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   300711篇
  免费   12407篇
  国内免费   6599篇
耳鼻咽喉   2341篇
儿科学   8512篇
妇产科学   5896篇
基础医学   29535篇
口腔科学   4199篇
临床医学   28115篇
内科学   50269篇
皮肤病学   2233篇
神经病学   22578篇
特种医学   12985篇
外国民族医学   40篇
外科学   41720篇
综合类   21509篇
现状与发展   20篇
一般理论   18篇
预防医学   27274篇
眼科学   6136篇
药学   22705篇
  114篇
中国医学   7140篇
肿瘤学   26378篇
  2024年   345篇
  2023年   1712篇
  2022年   4012篇
  2021年   5426篇
  2020年   4056篇
  2019年   3676篇
  2018年   25554篇
  2017年   20817篇
  2016年   22555篇
  2015年   6095篇
  2014年   7492篇
  2013年   7654篇
  2012年   16905篇
  2011年   31511篇
  2010年   25979篇
  2009年   17477篇
  2008年   27006篇
  2007年   29114篇
  2006年   7764篇
  2005年   8757篇
  2004年   8103篇
  2003年   8637篇
  2002年   6056篇
  2001年   3340篇
  2000年   3241篇
  1999年   2794篇
  1998年   1500篇
  1997年   1415篇
  1996年   1069篇
  1995年   1043篇
  1994年   976篇
  1993年   558篇
  1992年   922篇
  1991年   882篇
  1990年   788篇
  1989年   642篇
  1988年   575篇
  1987年   487篇
  1986年   378篇
  1985年   312篇
  1984年   202篇
  1983年   187篇
  1982年   118篇
  1981年   93篇
  1980年   106篇
  1979年   142篇
  1978年   119篇
  1977年   86篇
  1974年   113篇
  1972年   87篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
931.
Complications in a donor are a distressing but inevitable occurrence, since graft procurement is a major undertaking. Although the technique for procurement has some similarities to hepatic resection, a donor is very unlike a patient with malignancy. The risk factors identified in these patients cannot be extrapolated to donors. Donor hepatectomy carried out from June 1995 to March 2005 in Chang Gung Memorial Hospital, Kaohsiung Medical Center was reviewed with the aim of identifying risk factors for complications. There were 204 living donor liver transplants, with 205 donor hepatectomies, as 1 living donor liver transplantation was a dual graft. Ten donors (4.88%) suffered complications. There was no difference in terms of age, gender, body weight, operation, and parenchymal time between those who had complications and those who did not. There was also no difference in liver function tests between the 2 groups of donors, but the total bilirubin was significantly higher in donors with complications. The graft weight and remnant liver volume were also similar. The proportion of donors with fatty liver was the same between the 2 groups. The mean blood loss in donors with complications was 170 +/- 79 mL, and that for donors without complications was 95 +/- 77 mL. There was a statistically significant greater blood loss in donors with complications (P < 0.05). The number of segments removed in donors with complications was also higher compared to donors without complications (P < 0.03). Using multivariate analysis, intraoperative blood loss and the number of segments removed were found to be independent risk factors for donor complications. Intraoperative blood loss during graft procurement must be kept low to minimize complications in donors.  相似文献   
932.
Several likely precursors of schizophrenia have been identified. These range from possibly causative features, such as exposure to perinatal insults, to features that are the effects of an underlying vulnerability, such as abnormal childhood behaviors. Unfortunately none of these precursors is specific enough to be used in identifying individuals for targeted preventive treatment. A more useful strategy is to combine risk factors for psychotic disorders in a population seeking help for psychiatric problems. Thus, individuals who are possibly prodromal are identified. Research into this group has found high rates of onset of psychotic disorders, particularly schizophrenia, within a short time frame. Preliminary treatment trials suggest that symptoms can be reduced and psychosis onset possibly delayed or averted.  相似文献   
933.
Magnetic susceptibility, as a physical property of materials, plays important roles in many physical, chemical, engineering, and medical applications. Its quantification becomes of significant interest when MRI becomes a commonly used technique in biomedical applications. A general method is presented here for quantifying arbitrary magnetic susceptibility distributions in a localized region on the basis of first principles of magnetic induction field distributions in space. A proof of the concept was demonstrated by computer simulations. The study establishes the methodological basis for quantitative magnetic susceptibility imaging with MR.  相似文献   
934.
Hemosuccus pancreaticus (HP) is a rare cause of gastrointestinal bleeding, usually due to rupture of a visceral artery aneurysm in chronic pancreatitis. Other causes of HP are rare. We present a case of HP which occurred in a patient with chronic calcifying pancreatitis and a pancreatic pseudocyst documented by ultrasonography and computed tomography. With detectable fresh blood in the descending duodenum, an aneurysm in the pancreatic head was revealed by superior mesenteric angiography as the suspected origin of intermittent bleeding from the pancreatic duct. Because an artery feeding the pseudocyst could not be identified, angiographic embolization was not possible. Surgical resection or ligation was difficult by laparotomy; therefore, intraoperative packing of the pseudocyst with absorbable gelatin sponges was achieved via a cannula through a directly punctured site in the pseudocyst wall. The patient has been followed for 4.25 years with no further episodes of HP. It is possible that the packing of a pancreatic pseudocyst with gelatin sponges is a method that can be used in similar cases, where control of hemostasis is the primary concern. The packing of a pancreatic pseudocyst with gelatin sponges is a technique that can be performed not only via laparotomy but also via laparoscopy or concomitant angiography and ultrasonography.  相似文献   
935.
In this review article, we demonstrate the mucin expression profile in normal tissue, invasive ductal carcinoma (IDC), two subtypes of intraductal papillary–mucinous neoplasm (IPMN dark cell type and IPMN clear cell type), pancreatic intraepithelial neoplasia (PanIN), and mucinous cystic neoplasm (MCN) of the pancreas. In MUC1, there are various glycoforms, such as poorly glycosylated MUC1, sialylated MUC1, and fully glycosylated MUC1. IDCs showed high expression of all the glycoforms of MUC1. IPMNs dark cell type showed no expression or low expression of all the glycoforms of MUC1. IPMNs clear cell type showed low expression of poorly glycosylated MUC1, but expression of sialylated MUC1 and fully glycosylated MUC1. Expression of MUC2 was negative in IDCs, high in IPMNs dark cell type and low in IPMNs clear cell type. MUC5AC was highly expressed in IDCs, IPMNs dark cell type, and IPMNs clear cell type. MUC6 expression was higher in IPMNs clear cell type than in IDCs and IPMNs dark cell type. Our recent study demonstrated that high expression of MUC4 in IDCs is correlated with a poor outcome for patients. In PanINs, expression of both MUC5AC and MUC6 are an early event, whereas up-regulation of MUC1 is a late event. MCNs do not look as if they will show a specific mucin expression profile according to the literature review.  相似文献   
936.
BACKGROUND AND PURPOSE: The potential risk of prolongation of treatment time in cervical cancer has been reported for many low-dose rate (LDR) studies, with an estimated loss of local control ranging from 0.3 to 1.6% per day of treatment prolongation. Since the treatment schedule for fractionated high-dose rate intracavitary brachytherapy (HDRICB) is not directly comparable with that for low-dose rate studies, this report aims to evaluate the adverse effect of treatment prolongation specifically for cervical cancer treated with HDRICB. MATERIAL AND METHODS: From September 1992 to December 1997, 257 patients diagnosed with uterine cervical cancer (35 Ib, 26 IIa, 122 IIb, 10 IIIa, 57 IIIb, 7 IVa), who underwent external radiotherapy combined with between two and four courses of HDRICB and a minimum of 3 years of follow-up (median 57 months), were analyzed. Treatment consisted of irradiation of the whole pelvis with 44-45 Gy consisting of 22-25 fractions by 5 weeks, with the dose boosted to 54-58 Gy (with central shielding) for patients diagnosed as FIGO stage IIb-IVa bilateral parametrial disease. HDRICB was performed using an Ir-192 remote afterloading technique at 1-week intervals. The standard prescribed dose for each course of HDRICB was 7.2 Gy to point A for three insertions (before July 1995), or 6.0 Gy to point A for four insertions (after July 1995). Total prescribed point A doses (external beam radiotherapy+HDRICB) ranged from 58 to 71.6 Gy (median, 65.6 Gy) for stage IB-IIA, while analogous dosage for larger lesions (stage IIb-IVa) ranged from 59 to 75.6 Gy (median, 65.6 Gy). Kaplan-Meier and multivariate analyses were used to test the effect of treatment time on pelvic control rate (PCR) and cause-specific survival (CSS) at 5 years. RESULTS: Median treatment time was 63 days. For all stages of disease, the 5-year CSS and PCR were significantly different comparing treatment times of less than and greater than or equal to 63 days [83% and 65% (P=0.004], 93% and 83% (P=0.02), respectively]. These associations were also significant for stage Ib/IIa [97% and 79% (P=0.01), and 100% and 87% (P=0.02), respectively), but not for stage IIb [75% and 72% (P=0.79), and 93% and 87% (P=0.83), respectively] or stage III [66% and 49% (P=0.2), and 83% and 72% (P=0.21), respectively]. Multivariate analysis identified three prognostic factors for CSS, stage (P<0.001), tumor response to external RT (P=0.001), and overall treatment time (OTT; P=0.006). Prognostic factors for pelvic failure were stage (P<0.001), tumor response to external RT (P=0.001), and OTT (P=0.03). Prolongation of treatment time resulted in a daily decrease in pelvic control rate of 0.67% overall, and 0.43% for stage Ib-IIa, 0.57% for stage IIb, and 0.73% for stage III patients. CONCLUSION: Analysis of the data from the current study demonstrates that the adverse effect of treatment prolongation was observed later in the treatment course for the high-dose rate (HDR) series compared to the LDR analog, however, treatment-time prolongation still negatively influenced the cause-specific survival and pelvic control rate for both dosage groups.  相似文献   
937.
慢传输型便秘模型的建立及其机制探讨   总被引:13,自引:0,他引:13  
目的 :建立实验型慢传输型便秘模型。 方法 :实验组小鼠皮下注射吗啡建立慢传输型便秘模型 ,记录小鼠粪便重量 ,利用炭沫推进试验比较实验组与对照组小鼠结肠传输功能 ;利用免疫组化技术比较两组小鼠结肠组织中Cajal细胞数量。 结果 :实验组小鼠粪便重量减轻 (P <0 .0 1) ,结肠推进率较对照组明显延长 (P <0 .0 1) ,Ca jal细胞数量较对照组明显减少 (P <0 .0 1)。 结论 :吗啡皮下注射诱导小鼠结肠慢传输型便秘模型符合疾病的基本特点 ,其发病机制可能与内源性阿片肽增多和 (或 )肠道Cajal细胞异常改变有关  相似文献   
938.
Genital herpes simplex virus (HSV) infection has substantial economic and quality-of-life consequences; not least is the risk of transmission to the fetus/infant during parturition with the subsequent effects on the family, society as a whole and healthcare providers. While general screening programs for HSV infection are not cost effective, screening of susceptible subgroups may be acceptable in some circumstances (e.g. immunocompromised patients, presumed discordant heterosexual couples, pregnant women) despite the high costs involved. First-line options for treatment and suppression of genital herpes in Europe and the US include valaciclovir, aciclovir and famciclovir. The established efficacy of valaciclovir, along with its potential for once-daily administration in many patients (versus administration up to five times daily for aciclovir), its positive effect on quality of life, its suppressive efficacy in late pregnancy and its proven reduction of viral transmission between heterosexual discordant partners support the drug’s position as a first-line therapy and suppression option in patients with genital herpes. However, the high acquisition costs compared with aciclovir will affect formulary decisions in some patients, and the favored niche for this drug, at least until evidence of prevention of transmission is demonstrated for other antivirale, would seem to be in the prevention of transmission in susceptible subgroups such as couples discordant for HSV infection (especially male-positive/female-negative couples who are planning a pregnancy), and the treatment and suppression of genital herpes in patients particularly receptive to once-daily administration.Potential disease management programs for genital herpes would thus need to balance the high costs of HSV screening and the relatively high acquisition costs of valaciclovir against the convenience of once-daily administration, the improved quality of life and the proven potential for reduced viral transmission to susceptible partners (with potential for downstream reductions in the overall socioeconomic burden of the disease) associated with oral valaciclovir.  相似文献   
939.
OBJECTIVE: To examine the oxidation or reduction products in patients with rheumatism arthritis (RA), and investigate the relationship between oxidation or reduction products and occurrence and development of RA. METHODS: The serum levels of total ascorbic acid (TAA), dehydroascorbic acid (DHAA)/TAA, vitamin E, advanced oxidation protein products (AOPP) and malondialdehyde (MDA) were detected by high-performance liquid chromatography with electrochemical detection in 83 RA patients and 30 healthy adults. Correlation analysis of AOPP, MDA and hs-CRP was performed. RESULTS: Compared with normal control group, significantly higher serum MDA, DHAA/TAA, and AOPP levels were detected in RA patients (P<0.05), but vitamin E showed no significant difference (P<0.05). Linear regression analysis showed that MDA (P<0.01) was positively but AOPP (P>0.05) negatively correlated to hs-CRP. CONCLUSIONS: Oxidation or reduction products in serum of RA patients increases significantly, which may be an important mechanism for the occurrence and development of RA. Serum AOPP and MDA levels can reflect the oxidation status in RA patients.  相似文献   
940.
p21对缺血-再灌注损伤后肾小管上皮细胞演变的影响   总被引:2,自引:0,他引:2  
目的 探讨p21对缺血-再灌注损伤(IRI)后肾小管上皮细胞演变的影响。方法 选择低龄(2个月龄)和高龄(12个月龄)p21(+/+)和p21(-/-)鼠,建立左肾IRI模型。于IRI后0、1、3、7d及1、3、6个月光镜下观察肾小管组织学变化,采用免疫组化法检测肾小管上皮细胞增殖细胞核抗原(PCNA)表达,组织化学染色观察肾小管上皮细胞衰老相关β-半乳糖苷酶(SA-β-gal)活力,末端脱氧核糖转移酶介导的生物素化脱氧尿嘧啶缺刻标记技术(TUNEL)检测肾小管上皮细胞凋亡。结果 IRI后0d,肾小管以坏死为主,高龄鼠比低龄鼠严重、p21(-/-)鼠比p21(+/+)鼠严重(P均〈0.05)。肾小管上皮细胞凋亡在IRI 1d后出现,7d达高峰,且高龄鼠比低龄鼠明显、p21(-/-)鼠比p21(+/+)鼠明显(P均d0.05)。低龄鼠IRI后1个月出现SA—β-gal染色阳性的肾小管上皮细胞,而对侧肾此时未见衰老细胞,3和6个月时衰老的肾小管上皮细胞显著增多,且p21(+/+)鼠比p21(-/-)鼠明显(P〈0.05);p21(+/+)高龄鼠IRI后0d双肾即可见大量的SA-β-gal染色阳性肾小管上皮细胞,且较p21(-/-)鼠显著增多(P〈O.05),但1d后,p21(+/+)和p21(-/-)鼠IRI肾衰老细胞均明显减少(P均〈0.05),1个月后又呈进行性增加,且p21(+/+)鼠始终比p21(-/-)鼠严重。高龄和低龄p21(+/+)鼠PCNA阳性染色细胞出现的几率差异无显著性(P〉0.05),但低龄鼠细胞增殖能力要强于高龄鼠;而p21(-/-)鼠的细胞增殖能力明显强于p21(+/+)鼠,低龄鼠更为显著(P均〈0.05)。对高龄鼠IRI后1d细胞衰老和凋亡进行相关分析显示,二者呈显著负相关Cp21(+/+)鼠:r=-0.82,P〈0.001,p21(-/-)鼠:r=-0.76,P〈0.0013。结论 ①IRI可促进正常肾小管上皮细胞衰老的进程;②已经进入衰老状态的肾小管上皮细胞在遭受IRI刺激后,更易走向死亡[坏死和(或)凋亡];③p21在IRI所致肾小管上皮细胞演变过程中发挥重要的调控作用。  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