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   10986篇
  免费   698篇
  国内免费   52篇
耳鼻咽喉   302篇
儿科学   273篇
妇产科学   299篇
基础医学   1554篇
口腔科学   419篇
临床医学   906篇
内科学   2566篇
皮肤病学   201篇
神经病学   1247篇
特种医学   221篇
外科学   1002篇
综合类   21篇
一般理论   5篇
预防医学   642篇
眼科学   132篇
药学   690篇
中国医学   36篇
肿瘤学   1220篇
  2024年   12篇
  2023年   109篇
  2022年   268篇
  2021年   420篇
  2020年   267篇
  2019年   316篇
  2018年   349篇
  2017年   288篇
  2016年   348篇
  2015年   369篇
  2014年   494篇
  2013年   602篇
  2012年   924篇
  2011年   1036篇
  2010年   513篇
  2009年   449篇
  2008年   784篇
  2007年   713篇
  2006年   640篇
  2005年   666篇
  2004年   599篇
  2003年   545篇
  2002年   478篇
  2001年   55篇
  2000年   33篇
  1999年   50篇
  1998年   86篇
  1997年   59篇
  1996年   43篇
  1995年   46篇
  1994年   33篇
  1993年   33篇
  1992年   20篇
  1991年   10篇
  1990年   7篇
  1989年   13篇
  1988年   8篇
  1987年   2篇
  1986年   13篇
  1985年   3篇
  1984年   5篇
  1983年   4篇
  1982年   5篇
  1980年   4篇
  1979年   2篇
  1978年   2篇
  1976年   3篇
  1974年   2篇
  1973年   2篇
  1968年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Transplant renal artery stenosis (TRAS) is a common vascular complication after kidney transplantation, leading to worsening or refractory hypertension, deterioration in renal function, and possible cause of graft loss. Early diagnosis and an appropriate treatment are crucial for organ preservation. Endovascular treatment, including percutaneous transluminal angioplasty and stent implantation, is considered the first-line therapy for TRAS. Here we report the case of a 69-year-old woman with end-stage renal disease for chronic kidney disease not biopsy proven, who underwent a kidney transplant from expanded criteria donors on December 2018. Postoperative course was characterized by delayed graft function. Doppler ultrasonography (US) showed an increase of peak systolic velocity at the origin of the renal artery, and parvus-tardus waveform in periferic graft arteries and an abdominal computed tomography scan confirmed a stenosis at the origin of the main renal artery (TRAS). The patient underwent a percutaneous transluminal angioplasty. It was not possible to place a stent at the particular location of the stenosis at the anastomosis. Despite the improvement of the graft's perfusion, monitored with Doppler US, the patient showed a very poor improvement in renal function and remained on hemodialysis for months. A percutaneous needle biopsy reported a normal renal parenchyma and excluded acute rejection. During this period, the patient received immunosuppressive therapy. About 6 months after the transplant, the patient had an unexpected and slow renal function recovery until she was weaned completely from hemodialysis.  相似文献   
82.
83.
BackgroundBariatric surgery is associated with an increased risk of delivering a small neonate. The role of maternal weight loss and surgery to conception interval is unclear.ObjectivesTo investigate the effect of maternal weight loss, as a result of bariatric surgery, and surgery to conception interval on fetal growth and birthweight (BW).SettingInner London Teaching HospitalMethodsWe studied prospectively nulliparous women with previous bariatric surgery. Information on type, time, and presurgery weight was obtained. Surgery-to-conception interval was calculated as the time between surgery and conception, defined as the fourteenth day of the pregnancy dated by first trimester ultrasound scan. In the first trimester, maternal weight was measured. Assessment of maternal weight change between presurgery and first trimester of pregnancy was defined as total weight loss (TWL) (%). Fetal ultrasound scans were performed twice; 30–32 and 35–37 weeks’ gestation and estimated fetal weight (EFW) was calculated. Fetal growth rate was calculated as the ratio of EFW increase (in grams) between 30–32 and 35–37 weeks divided by the time interval (in days) between the 2 examinations. BW was recorded.ResultsThe study included 54 pregnant women, 26 with a restrictive procedure (gastric band or vertical sleeve gastrectomy) and 28 with a gastric bypass. Surgery to conception interval was not a significant predictor of the offspring’s growth. Maternal TWL was a significant predictor of fetal growth rate (P = .04) and predictor of BW (P = .005), even after adjustment for confounders.ConclusionsMaternal weight loss, as a result of bariatric surgery, has an inverse correlation with fetal growth rate and BW.  相似文献   
84.
The tumor immune microenvironment of oral tongue squamous cell carcinoma may be accountable for differences in clinical behavior, particularly between different age groups. We performed RNA expression profiling and evaluated tumor infiltrating lymphocytes (TILs) and their T-cell subsets in order to assess the functional status of oral tongue squamous cell carcinoma tumor microenvironment and detect potentially clinically useful associations. Archival surgical pathology material from sixteen oral tongue squamous cell carcinoma patients was microscopically evaluated for TIL densities. RNA was extracted from macrodissected whole tumor sections and normal controls and RNA expression profiling was performed by the NanoString PanCancer IO 360 Gene Expression Panel. Immunostains for CD4, CD8 and FOXP3 were evaluated manually and by digital image analysis. Oral tongue squamous cell carcinomas had increased TIL densities, numerically dominated by CD4 + T cells, followed by CD8 + and FOXP3 + T cells. RNA expression profiling of tumors versus normal controls showed tumor signature upregulation in inhibitory immune signaling (CTLA4, TIGIT and PD-L2), followed by inhibitory tumor mechanisms (IDO1, TGF-β, B7-H3 and PD-L1). Patients older than 44 years showed a tumor microenvironment with increased Tregs and CTLA4 expression. Immunohistochemically assessed CD8% correlated well with molecular signatures related to CD8 + cytotoxic T-cell functions. FOXP3% correlated significantly with CTLA4 upregulation. CTLA4 molecular signature could be predicted by FOXP3% assessed by immunohistochemistry (R2 = 0.619, p = 0.026). Oral tongue squamous cell carcinoma hosts a complex inhibitory immune microenvironment, partially reflected in immunohistochemically quantified CD8 + and FOXP3 + T-cell subsets. Immunohistochemistry can be a useful screening tool for detecting tumors with upregulated expression of the targetable molecule CTLA4.Electronic supplementary materialThe online version of this article (10.1007/s12105-020-01229-w) contains supplementary material, which is available to authorized users.  相似文献   
85.
86.
Summary The glutamatergic mossy fibre granule cell pathway has been investigated in rat cerebellar slices. Exposure to 35 mM KCI, a concentration of K+ known to elicit Ca2+-dependent releases of excitatory amino acids from cerebellar slices, raised cGMP levels. The cGMP response was decreased in a concentration-dependent manner by D-(–)-2-amino-5-phosphonopentanoic acid (D-AP5) and by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) indicating the involvement of ionotropic glutamate receptors of both the N-methyl-D-aspartate (NMDA) and the non-NMDA type. The K+-evoked production of cGMP was potently inhibited (EC50 = 1.21 nM) by 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), a selective 5-HT2 receptor agonist. The effect of DOI (0.01 M) was antagonized by 0.03 M of the 5-HT2 receptor antagonists ketanserin and methiothepin. At concentrations higher than 0.1 M, both antagonists increased on their own the cGMP response elicited by high-K+. This effect was insensitive to tetrodotoxin.It had been previously shown that rat mossy fibre endings release glutamate upon depolarization and that such release can be inhibited by activation of 5-HT2 receptors sited on the mossy fibre endings. Altogether the available data suggest the following conclusions: (a) the glutamate/aspartate endogenously released in cerebellar slices during K+ depolarization increase cGMP synthesis through the activation of both NMDA and non-NMDA receptors; (b) a portion of the cGMP response can be prevented by 5-HT2 receptor activation and may reflect the activity of the mossy fibre-granule cell pathway. Thus serotonin is likely to exert a potent inhibitory control of the excitatory mossy fibre input to the cerebellum by acting at receptors of the 5-HT2 type. Correspondence to M. Raiteri at the above address  相似文献   
87.
88.
89.
The ability of lonidamine (LND), an energolytic derivativeof indazole-carboxylic acid, to modulate the cytotoxic activityof cisplatin (CDDP) and epidoxorubicin (EPI), singly orin combination, was investigated in two human breastcancer cell lines (MCF7 and T47D). A 72-hrpost-incubation with a non-cytotoxic concentration of LND (75M) increased the activity of a 1-hr CDDPtreatment as well as that of a 1to 16-hr EPI treatment. A different pattern ofinteraction among the drugs and modulator was observedas a function of the sequence of drugtreatment. Specifically, supra-additive or additive effects of thecombination were obtained in the two cell linesaccording to the different treatment schemes. In particular,the maximum potentiation was observed in MCF7 cellssimultaneously exposed to CDDP, EPI and LND for1 hr and then post-incubated with LND for72 hr, and in T47 first exposed toEPI and LND, then to CDDP and LND,and finally post-incubated with LND. Flow cytometric analysisof MCF7 cell distribution in the different cyclephases showed that combined treatment with EPI/CDDP/LND wasable to stabilize cell cycle perturbations (mainly G2Maccumulation) induced by individual agents. The ability ofLND to potentiate CDDP and EPI cytotoxicity, andthe consideration that LND causes side effects differentfrom those caused by alkylating agents and anthracyclines,make this compound an attractive candidate for multidrugcombination therapy in breast cancer.  相似文献   
90.
Several patients with the Silver-Russell syndrome (SRS) attending our Genetics Clinic were diagnosed as having persistent metabolic acidosis. Since this abnormality has not been reported previously in the SRS, we reexamined 33 SRS patients to evaluate the frequency and type of metabolic acidosis, the clinical and laboratory findings, and the growth pattern in SRS patients with and without metabolic acidosis. Among them, 14 had a consistent decrease in HCO levels. Renal studies in acidotic patients showed urine pH of 5.8 and 24 h urine calcium of <2.4 mg/kg/24 h; serum creatinine, excretion of glucose, and aminoacids were normal, as were renal ultrasound and excretory urography findings. These data supported the diagnosis of renal tubular acidosis, probably type II; the patients were treated with oral bicarbonate and acidosis was corrected successfully. Clinical manifestations were similar in acidotic and non-acidotic patients. The nutritional indices at diagnosis and at last evaluation (at least 8 months after diagnosis) were abnormally low in all patients; however, acidotic patients, treated with bicarbonate, showed an improvement of nutritional status particularly in the weight/height index, although the difference between groups after follow-up did not reach statistical significance. We suggest that metabolic acidosis due to renal tubular acidosis, probably type II, may occur in children with the SRS and should be looked for and treated in all patients. © 1995 Wiley-Liss, Inc.  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