全文获取类型
收费全文 | 2162篇 |
免费 | 100篇 |
国内免费 | 5篇 |
专业分类
耳鼻咽喉 | 9篇 |
儿科学 | 28篇 |
妇产科学 | 24篇 |
基础医学 | 391篇 |
口腔科学 | 37篇 |
临床医学 | 125篇 |
内科学 | 752篇 |
皮肤病学 | 14篇 |
神经病学 | 133篇 |
特种医学 | 104篇 |
外科学 | 255篇 |
综合类 | 4篇 |
预防医学 | 61篇 |
眼科学 | 22篇 |
药学 | 107篇 |
中国医学 | 3篇 |
肿瘤学 | 198篇 |
出版年
2023年 | 9篇 |
2022年 | 21篇 |
2021年 | 31篇 |
2020年 | 25篇 |
2019年 | 31篇 |
2018年 | 43篇 |
2017年 | 19篇 |
2016年 | 39篇 |
2015年 | 46篇 |
2014年 | 59篇 |
2013年 | 67篇 |
2012年 | 85篇 |
2011年 | 109篇 |
2010年 | 49篇 |
2009年 | 49篇 |
2008年 | 104篇 |
2007年 | 99篇 |
2006年 | 84篇 |
2005年 | 93篇 |
2004年 | 84篇 |
2003年 | 119篇 |
2002年 | 138篇 |
2001年 | 87篇 |
2000年 | 77篇 |
1999年 | 105篇 |
1998年 | 38篇 |
1997年 | 26篇 |
1996年 | 25篇 |
1995年 | 14篇 |
1994年 | 17篇 |
1993年 | 9篇 |
1992年 | 44篇 |
1991年 | 35篇 |
1990年 | 44篇 |
1989年 | 64篇 |
1988年 | 30篇 |
1987年 | 40篇 |
1986年 | 30篇 |
1985年 | 22篇 |
1984年 | 26篇 |
1983年 | 18篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 14篇 |
1978年 | 9篇 |
1977年 | 8篇 |
1973年 | 6篇 |
1970年 | 7篇 |
1968年 | 5篇 |
1966年 | 6篇 |
排序方式: 共有2267条查询结果,搜索用时 31 毫秒
1.
Michiko Oka Y. Itoh Shigeru Tatsumi F.-H. Ma Yojiro Ukai Yoshiaki Yoshikuni Kiyoshi Kimura 《Naunyn-Schmiedeberg's archives of pharmacology》1997,356(2):189-196
The effect of (+)-5-oxo-D-prolinepiperidinamide monohydrate (NS-105), a novel cognition enhancer, on adenylate cyclase activity
was investigated in cultured neurons of the mouse cerebral cortex. NS-105 (10–7 and 10–6 M) inhibited forskolin-stimulated cyclic AMP formation, an action that was dependent on pertussis toxin-sensitive G proteins.
Conversely, in pertussis toxin-pretreated neurons, NS-105 (10–7 –10–5 M) significantly enhanced the forskolin-stimulated cyclic AMP formation, and this action was completely reversed by cholera
toxin. A metabotropic glutamate receptor agonist (1S, 3R)-1-aminocyclopentane-1, 3-dicarboxylic acid (1S, 3R-ACPD) produced
similar bi-directional actions on the cyclic AMP formation. Both of these inhibitory and facilitatory actions of NS-105 and
1S, 3R-ACPD were blocked by L(+)-2-amino-3-phosphopropinoic acid (L-AP3). NS-105 (10–6 M) and 1S, 3R-ACPD (10–4 M) significantly enhanced isoproterenol- and adenosine-stimulated cyclic AMP formation. The enhancement of such Gs-coupled
receptor agonists-stimulated cyclic AMP formation was also produced by quisqualate but not by L(+)-2-amino-4-phosphonobutanoate
(L-AP4). The phosphoinositides hydrolysis was enhanced by 1S, 3R-ACPD (10–4 M) but not by NS-105 (10–6 M), however, 1S, 3R-ACPD-induced increase in phosphoinositides turnover was attenuated by NS-105. These findings suggest
that NS-105 stimulates metabotropic glutamate receptor subclasses that are coupled both negatively and positively to adenylate
cyclase, but it acts as an antagonist at the receptor subclasses that are linked to phosphoinositides hydrolysis.
Received: 3 February 1997 / Accepted: 25 April 1997 相似文献
2.
3.
4.
5.
An instrument was developed to detect the shift in scattering of laser light that occurs when particles in suspension move in a chamber with an electrical load. The instrument measures the zeta potential of particles. We applied the instrument to study human blood cells. Platelet-rich plasma was used because of the stability of the suspension, without the sedimentation or autoaggregation that is often seen with red or white blood cells. The reproducibility of the measurements was satisfactory when there were enough platelets in the suspension. Platelets from healthy controls (n = 136) had a potential of -14.20 +/- 1.64 mV at the detection angle of 17.1 degrees. Platelets from patients with essential thrombocytosis (n = 16) or polycythemia vera (n = 8) had higher potentials than the healthy controls. 相似文献
6.
A case of Raeder's syndrome caused by metastatic malignant lymphoma was reported. The patient was 67-year-old male. He had complained of diplopia, ptosis and frontal headache at the left side. Neurological examinations revealed left incomplete Horner's syndrome (miosis and ptosis, but normal facial sweating) and left abducens palsy, which was considered to be Raeder's syndrome Group 1 (Boniuk and Schlazinger's classification). CT scan, MRI and angiography demonstrated a mass lesion in the left cavernous sinus extending to the sphenoparietal sinus, and a mass lesion in the anterior part of the superior sagittal sinus. During his hospitalization, enlargement of the left cervical lymph nodes was noticed. "Malignant lymphoma (non-Hodgkin)" was diagnosed on the basis of biopsy. Group 1 of Raeder's syndrome is rare, but it is important to define the site of lesion, which is located around the paratrigeminal region at the middle cranial fossa. Because these lesions are very small and metastatic in many cases, various neuroradiological investigations, especially MRI, are necessary for early diagnosis and early treatment. 相似文献
7.
Identification of a large novel imprinted gene cluster on mouse proximal chromosome 6 总被引:15,自引:0,他引:15
下载免费PDF全文
![点击此处可从《Genome research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Mice with maternal duplication of proximal chromosome 6 die in utero at an early embryonic stage. Recently, two imprinted genes, paternally expressed Sgce and maternally expressed Asb4, were identified in this region. This report analyzes the imprinting status of genes within a 1-Mb region containing these two genes. Peg10, which is next to Sgce, shows complete paternal expression, like Sgce. Conversely, Neurabin, Pon2, and Pon3 show preferential maternal expression at embryonic stages, although they all show biallelic expression in neonatal tissues. These results demonstrate that there is a large novel imprinted gene cluster in this region. 5'-RACE (Rapid Amplification of cDNA Ends) analysis of Peg10 revealed the existence of a novel first exon separate from the second exon, which encoded two putative ORFs similar to the viral Gag and Pol proteins. A differentially methylated region established in sperm and eggs is located just within the region containing the two first exons of Peg10 and Sgce, and may play an important role in regulating the two paternally expressed genes: Peg10 and Sgce. 相似文献
8.
FGF signaling segregates biliary cell-lineage from chick hepatoblasts cooperatively with BMP4 and ECM components in vitro. 总被引:2,自引:0,他引:2
Masaaki Yanai Norifumi Tatsumi Noboru Hasunuma Kenjiro Katsu Fumio Endo Yuji Yokouchi 《Developmental dynamics》2008,237(5):1268-1283
Intrahepatic bile ducts (IHBDs) are indispensable for transporting bile secreted from hepatocytes to the hepatic duct. The biliary epithelial cells (BECs) of the IHBD arise from bipotent hepatoblasts around the portal vein, suggesting the portal mesenchyme is essential for their development. However, except for Notch or Activin/TGF-beta signaling molecules, it is not known which molecules regulate IHBD development. Here, we found that FGF receptors and BMP4 are specifically expressed in the developing IHBD and the hepatic mesenchyme, respectively. Using a mesenchyme-free culture of liver bud, we showed that bFGF and FGF7 induce the hepatoblasts to differentiate into BECs, and that BMP4 enhances bFGF-induced BEC differentiation. The extracellular matrix (ECM) components in the hepatic mesenchyme induced BEC differentiation. Forced expression of a constitutively active form of the FGF receptor partially induced BEC differentiation markers in vivo. These data strongly suggest that bFGF and FGF7 promote BEC differentiation cooperatively with BMP4 and ECMs in vivo. 相似文献
9.
Yoshio Hiasa Noriyuki Ito Masato Ohshima Tomoyoshi Ohmori Asao Seki Toshikazu Tatsumi Hiromu Yokoi Chikayoshi Iwata Yoshio Murata Nobuyuki Ito † 《Pathology international》1978,28(4):637-644
Light and electron microscopic studies have been made on an anaplastic giant-cell tumor that developed in a woman 8 years after an operation on the thyroid for papillary carcinoma. Many giant cells were observed in the anaplastic tumor tissue, but no follicles. Numerous tightly-packed mitochondria and abundant ribosomes were present, but there were no desmosomes. The basement membrane was not distinct. 相似文献
10.
Cross-linking of Fc(gamma)-receptor on monocytes inhibits hepatitis C virus-specific cytotoxic T-lymphocyte induction in vitro. 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《Immunology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
T Kanto N Hayashi T Takehara K Katayama A Ito K Mochizuki N Kuzushita T Tatsumi Y Sasaki A Kasahara M Hori 《Immunology》1998,94(4):461-468
In hepatitis C virus (HCV) infection, immune complex (IC)-type virus particles are frequently observed in circulation. The IC leads to cross-linking of Fcgamma receptors (FcgammaR) on monocytes and exerts immunoinhibitory function. To test the roles of IC in HCV-specific cytotoxic T lymphocyte (CTL) induction, we generated HCV CTL from peripheral blood mononuclear cells of chronic hepatitis C patients with or without HCV-IC- or immunoglobulin G (IgG)-coated culture plates and compared their lytic activities. HCV-IC or adherent IgG, which induces FcgammaR cross-linking, significantly reduced CTL activity. Expression of B7-1 on monocytes decreased on adherent IgG. In addition, tumour necrosis factor-alpha (TNF-alpha) and transforming growth factor-beta1 (TGF-beta1) production increased from cells on adherent IgG and their mRNA expression in monocytes was enhanced. Anti-TNF-alpha antibody during induction on adherent IgG inhibited lysis; however, anti-TGF-beta completely reversed its inhibitory effect. These results demonstrated that HCV-IC or adherent IgG impaired HCV-CTL induction in vitro. The FcgammaR-mediated CTL suppression occurred via decreased expression of monocyte B7-1 and/or enhanced production of TGF-beta1. 相似文献