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   2838篇
  免费   190篇
  国内免费   10篇
耳鼻咽喉   10篇
儿科学   69篇
妇产科学   20篇
基础医学   600篇
口腔科学   85篇
临床医学   244篇
内科学   563篇
皮肤病学   21篇
神经病学   358篇
特种医学   144篇
外科学   274篇
综合类   21篇
一般理论   2篇
预防医学   239篇
眼科学   72篇
药学   136篇
  1篇
中国医学   5篇
肿瘤学   174篇
  2022年   26篇
  2021年   36篇
  2020年   30篇
  2019年   35篇
  2018年   46篇
  2017年   42篇
  2016年   52篇
  2015年   54篇
  2014年   74篇
  2013年   111篇
  2012年   165篇
  2011年   175篇
  2010年   103篇
  2009年   106篇
  2008年   148篇
  2007年   151篇
  2006年   148篇
  2005年   131篇
  2004年   124篇
  2003年   125篇
  2002年   128篇
  2001年   55篇
  2000年   70篇
  1999年   64篇
  1998年   44篇
  1997年   52篇
  1996年   44篇
  1995年   35篇
  1994年   37篇
  1993年   24篇
  1992年   33篇
  1991年   48篇
  1990年   29篇
  1989年   33篇
  1988年   44篇
  1987年   37篇
  1986年   27篇
  1985年   26篇
  1984年   28篇
  1983年   18篇
  1982年   18篇
  1981年   24篇
  1980年   17篇
  1979年   29篇
  1978年   14篇
  1977年   17篇
  1976年   11篇
  1974年   12篇
  1973年   11篇
  1969年   11篇
排序方式: 共有3038条查询结果,搜索用时 31 毫秒
51.
The development of a specific and sensitive immunologic ELISA detection system for methylphosphonoflouridic acid. 1,2,2-trimethylpropylester (soman) by the use of monoclonal antibodies (MAbs) is described. The monoclonal antibodies F71D7, F71H10, F71B12 and F71H9 originally produced against the soman derivative methyl phosphonic acid,p-aminophenyl 1,2,2-trimethylpropyldiester (MATP) also reacted with soman in a previously developed, direct competitive ELISA. After optimizing the ELISA system by varying the reaction mixture and the solvents for the organophosphate, 5.0×10–7 mol/l soman (80% purity), e.g. 2.5 ng or 2 ng pure soman per 25 l test buffer, could be detected after a total test duration of 40 min. A shortening of the incubation time to 10 min resulted in a drop of sensitivity to 1.8×10–6 mol/l soman. Various alcohols which may be used as extraction media for soman from various materials (isopropanol, ethanol and methanol) were shown to inhibit peroxidase activity and thereby reduce the sensitivity of the test. However, the influence of alcohols decreased with the shortening of incubation time. All monoclonal antibodies showed little cross reactivity to sarin and no cross reactivity to tabun and VX. Judging on the reactivity of the MAbs with MATP and soman oxidazed by 1,2-dihydrobenzol, some reactivity with some other (non-toxic) soman analogues containing the same pinacolyl group can be expected. There was no evidence for stereoselectivity of the MAbs tested. Finally, soman could be detected in different biological samples like human serum, goat serum, rabbit serum, chicken serum, milk, and tap water in concentrations between 1.3×10–6 and 2.0×10–6 mol/l.  相似文献   
52.
A retrospective evaluation of 68 Fallopian tube carcinomas (FTC) of a period of ten years (1980-1990) in stage I and II was performed. The aim of this study was to evaluate the prognostic impact of various factors. 68 cases were investigated for the prognostic influence of mitotic activity, degree of nuclear anaplasia and inflammatory reaction. Histological grading (p=0.08), and inflammatory reaction (p=0.003) showed to have a prognostic impact for survival in univariate analysis. Whereas, mitotic activity did not show any statistically significant influence. 47 (69%) tissue samples showed a positive inflammatory reaction which correlated with a significantly better outcome compared with tumors without this feature. However, this influence was proved in multivariate analysis for inflammatory reaction only (p=0.01). Although no data on the influence of the inflammatory reaction on prognosis in FTC has been published up to now, we can state that the determination of this factor can be useful for prognosis in this rare but highly aggressive tumor.  相似文献   
53.
Corticostriatal and thalamostriatal projection systems have been shown to utilize glutamate as a neurotransmitter in mammals and birds. Although corticostriatal and thalamostriatal projection systems have been demonstrated in turtles, it is uncertain whether they too use glutamate as their neurotransmitter. Immunohistochemical localization of glutamate and of NMDA- and AMPA-type ionotropic glutamate receptor subunits (NMDAR2A/B, GluR1, GluR2/3, and GluR4) were used to address this issue. Numerous medium-sized neurons that were rich in NMDAR2A/B and GluR2/3 were observed in the striatal part of the basal ganglia of red-eared turtles. Smaller numbers of medium-sized neurons and some large neurons rich in the GluR1 and GluR4 subunits were also observed in the striatum. The striatal neuropil was notably rich in GluR1, GluR2/3 and NMDAR2A/B subunits. The pallidal region was specifically rich in large neurons possessing GluR4 subunits. Consistent with the glutamate receptors on striatal and pallidal neurons, sources of input to the striatum and pallidum in turtle such as the dorsomedial and dorsolateral thalamic nuclei (which appear to correspond to intralaminar thalamic nuclei), telencephalic pallial cell groups, and the apparent subthalamic nucleus homologue were rich in glutamatergic neurons. The results show that the thalamostriatal, corticostriatal and subthalamo-pallidal projection systems of turtles are glutamatergic and that similar basal ganglia cell types in turtles and mammals have largely similar glutamate receptor characteristics. Copyright (R) 2000 S.Karger AG, Basel  相似文献   
54.
Vrbanec D  Reiner Z  Belev B  Plestina S 《Tumori》1998,84(6):687-690
Tamoxifen has been used for a long time as an adjuvant hormonal treatment in breast cancer patients. We studied 62 newly diagnosed postmenopausal women, aged 50-79 years, with node-positive breast cancer and receiving adjuvant tamoxifen (20 mg per day). Total serum cholesterol, triglycerides, HDL-cholesterol, LDL-cholesterol, VLDL-cholesterol, apo AI, apo AII, apo B and Lp(a) were determined before the surgery and 3, 6, 9, 12 and 24 months after starting tamoxifen treatment. Tamoxifen significantly reduced total serum cholesterol (6.13+/-1.20 mmol/L vs 5.21+/-1.05 mmol/L) (P <0.01), LDL-cholesterol (3.72+/-0.70 mmol/L vs 2.93+/-0.51) (P <0.01) and Lp(a) (0.11+/-0.07 g/L vs 0.02+/-0.01 g/L) (P < 0.01). There were no changes in triglycerides or HDL-cholesterol serum levels during tamoxifen treatment. The results indicate that an additional beneficial effect of adjuvant tamoxifen therapy may be that it decreases cardiovascular risk in such patients.  相似文献   
55.
56.
By means of a new optical device developed by Reiner, an "optical implantation" of 6 different bi- and multifocal intraocular lenses (MIOLs) was performed in 20 young healthy subjects, and results were compared with those of a monofocal reference IOL. The following parameters were investigated: distance and near visual acuity, depth of focus and contrast sensitivity. The median of distance visual acuity was 1.0 in all IOLs with the exception of a 7-zone refractive MIOL (0.75). Near acuity without near addition was 1.0 in all MIOL models; through focus curves of all MIOLs showed an increase in depth of focus with a typical two peak course. Contrast sensitivity at high contrasts was reduced for the 7-zone-model, but contrast sensitivity at low contrasts was significantly reduced for all MIOLs, except the 2- and 3-zone refractive models.  相似文献   
57.
PURPOSE: Intestinal non-Hodgkin's lymphomas are not well characterized. We therefore studied prospectively their clinical features and response to standardized therapy. PATIENTS AND METHODS: Fifty-six patients with primary intestinal lymphoma were included in a prospective, nonrandomized multicenter study. Lymphoma resection was recommended and staging was performed according to the Ann Arbor classification. Patients were scheduled to receive six cycles of cyclophosphamide, doxorubicin, vincristine, and prednisolone (CHOP) chemotherapy, and at stages EIII to EIV, they received additional involved-field radiotherapy. Corticosteroids were used in patients who could not receive chemotherapy. RESULTS: Thirty-five patients had intestinal T-cell lymphoma (ITCL), 21 patients had intestinal B-cell lymphoma (IBCL; 18 diffuse large-cell lymphomas, two marginal-cell lymphomas, and one follicle-center lymphoma). Thirty-four patients at stages EI to EII (14 ITCL and 20 IBCL) and nine patients at stages EIII to EIV (all ITCL) received chemotherapy. No patient in stages EIII to EIV received radiotherapy, because death occurred in 12 of 14 patients. Two-year cumulative survival in patients with IBCL was 94% (95% CI, 82% to 100%) and higher than in patients with ITCL (28% [95% CI, 13% to 43%]; P <.0001), even when only stages EI to EII were considered (ITCL, 37.5% [95% CI, 16.5% to 58.5%]; P <.0001). IBCL patients compared with ITCL patients were at lower lymphoma stages (P <.01), had higher Karnofsky status (P <.005), had intestinal perforation less often (P <.05), required emergency operation less often (P <.05), received CHOP (P <.05) more often, and reached complete remission (P <.0005) more frequently. CONCLUSION: IBCL patients at stages EI and EII respond well to chemotherapy, but the prognosis and treatment of ITCL patients is unsatisfactory.  相似文献   
58.
OBJECTIVE: To determine nosocomial transmission of respiratory syncytial virus (RSV) in Canadian pediatric hospitals, outcomes associated with nosocomial disease, and infection control practices. DESIGN: A prospective cohort study in the 1992 to 1994 winter respiratory seasons. SETTING: Nine Canadian pediatric university-affiliated hospitals. PARTICIPANTS: Hospitalized children with symptoms of lower respiratory tract infection (at least one of cough, wheezing, dyspnea, tachypnea, and apnea) and RSV antigen identified in a nasopharyngeal aspirate. RESULTS: Of 1516 children, 91 (6%) had nosocomial RSV (NRSV), defined as symptoms of lower respiratory tract infection and RSV antigen beginning >72 hours after admission. The nosocomial ratio (NRSV/[com-munity-acquired RSV {CARSV})] + NRSV) varied by site from 2.8% to 13%. The median length of stay attributable to RSV for community-acquired illness was 5 days, but 10 days for nosocomial illness. Four children with NRSV (4. 4%) died within 2 weeks of infection, compared with 6 (0.42%) with CARSV (relative risk = 10.4, 95% confidence interval: 3.0, 36.4). All sites isolated RSV-positive patients in single rooms or cohorted them. In a multivariate model, no particular isolation policy was associated with decreased nosocomial ratio, but gowning to enter the room was associated with increased risk of RSV transmission (incidence rate ratio 2.81; confidence interval: 1.65, 4.77). CONCLUSIONS: RSV transmission risk in Canadian pediatric hospitals is generally low. Although use of barrier methods varies, all sites cohort or isolate RSV-positive patients in single rooms. Children with risk factors for severe disease who acquire infection nosocomially have prolonged stays and excess mortality.  相似文献   
59.
Endometrial carcinoma (EnCa) is the most common invasive gynaecologic carcinoma. Over 85% of EnCa are classified as endometrioid, expressing steroid hormone receptors and mostly involving pathological prestages. Human endogenous retroviruses (ERV) are chromosomally integrated genes, account for about 8% of the human genome and are implicated in the etiology of carcinomas. The majority of ERV envelope (env) coding genes are either not present or not consistently represented between common gene expression microarrays. The aim of this study was to analyse the absolute gene expression of all known 21 ERV env genes including 19 codogenic and two env genes with premature stop codons in EnCa, endometrium as well as in hyperplasia and polyps. For EnCa seven env genes had high expression with >200 mol/ng cDNA (e.g. envH1-3, Syncytin-1, envT), two middle >50 mol/ng cDNA (envFc2, erv-3) and 12 low <50 mol/ng cDNA (e.g. Syncytin-2, envV2). Regarding tumor parameters, Syncytin-1 and Syncytin-2 were significantly over-expressed in advanced stage pT2 compared to pT1b. In less differentiated EnCa Syncytin-1, erv-3, envT and envFc2 were significantly over-expressed. Syncytin-1, Syncytin-2 and erv-3 were specific to glandular epithelial cells of polyps, hyperplasia and EnCa using immunohistochemistry. An analysis of 10 patient-matched EnCa with endometrium revealed that the ERV-W 5'' long terminal repeat regulating Syncytin-1 was hypomethylated, including the ERE and CRE overlapping MeCP2 sites. Functional analyses showed that 10 env genes were regulated by methylation in EnCa using the RL95-2 cell line. In conclusion, over-expressed env genes could serve as indicators for pathological pre-stages and EnCa.  相似文献   
60.
Conventional peer review practice is compromised by a number of well-documented biases, which in turn limit standard of care analysis, which is fundamental to determination of medical malpractice. In addition to these intrinsic biases, other existing deficiencies exist in current peer review including the lack of standardization, objectivity, retrospective practice, and automation. An alternative model to address these deficiencies would be one which is completely blinded to the peer reviewer, requires independent reporting from both parties, utilizes automated data mining techniques for neutral and objective report analysis, and provides data reconciliation for resolution of finding-specific report differences. If properly implemented, this peer review model could result in creation of a standardized referenceable peer review database which could further assist in customizable education, technology refinement, and implementation of real-time context and user-specific decision support.  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