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   3175篇
  免费   144篇
  国内免费   18篇
耳鼻咽喉   7篇
儿科学   27篇
妇产科学   18篇
基础医学   396篇
口腔科学   47篇
临床医学   218篇
内科学   751篇
皮肤病学   206篇
神经病学   155篇
特种医学   451篇
外科学   432篇
综合类   12篇
预防医学   45篇
眼科学   11篇
药学   138篇
中国医学   8篇
肿瘤学   415篇
  2023年   13篇
  2022年   30篇
  2021年   56篇
  2020年   39篇
  2019年   48篇
  2018年   62篇
  2017年   60篇
  2016年   82篇
  2015年   83篇
  2014年   122篇
  2013年   139篇
  2012年   177篇
  2011年   237篇
  2010年   117篇
  2009年   89篇
  2008年   191篇
  2007年   240篇
  2006年   216篇
  2005年   219篇
  2004年   213篇
  2003年   212篇
  2002年   192篇
  2001年   60篇
  2000年   37篇
  1999年   40篇
  1998年   35篇
  1997年   43篇
  1996年   40篇
  1995年   29篇
  1994年   24篇
  1993年   23篇
  1992年   24篇
  1991年   17篇
  1990年   13篇
  1989年   23篇
  1988年   11篇
  1987年   8篇
  1986年   11篇
  1985年   9篇
  1984年   12篇
  1983年   8篇
  1982年   7篇
  1981年   7篇
  1980年   5篇
  1979年   2篇
  1978年   2篇
  1977年   3篇
  1976年   3篇
  1974年   1篇
  1972年   1篇
排序方式: 共有3337条查询结果,搜索用时 15 毫秒
51.
Systemic sclerosis (SSc) is an autoimmune systemic connective tissue disorder characterized by sclerotic change of the skin and multiple internal organs. Although the pathogenesis of this disorder is still unknown, overproduction of extracellular matrix proteins, including collagens and fibronectin, and aberrant immune activation may be involved in the mechanism. Interleukin (IL)‐1 is one of the key regulators of inflammatory response. IL‐1 is also involved in regulating connective tissue remodeling and cellular differentiation of epithelial and ectodermal cells. There are three major members of the IL‐1 family: IL‐1α, IL‐1β and IL‐1 receptor antagonist. IL‐1α was first described as a factor derived from keratinocytes that stimulates thymocyte proliferation. IL‐1α plays a crucial role in procollagen production by fibroblasts derived from patients with SSc. The present study was undertaken to investigate the serum levels of IL‐1α in patients with SSc. Serum samples were obtained from 66 Japanese patients with SSc and 19 healthy controls. Levels of serum IL‐1α were measured with a specific enzyme‐linked immunoassay kit. Mean serum levels were significantly higher in SSc patients than in those healthy control subjects. Moreover, contracture of phalanges was found at a significantly lower prevalence in SSc patients with elevated serum IL‐1α levels than those with normal levels. These results suggest that IL‐1α may play a role in the pathogenesis of SSc.  相似文献   
52.
53.
Glycogen storage disease type Ia (GSD-Ia; von Gierke disease) is an inherited disorder caused by glucose-6-phosphatase deficiency, and there have been some reports of hepatic tumors in patients with this disease. We report two patients with benign hepatic tumors with GSD-Ia. One is a 19-year-old man who underwent segmentectomy 4 for a focal nodular hyperplasia, and the other is a 31-year-old woman who underwent segmentectomies 3, 5, and 6 for hepatic adenomas. Two significant perioperative complications, resulting from the carbohydrate metabolic disorders, hypoglycemia and metabolic acidosis, occurred in both patients. We managed the metabolic complications successfully by administering a sufficient volume of glucose intravenously. Close perioperative monitoring of blood glucose and lactate concentrations is essential in the perioperative management of patients with GSD-Ia. The intravenous administration of glucose, starting with a smaller dose and then increasing the dose, is adequate management for lactic acidosis with or without hypoglycemia during the perioperative period.  相似文献   
54.
BACKGROUND: We developed a method for reorganizing the mouse small intestine. In the present study, we investigated whether the reorganized small intestine was morphologically and histochemically differentiated. We also evaluated the reorganized small intestine as an in vitro wound healing model. METHODS: Fetal mouse small intestines were dispersed into single cells, which were then cultured to a high density. Newly formed small intestine-like organs on a membrane filter were observed by light and electron microscopy. Alkaline phosphatase (ALPase) activity of the epithelium was analyzed. To evaluate the reorganized small intestine as an in vitro wound healing model, a scalpel was used to cut the reorganized intestine on a membrane, and the healing process was morphologically and immunohistochemically examined. RESULTS: After 6 days in culture, the surface was almost completely coveed with epithelial cells, and villus-like structures were observed. These epithelial cells formed microvilli, and in parallel with this development, ALPase activity of the microvilli increased (from day 4). Twenty-four hours after the cutting, the wound surface was almost completely covered with undifferentiated epithelial cells. The number of acetylated low-density lipoprotein labeled with 1,1,dioctadecyll,3,3,3,3, tetramethyl-indocarbocyanine perchlorate (DiI-Ac-LDL)-positive macrophages increased after cutting. Platelet-derived growth factor (PDGF)-, basic fibroblast growth factor (bFGF)-, matrix metalloproteinase-1 (MMP-1)-positive cells were detected by immunohistochemical staining. CONCLUSIONS: The reorganized small intestine had a morphologically and histochemically differentiated organoid structure, and was useful as an in vitro model for investigating the process of wound healing.  相似文献   
55.
The effect of selectively decreasing renal angiotensin II type 1 (AT1) receptor expression on renal function and blood pressure has not been determined. Therefore, we studied the consequences of selective renal inhibition of AT1 receptor expression in normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) in vivo. Vehicle, AT1 receptor antisense oligodeoxynucleotides (AS-ODN), or scrambled oligodeoxynucleotides were infused chronically into the cortex of the remaining kidney of conscious, uninephrectomized WKY and SHR on a 4% NaCl intake. Basal renal cortical membrane AT1 receptor protein was greater in SHR than in WKY. In WKY and SHR, AS-ODN decreased renal but not cardiac AT1 receptors. AT1 receptor AS-ODN treatment increased plasma renin activity to a greater extent in WKY than in SHR. However, plasma angiotensin II and aldosterone were increased by AS-ODN to a similar degree in both rat strains. In SHR, sodium excretion was increased and sodium balance was decreased by AS-ODN but had only a transient ameliorating effect on blood pressure. Urinary protein and glomerular sclerosis were markedly reduced by AS-ODN-treated SHR. In WKY, AS-ODN had no effect on sodium excretion, blood pressure, or renal histology but also modestly decreased proteinuria. The major consequence of decreasing renal AT1 receptor protein in the SHR is a decrease in proteinuria, probably as a result of the amelioration in glomerular pathology but independent of systemic blood pressure and circulating angiotensin II levels.  相似文献   
56.
Macrophage inflammatory protein (MIP)-1alpha and MIP-1beta have been identified as candidates for multiple myeloma (MM)-derived bone-resorbing factors. To validate the clinical relevance of these observations, we investigated correlations between the ability of MM cells to secrete these chemokines and the extent of MM bone lesions as well as levels of biochemical bone markers in patients with MM. Patients with multiple bone lesions exhibited higher MIP-1alpha and MIP-1beta secretion from MM cells along with elevated urinary deoxypyridinoline (Dpd), without significant elevation of serum bone-specific alkaline phosphatase (BALP) or osteocalcin compared with those with minimal bone lesions. MIP-1alpha and MIP-1beta levels correlated positively with urinary Dpd and serum BALP but not with serum osteocalcin. These results provide further evidence for a causal role of MIP-1alpha and MIP-1beta in the development of lytic bone lesions, and suggest that MM cells suppress osteoblastic bone formation to cause an imbalance of bone turnover and development of destructive bone lesions.  相似文献   
57.
It is well known that sex steroids play important roles in the development of invasive ductal carcinoma (IDC) of the human breast. However, biological significance of sex steroids remains largely unclear in ductal carcinoma in situ (DCIS), regarded as a precursor lesion of IDC, which is partly due to the fact that the intratumoral concentration of sex steroids has not been examined in DCIS. Therefore, in this study, we first examined the intratumoral concentrations of estradiol and 5alpha-dihydrotestosterone (DHT) using liquid chromatography/electrospray tandem mass spectrometry in DCIS. Intratumoral concentrations of both estradiol and DHT were threefold higher in DCIS than non-neoplastic breast tissues and estrogen-producing enzymes (aromatase, steroid sulfatase, and 17beta-hydroxysteroid dehydrogenase type 1 (17betaHSD1)), and androgen-producing enzymes (17betaHSD5 and 5alpha-reductase type 1 (5alphaRed1)) were abundantly expressed in DCIS by real-time PCR and immunohistochemical analyses. The intratumoral concentration of DHT was significantly lower in IDC than DCIS, while the expression of aromatase mRNA in carcinoma cells and intratumoral stromal cells was significantly higher in IDC than those in DCIS. Immunohistochemistry for sex steroid-producing enzymes in DCIS demonstrated that 5alphaRed1 immunoreactivity was positively correlated with Ki-67 labeling index and histological grade and was also associated with an increased risk of recurrence in patients with DCIS examined. Results of our study suggest that intratumoral concentrations of estradiol and DHT are increased in DCIS, which is possibly due to intratumoral production of these steroids. Therefore, estradiol and DHT may play important roles in the development of DCIS of the human breast.  相似文献   
58.
In human endometriotic stromal cells, markedly high levels of aromatase P450 (P450arom) mRNA and promoter II activity are present and can be vigorously stimulated by PGE(2) via a cAMP-dependent pathway to give rise to physiologically significant estrogen biosynthesis. Stromal cells of eutopic endometrium, on the other hand, do not express sufficient levels of P450arom for detectable enzyme activity. Because P450arom is up-regulated in the ovaries of CCAAT/enhancer binding protein (C/EBP) beta knockout mice and activation of the ovarian-type P450arom promoter (II) is responsible for aberrant P450arom expression in endometriosis, we sought here to evaluate the possible roles of C/EBP isoforms in the regulation of P450arom expression in endometriotic vs. eutopic endometrial stromal cells. We previously found that the -517-bp flanking region of promoter II contained the critical cis-acting elements for baseline and cAMP (analog)-induced activity. In this study, we disrupted several potential sequences and found that mutations of a -211/-197-bp cAMP-response element (CRE) and a -317/-304-bp C/EBP binding site abolished both baseline and cAMP-induced promoter II activity. Ectopic expression of C/EBPalpha increased both baseline and cAMP-dependent promoter II activity significantly in endometriotic cells, whereas ectopic expression of C/EBPbeta or C/EBPdelta abolished promoter II activity in both untreated and cAMP-treated endometriotic stromal cells. Comparable changes in promoter II activity were observed using endometrial stromal cells, which showed, however, seemingly diminished levels of baseline and cAMP-induced promoter II activity in comparison with endometriotic cells. EMSA using a probe containing the critical -317/-304-bp C/EBP site upstream of promoter II demonstrated a distinct DNA-protein complex in endometriotic, but not in endometrial stromal cells. This specific complex, however, could not be altered using antibodies against C/EBPalpha, -beta, or -delta. Because CRE is another potential DNA motif that can bind C/EBP isoforms, we next used EMSA using a probe containing the -211/-197-bp CRE and demonstrated that specific DNA-protein complexes contained C/EBPalpha but not C/EBPbeta or C/EBPdelta in endometriotic stromal cells. In contrast, C/EBPbeta and C/EBPdelta but not C/EBPalpha were detected in DNA-protein complexes using nuclear extracts from endometrial stromal cells. Western blotting and immunohistochemistry demonstrated expression of C/EBPalpha, -beta, and -delta in human endometriotic and endometrial stroma and epithelium. Intriguingly, C/EBPbeta was expressed at increased levels in stromal cells of human eutopic endometrium compared with simultaneously biopsied endometriotic tissues. We conclude that both -317/-304 and -211/-197-bp elements in promoter II are critical for the robust cAMP-dependent induction in endometriosis. C/EBPalpha up-regulates, whereas C/EBPbeta and C/EBPdelta inhibit P450arom promoter activity via binding primarily to the -211/-197-bp CRE under in vitro conditions. In vivo down-regulation of C/EBPbeta in endometriotic stromal cells and its up-regulation in endometrial stromal cells may in part account for the induction of P450arom expression in endometriosis and its inhibition in endometrium.  相似文献   
59.
The patient was a 39-year-old woman admitted with complaints of fever, clubbed fingers and arthralgia. A chest roentgenogram and chest computed tomographic scan revealed a mass in the left lower lobe. Transbronchial lung biopsy was performed, and a diagnosis of moderately differentiated adenocarcinoma was made. Physical examination confirmed finger clubbing in both hands. Bone scintigram showed marked accumulation of 99mTc-MDP in the long bones, bones of the elbows, and patellae. These findings yielded a diagnosis of pulmonary hypertrophic osteoarthropathy associated with primary lung cancer in young adult. The patient had fever and disturbance of gait of arthralgia on admission, and was treated with an oral non-steroidal anti-inflammation drug (NSAID). Advanced non small cell lung cancer (clinical stage T2 N3 M1, Stage IV) was then diagnosed. Gefitinib was administered after EGFR mutation was found in the tumor specimen. NSAID therapy alleviated the fever and arthralgia. After starting gefitinib and discontinuing the NSAID, She had kept a remission of rational symptom with cytoreductive effect. The abnormal findings of bone scintigrams subsequently disappeared and the patient's serum ICTP dropped.  相似文献   
60.
Papillary carcinoma is the most common thyroid malignancy. As the cytological diagnosis of papillary carcinoma is not difficult in patients with the usual type of lesion, fine‐needle aspiration (FNA) cytology is an effective method for preoperative evaluation. However, this modality is often ineffective in identifying the follicular variant of papillary thyroid carcinoma (FVPTC) due to its similarity to other follicular lesions and the incompleteness of typical nuclear features. Therefore, we investigated the expression of immunocytochemical markers of papillary carcinoma in cytological specimens of FVPTC and evaluated their utilities. The immunoreactivity of HBME‐1 and CD15 was investigated using 50 imprint smear cytological specimens obtained from thyroid lesions, including 13 FVPTC. The sensitivity and specificity of HBME‐1 for FVPTC were 92% and 89%, respectively, while those of CD15 were 23% and 100%, respectively. In conclusion, HBME‐1 is a sensitive marker of papillary carcinoma, including both usual type and FVPTC, in cytological specimens. Therefore, using HBME‐1 immunocytochemistry in FNA cytology will lead to reduction of the incidence of false‐negative diagnoses of FVPTC. Although CD15 is apparently inferior in terms of sensitivity for FVPTC, its excellent specificity will support the definitive diagnosis of thyroid malignancies, including FVPTC, after screening with HBME‐1.  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