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   45199篇
  免费   2128篇
  国内免费   371篇
耳鼻咽喉   468篇
儿科学   833篇
妇产科学   1303篇
基础医学   5355篇
口腔科学   1711篇
临床医学   3471篇
内科学   12640篇
皮肤病学   961篇
神经病学   3948篇
特种医学   1190篇
外科学   6840篇
综合类   172篇
一般理论   9篇
预防医学   2469篇
眼科学   719篇
药学   2441篇
中国医学   115篇
肿瘤学   3053篇
  2024年   40篇
  2023年   323篇
  2022年   777篇
  2021年   1469篇
  2020年   795篇
  2019年   1128篇
  2018年   1555篇
  2017年   1021篇
  2016年   1117篇
  2015年   1312篇
  2014年   1796篇
  2013年   2362篇
  2012年   3625篇
  2011年   3586篇
  2010年   2016篇
  2009年   1752篇
  2008年   3048篇
  2007年   3158篇
  2006年   2946篇
  2005年   2930篇
  2004年   2629篇
  2003年   2364篇
  2002年   2088篇
  2001年   279篇
  2000年   191篇
  1999年   296篇
  1998年   367篇
  1997年   323篇
  1996年   283篇
  1995年   279篇
  1994年   220篇
  1993年   164篇
  1992年   143篇
  1991年   101篇
  1990年   104篇
  1989年   85篇
  1988年   66篇
  1987年   57篇
  1986年   73篇
  1985年   70篇
  1984年   73篇
  1983年   67篇
  1982年   94篇
  1981年   66篇
  1980年   71篇
  1979年   39篇
  1978年   47篇
  1977年   37篇
  1976年   35篇
  1975年   31篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
12.
Abstract: The use of neuromuscular electrical stimulation (NMES) for rehabilitation of gait in spinal patients is widely known. The best results can be obtained with the use of biomechanical sensors and a closed loop NMES system. One of the biggest problems faced in the design of control systems for closed-loop operation, in gait rehabilitation, is the variation of the mechanical conditions during the phases of gait. This work presents a new approach to ease the design of rule-based closed loop systems for operation in conditions such as gait rehabilitation.  相似文献   
13.
The photophysics of protoporphyrin-naphthyl (P-N) pairs covalently and randomly bound to the ε-amino groups of the side-chains of poly(L -lysine) (PL) were investigated by steady-state and time-resolved fluorescence measurements. The results indicate that quenching of excited naphthalene (λex = 280 nm) chiefly occurs by interconversion to the triplet state when the polymeric matrix is in random coil (pH ≈ 7) and by intramolecular electron transfer from ground-state porphyrin, P → 1N*, when the polypeptide is in α-helical conformation (pH ≈ 11), the specific rate constant of the electron transfer being 3,1 · 107 s?1 (25°C). PNPL exhibits very little exciplex fluorescence, whatever the pH, suggesting both a reduced internal Brownian motion of the chromophores, owing to the amide bond in the substituted side-chains, and a relatively large average interprobe separation distance. This agrees with polarized fluorescence data and with the results of a conformational statistics analysis on the fully ordered PNPL, indicating that the average interchromophoric distance for which the electron transfer has the highest probability to occur is around 12 Å. The computational results allowed us to reproduce the experimental fluorescence decay curves and estimate the parameters governing the electron transfer process. Implications of these findings on the relaxation time of the heli-xcoil transition in PNPL are briefly discussed.  相似文献   
14.
Background: Head-kidney, considered the major fish lympho-haemopoietic tissue, consists of cells of the different haemopoietic series supported by a network of stromal cells whose morphofunctional properties have not been established. We report the ultrastructure and cytochemical features of the reticulo-endothelial stroma of the head-kidney from the seawater teleost gilthead seabream (Sparus aurata L.). Methods: Samples of head-kidney were processed for electron microscopic study. Some of the samples were incubated for acid and alkaline phosphatase, peroxidase, glucose-6-phosphatase, or ATPase. Results: The reticulo-endothelial stroma of gilthead seabream head-kidney consists of sinusoidal cells (endothelial and adventitial cells) and reticular cells (macrophage-type reticulum and fibroblast-like reticular cells). Transcytosis vesicles and rounded medium electron-dense granules were observed in the cytoplasm of the endothelial cells. The adventitial cells partially covered the outside surface of the endothelial cells and were joined by desmosomes. The macrophage-type reticulum cells were characterized by their cytoplasmic processes and acid phosphatase positive lysosomes. The fibroblast-like reticular cells were joined by desmosomes and formed an extensive network between the haemopoietic parenchyma. They were peroxidase negative and acid and alkaline phosphatase, glucose-6-phosphatase, β-glucuronidase, and ATPase positive. Conclusions: The ultrastructural and cytochemical features of the reticulo-endothelial stroma of the gilthead seabream head-kidney are similar to those of mammalian bone marrow, suggesting phylogenetic analogies between both tissues. © 1995 Wiley-Liss, Inc.  相似文献   
15.
16.
17.
Hyperexcitability of the motor system has been reported in Parkinson's disease (PD). We evaluate how cutaneous afferents modulate motor excitability in PD patients and whether abnormal modulation is correlated to parkinsonian symptoms. Digital stimulation causes abnormal enhancement of motor responses in patients. This effect may be one of the features of motor hyperexcitability in PD. Cutaneomotor hyperexcitability correlates with clinical scores, suggesting that abnormal processing of cutaneous inputs might contribute to the pathogenesis of parkinsonian symptoms.  相似文献   
18.
The isoleucyl-tRNA synthetase (ileS) gene was sequenced in toto from 9 and in part from 31 Staphylococcus aureus strains with various degrees of susceptibility to mupirocin. All strains for which the mupirocin MIC was greater than 8 microg/ml contained point mutations affecting the Rossman fold via Val-to-Phe changes at either residue 588 (V588F) or residue 631 (V631F). The importance of the V588F mutation was confirmed by an allele-specific PCR survey of 32 additional strains. Additional mutations of uncertain significance were found in residues clustered on the surface of the IleS protein.  相似文献   
19.
20.
We report a case of cervical dystonia occurring in a 33-year-old without personal history of movement disorder but with family history of essential tremor, primigravid, primiparous woman at 1 weeks' amenorrhea, resolved completely after delivery in the course of 3 months. Dystonia never recurred in the following 5 years. Several neurological disorders are known to occur or worsen during pregnancy. As far as we know, this is the second reported case of dystonia occurring during pregnancy, thus confirming that dystonia gravidarum represents a new entity and should be considered in women of reproductive age affected by dystonia, especially when presenting with rapid-onset cervical dystonia.  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