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   187856篇
  免费   1589篇
  国内免费   96篇
耳鼻咽喉   1236篇
儿科学   6925篇
妇产科学   3217篇
基础医学   18247篇
口腔科学   1880篇
临床医学   13461篇
内科学   34236篇
皮肤病学   881篇
神经病学   17601篇
特种医学   9317篇
外科学   30564篇
综合类   2348篇
一般理论   4篇
预防医学   18662篇
眼科学   2911篇
药学   10141篇
中国医学   651篇
肿瘤学   17259篇
  2023年   102篇
  2022年   232篇
  2021年   376篇
  2020年   275篇
  2019年   322篇
  2018年   22244篇
  2017年   17585篇
  2016年   19773篇
  2015年   1274篇
  2014年   1317篇
  2013年   1425篇
  2012年   7986篇
  2011年   21968篇
  2010年   19370篇
  2009年   12011篇
  2008年   20302篇
  2007年   22517篇
  2006年   1361篇
  2005年   2967篇
  2004年   4112篇
  2003年   4951篇
  2002年   3055篇
  2001年   403篇
  2000年   513篇
  1999年   292篇
  1998年   317篇
  1997年   299篇
  1996年   187篇
  1995年   170篇
  1994年   160篇
  1993年   114篇
  1992年   101篇
  1991年   142篇
  1990年   171篇
  1989年   112篇
  1988年   85篇
  1987年   62篇
  1986年   49篇
  1985年   50篇
  1984年   55篇
  1983年   51篇
  1982年   49篇
  1981年   24篇
  1980年   53篇
  1974年   35篇
  1938年   60篇
  1937年   25篇
  1934年   30篇
  1932年   56篇
  1930年   48篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.

Background  

It has been observed that ras-transformed cell lines in culture have a higher phosphatidylcholine (PC) biosynthesis rate as well as higher PC-degradation rate (increased PC-turnover) than normal cells. In correspondence to these findings, the concentrations of the PC-degradation product lyso-phosphatidylcholine (LPC) in cancer patients were found to be decreased. Our objective was the systematic investigation of the relationship between LPC and inflammatory and nutritional parameters in cancer patients. Therefore, plasma LPC concentrations were assessed in 59 cancer patients and related to nutritional and inflammatory parameters. To determine LPC in blood plasma we developed and validated a HPTLC method.  相似文献   
105.
106.
The depth and extent of the invasion of the skull base by a tumor are the most critical information for successful en bloc resection of the tumor. The only means available for the evaluation of these factors are CT or MRI images. In order to clarify the ability of these imaging modes to delineate the invasion of the skull base, preoperative images of ten patients who underwent en bloc resection of skull base tumors at Kobe University Hospital were compared with the histopathological findings of the resected specimens. CT proved to be superior to MRI for evaluating bone destruction of the skull base. On the other hand, MRI provided more useful information about intracranial invasion than CT. As a hypertrophic linear shadow on Gd-enhanced MRI represented dural invasion or thickened dura mater adjacent to the tumor, this technique should be taken into consideration to determine the dural resection. We concluded that preoperative evaluation of the depth of skull base invasion by both CT and Gd-enhanced MRI is essential for planning complete tumor resection.  相似文献   
107.
108.
Summary To investigate the distribution of possible novel mutations from parkin gene in variant subset of patients with Parkinson’s disease (PD) in China and explore whether parkin gene plays an important role in the pathogenesis of PD, 70 patients were divided into early-onset group and late-onset group; 70 healthy subjects were included as controls. Genomic DNA from 70 normal controls and from those of PD patients were extracted from peripheral blood leukocytes by using standard procedures. Mutations of parkin gene (exon 1–12) in all the subjects were screened by PCR-single strand conformation polymorphism (SSCP), and further sequencing was performed in the samples with abnormal SSCP results, in order to confirm the mutation and its location. A new missense mutation Gly284Arg in a patient and 3 abnormal bands in SSCP electrophoresis from samples of another 3 patients were found. All the DNA variants were sourced from the samples of the patients with early-onset PD. It was concluded that Parkin point mutation also partially contributes to the development of early-onset Parkinson’s disease in Chinese. WANG Tao, male, born in 1961, Associate Professor This work was supported by grants from the key program of the special scientific project of Scientific & Technologic Agency of Hubei Province (Serial No. 2001AA308B01) and the Hygienic Research Project of Hygienic Agency of Hubei province (Serial No. WJ 01529).  相似文献   
109.
The content of dolichol, an isoprenoid present in all biological membranes, was determined in isolated sinusoidal liver cells after treatment of rats for 2 and 4 months with a low dosage of the hepatotoxin thioacetamide. The significant decrease in dolichol observed in hepatocytes after 2 months might be explained by peroxidation of the isoprenoid. At the same time point, retinol was retained, and decreased only after 4 months of treatment. After 4 months of treatment therefore both lipids decreased. In a subfraction of hepatic stellate cells, Ito-1 cells, the main storage site of vitamin A, dolichol decreased significantly only after 4 months. A remarkable difference from hepatocytes is that in Ito-1 cells retinol content significantly decreased after 2 months of treatment. In another subfraction, Ito-2 cells, the content of the two isoprenoids decreased in parallel. This heterogeneous subfraction might represent those transitional hepatic stellate cells that, while losing retinol, are in the process of differentiating into myofibroblasts secreting extracellular matrix components. In Kupffer cells and sinusoidal endothelial cells, impairment of dolichol might be observed later, only after 4 months of treatment, while retinol decreases uniformly over time. Starting after two months of treatment, the decrease of dolichol and the increase of retinol in hepatocytes, at the same time as retinol decreases in hepatic stellate cells, might be taken as an early index of incipient liver injury due to thioacetamide. This hypothesis is discussed with regard to a role of dolichol in the modulation of membrane fluidity for intracellular and intercellular retinol transport.  相似文献   
110.
The aim of this study was to evaluate the prognosis for surgically treated young patients with primary lung cancer, a prognosis generally considered to be very poor. Eighty-two patients less than 40 years of age were operated on at Marie-Lannelongue Hospital between 1982 and 1990. There were 72 male and 10 female patients. Ten patients (12%) had never smoked, whereas 48 patients (59%) had smoked for more than 20 pack-years. The lung cancer was asymptomatic in 27 patients (33%) and symptomatic in the others. Adenocarcinoma was found in 42% of the patients, epidermoid carcinoma in 28%, mixed cell carcinoma in 16%, small cell carcinoma in 8.5%, and undifferentiated large cell carcinoma in 6%. Among the 69 resected tumors, 22 were stage I, ten were stage II, 32 were stage IIIa, and five were stage IIIb. The resection was considered complete and curative in 56 patients (68%) and noncurative in 26 (32%) either because of an incomplete resection (12 in stage IIIa; 1 in stage IIIb) or because of an exploratory thoracotomy only (13). The overall actuarial 5-year survival rate was 41%, and the actuarial 5-year survival for patients who had a complete resection was 56%. The actuarial 5-year survival rates were as follows: patients in stage I, 70%; stage II, 54%; stage IIIa, 28%; stage IIIb, 0%; and patients having exploratory thoracotomy only, 18%. These survival rates are similar to those of patients older than 40 years with similar stages of disease.(ABSTRACT TRUNCATED AT 250 WORDS)  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