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   3444篇
  免费   123篇
  国内免费   13篇
耳鼻咽喉   42篇
儿科学   43篇
妇产科学   43篇
基础医学   556篇
口腔科学   24篇
临床医学   418篇
内科学   699篇
皮肤病学   37篇
神经病学   290篇
特种医学   136篇
外科学   484篇
综合类   4篇
一般理论   1篇
预防医学   185篇
眼科学   32篇
药学   309篇
中国医学   6篇
肿瘤学   271篇
  2024年   2篇
  2023年   9篇
  2022年   29篇
  2021年   94篇
  2020年   24篇
  2019年   54篇
  2018年   77篇
  2017年   56篇
  2016年   47篇
  2015年   73篇
  2014年   78篇
  2013年   117篇
  2012年   263篇
  2011年   260篇
  2010年   134篇
  2009年   137篇
  2008年   247篇
  2007年   256篇
  2006年   282篇
  2005年   255篇
  2004年   242篇
  2003年   206篇
  2002年   212篇
  2001年   35篇
  2000年   24篇
  1999年   23篇
  1998年   48篇
  1997年   41篇
  1996年   28篇
  1995年   35篇
  1994年   20篇
  1993年   25篇
  1992年   21篇
  1991年   6篇
  1990年   12篇
  1989年   13篇
  1988年   23篇
  1987年   10篇
  1986年   14篇
  1985年   6篇
  1984年   12篇
  1983年   7篇
  1982年   4篇
  1981年   4篇
  1980年   4篇
  1979年   1篇
  1978年   1篇
  1977年   6篇
  1974年   2篇
  1966年   1篇
排序方式: 共有3580条查询结果,搜索用时 31 毫秒
991.
992.
Context  Septic shock may be associated with relative adrenal insufficiency. Thus, a replacement therapy of low doses of corticosteroids has been proposed to treat septic shock. Objective  To assess whether low doses of corticosteroids improve 28-day survival in patients with septic shock and relative adrenal insufficiency. Design and Setting  Placebo-controlled, randomized, double-blind, parallel-group trial performed in 19 intensive care units in France from October 9, 1995, to February 23, 1999. Patients  Three hundred adult patients who fulfilled usual criteria for septic shock were enrolled after undergoing a short corticotropin test. Intervention  Patients were randomly assigned to receive either hydrocortisone (50-mg intravenous bolus every 6 hours) and fludrocortisone (50-µg tablet once daily) (n = 151) or matching placebos (n = 149) for 7 days. Main Outcome Measure  Twenty-eight-day survival distribution in patients with relative adrenal insufficiency (nonresponders to the corticotropin test). Results  One patient from the corticosteroid group was excluded from analyses because of consent withdrawal. There were 229 nonresponders to the corticotropin test (placebo, 115; corticosteroids, 114) and 70 responders to the corticotropin test (placebo, 34; corticosteroids, 36). In nonresponders, there were 73 deaths (63%) in the placebo group and 60 deaths (53%) in the corticosteroid group (hazard ratio, 0.67; 95% confidence interval, 0.47-0.95; P = .02). Vasopressor therapy was withdrawn within 28 days in 46 patients (40%) in the placebo group and in 65 patients (57%) in the corticosteroid group (hazard ratio, 1.91; 95% confidence interval, 1.29-2.84; P = .001). There was no significant difference between groups in responders. Adverse events rates were similar in the 2 groups. Conclusion  In our trial, a 7-day treatment with low doses of hydrocortisone and fludrocortisone significantly reduced the risk of death in patients with septic shock and relative adrenal insufficiency without increasing adverse events.   相似文献   
993.
Targeting interleukin-1 in the treatment of rheumatoid arthritis   总被引:4,自引:0,他引:4  
  相似文献   
994.
Peripheral blood mononuclear cells from HIV-1-infected subjects secrete spontaneously in vitro immunoglobulins (Ig) and anti-HIV-1 antibodies (Ab). Purified B lymphocytes secrete only minute amounts of Ig and anti-HIV-1 Ab compared with unfractionated cells. Monocytes and natural killer cells enhanced both secretions by cell-to-cell contacts, involving adhesion and CD27, CD80 costimulatory molecules and IL-6. Cell interactions prolonged the survival and allowed the terminal maturation of in vivo activated B cells. The secreting cell precursors were highly differentiated B cells expressing a broad diversity of maturation markers (CD27(+), CD38(+), CD20(+/-), CD37(+/-), CD71(+/-), HLA-DQ(+/-), sIg(+/-)) but not sIgD, CD28, or CD40. This phenotype and the cytologic aspect of purified B cells suggest that these cells are early plasma cells originated from germinal center. Ex vivo secreting peripheral B cells had probably gone beyond the CD40/CD40 ligand interaction; then following CD28/CD80 and CD27/CD27 ligand (CD70) interactions in the presence of IL-6, they achieved in vitro their differentiation into plasma cells.  相似文献   
995.
This study was conducted to determine the maximum tolerated dose of an intensified MAID (mesna, adriamycin, ifosfamide, dacarbazine) regimen with the support of lenograstim in patients with advanced soft tissue sarcomas. Following 1 cycle of MAID at the standard dose, four patients were to be treated at each of five dosage levels: +25%, +45%, +65%, +85%, +100%. Sixteen patients were treated. Because there were no significant differences in hematologic toxicity between patients receiving lenograstim 5 or 10 microg/kg/day (levels 1-5 and 1-10), the data were pooled for comparison with level 2. The median duration of absolute neutrophil count < 0.5 x 10(9)/l was 3 days at level 1 and 7 days at level 2 (p < 0.01). The median platelet nadir was 25 x 10(9)/l at level 1 and 10 x 10(9)/l at level 2 (p < 0.01). The median duration of toxicity-related hospitalization was 3.5 days and 11 days at levels 1 and 2, respectively, (p < 0.001). Mucositis > or = grade III occurred after 3/29 cycles at level 1 and 10/15 cycles at level 2 (p < 0.001). After 4 cycles at level 1, 8/8 patients still had performance status scores < or = 2, and only 4/8 had performance status scores < or = 2 after the second cycle at level 2. Lenograstim enabled an increase of 25% of the MAID regimen. At higher dose levels, severe mucositis and deterioration in performance status were dose limiting.  相似文献   
996.
Nasal and sinus polyposis in the pediatric population is uncommon and its etiology is unclear. In this 11-year retrospective study, the authors describe the etiologic features and evaluate the effectiveness of endoscopic sinus surgery in 46 children. Patients were divided into three groups according to whether nasal and sinus polyposis was isolated (n = 14), or associated with either asthma (n = 5) or cystic fibrosis (n = 27). An allergy was present in 10% of patients with isolated polyposis, 80% of patients with polyposis associated with asthma, and 22% of patients with polyposis associated with cystic fibrosis. The indications for surgery were disabling symptoms, especially chronic nasal obstruction, rhinorrhea, and mouth breathing, and failure to respond to medical treatment. No surgical complications were encountered. Most patients reported improvement in quality of life with reduction of nasal obstruction in 83% of cases and rhinorrhea in 61%. Minor asymptomatic recurrence (i.e., a few micropolyps localized on the roof of the ethmoid cavity) was observed in 24% of the cases in this series, and major recurrence with the same functional symptoms as before surgery in 12%. However, recurrences were higher in patients with cystic fibrosis, because minor recurrence with no clinical manifestation was observed in 32% of these cases and major recurrence in 16%. Endoscopic sinus surgery must be decided in collaboration with the pediatric and pulmonary physicians, and must be performed skillfully. With a mean follow-up of 3.7 years, results in this series are encouraging.  相似文献   
997.
LND-623 is a new aminosteroid analog of ouabain, with a greater separation between efficacy and toxicity than ouabain. To determine its mechanism of action, we studied its biochemical and physiological effects on human red blood cell sodium transports on different cellular structures regarded as sites of contractile control, and we compared its relative efficacy to ouabain in rat heart preparations and membrane-bound Na, K-ATPase isoenzymes. The response to ouabain was evaluated in Langendorff-perfused hearts and on purified membrane-bound Na, K-ATPase. LND-623 is 6.8-fold more efficient than ouabain in inhibiting the human Na+ pump (IC50= 0.098 ± 0.001 M vs. 0.67 ± 0.02 M); (P < 0.0001). LND-623 had no effect on the following cellular functions: Na-Ca exchange, Na-K cotransport, Ca-ATPase, slow calcium channels, adenylate cyclase system, phosphodiesterase, and calcium sensitivity of the contractile protein system. The dose–response curve for the positive inotropic and inhibitory effects on rat cardiac isoenzymes produced by LND-623 were clearly biphasic. The amplitude of the maximum inotropic effect, without any toxic effect, was up to three-fold higher with LND-623 than with the same maximum dose of ouabain used. The strong positive inotropic effect of LND-623 in rats could be related to a specific inhibition of the two rat cardiac isoforms of the Na, K-ATPase.  相似文献   
998.
BACKGROUND: Animal studies have shown that neuroactive steroids modulate the activity of the gamma-aminobutyric acid type A/benzodiazepine receptor complex and that these steroids display anxiolytic or anxiogenic activity depending on their positive (e.g. allopregnanolone) or negative allosteric modulation (e.g. dehydroepiandrosterone sulphate) of this receptor. This study compared plasma levels of allopregnanolone, dehydroepiandrosterone sulphate and pregnenolone sulphate in healthy controls and in patients with generalized social phobia, as assessed with the Mini-International Neuropsychiatric Interview. METHODS: Plasma concentrations of allopregnanolone, pregnenolone sulphate, and dehydroepiandrosterone sulphate were measured in 12 unmedicated male patients with generalized social phobia and 12 matched healthy male volunteers. RESULTS: Concentrations of pregnenolone sulphate were significantly lower in patients with generalized social phobia than in healthy controls. No statistically significant differences were found for the concentrations of allopregnanolone and dehydroepiandrosterone sulphate in plasma. CONCLUSIONS: These results are particularly interesting since we also observed lower pregnenolone sulphate concentrations in male patients suffering from generalized anxiety disorder. Their relevance to the pathophysiology of social anxiety disorder remains to be determined.  相似文献   
999.
Sequence analysis of a transcribed region of the wheat mitochondrial (mt) genome revealed two open reading frames (orfs) coding for proteins of 589 and 174 amino acids. Both genes are co-transcribed in a 2.6-kb RNA. The largest orf codes for a hydrophobic protein which bears similarity to a bacterial protein involved in the biogenesis of c-type cytochromes. Its corresponding RNA sequence is fully edited at 34 positions. The second orf encodes a protein homologous to the amino-terminal third of E. coli ribosomal protein S1, corresponding to the ribosome-binding domain of this protein. Its RNA sequence is edited at four positions, one of the edits creating a stop codon. The presence of both proteins in wheat mitochondria was demonstrated using specific antibodies raised against fusion proteins obtained in E. coli from the corresponding cDNAs.  相似文献   
1000.
We have reviewed cytopathology and the corresponding histopathology material of 86 liposarcomas (55 patients) seen at Institut Curie. The liposarcomas (LS) were well differentiated in 14 cases (9 pure, 2 dedifferentiated, 3 sclerosing), 64 myxoid, and 8 pleomorphic. Twenty-four tumors were primary, 34 recurrent, and 28 secondary. Smears in LS were composed in different proportions of round, spindle cells, lipoblasts, and myxoid and vascular arborizing structures. Pure well-differentiated LS were frequently composed of lipoblasts, and round or spindle cells were occasionally seen. Dedifferentiated and sclerosing liposarcomas were composed of spindle or round cells, but lipoblasts were also occasionally present. Myxoid or vascular arborizing structures were absent. Myxoid LS (including round and spindle cell LS) frequently showed a myxoid background and less frequently vascular arborizing structures. Tumor cells were round or spindle. Lipoblasts were also seen. Pleomorphic LS were composed of an admixture of all cellular and stromal elements. Well-differentiated LS should be distinguished from hibernoma and spindle cell lipoma, and myxoid LS from myxoma, myxoid chondrosarcoma, chordoma, myxoid leiomyosarcoma, and myxoid malignant fibrous histiocytoma. The demonstration of the specific translocation t(12;16)(q13;p11) of myxoid LS is very helpful to establish the diagnosis. Pleomorphic LS should be differentiated from other high-grade sarcomas, whenever possible.  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