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   3256篇
  免费   164篇
  国内免费   76篇
耳鼻咽喉   12篇
儿科学   196篇
妇产科学   48篇
基础医学   358篇
口腔科学   60篇
临床医学   325篇
内科学   758篇
皮肤病学   81篇
神经病学   212篇
特种医学   423篇
外科学   210篇
综合类   46篇
预防医学   135篇
眼科学   265篇
药学   189篇
  2篇
肿瘤学   176篇
  2023年   12篇
  2022年   17篇
  2021年   35篇
  2020年   35篇
  2019年   37篇
  2018年   45篇
  2017年   47篇
  2016年   39篇
  2015年   54篇
  2014年   71篇
  2013年   97篇
  2012年   96篇
  2011年   109篇
  2010年   128篇
  2009年   124篇
  2008年   96篇
  2007年   139篇
  2006年   106篇
  2005年   111篇
  2004年   78篇
  2003年   73篇
  2002年   86篇
  2001年   109篇
  2000年   85篇
  1999年   84篇
  1998年   142篇
  1997年   163篇
  1996年   143篇
  1995年   118篇
  1994年   123篇
  1993年   102篇
  1992年   52篇
  1991年   49篇
  1990年   56篇
  1989年   69篇
  1988年   65篇
  1987年   55篇
  1986年   69篇
  1985年   62篇
  1984年   37篇
  1983年   30篇
  1982年   27篇
  1981年   34篇
  1980年   29篇
  1979年   14篇
  1978年   20篇
  1977年   24篇
  1976年   37篇
  1975年   20篇
  1974年   9篇
排序方式: 共有3496条查询结果,搜索用时 15 毫秒
91.
INTRODUCTION: There is no consensus for the treatment of severe recurrent uveitis. Immunosuppressive drugs have inconstant efficiency and may result in serious adverse effects. We report the cases of two brothers suffering from severe recurrent idiopathic panuveitis dramatically improved following alpha interferon therapy. EXEGESIS: Two 28 and 32 years old brothers presented with an idiopathic recurrent panuveitis for 4 and 5 years respectively. They both had a HLA B5 haplotype. However they had no clinical symptoms of Beh?et's disease. In both cases panuveitis recurred three or four times yearly despite corticosteroid and cyclosporin therapies. The treatment with alpha interferon improved visual acuity in both cases. The older brother had no recurrence throughout the period of treatment and after a 1 year follow-up. The other one was improved and the ocular lesions have been stabilised for nine months follow-up. CONCLUSION: - Alpha interferon therapy seems efficient in severe idiopathic panuveitis. This treatment is well tolerated without ophthalmologic adverse effects. The optimal posology and the duration of treatment need to be determined.  相似文献   
92.
The B-lymphocyte/accessory-cell activation antigen B7 (BB1) has been shown in vitro to stimulate T-lymphocyte proliferation and cytokine production via CD28 present on the latter cells. In this study, benign lymphoid tissues, lymphomas, and extralymphoid inflammatory sites were examined immunohistochemically using anti-B7 and other relevant monoclonal antibodies. B7 was expressed by benign transformed germinal center B cells, as it was by B cells of follicular lymphomas. B7 was also expressed by a subpopulation (a mean of 31% to 65%) of macrophages and dendritic cells in a variety of lymphoid tissues. It was present in abundance on all macrophages constituting sarcoid granulomas in lymph nodes. In extralymphoid inflammation, 17% to 35% of macrophages expressed B7 only weakly. Cases of Hodgkin's disease showed expression of B7 by the majority of Reed-Sternberg cells or malignant mononuclear variants, a phenomenon that potentially contributes to the lymphocytic accumulation that is a feature of this condition. CD28+ T cells were seen in all areas where T cells were present. B7+ and CD28+ cells colocalized in, for example, lymphoid follicles, lymph node paracortex, sarcoid granulomas, and Hodgkin's disease tissue, indicating a potential for cellular interaction via these molecules at these sites.  相似文献   
93.
After bone marrow transplantation (BMT), a prolonged dysregulation of humoral immunity can be observed. In the present study, we investigated whether this is reflected in an abnormal production of specific antibodies (Ab) to the T-cell-dependent recall antigen tetanus-toxoid (TT). The study group consisted of children receiving transplants of an unmodified allogeneic graft and of adults receiving either a T-cell- depleted allogeneic or an unmodified autologous BM graft. Findings were compared with those in healthy controls. In pediatric graft recipients, who were routinely revaccinated early after BMT, the Ab response was quantitatively superior to that in adult graft recipients who did not receive early revaccination. In the majority of graft recipients, the time period after vaccination required to reach the peak level of antibodies was prolonged and the number of responding TT-specific B- cell clones was markedly decreased in comparison with controls. In controls, a low frequency of dominant B-cell clones may produce low quantities of homogeneous Ab components (H-Ab) against a heterogeneous background. However, in BM graft recipients, "overshooting" of Ab production by separate B-cell clones was observed, resulting in the development of H-Ab at a relatively high concentration. These abnormalities were present up to 10 years after BMT, irrespective of either the age of the recipient, the modulation of the graft, or the vaccination schedule used. It is hypothesized that the dysregulated Ab production is the consequence of activation of a restricted number of resting memory B cells, present in germinal centers, repopulating gradually after BMT. Our data show that routine revaccination early after BMT improves the humoral immune response. However, because of a clonally dysregulated Ab production, long-lasting qualitative defects may be present even after normalization of Ab titers.  相似文献   
94.
Naccache  PH; Jean  N; Liao  NW; Bator  JM; McColl  SR; Kubes  P 《Blood》1994,84(2):616-624
The control of the adhesive properties of human neutrophils is an essential element of their defense function. One level at which this control is exerted involves the upregulation of the surface expression of beta 2-integrins. In this study, we have examined the potential involvement of tyrosine phosphorylation in the latter process. Two inhibitors of tyrosine kinases with differing modes of action, erbstatin and herbimycin A, were found to inhibit the expression of CD11b and CD18 stimulated by chemotactic factors (fMet-Leu-Phe or leukotriene B4) or growth factors (tumor necrosis factor alpha). This inhibition was not shared by an inactive analog of erbstatin or by the protein kinase C inhibitor Ro 31-8330. Erbstatin also inhibited the unveiling of activation-specific neoepitopes detected by antibody CBRM1/5. Pretreatment of neutrophils (but not of endothelial cells) with erbstatin inhibited the stimulation of neutrophils' adherence to endothelial cells induced by fMet-Leu-Phe. Augmentation of tyrosine phosphorylation by inhibiting tyrosine phosphatases using hydroperoxyvanadate led to an increased surface expression of CD11b and CD18 and enhanced the adhesion of neutrophils to endothelial cells. Finally, the leumedin NPC 15669, which had previously been shown to inhibit stimulated CD11b expression and neutrophil adherence to endothelial cells and to exhibit anti-inflammatory properties in various in vivo models of inflammation, inhibited the stimulation of tyrosine, phosphorylation induced by fMet-Leu-Phe. Taken together, these data establish a strong correlation between tyrosine phosphorylation and integrin upregulation in stimulated human neutrophils.  相似文献   
95.
Assessing the delivery of neutrophils to tissues in neutropenia   总被引:2,自引:2,他引:2  
Wright  DG; Meierovics  AI; Foxley  JM 《Blood》1986,67(4):1023-1030
Studies of neutrophil kinetics in neutropenic individuals, as well as clinical observations of variability in the occurrence of infection among patients with neutropenia, have suggested that blood neutrophil counts may not uniformly reflect the effective delivery of neutrophils to extravascular tissues where the cells perform their principal host defense functions. To evaluate this possibility we developed a sensitive, reproducible method of measuring the extravascular delivery of neutrophils to a normal mucosal site of neutrophil turnover. This method is based upon the quantification of neutrophils recoverable from saline mouth wash specimens. Twenty-five mL specimens, obtained in a controlled manner from neutropenic patients and normal subjects, were centrifuged and the sediments resuspended in 1.0 mL Hank's buffer with 2 micrograms acridine orange, incubated at 37 degrees C for 15 minutes, and then examined in a hemocytometer chamber by fluorescence microscopy. Neutrophils could be clearly distinguished by their characteristic fluorescence and were counted. With this method as few as 1,500 neutrophils were detected reliably in mouth wash specimens. Mucosal neutrophil counts varied less than 10% with repeated sampling of individual subjects over 5-day periods and were consistently greater than 1.3 X 10(5)/specimen in non-neutropenic individuals. Although profound neutropenia was generally reflected by lower than normal oral mucosal neutrophil counts, these counts were significantly higher in individuals with chronic severe neutropenia (blood neutrophils less than 300/mm3) than in patients with acute neutropenia of comparable severity that had developed following chemotherapy. Also, in individuals recovering from profound neutropenia, neutrophils usually reappeared earlier in mouth wash specimens than in blood, and oral mucosal neutrophil counts attained recovery levels more rapidly than did blood counts. This phenomenon was particularly evident in an individual with cyclic neutropenia. Moreover, mucosal neutrophils could occasionally be detected in profoundly neutropenic patients when neutrophils were not present in blood samples. These findings indicate that mucosal neutrophil counts in individuals with neutropenia provide information about the delivery of neutrophils to tissues that may not be apparent from blood neutrophil counts alone.  相似文献   
96.
97.
MATERIALS AND METHODS: Thirty-one patients underwent stent placement between June 1998 and October 2006 for superior vena cava obstruction. The initial effectiveness of the metallic stent therapy and the follow-up results were studied at one, six and 12 months. PURPOSE: We retrospectively studied the utility of metallic stent placement for the treatment of malignant superior vena cava obstruction in 31 patients (SVCO) on the basis of long-term follow-up data. RESULTS: The initial clinical success rate was 100% (31 out of 31), the primary clinical patency rate was 93% (26 out of 28) at six months. The obstruction rate of the stent was 7% (two out of 28) at six months. There was no additional stent used for recurrence. At 12 months, 27 out of 31 patients were deceased in whom there was no recurrence of SVCO until death. CONCLUSION: Stent therapy is an effective treatment for SVCO. Adjuvant therapy must to be evaluated in association with stent therapy.  相似文献   
98.
99.
Melatonin is synthesized during the night by the pineal gland. Recently, melatonin binding sites have been identified in the gut. Despite few studies, the physiological role of melatonin in gut function remains unclear. The objective of the present study was to investigate the effects of melatonin in the regulation of intestinal motility by using the melatonin receptor antagonist S 22153 in rats. Twenty-four male Wistar rats (400 +/- 25 g) were equipped with intraparietal electrodes along the small intestine. Rats were subjected to a 12:12 hr light:dark schedule. During the dark phase, intestinal migrating motor complexes (MMCs) frequency increased (P < 0.05) by 20% in the duodenum and in the jejunum compared with daylight. This effect is due to a significant reduction in the irregular spiking activity (ISA) of MMCs. Concurrently, at night, the duration of the postprandial motor response is reduced by 30% in the duodenum and 50% in the jejunum and ileum. The administration of S 22153 (2 mg/kg sc) at night suppressed these nocturnal variations and restored the daylight values. In contrast, S 22153 was ineffective during daylight whatever the digestive state. Administration of melatonin (1 mg/kg iv) during the preprandial state, 3 hr after light onset, decreased (-80%) the duration of the ISA of MMCs at the three intestinal levels. During the satiety phase, melatonin administered 10 min before or 15 min after food onset induced the appearance of a transitory preprandial-like motor profile in the entire small intestine. In contrast, when administered at the end of the meal it was ineffective. Preprandial and postprandial melatonin effects were prevented by S 22153 pretreatment. In conclusion, these findings reveal, first, that endogenous melatonin is physiologically involved in the pre- and postprandial changes of intestinal motility at night. Second, exogenous melatonin produces pharmacological effects on pre- and postprandial intestinal motility. In both cases, the action of melatonin corresponds to an inhibition of ISA and a reinforcement of the cyclic MMC pattern.  相似文献   
100.
European Journal of Clinical Microbiology & Infectious Diseases - Molecular diagnosis on nasopharyngeal swabs (NPS) is the current standard for COVID-19 diagnosis, but saliva may be an...  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