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   178002篇
  免费   1104篇
  国内免费   31篇
耳鼻咽喉   1196篇
儿科学   6764篇
妇产科学   3149篇
基础医学   16649篇
口腔科学   1707篇
临床医学   12598篇
内科学   31343篇
皮肤病学   728篇
神经病学   16591篇
特种医学   8991篇
外科学   29275篇
综合类   2342篇
现状与发展   1篇
一般理论   4篇
预防医学   18320篇
眼科学   2834篇
药学   9574篇
  1篇
中国医学   637篇
肿瘤学   16433篇
  2023年   38篇
  2022年   93篇
  2021年   126篇
  2020年   84篇
  2019年   126篇
  2018年   22015篇
  2017年   17429篇
  2016年   19602篇
  2015年   1026篇
  2014年   933篇
  2013年   949篇
  2012年   7176篇
  2011年   21206篇
  2010年   18910篇
  2009年   11609篇
  2008年   19651篇
  2007年   21824篇
  2006年   689篇
  2005年   2300篇
  2004年   3527篇
  2003年   4436篇
  2002年   2598篇
  2001年   313篇
  2000年   436篇
  1999年   182篇
  1998年   203篇
  1997年   209篇
  1996年   94篇
  1995年   100篇
  1994年   98篇
  1993年   61篇
  1992年   43篇
  1991年   96篇
  1990年   129篇
  1989年   80篇
  1988年   56篇
  1987年   45篇
  1986年   29篇
  1985年   33篇
  1983年   27篇
  1982年   25篇
  1980年   40篇
  1974年   23篇
  1969年   25篇
  1938年   60篇
  1937年   25篇
  1935年   22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 10 毫秒
111.

Background  

Induction of apoptosis is one strategy for treatment of prostate cancer. The Shb adapter protein has been found to regulate apoptosis in various cell types and consequently human prostate cancer 3 (PC3) cells were transfected to obtain cells overexpressing Shb in order to increase our understanding of the mechanisms regulating PC3 cell apoptosis.  相似文献   
112.
113.
114.
Objective The purpose of this study is to analyze clinical aspects and disease-free survival (DFS) in children less than 3 years of age diagnosed with low-grade astrocytoma. Methods In a period of 24 years (1980–2004), a total of 43 (5.4%) children were registered with these characteristics. Twenty-three patients had pilocytic astrocytoma, 18 diffused, and 2 mixed. Thirty-one (72.1%) children had incomplete surgical tumor resection and 12 (27.9%) had a complete tumor resection. Twelve (27.9%) patients had cranial radiotherapy and 17 (39.5%) received chemotherapy. Overall survival was recorded in 23 (53%). DFS was 50% at 250 months of follow-up for the whole group. DFS for the supratentorial group was 60% at 250 months, whereas, for the infratentorial, it was 22% at 120 months (p = 0.008). Conclusion The only favorable prognostic pattern was the supratentorial presentation. Radiotherapy and chemotherapy did not alter the outcome.  相似文献   
115.
Previously reported attenuation of skin postural vasoconstriction in women during the luteal menstrual cycle phase may be due to a progesterone-mediated decrease in myogenic or veno-arteriolar (VAR) mechanisms. Skin perfusion was measured in the shin and foot dorsum by Laser Doppler Fluxometry during leg dependency that increased vascular transmural pressure below (myogenic constriction only) and above (myogenic and VAR) the 25 mmHg threshold for activation of the VAR, and during venous distension to activate the VAR alone (cuff inflation to 50 mmHg). In six young women with normal menstrual cycles, vasoconstrictor responses to all interventions did not differ between days 7–13 (follicular) and 18–23 (luteal) of the normal menstrual cycle when progesterone levels were low and at their peak respectively. In eight women taking combined oral contraceptives (OC) and tested during pill consumption days, reductions in foot skin perfusion were smaller (P = 0.05) than in the luteal phase of the normal cycle for leg dependency below (−36.9 ± 5.2% OC vs. −52.5 ± 7.8% luteal, mean ± S.E.M.) and above (−43.7 ± 3.4% OC vs. −55.1 ± 4.8% luteal) the VAR threshold, and for venous distension (−53.1 ± 2.6% OC vs. 66.4 ± 5.5% luteal). In women with normal menstrual cycles, impaired postural vasoconstriction may be confined to those who experience pre-menstrual symptoms rather than a direct effect of endogenous hormones. Reduced vasoconstriction in the dependent foot during OC use is consistent with the known vasodilator action of exogenous hormones and its long-term effects  相似文献   
116.
Stenosis of the hypopharyngo-oesophageal junction can be a rare complication of laryngectomy and/or partial pharyngectomy and makes the insertion of voice prosthesis extremely difficult. This study describes the authors’ experiences gained by endoscopic balloon-catheter dilatation of hypopharyngo-oesophageal stenoses prior to implantation of voice prostheses in four cases. In two patients a single balloon-catheter dilatation resulted in wide enough pharyngo-oesophageal lumen on the long run. The average prosthesis wearing-times were 6.8 months in case 1 and 4.6 months in case 2, corresponding to the published literature data. In case 3, repeated dilatation of the pharyngo-oesophageal transition had proved to be unsuccessful despite taking every effort with the endoscopic balloon-catheter method. Having excised the stenotic segment, reconstruction with pectoralis major myocutaneous flap (PMMF) was indicated. Eighteen months later, a repeated restenosis was observed and a free jejunal flap needed to be performed as a final solution. In case 4, the insertion was carried out into a previously dilated jejunal free flap, which became gradually ischemic and stenotic since the major head-and neck procedure was carried out that resulted in prosthesis rejection after just 1 week. The authors emphasize that correct indication of pedicled and free flaps in head and neck reconstruction is a prerequisite from the aspect of prevention of pharyngo-oesophageal strictures. Endoscopic balloon-catheter dilatation is a safe and established method for dilatating hypopharyngo-oesophageal stenoses of different origin. The procedure provides maximum patient benefit with minimal trauma and morbidity; moreover, facilitates insertion of voice prostheses. However, a single balloon-catheter dilatation cannot always result in wide enough oesophageal lumen on the long run (case 3). Insertion of a voice prosthesis into a previously dilated ischemic jejunal segment is challenging and avoidable due to risks of complications.  相似文献   
117.
Mathematical modeling of transmission dynamics of sexually transmitted infections (STIs) and HIV has considerably advanced HIV research by highlighting the importance of certain types of partnerships in epidemic spread. Notably, concurrent partnerships, defined as a sexual partnership in which one or more of the partnership members have other sexual partners while continuing sexual activity with the original partner, have been shown to play a fundamental role in potentiating the spread of STIs and HIV. Risk behaviors such as concurrency and sex without condoms as well as STI/HIV prevalence vary with physical, social, and emotional factors within partnerships. The efficiency of STI/HIV transmission appears to vary across types of concurrent partnerships according to the differing dynamics within them. Previous research on partnership dynamics has improved our understanding of the multidimensional aspects of sexual partnering, but little is understood of how these aspects of sexual partnering interact and increase risks for HIV, nor how types of partnerships, partnership dynamics, and concurrency work together to affect both the behavior of condom use and the biological transmission of disease. In this article, we discuss the need to extend our understanding of concurrency to include partnerships among men who have sex with men (MSM) and to differentiate between types of partnerships and to develop interventions to modify risk within partnerships. We also introduce a conceptual framework that reflects how individual and partner characteristics influence partnership dynamics that in turn influence risk behaviors, such as concurrency and not using condoms, and associated risks for STIs and HIV.  相似文献   
118.
Background Sympathectomy is the treatment of choice for primary hyperhidrosis. One curious occurrence that is difficult to explain from an anatomophysiological point of view in cases of video-assisted thoracoscopic sympathectomy (VATS) for the treatment of palmar hyperhidrosis (PH) is the observed improvement in plantar hyperhidrosis (PLH). Nevertheless, current reports on VATS rarely describe the effect on PLH or just give superficial data. The aim of this study was to prospectively investigate, how surgery affects PLH in patients with PH and PLH over one-year period. Methods From May 2003 to January 2004, 70 consecutive patients with combined PH and PLH underwent VATS at the T2, T3, or T4 ganglion level (47 women and 23 men, with mean age of 23 years). Results Immediately after the operation, all the patients said they were free from PH episodes, except for two patients (2.8%) who suffered from continued PH. Compensatory hyperhidrosis (CH) of various degrees was observed in 58 (90.6%) patients after one year. Only 13 (20.3%) suffered from severe CH. There was a great initial improvement in PLH in 50% of the cases, followed by progressive regression, such that only 23.4% still presented that improvement after one year. The number of cases without overall improvement increased progressively (from 17.1% to 37.5%) and the numbers with slight improvement remained stable (32.9–39.1%). Of the 24 patients with no improvement after one year, 6 patients graded plantar sweating worse. Conclusion Patients with PH and PLH who undergo VATS to treat their PH present a good initial improvement in PLH that reduces to a lower level of improvement after the one-year period.  相似文献   
119.
Cholecystokinin (CCK )isa polypeptidehor monecontaining 33aminoacidsresiduewithgastroin testinal,biliarandbrainactivities Itiswidelydis tributedinthevertebratecentralnervoussystem ,anditcanstimulateextensivelytheliberationofinsulinandglucagonfromtheLangerhansislets GreateffortshavebeendevotedtothesynthesisofCCK 8,itsderivativesandanalogues Amongthedifferentmethods ,theenzymaticmethodisthemosteffectiveonewithmanyadvantagesoverconventionalchemicalmethodologies :enzymespecificitysuppress essid…  相似文献   
120.
Epiploic appendagitis and omental infarction: pitfalls and look-alikes   总被引:3,自引:0,他引:3  
Epiploic appendagitis and omental infarction are benign self-limiting conditions that are more frequent than generally assumed. Both disorders frequently mimic symptoms of an abdominal surgical emergency, often leading to clinical misdiagnosis of appendicitis or diverticulitis. Because a misdiagnosis can result in an unnecessary laparotomy, a correct diagnosis is of great importance. Ultrasound and computed tomography can be used to make a reliable diagnosis. This pictorial essay illustrates the various ultrasonographic and computed tomographic appearances of epiploic appendagitis and omental infarction and focuses on their radiologic differential diagnoses and pitfalls. Received: 22 February 2001/Accepted: 18 April 2001  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