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   20619篇
  免费   1582篇
  国内免费   704篇
耳鼻咽喉   39篇
儿科学   216篇
妇产科学   147篇
基础医学   847篇
口腔科学   139篇
临床医学   1493篇
内科学   2553篇
皮肤病学   276篇
神经病学   1879篇
特种医学   199篇
外国民族医学   1篇
外科学   751篇
综合类   2241篇
一般理论   3篇
预防医学   1182篇
眼科学   158篇
药学   8770篇
  8篇
中国医学   1270篇
肿瘤学   733篇
  2024年   65篇
  2023年   333篇
  2022年   490篇
  2021年   700篇
  2020年   695篇
  2019年   764篇
  2018年   771篇
  2017年   831篇
  2016年   730篇
  2015年   726篇
  2014年   1456篇
  2013年   2239篇
  2012年   1313篇
  2011年   1378篇
  2010年   1111篇
  2009年   907篇
  2008年   858篇
  2007年   886篇
  2006年   732篇
  2005年   657篇
  2004年   546篇
  2003年   532篇
  2002年   384篇
  2001年   364篇
  2000年   283篇
  1999年   240篇
  1998年   225篇
  1997年   215篇
  1996年   212篇
  1995年   187篇
  1994年   155篇
  1993年   187篇
  1992年   182篇
  1991年   137篇
  1990年   132篇
  1989年   106篇
  1988年   116篇
  1987年   75篇
  1986年   87篇
  1985年   127篇
  1984年   113篇
  1983年   82篇
  1982年   92篇
  1981年   61篇
  1980年   70篇
  1979年   55篇
  1978年   63篇
  1977年   56篇
  1976年   47篇
  1975年   43篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
1.
Abstract

This study was undertaken to compare the concentrations of pro- and anti-angiogenic growth factors, nitric oxide (NO) stable metabolites in maternal serum and embryonic left ventricular (LV) isovolumic relaxation time (IRT, ms) during the first trimester in two groups of women: with pregnancy conceived by assisted reproductive technologies (ART, n?=?39) and normally conceived (control group, n?=?68) pregnancy. The concentration of vasoconstrictor endothelin 1 was 45.5 times more in ART than in control group. On the contrary, the concentrations of NO stable metabolites in ART were 1.9 times less than in control women. The assessment of angiogenic suppressors in ART women demonstrates the decrease in s-endoglin concentration was 1.6 times and in soluble receptor to vascular endothelial growth factor concentration was 2.0 times in comparison with control group. There was a significant increase in LV IRT in ART embryos in comparison to control ones. These data suggest significant changes in pro- anti-angiogenic factors balance and increase in vascular impedance in ART-conceived embryos.  相似文献   
2.
Systemic (s.c.) administration of aminooxyacetic acid (AOAA) in mice triggered clonic convulsions with a CD50 (convulsive dose) of 68 mg/kg (range 54-86). AOAA also induced clonic convulsions in mice subjected to intracerebroventricular administration of the drug with a CD50 of 0.04 mumols (range 0.028-0.06). At the onset of convulsions induced by systemic AOAA (CD97;150 mg/kg), the GAD activity in the frontal cortex and hippocampus was not affected. GABA mimetic drugs, progabide and gabaculine, had no effect on convulsions induced by AOAA. Convulsions induced by systemic administration of AOAA were blocked by diazepam, phenobarbital, and valproate. Ethosuximide, trimethadione, acetazolamide, diphenylhydantoin, and carbamazepine remained ineffective. L-Phenylisopropyladenosine was also found to protect mice against AOAA-induced convulsions, whereas atropine and baclofen had no effect. The seizures induced by intracerebroventricular administration of AOAA (CD97; 0.1 mumols) were blocked by coadministration of preferential N-methyl-D-aspartate antagonists, D-(-)-2-aminophosphonoheptanoic (AP7), 3-[+/-)-2-carboxypiperazine-4-yl)-propyl-1-phosphonic (CPP), and kynurenic acid (KYNA); preferential quisqualate/kainate antagonists, 6-cyano-7-nitro-quinoxaline-2,3-dione and gamma-D-glutamylaminomethylsulphonic acid, remained inactive in the range of dosages sufficient to block seizures induced by quisqualic acid or kainic acid. The antagonistic action of antiepileptic drugs effective against seizures induced by excitatory amino acids (diazepam and valproate), and drugs acting on excitatory amino acid receptors (AP7, CPP, and KYNA) upon seizures induced by AOAA suggests an involvement of excitatory neurotransmission in the convulsant action of the drug.  相似文献   
3.
Abstract:   A 19-year-old woman presented at our hospital with acute urinary retention in September 2005. She had experienced the same chief complaint twice previously. She had used non-steroidal anti-inflammatory drugs before acute urinary retention. The results of physical examinations were unremarkable, and her neurologic signs were not remarkable. The basic laboratory test values were all normal and a psychiatric assessment indicated that her symptoms were not psychogenic. Magnetic resonance imaging was carried out, but revealed only a slight bulging in the L3/L4/L5 disk. Water cystometry showed acontractile detrusor. We made a diagnosis of acute urinary retention as a result of non-steroidal anti-inflammatory drugs because of her use of such drugs before the development of symptoms on multiple occasions. This patient was regularly followed up as an outpatient, and she could void smoothly in February 2006. This is the first report which acute urinary retention associated with non-steroidal anti-inflammatory drugs in Japan.  相似文献   
4.
In search of potential drugs for the treatment of estrogen- and androgen-dependent cancer as well as the prophylaxis of metastases, tetralones, tetralins, and dihydronaphthalenes bearing a OCH3 substituent at the benzene nucleus and an imidazol-4-yl, imidazol-1-yl, or 1,2,4-triazol-1-yl substituent in 2-position were synthesized with and without C1-spacer between the rings (compounds 2 – 26 ). The compounds were tested in vitro for inhibition of the three target enzymes P450 arom (human placental microsomes), P450 17 (rat testicular microsomes), and P450 TxA2 (citrated human whole blood). To examine selectivity, some compounds were further tested in vitro for inhibition of P450 18 (bovine adrenal mitochondria), P450 see (bovine adrenal mitochondria) and corticoid formation (aldosterone, corticosterone; ACTH stimulated rat adrenal tissue). In vivo, selected compounds were examined in Sprague Dawley rats regarding P450 TxA2 inhibition, reduction of plasma testosterone concentration, antiuterotrophic activity (inhibition of the uterotrophic activity of androstenedione), reduction of plasma estradiol concentration (pregnant mares' serum gonadotropin-primed rats), and mammary tumor inhibiting activity (dimethylbenzanthracene-induced tumor; pre- and postmenopausal model). In the series of imidazol-4-yl compounds, which represent a novelty in the field of azole inhibitors of steroidogenic P450 enzymes, strong inhibitors of P450 arom and/or P450 17 were found: 7-OCH3-2-(imidazol-4-ylmethylene)-1-tetralone ( 4 ) and 7-OCH3-2-(imidazol-4-ylmethyl)-tetralin ( 12 ) are among the most potent inhibitors of P450 arom in vitro known so far. Compound 4 is a selective inhibitor, whereas 12 shows in addition strong inhibition of P450 17. In contrast to 12 , the 6-OCH3 derivative (compound 11 ) is a selective inhibitor of P450 17, being 50 times more potent than ketoconazole. Some imidazol-1-yl compounds show a marked inhibition of P450 TxA2: 2-(imidazol-1-ylmethyl)-1-tetralone ( 13 ) is a selective inhibitor of P450 TxA2, whereas 7-OCH3-2-(imidazol-1-ylmethyl)-tetralin ( 17 ) as well as 2-(imidazol-1-ylmethyl)-tetralin ( 16 ) and 7-OCH3-2-imidazol-1-yl-3,4-dihydronaphthalene ( 25 ) additionally show strong inhibition of P450 arom and P450 17. Regarding the other steroidogenic P450 enzymes as well as corticosterone formation, the compounds show only little inhibitory activity. Aldosterone formation, however, is inhibited at low concentrations. Nevertheless, 4 and 12 are more selective, i.e. inhibit aldosterone synthesis less than the well known inhibitor of P450 arom fadrozole. The compounds show activity in the aforementioned in vivo tests.  相似文献   
5.
Although cardiac arrhythmias remain a serious clinical problem in many patients with heart disease, the exact role of antiarrhythmic drug therapy is currently under intense evaluation. Within the last several years it has become clear that there are significant risks as well as potential benefits associated with existing agents. Ongoing studies in large patient populations should help determine the benefit/risk ratio of traditional therapy. Regardless of the outcome of these trials, current electrophysiological dogma will have to be re-evaluated and newer concepts evolve for drug development to make further progress. The goal of this symposium is to exchange information among basic and clinical investigators so as to facilitate the emergence of novel electrophysiological concepts that will form the basis for future generations of antiarrhythmic drugs.  相似文献   
6.
7.
Summary: We studied the effect of antiepileptic drugs (AEDs) on internal carotid artery (ICA) blood flow velocity, as an index of total cerebral blood flow (CBF). The subjects were 45 newly diagnosed children with febrile convulsion or epilepsy who were seizure-free for a period long enough not to affect the results. They had no neurologic deficit, received fixed monotherapy, and were examined by a noninvasive Doppler ultrasound method, in comparisonwith 13 age-matched normal volunteers with no AED. In 30 patients, the measurements were performed before and after AED administration [10 with phenobarbital (PB), 10 with carbamazepine (CBZ), and 10 with valproate (VPA)], and performed before and after AED discontinuation in the remaining 15 patients (all with PB). Normal volunteers underwent the two consecutive examinations with a mean interval equal to that of the entire patient group, and there was no difference in velocity values between the measurements. In patients receiving CBZ or VPA, a significant reduction was noted in blood flow velocity after drug administration. Although velocity values in the patients receiving PB did not change after drug administration, they were significantly increased after complete discontinuation. In the present study, a slight but significant reduction in CBF caused by AED administration at therapeutic doses in children was suggested.  相似文献   
8.
A case of partially reversible chronic renal failure due tolong-term NSAID use is discussed. An analysis of this and similarcases recently reported indicates many similarities betweenchronic NSAID nephropathy and analgesic nephropathy.  相似文献   
9.
Summary The influence of antiepileptics on the evolution of rat amygdaloid kindling was studied.Under placebo conditions clonic convulsions and a spike-wave EEG pattern developed. Diazepam, clonazepam, clobazam and phenobarbital were most effective in suppressing the evolution of kindling; the effects of valproate sodium, ethosuximide and acetazolamide were somewhat less pronounced in this respect. Carbamazepine, oxcarbazepine and phenytoin, on the other hand, enhanced kindling development, i.e. the increase in duration of after-discharge was faster than in the placebo group. The results indicate that under the above experimental conditions drugs with no anti-absence component can be distinguished from those with an anti-absence component. The mechanism of action underlying the observed effects is not yet known; the hypothesis that under special conditions protective inhibitory neuronal activity can develop to absence type seizures is proposed.  相似文献   
10.
空管药物疗法治疗牙髓病和根尖周病疗效观察   总被引:1,自引:0,他引:1  
用SMTD复合药物对牙髓病和根尖周病实施空管药物疗法。78例103颗获得完整随访资料患牙经两年观察,92.2%治愈率。文章介绍了治疗方法,讨论了空管药物疗法的愈合机理、优点、失败原因及其预防措施。  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