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   24213篇
  免费   1800篇
  国内免费   79篇
耳鼻咽喉   397篇
儿科学   838篇
妇产科学   377篇
基础医学   2468篇
口腔科学   549篇
临床医学   2165篇
内科学   5316篇
皮肤病学   667篇
神经病学   1294篇
特种医学   1117篇
外国民族医学   1篇
外科学   4630篇
综合类   333篇
一般理论   15篇
预防医学   1180篇
眼科学   823篇
药学   2104篇
中国医学   43篇
肿瘤学   1775篇
  2023年   229篇
  2022年   408篇
  2021年   998篇
  2020年   479篇
  2019年   823篇
  2018年   952篇
  2017年   617篇
  2016年   654篇
  2015年   682篇
  2014年   1028篇
  2013年   1200篇
  2012年   1785篇
  2011年   1753篇
  2010年   893篇
  2009年   830篇
  2008年   1332篇
  2007年   1244篇
  2006年   1156篇
  2005年   1008篇
  2004年   903篇
  2003年   774篇
  2002年   671篇
  2001年   589篇
  2000年   556篇
  1999年   491篇
  1998年   164篇
  1997年   140篇
  1996年   145篇
  1995年   152篇
  1994年   121篇
  1993年   104篇
  1992年   271篇
  1991年   291篇
  1990年   256篇
  1989年   217篇
  1988年   215篇
  1987年   221篇
  1986年   192篇
  1985年   179篇
  1984年   113篇
  1983年   130篇
  1982年   87篇
  1981年   72篇
  1980年   62篇
  1979年   133篇
  1978年   79篇
  1977年   72篇
  1974年   65篇
  1973年   88篇
  1970年   59篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Background: This is the second of two papers using qualitative methods from a study of an intervention for family members affected by close relatives' substance misuse problems.

Participants: 168 primary healthcare professionals (PHCPs: GPs, practice nurses and health visitors) working in general practices in two areas of England, and who took part in the study.

Data sources: Recruitment and post-session forms completed by PHCPs; telephone interviews with each PHCP 12 weeks after recruitment of a family member; interviews with PHCPs at the end of the study.

Results: At the end of the project PHCPs were overwhelmingly positive about the family member intervention and about primary care as the appropriate site. Difficulties were encountered, however, in identifying and engaging affected family members, who were often excluded on grounds of the complexity of their problems or the level of their distress. Shortage of PHCP time and other practice-related factors added to the difficulty. Active work by a PHCP was often necessary in order to make the link between presenting symptoms of physical or mental ill-health and the existence of a family substance misuse problem. When family members were identified and recruited, PHCPs were usually positive about what was achieved. Nearly all were in favour of an approach that combined giving a self-help manual with some follow-up contact with a family member as needed.

Conclusions: Taken in conjunction with statistical outcome findings of significant reductions in symptoms and changes in ways of coping, plus qualitative analysis of the views of family members, the present results encourage the view that a flexible form of this intervention should be developed for use in primary healthcare, and that further work should build on existing strengths and attempt to overcome weaknesses identified.  相似文献   
3.
PURPOSE: Bevacizumab, a monoclonal antibody against vascular endothelial growth factor, increases survival when combined with irinotecan-based chemotherapy in first-line treatment of metastatic colorectal cancer (CRC). This randomized, phase II trial compared bevacizumab plus fluorouracil and leucovorin (FU/LV) versus placebo plus FU/LV as first-line therapy in patients considered nonoptimal candidates for first-line irinotecan. PATIENTS AND METHODS: Patients had metastatic CRC and one of the following characteristics: age > or = 65 years, Eastern Cooperative Oncology Group performance status 1 or 2, serum albumin < or = 3.5 g/dL, or prior abdominal/pelvic radiotherapy. Patients were randomly assigned to FU/LV/placebo (n = 105) or FU/LV/bevacizumab (n = 104). The primary end point was overall survival. Secondary end points were progression-free survival, response rate, response duration, and quality of life. Safety was also assessed. RESULTS: Median survival was 16.6 months for the FU/LV/bevacizumab group and 12.9 months for the FU/LV/placebo group (hazard ratio, 0.79; P = .16). Median progression-free survival was 9.2 months (FU/LV/bevacizumab) and 5.5 months (FU/LV/placebo); hazard ratio was 0.50; P = .0002. Response rates were 26.0% (FU/LV/bevacizumab) and 15.2% (FU/LV/placebo) (P = .055); duration of response was 9.2 months (FU/LV/bevacizumab) and 6.8 months (FU/LV/placebo); hazard ratio was 0.42; P = .088. Grade 3 hypertension was more common with bevacizumab treatment (16% v 3%) but was controlled with oral medication and did not cause study drug discontinuation. CONCLUSION: Addition of bevacizumab to FU/LV as first-line therapy in CRC patients who were not considered optimal candidates for first-line irinotecan treatment provided clinically significant patient benefit, including statistically significant improvement in progression-free survival.  相似文献   
4.
5.
6.
BackgroundMesenteric internal hernia (MIH) is the most common cause of small bowel obstruction (SBO) after laparoscopic Roux-en-Y gastric bypass. Because MIH is a potentially life-threatening complication, we hypothesized that elective repair of MIH before developing acute SBO could decrease morbidity in this population.MethodsThe records of 702 consecutive patients undergoing primary laparoscopic Roux-en-Y gastric bypass from January 2002 and August 2007 were retrospectively reviewed to determine the incidence and etiology of SBO. During the last 9 months of the study, we offered elective laparoscopy to any patient who presented to us with symptoms of intermittent SBO.ResultsOf the 702 patients, 27 (3.8%) developed acute SBO. Of these 27 patients, 15 (55%) had obstruction related to an MIH. Nearly all patients had a typical history of intermittent abdominal pain, nausea, and bloating before developing acute SBO. Elective laparoscopy was offered to 11 patients with symptoms of intermittent SBO. Two patients who refused subsequently underwent operations for acute SBO. MIH was found at elective laparoscopic exploration in all cases. Of the 9 patients undergoing elective surgery, 3 (33%) had small bowel volvulus.ConclusionSBO due to MIH after laparoscopic Roux-en-Y gastric bypass is typically preceded by symptoms of intermittent obstruction. Patients who have these herald symptoms should promptly be offered elective laparoscopic exploration. Elective repair of MIH can be performed safely and expeditiously.  相似文献   
7.
Using fura-2 loaded neural tumour cells, SK-N-SH, we demonstrate that receptor-mediated activation of phosphoinositide hydrolysis not only causes the release of Ca2+ from intracellular stores but also causes a concomitant influx of extracellular Ca2+. Thapsigargin (TG), a sesquiterpene lactone, causes a sustained elevation of intracellular Ca2+ and depletion of the inositol 1, 4, 5-trisphosphate-sensitive intracellular Ca2+ stores. In the absence of extracellular Ca2+, the increase in intracellular Ca2+ concentration ([Ca2+]i) was transient, suggesting that thapsigargin activates both intracellular mobilization and the influx of Ca2+ from extracellular space. These results are consistent with the proposal that the depletion of the inositol 1, 4, 5-trisphosphate-sensitive intracellular Ca2+ pool serves as a signal for Ca2+ influx.  相似文献   
8.
Brain metastasis is the most common intracranial malignancy in adults. Improvements in modern imaging techniques are detecting previously occult brain metastases, and more effective therapies are extending the survival of patients with invasive cancer who have historically died from extracranial disease before developing brain metastasis. This combination of factors along with increased life expectancy has led to the increased diagnosis of brain metastases. Conventional treatment has been whole brain radiotherapy, which can improve symptoms, but potentially results in neurocognitive deficits. Several strategies to improve the therapeutic ratio are currently under investigation to either enhance the radiation effect, thereby preventing tumor recurrence or progression as well as reducing collateral treatment-related brain injury. In this review article, we discuss new directions in the management of brain metastases, including the role of chemical modifiers, novel systemic agents, and the management and prevention of neurocognitive deficits.  相似文献   
9.
10.
Akt, a Serine/Threonine protein kinase, mediates growth factor-associated cell survival. Constitutive activation of Akt (phosphorylated Akt, P-Akt) has been observed in several human cancers, including lung cancer and may be associated with poor prognosis and chemotherapy and radiotherapy resistance. The clinical relevance of P-Akt in non-small cell lung cancer (NSCLC) is not well described. In the present study, we examined 82 surgically resected snap-frozen and paraffin-embedded stage I to IIIA NSCLC samples for P-Akt and Akt by Western blotting and for P-Akt by immunohistochemistry. P-Akt protein levels above the median, measured using reproducible semiquantitative band densitometry, correlated with a favorable outcome (P = 0.007). Multivariate analysis identified P-Akt as a significant independent favorable prognostic factor (P = 0.004). Although associated with a favorable prognosis, high P-Akt levels correlated with high tumor grade (P = 0.02). Adenocarcinomas were associated with low P-Akt levels (P = 0.039). Akt was not associated with either outcome or clinicopathologic variables.Cytoplasmic (CP-Akt) and nuclear (NP-Akt) P-Akt tumor cell staining was detected in 96% and 42% of cases, respectively. Both CP-Akt and NP-Akt correlated with well-differentiated tumors (P = 0.008 and 0.017, respectively). NP-Akt also correlated with nodal metastases (P = 0.022) and squamous histology (P = 0.037).These results suggest P-Akt expression is a favorable prognostic factor in NSCLC. Immunolocalization of P-Akt, however, may be relevant as NP-Akt was associated with nodal metastases, a known poor prognostic feature in this disease. P-Akt may be a potential novel therapeutic target for the management of NSCLC.  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