全文获取类型
收费全文 | 2640篇 |
免费 | 271篇 |
国内免费 | 46篇 |
专业分类
耳鼻咽喉 | 16篇 |
儿科学 | 122篇 |
妇产科学 | 40篇 |
基础医学 | 315篇 |
口腔科学 | 51篇 |
临床医学 | 360篇 |
内科学 | 445篇 |
皮肤病学 | 48篇 |
神经病学 | 104篇 |
特种医学 | 306篇 |
外科学 | 418篇 |
综合类 | 221篇 |
预防医学 | 191篇 |
眼科学 | 40篇 |
药学 | 137篇 |
2篇 | |
中国医学 | 33篇 |
肿瘤学 | 108篇 |
出版年
2022年 | 34篇 |
2021年 | 50篇 |
2020年 | 43篇 |
2019年 | 25篇 |
2018年 | 37篇 |
2017年 | 39篇 |
2016年 | 35篇 |
2015年 | 53篇 |
2014年 | 62篇 |
2013年 | 104篇 |
2012年 | 119篇 |
2011年 | 113篇 |
2010年 | 105篇 |
2009年 | 120篇 |
2008年 | 92篇 |
2007年 | 105篇 |
2006年 | 98篇 |
2005年 | 77篇 |
2004年 | 75篇 |
2003年 | 68篇 |
2002年 | 64篇 |
2001年 | 52篇 |
2000年 | 50篇 |
1999年 | 50篇 |
1998年 | 88篇 |
1997年 | 80篇 |
1996年 | 74篇 |
1995年 | 71篇 |
1994年 | 44篇 |
1993年 | 51篇 |
1992年 | 24篇 |
1991年 | 26篇 |
1990年 | 28篇 |
1989年 | 45篇 |
1988年 | 50篇 |
1987年 | 46篇 |
1986年 | 38篇 |
1985年 | 39篇 |
1984年 | 28篇 |
1983年 | 30篇 |
1979年 | 21篇 |
1978年 | 19篇 |
1977年 | 22篇 |
1976年 | 19篇 |
1959年 | 22篇 |
1958年 | 30篇 |
1957年 | 19篇 |
1956年 | 30篇 |
1955年 | 42篇 |
1954年 | 35篇 |
排序方式: 共有2957条查询结果,搜索用时 15 毫秒
41.
The status of women at one academic medical center. Breaking through the glass ceiling 总被引:2,自引:0,他引:2
Despite recent gains in admission to medical school and in obtaining junior faculty positions, women remain underrepresented at senior academic ranks and in leadership positions in medicine. This discrepancy has been interpreted as evidence of a "glass ceiling" that prevents all but a few exceptional women from gaining access to leadership positions. We analyzed data from Columbia University College of Physicians & Surgeons, New York, NY, for all faculty hired from 1969 through 1988 and found that the likelihood of promotion on the tenure track was 0.40 for women and 0.48 for men (ratio, 0.82; 95% confidence interval, 0.56 to 1.20); on the clinical track the likelihood of promotion was 0.75 for women and 0.72 for men (ratio, 1.04; 95% confidence interval, 0.56 to 1.94). Additional analysis of current faculty showed that in the academic year 1988-1989 the proportion of women at each tenure track rank at the College of Physicians & Surgeons equaled or exceeded the national proportion of women graduating from medical school, once allowance was made for the average time lag necessary to attain each rank. On the clinical track women were somewhat overrepresented, particularly at the junior rank. National data that describe medical school faculty, which combine tenure and clinical tracks, showed that in 1988 women were proportionately represented at each rank once the lead time from graduation was considered. We conclude that objective evidence shows that women can succeed and are succeeding in gaining promotions in academic medicine. 相似文献
42.
目的 探讨人胰弹力蛋白酶Ⅰ (Humanpancreaticelastase 1 ,HPE1 )放射免疫测定 (Radioimmunoassay ,RIA)和核糖核酸酶(Ribonuclease ,RNase)活性检测的临床价值。方法 参照Satake等建立的改良HPE1RIA和Thomas等的改良酸溶性产物法检测 82例正常成年人和 2 2 2例各类患者血清并分析结果。结果 82例健康成人HPE1值为 2 3.8( 3.4ng L) ,RNase活性为 5 7.0 3( 1 2 .1 6 μ ml) ;急性胰腺炎和胰腺癌HPE1 值明显高于其他疾病 (P <0 .0 1 )。联合检测HPE1 、RNase活性可提高胰腺癌的检出率 ( 92 .47% )。结论 HPE1 RIA对急性胰腺炎有诊断价值 ,联合检测HPE1 、RNase活性检测对胰腺癌诊断有一定的临床价值 相似文献
43.
Does subclinical rejection contribute to chronic rejection in renal transplant patients? 总被引:6,自引:0,他引:6
Rush DN Karpinski ME Nickerson P Dancea S Birk P Jeffery JR 《Clinical transplantation》1999,13(6):441-446
Renal allograft biopsies have traditionally been performed in the setting of acute graft dysfunction. However, several groups have performed graft biopsies at times of stable graft function, and more recently, after treatment of rejection episodes. Surprisingly, unequivocal histologic criteria for acute rejection have been demonstrated in a high proportion of these protocol biopsies. The Winnipeg Transplant Group has documented the high prevalence of clinically silent inflammatory infiltrates in early protocol biopsies, and demonstrated their inflammatory and cytotoxic potential by immunohistochemical and molecular biological techniques. Furthermore, in a randomized trial, our group has demonstrated that subclinical rejection, if untreated, is associated with the development of early chronic pathology and late graft dysfunction. In this overview, we will summarize the early data on subclinical allograft inflammation, present the experience of the Winnipeg Transplant Group, and discuss the possible implications of subclinical rejection on the development of chronic rejection. 相似文献
44.
In this work we use a computer simulation to estimate the magnitude of improvement in the signal-to-noise ratio of PET functional brain mapping studies as a function of partition coefficient and permeability surface product for O-14, F-17, and O-15 labeled flow tracers. A model for signal-to-noise ratio is derived from the Kety model for inert diffusible blood flow tracers. The results of the simulation suggest that moderate increases in partition coefficient and permeability surface product compared with water would lead to an increase in signal-to-noise ratio of a factor of about 3. 相似文献
45.
Objectives. To examine the effects of bicalutamide (Casodex), a pure antiandrogen with high specificity for the androgen receptor, on insulin-like growth factor binding protein (IGFBP) expression and apoptotic regression of the rat ventral prostate.Methods. Rats were treated daily with 10 mg/kg body weight bicalutamide or vehicle alone. Ventral prostates were collected at various days of treatment. Northern blot analysis was performed to quantitate expression of genes encoding IGFBPs, and the TUNEL method was used to determine the extent of apoptosis in ventral prostate.Results. In rats treated daily with bicalutamide, increases in mRNA levels of IGFBP-2, -3, -4, and -5 were detectable by Northern blotting by 6 hours and reached 6 to 10-fold of control levels after 5 days of treatment. The time-course of induction of apoptosis in the ventral prostate by bicalutamide, as detected in situ by the TUNEL method, corresponded to the time-course of induction of IGFBP expression.Conclusions. We demonstrate that apoptotic regression of the ventral prostate during bicalutamide treatment is accompanied by increased expression of IGFBP-2, -3, -4, and -5. Rapid induction of IGFBPs, which can limit access of insulin-like growth factors (IGFs) to the IGF-I receptor, may play a role in the induction of apoptosis by antiandrogens, particularly in view of the increasing evidence that IGF-I inhibits apoptosis. These results document a previously unrecognized effect of antiandrogens and extend our previous studies relating IGF physiology to prostate biology. Together with evidence that a strong positive correlation exists between plasma IGF-I levels and prostate cancer risk, our data suggest that IGF physiology may play a key role in prostate cancer biology and is strongly influenced by androgen-targeting therapies. 相似文献
46.
磺胺类药物的毛细管高效液相色谱与电色谱研究 总被引:4,自引:0,他引:4
目的 研究毛细管高效液相色谱(μ-HPLC)和毛细管电色谱(CEC)分离磺胺类药物,建立药物微分离分析方法。方法 用ODS柱为固定相,甲醇和2 mmol·L-1磷酸缓冲液(pH 3.0~7.0)为流动相,电压为0~-15 kV,流速为10 μL·min-1,紫外检测波长254 nm。结果μ-HPLC在甲醇-2 mmol·L-1磷酸缓冲液(30∶70),pH 3.0时5种磺胺类药物实现基线分离;CEC在电压为-5 kV,甲醇-2 mmol·L-1磷酸缓冲液(30∶70),pH 5.0时5种磺胺类药物实现基线分离。结论电渗流随甲醇含量、缓冲液浓度增加而下降,随pH值、电压的增加而增加;溶质的保留值(k)随甲醇含量、缓冲液浓度、电压的增加而下降,随电压增加下降明显的是TMP,随pH值变化较复杂。在相同条件下对5种磺胺类药物的分离,μ-HPLC需67 min,CEC只需25 min,后者更适合于磺胺类药物的快速分离分析。 相似文献
47.
48.
Identification of differentially expressed genes in aflatoxin B1- treated cultured primary rat hepatocytes and Fischer 344 rats 总被引:4,自引:1,他引:4
Harris AJ; Shaddock JG; Manjanatha MG; Lisenbey JA; Casciano DA 《Carcinogenesis》1998,19(8):1451-1458
Aflatoxin B1 (AFB1), a mutagen and hepatocarcinogen in rats and humans, is
a contaminant of the human food supply, particularly in parts of Africa and
Asia. AFB1-induced changes in gene expression may play a part in the
development of the toxic, immunosuppressive and carcinogenic properties of
this fungal metabolite. An understanding of the-role of AFB1 in modulating
gene regulation should provide insight regarding mechanisms of AFB1-induced
carcinogenesis. We used three PCR- based subtractive techniques to identify
AFB1-responsive genes in cultured primary rat hepatocyte RNA: differential
display PCR (DD-PCR), representational difference analysis (RDA) and
suppression subtractive hybridization (SSH). Each of the three techniques
identified AFB1- responsive genes, although no individual cDNA was isolated
by more than one technique. Nine cDNAs isolated using DD-PCR, RDA or SSH
were found to represent eight genes that are differentially expressed as a
result of AFB1 exposure. Genes whose mRNA levels were increased in cultured
primary rat hepatocytes after AFB1 treatment were corticosteroid binding
globulin (CBG), cytochrome P450 4F1 (CYP4F1), alpha-2 microglobulin,
C4b-binding protein (C4BP), serum amyloid A-2 and glutathione S-transferase
Yb2 (GST). Transferrin and a small CYP3A-like cDNA had reduced mRNA levels
after AFB1 exposure. Full-length CYP3A mRNA levels were increased. When
liver RNA from AFB1-treated male F344 rats was evaluated for transferrin,
CBG, GST, CYP3A and CYP4F1 expression, a decrease in transferrin mRNA and
an increase in CBG, GST, CYP3A and CYP4F1 mRNA levels was also seen.
Analysis of the potential function of these genes in maintaining cellular
homeostasis suggests that their differential expression could contribute to
the toxicity associated with AFB1 exposure.
相似文献
49.
Effect of genetic modification of acute inflammatory responsiveness on tumorigenesis in the mouse 总被引:1,自引:3,他引:1
50.
Sarah B. Laditka PhD ; James N. Laditka DA PhD ; Kevin J. Bennett MS PhD ; Janice C. Probst PhD 《The Journal of rural health》2005,21(2):158-166
CONTEXT: Pregnancy complications affect many women. It is likely that some complications can be avoided through routine primary and prenatal care of reasonable quality. PURPOSE: The authors examined access to health care during pregnancy for mothers insured by Medicaid. The access indicator is potentially avoidable maternity complications (PAMCs). Potentially avoidable maternity complications are often preventable through routine prenatal care, such as infection screening and treatment. The authors examined the risks of potentially avoidable maternity complications among rural and urban hospital deliveries for groups of mothers defined by race or ethnicity. METHODS: Data are from the year 2000 Nationwide Inpatient Sample (NIS). The stratified sample represents all discharges from 20.5% of community hospitals in the United States. The Nationwide Inpatient Sample identifies hospital locations, but not patients' areas of residence. Analyses, which accounted for the sample design, included calculation of potentially avoidable maternity complication rates by race or ethnicity, chi2, t tests, and multivariate logistic regression. FINDINGS: Within groups defined by race or ethnicity, unadjusted rates for potentially avoidable maternity complications did not differ significantly by hospital location. Holding other factors constant, potentially avoidable maternity complications were less common in rural hospitals than in urban hospitals (odds ratio, 0.78; CI, 0.62 to 0.99). In rural hospitals, African Americans had notably higher risk for potentially avoidable maternity complications than did non-Hispanic whites (odds ratio, 1.72; CI, 1.26 to 2.36). In urban hospitals, risk of potentially avoidable maternity complications was not significantly higher for African Americans. Hispanics and Asians had notably lower risks of potentially avoidable maternity complications in urban hospitals than did non-Hispanic whites. CONCLUSIONS: Providers and policymakers should work to reduce the risks of potentially avoidable maternity complications for African American women in rural areas who are insured by Medicaid. 相似文献