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   1562篇
  免费   94篇
  国内免费   4篇
耳鼻咽喉   21篇
儿科学   27篇
妇产科学   78篇
基础医学   160篇
口腔科学   64篇
临床医学   103篇
内科学   438篇
皮肤病学   19篇
神经病学   249篇
特种医学   30篇
外科学   221篇
综合类   5篇
一般理论   3篇
预防医学   89篇
眼科学   42篇
药学   47篇
中国医学   1篇
肿瘤学   63篇
  2023年   4篇
  2022年   14篇
  2021年   20篇
  2020年   23篇
  2019年   22篇
  2018年   29篇
  2017年   33篇
  2016年   31篇
  2015年   26篇
  2014年   46篇
  2013年   52篇
  2012年   81篇
  2011年   79篇
  2010年   52篇
  2009年   60篇
  2008年   78篇
  2007年   117篇
  2006年   96篇
  2005年   103篇
  2004年   90篇
  2003年   103篇
  2002年   125篇
  2001年   19篇
  2000年   14篇
  1999年   18篇
  1998年   25篇
  1997年   24篇
  1996年   22篇
  1995年   15篇
  1994年   17篇
  1993年   13篇
  1992年   21篇
  1991年   16篇
  1990年   16篇
  1989年   8篇
  1988年   8篇
  1987年   5篇
  1986年   10篇
  1985年   12篇
  1984年   13篇
  1983年   17篇
  1982年   8篇
  1981年   19篇
  1980年   12篇
  1978年   7篇
  1977年   9篇
  1975年   3篇
  1974年   4篇
  1973年   5篇
  1972年   5篇
排序方式: 共有1660条查询结果,搜索用时 31 毫秒
31.
32.
33.
A simple reproducible and versatile small animal model for hepatitis B virus (HBV) infection is still unavailable. We have generated a simple transient liver-targeted transgenic mouse. Hydrodynamics tail vein injection of a head-to-tail dimer of adw HBV genome (pHBVadwHTD) into immunocompetent mice generated HBsAg and HBeAg expression in both serum and hepatocytes, followed by seroconversion. The injection of pHBVadwHTD into SCID mice generated prolonged HBsAg and HBeAg antigenemia and HBV viremia. Our results demonstrate that hydrodynamic injection of naked DNA could support the generation of HBV particles. We used this model for the assessment of anti-viral agents. Administration of our human monoclonal antibodies, HBV-Ab17(XTL) and HBV-Ab19(XTL), as well as Lamivudine (3TC) treatment suppressed HBV viremia. The model presented herein supports long and stable expression of HBV and will enable determination of various biological questions related to HBV life cycle, mutants and could enhance the development of anti-viral reagents.  相似文献   
34.
Currently available somatostatin analogs predominantly bind to the somatostatin receptor subtype (SSTR)2 subtype, and control GH and IGF-I secretion in approximately 65% of patients with acromegaly, their efficacy relating to receptor density and subtype expression. SOM230 is a somatostatin ligand with high affinity to four SSTR subtypes. In primary cultures of rat pituicytes, SOM230 dose-dependently inhibited GH release (P = 0.002) with an IC50 of 1.2 nM. Ten nanomoles SOM230 inhibited GH and TSH release by 40 +/- 7% (P < 0.001) and 47 +/- 21% (P = 0.09), respectively. No effect of SOM230 was observed on prolactin (PRL) or LH release. In cultures of human fetal pituitary cells, SOM230 inhibited GH secretion by 42 +/- 9% (P = 0.002) but had no effect on TSH release. SOM230 inhibited GH release from GH-secreting adenoma cultures by 34 +/- 8% (P = 0.002), PRL by 35 +/- 4% from PRL-secreting adenomas (P = 0.01), and alpha-subunit secretion from nonfunctioning pituitary adenomas by 46 +/- 18% (P = 0.34). In contrast, octreotide inhibited GH, PRL, and alpha-subunit from the respective adenoma by 18 +/- 12 (P = 0.39), 22 +/- 4 (P = 0.04), and 20 +/- 10% (P = 0.34). In all culture systems, no significant difference in the inhibitory action of SOM230, octreotide, and somatostatin 14 on hormone release was observed. SOM230, similar to somatostatin, has high-affinity binding to SSTR1, 2, 3, and 5 and, in keeping with this, has an equivalent inhibitory effect on pituitary hormone secretion. As a consequence of its broader binding profile, SOM230 is likely to find clinical utility in treating tumors resistant to SSTR-2-preferential analogs.  相似文献   
35.
Background: Evidence linking cardiovascular risk factors to aortic valve sclerosis (AVS) has led to the assumption that the latter is an atherosclerosis-like process. However, triglyceride (TG)-rich lipoproteins, an important risk factor for atherosclerosis, have been rarely investigated in connection with AVS. Methods: A cross-sectional study of 246 healthy individuals (mean age 59±6 years, 77% men) was conducted. Subjects underwent an echocardiographic assessment and extensive blood lipid measurements, including evaluation of TG-related indices, such as serum apolipoprotein (apo) CII and CIII levels, apo CIII levels in VLDL+LDL particles, and apo CIII ratio (CIII level in HDL/CIII level in VLDL+LDL). Results: Twenty-three patients (9.3%) were diagnosed as having AVS. On average, these patients were 5 years older and had higher levels of serum cholesterol, LDL-C and LP(a), compared with non-AVS subjects. In addition, the AVS patients exhibited higher concentrations of serum apo CII, serum apo CIII and apo CIII in VLDL+LDL, and a lower apo CIII ratio. Adjusting for age and gender, a 1 S.D. increment in apo CIII in VLDL+LDL was associated with odds ratio (OR) of 1.76 (95% CI: 1.17–2.65) for AVS. Further adjustment for atherosclerotic risk factors did not alter the association appreciably (OR=1.65, 95% CI: 1.06–2.58). Conclusion: TG-rich lipoproteins may be involved in the early development of AVS. Confirmation in prospective studies is required.  相似文献   
36.

Essentials

  • Strong P2Y12 blockade may cause platelet inhibition that is only minimally enhanced by aspirin.
  • We evaluated aspirin withdrawal on platelet reactivity in ticagrelor treated patients.
  • Aspirin withdrawal resulted in increased platelet reactivity to arachidonic acid.
  • Aspirin withdrawal caused little difference in adenosine diphosphate‐induced platelet aggregation.

Summary

Background

Recent studies have shown that the thromboxane A2‐dependent pathway is dependent on the ADP–P2Y12 pathway, and that strong P2Y12 receptor blockade alone causes inhibition of platelet aggregation that is minimally enhanced by aspirin. Data from the PLATO trial suggested that, among ticagrelor‐treated patients, high‐dose versus low‐dose (< 100 mg day?1) aspirin is associated with an increased risk fof ischemic events.

Objectives

To evaluate the impact of aspirin withdrawal on platelet reactivity in acute coronary syndrome (ACS) patients treated with a potent P2Y12 blocker.

Patients/Methods

This was a current prospective, randomized, placebo‐controlled, double‐blind, cross‐over study. The study population comprised 22 consecutive ACS patients who underwent percutaneous coronary intervention and were treated with aspirin (100 mg day?1) and ticagrelor. Thirty days post‐ACS, open‐label aspirin was stopped, and patients were randomized to either blinded aspirin or placebo for 2 weeks, with each patient crossing over to the other arm for an additional 2 weeks. Platelet reactivity to arachidonic acid and ADP determined with light‐transmission aggregometry (LTA) and VerifyNow was evaluated at baseline, and 2 weeks and 4 weeks later.

Results

Aspirin withdrawal resulted in an increase in arachidonic‐acid induced platelet reactivity as determined with both LTA (77.0% ± 11.3% versus 20.8% ± 4.4%) and VerifyNow (607.7 ± 10.6 aspirin reaction units [ARU] versus 408.5 ± 14.4 ARU). Platelet response to ADP, as determined with both LTA and VerifyNow, did not differ with either aspirin or placebo (32.9% ± 2.6% versus 35.8% ± 3.6%, and 33.5 ± 6.4 P2Y12 reaction units (PRU) versus 29.6 ± 5.7 PRU, respectively).

Conclusions

Aspirin withdrawal early post‐ACS results in increased platelet reactivity in response to arachidonic acid, despite concomitant treatment with the potent P2Y12 blocker ticagrelor.
  相似文献   
37.
Long-term primary cultures were established fromfetal or neonatal livers by using cell suspensionsdepleted of red blood cells and by culturing the cellsin hormonally defined medium containing dimethyl sulfoxide. Two distinct populations of hepaticprogenitor cells were evident in the cultures, based onmorphology, proliferative ability, and liver-specificgene expression. Most colonies consisted of immature hepatic progenitors: small, blastlike cells,weakly expressing alpha-fetoprotein, albumin, and-glutamyltranspeptidase, and showing evidence ofproliferation as measured by bromodeoxyuridineincorporation. At the perimeter of these colonies of immaturecells and forming some colonies by themselves were moremature hepatic progenitor cells: larger cells, withincreased cytoplasmic to nuclear ratios, little proliferation, and strongly expressing albumin,alpha-fetoprotein, and -glutamyltranspeptidase.The latter two proteins were localized to the bilecanalicular membranes of these cells. Glycogen deposits were present in the mature cells from day 14embryos after eight days of culture. Thus, DMSOtreatment of hepatic parenchymal progenitors provides anovel system for studies of liver development.  相似文献   
38.
OBJECTIVE: The recently introduced Bayer wide‐range C‐reactive protein (wr‐CRP) assay might be relevant for the real‐time low‐cost and online determination of inflammatory bowel disease (IBD) activity. Our aim was to examine whether wr‐CRP can substitute for the Dade Behring high sensitivity C‐reactive protein (hs‐CRP) assay in IBD patients. METHODS: A total of 71 patients with IBD, of whom 48 had Crohn's disease CD and 23 had ulcerative colitis (UC) with various intensities of disease activity participated in the study. The CRP of patients who were under treatment at the Department of Gastroenterology and Liver Diseases were measured using both wr‐CRP and the hs‐CRP. RESULTS: A significant (r = 0.995; P < 0.001) correlation was noted between the hs‐CRP and wr‐CRP measurements for the whole sample as well as for the two diseases, CD (r = 0.994; P < 0.001) and UC (r = 0.997; P < 0.001), which were analyzed separately. CONCLUSION: The Bayer wr‐CRP assay might be a useful low‐cost and real‐time inflammation‐sensitive biomarker in patients with IBD.  相似文献   
39.
BACKGROUNDPatients with p16+ oropharyngeal squamous cell carcinoma (OPSCC) are potentially cured with definitive treatment. However, there are currently no reliable biomarkers of treatment failure for p16+ OPSCC. Pathologist-based visual assessment of tumor cell multinucleation (MN) has been shown to be independently prognostic of disease-free survival (DFS) in p16+ OPSCC. However, its quantification is time intensive, subjective, and at risk of interobserver variability.METHODSWe present a deep-learning–based metric, the multinucleation index (MuNI), for prognostication in p16+ OPSCC. This approach quantifies tumor MN from digitally scanned H&E-stained slides. Representative H&E-stained whole-slide images from 1094 patients with previously untreated p16+ OPSCC were acquired from 6 institutions for optimization and validation of the MuNI.RESULTSThe MuNI was prognostic for DFS, overall survival (OS), or distant metastasis–free survival (DMFS) in p16+ OPSCC, with HRs of 1.78 (95% CI: 1.37–2.30), 1.94 (1.44–2.60), and 1.88 (1.43–2.47), respectively, independent of age, smoking status, treatment type, or tumor and lymph node (T/N) categories in multivariable analyses. The MuNI was also prognostic for DFS, OS, and DMFS in patients with stage I and stage III OPSCC, separately.CONCLUSIONMuNI holds promise as a low-cost, tissue-nondestructive, H&E stain–based digital biomarker test for counseling, treatment, and surveillance of patients with p16+ OPSCC. These data support further confirmation of the MuNI in prospective trials.FUNDINGNational Cancer Institute (NCI), NIH; National Institute for Biomedical Imaging and Bioengineering, NIH; National Center for Research Resources, NIH; VA Merit Review Award from the US Department of VA Biomedical Laboratory Research and Development Service; US Department of Defense (DOD) Breast Cancer Research Program Breakthrough Level 1 Award; DOD Prostate Cancer Idea Development Award; DOD Lung Cancer Investigator-Initiated Translational Research Award; DOD Peer-Reviewed Cancer Research Program; Ohio Third Frontier Technology Validation Fund; Wallace H. Coulter Foundation Program in the Department of Biomedical Engineering; Clinical and Translational Science Award (CTSA) program, Case Western Reserve University; NCI Cancer Center Support Grant, NIH; Career Development Award from the US Department of VA Clinical Sciences Research and Development Program; Dan L. Duncan Comprehensive Cancer Center Support Grant, NIH; and Computational Genomic Epidemiology of Cancer Program, Case Comprehensive Cancer Center. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH, the US Department of VA, the DOD, or the US Government.  相似文献   
40.
Rat stromal bone-marrow cells cultured in the presence of dexamethasone, ascorbic acid, &#103 -glycerophosphate, and fibroblast growth factor-2 (FGF-2) express the osteogenic phenotype (Pitaru et al., J. Bone Miner. Res . 8:919-929, 1993). The purpose of this study was to establish a long-term homogeneous culture expressing the osteogenic phenotype. The cultures were routinely passaged every 5 days in the absence or presence of either or both dexamethasone and FGF-2, and the cumulative doubling number and the expression of the osteogenic phenotype were determined. Cultures treated with dexamethasone (10 &#109 7 M) ceased proliferation and only upon addition of FGF-2 (3 ng/ml) was a spontaneous immortalization achieved, as expressed by sustained proliferation for about 1 year, with a doubling time of 22 h and more than 300 doublings in 72 passages. Both FGF-2 and dexamethasone are required and act synergistically to maintain cell propagation, alkaline phosphatase expression, and osteocalcin secretion; however, protein content was FGF-2 dependent and the mineralization was dexamethasone dependent. Repetitive single-cell cloning tested the homogeneity and stability of the cells expressing the osteogenic phenotype in these long-term cultures. It was shown that 25% to 50% of subclones derived from clones with an osteogenic phenotype do not further express the osteogenic phenotype. In conclusion, we have established a spontaneously immortalized dexamethasone- and FGF-2-dependent rat stromal bone-marrow-derived long-term culture expressing the osteogenic phenotype. The cultures tend to lose the osteogenic phenotype, and dexamethasone supports the long-term preservation of the osteogenic phenotype.  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