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   180533篇
  免费   1403篇
  国内免费   35篇
耳鼻咽喉   1201篇
儿科学   6726篇
妇产科学   3124篇
基础医学   17026篇
口腔科学   1709篇
临床医学   12884篇
内科学   31815篇
皮肤病学   730篇
神经病学   16791篇
特种医学   9049篇
外国民族医学   1篇
外科学   30128篇
综合类   2433篇
一般理论   2篇
预防医学   18396篇
眼科学   2875篇
药学   9770篇
中国医学   644篇
肿瘤学   16667篇
  2023年   63篇
  2022年   143篇
  2021年   256篇
  2020年   143篇
  2019年   216篇
  2018年   22114篇
  2017年   17513篇
  2016年   19632篇
  2015年   1083篇
  2014年   1058篇
  2013年   1047篇
  2012年   7382篇
  2011年   21395篇
  2010年   18997篇
  2009年   11685篇
  2008年   19736篇
  2007年   21908篇
  2006年   789篇
  2005年   2395篇
  2004年   3560篇
  2003年   4542篇
  2002年   2647篇
  2001年   368篇
  2000年   505篇
  1999年   237篇
  1998年   243篇
  1997年   230篇
  1996年   113篇
  1995年   117篇
  1994年   112篇
  1993年   75篇
  1992年   92篇
  1991年   143篇
  1990年   169篇
  1989年   118篇
  1988年   78篇
  1987年   62篇
  1986年   57篇
  1985年   57篇
  1984年   52篇
  1983年   43篇
  1982年   47篇
  1980年   52篇
  1974年   45篇
  1970年   35篇
  1969年   33篇
  1938年   60篇
  1934年   30篇
  1932年   56篇
  1930年   46篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Whether inhibiting the activity of nuclear factor (NF)-κB potentiates cisplatin-induced apoptosis in non-small cell lung cell line A549 cells was investigated. The recombinant plasmid pcDNA3.1(+)/IκBα expressing IκBα was constructed. The in vitro cultured A549 cells were transfected with pcDNA3.1 (+)/IκBα alone, or pcDNA3.1(+)/IκBα combined with cisplatin. The mitochondrial membrane potential (△ψm) was determined by rhodamine 123, the activity of caspase-3 was tested by colorimetric assay, and cell apoptosis was detected by flow cytometry with the annexin V/propidium iodide assay. The results showed that the activity of NF-κB in A549 cells was inhibited by transfecting pcDNA3.1(+)/IκBα. Transfection of pcDNA3.1(+)/IκBα alone did not promote apoptosis. Treatment of cisplatin alone had a little effect on cell apoptosis. Transfection of pcDNA3.1(+)/IκBα combined with cisplatin treatment significantly induced apoptosis of A549 ceils. It was concluded that inhibiting the activity of NF-κB potentiated cisplatin-induced apoptosis of A549 cells.  相似文献   
992.
Background The future remnant liver (FRL) limit for safe major hepatectomy with low risk of postoperative liver failure has not yet been well defined. Methods Between April 2000 and September 2004, every patient scheduled for major hepatectomy in our institution underwent CT-volumetry of FRL. Patients with FRL <25% underwent portal vein embolization (PVE). Exclusion criteria were PVE, associated vascular resection and liver cirrhosis. The FRL was correlated with short-term results in patients with normal liver (group A) and those with impaired liver function secondary to neoadjuvant chemotherapy or cholestasis (bilirubin >2 mg/100 ml) (group B). Liver dysfunction was defined as both PT <50% and serum bilirubin level >5 mg/100 ml for three or more consecutive days. Results A total of 119 patients were analyzed, 72 in group A and 47 in group B. The FRL value was the only significant risk factor for postoperative liver dysfunction in the univariate and multivariate analysis (p = 0.009). The FRL did not correlate with postoperative mortality and morbidity. Bilirubin and prothrombin time (PT) on days 3 and 7 were significantly correlated to FRL in both groups. In group A, patients with postoperative liver dysfunction had a FRL<30% (3 versus 0; p = 0.005). According to receiving operator characteristic (ROC) curve analysis, a FRL value of 26.5% predicted postoperative liver dysfunction with 66.7% sensitivity, 97.1% specificity, 50% positive predictive value (PPV), and 98.5% negative predictive value (NPV). In group B, patients with postoperative liver dysfunction had a FRL <35% (4 versus 0; p = 0.027). According to ROC curve analysis, a FRL value of 31.05% predicted postoperative liver dysfunction with 75% sensitivity, 79.1% specificity, 25% PPV, and 97.1% NPV. Conclusions Hepatectomy can be considered safe when FRL is >26.5% in patients with healthy liver and >31% in patients with impaired liver function.  相似文献   
993.
Robotic surgery is being performed more frequently for a variety of urologic procedures. Since the first robotic adrenalectomy less than a decade ago, this modality has gained increased acceptance in the urologic community and has been employed with increased frequency in minimally invasive centers. This review evaluates the current literature on robotic adrenalectomy, its indications, as well as its advantages and limitations compared with other forms of surgical management of adrenal pathology.  相似文献   
994.
From the earliest stages of embryonic development, cells of epithelial and mesenchymal origin contribute to the structure and function of developing organs. However, these phenotypes are not always permanent, and instead, under the appropriate conditions, epithelial and mesenchymal cells convert between these two phenotypes. These processes, termed Epithelial-Mesenchymal Transition (EMT), or the reverse Mesenchymal-Epithelial Transition (MET), are required for complex body patterning and morphogenesis. In addition, epithelial plasticity and the acquisition of invasive properties without the full commitment to a mesenchymal phenotype are critical in development, particularly during branching morphogenesis in the mammary gland. Recent work in cancer has identified an analogous plasticity of cellular phenotypes whereby epithelial cancer cells acquire mesenchymal features that permit escape from the primary tumor. Because local invasion is thought to be a necessary first step in metastatic dissemination, EMT and epithelial plasticity are hypothesized to contribute to tumor progression. Similarities between developmental and oncogenic EMT have led to the identification of common contributing pathways, suggesting that the reactivation of developmental pathways in breast and other cancers contributes to tumor progression. For example, developmental EMT regulators including Snail/Slug, Twist, Six1, and Cripto, along with developmental signaling pathways including TGF-β and Wnt/β-catenin, are misexpressed in breast cancer and correlate with poor clinical outcomes. This review focuses on the parallels between epithelial plasticity/EMT in the mammary gland and other organs during development, and on a selection of developmental EMT regulators that are misexpressed specifically during breast cancer.  相似文献   
995.

Background

Roux-en-Y gastric bypass (LRYGB) has weight-independent effects on glycemia in obese type 2 diabetic patients, whereas sleeve gastrectomy (LSG) is less well characterized. This study aims to compare early weight-independent and later weight-dependent glycemic effects of LRYGB and LSG.

Methods

Eighteen LRYGB and 15 LSG patients were included in the study. Glucose, insulin, GLP-1, and GIP levels were monitored during a modified 30 g oral glucose tolerance test before surgery and 2 days, 3 weeks, and 12 months after surgery. Patients self-monitored glucose levels 2 weeks before and after surgery.

Results

Postoperative fasting blood glucose decreased similarly in both groups (LRYGB vs. SG; baseline—8.1?±?0.6 vs. 8.2?±?0.4 mmol/l, 2 days—7.8?±?0.5 vs. 7.4?±?0.3 mmol/l, 3 weeks—6.6?±?0.4 vs. 6.6?±?0.3 mmol/l, respectively, P <?0.01 vs. baseline for both groups; 12 months—6.6?±?0.4 vs. 5.9?±?0.4, respectively, P <?0.05 for LRYGB and P <?0.001 for LSG vs. baseline, P =?ns between the groups at all times). LSG, but not LRYGB, showed increased peak insulin levels 2 days postoperatively (mean?±?SEM; LSG +?58?±?14%, P <?0.01; LRYGB ??8?±?17%, P =?ns). GLP-1 levels increased similarly at 2 days, but were higher in LRYGB at 3 weeks (AUC; 7525?±?1258 vs. 4779?±?712 pmol?×?min, respectively, P <?0.05). GIP levels did not differ. Body mass index (BMI) decreased more after LRYGB than LSG (??10.1?±?0.9 vs. ??7.9?±?0.5 kg/m2, respectively, P <?0.05).

Conclusion

LRYGB and LSG show very similar effects on glycemic control, despite lower GLP-1 levels and inferior BMI decrease after LSG.
  相似文献   
996.

Introductions

Different staging systems have been devised for patients undergoing resection for hepatocellular carcinoma (HCC) with disparate results. The aim of this study was to create a new nomogram to predict individual survival after hepatectomy for HCC.

Methods

Based on the “Hepatocellular Carcinoma: Eastern & Western Experiences Network,” data from 2046 patients who underwent HCC resections at ten centers were reviewed. Patient survival was analyzed with Cox-regression analysis to construct a unique nomogram and contour plots to predict survival.

Results

The nomograms built on the multivariate analyses, which showed that the independent predictors were tumor size, tumor number, vascular invasion, cirrhosis, preoperative bilirubin value, and esophageal varices, showed good calibration and discriminatory abilities with C-index value of 0.62 (95 % CI, 0.59–0.69) and 0.61 (95 % CI, 0.56–0.64) for overall and disease-free survival, respectively. The 5-year survival contour plots showed that the presence of vascular invasion was associated with decreased survival, regardless of the tumor number or size. Cirrhosis and varices were equally associated with decreased survival, according to the tumor number or size.

Conclusions

These nomograms accurately predict individual prognosis after HCC resection and support an expansion of the selection criteria for resection. They offer useful guidance to clinicians for individual survival prediction.
  相似文献   
997.

Background

In recent years, surgical outcomes have improved, and positive reports on surgery for type A aortic dissection (AAD) in the elderly are increasing. However, the difference between surgical and conservative treatments in the elderly remains unclear. Therefore, we conducted this study to determine whether surgery should be performed for Stanford (AAD) in elderly patients.

Methods

Data of patients aged 80?years or older who were hospitalized for AAD from April 2014 to March 2016 were extracted from the Japanese national inpatient database. Outcome measures were all-cause in-hospital death, stroke, acute kidney injury and tracheotomy, and composite adverse events (consisting of all-cause in-hospital death, stroke, acute kidney injury, and tracheotomy), and we compared them between surgical and conservative treatments using propensity score matching.

Results

The study cohort included 3258 patients, with 845 matched pairs (1690 patients) in the propensity score matching. All-cause in-hospital death was significantly lower in the surgical treatment group than in the conservative treatment group before and after matching (15.6% vs. 51.1%, p?<?0.001; 16.7% vs. 31.6%, p?<?0.001, respectively); however, there was no significant difference in composite adverse events after matching (36.0%, conservative vs. 37.2%, surgical; p?=?0.65), and adjusted odds ratio was 1.06 and 95% confidence interval was 0.86–1.29 (p?=?0.61) with reference to conservative treatment.

Conclusions

All-cause in-hospital death among elderly patients with AAD was significantly lower in patients treated surgically than in those undergoing conservative treatment. However, there was no significant difference between the two groups in the event-free survival, which is important for the elderly. These findings may be used in the consideration of treatment course for elderly patients with AAD.
  相似文献   
998.
Background Appropriate management of cystic lesions of the pancreas is controversial. Major pancreatectomies (pancreaticoduodenectomy or distal pancreatectomy with splenectomy) are the commonly used procedures, even though most cystic lesions are noninvasive neoplasms. We tested the adequacy of limited pancreatectomies in the treatment of pancreatic cystic lesions. Methods Data from 109 patients who underwent surgical resection of a pancreatic cystic lesion at National Taiwan University Hospital from 2001 to 2007 were retrospectively reviewed. Major pancreatomies (n = 79) constituted pancreaticoduodenectomy and total/distal pancreatectomies, while other resection procedures (n = 30) represented limited pancreatectomies. Clinicopathologic features were compared between the major and limited groups. Results There were no statistically significant differences in sex, age, presence of symptoms, cyst diameter, minor or major treatment complications, or pancreatic leakage between the two groups. Cystic lesions located in the neck/body/tail rather than in the head/uncinate process were significantly more often treated with limited pancreatectomy (P = .02). Both groups had similar pathologic distribution of cystic lesions, with the exception of nine invasive neoplasms. The latter were treated with major pancreatectomy. No recurrence was noted in 100 patients with noninvasive cystic neoplasms after major or limited pancreatectomy. Conclusions Noninvasive pancreatic cystic neoplasms can be safely and effectively treated by limited pancreatectomy.  相似文献   
999.
Background Information on surgical complications of laparoscopy-assisted distal gastrectomy (LADG) and their risk factors is limited in the literature despite increasing popularity of this procedure. This study was performed to identify the surgical complications and their associated risk factors of LADG in early gastric cancer. Methods LADG was performed in 347 gastric cancer patients from January 2002 to December 2006 at the Korean National Cancer Center by four surgeons with ample experience of open gastric surgery before LADG. LADG indications for cases of gastric cancer at our institution are preoperatively diagnosed cT1N0 or cT1N1, except in cases with an absolute indication for endoscopic resection. Lymph node dissection of more than D1 + β was performed in all patients. Intraoperative and postoperative complications were reviewed and their risk factors were retrospectively analyzed by prospective database information. Results Forty complications occurred in 34 patients (9.8%), but there was no mortality. Intraoperative complications occurred in nine patients (2.6%), and open conversion was performed in eight (2.3%) of these patients. Early and late postoperative complications occurred in 21 (6.1%) and 10 (2.9%) patients, respectively. The most serious complication was vascular injury resulting in bleeding or organ ischemia, which occurred in seven patients. Degree of lymph node dissection and surgical inexperience were found to be risk factors of surgical complication (P = .023, odds ratio 2.832, 95% confidence interval 1.155–6.946 vs. P = .028, odds ratio 2.975, 95% confidence interval 1.127–7.854). Conclusions Lymph node dissection during LADG should be performed cautiously to prevent surgical complications like vascular injuries, especially during the surgeon’s early learning period.  相似文献   
1000.
Background  We evaluated the prognostic value of the preoperative serum carcinoembryonic antigen (CEA) level in patients with colorectal cancer (CRC). Patients and Methods  The study group comprised 638 patients. The optimal cutoff value for the preoperative serum CEA level was determined. Predictive factors of recurrence were evaluated using multivariate analyses. The relapse-free time was investigated according to the CEA level. Results  All patients underwent potentially curative resection for CRC without distant metastasis, classified as stage I, II, or III. The optimal cutoff value for preoperative serum CEA level was 10 ng/ml. Elevated preoperative serum CEA level was observed in 92 patients. Multivariate analysis identified tumor–node–metastasis (TNM) stage and preoperative serum CEA level as independent predictive factors of recurrence. The relapse-free survival between CEA levels >10 ng/ml and <10 ng/ml significantly differed in patients with stage II and III. However, there was no significant difference in relapse-free survival between CEA levels >10 ng/ml and <10 ng/ml in patients with stage I. Conclusion  Preoperative serum CEA is a reliable predictive factor of recurrence after curative surgery in CRC patients and a useful indicator of the optimal treatment after resection, particularly for cases classified as stage II or stage III.  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