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   203838篇
  免费   18170篇
  国内免费   11528篇
耳鼻咽喉   1764篇
儿科学   2865篇
妇产科学   4025篇
基础医学   22493篇
口腔科学   4158篇
临床医学   25566篇
内科学   31708篇
皮肤病学   2377篇
神经病学   10442篇
特种医学   6865篇
外国民族医学   69篇
外科学   20545篇
综合类   31638篇
现状与发展   33篇
一般理论   30篇
预防医学   14612篇
眼科学   5414篇
药学   21501篇
  192篇
中国医学   10672篇
肿瘤学   16567篇
  2024年   657篇
  2023年   2891篇
  2022年   6935篇
  2021年   9205篇
  2020年   6880篇
  2019年   6066篇
  2018年   6493篇
  2017年   6014篇
  2016年   5478篇
  2015年   8539篇
  2014年   10724篇
  2013年   10724篇
  2012年   15808篇
  2011年   16885篇
  2010年   11376篇
  2009年   9204篇
  2008年   11908篇
  2007年   11713篇
  2006年   10941篇
  2005年   10264篇
  2004年   7449篇
  2003年   6749篇
  2002年   5761篇
  2001年   4818篇
  2000年   4656篇
  1999年   4542篇
  1998年   2522篇
  1997年   2415篇
  1996年   1936篇
  1995年   1867篇
  1994年   1625篇
  1993年   970篇
  1992年   1420篇
  1991年   1295篇
  1990年   1091篇
  1989年   934篇
  1988年   821篇
  1987年   748篇
  1986年   582篇
  1985年   464篇
  1984年   304篇
  1983年   249篇
  1982年   155篇
  1981年   139篇
  1980年   100篇
  1979年   183篇
  1978年   129篇
  1977年   97篇
  1974年   111篇
  1972年   102篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.

Background  

Colorectal cancer, if detected early, has greater than 90% 5-year survival. However, survival has been shown to vary across racial/ethnic groups in the United States, despite the availability of early detection methods.  相似文献   
92.
A patient with skeletal Class III malocclusion was treated in 2 phases during the early permanent dentition. In phase 1, maxillary protraction was combined with rapid palatal expansion; in phase 2, fixed appliances were placed. The results were good posttreatment, and, 1 year later, a favorable growth tendency could be observed. This report shows that treatment for a patient with skeletal Class III malocclusion can be started in the early permanent dentition, with very good final results.  相似文献   
93.
PURPOSE: Perineural invasion is a frequent occurrence in salivary adenoid cystic carcinoma (ACC) and may prevent complete surgical resection. Studies have indicated that nerve growth factor (NGF) and its high-affinity receptor tyrosine kinase A (TrkA) may play a role in perineural invasion in several malignancies in which perineural invasion is observed. The present study was conducted to investigate the expression of NGF and TrkA in salivary ACC and to examine the effects of NGF on adhesion, migration and invasion capacities of a salivary ACC cell line (SACC-83) in vitro. PATIENTS AND METHODS: Expression of NGF and TrkA was explored using immunohistochemistry in paraffin-embedded tissues of 32 cases of salivary ACC. The effects of NGF on in vitro adhesion, migration, and invasion capacities of the SACC-83 cell line were examined using an MTT assay and a modified Boyden chamber assay respectively. RESULTS: In ACC specimens, 31 (96.9%) and 32 (100%) tumors showed immunoreactivity for NGF and TrkA respectively. Significant correlations were found between NGF/TrkA expression levels and perineural invasion (P < .05). In cell adhesion assay, the percent adherences of SACC-83 cells co-cultured with 25 ng/ml NGF at 1.5 hours and 5, 25 ng/ml NGF at 6 hours were significantly higher than that co-cultured with 0 ng/ml NGF (P < .05). However, high concentration of NGF (500 ng/ml) resulted in a significant inhibition of invasion (P < .05). CONCLUSION: Overexpression of NGF and TrkA in human salivary ACC tissues may constitute a reason for perineural invasion in salivary ACC.  相似文献   
94.
什么是针灸现代化?1997年11月在北京举办的世界针联成立10周年学术大会上,王雪苔教授以《针灸的现状与未来》为题作特别演讲时认为,20世纪针灸发展的时代特征是针灸国际化和现代化。针灸现代化的主要标志是既保持中医学理论体系,又赋予现代科学内涵的现代针灸学的形成。笔者认为:在针灸现代化过程中,  相似文献   
95.
Although many monoclonal antibodies have been made in human colon cancer, none of them are from the Chinese species. Recently, a colon cancer cell line CC-M2 established from a Chinese patient has been completely characterized and used as immunogen to produce monoclonal antibodies. Monoclonal antibodies were produced by standard hybridoma technique. The fusion rate was 95.8%. An isotype IgG1 of high proliferation named as Sam-2 was used in this study. The titers were measured around 10(4). Further studies on MoAb Sam-2 through indirect immunofluorescent and immunoperoxidase tests revealed its good specificity and sensitivity in colorectal cancer tissue. In CEA study, the result indicated that Sam-2 may react on a non-CEA related antigen. For further clinical application, the antigen was identified as a glycoprotein by chemical resistant test. In preliminary studies using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting techniques, Sam-2 could recognize two closed antigens or a dimer antigen with molecular weight 25.2 and 27 Kd respectively.  相似文献   
96.
本文采用高效液相色谱法,以盐酸布比卡因为内标,检测波长220nm,在Symmetry-C18柱上,以己腈-磷酸二氢钾(pH2.5)(3862,V/V)为流动相,测定盐酸美沙酮及其口服液的含量。方法平均回收率为100.17%,日内及日间的RSD均<1%。方法简便、快速、准确。  相似文献   
97.
Peritoneal macrophages (PM) perform first-line defense activity against peritonitis, the most important complication in continuous ambulatory peritoneal dialysis (CAPD) therapy. Our longitudinal study has compared the PM function in 20 uremic patients during periods free of peritonitis since they started CAPD therapy in January 1987. The results showed that at the initiation of CAPD, there was a higher bactericidal activity, phagocytosis index, H2O2 production and interleukin-1 (IL-1), gamma-interferon (IFN-gamma) and tumor necrosis factor (TNF) production ability and MHC expression. As time went on, these progressively decreased, and by 9 months after CAPD therapy had started they were significantly lower than at the beginning. During the 1.5-year follow-up period, there was a significantly increased peritonitis rate in the period 6 months after the beginning of CAPD than in the period before the 6th month (88.3 vs. 11.7% respectively; p less than 0.001). These results indicate that PM of new CAPD patients have a more active function than those of established patients. The established patients had a greater risk of peritonitis. A comparison of the immunological profiles of PM from patients who had a peritonitis history shows that phagocytosis index, bactericidal activity and IL-1 and TNF production of PM were significantly decreased during the period free of peritonitis. This result suggests that these parameters may serve as an indicator in developing peritonitis.  相似文献   
98.
R.R Fiscus  L Lu  A.W.K Tu  H Hao  L Yang  X Wang 《Neuropeptides》1998,32(6):499-509
Calcitonin gene-related peptide (CGRP) causes vasorelaxation in rat aorta involving endothelium/nitric oxide (NO)-dependent elevations of both cAMP and cGMP levels. When endothelium is removed, preincubation with exogenous NO uncovers and potentiates direct (endothelium-independent) cAMP elevations and vasorelaxations caused by CGRP. This enhancing effect of NO potentially involves elevation of cGMP and inhibition of Type III (cGMPinhibitable) phosphodiesterase, causing accumulation of cAMP. However, NO may have other actions. The aim of the present study was to determine if brain natriuretic peptide (BNP), which elevates cGMP levels independent of NO, could enhance cAMP accumulations and vasorelaxations induced by CGRP in rat aortic rings denuded of endothelium. When added separately, neither CGRP (100 nM) nor BNP (10 nM) altered cAMP levels. When added in combination, CGRP (100 nM) and BNP (10 nM) significantly elevated cAMP levels (from control of 0.95 ± 0.08 to 1.53 ± 0.09 pmol/mg protein) at 2 min. BNP (10 nM) elevated cGMP levels 10-fold at 2 min and this response was not altered by co-administration of CGRP (100 nM).Pretreatment with BNP at concentrations as low as 1 nM in endothelium-denuded aortic rings greatly enhanced the direct vasorelaxant effects of CGRP (100 nM) (from control of 0% to 57.6 ± 6.8% relaxation of phenylephrineprecontractions). Our findings indicate that BNP enhances direct (endothelium-independent) cAMP elevations and vasorelaxations caused by CGRP in rat aorta, thus supporting the concept that cGMP inhibits cAMP metabolism and enhances CGRP-induced responses in aortic smooth muscle cells.  相似文献   
99.
采用SD大鼠一侧大脑中动脉阻断致局限性脑缺血模型。脑缺血后迅速断头置于液氮中,HPLC外标定量法测定各磷脂组分。观察脑缺血1、5、15、60、360min时脑细胞膜磷脂含量变化。结果显示,PI在缺血早期显著低于对照组(P<0.01~0.05);PE、PC早期仅呈下降趋势,PE在缺血60min组、PC缺血360min组显著低于对照组(P<0.01~0.05)。PS在缺血全过程中变化轻微(P>0.05)。提示磷脂降解与脑缺血存在一定关系,缺血早期首先出现脑细胞膜功能磷脂降解,膜结构磷脂则在缺血后期出现显著变化,且PE较PC优先降解。  相似文献   
100.
对小鼠睾丸冰冻切片LDH-X的显示方法作了进一步探讨。实验表明,以L-2-羟基-3-甲基戊酸(HMV)为特异性底物,能相当有效地显示睾丸LDH-X的分布,且该底物的配制方法简便易行。在显示LDH-X的孵育液中采用萘酚蓝(NB)作中间递电子体较吩嗪甲基硫酸酯更具优越性。  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