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   810篇
  免费   62篇
  国内免费   3篇
耳鼻咽喉   6篇
儿科学   63篇
妇产科学   12篇
基础医学   166篇
口腔科学   14篇
临床医学   69篇
内科学   133篇
皮肤病学   16篇
神经病学   72篇
特种医学   10篇
外科学   54篇
综合类   12篇
预防医学   52篇
眼科学   16篇
药学   107篇
中国医学   8篇
肿瘤学   65篇
  2021年   14篇
  2020年   10篇
  2019年   7篇
  2018年   15篇
  2017年   15篇
  2016年   14篇
  2015年   13篇
  2014年   12篇
  2013年   31篇
  2012年   38篇
  2011年   31篇
  2010年   28篇
  2009年   29篇
  2008年   45篇
  2007年   42篇
  2006年   37篇
  2005年   36篇
  2004年   44篇
  2003年   45篇
  2002年   44篇
  2001年   9篇
  2000年   5篇
  1999年   5篇
  1998年   6篇
  1997年   7篇
  1996年   5篇
  1995年   6篇
  1993年   11篇
  1992年   13篇
  1991年   9篇
  1990年   16篇
  1989年   16篇
  1988年   12篇
  1987年   19篇
  1986年   11篇
  1985年   15篇
  1984年   10篇
  1983年   15篇
  1982年   10篇
  1981年   5篇
  1980年   10篇
  1979年   7篇
  1978年   5篇
  1977年   7篇
  1975年   7篇
  1974年   5篇
  1973年   6篇
  1971年   8篇
  1964年   6篇
  1960年   4篇
排序方式: 共有875条查询结果,搜索用时 390 毫秒
81.
“Special therapies” (homoeopathy, anthroposophical medicine, and phytotherapy) play a particular role in the field of unconventional, i. e. scientifically unproved and not generally acknowledged medicaments and measures. This is because-contrary to other such methods-they are incorporated in medicament and social insurance regulations. However, conditions of release and/or registration of these medicaments which, according to the 1976 German law, are facilitated, do not conform to international standard of medicament examination. Therefore, rigorous execution of these rules would ruin any chance of these hitherto admitted “particular medicaments” to stay on the market. It is these commercial considerations which play an essential part in the discussion about indispensable requirements of medicament examination. This is demonstrated in detail. It is recommended to give preference to efforts on behalf of medicament safety as well as conformity to international standards. This would be in the best interest of the people.  相似文献   
82.
Focal cerebral lesions in the rat brain induced by photothrombosis cause hyperexcitability of the surrounding brain. This can be demonstrated in brain slices taken from animals several days after lesioning, by analysis of field potential responses to paired-pulse stimulation. We now investigated whether and how these remote effects of a cortical lesion can be modified pharmacologically. Application of the NMDA receptor antagonist, MK-801 ((+)-5-methyl-10,11-dihydro-5H-dibnzo[a,d]cyclohepten-5,10-imine), was shown to block induction of immediate early genes and activation of astrocytes as evidenced by glial fibrillary acidic protein (GFAP) staining in the photothrombosis model. However, MK-801 did not affect the hyperexcitability that had been demonstrated by field potential recordings in brain slices. In another series of experiments, lubeluzole ((+)-(S)-4-(2-benzothiazolylmethylamino)--[(3,4-difluorophenoxy)methyl]-1-piperidineethanol), which inhibits the glutamate-activated nitric oxide pathway as evidenced by down-regulation of intracellular cyclic GMP, was given immediately after induction of the insult. This reduced hyperexcitability as investigated 7 days later. In the light of these data one can suggest that a nitric oxide-cyclic GMP-related mechanism may be responsible for functional alterations in the surround of photothrombotic brain lesions.  相似文献   
83.
Substance P- and calcitonin gene-related peptide-like immunoreactivities (SP-LI and CGRP-LI, respectively) were measured in superfusates of either superior sagittal sinus and transverse sinuses and attached dura mater or dura mater alone of guinea pig. Exposure of cerebral venous sinuses to capsaicin (1 microM) evoked the release of both SP-LI and CGRP-LI, which was no longer observed upon second challenge with the drug. Neuropeptide release was induced by 80 mM K+ either at the first or second administration. Bradykinin (10 microM) increased the outflow of CGRP-LI, but not of SP-LI, from cerebral venous sinuses. In vitro capsaicin pretreatment (10 microM) or incubation with 10 microM indomethacin completely abolished the bradykinin-evoked CGRP-LI release. Capsaicin (1 microM) failed to evoke release from dura mater without major intracranial venous vessels. Sensory neuropeptide released from the cerebral venous sinuses may take part in certain symptoms, such as vasodilatation and inflammation accompanying the pain of the migraine attack. Bradykinin, putatively via prostanoid generation, may participate in this event.  相似文献   
84.
85.
Ten T-cell acute lymphoblastic (T-ALL) CEM cell lines selected for resistance toward methotrexate (CEM/MTX60PGA, CEM/MTX140LV, CEM/MTX1500LV, CEM/MTX5000PGA, CEM/MTXR1, CEM/MTXR2, and CEM/MTXR3), doxorubicin (CEM/ADR5000), vincristine (CEM/VCR1000), or hydroxyurea (CEM/HUR90), respectively, and parental drug-sensitive CCRF-CEM cells were analyzed using comparative genomic hybridization. Most genomic imbalances were not specific for drug resistance, as they were found in both parental and drug-resistant lines. Three aberrations were common to all or most cell lines analyzed: dim(5q35), dim(9p21p24), and enh(20q). We were concerned on those imbalances which were specifically present in drug-resistant but not in drug-sensitive cells. All methotrexate-resistant cell lines were characterized by an enhancement or an amplification of 5q13. The methotrexate resistance-conferring dihydrofolate reductase (DHFR) gene is located at this locus. Gain of DHFR was verified by PCR analyses. CEM/MTX60PGA, CEM/MTX140LV, CEM/MTX1500LV, and CEM/MTX5000PGA showed enh(14q21qter) and CEM/MTX5000PGA amp(5p13p15.2). These two loci harbor the methylenetetrahydrofolate dehydrogenase (MTHFD1) and 5'-methyltetrahdrofolate-homocysteine methyltransferase reductase (MTRR) genes, both of which are involved in folate metabolism. Their gain indicates a role in methotrexate resistance. A loss of 4q35 was found in CEM/MTXR2, CEM/MTXR3, and CEM/ADR5000 where the proapoptotic caspase-3 gene is located. The thioredoxin (TXN) locus 9q31 was enhanced in CEM/ADR5000 and CEM/MTX5000PGA cells. 2p22pter was increased in hydroxyurea-resistant CEM/HUR90 cells. Ribonucleotide reductase polypeptide M2 (RRM2), which confers resistance to hydroxyurea, resides at this locus. Other specific genomic imbalances in drug-resistant cell lines were dim(1p36.5), enh(4p), dim(8p22pter), enh(12p13), dim(17p), enh(18q12), enh(21q22.2), dim(21q22.2), and dim(22q13). All genomic imbalances were subjected to hierarchical cluster analysis and clustered image mapping to identify profiles of chromosomal aberrations in the cell lines. The obtained dendrograms allowed separation of imbalances common to all or most cell lines from other more individual aberrations. Furthermore, methotrexate-resistant cell lines clustered together. Our future efforts will be directed toward those imbalances which implicate still unknown candidate drug resistance genes.  相似文献   
86.
MRP14 (S100A9) is the major calcium-binding protein of neutrophils and monocytes. Targeted gene disruption reveals an essential role of this S100 protein for transendothelial migration of phagocytes. The underlying molecular mechanism comprises major alterations of cytoskeletal metabolism. MRP14, in complex with its binding partner MRP8 (S100A8), promotes polymerization of microtubules. MRP14 is specifically phosphorylated by p38 mitogen-activated protein kinase (MAPK). This phosphorylation inhibits MRP8/MRP14-induced tubulin polymerization. Phosphorylation of MRP14 is antagonistically regulated by binding of MRP8 and calcium. The biologic relevance of these findings is confirmed by the fact that MAPK p38 fails to stimulate migration of MRP14(-/-) granulocytes in vitro and MRP14(-/-) mice show a diminished recruitment of granulocytes into the granulation tissue during wound healing in vivo. MRP14(-/-) granulocytes contain significantly less polymerized tubulin, which subsequently results in minor activation of Rac1 and Cdc42 after stimulation of p38 MAPK. Thus, the complex of MRP8/MRP14 is the first characterized molecular target integrating MAPK- and calcium-dependent signals during migration of phagocytes.  相似文献   
87.
Suppression of estrogen, via estrogen receptor or aromatase blockade, is being investigated in the treatment of different conditions. Exemestane (Aromasin) is a potent and selective irreversible aromatase inhibitor. To characterize its suppression of estrogen and its pharmacokinetic (PK) properties in males, healthy eugonadal subjects (14-26 yr of age) were recruited. In a cross-over study, 12 were randomly assigned to 25 and 50 mg exemestane daily, orally, for 10 d with a 14-d washout period. Blood was withdrawn before and 24 h after the last dose of each treatment period. A PK study was performed (n = 10) using a 25-mg dose. Exemestane suppressed plasma estradiol comparably with either dose [25 mg, 38% (P 相似文献   
88.
M Battistel  M Plebani  F Di Mario  M Jocic  I T Lippe    P Holzer 《Gut》1993,34(12):1688-1692
Chronic cigarette smoking has adverse effects on peptic ulcer disease because the healing of ulcers is delayed and the incidence of relapses is enhanced. Short term intake of nicotine induces vascular damage in the rat gastric mucosa, but the pathophysiological mechanisms of nicotine's action in the stomach are largely unknown. In this study rats were treated with nicotine, added to their drinking water, for 50 days. They were then anaesthetised and their stomachs perfused with acidified acetylsalicylic acid (ASA). Chronic nicotine treatment failed to change the effects of acidified ASA to induce gastric mucosal acid back diffusion, haemorrhagic damage and bleeding. Basal blood flow in the gastric mucosa was also unchanged by chronic nicotine intake, whereas the mucosal hyperaemia evoked by ASA induced acid back diffusion was averted. The concentrations of sulfidoleukotrienes were significantly augmented in the gastric wall of nicotine treated rats. These data show that chronic nicotine intake causes dysregulation of the gastric microcirculation, an effect that is associated with biochemical changes in the stomach. This study thus substantiates the adverse effects of smoking on gastric mucosal pathophysiology. These data suggest that inappropriate regulation of gastric mucosal blood flow inhibits recovery from gastric mucosal injury in smokers.  相似文献   
89.
Fifty-three patients with a suspected first anterior wall acute myocardial infarction (AMI) were randomized to intervention with intravenous heparin followed by oral warfarin (26 patients) or matching placebo (27 patients). The regimen was started within 12 hours after the onset of AMI. Anticoagulation was maintained at a therapeutic level (for heparin, activated partial thromboplastin time 70 to 140 seconds; for warfarin, thrombotest 5 to 10%) for 10 days, and no bleeding episodes occurred. The baseline characteristics of the 2 study groups were well matched. In 7 patients in the placebo group and in none in the anticoagulant group, left ventricular thrombus developed during the study, as detected by serial 2-dimensional echocardiography. Early intervention with high-dose anticoagulant drugs may prevent the development of left ventricular thrombus in anterior wall AMI.  相似文献   
90.
The present report describes a 19-yr-old female with progressive hypopituitarism and diabetes insipidus. Pneumoencephalography demonstrated gross atrophy of the hypothalamus and a small pituitary gland. In the face of documented hypothyroidism and hypogonadism, basal pituitary trophic hormones were consistently detectable and responded briskly to releasing factor administration. This combination of an atrophic lesion of the hypothalamus with gradually evolving hypopituitarism but detectable and stimulable anterior pituitary hormones appears to represent a unique form of hypothalamic failure.  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