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   18110篇
  免费   739篇
  国内免费   83篇
耳鼻咽喉   222篇
儿科学   401篇
妇产科学   142篇
基础医学   2108篇
口腔科学   483篇
临床医学   1033篇
内科学   4555篇
皮肤病学   294篇
神经病学   1484篇
特种医学   808篇
外科学   2897篇
综合类   78篇
预防医学   537篇
眼科学   684篇
药学   1258篇
中国医学   22篇
肿瘤学   1926篇
  2023年   69篇
  2022年   126篇
  2021年   301篇
  2020年   148篇
  2019年   202篇
  2018年   299篇
  2017年   245篇
  2016年   316篇
  2015年   319篇
  2014年   424篇
  2013年   573篇
  2012年   830篇
  2011年   944篇
  2010年   546篇
  2009年   468篇
  2008年   942篇
  2007年   1025篇
  2006年   1066篇
  2005年   1031篇
  2004年   1012篇
  2003年   942篇
  2002年   997篇
  2001年   476篇
  2000年   449篇
  1999年   485篇
  1998年   262篇
  1997年   231篇
  1996年   199篇
  1995年   184篇
  1994年   160篇
  1993年   160篇
  1992年   323篇
  1991年   278篇
  1990年   284篇
  1989年   310篇
  1988年   240篇
  1987年   219篇
  1986年   228篇
  1985年   207篇
  1984年   168篇
  1983年   133篇
  1982年   98篇
  1981年   80篇
  1980年   63篇
  1979年   99篇
  1978年   64篇
  1977年   77篇
  1975年   61篇
  1974年   56篇
  1973年   59篇
排序方式: 共有10000条查询结果,搜索用时 536 毫秒
51.
A case of bilateral blepharospasm who registered the efficacy of edrophonium was reported. The case is a 49-year-old female. She had been in good health until January, 1991 when she complained of difficulty in opening her eyes while driving. Thereafter the condition progressed to such a degree that she was unable to experience a comfortable life. Her blinking rate did not changed. The symptoms were triggered by stress or some physical action, such as walking or driving. They were attenuated by taking a bath, sleep or sedation. The severity of the symptoms varied during the day and from day to day. Neurological examination revealed bilateral spasms of the orbicular oculi muscles, and occasionally of the orbicular oris muscles, sternocleidmastoid muscles and the perinasal regions. Neither orolingual dyskinesia nor other involuntary movements were detected. Surface electromyography (EMG) disclosed tonic discharges mainly from the orbicular oculi muscles. The abnormal spasm disappeared with the injection of edrophonium chloride. The test for the serum antiacetylcholine receptor antibody was negative and a repetitive stimulation EMG showed no waning phenomenon. No thymoma or thymus abnormalities were detected by pneumomediastinography. A needle EMG revealed neurogenic change in the distal portion of the limbs. A single fiber EMG showed elongation of the jitter value and the blocking phenomenon. Although distigmine bromide was ineffective against the spasm, pyridostigmine bromide and the local injection of botulinum toxin were very effective.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
52.
Many reports about the increase of renal cell carcinoma patients have been published in Japan recently, however, the real fluctuations in the total number of patients in relation to the change of population have not been reported yet. Most of the patients with renal cell carcinoma in the last 10 years were examined in Chiba prefecture, which has a population of about five million and 25 active urological offices. Histologically confirmed cases were investigated by sending questionnaire letters. The items were as follows; sex, age, address, occupation, family history, past history, symptoms, examination methods that first detected the tumor, operation date, tumor diameter and clinical stage. Twenty two offices returned answers and 560 cases who lived in Chiba were found to have renal cell carcinoma from 1980 to 1989. Yearly incidence rates per 100,000 persons demonstrated a significant increase from 0.32 to 2.07. Small, asymptomatic and low stage cancers have been increasing rapidly, however, the rate of metastatic disease has not shown any decrease. The main cause of rapid increase seems to be attributed to progress in diagnostic methods and increase of early detection, but the possibility of an increase in some carcinogenic factors can not be ruled out.  相似文献   
53.
Abstract: Studies on the circadian rhythm of urine excretion in healthy men have demonstrated that the maximal urine flow occurs in the early afternoon and the minimal around midnight. In this study, an abnormality in the variation of urine volume was found in parkinsonian patients. Urine samples were collected during daytime (9:00–21:00) and nighttime (21:00–9:00). Fifteen healthy control subjects were examined and found to excrete 60% during the daytime and 40% during the nighttime of the total urine volume. Sixteen parkinsonian patients excreted 43% during the daytime and 57% during the nighttime. In contrast to the control subjects, the parkinsonian patients excreted a smaller volume of their urine during the daytime than during the nighttime. This finding might be related to the degeneration of dopaminergic and/or nondopaminergic neurons in the brain which control urinary excretion.  相似文献   
54.
Summary: In situ hybridization of mRNA for collagen IV, collagen VI, stromelysin (MMP-3) and TIMP1 was examined in renal biopsy specimens from patients with IgA nephropathy (IgAN) or diabetic nephropathy with various degrees of tissue damage. The majority of cells in the glomeruli expressed these mRNA almost simultaneously, but a few cells demonstrated positive expression for only one of these probes. There was a parallel relationship between the degree of tissue damage and that of mRNA expressions of these probes in patients with IgAN, while patients with diabetic nephropathy showed a reverse relationship between these two parameters. It is concluded that patients with mesangial proliferative glomerulonephritis expressed mRNA for collagen collagenase and its inhibitor in the glomeruli in parallel with the progress of tissue damage. In contrast, glomerular samples from patients with diabetic nephropathy showed that there was an inverse relationship between tissue damage and expression of mRNA. It is concluded that expression of collagen, collagenase and its inhibitor parallels the progression of glomerular changes in IgAN, but such parallel expression was not observed in patients with diabetic nephropathy.  相似文献   
55.
56.
57.
A bstract The purpose of this study was to assess the efficacy of nasal mask bi-level positive airway pressure (BiPAP) support in managing respiratory failure following cardiovascular surgery. A total of 20 patients requiring postoperative prolonged respiratory support of 72 hours or longer were studied. BiPAP support was used for eight patients (BiPAP group); the other 12 patients were managed using ordinary oxygen mask treatment (control group). The mean age of the BiPAP group and control group was 65 and 58 years of age, respectively. The mean period of postoperative endotracheal intubation of the BiPAP group and control group was 12 ± 5 days and 7 ± 1 days, respectively. Reintubation was necessary in two patients of the control group. The BiPAP group patients required no reintubation. BiPAP support was discontinued within 48 hours in 6 out of 8 patients. The respiratory rates of control group increased (p < 0.1) 24 hours after extubation, however, the respiratory rates of the BiPAP group remained unchanged. The values of the respiratory index of the BiPAP group improved significantly (p < 0.01) after BiPAP management (from 1.5 ± 0.2 to 0.9 ± 0.2). The values of the control group, however, remained unchanged. A-aDO2 and Qs/Qt decreased (p < 0.1) in the BiPAP group. There were no significant differences in central venous pressure or circulatory status between the two groups. In conclusion, BiPAP support is a noninvasive management technique for postoperative respiratory failure and may also prevent prolonged endotracheal intubation.  相似文献   
58.
PURPOSE: The association of BRCA2 polymorphisms at codon 372 [Asn (N)/His (H)]and codon 784 [Met (M)/Val (V)] with breast cancer risk was evaluated in Japanese women. In addition, the prognostic significance of these polymorphisms was studied in breast cancer patients. EXPERIMENTAL DESIGN: A case-control study was conducted to examine the association of the BRCA2 N/H372 polymorphism and M/V 784 polymorphism with breast cancer risk (cases = 149, controls = 154). The prognostic significance of these polymorphisms was evaluated in 139 patients with primary breast cancer. RESULTS: No significant association was observed between the N/H372 polymorphism and breast cancer risk. In contrast, a significant increase in breast cancer risk (odds ratio, 2.03; 95% confidence interval, 1.07-3.87) was observed in carriers of the variant allele (V784) of the M/V784 polymorphism as compared with noncarriers after adjustment for the classical risk factors, age, family history, parity, body mass index, and so forth. Among breast cancer patients, various clinicopathological parameters including menopausal status, tumor size, lymph node status, histological grade, and estrogen-receptor status were not significantly different between the carriers and noncarriers of the variant allele with regard to both N/H372 and M/V784 polymorphisms. The N/H 372 polymorphism was not significantly associated with patient prognosis. On the other hand, breast cancer patients carrying the variant allele of M/V784 polymorphism showed a significantly (P = 0.014) lower 3-year disease-free survival rate (63%) than noncarriers (92%). Multivariate analysis has revealed that the M/V784 polymorphism is a significant prognostic factor, being independent of the other conventional prognostic factors such as lymph node status and estrogen receptor status. CONCLUSION: These results suggest that the M/V784 polymorphism, but not the N/H372 polymorphism, would be useful in the selection of women at high risk for developing breast cancer and would also serve as a clinically useful prognostic factor in breast cancer patients.  相似文献   
59.
H Hara  H Onodera  H Kato  T Araki  K Kogure 《Brain research》1991,545(1-2):87-96
Changes in second messenger and neurotransmitter system receptor ligand binding induced by transient forebrain ischemia were studied in the gerbil hippocampus. The animals were allowed variable periods of recovery ranging from 2 h to 7 days after 5-min bilateral carotid artery occlusion. The binding of second messenger systems ([3H]inositol 1,4,5-trisphosphate ([3H]IP3)to inositol 1,4,5-triphosphate, [3H]forskolin to adenylate cyclase and [3H]phorbol 12,13-dibutylate to protein kinase C) and neurotransmitter receptor systems ([3H]PN200-110 to L-type calcium channels. [3H]N6-cyclohexyl-adenosine to adenosine A1 and [3H]quinuclidinyl benzilate to muscarinic cholinergic receptor) were assayed using quantitative autoradiography. In the CA1 subfield, 2 h after ischemia, [3H]IP3, [3H]forskolin, and [3H]quinuclidinyl benzilate binding activities significantly decreased by 25, 17 and 13%, respectively, though no morphological abnormalities were obvious. Six hours after ischemia, the [3H]phorbol 12,13-dibutylate binding activity in the stratum oriens of the CA1 subfield increased by 15%. One day after ischemia, [3H]PN200-110 binding activity in this subfield decreased by 26%, and 7 days after ischemia, [3H]phorbol 12,13-dibutylate and [3H]N6-cyclohexyl-adenosine receptor binding activities decreased in this subfield. In particular, at 7 days after ischemia, [3H]IP3 binding activity in the CA1 subfield showed a complete decline. In the CA3 subfield, [3H]PN200-110 binding activity decreased 2 days after ischemia, and [3H]IP3 and [3H]N6-cyclohexyl-adenosine binding activities decreased 7 days after ischemia. In the dentate gyrus, the structure of which remained histologically intact after ischemic insult, [3H]IP3 and [3H]forskolin binding activities decreased 7 days after ischemia. In contrast, the [3H]phorbol 12,13-dibutylate binding activity increased in the molecular layer of the dentate gyrus 7 days after ischemia. These results indicate that marked alteration of intracellular signal transduction precedes neuronal damage in the hippocampal CA1 subfield and that the histologically intact CA3 and dentate gyrus also shows modulated neuronal transmission after ischemia.  相似文献   
60.
The ionic mechanisms of the effect of extracellularly ejected recombinant human tumor necrosis factor-alpha (rhTNF-alpha) on the membrane of identified neurons R9 and R10 of Aplysia kurodai was investigated with conventional voltage-clamp, micropressure ejection, and ion substitution techniques. Micropressure-ejected rhTNF caused a marked hyperpolarization in the unclamped neuron. Clamping the same neuron at it resting potential level (-60 mV) and reejecting rhTNF-alpha with the same dose produced a slow outward current [Io (TNF)] associated with a decrease in input membrane conductance. Io (TNF) was decreased by depolarization and increased by hyperpolarization. The extrapolated reversal potential of Io (TNF) was approximately +10 mV. Ion substitution and pharmacological experiments suggest that Io (TNF) in identified neurons R9 and R10 of A. kurodai is due to a decreased Na+ conductance but not due to an activation of the Na(+)-K+ pump. Our results demonstrate that the immunomodulator TNF can act directly on the nervous system as well as on the immune system.  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