全文获取类型
收费全文 | 1898篇 |
免费 | 127篇 |
国内免费 | 25篇 |
专业分类
耳鼻咽喉 | 3篇 |
儿科学 | 197篇 |
妇产科学 | 39篇 |
基础医学 | 217篇 |
口腔科学 | 96篇 |
临床医学 | 175篇 |
内科学 | 394篇 |
皮肤病学 | 43篇 |
神经病学 | 56篇 |
特种医学 | 337篇 |
外科学 | 113篇 |
综合类 | 27篇 |
一般理论 | 1篇 |
预防医学 | 96篇 |
眼科学 | 42篇 |
药学 | 107篇 |
1篇 | |
中国医学 | 1篇 |
肿瘤学 | 105篇 |
出版年
2023年 | 10篇 |
2022年 | 10篇 |
2021年 | 24篇 |
2020年 | 19篇 |
2019年 | 23篇 |
2018年 | 38篇 |
2017年 | 24篇 |
2016年 | 30篇 |
2015年 | 47篇 |
2014年 | 47篇 |
2013年 | 66篇 |
2012年 | 50篇 |
2011年 | 48篇 |
2010年 | 60篇 |
2009年 | 94篇 |
2008年 | 29篇 |
2007年 | 52篇 |
2006年 | 54篇 |
2005年 | 48篇 |
2004年 | 33篇 |
2003年 | 41篇 |
2002年 | 25篇 |
2001年 | 29篇 |
2000年 | 27篇 |
1999年 | 31篇 |
1998年 | 106篇 |
1997年 | 118篇 |
1996年 | 114篇 |
1995年 | 79篇 |
1994年 | 82篇 |
1993年 | 98篇 |
1992年 | 18篇 |
1991年 | 20篇 |
1990年 | 19篇 |
1989年 | 46篇 |
1988年 | 43篇 |
1987年 | 31篇 |
1986年 | 34篇 |
1985年 | 31篇 |
1984年 | 19篇 |
1983年 | 16篇 |
1982年 | 21篇 |
1981年 | 36篇 |
1980年 | 24篇 |
1979年 | 15篇 |
1977年 | 23篇 |
1976年 | 23篇 |
1975年 | 9篇 |
1974年 | 10篇 |
1973年 | 12篇 |
排序方式: 共有2050条查询结果,搜索用时 15 毫秒
21.
Dibenzo[a,l]pyrene-induced DNA adduction, tumorigenicity, and Ki-ras oncogene mutations in strain A/J mouse lung 总被引:1,自引:0,他引:1
Prahalad AK; Ross JA; Nelson GB; Roop BC; King LC; Nesnow S; Mass MJ 《Carcinogenesis》1997,18(10):1955-1963
Dibenzo[a,l]pyrene (DB[a,l]P), an environmental polycyclic aromatic
hydrocarbon, is the most potent carcinogen ever tested in mouse skin and
rat mammary gland. In this study, DB[a,l]P was examined for DNA adduction,
tumorigenicity, and induction of Ki-ras oncogene mutations in tumor DNA in
strain A/J mouse lung. Groups of mice received a single i.p. injection of
0.3, 1.5, 3.0, or 6.0 mg/kg DB[a,l]P in tricaprylin. Following treatment,
DNA adducts were measured at times between 1 and 28 days, while tumors were
counted at 250 days and analyzed for the occurrence of point mutations in
codons 12 and 61 of the Ki-ras oncogene. DB[a,l]P in strain A/J mouse lung
induced six major and four minor DNA adducts. Maximal levels of adduction
occurred between 5 and 10 days after injection followed by a gradual
decrease. DB[a,l]P-DNA adducts in lung tissue were derived from both anti-
and syn-11,12- dihydroxy-13,14-epoxy-
11,12,13,14-tetrahydrodibenzo[a,l]pyrene (DB[a,l]PDE) and both
deoxyadenosine (dAdo) and deoxyguanosine (dGuo) residues in DNA as revealed
by cochromatography. The major adduct was identified as a product of the
reaction of an anti-DB[a,l]PDE with dAdo in DNA. DB[a,l]P induced
significant numbers of lung adenomas in a dose- dependent manner, with the
highest dose (6.0 mg/kg) yielding 16.1 adenomas/mouse. In
tricaprylin-treated control animals, there were 0.67 adenomas/mouse. Based
on the administered dose, DB[a,l]P was more active than other environmental
carcinogens including benzo[a]pyrene. As a function of time-integrated DNA
adduct levels, DB[a,l]P induced lung adenomas with about the same potency
as other PAHs, suggesting that the adducts formed by DB[a,l]P are similar
in carcinogenic potency to other PAHs in the strain A/J mouse lung model.
Analysis of the Ki- ras mutation spectrum in DB[a,l]P-induced lung tumors
revealed the predominant mutations to be G-->T transversions in the
first base of codon 12, A-->G transitions in the second base of codon
12, and A-->T transversions in the second or third base of codon 61,
concordant with the DNA adduct profile.
相似文献
22.
23.
OBJECTIVES: To study the efficacy of otoacoustic emissions (OAEs) as a screening test for hearing impairment in children with acute bacterial meningitis. Hearing tests were performed before discharge from the hospital in an attempt to improve coverage and avoid delays in the diagnosis of postmeningitic hearing loss. METHODS: Children with bacterial meningitis were recruited from 21 centers. In the 48 hours before discharge from the hospital, all patients underwent a thorough audiologic assessment consisting of transient evoked OAEs, auditory brainstem responses (ABRs), otoscopy, and tympanometry. Hearing loss was defined as ABR threshold >/=30 dB. The results of OAE screening were compared with the gold standard of ABR threshold. RESULTS: Of 124 children recruited, we were able to perform both OAEs and ABRs on 110 children. Seven (6.3%) of the 110 children had ABR threshold >/=30 dB; 2 had sensorineural hearing loss and 5 had conductive hearing loss. At follow-up, hearing loss persisted in both cases of sensorineural hearing loss and no new cases were identified. All 7 children with hearing loss failed the OAE screening test. Ninety-four children with normal hearing thresholds passed the test, and 9 failed. Thus, the screening test had a sensitivity of 1.00 (95% confidence interval, 0.59 to 1.00), a specificity of 0.91 (0.85 to 0.97), a positive predictive value of 0. 44 (0.20 to 0.70), and a negative predictive value of 1.00 (0.96 to 1.00). CONCLUSIONS: OAE screening in children recovering from meningitis was found to be feasible and effective. The test was highly sensitive and reasonably specific. Inpatient OAE screening should allow early diagnosis of postmeningitic hearing loss and prompt auditory rehabilitation. 相似文献
24.
25.
26.
Cutaneous manifestations of malignancy are not uncommon, especially in advanced disease. They may also occur early in malignant disease or they may even signify recurrence particularly if they are paraneoplastic in nature. Clinical diagnosis can be difficult because of the wide spectrum of appearance of these lesions, and, in many cases, because of the lack of an identifiable underlying primary. Presented here is the case of a 65-year-old woman with multiple inflammatory cutaneous metastases, which were sclerodermoid in nature. These appeared 14 months after initial diagnosis of adenocarcinoma of unknown primary (ACUP) and signified the beginning of a rapid deterioration in her condition. The coexistence of limited systemic sclerosis (scleroderma) and ACUP initially raised several interesting diagnostic possibilities. Adenocarcinoma of unknown primary and the sclerodermoid reaction in malignancy are discussed. 相似文献
27.
28.
The functional characterization of interleukin-10 receptor expression on human natural killer cells 总被引:11,自引:1,他引:11
Carson WE; Lindemann MJ; Baiocchi R; Linett M; Tan JC; Chou CC; Narula S; Caligiuri MA 《Blood》1995,85(12):3577-3585
Human natural killer (NK) cells are large granular lymphocytes that constitutively express functional forms of the interleukin-2 receptor (IL-2R) and lyse tumor and virally infected cells without prior sensitization. NK cells with high density expression of CD56 (CD56bright) express the high affinity IL-2R and proliferate in response to low (picomolar) concentrations of IL-2. CD56dim NK cells express the intermediate affinity IL-2R and demonstrate enhanced cytotoxic activity without proliferation in response to high (nanomolar) concentrations of IL-2. In the present study, we characterized IL-10R expression on human NK cells and the functional consequences of IL-10 binding directly to highly purified subsets of CD56bright and CD56dim NK cells. Binding studies using 125I-IL-10 indicated that resting human NK cells constitutively express the IL-10 receptor protein at a surface density of approximately 90 receptor sites per cell, with a kd of approximately 1 nmol/L. Alone, IL-10 did not induce proliferation of CD56bright or CD56dim NK cell subsets. However, at low concentrations (0.5 to 5 ng/mL), IL-10 significantly augmented IL-2-induced proliferation of the CD56bright NK cell subset mediated via the high-affinity IL-2R. In the absence of IL-2, IL-10 was able to induce significant NK cytotoxic activity against NK-resistant tumor cell targets in both subsets of NK cells in a dose-dependent fashion. Furthermore, the combination of IL-10 and IL-2 had an additive effect on NK cytotoxic activity, whereas that of IL-10 and IL-12 did not. Production of interferon-gamma, tumor necrosis factor-alpha, and granulocyte-macrophage colony-stimulating factor by IL-2-activated NK cells was also significantly enhanced by IL-10. Neither resting nor activated human NK cells appear to produce human IL-10 protein. In summary, NK cells constitutively express the IL-10R protein in low density, and the functional consequences of IL-10 binding directly to human NK cell subsets appear to be stimulatory and dose-dependent. In contrast to its direct effects on human T cells and monocytes/macrophages, IL-10 potentiates cytokine production by human NK cells. 相似文献
29.
30.
Ross AA; Cooper BW; Lazarus HM; Mackay W; Moss TJ; Ciobanu N; Tallman MS; Kennedy MJ; Davidson NE; Sweet D 《Blood》1993,82(9):2605-2610
Although peripheral blood stem cell collections (PBSC) are thought to have less tumor involvement than bone marrow (BM), the incidence of circulating tumor cells in patients with breast cancer has not been widely investigated. We prospectively investigated the incidence and viability of tumor cell involvement in PBSC and BM collections from breast cancer patients undergoing high-dose chemotherapy/hematopoietic stem cell transplantation. Paired samples of PBSC and BM from 48 patients were analyzed using an immunocytochemical technique that detects one epithelial-derived tumor cell per 5 x 10(5) mononuclear cells. Immunostained tumor cells were detected in 9.8% (13/133) PBSC specimens from 9/48 (18.7%) patients and in 62.3% (38/61) BM specimens from 32/48 (66.7%) patients, a significantly higher rate than in PBSC (P < .005). The geometric mean concentration of tumor cells in contaminated PBSC specimens was 0.8/10(5) mononuclear cells (range 0.33 to 2.0/10(5)) compared with 22.9/10(5) mononuclear cells in BM (range 1 to 3,000/10(5), P < .0001). In culture experiments, clonogenic tumor colonies grew in 21/26 immunocytochemically positive specimens. No tumor colony growth was detected in 30/32 immunocytochemically negative specimens. Immunocytochemical detection of tumor involvement in BM and PBSC correlated significantly with in vitro clonogenic growth (P < .0001). We conclude that PBSC contain fewer tumor cells than paired BM specimens from patients with advanced breast cancer and that these tumor cells appear to be capable of clonogenic growth in vitro. 相似文献