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   4503篇
  免费   233篇
  国内免费   49篇
耳鼻咽喉   68篇
儿科学   71篇
妇产科学   93篇
基础医学   618篇
口腔科学   110篇
临床医学   414篇
内科学   763篇
皮肤病学   150篇
神经病学   322篇
特种医学   203篇
外科学   577篇
综合类   32篇
一般理论   3篇
预防医学   243篇
眼科学   67篇
药学   576篇
中国医学   110篇
肿瘤学   365篇
  2023年   31篇
  2022年   113篇
  2021年   183篇
  2020年   90篇
  2019年   116篇
  2018年   143篇
  2017年   105篇
  2016年   140篇
  2015年   195篇
  2014年   255篇
  2013年   277篇
  2012年   388篇
  2011年   404篇
  2010年   222篇
  2009年   167篇
  2008年   269篇
  2007年   256篇
  2006年   225篇
  2005年   190篇
  2004年   165篇
  2003年   140篇
  2002年   107篇
  2001年   97篇
  2000年   78篇
  1999年   82篇
  1998年   33篇
  1997年   18篇
  1996年   22篇
  1995年   11篇
  1994年   9篇
  1993年   8篇
  1992年   31篇
  1991年   29篇
  1990年   25篇
  1989年   22篇
  1988年   10篇
  1987年   12篇
  1986年   5篇
  1985年   17篇
  1984年   5篇
  1983年   6篇
  1979年   5篇
  1974年   8篇
  1972年   5篇
  1971年   8篇
  1970年   4篇
  1969年   6篇
  1968年   14篇
  1967年   5篇
  1966年   4篇
排序方式: 共有4785条查询结果,搜索用时 31 毫秒
991.
992.
O P Khanna  D L Son 《Urology》1986,27(5):424-428
The Bac-T-Screen was used to process 795 urine specimens. Tests for urine specimens took slightly more than two minutes. The Bac-T-Screen predicted with 99 per cent accuracy if a specimen was negative for bacteriuria or pyuria. Thus, approximately one half of all carefully collected urine specimens need no further laboratory culture. In addition, the Bac-T-Screen detected bacteriuria with a sensitivity of 96 per cent at the 10(5) CFU/ml level of probability. Pyuria (1 +) was detected with a sensitivity of 98 per cent. The Bac-T-Screen can be used in an office practice as well as in the clinical laboratory.  相似文献   
993.
Chronic renal transplant dysfunction (CRTD) remains a leading cause of renal allograft loss. Evidence suggests that immunological and ischemic insults are mainly associated with CRTD occurring within the first year after transplantation, whereas nonimmunological insults are predominantly associated with CRTD beyond the first year. Several cardiovascular risk factors, such as obesity, dyslipidemia, hypertension, and diabetes mellitus have been identified as important nonimmunological risk factors for CRTD. These risk factors constitute the metabolic syndrome (MS). As renal allograft function is a surrogate marker of renal allograft loss, we investigated the association of MS with impairment of renal allograft function beyond the first year after transplantation in a cross-sectional study of 606 renal transplant outpatients. Metabolic syndrome was defined using the definition of the National Cholesterol Education Program. Renal allograft function was assessed as the 24-h urinary creatinine clearance. A total of 383 out of 606 patients (63%) suffered from MS at a median time of 6 years (2.6-11.4) post-transplant. Presence of MS was associated with impaired renal allograft function beyond 1 year post-transplant [-4.1 mL/min, 95%CI (-7.1, -1.1)]. The impact of MS did not change appreciably after adjustment for established risk factors for CRTD [-3.1 mL/min, 95%CI (-6.0, -0.2)]. However, not all component criteria of MS contributed equally. Only systolic blood pressure and hypertriglyceridemia were independently associated with impaired renal allograft function beyond 1 year post-transplant in multivariate analyses.  相似文献   
994.
In 20 patients with a cadaveric renal allograft, serial measurements were made of the serum complement factors C3, C4, factor B (FB), and C3d, the stable conversion product of C3. Measurements were started immediately before transplantation and continued thereafter once a week to investigate whether these assays help to differentiate between acute allograft rejection (R) and an active cytomegalovirus (CMV) infection. Fifteen patients had one or more R episodes, and 9 patients suffered from an active CMV infection. Six patients had an R episode and subsequently a CMV infection 13-64 days after R. No significant changes were found in the levels of C3, C4, and FB during R or CMV infection. C3d levels remained unchanged or decreased slightly during R. However, there was a 43-500% increase in the C3d level during CMV infection. This difference in the behavior of levels of C3d during R and CMV infection is significant (P less than 0.01), and suggests that serial measurements of C3d may be useful in differentiating CMV infection from R after renal transplantation.  相似文献   
995.
The flowers ofChrysanthemum boreale afforded handelin, a unique guaianolide dimer and a mixture ofn-hydrocarbons andn-hydrocarbon alcohols in addition to β-sitosterol and β-sitosterol glucoside. Detailed analysis of the1H-and11C-NMR spectra of handelin was carried out by the application of two-dimensional1H-1H-COSY and1H-11C multiple-bond, multiplequantum sepctroscopic correlation techniques. Handelin was inactive in thein vitro anti-tumor activity.  相似文献   
996.
997.
The detailed mechanisms underlying long-term potentiation (LTP) are not known. In hippocampal CA1, translocation of protein kinase C (PKC) activity from cytosol to membrane and subsequent phosphorylation of growth associated protein (GAP)-43 have been demonstrated to be critical events for the maintenance phase of LTP. LTP in mossy fiber (MF)-CA3 pathway and the Schaffer collateral/commissural (SC)-CA1 pathway differ in a number of ways: SC-CA1 LTP depends on NMDA receptors while MF-CA3 LTP does not, and SC-CA1 LTP is primarily postsynaptic while MF-CA3 LTP is primarily presynaptic. The role of PKC in MF-CA3 LTP has not been studied. We investigated the role of PKC in CA3 and show that PKC inhibitors prevent LTP, but that PKC activators produce a reversible synaptic potentiation, indicating that PKC activation is an essential but not sufficient component of LTP in CA3. Then using antibodies against specific PKC isozymes we have determined the membrane vs. cytosolic distribution of various PKC isozymes in slices subjected to low or tetanic stimulation, or perfused with phorbol esters (PDAc). Compared with control, LTP and PDAc slices show greater PKC-α and -ε immunoreactivity in the membrane fraction, indicating that both LTP and phorbol ester treatment induce translocation of PKC-α and -ε from cytosol to membrane. However, with PKC-β and PKC-γ the only detectable translocation from cytosol to membrane was in the phorbol ester-treated slices. Thus, while phorbol ester treatment causes translocation of PKC-α, -β, -γ and -ε, the only detectable translocation associated with CA3 LTP is that of PKC-α and -ε.  相似文献   
998.
The European Journal of Health Economics - Cardiovascular diseases (CVDs) remain a global health challenge due to number of deaths and use of healthcare services related to the condition....  相似文献   
999.

Purpose

The purpose of the study was to evaluate protein expression of PD-L1 and CD20 as prognostic biomarkers of patient outcome in inflammatory breast cancer (IBC) samples.

Methods

PD-L1 and CD20 protein expression was measured by immunohistochemistry in 221 pretreatment IBC biopsies. PD-L1 was assessed in tumor cells (PD-L1+ tumor cells) and tumor stromal infiltrating lymphocytes (PD-L1+ TILs); CD20 was scored in tumor-infiltrating B cells. Kaplan–Meier curves and Cox proportional hazard models were used for survival analysis.

Results

PD-L1+ tumor cells, PD-L1+ TILs, and CD20+ TILs were found in 8%, 66%, and 62% of IBC, respectively. PD-L1+ tumor cells strongly correlated with high TILs, pathological complete response (pCR), CD20+ TILs, but marginally with breast cancer-specific survival (BCSS, P?=?0.057). PD-L1+ TILs strongly correlated with high TILs, CD20+ TILs, and longer disease-free survival (DFS) in all IBC and in triple-negative (TN) IBC (P?<?0.035). IBC and TN IBC patients with tumors containing both CD20+ TILs and PD-L1+ TILs (CD20+TILs/PD-L1+TILs) showed longer DFS and improved BCSS (P?<?0.002) than patients lacking both, or those with either CD20+ TILs or PD-L1+ TILs alone. In multivariate analyses, CD20+TILs/PD-L1+TILs status was an independent prognostic factor for DFS in IBC (hazard ratio (HR): 0.53, 95% CI 0.37–0.77) and TN IBC (HR: 0.39 95% CI 0.17–0.88), and for BCSS in IBC (HR: 0.60 95% CI 0.43–0.85) and TN IBC (HR: 0.38 95% CI 0.17–0.83).

Conclusion

CD20+TILs/PD-L1+TILs status represents an independent favorable prognostic factor in IBC and TN IBC, suggesting a critical role for B cells in antitumor immune responses. Anti-PD-1/PD-L1 and B cell-activating immunotherapies should be explored in these settings.
  相似文献   
1000.

Background

Neoadjuvant systemic therapy (NST) is performed to increase the rate of breast-conserving surgery in advanced breast cancer patients. Although magnetic resonance imaging (MRI) is accurate in predicting residual cancer, if calcification remains, the issue of whether to perform the surgery on the basis of the residual tumor prediction range in mammography (MMG) or MRI has not yet been elucidated. This study aimed to estimate the accuracy of predicting residual tumor after NST for residual microcalcification on mammographic and enhancing lesion on MRI.

Patients and Methods

This was a single-center, retrospective study. We included breast cancer patients who underwent NST, had microcalcifications in the post-NST MMG, and underwent surgery from January 2, 2013 to December 30, 2014 at Asan Medical Center. Patients with post-NST MMG as well as MRI were included. Final pathologic tumor size with histopathology and biomarker status were obtained postoperatively.

Results

In total, 151 patients were included in this study. Overall, MRI correlated better than MMG in predicting the tumor size (intraclass correlation coefficient [ICC], 0.769 vs. 0.651). For hormone receptor (HR)-positive (HR+)/HER2? subtype, MMG had higher correlation than MRI (ICC = 0.747 vs. 0.575). In HR? subtype, MRI had a strong correlation with pathology (HR?/HER2+ or triple negative (TN), ICC = 0.939 vs. 0.750), whereas MMG tended to overestimate the tumor size (HR?/HER2+ or TN, ICC = 0.543 vs. 0.479).

Conclusion

Post-NST residual microcalcifications on MMG have a lower correlation with residual tumor size than MRI. Other than HR+/HER2? subtype, the extent of calcifications on preoperative evaluation might not be accurate in evaluating the residual extent of the tumor after NST.  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