全文获取类型
收费全文 | 8614篇 |
免费 | 585篇 |
国内免费 | 89篇 |
专业分类
耳鼻咽喉 | 105篇 |
儿科学 | 295篇 |
妇产科学 | 291篇 |
基础医学 | 929篇 |
口腔科学 | 159篇 |
临床医学 | 928篇 |
内科学 | 1862篇 |
皮肤病学 | 215篇 |
神经病学 | 860篇 |
特种医学 | 227篇 |
外科学 | 1403篇 |
综合类 | 166篇 |
一般理论 | 3篇 |
预防医学 | 421篇 |
眼科学 | 136篇 |
药学 | 642篇 |
中国医学 | 70篇 |
肿瘤学 | 576篇 |
出版年
2023年 | 43篇 |
2022年 | 101篇 |
2021年 | 218篇 |
2020年 | 105篇 |
2019年 | 196篇 |
2018年 | 233篇 |
2017年 | 165篇 |
2016年 | 186篇 |
2015年 | 253篇 |
2014年 | 312篇 |
2013年 | 433篇 |
2012年 | 559篇 |
2011年 | 624篇 |
2010年 | 376篇 |
2009年 | 354篇 |
2008年 | 518篇 |
2007年 | 504篇 |
2006年 | 520篇 |
2005年 | 460篇 |
2004年 | 446篇 |
2003年 | 326篇 |
2002年 | 309篇 |
2001年 | 275篇 |
2000年 | 216篇 |
1999年 | 217篇 |
1998年 | 59篇 |
1997年 | 60篇 |
1996年 | 54篇 |
1995年 | 33篇 |
1994年 | 45篇 |
1993年 | 44篇 |
1992年 | 100篇 |
1991年 | 102篇 |
1990年 | 104篇 |
1989年 | 97篇 |
1988年 | 80篇 |
1987年 | 71篇 |
1986年 | 58篇 |
1985年 | 56篇 |
1984年 | 54篇 |
1983年 | 37篇 |
1982年 | 16篇 |
1981年 | 25篇 |
1980年 | 20篇 |
1979年 | 40篇 |
1978年 | 23篇 |
1977年 | 20篇 |
1976年 | 23篇 |
1975年 | 19篇 |
1974年 | 23篇 |
排序方式: 共有9288条查询结果,搜索用时 0 毫秒
81.
Lai Fong Chiu Philip Heywood Joanne Jordan Patricia McKinney Tony Dowell 《Critical public health》1999,9(1):5-22
Studies of minority ethnic women and cancer screening have, in the past, suffered from many theoretical and methodological weaknesses. In addition, no attempts have been made to study the complexity of the issue involved in the intercultural context, or the possible contribution of women's experiences to low uptake rates. In order to further our understanding of the issues, an alternative approach, participatory action research (PAR), was adopted to identify factors that might have contributed to the persistently low participation of minority ethnic women in the cervical screening programme, and address them collaboratively. This paper presents the key findings of the ‘problem identification' phase of the project. Using mainly the focus-group method, it explores both smear takers' and minority ethnic women's perceptions and experiences of cervical screening. Data suggest that there was a divergence in perceptions held by these groups regarding cervical screening, which contributed to negative experiences for both groups. There is also clear evidence of dysfunctional clinical communication arising from these differing perceptions. Opportunistic screening at post-natal examination adopted by many general practices appeared to have perpetuated the perceptions that the majority of minority ethnic women held about the purpose of the smear test. Compounded by language differences, the majority of women who had undergone smear testing understood neither the purpose of screening programme nor the procedure of the test. This has clear implications for promoting regular uptake, and more importantly for informed consent and choice. 相似文献
82.
Nagarathnam D Miao SW Lagu B Chiu G Fang J Murali Dhar TG Zhang J Tyagarajan S Marzabadi MR Zhang F Wong WC Sun W Tian D Wetzel JM Forray C Chang RS Broten TP Ransom RW Schorn TW Chen TB O'Malley S Kling P Schneck K Bendesky R Harrell CM 《Journal of medicinal chemistry》1999,42(23):4764-4777
Dihydropyrimidinones such as compound 12 exhibited high binding affinity and subtype selectivity for the cloned human alpha(1a) receptor. Systematic modifications of 12 led to identification of highly potent and subtype-selective compounds such as (+)-30 and (+)-103, with high binding affinity (K(i) = 0.2 nM) for alpha(1a) receptor and greater than 1500-fold selectivity over alpha(1b) and alpha(1d) adrenoceptors. The compounds were found to be functional antagonists in human, rat, and dog prostate tissues. Compound (+)-103 exhibited excellent selectively to inhibit intraurethral pressure (IUP) as compared to lowering diastolic blood pressure (DBP) in mongrel dogs (K(b)(DBP)/K(b)(IUP) = 40) suggesting uroselectivity for alpha(1a)-selective compounds. 相似文献
83.
Acute catatonic syndromes occurring in the context of various medical and neuropsychiatric conditions, including schizophrenia,
have been shown to respond well to benzodiazepines (BZD). However, there have been no studies specifically designed to address
the BZD treatment response of persistent catatonic states. Eighteen patients with clinically stable chronic schizophrenia,
who also displayed enduring catatonic features, underwent a 12-week long, random assignment, double-blind, placebo-controlled
cross-over trial with lorazepam (6 mg/day). A comprehensive assessment, including the subjects’ clinical and motor (catatonic
as well as drug-induced movement disorders) condition, was performed at baseline and four weekly intervals thereafter. Pre-existing
medication was kept constant throughout the study. Lorazepam had no effect on the subjects’catatonic signs and symptoms, suggesting
that acute and chronic catatonic syndromes associated with schizophrenic illness might have a different neurobiological basis.
Received: 25 May 1998/Final version: 22 September 1998 相似文献
84.
Mechanism of activation of an N-ras oncogene of SW-1271 human lung carcinoma cells. 总被引:15,自引:8,他引:7
下载免费PDF全文
![点击此处可从《Proceedings of the National Academy of Sciences of the United States of America》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Y Yuasa R A Gol A Chang I M Chiu E P Reddy S R Tronick S A Aaronson 《Proceedings of the National Academy of Sciences of the United States of America》1984,81(12):3670-3674
An N-ras-related transforming gene was detected in the human lung carcinoma cell line SW-1271 and molecularly cloned. The lesion responsible for its acquisition of transforming activity was localized to a single nucleotide transition from A to G in codon 61 of the predicted protein. This lesion in the second exon results in the substitution of arginine for glutamine at this position. These findings, together with previous studies, indicate that the activation of ras oncogenes in human tumors is most commonly due to point mutations at one of two major "hot spots" in the ras coding sequence. 相似文献
85.
The handedness of seventy-five persons without evidence of neurological disease, was assessed with a standardised test. An analysis of the CT scans of the same persons was performed to determine (1) presence and lateralisation of frontal and occipital "petalia," (2) width of frontal and occipital lobes of each hemisphere, (3) direction of straight sinus deviation. Results suggest that handedness and cerebral asymmetries are independent variables. There were no significant differences between right-handers and non-right-handers. Also there were no significant differences between strongly left-handed and ambidextrous individuals, nor were there differences between right-handers with or without family history of left-handedness. Irrespective of handedness, left occipital "petalia" was more common than right (p < 0.01), right frontal petalia was more common than left (p < 0.01), and straight sinus deviation was more commonly toward the right. The study does not support the concept that cerebral "symmetry" or "reverse asymmetry" are associated with left-handedness or ambidexterity. The noted asymmetries are more likely to be direct correlates of cerebral language dominance, than of handedness. Furthermore, the possibility that outside forces acting on the bone contributes to the asymmetries cannot be excluded. CT scan may be of value as a direct predictor of cerebral dominance. 相似文献
86.
Two cannabinoids, 9 and cannabidiol, and several reference drugs were compared relative to their effects in a recently developed anticonvulsant test system, the after-discharge potentials of the visually evoked response; the potentials were recorded electrophysiologically from electrodes permanently mounted over the visual cortices of conscious rats. In anticonvulsant doses, trimethadione and ethosuximide produced an extensive depression of after-discharge activity, whereas diphenylhydantoin and cannabidiol exerted no such effect. In contrast, anticonvulsant doses of 9 and subconvulsant doses of pentylenetetrazol markedly increased after-discharge activity, which may represent a manifestation of their central nervous system excitatory properties. The data from the present study support our previously published observations from several other anticonvulsant tests that indicate the anticonvulsant characteristics of cannabidiol resemble those of diphenylhydantoin rather than those of trimethadione and that the central excitatory properties of 9 distinguish it from cannabidiol. The results consistently suggest that the cannabinoids will be effective against grand mal but not absence seizures. 相似文献
87.
STUDY DESIGN: This is a feasibility study of image-guided surgery for C1-C2 transarticular screw fixation comparing postoperative screw position in a nonrandomized prospective cohort with a historic control group in which fluoroscopic guidance was used alone. OBJECTIVES: To evaluate the potential benefits and disadvantages of image-guided surgery for C1-C2 screw placement. SUMMARY OF BACKGROUND DATA: C1-C2 transarticular screw fixation is biomechanically superior to other current surgical stabilization procedures. The original technique for C1-C2 screw placement relies on anatomic landmarks and intraoperative fluoroscopy. Screw misplacement or anatomic variations can result in vertebral artery injury. Image-guided surgery involves using computed tomography (CT) data to plan the optimal screw trajectory before surgery and then use this data to guide screw placement during the actual surgery. Promising results of this technique are reported in the literature, but no direct comparison between image-guided surgery and conventional surgical techniques has been previously reported. METHODS: The image-guided surgery group consisted of 37 prospective patients. The historic control group included 78 patients who had similar surgeries performed using only fluoroscopic guidance. For the image-guided surgery group, subluxation was reduced by positioning at the time of CT examination. The CT data were transferred to a StealthStation (Sofamor-Danek, Memphis, TN) surgical planning and guidance computer system, and an optimal screw trajectory was determined for the right and left transarticular screws. After matching the surgical field to the virtual computer field, C2 was drilled according to the planned screw trajectory, and screws were placed. Plain radiographs and CT were used for postoperative evaluation of the image-guided surgery group. RESULTS: Image-guided surgery reduced but did not eliminate the risk of screw misplacement. Surgical time was not increased overall. CONCLUSIONS: Image-guided surgery is an effective tool for the achievement of correct screw placement in C1-C2 transarticular screw fixation procedures. The procedure remains technically demanding. 相似文献
88.
Maria G Beconi Ann Mao David Q Liu Christopher Kochansky Tony Pereira Conrad Raab Paul Pearson Shuet-Hing Lee Chiu 《Drug metabolism and disposition》2003,31(10):1269-1277
The pharmacokinetics and metabolism of the l-threo isoleucine thiazolidide dipeptidyl peptidase IV inhibitor, di-[2S,3S]-2-amino-3-methyl-pentanoic-1,3-thiazolidine fumarate (ILT-threo) and its allo stereoisomer (ILT-allo) were evaluated in rats, dogs, and monkeys. Both compounds were well absorbed (>80%) in all species, and most of the dose (>60%) was recovered in urine. Metabolites identified in all species included a sulfoxide (M1), a sulfone (M2), and a carbamoyl glucuronide (M3). For both compounds, parent drug had moderate systemic clearance in rats and dogs ( approximately 20-35 ml/min/kg in both species) and lower clearance in monkeys ( approximately 6-9 ml/min/kg). In rats, M1 was present in systemic circulation in concentrations similar to that of parent drug, whereas in dogs and monkeys, exposures to M1 were higher than for parent drug. In dogs, exposures to the sulfoxide metabolite were approximately 2 to 3 times higher after administration of ILT-allo than after administration of ILT-threo. Carbamoyl glucuronidation was an important biotransformation pathway in dogs. Circulating levels of M3 were significant in the dog, and present only in trace levels in rats and monkeys. M3 could be produced in in vitro systems in a NaHCO3 buffer under a CO2-saturated atmosphere and in the presence of UDP-glucuronic acid and alamethicin. 相似文献
89.
Anthony T C Chan Brigette B Y Ma Y M Dennis Lo S F Leung W H Kwan Edwin P Hui Tony S K Mok Michael Kam Lisa S Chan Samuel K W Chiu K H Yu K Y Cheung Karen Lai Maria Lai Frankie Mo Winnie Yeo Ann King Philip J Johnson Peter M L Teo Benny Zee 《Journal of clinical oncology》2004,22(15):3053-3060
PURPOSE: To assess the efficacy of neoadjuvant paclitaxel and carboplatin (TC) followed by concurrent cisplatin and radiotherapy (RT) in patients with locoregionally advanced nasopharyngeal carcinoma (NPC) and to monitor treatment response with plasma Epstein-Barr virus (EBV) DNA. PATIENTS AND METHODS: Thirty-one patients with International Union Against Cancer stages III and IV undifferentiated NPC had two cycles of paclitaxel (70 mg/m2 on days 1, 8, and 15) and carboplatin (area under the curve 6 mg/mL/min on day 1) on a 3-weekly cycle, followed by 6 to 8 weeks of cisplatin (40 mg/m2 weekly) and RT at 66 Gy in 2-Gy fractions. Plasma EBV DNA was measured serially using the real-time quantitative polymerase chain reaction method. Results All patients completed planned treatment. Response to neoadjuvant TC was as follows: 12 patients (39%) achieved partial response (PR) and 18 achieved (58%) complete response (CR) in regional nodes; five patients (16%) achieved PR and no patients achieved CR in nasopharynx. At 6 weeks after RT, one patient (3%) achieved PR and 30 patients (97%) achieved CR in regional nodes, and 31 patients (100%) achieved CR in nasopharynx; 29 patients (93%) had EBV DNA level of less than 500 copies/mL. Neoadjuvant TC was well tolerated, and the most common acute toxicity of cisplatin plus RT was grade 3 mucositis (55%). At median follow-up of 33.7 months (range, 7 to 39.3 months), six distant and three locoregional failures occurred. Plasma EBV DNA level increased significantly in eight of nine patients who experienced treatment failure but did not increase in those who did not. The 2-year overall and progression-free survival rates were 91.8% and 78.5%, respectively. CONCLUSION This strategy was feasible and resulted in excellent local tumor control. Serial plasma EBV DNA provides a noninvasive method of monitoring response in NPC. 相似文献
90.
Nm23 protein expression was analyzed by immunohistochemical staining using formalin-fixed, paraffin-embedded sections from 39 cases with osteosarcomas and compared with the histologic findings and early metastasis for the purpose of detecting nm23 expression in osteosarcoma and elucidating the clinical significance of its expression. Immunoreactivity of nm23 protein was detected in 48.7% of the total cases. There was no statistical difference between nm23 expression and early metastasis, but there was a trend for cases with nm23 expression to progress to early metastasis within 1 year after operation. The role of nm23 as a tumor metastasis suppressor in osteosarcomas appeared less prominent. 相似文献