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   11162篇
  免费   580篇
  国内免费   80篇
耳鼻咽喉   98篇
儿科学   194篇
妇产科学   96篇
基础医学   1353篇
口腔科学   238篇
临床医学   766篇
内科学   3114篇
皮肤病学   256篇
神经病学   682篇
特种医学   479篇
外科学   1967篇
综合类   49篇
预防医学   241篇
眼科学   268篇
药学   728篇
中国医学   22篇
肿瘤学   1271篇
  2024年   12篇
  2023年   147篇
  2022年   286篇
  2021年   440篇
  2020年   238篇
  2019年   336篇
  2018年   392篇
  2017年   287篇
  2016年   322篇
  2015年   305篇
  2014年   395篇
  2013年   438篇
  2012年   759篇
  2011年   720篇
  2010年   429篇
  2009年   356篇
  2008年   604篇
  2007年   710篇
  2006年   659篇
  2005年   656篇
  2004年   637篇
  2003年   564篇
  2002年   554篇
  2001年   166篇
  2000年   128篇
  1999年   129篇
  1998年   106篇
  1997年   88篇
  1996年   93篇
  1995年   63篇
  1994年   54篇
  1993年   53篇
  1992年   74篇
  1991年   70篇
  1990年   64篇
  1989年   59篇
  1988年   58篇
  1987年   42篇
  1986年   40篇
  1985年   41篇
  1984年   32篇
  1983年   28篇
  1982年   27篇
  1981年   16篇
  1980年   16篇
  1979年   15篇
  1977年   20篇
  1975年   10篇
  1970年   8篇
  1966年   10篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
The objective of this study was to assess the relationship of signaling molecules to monocyte/ macrophages as a precursor to venous valve and venous wall dysfunction in patients with varicose veins. One of the hallmarks of venous dysfunction is destruction of venous valves with subsequent reflux and elevation of distal venous pressure. We recently observed that monocytes/macrophages migrate into the venous walls and valves of patients with venous insufficiency. There, they may play a role in the pathogenesis of primary venous insufficiency. If so, an important element in their performance would be the interaction between the monocytes and the endothelium as a precursor of damage to venous valves and the venous wall. To explore this interaction, immunohistochemistry was carried out to detect adhesion molecules and cytokines in surgical specimens removed during surgical therapy. Twenty-four surgical specimens consisting of proximal saphenous vein and subterminal valve were obtained using minimally traumatic technique in 6 males and 18 females who ranged in age from 31 to 79 years. Reflux was confirmed preoperatively by duplex technique, and severity was classified by the CEAP classification of the American Venous Forum. Ten patient limbs were class 2, eight were class 3, four were class 4, and two were class 6. The venous specimens were labeled using monoclonal antibody against ICAM-1, E-selectin, IL-1alpha, and TNF-alpha. CD68 was used for detection of monocytes/macrophages. Our results indicate that not only luminal venous endothelium but also endothelium in the vasa vasora of refluxing saphenous veins is activated, as indicated by the up-regulation of ICAM-1. However, IL-1alpha and TNF-alpha were increased in only selected specimens and are mainly detected in the vein wall. The factors that serve as trigger mechanisms to activate cells in the pathogenesis of primary venous dysfunction remain to be explored.  相似文献   
112.
BACKGROUND: Infection of the gastric mucosa by helicobacter pylori is primarily responsible for gastritis, gastric ulcer, adenocarcinoma, and lymphoproliferative disorders. H. pylori appears to accelerate apoptosis and the proliferation of the gastric epithelium directly or indirectly. To precisely assess the proliferative and apoptotic profile of .H pylori-infected gastric mucosa, a quantitative imaging system is now required. METHODS: Fifty-two patients with H. pylori gastritis were the subjects of the study. Biopsy materials were taken from at least two sites (usually three to five sites) including the antrum and corpus. The grade of gastritis was evaluated by the updated Sydney System. The proliferative and apoptotic profile was examined by Ki-67 immunohistochemistry and by a terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end-labeling method. In addition, Ki-67-positive cells were quantitated by an image processor for analytical pathology (IPAP) system. RESULTS: H. pylori density and polymorphonuclear neutrophil activity were significantly decreased after H. pylori eradication ( P< 0.0001). Chronic inflammation (P< 0.0001) and lymphoid follicle numbers ( P < 0.0005) were also significantly decreased after the eradication. Glandular atrophy and intestinal metaplasia were slightly decreased after eradication, but the decrease did not reach the significant level. the Ki-67 labeling index was significantly decreased after the eradication P< 0.0001). The apoptosis index was also decreased after the eradication, but this decrease did not reach the significant level ( P = 0.06). CONCLUSION: our data suggest that the activation of proliferative cells and induction of apoptosis in the gastric mucosa is a response to H. pylori-induced mucosal damage. Moreover, IPAP may be a useful technology for evaluating the results of immunohistochemistry, and it could provide quantitative and reliable data for studying H. pylori gastritis.  相似文献   
113.
BACKGROUND: Dysregulation of apoptosis is one of the likely underlying mechanisms of mesangial proliferative glomerulonephritis (GN), a disease in which proinflammatory cytokines exhibit a wide range of biological activities. Among them, tumor necrosis factor-alpha (TNF-alpha) induces two conflicting pathways, one leading to activation of the nuclear factor-kappa B (NF-kappa B), and the other leading to caspase-mediated apoptosis. We investigated whether or not specific inhibition of NF-kappa B affects TNF-alpha-induced apoptosis in rat mesangial cells (MCs). METHODS: To specifically inhibit NF-kappa B activation, we constructed a recombinant adenovirus vector expressing a truncated form of I kappa B alpha (AdexI kappa B delta N) that lacks the phosphorylation sites essential for the activation of NF-kappa B. Electrophoretic mobility shift assay was performed to evaluate NF-kappa B activity. Nuclear morphology was observed by staining with Hoechst-33258. DNA fragmentation was detected using an ELISA kit with an antihistone antibody. To investigate the regulation of apoptosis, we measured caspase-3 and caspase-8 activity by ELISA, and examined the Bcl-2 and Bax protein level by Western blot. RESULTS: TNF-alpha-induced NF-kappa B activation was blocked by overexpression of I kappa B delta N. Overexpression of I kappa B delta N potentiated TNF-alpha-induced apoptosis compared to mock transfection, and the potentiation was abolished by treatment with a caspase-3 inhibitor, Z-DEVD-FMK. Overexpression of I kappa B delta N augmented TNF-alpha-induced caspase-3 and caspase-8 activity, but did not affect Bcl-2 or Bax protein expression. CONCLUSION: Overexpression of I kappa B delta N potentiates TNF-alpha-induced apoptosis and augments caspase-8 and caspase-3 activity in rat MCs without changing Bcl-2 or Bax protein expression. These results suggest the potential usefulness of AdexI kappa B delta N to induce apoptosis in MCs under inflammatory conditions.  相似文献   
114.
Hori Y  Takeyama Y  Ueda T  Shinkai M  Takase K  Kuroda Y 《Surgery》2000,127(6):641-649
BACKGROUND: The mechanism of acute pancreatitis-induced hepatocellular injury is unclear. We have observed hepatocyte apoptosis in rat acute necrotizing pancreatitis. These studies were designed to determine the mediator(s) responsible for hepatocyte apoptosis and to clarify the significance of macrophages as its source. METHODS: A rat sodium deoxycholate-induced pancreatitis model was used. Immunohistochemical studies for apoptosis-inducing mediators on hepatocytes were examined in the liver and on the peritoneal macrophages. The levels of transforming growth factor-beta1 (TGF-beta1) were also evaluated quantitatively with an enzyme-linked immunosorbent assay. Induction of apoptosis on the hepatocytes was evaluated by in situ nick-end labeling and tissue DNA fragmentation enzyme-linked immunosorbent assay. Finally, the effects of TGF-beta1 neutralization and macrophage depletion were examined. RESULTS: In the liver and the peritoneal macrophages, strong expression of TGF-beta1 was detected early in the course of pancreatitis. In sodium deoxycholate-induced pancreatitis, the levels of TGF-beta1 were also elevated in the plasma (9.2 +/- 0.8 ng/mL), in the pancreatitis-associated ascitic fluid (11.5 +/- 0.6 ng/mL), and in the liver homogenate (2.8 +/- 0.3 ng/g of liver tissue). Moreover, the amount of fragmented DNA of the liver with pancreatitis was 290% +/- 20% of that with a sham operation and serum alanine aminotransferase levels elevated to 248.2 +/- 67.0 IU/L. TGF-beta1 neutralization partly blocked the positive labeling on the nuclei of the hepatocytes, the elevation of the amounts of fragmented DNA (205% +/- 10% of sham operation), and the serum alanine aminotransferase level (144.2 +/- 14.9 IU/L). On the other hand, the macrophage depletion caused a marked decrease in the TGF-beta1 protein level in the plasma (4.8 +/- 1.2 ng/mL) or in the pancreatitis-associated ascitic fluid (8.0 +/- 1.0 ng/mL). Moreover, the macrophage depletion completely inhibited the elevation of the TGF-beta1 protein level in the liver homogenate (1.5 +/- 0.4 ng/g of liver tissue), and thereafter decreased the amounts of the positive labeling on the nuclei of the hepatocytes and decreased the amount of fragmented DNA (120% +/- 18% of sham operation) and the serum alanine aminotransferase elevation (119.2 +/- 24.2 IU/L). CONCLUSIONS: In a model of sodium deoxycholate-induced pancreatitis, macrophages are responsible for pancreatitis-induced hepatocellular injury by means of apoptosis, and macrophage-derived TGF-beta1 is one of the major factors inducing the hepatocyte apoptosis.  相似文献   
115.
116.
Abstract The delivery of nitric oxide (NO) via a nasopharyngeal tube is an alternative to endotracheal intubation. A male infant with end-stage pulmonary hypertension (PH) due to a severe hypoplastic lung developed a PH crisis on day 145 and received NO inhalation via a nasopharyngeal tube. Clinical improvement was maintained for 7 days with18–22ppm NO inhalation. The patient remained in close physical contact with his parents without the use of sedation. Blood methemoglobin levels remained below 1%. The environmental NO levels were less than 0.06 ppm and NO2 less than 0.3 ppm throughout the treatment, well within the safety margin. On day 152, the patient succumbed to hypoxemia and heart failure. The use of a nasopharyngeal NO delivery system without sedation, as an alternative to endotracheal intubation with sedation, was a practical method in treating a patient with PH while maintaining a certain quality of life for the patient and the family.  相似文献   
117.
Tumor recurrence rate (TRR) and mortality rate (MR) of invasive ductal carcinoma (IDC) of the breast in short-term follow-up are relatively low. Nevertheless, it is extremely important to identify patients at risk of early recurrence or death after surgery. The aim of this study was to establish a new histological prognostic classification scheme for IDC in order accurately to predict the short-term outcome. The following histological parameters were analyzed in 201 IDCs: 1) tumor size, 2) structural atypia, 3) nuclear atypia, 4) number of mitotic figures, 5) fibrotic focus (FF), 6) vascular invasion, 7) tumor necrosis, 8) skin invasion, 9) muscle invasion, 10) nodal status and 11) extramammary fat invasion. Multivariate analysis showed that nuclear atypia, presence of FF, and the invasive length of fat invasion (ILFI) were the most important histological parameters correlated with TRR or MR of IDCs. Accordingly, a new histological classification based on nuclear atypia, FF and ILFI (Nucleus-Fibrotic focus-Fat invasion, NFF) was devised. Comparative studies were performed with the following existing prognostic classifications: 1) histological grade, 2) modified Scarff-Bloom-Richardson histological grade, 3) prognostic index and 4) pathological TNM (pTNM) stage classifications. Patient grouping defined by NFF classification significantly correlated with tumor recurrence or death of IDCs in all cases, cases at stages I and II, those without lymph node metastasis and those who were estrogen receptor (ER)-positive after adjustment for the other four classifications, using multivariate analysis. NFF classification appeared superior to existing prognostic classifications for the accurate prediction of the short-term outcome for patients with IDCs in low risk groups.  相似文献   
118.
We constructed a question and answer system for direct delivery of E-mail queries from the general public to the proper hospital representative and with which the system administrator can monitor E-mail replies. The system consists of two sub-systems; one is an E-mail questionnaire sub-system that automatically delivers E-mail queries to the proper person and an E-mail reply monitor sub-system with which the system administrator can monitor the E-mail replies. The monitor system compares the origin address of the E-mail reply and the destination address on a questionnaire filled out at the time the query is made. In a test of the system, 56 queries were received in 31 days, with 37 replied to. The interval from receipt of an E-mail query to reply was calculated. Nineteen replies were submitted within 2 days.  相似文献   
119.
A 69-year-old woman was admitted to our hospital because of dysphasia. The upper G-I examination showed a stenosis at the middle thoracic esophagus and poorly differentiated adenocarcinoma was revealed histologically. Chest CT scan showed a mass shadow in the right upper lobe of the lung. She had undergone a partial resection of right upper lobe because of lung cancer seven years before. She was diagnosed as metachrous double carcinoma of the lung and the esophagus. The method of surgery included right upper lobectomy of the lung, esophagectomy and intrathoracic esophageal reconstruction using the gastric tube. The patient manifested pneumonia due to the failure of the sutures after the surgery and died on the twentieth postoperative day. When conducting simultaneous resection of both cancer and esophageal reconstruction for the double cancer of the lung and the esophagus, it was considered necessary to conduct the anastomosis outside the thoracic cavity for the purpose of preventing the pulmonary complication due to the failure of the sutures.  相似文献   
120.
Two patients with postoperative interstitial pneumonia are reported. Preoperative diagnosis was primary lung cancer without idiopathic interstitial pneumonia (IIP). Within one week after operation acute interstitial pneumonia (AIP) occurred on the nonoperated side and developed. Steroid therapy was performed but one was dead. AIP is a fatal complication after pulmonary resection and steroid therapy may be useful in some cases of postoperative AIP.  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