全文获取类型
收费全文 | 2174篇 |
免费 | 151篇 |
国内免费 | 14篇 |
专业分类
耳鼻咽喉 | 50篇 |
儿科学 | 127篇 |
妇产科学 | 84篇 |
基础医学 | 209篇 |
口腔科学 | 54篇 |
临床医学 | 281篇 |
内科学 | 372篇 |
皮肤病学 | 29篇 |
神经病学 | 52篇 |
特种医学 | 412篇 |
外科学 | 196篇 |
综合类 | 25篇 |
一般理论 | 13篇 |
预防医学 | 227篇 |
眼科学 | 23篇 |
药学 | 54篇 |
肿瘤学 | 131篇 |
出版年
2023年 | 9篇 |
2021年 | 23篇 |
2020年 | 12篇 |
2019年 | 19篇 |
2018年 | 29篇 |
2017年 | 21篇 |
2016年 | 21篇 |
2015年 | 32篇 |
2014年 | 47篇 |
2013年 | 65篇 |
2012年 | 76篇 |
2011年 | 72篇 |
2010年 | 70篇 |
2009年 | 59篇 |
2008年 | 67篇 |
2007年 | 99篇 |
2006年 | 75篇 |
2005年 | 80篇 |
2004年 | 67篇 |
2003年 | 44篇 |
2002年 | 55篇 |
2001年 | 43篇 |
2000年 | 48篇 |
1999年 | 55篇 |
1998年 | 105篇 |
1997年 | 78篇 |
1996年 | 83篇 |
1995年 | 57篇 |
1994年 | 60篇 |
1993年 | 68篇 |
1992年 | 18篇 |
1991年 | 20篇 |
1990年 | 21篇 |
1989年 | 48篇 |
1988年 | 33篇 |
1987年 | 44篇 |
1986年 | 28篇 |
1985年 | 39篇 |
1984年 | 35篇 |
1983年 | 22篇 |
1982年 | 25篇 |
1981年 | 29篇 |
1980年 | 36篇 |
1979年 | 15篇 |
1978年 | 19篇 |
1977年 | 26篇 |
1976年 | 25篇 |
1975年 | 19篇 |
1922年 | 14篇 |
1921年 | 13篇 |
排序方式: 共有2339条查询结果,搜索用时 15 毫秒
21.
Hypospadias trends in two US surveillance systems 总被引:6,自引:0,他引:6
OBJECTIVE: Hypospadias is a common congenital anomaly, the cause of which is unknown. Unexplained increases in the rates of hypospadias occurred in five European countries in the 1970s and 1980s. We examined data from two birth defects surveillance systems in the United States for evidence of similar trends. METHODOLOGY: The Metropolitan Atlanta Congenital Defects Program (MACDP) provided birth prevalence rates from 1968 to 1993. The nationwide Birth Defects Monitoring Program (BDMP) provided rates from 1970 to 1993. MACDP data are population-based and could be categorized by the severity of the hypospadias. BDMP data allowed analysis of rate trends for the four census regions of the United States. RESULTS: Data from both surveillance systems showed an approximate doubling of hypospadias rates in the 1970s and 1980s. MACDP data showed that the rate of severe cases increased while the ratio of mild to severe cases decreased. BDMP data showed that hypospadias rates increased markedly in all four regions of the United States. CONCLUSIONS: The observed increases are unlikely to be attributable to increased sensitivity of the surveillance systems or the identification of more mild cases by physicians over time, because either trend would have increased rather than decreased the ratio of mild to severe cases. If real, these trends represent the largest number of cases and the first report of an increase in hypospadias rates outside of Europe. Additional investigation of a possible increase in hypospadias rates is warranted. 相似文献
22.
Gonzales AJ; Christensen JG; Preston RJ; Goldsworthy TL; Tlsty TD; Fox TR 《Carcinogenesis》1998,19(7):1173-1183
23.
Guo RJ; Wang Y; Kaneko E; Wang DY; Arai H; Hanai H; Takenoshita S; Hagiwara K; Harris CC; Sugimura H 《Carcinogenesis》1998,19(9):1539-1544
Mutations in the transforming growth factor beta type II receptor
(TGFbetaRII) gene have been detected in several human cancer types
exhibiting microsatellite instability. Using intron primers previously
reported for examination of the entire coding region of the TGFbetaRII
gene, 29 sporadic gastric cancers were screened with non-radioactive single
strand conformation polymorphism and subsequent DNA sequencing analysis.
Mutations of the TGFbetaRII gene were detected in three out of 29 tumors
(10%). Two cases showed deletions in a polyadenine tract in both alleles
and was positively associated with replication error. One case had an
insertion of GA dinucleotide sequence in one allele. Mutations of the
TGFbetaRII gene were restricted to exon 3 and other coding regions were not
affected. Loss of heterozygosity was detected by analyzing a polymorphic
site in intron 2. Three out of nine (33%) informative cases, which were all
of intestinal type and advanced cases, showed loss of heterozygosity but
neither TGFbetaRII mutation nor replication error was found in these cases.
Immunoreactivity of TGFbetaRII in tumor tissues was reduced to a different
extent in the gastric cancer with genetically abnormal transforming growth
factor. Although the numbers studied are small, homozygous (A)10 deletion
or loss of heterozygosity of TGFbetaRII is involved in tumorigenesis and
progression of at least some part of sporadic gastric cancer.
相似文献
24.
25.
Tumour cell growth may be accelerated by protein kinase C (PKC) agonists
such as phorbol esters and receptor tyrosine kinases, but receptor tyrosine
kinases are in turn desensitized to growth factors by PKC agonists. To
clarify this apparent PKC bifunctionality, we have used phosphoantibodies
to determine the relationship between PKC- dependent phosphorylation events
affecting the ErbB2 oncoprotein in G8/DHFR 3T3 cells. Neither the kinetics
nor the extent of phorbol- induced juxtamembrane domain (Thr686)
phosphorylation vary directly with C-terminal (Tyr1222) dephosphorylation,
with Tyr1222 continuing to be dephosphorylated long after Thr686
phosphorylation has also declined. Platelet-derived growth factor (PDGF)
mimics the short-term effects of phorbol on Thr686 and Tyr1222
phosphorylation, and confocal microscopy reveals that both of these PKC
agonists induce rapid internalization of PKC-modified ErbB2. Phorbol causes
sustained cytoplasmic accumulation of PKC-phosphorylated receptors,
however, whereas PDGF triggers the appearance of this ErbB2 subset only
briefly. Metabolic labelling and co-precipitation studies fail to implicate
heterologous molecules in either the tyrosine dephosphorylation or
internalization of PKC-modified ErbB2. Taken in the context of earlier
juxtamembrane domain mutagenesis studies, these findings indicate that
phorbol-activated PKC may desensitize growth factor receptors to
extracellular ligands solely by triggering sustained receptor
internalization. We submit that PKC-dependent juxtamembrane domain
phosphorylation represents a physiological mechanism for shortening the
duration and enhancing the specificity of growth factor signalling by
promoting internalization of liganded and unliganded receptors,
respectively.
相似文献
26.
27.
18F]fluorodeoxyglucose uptake by positron emission tomography predicts outcome of non-small-cell lung cancer. 总被引:9,自引:0,他引:9
Ryohei Sasaki Ritsuko Komaki Homer Macapinlac Jeremy Erasmus Pamela Allen Kenneth Forster Joe B Putnam Roy S Herbst Cesar A Moran Donald A Podoloff Jack A Roth James D Cox 《Journal of clinical oncology》2005,23(6):1136-1143
PURPOSE: To determine whether the standardized uptake value (SUV) of [(18)F]fluorodeoxyglucose uptake by positron emission tomography could be a prognostic factor for non-small-cell lung cancer (NSCLC). PATIENTS AND METHODS: One hundred sixty-two patients with stage I to IIIb NSCLC were analyzed. Overall survival (OS), disease-free survival (DFS), distant metastasis-free survival (DMFS), and local-regional control (LRC) were calculated by the Kaplan-Meier method and evaluated with the log-rank test. The prognostic significance was assessed by univariate and multivariate analyses. RESULTS: There were 93 patients treated with surgery and 69 patients treated with radiotherapy. A cutoff of 5 for the SUV for the primary tumor showed the best discriminative value. The SUV for the primary tumor was a significant predictor of OS (P = .02) in both groups. Low SUVs (= 5.0) showed significantly better DFS rates than those with high SUVs (> 5.0; surgery group, P = .02; radiotherapy group, P = .0005). Low SUVs (= 5.0) indicated a significantly better DFS than those with high SUVs (> 5.0; stage I or II, P = .02; stage IIIa or IIIb, P = .004). However, using the same cutoff point of 5, the SUV for regional lymph nodes was not a significant indicator for DFS (P = .19), LRC (P = .97), or DMFS (P = .17). The multivariate analysis showed that the SUV for the primary tumor was a significant prognostic factor for OS (P = .03) and DFS (P = .001). CONCLUSION: The SUV of the primary tumor was the strongest prognostic factor among the patients treated by curative surgery or radiotherapy. 相似文献
28.
Macapinlac HA 《Cancer journal (Sudbury, Mass.)》2004,10(4):262-270
FDG PET imaging is rapidly gaining acceptance in numerous clinical applications in oncology. PET/CT is a new imaging tool, which takes advantage of the excellent anatomic resolution of CT and the biologic characterization provided by FDG PET which together results in improvement in accuracy of detecting the extent of disease, provide a guide to biopsy or surgery, allow early response evaluation and prognostication. This article will provide specific clinical applications for the utilization of these imaging modalities in both lymphoma and melanoma. 相似文献
29.
30.