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   5023篇
  免费   434篇
  国内免费   32篇
耳鼻咽喉   56篇
儿科学   102篇
妇产科学   108篇
基础医学   774篇
口腔科学   92篇
临床医学   546篇
内科学   1114篇
皮肤病学   108篇
神经病学   464篇
特种医学   125篇
外科学   627篇
综合类   90篇
一般理论   5篇
预防医学   502篇
眼科学   44篇
药学   206篇
中国医学   11篇
肿瘤学   515篇
  2023年   42篇
  2022年   54篇
  2021年   139篇
  2020年   73篇
  2019年   105篇
  2018年   148篇
  2017年   97篇
  2016年   115篇
  2015年   150篇
  2014年   182篇
  2013年   252篇
  2012年   331篇
  2011年   301篇
  2010年   202篇
  2009年   164篇
  2008年   281篇
  2007年   300篇
  2006年   262篇
  2005年   296篇
  2004年   267篇
  2003年   223篇
  2002年   185篇
  2001年   125篇
  2000年   91篇
  1999年   82篇
  1998年   38篇
  1997年   45篇
  1996年   44篇
  1995年   33篇
  1994年   38篇
  1993年   16篇
  1992年   63篇
  1991年   61篇
  1990年   54篇
  1989年   47篇
  1988年   37篇
  1987年   39篇
  1986年   37篇
  1985年   46篇
  1984年   31篇
  1983年   37篇
  1982年   27篇
  1981年   33篇
  1980年   21篇
  1979年   28篇
  1978年   15篇
  1976年   15篇
  1972年   16篇
  1937年   41篇
  1936年   38篇
排序方式: 共有5489条查询结果,搜索用时 15 毫秒
91.
Drug-Induced Esophagitis   总被引:7,自引:0,他引:7  
Drug-induced esophagitis is being recognized increasingly in the past few years. We have reviewed 175 cases with a view to classifying this disease based on pathology. Drug-induced esophageal injury tends to occur at the anatomical site of narrowing, with the middle third behind the left atrium predominating. The disease is classified broadly into two groups. The first group is transient and self-limiting, as exemplified by tetracycline- and emepronium-induced injury (57.3%). The second is the persistent esophagitis group, often with stricture with two distinct entities: 1) patients on nonsteroidal antiinflammatory agents whose injury is aggravated by gastroesophageal reflux (26.2%) (reflux aggravated), and 2) patients with potassium chloride and quinidine sulfate-induced injury (16.2%) (persisting drug injury). We report a case that highlights the pathophysiology (delayed transit, persisting potassium within the stricture) of this type of injury which is not reflux aggravated.  相似文献   
92.
Leo JC  Guo C  Woon CT  Aw SE  Lin VC 《Endocrinology》2004,145(3):1314-1321
Progesterone receptor (PR), glucocorticoid receptor, and mineralocorticoid receptor belong to a subfamily of nuclear receptor superfamily with similar sequence and structural characteristics. Many reports have documented glucocorticoid-like effects of progesterone in various tissues. This study addresses the issue of cross-talk between corticosteroids and PR using PR-transfected MDA-MB-231 cells ABC28 and vector-transfected control cells CTC15. At physiological concentrations, dexamethasone, cortisol, and aldosterone mimic the effects of progesterone by inducing significant growth inhibition, cell spreading, and focal adhesions in PR-positive ABC28 cells. These hormones also induce progesterone-like effects in increasing the expression of p21(CIP1/WAF1) protein and decreasing the level of phospho-p42/p44 mAPK. Two lines of evidence suggest that these effects are mediated by cross-talk with PR. First, these compounds do not exhibit the same progesterone-like effects in PR-negative CTC15 cells. Second, PR blocker ZK98299 abolishes their effect on cell spreading and focal adhesion in ABC28 cells. The cross-talk is corticosteroid specific because estradiol and thyroid hormone triiodothyronine have no effect on PR-transfected cells ABC28. It is also interesting to note that dexamethasone induces a small but detectable increase of focal adhesions and limited growth stimulation in vector-transfected cells CTC15. In contrast, progesterone exhibits no detectable effect on CTC15 cells. This study provides evidence that glucocorticoid and mineralocorticoid cross-talk with PR to produce progesterone-like effects in breast cancer cells. Glucocorticoid receptor and PR share some overlapping activity in mediating focal adhesion but not in regulating cell proliferation.  相似文献   
93.
Abdominosacral resection for midrectal cancer.   总被引:3,自引:0,他引:3  
Abdominosacral resection is the most reliable radical sphincter-saving operation for midrectal cancers which are too low for anterior resection. The posterior incision provides maximum exposure for wide resection of the tumor, a measured distal margin, and an accurate anastomosis. The procedure can be carried out consistently to the pelvic floor without disrupting the anal sphincters and their innervation. Sphincter function is consistently preserved. Mortality rate is no higher than for other radical rectal resections. Morbidity can be limited by the selective use of protective colostomy. The use of mechanical retractors and the end-to-end stapler facilitates the operation and should encourage its wider application. The transsacral approach allows mobilization of the rectum to the levators in every case, and resection is limited only by the distance of the tumor from the sphincter, and not by poor exposure due to obesity or a narrow pelvis. In the treatment of 926 consecutive patients with rectal cancer, sphincter-saving resection was possible in 79%. In our experience, abdominosacral resection extends the range of sphincter-saving resection beyond that which is possible by the abdominal approach alone, with no compromise in safety and no increased risk of local recurrence or death from cancer.  相似文献   
94.
AIM: Autologous blood donation (ABD) is mainly used to reduce the use of banked blood. In fact, ABD can be regarded as acute blood loss. Would ABD 2-3 d before operation affect the CVP level and subsequently result in less blood loss during liver resection was to be determined. METHODS: Eighty-four patients undergoing living donor left hepatectomy were retrospectively divided as group Ⅰ (GI) and group Ⅱ (Gil) according to have donated 250-300 mL blood 2-3 d before living donor hepatectomy or not. The changes of the intraoperative CVP, surgical blood loss, blood products used and the changes of perioperative hemoglobin (Hb) between groups were analyzed and compared by using Mann-Whitney U test. RESULTS: The results show that the intraoperative CVP changes between GI (n = 35) and GII (n = 49) up to graft procurement were the same, subsequently the blood loss, but ABD resulted in significantly lower perioperative Hb levels in GI. CONCLUSION: Since none of the patients required any blood products perioperatively, all the predonated bloods were discarded after the patients were discharged from the hospital. It indicates that ABD in current series had no any beneficial effects, in term of cost, lowering the CVP, blood loss and reduce the use of banked blood products, but resulted in significant lower Hb in perioperative period.  相似文献   
95.
Microspheres approximately 25 or 50 micrometers in diameter were systemically embolized from the left ventricular cavity. The number of microspheres given was empirically chosen to minimize the possibility of more than one microsphere lodging in an arteriole (3 mg/kg), yet was sufficient to allow for adequate histological assessment. The dogs were sacrificed after 24 hours, and focal areas of myocytolytic necrosis were noted in the myocardium. Groups of dogs were given pretreatment with drugs 10 minutes before embolization. Dogs pretreated with phentolamine (n = 8) and prazosin (n = 2) did not reveal any areas of myocardial necrosis after embolization with 25-micrometers microspheres. Cardiac lesions were also prevented in four of five dogs pretreated with verapamil. In contrast, cardiac lesions were not prevented by pretreatment with yohimbine (n = 2), dipyridamole (n = 3), propranolol (n = 2), or atropine (n = 2). Drug pretreatment with phentolamine or verapamil was not able to prevent cardiac lesions after embolization with 50-micrometers microspheres. Furthermore, despite a greater number of microspheres physically present in the subendocardial layer, the necrotic lesions were more frequent in the mid-wall and epicardial layers. Lesions produced by 25- or 50-micrometers emboli were also significantly smaller in the endocardium. Systemic embolization with microspheres excluding the coronary circulation did not produce cardiac lesions. We conclude that mechanical interruption of the coronary circulation with a 25-micrometers microsphere may be a necessary but not sufficient condition to produce cardiac necrosis. An alpha 1-adrenergic mechanism is also involved in the production of these lesions.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
96.
A woman who was positive for anti-hepatitis B surface antigen (anti-HBs) and anti-hepatitis B core antigen (anti-HBc) received an orthotopic liver transplantation from an anti-HBc-seropositive donor in November 1985. Reappearance of hepatitis B surface antigen (HBsAg) was noted 5 months after the transplantation, but it was not associated with significant liver inflammation. Ten years after the transplantation, results of serum hepatitis B virus (HBV) DNA study, by nested polymerase chain reaction, were negative. However, HBV DNA was detected in the transplanted liver tissues and peripheral blood mononuclear cells. Different strains were identified in these two organs. An adw strain was found in the transplanted liver, whereas an adr strain with long segment deletions in the core gene was found in the peripheral blood mononuclear cells. Covalently closed circular HBV DNA was not detected in any of the tissues examined. Occult HBV infection in the donor as well as the recipient is common in HBV endemic areas. The recipient in this case had reappearance of hepatitis B surface antigen (HBsAg) in the serum after transplantation. Nevertheless, 10 years later, two different strains of HBV were identified in different organs, without cross infection. The present case demonstrates that HBsAg reappearance was not associated with reactivation of the virus and liver inflammation. This type of HBsAg reappearance did not appear to produce a significant hazard to the transplanted liver. Received: December 16, 1999 / Accepted: May 26, 2000  相似文献   
97.
ObjectivesThe efficacy of thrombolytic therapy with tissue plasminogen activator (tPA) is highly time dependent. Although clinical guidelines do not recommend written informed consent as it may cause treatment delays, local policy can supersede and require it. From 2014 to 2017, three out of five public hospitals in Singapore changed from written to verbal consent at different time points. We aimed to examine the association of hospital policy changes regarding informed consent on door-to-needle (DTN) times.Materials and MethodsUsing data from the Singapore Stroke Registry and surveys of local practice, we analyzed data of 915 acute ischemic stroke patients treated with tPA within 3 hours in all public hospitals between July 2014 to Dec 2017. Patient-level DTN times before and after policy changes were examined while adjusting for clinical characteristics, within-hospital clustering, and trends over time.ResultsPatient characteristics and stroke severity were similar before and after the policy changes. Overall, the median DTN times decreased from 68 to 53 minutes after the policy changes. After risk adjustment, changing from written to verbal informed consent was associated with a 5.6 minutes reduction (95% CI 1.1-10.0) in DTN times. After the policy changed, the percentage of patients with DTN ≤60 minutes and ≤45 minutes increased from 35.6% to 66.1% (adjusted OR 1.75; 95% CI 1.12-2.74) and 9.3% to 36.0% (adjusted OR 2.42; 95% CI 1.37-4.25), respectively.ConclusionChanging from written to verbal consent is associated with significant improvement in the timeliness of tPA administration in acute ischemic stroke.  相似文献   
98.
Background: Seasons affect many social, economic, and biological outcomes, particularly in low-resource settings, and some studies suggest that birth season affects child growth.

Aim: To study a predictor of stunting that has received limited attention: birth season.

Subjects and methods: This study uses cross-sectional data collected during 2008 in a low-resource society of horticulturists-foragers in the Bolivian Amazon, Tsimane’. It estimates the associations between birth months and height-for-age Z-scores (HAZ) for 562 girls and 546 boys separately, from birth until age 11?years or pre-puberty, which in this society occurs ~13–14?years.

Results: Children born during the rainy season (February–May) were shorter, while children born during the end of the dry season and the start of the rainy season (August–November) were taller, both compared with their age–sex peers born during the rest of the year. The correlations of birth season with HAZ were stronger for boys than for girls. Controlling for birth season, there is some evidence of eventual partial catch-up growth, with the HAZ of girls or boys worsening until?~?age 4–5?years, but improving thereafter. By age 6?years, many girls and boys had ceased to be stunted, irrespective of birth season.

Conclusion: The results suggest that redressing stunting will require attention to conditions in utero, infancy and late childhood.  相似文献   
99.
100.
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