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   2251篇
  免费   125篇
  国内免费   7篇
耳鼻咽喉   6篇
儿科学   16篇
妇产科学   42篇
基础医学   247篇
口腔科学   76篇
临床医学   78篇
内科学   320篇
皮肤病学   2篇
神经病学   85篇
特种医学   344篇
外科学   301篇
综合类   5篇
预防医学   29篇
眼科学   110篇
药学   57篇
中国医学   2篇
肿瘤学   663篇
  2022年   10篇
  2021年   18篇
  2020年   9篇
  2019年   12篇
  2018年   20篇
  2017年   16篇
  2016年   35篇
  2015年   31篇
  2014年   42篇
  2013年   47篇
  2012年   88篇
  2011年   91篇
  2010年   58篇
  2009年   48篇
  2008年   101篇
  2007年   100篇
  2006年   95篇
  2005年   88篇
  2004年   104篇
  2003年   114篇
  2002年   120篇
  2001年   82篇
  2000年   94篇
  1999年   96篇
  1998年   42篇
  1997年   23篇
  1996年   33篇
  1995年   29篇
  1994年   37篇
  1993年   19篇
  1992年   76篇
  1991年   65篇
  1990年   73篇
  1989年   62篇
  1988年   55篇
  1987年   56篇
  1986年   40篇
  1985年   33篇
  1984年   22篇
  1983年   27篇
  1982年   13篇
  1981年   14篇
  1980年   14篇
  1979年   20篇
  1978年   10篇
  1977年   15篇
  1976年   12篇
  1974年   11篇
  1972年   8篇
  1971年   10篇
排序方式: 共有2383条查询结果,搜索用时 15 毫秒
91.
We report herein a rare case of diverticulitis causing a high serum level of carbohydrate antigen (CA) 19-9. A 52-year-old man was admitted to our hospital with lower abdominal pain. Laboratory data showed evidence of inflammation and a high serum level of CA 19-9 (370 U/ml). Computed tomography demonstrated thickening of the wall of the sigmoid colon. He was diagnosed as having diverticulitis of the sigmoid colon and was treated with antibiotics. Although his symptoms improved, the presence of a malignancy such as colorectal cancer could not be completely ruled out because of the persistently high serum level of CA19-9. A laparotomy was performed and the sigmoid colon was found to be adherent to the bladder. Under a diagnosis of diverticulitis, a sigmoidectomy was performed. Pathological examination revealed diverticulitis of the sigmoid colon, but there was no evidence of malignancy in the resected specimen. The serum CA19-9 level decreased to normal postoperatively and immunohistochemical staining revealed CA19-9 antigen in the cytoplasm of the diverticular epithelium. Therefore, a possible explanation for the high level of this tumor marker was diverticulitis of the sigmoid colon. Received: June 6, 2001 / Accepted: September 11, 2001  相似文献   
92.
PURPOSE: To elucidate the diurnal variation of human corneal curvature with regard to gender and menstrual cycle. METHODS: Changes in corneal curvature and intraocular pressure (IOP) were measured over 24 hours in 14 young adults using corneal topography and a non-contact tonometer. In study 1, seven males and seven females (after menses) were measured. In study 2, four females out of the seven volunteers who participated in study 1 were measured again during menses. RESULTS: The females after menses showed a remarkable diurnal variation throughout 24 hours. A significant difference between the light-wake periods and dark-sleep periods of 0.83 +/- 0.15 D was found (P < .01). Corneal curvature was significantly flatter during menses than after menses in the light-wake period (P < .05). In the males, no significant diurnal change (0.21 +/- 0.12 D) was measured in corneal curvature. CONCLUSIONS: Diurnal variation of corneal curvature was significant, approximately 0.83 D in young females after menses, and corneal curvature became flatter during menses in young females. Diurnal variation of corneal curvature is an important parameter for planning refractive surgery and contact lens wear.  相似文献   
93.
94.
Papillary adenocarcinoma of the stomach is a relatively uncommon histological type, and it is often detected in the early stage. We recently characterized the papillary type of gastric cancer and found frequent microsatellite instability and associated mutations. In this study we analyzed the centromere numerical abnormality (CNA) of 18 chromosomes (chromosomes 1-4, 6-12, 15-18, 20, X, and Y) in the papillary and papillotubular types of gastric cancer by a modified fluorescence in situ hybridization technique with microwave treatment. All 3 cases (100%) of papillary adenocarcinoma had high microsatellite instability (MSI-H), and low CNA, and 41% (7 cases) of the 17 cases of papillotubular adenocarcinoma exhibited MSI-H and all 7 cases had low CNA. Further 8 cases (47%) had extensive CNA. In these 15 cases, all the MSI-H cases had lower CNA, and low microsatellite instability (MSI-L) and MSS cases had higher CNA. The remaining two cases showed low CNA and MSI-L and MSS. These profiles were different from those of tubular type gastric cancer, which always had extensive CNA and no MSI. Although the numbers of the cases in this series are limited, our data may suggest that a modest CNA may be another characteristic of gastric cancer with papillary structure.  相似文献   
95.
A 37-year old male patient complained of lower back pain. Investigations revealed a retroperitoneal tumor and left-sided cervical lymphadenopathy without abnormal findings in both testicles. The diagnosis of extragonadal germ cell tumor was made based on a lymph node biopsy. Following chemotherapy and retroperitoneal lymphoadenectomy, at outpatient follow-up, beta-HCG elevated again. He complained of gross hematuria, cystoscopy showed a bladder tumor, and abdominal MRI scan showed a right ureteral tumor. Total cystectomy and right nephroureterectomy were performed, which revealed that the bladder and ureteral tumors were metastatic germ cell tumors. Six months later, the patient developed hepatic and mesenteric lymph node metastases that failed to respond to treatment, and died. Germ cell tumors metastasizing to the urinary tract are extremely uncommon, and this is the first report of bladder metastases, other than through direct invasion, from an extratesticular germ cell tumor.  相似文献   
96.
Identification of silencing of nine genes in human gastric cancers   总被引:12,自引:0,他引:12  
Aberrant methylations in human gastric cancers were searched for by a genome scanning technique, methylation-sensitive representational difference analysis. Nine CpG islands (CGIs) in the 5' regions of nine genes, LOX, HRASLS, bA305P22.2.3, FLNc (gamma-filamin/ABPL), HAND1, a homologue of RIKEN 2210016F16, FLJ32130, PGAR (HFARP/ANGPTL4/ARP4), and thrombomodulin, were found to be methylated in two gastric cancer cell lines, MKN28 and MKN74, but unmethylated in the normal sample. Their expressions were lost in the two cell lines, and the causal roles of the methylations in gene silencing were shown by treatment with 5-aza-2'-deoxycytidine. In 41 primary gastric cancers, methylations of these CGIs in association with reduced expressions were observed at high incidences (29-41%) for five genes, including LOX and HRASLS, which have been reported to have tumor-suppressive activities. The other four genes were methylated at low incidences (0-7%). By analysis of the numbers of aberrant methylations in individual cancers, a subset of cancers with high prevalence of aberrant methylations was identified, and all of the 11 cancers in the subset were diffuse type. To analyze the possible involvement of decreased fidelity of maintenance methylation in this subset of cancers, aberrant hypomethylations of three normally methylated CGIs were examined. Cancers with high prevalence of hypomethylations of normally methylated CGIs, however, constituted a different subset. It is expected that these nine genes may include important genes in gastric cancer development and would be useful to identify a distinct subset of gastric cancers.  相似文献   
97.
98.
We reviewed the current techniques and published results of balloon-occluded retrograde transvenous obliteration (B-RTO) for gastric varices (GV) and hepatic encephalopathy. The portal hemodynamics of gastric varices were classified into three types according to their feeding vessels, and the development of collateral veins under balloon occlusion of gastro-renal shunt was classified into five grades. The main draining veins of gastric varices were gastro-renal and gastro-inferior phrenic shunts. Preprocedural diagnosis of portal hemodynamics is important in selecting the technique for B-RTO. The rate of disappearance or marked reduction of GV was 98%, and the rate of recurrence of GV was 2%. Hepatic encephalopathy due to gastro-renal shunt improved markedly. In contrast, esophageal varices were aggravated at rates of 10% to 62.5% by the post-procedural elevation of portal pressure. Common adverse effects were hemoglobinuria, abdominal pain, and low-grade fever, but ascites and pleural effusion were also reported. Severe complications such as cardiogenic shock, atrial fibrillation, and pulmonary embolism were reported. We await technical improvements and further indications for this procedure.  相似文献   
99.
Involvement of prostaglandin E receptor subtype EP(4) in colon carcinogenesis.   总被引:16,自引:0,他引:16  
Accumulating evidence indicates that overproduction of prostanoids attributable to overexpression of cyclooxygenase-2 (COX-2) plays an important role in colon carcinogenesis. We have shown recently that the prostaglandin (PG) E receptor, EP(1), but not EP(3), is involved in mouse colon carcinogenesis. In line with our previous study, here we examined the role of prostanoid receptors in colon carcinogenesis using six additional lines of knockout mice deficient in prostanoid receptors EP(2), EP(4), DP, FP, IP, or TP. The animals were treated with the colon carcinogen, azoxymethane (AOM), and examined for the development of aberrant crypt foci (ACFs), putative preneoplastic lesions in the colon. Formation of ACFs was decreased only in the EP(4)-knockout mice, to 56% of the wild-type level. To confirm these results, we also examined the inhibitory effects of an EP(4)-selective antagonist, ONO-AE2-227, in the diet on the formation of AOM-induced colon ACFs in C57BL/6Cr mice and on the development of intestinal polyps in Min mice. ONO-AE2-227 at a dose of 400 ppm reduced the formation of ACFs to 67% of the control level, and intestinal polyp numbers in Min mice receiving 300 ppm were decreased to 69% of the control level. Plating efficiency assays showed that addition of 1.0 microM ONO-AE1-329, an EP(4)-selective agonist, resulted in a 1.8-fold increase in the colony number of the human colon cancer cell line, HCA-7, similar to the effect of PGE(2). Moreover, EP(4) mRNA expression was clearly observed in normal colon mucosa and colon tumors in mice. Our previous and present results indicate that PGE(2) contributes to colon carcinogenesis through its actions mediated through EP(1) and EP(4) receptors; therefore, antagonists for these two receptors may be good candidates as chemopreventive agents against colon cancer.  相似文献   
100.
Hypermethylation of the 5' upstream region (5' region) of the human p16(CDKN2A) (p16) gene is known to cause silencing, which is involved in a wide range of human cancers. For the rat p16 gene, its 5' region has not been cloned, and it is uncertain whether surrogate use of exon 1 alpha is adequate for analysis of p16 silencing. In this study, we observed that methylation analysis of exon 1 alpha gave false positive results in three samples of normal rat mammary epithelia and in two of six primary mammary carcinomas. Therefore, we determined the nucleotide sequence of the 5' region of the rat p16 gene. To confirm that methylation status of the 5' region is correlated with p16 expression, the methylation status was analyzed by bisulfite sequencing and methylation-specific PCR in three samples of normal mammary glands, six samples of mammary carcinomas and four cell lines. The 5' region was demethylated in all of the three normal and six carcinoma samples that fully expressed p16. On the other hand, the 5' region was highly methylated in the 3Y1 cell line, which lacked p16 expression, but without deletion. These results showed that the methylation status of the 5' region was more closely correlated with p16 expression than that of the exon 1 alpha and analysis of the methylation status is useful in examining p16 silencing in various rat tumors.  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