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   50885篇
  免费   2994篇
  国内免费   246篇
耳鼻咽喉   631篇
儿科学   1170篇
妇产科学   1219篇
基础医学   7057篇
口腔科学   1499篇
临床医学   5572篇
内科学   10970篇
皮肤病学   797篇
神经病学   5010篇
特种医学   1761篇
外科学   6306篇
综合类   325篇
一般理论   44篇
预防医学   3619篇
眼科学   805篇
药学   3449篇
  1篇
中国医学   59篇
肿瘤学   3831篇
  2023年   321篇
  2022年   631篇
  2021年   1143篇
  2020年   745篇
  2019年   979篇
  2018年   1194篇
  2017年   1069篇
  2016年   1254篇
  2015年   1309篇
  2014年   1738篇
  2013年   2506篇
  2012年   3789篇
  2011年   3979篇
  2010年   2366篇
  2009年   2155篇
  2008年   3288篇
  2007年   3590篇
  2006年   3203篇
  2005年   3260篇
  2004年   3002篇
  2003年   2796篇
  2002年   2565篇
  2001年   428篇
  2000年   349篇
  1999年   480篇
  1998年   561篇
  1997年   459篇
  1996年   407篇
  1995年   346篇
  1994年   304篇
  1993年   308篇
  1992年   236篇
  1991年   230篇
  1990年   209篇
  1989年   222篇
  1988年   195篇
  1987年   171篇
  1986年   177篇
  1985年   211篇
  1984年   181篇
  1983年   166篇
  1982年   192篇
  1981年   159篇
  1980年   139篇
  1979年   112篇
  1978年   122篇
  1977年   131篇
  1976年   94篇
  1975年   107篇
  1974年   82篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Summary A patient is described with a testicular Non-Hodgkin's Lymphoma (NHL) presenting with panhypopituitarism caused by a hypophyseal localization. A67Gallium scintigraphy showed avid uptake in the hypophyseal region. Obviously67Gallium could reach the tumor, by the intravenous route, which was the reason to treat the patient with intravenous chemotherapy. A complete remission was induced, which seems to be lasting (+ 25 months). As far as we know this is the first report of panhypopituitarism caused by a hypophyseal NHL in the hypophysis and successfully treated by intravenous chemotherapy.  相似文献   
42.
Anionic polymerization of ?-caprolactam was initiated with the potassium salt of ?-caprolactam and accelerated with phenyl isocyanate, toluylene diisocyanate, 4,4′-diphenylmethane diisocyanate, some derivatives of these isocyanates (urethanes, ureas, and allophanates), or combinations of phenyl isocyanate with its derivatives at 150°C. The effect of individual structures on the polymerization kinetics and their contribution to the preparation of block copolymers of ?-caprolactam with hydroxy-terminated prepolymers, in-situ functionalized with diisocyanates, are discussed on the basis of a detailed analysis of time functions of polymer yield and degree of polymerization.  相似文献   
43.
Mice homozygous for the lpr mutation have B and T cell defects and develop autoantibodies, suggesting that lpr plays a role in their genesis. The lpr defect has been identified as a mutation in the apoptosis-associated Fas receptor (FasR) gene. To begin to define the role of FasR in B cells, we have surveyed FasR expression on B-lineage cells from early progenitors in the bone marrow through their maturation in the periphery. Contrary to some reports, we found that FasR is expressed on B cells at all stages of their development and is highest on germinal center B cells. FasR is not expressed on lpr/lpr-derived cells. These data are consistent with the idea that lpr/lpr mice have an intrinsic B cell defect that may be manifested in developing as well as peripheral B cells. An unexpected finding is that B-1 (CD5) B cells do not constitutively express FasR: FasR becomes detectable on B-1 B cells only after activation.  相似文献   
44.
45.
To examine the incidence of interstitial and vascular rejection in pancreas allografts and its impact on graft survival, we studied 36 percutaneous pancreas biopsies and 10 pancreas transplantectomy specimens from 32 patients who had undergone simultaneous pancreas-kidney transplantation. Interstitial rejection (IR) was predominantly found in the biopsies, while vascular rejection (VR) was most prominent in the transplantectomies. Pancreas graft survival was significantly decreased for pancreas grafts that had suffered from vascular rejection when compared to those with only interstitial rejection. Potential rejection markers, i. e., serum amylase, glucose, creatinine, and urinary amylase, did not correlate with histological signs of rejection, although increased levels of serum amylase were, in all but one case, associated with rejection.We conclude that a percutaneous pancreas biopsy remains the most reliable method to determine pancreas rejection, and that by distinguishing between IR andVR, a pancreas biopsy may provide important diagnostic as well as prognostic information. Received: 6 March 1997 Received after revision: 5 June 1997 Accepted: 30 June 1997  相似文献   
46.
A cross-sectional survey on respiratory health in swine producers showed that 30% of 301 examined men usually used a dust mask when working inside a barn. They did not differ significantly from dust mask nonusers in respect to respiratory symptoms and lung function. This analysis was undertaken to determine whether the respiratory health of dust mask users was associated with reasons why they had started individual respiratory protection. The subjects were recontacted in order to identify those who started using a mask to deliberately prevent symptoms (42 men) and those who started protection because of pre-existing respiratory symptoms (44 men). Not unexpectedly, betweengroup comparisons of respiratory symptoms and lung function suggest that swine producers who wear dust masks for preventive purposes have better respiratory health than those who wear dust masks because of symptoms or those who do not use individual respiratory protection. The individual reasons for starting dust mask usage should be examined among potential determinants of the outcomes of prospective studies which can then provide more valid assessment of the effect of individual respiratory protection. © 1993 Wiley-Liss, Inc.  相似文献   
47.
48.
Axonal pathology is a major cause of neurological disability in multiple sclerosis. Axonal transection begins at disease onset but remains clinically silent because of compensatory brain mechanisms. Noninvasive surrogate markers for axonal injury are therefore essential to monitor cumulative disease burden in vivo. The neuronal compound N-acetylaspartate, as measured by magnetic resonance spectroscopy, is currently the best and most specific noninvasive marker of axonal pathology in multiple sclerosis. The possibility has been raised, however, that N-acetylaspartate is expressed also by oligodendroglial lineage cells. In order to investigate N-acetylaspartate specificity for white matter axons, transected rat optic nerves were analyzed by high-performance liquid chromatography and immunohistochemistry. In transected adult nerves, N-acetylaspartate and N-acetyl aspartylglutamate decreased in concordance with axonal degeneration and were undetectable 24 days posttransection. Nonproliferating oligodendrocyte progenitor cells, oligodendrocytes, and myelin were abundant in these axon-free nerves. At 24 days posttransection, N-acetylaspartate was increased (42%; p = 0.02) in nontransected contralateral nerves. After transection at postnatal day 4, total N-acetylaspartate decreased by 80% (P14; p = 0.002) and 94% (P20; p = 0.003). In these developing axon-free nerves, 25 to 33% of oligodendrocyte progenitor cells were proliferating. These data validate magnetic resonance spectroscopy measurements of N-acetylaspartate as an axon-specific monitor of central nervous system white matter in vivo. In addition, the results indicate that neuronal adaptation can increase N-acetylaspartate levels, and that 5 to 20% of the N-acetylaspartate in developing white matter is synthesized by proliferating oligodendrocyte progenitor cells.  相似文献   
49.
Background: Half of the patients who undergo surgery for cancer of the esophagus or gastric cardia present with recurrent disease within 2 years after the operation. We investigated the value of endosonography for the early detection of recurrent disease. Methods: Forty-three patients entered a follow-up protocol in which endosonography was performed every 6 months within the first 2 years after resection. Results: During 16 of a total of 66 examinations, suspicious abnormalities were found. In three patients free fluid was seen, but recurrence could not be confirmed during follow-up. In eight patients suspicious lymph nodes were seen; six died within 6 months, one was alive with a proven recurrence at 6 months, and one was alive without recurrence at 22 months. In five patients focal wall-thickening or a mass was seen; three died within 6 months, and two were alive with a proven recurrence at 2 and 5 months. After exclusion of free fluid, the positive predictive value of abnormalities on endoscopic ultrasonography (EUS) was 92%. Conclusions: Endosonography, performed at 6-month intervals after resection of cancer of the esophagus or gastric cardia, is accurate in the early detection of locoregional recurrent disease. Two thirds of the patients were still without symptoms when the recurrence was found. (Gastrointest Endosc 1997;46:487-91.)  相似文献   
50.
Hydrocephalus and cavernoma of the cauda equina   总被引:1,自引:0,他引:1  
F Ramos  B de Toffol  B Aesch  M Jan 《Neurosurgery》1990,27(1):139-142
The association of a tumor of the cauda equina and hydrocephalus is unusual. We report a case of hydrocephalus with normal pressure associated with an equally rare affliction, a cavernous angioma of the cauda equina, which regressed after surgical ablation. The physiological mechanism involved is discussed.  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