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   1103篇
  免费   90篇
  国内免费   19篇
儿科学   78篇
妇产科学   4篇
基础医学   138篇
口腔科学   63篇
临床医学   138篇
内科学   188篇
皮肤病学   46篇
神经病学   27篇
特种医学   244篇
外科学   97篇
综合类   29篇
预防医学   49篇
眼科学   13篇
药学   35篇
  1篇
肿瘤学   62篇
  2023年   3篇
  2022年   5篇
  2021年   8篇
  2020年   13篇
  2019年   12篇
  2018年   14篇
  2017年   9篇
  2016年   13篇
  2015年   27篇
  2014年   25篇
  2013年   45篇
  2012年   25篇
  2011年   23篇
  2010年   56篇
  2009年   53篇
  2008年   26篇
  2007年   36篇
  2006年   26篇
  2005年   28篇
  2004年   17篇
  2003年   28篇
  2002年   20篇
  2001年   20篇
  2000年   8篇
  1999年   27篇
  1998年   84篇
  1997年   76篇
  1996年   59篇
  1995年   52篇
  1994年   37篇
  1993年   45篇
  1992年   7篇
  1991年   23篇
  1990年   14篇
  1989年   42篇
  1988年   35篇
  1987年   25篇
  1986年   18篇
  1985年   18篇
  1984年   9篇
  1983年   12篇
  1982年   14篇
  1981年   14篇
  1980年   15篇
  1979年   3篇
  1978年   13篇
  1977年   11篇
  1976年   10篇
  1975年   8篇
  1954年   1篇
排序方式: 共有1212条查询结果,搜索用时 15 毫秒
61.
62.
63.
We have used the long-term bone marrow culture (LTBMC) system to analyze hematopoiesis in three patients with dyskeratosis congenita (DC), two of whom had aplastic anemia, and the third had a normal blood count (apart from mild macrocytosis) and normal BM cellularity. Hematopoiesis was severely defective in all three patients, as measured by a low incidence of colony-forming cells and a low level of hematopoiesis in LTBMC. The function of the marrow stroma was normal in its ability to support the growth of hematopoietic progenitors from normal marrows seeded onto them in all three cases, but the generation of hematopoietic progenitors from patients marrow cells inoculated onto normal stromas was reduced, thus suggesting the defect to be of stem cell origin. The parents and unaffected brother of one of the families have also been studied in LTBMC and all showed normal hematopoietic and stromal cell function. From this study we speculate that there are some similarities between DC and the defect in the W/Wv mouse.  相似文献   
64.
3-Hydroxypropyl flufenamide (Flu-HPA) is one of a series of flufenamic acid derivatives that enhances blood clot lysis in vitro. Studies of possible mechanisms of action of Flu-HPA were undertaken. The profibrinolytic activity of Flu-HPA in clot lysis assays was found to be dependent on plasminogen. The influence of Flu-HPA on the ability of purified alpha 2-antiplasmin to inhibit purified plasmin was studied. Plasmin activity was determined using 125I-fibrin plates or the spectrophotometric tripeptide substrate, Val-Leu-Lys-paranitroanilide. At Flu-HPA concentrations greater than 1 mM, the inhibitory activity of alpha 2-antiplasmin was abolished in a time-dependent and concentration- dependent manner. The influence of Flu-HPA on the ability of purified Cl inhibitor to inhibit purified plasma kallikrein and beta-Factor XIIa was also studied. Cl inhibitor activity was abolished by Flu-HPA at concentrations greater than 2 mM. Notably, Flu-HPA up to 60 mM did not affect the amidolytic activities of plasmin, kallikrein, or beta-Factor XIIa. Flu-HPA did not release enzyme activity from preformed complexes of either alpha 2-antiplasmin and plasmin of Cl inhibitor and kallikrein. A water-soluble derivative of flufenamic acid, N-flufenamyl- glutamic acid, also inactivated alpha 2-antiplasm and Cl inhibitor. This inactivation was shown to be reversible. These results indicate that synthetic fibrinolytic compounds such as flufenamic acid derivatives may promote fibrinolysis by directly inactivating alpha 2- antiplasmin and Cl inhibitor.  相似文献   
65.
Tacrolimus exposure and renal function data to 36 months post‐transplant were analyzed from the prospective, observational Mycophenolic acid Observational REnal transplant (MORE) registry in which de novo kidney transplant patients were managed according to local practice. Tacrolimus trough (C0) concentration at month 12 was stratified as low (<6 ng/mL), moderate (6–8 ng/mL), or high (>8 ng/mL) in 724 patients. Estimated glomerular filtration rate (eGFR) was stratified as low (<60 mL/min/1.73 m2) or high (≥60 mL/min/1.73 m2). High tacrolimus C0 (>8 ng/mL) was observed in 47.7%, 34.1%, 26.8%, and 26.7% of patients at baseline and months 12, 24, and 36, respectively. Biopsy‐proven acute rejection was similar to month 36 regardless of tacrolimus C0 category at month 12. Tacrolimus C0 >8 ng/mL vs. <6 ng/mL at month 12 was predictive of low eGFR at month 24 (p = 0.023) with a nonsignificant trend at month 36 (p = 0.085). Infections (p < 0.013) and BK virus infection (p < 0.001) were most frequent in the low tacrolimus C0 cohort. Neutropenia was most frequent in the high tacrolimus C0 category (p = 0.010). In conclusion, over a quarter of patients were exposed to high tacrolimus C0 to 36 months post‐transplant. Tacrolimus exposure did not affect rejection risk, but tacrolimus C0 >8 ng/mL at month 12 was predictive of subsequent low eGFR compared to C0 <6 ng/mL.  相似文献   
66.
67.
Dihydronaphthofurans (DHNs) are an important class of arene ring-fused furans which are widely found in many natural and non-natural products and drug candidates with relevant biological and pharmacological activities. Furthermore, vinylidene-naphthofurans exhibit photochromic properties when exposed to UV or sun light at room temperature. For these reasons, a vast array of synthetic procedures for the preparation of dihydronaphthofurans including annulation of naphthols with various reagents, cycloaddition reactions ([3 + 2], [4 + 1] and Diels–Alder), intramolecular transannulation, Friedel–Crafts, Wittig, Claisen rearrangement, neophyl rearrangement and other reactions under various conditions have been developed over the past decades. This review aims to describe the different strategies developed so far for the synthesis of dihydronaphthofurans and their applications. After a brief introduction to the types of dihydronaphthofurans and their biological activities, the different synthetic approaches such as chemical, photochemical, and electrochemical, methods are described and organized on the basis of the catalysts and the other reagents employed in the syntheses. The subsequent section focuses on biological and pharmacological applications and photochromic properties of the target compounds.

Dihydronaphthofurans (DHNs) are an important class of arene ring-fused furans which are widely found in many natural and non-natural products and drug candidates with relevant biological and pharmacological activities.  相似文献   
68.
The detection and quantitation of apoptotic cells is becoming increasingly important in the investigation of the role of apoptosis in cellular proliferation and differentiation. The pathogenesis of hematologic disorders such as aplastic anemia and the development of neoplasia are believed to involve dysregulation of apoptosis. To quantitate accurately the proportion of apoptosis cells within different cell types of a heterogeneous cell population such as blood or bone marrow, a method is required that combines the analysis of large numbers of cells with concurrent immunophenotyping of cell surface antigens. In this study, we have evaluated such a method using the fluorescent DNA binding agent, 7-amino actinomycin D (7AAD), to stain three diverse human cell lines, induced to undergo apoptosis by three different stimuli. Flow cytometric analysis defines three populations on the basis of 7AAD fluorescence and forward light scatter. We have shown by cell sorting and subsequent morphological assessment and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling that the populations defined by 7AAD represent live, apoptotic, and late-apoptotic/dead cells. This method is quick, simple, reproducible, and cheap and will be a valuable tool in the investigation of the role of apoptosis in normal physiology and in disease states.  相似文献   
69.
目的 探讨整合素在体外培养的椎间盘细胞力学传导中的作用。方法采用猪的椎间盘进行体外细胞的分离和培养,对细胞施加周期性液压负荷,通过对细胞的形态学观察、Western免疫印迹、免疫细胞化学染色和免疫荧光,分别检测整合素α3和肌动蛋白在周期性压力下椎间盘细胞中的表达。结果经加压后,纤维环细胞和髓核细胞均可见体积缩小,由多角形转变为细长形,α3和肌动蛋白在AF和NP细胞中的表达均明显减少。结论压力抑制了整合素α3的产生,整合素α3将力的信号转换到细胞内时,进一步影响到与其关系密切的肌动蛋白。  相似文献   
70.
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