年   16篇
  1987年   22篇
  1986年   15篇
  1985年   12篇
  1984年   4篇
  1983年   6篇
  1982年   5篇
  1979年   6篇
  1978年   6篇
  1977年   4篇
  1976年   3篇
  1975年   3篇
  1970年   3篇
  1968年   4篇
排序方式: 共有9510条查询结果,搜索用时 15 毫秒
11.
The aim of this study was to investigate the potential of a composite matrix, containing esterified hyaluronic acid and gelatin, to facilitate the osteochondral differentiation of culture-expanded, bone marrow-derived mesenchymal progenitor cells. The cell loading characteristics and the effects of the matrix on cell differentiation were examined in vitro and in vivo. Empty and cell-loaded composites were cultivated for up to 28 days in a chemically defined medium with or without transforming growth factor-beta1 (TGF-beta1). A type II collagen-rich extracellular matrix was produced by cells loaded in the matrix and cultured in the presence of TGF-beta1. Empty and cell-loaded matrices were also implanted subcutaneously in immunodeficient mice. Three types of implant were used: empty (group I), cell-loaded matrices (Group II), and cell-loaded matrices cultured for 14 days in vitro in defined medium with TGF-beta1 (group III). No osteochondral differentiation was found in implanted empty matrices; however, the matrix supported osteochondrogenic cell differentiation in the cell-loaded implants. Preculture in vitro in a chondrogenic medium increased the percentage of osteochondral tissue found in the constructs after 3 weeks. These results indicate the potential use of this composite matrix for delivery of bone marrow-derived mesenchymal progenitor cells for the repair of chondral and osseous defects. The results also indicate that this composite matrix is useful for in vitro tissue engineering.  相似文献   
12.
13.
Contrast enhancement during the dynamic MR imaging is important for the detection and characterization of focal liver lesions. The purpose of this study was to determine whether or not a timing examination with a injection of a 1.0-mL bolus of gadopentetate dimeglumine into the antecubital vein followed by rapid dynamic scanning and measurement of signal intensity of the aorta could help to obtain proper arterial-dominant phase images for the characterization of focal hepatic lesions during subsequent multiphase dynamic MR imaging. The imaging delay to acquisition of the first gadolinium-enhanced image for multiphase dynamic MR imaging was set to equal the time to peak aortic enhancement during the test examination. The first contrast-enhanced images of 80 patients with 160 focal liver lesions (hepatocellular carcinoma, n = 79; cavernous hemangioma, n = 51; metastatic tumor, n = 30) were then retrospectively reviewed. Peak aortic enhancement occurred between 10 and 28 seconds (mean, 16.5 seconds +/- 3.1) after starting the infusion of contrast material in 80 patients during the test-examination. Depending on the findings of intrahepatic vascular enhancement on the full-scale dynamic images, hepatic arterial phase (n = 11, 14%) or sinusoid phase (n = 65, 81%) imaging was obtained during the first gadolinium-enhanced acquisition in 76 (95%) of 80 patients. Three different lesions were well characterized and easily distinguished from each other (p < .0001) on the first-phase images depending on their enhancement pattern. In the majority of patients, timing examination with test-bolus injection was helpful in obtaining qualified images for the characterization of various focal lesions.  相似文献   
14.
Five hundred allergy clinic patients were prick skin tested with papain, 1 mg/mL, in addition to usual local aeroallergens. Five of 475 subjects with seasonal allergic disease had positive skin tests to both papain and local pollens. None of the 25 individuals with negative skin test to pollens had skin reactivity to papain. The five subjects with positive skin tests to papain underwent double-blind placebo-papain challenges. All papain challenges were positive. Placebo challenges were negative. Papain-induced symptoms included palatal itching, watering itchy eyes, sneezing, rhinorrhea, abdominal cramps, diarrhea, and diaphoresis. Circulating papain-specific IgE was detected in all the papain-sensitive individuals, but not in control subjects. Confirmed papain sensitivity occurred in 1.05% of allergic subjects. In the papain-sensitive patients, cross-reacting antibodies with chymopapain were found. The small number of non-allergic subjects did not show any papain or chymopapain sensitivity in vitro.  相似文献   
15.
Radiologic findings of Mirizzi syndrome with emphasis on MRI   总被引:6,自引:0,他引:6  
We have reported a case of Mirizzi syndrome preoperatively diagnosed using MR cholangiopancreatography. MRCP and T2-weighted image using a single-shot fast spin-echo sequence accurately depicted all components of Mirizzi syndrome, including impacted stone in the neck of the gallbladder compressing the common hepatic duct and wall-thickening of the gallbladder without any evidence of malignancy. The combination of MRCP and T2-weighted image can be counted on to replace conventional modalities of diagnosing Mirizzi syndrome without any loss of diagnostic accuracy.  相似文献   
16.
A patient complying with the clinical criteria for brain death was studied by preenhanced computed tomography (CT). Preenhanced CT showed apparent increased density at the base of the brain along the course of the major arterial vessels, and abnormally dense-appearing deep venous structures, like those of contrast-enhanced CT. There was a diffuse decrease in brain density with a poorly delineated ventricular system. These CT findings were very characteristic. CT as a non-invasive method seems to be valuable in the diagnosis of brain death. The relevant literature is reviewed and mechanisms showing those CT findings are discussed.  相似文献   
17.
Reaction of diene alcohol5 and maleic anhydride in benzene at either room temperature or reflux proceeds probably through a intermolecular Diels-Alder cycloaddition followed by lactone formation to give adduct6.  相似文献   
18.
BackgroudOutcomes of traditional treatment for osteonecrosis of the femoral head (ONFH) are not always satisfactory. Hence, cell-supplementation therapy has been attempted to facilitate necrotic-tissue regeneration. Adipose-derived mesenchymal stem cell (ADMSC) transplantation is potentially advantageous over bone marrow-derived MSC implantation, but its outcomes for ONFH remain unclear. The aim of this study was to determine 2-year radiological and clinical outcomes of culture-expanded autologous ADMSC implantation for ONFH.MethodsEighteen hips with necrotic lesions involving ≥ 30% of the femoral head were included. ADMSCs were harvested by liposuction and culture expanded for 3 passages over 3 weeks. With a 6-mm single drilling, ADMSCs were implanted into the necrotic zone. All patients underwent magnetic resonance imaging (MRI), single-photon emission computed tomography/computed tomography (SPECT/CT) at screening and 6 months, 12 months, and 24 months postoperatively. The primary outcome was the change in the size of necrotic area on MRI. Secondary outcomes were changes in clinical scores and radioisotope uptake on SPECT/CT. Conversion total hip arthroplasty (THA) was defined as the endpoint.ResultsPreoperatively, the necrotic lesion extent was 63.0% (38.4%–96.7%) of the femoral head. The mean Harris hip score was 89.2, the University of California at Los Angeles (UCLA) score was 5.6, and Western Ontario and McMaster Universities Arthritis index (WOMAC) was 79.4. Three patients underwent THA and 1 patient died in an accident. Finally, 11 patients (14 hips) were available for ≥ 2-year follow-up. At the last follow-up, no surgery-related complications occurred, and 14 of 17 hips (82%) were able to perform daily activities without THA requirement. There was no significant decrease in lesion size between any 2 intervals on MRI. However, widening of high signal intensity bands on T2-weighted images inside the necrotic lesion was observed in 9 of 14 hips (64%); 11 of 14 hips (79%) showed increased vascularity on SPECT/CT at 2 years postoperatively. No significant differences were observed between preoperative and 24-month mean Harris hip score (89.2 vs. 88.6), WOMAC (79.4 vs. 75.7), and UCLA score (5.6 vs. 6.2).ConclusionsOur outcomes suggest that culture-expanded ADMSC implantation is a viable option for ONFH treatment without adverse events.  相似文献   
19.
Six flavonoids were isolated from the aerial parts ofCirsium rhinoceros. The flavonoids were identified as apigenin, luteolin, pectolinarigenin-7-O-β-D-glucopyranoside, linarin, pectolinarin and hispidulin-7-O-α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranoside on the basis of chemical and spectral evidence.  相似文献   
20.
Transfer of extensor carpi radialis longus or brevis for opponensplasty   总被引:4,自引:0,他引:4  
For the restoration of thumb opposition many types of tendon transfer techniques have been described. The flexor digitorum superficialis (FDS) of the ring finger is commonly selected as a motor. On occasion, however, the quality of the flexor muscles of the fingers or wrist is not good enough for tendon transfer and another available muscle must be selected. In this situation, we have preferred to use an extensor carpi radialis longus (ECRL) or brevis (ECRB) transfer to restore opposition of the thumb. Follow-up examination, at an average 5 years and 10 months after operation, showed that the results of ten of 11 transfers were excellent and the other was good.  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