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   5316篇
  免费   256篇
  国内免费   15篇
耳鼻咽喉   47篇
儿科学   145篇
妇产科学   53篇
基础医学   603篇
口腔科学   161篇
临床医学   380篇
内科学   1255篇
皮肤病学   55篇
神经病学   368篇
特种医学   201篇
外科学   915篇
综合类   20篇
预防医学   302篇
眼科学   66篇
药学   537篇
中国医学   9篇
肿瘤学   470篇
  2023年   34篇
  2022年   64篇
  2021年   105篇
  2020年   50篇
  2019年   67篇
  2018年   84篇
  2017年   87篇
  2016年   86篇
  2015年   78篇
  2014年   114篇
  2013年   162篇
  2012年   223篇
  2011年   275篇
  2010年   136篇
  2009年   88篇
  2008年   192篇
  2007年   231篇
  2006年   204篇
  2005年   238篇
  2004年   217篇
  2003年   196篇
  2002年   207篇
  2001年   203篇
  2000年   190篇
  1999年   185篇
  1998年   62篇
  1997年   56篇
  1996年   56篇
  1995年   47篇
  1994年   54篇
  1993年   54篇
  1992年   171篇
  1991年   166篇
  1990年   140篇
  1989年   128篇
  1988年   119篇
  1987年   104篇
  1986年   111篇
  1985年   110篇
  1984年   60篇
  1983年   59篇
  1982年   30篇
  1981年   28篇
  1980年   23篇
  1979年   44篇
  1975年   23篇
  1974年   27篇
  1971年   21篇
  1969年   20篇
  1968年   20篇
排序方式: 共有5587条查询结果,搜索用时 15 毫秒
91.
Disseminated intravascular coagulation frequently occurs after global ischemia and reperfusion due to cardiac arrest. The present study was performed to demonstrate the role of tissue factor for coagulation pathway activation, as well as to investigate the precise time course of tissue factor pathway inhibitor (TFPI) during and after cardiopulmonary resuscitation (CPR). Thirty-two of out-of-hospital cardiac arrest patients were classified into two groups, those who achieved return of spontaneous circulation (ROSC) (n=13) and those without ROSC (n=19). Ten normal healthy volunteers served as control subjects. Serial levels of tissue factor and TFPI were measured during and after cardiac arrest and CPR. In patients with ROSC, cardiac arrest and CPR led to persistent increases in the levels of tissue factor that peaked 6 hours after arrival at the Emergency Department. Tissue factor levels in patients without ROSC also showed marked elevations compared to those of the control subjects. In both groups, the levels of TFPI were significantly lower than those in the control subjects. However, we could not find differences in the levels of the two markers between the patients with ROSC and those without ROSC. In conclusion, we demonstrated persistent elevation of the tissue factor levels associated with low TFPI during and after CPR in patients with out-of-hospital cardiac arrest. These results indicate the activation of the extrinsic coagulation pathway without adequate TFPI generation, which may contribute to thrombin activation and fibrin formation after whole-body ischemia and reperfusion.  相似文献   
92.
93.
A case of fibrous dysplasia of the frontal bone in a 51 year-old male is described. He was admitted to our hospital with a hard, painless growing mass in the left frontal region. A symmetrical protrusion of his forehead has been observed since several years before. Neurological examination and laboratory data revealed no abnormalities. Skull x-rays demonstrated two different lesions. One showed a ground glass appearance in the supraorbital region, and the other showed a radiolucent lesion with marginal sclerosis crossing the left coronal suture CT scan revealed an intradiploic multilocular mass. T1 and T2 MR images showed an abnormal low-intensity mass, and heterogeneous gadolinium-enhancement was noticed in both lesions. Selective external carotid angiography showed tumor stain in the left coronal mass fed by middle meningeal and superficial temporal arteries mimicking intraosseous meningioma. On the other hand, a supraorbital hyperostotic lesion showed no apparent vascularity. An operation was performed on the left coronal lesion to verify the nature of the progressively enlarging mass, which was histologically confirmed to be a fibrous dysplasia rich in numerous vessels. Postoperative course was uneventful. Correlation with clinical activity and enhancement pattern was not known, however, careful observation is required in hypervascular fibrous dysplasia such as was observed in this case.  相似文献   
94.
In the early progression of atherosclerosis, LDL migrates in the subendothelial space of the artery and plays an important role in foam cell formations of macrophages. LDL may serve as a carrier of site-specific delivery of drugs to atherosclerotic lesions. In this exploratory study, dexamethasone palmitate (DP) was incorporated in LDL, and an inhibitory effect of this complex on foam cell formations was examined. LDL was isolated from human plasma, and the DP-LDL complex was prepared by incubation in the presence of Celite 545. No degradation nor modification of LDL was observed. The DP/LDL molar ratio of the complex was 35-50:1. Foam cell formations of murine macrophages were induced by incubation with oxidized LDL. When macrophages were pretreated with the DP-LDL complex, accumulation of cholesterol ester in the macrophages induced by oxidized LDL, i.e., an index of foam cell formation, was decreased. These findings indicated that the DP-LDL complex showed similar characteristics to LDL, and the DP-LDL complex inhibited foam cell formations of macrophages in vitro. This study provides the basis for further study of the DP-LDL complex as a drug-carrier complex for treatment of atherosclerosis.  相似文献   
95.
Methylterahydrophthalic anhydride (MTHPA) is used as a hardening agent in an epoxy resin system. Because work-related nasal symptoms were observed in some workers exposed toMTHPA at two condenser plants, a cross-sectional survey was performed to improve their work environment. MeanMTHPA levels in the manufacturing processes to which the workers were routinely assigned were extremely low (1.09-22.4 μg/m3). However, specific IgE antibody (S-IgE) was detected in 9 (32%) of 28 workers. Of these, 8 (89%) had nasal symptoms. An IgE-mediated mechanism seems to be associated with at least some of the cases of work-related nasal symptoms. This indicates that the occupational health administration ofMTHPA cannot be controlled simply by limiting exposure in the work environment. Total IgE (T-IgE) levels were significantly higher in S-IgE-positive workers than in S-IgE-negative workers (geometric mean, 200.5 and 51.3 IU/ml, respectively; p<0.002, unpaired t test). These findings demonstrate that workers in whom S-IgE is less likely to be produced, i.e., those in whom the T-IgE level is 80 IU/ml or less, should be assigned to work in these manufacturing processes.  相似文献   
96.
To determine whether acute mental stress alters the composition of peripheral blood cells or components of the immune system, we determined blood cell counts and leukocyte differential counts, and examined lymphocyte subsets, before, during, and after 10 min. of mental arithmetic in 20 healthy female students. During mental stress the absolute number of leukocytes, lymphocytes, CD8+ cells, and CD16+ cells increased significantly, and the rate of CD8+ cell increase was higher than CD4+ cell increase. Therefore the CD4+/CD8+ ratio decreased significantly during mental stress. Erythrocyte counts, hemoglobin concentrations and packed cell volumes remained unchanged during and after mental stress. These results demonstrate that acute mental stress is associated mainly with rapid peripheral blood lymphocyte changes, including the release of CD8+ and CD 16+ cells into circulation. The absence of significant increases in erythrocyte counts, hemoglobin concentrations, and packed cell volumes during stress indicates that changes in lymphocyte composition cannot be explained by the hemoconcentration. Thus, acute mental stress has a detectable influence on peripheral blood cell counts and the immune system.  相似文献   
97.
Although several studies have been undertaken to evaluate the efficacy of health screening in causing changes in health-related behavior, there are few findings with respect to the efficacy of annually repeated health screening.Using cross-sectional data drawn from a population consisting of white-collar workers in Osaka, Japan, the relation between the results of annually repeated health screening and individual health behavior was examined.Several diseases were related to diet and alcohol consumption, but not to physical exercise habits. High γ-GTP or alcoholic liver damage and hypertension were related to moderate alcohol consumption (p<0.001 and 0.05). A high cholesterol level was related to a nutritionally balanced diet (p<0.05). However, there were no diseases related to increased physical exercise.Findings in the present study, in combination with the literature indicate the possibility that annually repeated health screening intervention has been effective in promoting positive lifestyle changes in diet and alcohol consumption among participants. However, to conclusively evaluate the effucacy of the annually repeated health screening, further study is necessary.  相似文献   
98.
Yield of methanolic extract of fresh roots of Ginseng harvested in winter was found to be more than two-fold grater than from roots collected in summer; this remarkable increase is mainly due to the large increase of sucrose in roots in winter. On the other hand, biologically active dammarane-saponins in the roots increase in summer. These results indicate that roots should be harvested in summer for the production of high quality Ginseng extracts.  相似文献   
99.
AIM: To facilitate the understanding of the transporter function of human renal tubular cells, we have developed a simple method using primary cultured proximal tubule (PT) cells isolated from voided urine. METHODS: PT cells grown to confluence on glass coverslips could be identified by parallel arrays of spindle cells and hemicyst formation. Brush-border gamma-glutamyl transpeptidase (gammaGTP) activity was histochemically identified. Apical membrane Na+/H+ exchanger (NHE) activity was measured by monitoring changes in intracellular pH (pHi) after an acid load in a single cell level using the pH-sensitive dye 2'7'-bis-(2-carboxyethyl)-5.6'carboxyfluorescein (BCECF). RESULTS: Amiloride and 5-(N-ethyl-N-isopropyl) amiloride (EIPA) inhibited the NHE activity with half-maximal inhibition values (IC50) of 15.3 and 4.0 microM, respectively. NHE-3 mRNA was detected by the RT-PCR technique in clonally proliferated PT cells. CONCLUSION: These results suggest that cultured PT cells isolated from human urine express amiloride-resistant NHE-3 activity on the apical membranes, which can be compared to functional properties of PT in vivo. Our experimental strategy offers a useful experimental approach to investigating human renal tubular transport function in vitro.  相似文献   
100.
We report a case of a 70-year-old woman admitted to our hospital with sudden headache, drowsiness and hyponatremia. MRI on admission showed an intrasellar mass with suprasellar extension. Serum examination revealed decreased sodium and hypopituitarism, but they were normalized gradually by compensation using hydrocortisone, thyroid hormone and salt. Afterwards, masked diabetes insipidus appeared and required aqueous pitressin for the control of urine volume. A removal operation was performed uneventfully using the transsphenoidal approach and histological examination confirmed squamous-papillary type craniopharyngioma. Intratumoral hemorrhage of the craniopharyngioma is extremely rare. These cases tend to occur after over 15 years of maturation and the squamous-papillary type tend to bleed more than the adamantinomatous type. However, it is very difficult to make a differential diagnosis between craniopharyngioma with intratumoral hemorrhage and pituitary apoplexy, judging only by symptoms or interventional radiology. The definite mechanism of hyponatremia associated with a parasellar lesion is still obscure, but compression to the anterior hypothalamus or pituitary gland by an enlargement of the parasellar tumor is generally hypothesized.  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