首页 | 官方网站   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   183489篇
  免费   1562篇
  国内免费   47篇
医药卫生   185098篇
  2023年   70篇
  2022年   73篇
  2021年   370篇
  2020年   234篇
  2019年   322篇
  2018年   22199篇
  2017年   17556篇
  2016年   19725篇
  2015年   1206篇
  2014年   1196篇
  2013年   1254篇
  2012年   7681篇
  2011年   21747篇
  2010年   19199篇
  2009年   11845篇
  2008年   20095篇
  2007年   22271篇
  2006年   1074篇
  2005年   2652篇
  2004年   3762篇
  2003年   4692篇
  2002年   2838篇
  2001年   315篇
  2000年   436篇
  1999年   211篇
  1998年   249篇
  1997年   230篇
  1996年   111篇
  1995年   128篇
  1994年   111篇
  1993年   82篇
  1992年   49篇
  1991年   95篇
  1990年   131篇
  1989年   83篇
  1988年   62篇
  1987年   51篇
  1986年   30篇
  1985年   35篇
  1984年   25篇
  1983年   28篇
  1982年   33篇
  1980年   44篇
  1970年   23篇
  1938年   61篇
  1937年   25篇
  1935年   22篇
  1934年   30篇
  1932年   56篇
  1930年   46篇
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
1.

Microdeletions encompassing 14q11.2 locus, involving SUPT16H and CHD8, were shown to cause developmental delay, intellectual disability, autism spectrum disorders and macrocephaly. Variations leading to CHD8 haploinsufficiency or loss of function were also shown to lead to a similar phenotype. Recently, a 14q11.2 microduplication syndrome, encompassing CHD8 and SUPT16H, has been described, highlighting the importance of a tight control of at least CHD8 gene-dosage for a normal development. There have been only a few reports of 14q11.2 microduplications. Patients showed variable neurodevelopmental issues of variable severity. Breakpoints of the microduplications were non-recurrent, making interpretation of the CNV and determination of their clinical relevance difficult. Here, we report on two patients with 14q11.2 microduplication encompassing CHD8 and SUPT16H, one of whom had normal intelligence. Review of previous reports describing patients with comparable microduplications allowed for a more precise delineation of the condition and widening of the phenotypic spectrum.

  相似文献   
2.
Magnetic field generated by neuronal activity could alter magnetic resonance imaging (MRI) signals but detection of such signal is under debate. Previous researches proposed that magnitude signal change is below current detectable level, but phase signal change (PSC) may be measurable with current MRI systems. Optimal imaging parameters like echo time, voxel size and external field direction, could increase the probability of detection of this small signal change. We simulate a voxel of cortical column to determine effect of such parameters on PSC signal. We extended a laminar network model for somatosensory cortex to find neuronal current in each segment of pyramidal neurons (PN). 60,000 PNs of simulated network were positioned randomly in a voxel. Biot–savart law applied to calculate neuronal magnetic field and additional phase. The procedure repeated for eleven neuronal arrangements in the voxel. PSC signal variation with the echo time and voxel size was assessed. The simulated results show that PSC signal increases with echo time, especially 100/80 ms after stimulus for gradient echo/spin echo sequence. It can be up to 0.1 mrad for echo time = 175 ms and voxel size = 1.48 × 1.48 × 2.18 mm3. With echo time less than 25 ms after stimulus, it was just acquired effects of physiological noise on PSC signal. The absolute value of the signal increased with decrease of voxel size, but its components had complex variation. External field orthogonal to local surface of cortex maximizes the signal. Expected PSC signal for tactile detection in the somatosensory cortex increase with echo time and have no oscillation.  相似文献   
3.
4.
5.
6.
Farnesyltransferase (FTase) is one of the prenyltransferase family enzymes that catalyse the transfer of 15-membered isoprenoid (farnesyl) moiety to the cysteine of CAAX motif-containing proteins including Rho and Ras family of G proteins. Inhibitors of FTase act as drugs for cancer, malaria, progeria and other diseases. In the present investigation, we have developed two structure-based pharmacophore models from protein–ligand complex (3E33 and 3E37) obtained from the protein data bank. Molecular dynamics (MD) simulations were performed on the complexes, and different conformers of the same complex were generated. These conformers were undergone protein–ligand interaction fingerprint (PLIF) analysis, and the fingerprint bits have been used for structure-based pharmacophore model development. The PLIF results showed that Lys164, Tyr166, TrpB106 and TyrB361 are the major interacting residues in both the complexes. The RMSD and RMSF analyses on the MD-simulated systems showed that the absence of FPP in the complex 3E37 has significant effect in the conformational changes of the ligands. During this conformational change, some interactions between the protein and the ligands are lost, but regained after some simulations (after 2 ns). The structure-based pharmacophore models showed that the hydrophobic and acceptor contours are predominantly present in the models. The pharmacophore models were validated using reference compounds, which significantly identified as HITs with smaller RMSD values. The developed structure-based pharmacophore models are significant, and the methodology used in this study is novel from the existing methods (the original X-ray crystallographic coordination of the ligands is used for the model building). In our study, along with the original coordination of the ligand, different conformers of the same complex (protein–ligand) are used. It concluded that the developed methodology is significant for the virtual screening of novel molecules on different targets.  相似文献   
7.
This paper takes a somewhat slant perspective on flourishing and care in the context of suffering, death and dying, arguing that care in this context consists principally of ‘acts of work and courage that enable flourishing’. Starting with the perception that individuals, society and health care professionals have become dulled to death and the process of dying in Western advanced health systems, it suggests that for flourishing to occur, both of these aspects of life need to be faced more directly. The last days of life need to be ‘undulled’. Reflections upon the experiences of the author as carer and daughter in the face of her mother’s experience of death are used as basis for making suggestions about how care systems and professionals might better assist people in dealing with ‘the most grown up thing’ humans ever do, which is to die.  相似文献   
8.
9.
Advancing nanomedicines from concept to clinic requires integration of new science with traditional pharmaceutical development. The medical and commercial success of nanomedicines is greatly facilitated when those charged with developing nanomedicines are cognizant of the unique opportunities and technical challenges that these products present. These individuals must also be knowledgeable about the processes of clinical and product development, including regulatory considerations, to maximize the odds for successful product registration. This article outlines these topics with a goal to accelerate the combination of academic innovation with collaborative industrial scientists who understand pharmaceutical development and regulatory approval requirements—only together can they realize the full potential of nanomedicines for patients.  相似文献   
10.
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-23

京公网安备 11010802026262号