全文获取类型
收费全文 | 1572篇 |
免费 | 82篇 |
国内免费 | 13篇 |
专业分类
耳鼻咽喉 | 9篇 |
儿科学 | 93篇 |
妇产科学 | 103篇 |
基础医学 | 121篇 |
口腔科学 | 42篇 |
临床医学 | 165篇 |
内科学 | 323篇 |
皮肤病学 | 45篇 |
神经病学 | 64篇 |
特种医学 | 145篇 |
外科学 | 117篇 |
综合类 | 135篇 |
预防医学 | 95篇 |
眼科学 | 10篇 |
药学 | 90篇 |
1篇 | |
中国医学 | 74篇 |
肿瘤学 | 35篇 |
出版年
2021年 | 15篇 |
2020年 | 10篇 |
2018年 | 12篇 |
2017年 | 18篇 |
2016年 | 14篇 |
2015年 | 33篇 |
2014年 | 42篇 |
2013年 | 42篇 |
2012年 | 48篇 |
2011年 | 51篇 |
2010年 | 54篇 |
2009年 | 45篇 |
2008年 | 45篇 |
2007年 | 35篇 |
2006年 | 39篇 |
2005年 | 21篇 |
2004年 | 19篇 |
2003年 | 16篇 |
2002年 | 15篇 |
2001年 | 21篇 |
2000年 | 12篇 |
1999年 | 24篇 |
1998年 | 44篇 |
1997年 | 55篇 |
1996年 | 50篇 |
1995年 | 43篇 |
1994年 | 55篇 |
1993年 | 36篇 |
1992年 | 17篇 |
1991年 | 17篇 |
1990年 | 14篇 |
1989年 | 28篇 |
1988年 | 27篇 |
1987年 | 30篇 |
1986年 | 25篇 |
1985年 | 16篇 |
1984年 | 16篇 |
1983年 | 16篇 |
1982年 | 13篇 |
1981年 | 23篇 |
1980年 | 16篇 |
1959年 | 35篇 |
1958年 | 58篇 |
1957年 | 87篇 |
1956年 | 45篇 |
1955年 | 75篇 |
1954年 | 67篇 |
1953年 | 17篇 |
1952年 | 14篇 |
1949年 | 10篇 |
排序方式: 共有1667条查询结果,搜索用时 0 毫秒
21.
目的:应用微乳液反应法制备磺胺嘧啶银均匀微晶,均匀制得的微晶的粒径大小约为2~4um,均匀微晶的结晶性好,纯度高。用均匀设计方法优化条件,制备的均匀的微晶平均粒径大小为2.09um,实验结果达到预测结果要求。结论:用微乳液反应法能获得磺胺嘧啶银均匀微晶。 相似文献
22.
微乳液反应法制备磺胺嘧啶银均匀微晶及其质量评价 总被引:1,自引:0,他引:1
目的:应用微乳液反应法制备磺胺嘧啶银均匀微晶,并评价其质量。方法:利用磺胺嘧啶钠微乳和硝酸银微乳混合后反应的方法,制备磺胺嘧啶银均匀微晶,用透射电镜观察其形态和大小,以X-射线衍射分析、红外光谱、核磁共振、差热分析等手段检测磺胺嘧啶银均匀微晶各种理化特性。结果:磺胺嘧啶银均匀微晶的粒径大小约为2~4μm,均匀微晶的结晶性好,纯度高。体外抑菌实验表明该品比市售磺胺嘧啶银具有更好的抑菌效果。结论:用微乳液反应法能获得磺胺嘧啶银均匀微晶。 相似文献
23.
OBJECTIVES: To determine the relative magnitudes of neuron-specific enolase (NSE) levels after complex partial status epilepticus (SE), absence SE, generalized convulsive SE, and subclinical generalized convulsive SE (frequently referred to as acute symptomatic myoclonic status epilepticus). BACKGROUND: NSE is a marker of acute brain injury and blood-brain barrier dysfunction, which is elevated in SE. METHODS: Serum NSE levels were drawn in 31 patients 1, 2, 3, and 7 days after SE. Patients were classified as acute symptomatic or remote symptomatic, and the duration and outcome of SE were determined and correlated with the peak NSE level. RESULTS: NSE was elevated significantly in all four subtypes of SE, but NSE levels were highest in complex partial and subclinical SE. The mean peak NSE level for the complex partial SE group was 23.88 ng/mL (n = 12), 21.5 ng/mL for absence SE (n = 1), 14.10 ng/mL for the generalized convulsive SE group (n = 12), and 37.83 ng/mL for the subclinical SE group (n = 6), all of which was significantly higher than normal control subjects (5.02 ng/mL). Outcome was significantly different between the three groups (p = 0.0007), and was significantly worse for subclinical SE (p = 0.0005, subclinical versus generalized convulsive SE). CONCLUSION: Serum NSE levels were highest in complex partial and subclinical generalized convulsive SE. The extremely high levels of NSE in subclinical SE reflect the severity of the acute neurologic insults and poor outcome common to subclinical SE. High NSE levels in complex partial SE reflects the long duration of SE in this subgroup, and potential for brain injury. 相似文献
24.
Economic costs of functional dyspepsia 总被引:5,自引:0,他引:5
Dyspepsia is defined as chronic or recurrent symptoms believed to originate in the upper gastrointestinal tract. When routine investigation results in no identifiable explanation for those symptoms patients are labelled as having functional dyspepsia. In community-based surveys, approximately 30% of the otherwise apparently healthy population report dyspeptic symptoms and the majority are believed to have functional dyspepsia. Although only 1 in 4 or 5 patients make use of healthcare resources, this patient category is one of the largest in ambulatory care (1.6 to 5% of all consultations in general practice). The annual frequency of consultations for functional dyspepsia in Sweden has been estimated at 47 per 1000 population. In consequence of its high prevalence and associated absenteeism, the total costs of functional dyspepsia are considerable. In Sweden in 1981, the costs were estimated at $US55 000 per 1000 population ($US113 630 in 1991 dollars). The most cost-effective management strategy remains to be defined. Evidence is accumulating that the traditional 'wait-and-see' policy with initial empirical therapeutic trials without investigation may not be the most cost conserving strategy. 相似文献
25.
Auditory event-related potentials (ERPs) were performed in 20 patients with nontraumatic coma to determine the presence of a P300 ERP in coma and its association with the Glasgow Coma Score and awakening (Glasgow Outcome Score, > or = 3). A standard "oddball" paradigm was used: frequent tone, 1 kHz; rare tone, 2 kHz and 4 Hz; probability, 20%. The Glasgow Coma Score was determined concurrently with the P300 ERP. Thirty percent (6/20) of the comatose patients had a P300 ERP. The mean Glasgow Coma Score was significantly higher for those with a P300 ERP. Eighty-three percent (5/6) of those with a P300 ERP awoke. Presence of a P300 ERP was associated significantly with awakening, but absence of a P300 ERP did not preclude it. 相似文献
26.
The involvement of the proliferating cell nuclear antigen (PCNA) in the
process of DNA repair induced by alkylating agents or by oxidative damage
was investigated in human quiescent fibroblasts by immunofluorescence and
flow cytometry. Transition from soluble to the DNA-bound form of PCNA, was
taken as the parameter to determine its involvement in repair DNA
synthesis. Treatment with the alkylating agents methylmethane sulfonate and
N-methyl-N'-nitro-N-nitrosoguanidine resulted in the rapid and
dose-dependent increase in the nuclear binding of PCNA. Similar results
were obtained with compounds such as hydrogen peroxide or tert-butyl
hydroperoxide, which are known to induce oxidative DNA damage. Tert-butyl
hydroperoxide may also generate malondialdehyde through a reaction of lipid
peroxidation. This mutagenic and carcinogenic product has been previously
shown to form adducts with DNA. Therefore, the possibility that tert-butyl
hydroperoxide could induce DNA damage through this pathway was investigated
by incubating cells directly in the presence of malondialdehyde. Such
treatment resulted in an increase in immunofluorescence associated with
nuclear-bound PCNA. The ability of oxidative and alkylating agents to
induce the nuclear binding of PCNA was also assessed in proliferating
cells. In these conditions, treatment with hydrogen peroxide or
methylmethane sulfonate, resulted in an increase in nuclear-bound PCNA in
the G1 and in the G2 + M compartments, but not in S phase. At longer times
after treatment, PCNA immunostaining was reduced to basal levels, while an
increase in nuclear binding of p21(waf1/cip1) protein was found in
concomitance with cell-cycle arrest. These results indicate that agents
inducing DNA base alterations in vivo, promote the nuclear binding of PCNA.
These lines of evidence support the role of a PCNA-dependent reaction in
the base excision repair system.
相似文献
27.
Hansen LA; Malarkey DE; Wilkinson JE; Rosenberg M; Woychik RE; Tennant RW 《Carcinogenesis》1998,19(10):1837-1845
We previously reported that papillomas can arise from the follicular
epithelium of v-Ha-ras transgenic TGxAC mice. Since the viable-yellow
mutation (A(vy)) of the mouse agouti gene which regulates coat color
pigmentation by acting within the micro-environment of the hair follicle
has been shown to function as a tumor promoter in the liver, we
hypothesized that it may also play a role in TGxAC skin tumorigenesis.
Endogenous agouti protein product was detected in the outer root sheath of
anagen hair follicles following plucking of the hair shaft, but not in the
interfollicular epithelium, in TGxAC mice on an FVB/N genetic background.
It was also detected in papillomas from these mice produced by
12-O-tetradecanoylphorbol-13-acetate (TPA) treatment or plucking.
Expression of the A(vy) allele in the v-Ha-ras transgenic TGxAC mouse line
results in an approximately 2-fold increase in papilloma development
compared with controls which did not carry the A(vy) allele following
twice-weekly treatment with 1.25, 2.5 or 5.0 microg TPA. In addition,
TPA-treated, papilloma-bearing F1 mice which carried the A(vy) allele, but
not F1 mice which did not carry the A(vy) allele, exhibited a syndrome of
humoral hypercalcemia mediated by parathyroid hormone-related protein
(PTHrP) that led to weight loss, hypercalcemia and hypophosphatemia. Thus,
we conclude that the A(vy) allele can influence the development of skin
tumors and PTHrP-mediated humoral hypercalcemia in v-Ha-ras transgenic
TGxAC mice.
相似文献
28.
Non-invasive detection of fecal protein kinase C betaII and zeta messenger RNA: putative biomarkers for colon cancer 总被引:2,自引:0,他引:2
Davidson LA; Aymond CM; Jiang YH; Turner ND; Lupton JR; Chapkin RS 《Carcinogenesis》1998,19(2):253-257
We have developed a non-invasive method utilizing feces, containing
sloughed colonocytes, as a sensitive technique for detecting diagnostic
colonic biomarkers. In this study, we used the rat colon carcinogenesis
model to determine if changes in fecal protein kinase C (PKC) expression
have predictive value in monitoring the neoplastic process. Weanling rats
were injected with saline or azoxymethane (AOM) and 36 weeks later fecal
samples and mucosa were collected, poly A+ RNA isolated, and quantitative
RT-PCR performed using primers to PKC betaII and zeta. Fecal PKC betaII and
zeta mRNA levels were altered by the presence of a tumor, with
tumor-bearing animals having a 3-fold higher (P < 0.05) PKC betaII
expression as compared with animals without tumors. In addition,
AOM-injection increased mucosal PKC betaII mRNA expression compared with
saline controls. No effect of tumor incidence on mucosal PKC betaII
expression was observed. In contrast, fecal PKC zeta expression was
2.5-fold lower (P < 0.05) in animals injected with azoxymethane versus
saline. Since tumor incidence exerts a reciprocal effect on fecal PKC
betaII and zeta mRNA expression, data were also expressed as the ratio
between PKC betaII and zeta. The isozyme ratio was strongly related to
tumor incidence, i.e. ratio for animals with tumors was 2.18 +/- 1.25,
animals without tumors was 0.50 +/- 0.16, P = 0.025. We demonstrate that
the expression of fecal PKC betaII and zeta may serve as a noninvasive
marker for development of colon tumors. A sensitive technique for the
detection of colon cancer is of importance since early diagnosis can
substantially reduce mortality.
相似文献
29.
宫颈病变液基细胞学筛查与组织病理学对照观察 总被引:5,自引:1,他引:5
目的 探讨液基薄层细胞学(ThinPrepCytologyTest, TCT)技术在妇科门诊人群宫颈病变筛查的准确性。方法 回顾性分析10 980例TCT,与组织学对比观察。结果 TCTLSIL以上阳性率45. 7% ( 373 /817),组织学检查阳性率50. 1% ( 409 /817 ),两者统计学比较无显著性差异(P>0. 05 )。TCT诊断符合率LSIL75. 8% (191 /252),HSIL98. 1% (101 /103),SCC90. 9% (10 /11),AC85. 7% (6 /7)。鳞状上皮内病变诊断符合率HSIL与LSIL统计学比较有显著性差异(P<0. 01)。结论 液基细胞学检查是宫颈癌早期筛查的有效手段,加强制片技术及诊断质量控制对提高诊断的准确性有重要意义。 相似文献
30.