全文获取类型
收费全文 | 19973篇 |
免费 | 1422篇 |
国内免费 | 85篇 |
专业分类
耳鼻咽喉 | 186篇 |
儿科学 | 555篇 |
妇产科学 | 488篇 |
基础医学 | 2437篇 |
口腔科学 | 428篇 |
临床医学 | 2160篇 |
内科学 | 3824篇 |
皮肤病学 | 179篇 |
神经病学 | 2078篇 |
特种医学 | 668篇 |
外国民族医学 | 3篇 |
外科学 | 3315篇 |
综合类 | 245篇 |
一般理论 | 16篇 |
预防医学 | 1617篇 |
眼科学 | 473篇 |
药学 | 1524篇 |
中国医学 | 14篇 |
肿瘤学 | 1270篇 |
出版年
2023年 | 72篇 |
2022年 | 142篇 |
2021年 | 330篇 |
2020年 | 216篇 |
2019年 | 358篇 |
2018年 | 422篇 |
2017年 | 302篇 |
2016年 | 336篇 |
2015年 | 412篇 |
2014年 | 593篇 |
2013年 | 880篇 |
2012年 | 1355篇 |
2011年 | 1424篇 |
2010年 | 807篇 |
2009年 | 675篇 |
2008年 | 1349篇 |
2007年 | 1550篇 |
2006年 | 1317篇 |
2005年 | 1332篇 |
2004年 | 1386篇 |
2003年 | 1207篇 |
2002年 | 1196篇 |
2001年 | 202篇 |
2000年 | 156篇 |
1999年 | 208篇 |
1998年 | 268篇 |
1997年 | 234篇 |
1996年 | 184篇 |
1995年 | 152篇 |
1994年 | 146篇 |
1993年 | 146篇 |
1992年 | 145篇 |
1991年 | 127篇 |
1990年 | 116篇 |
1989年 | 104篇 |
1988年 | 87篇 |
1987年 | 98篇 |
1986年 | 91篇 |
1985年 | 78篇 |
1984年 | 92篇 |
1983年 | 95篇 |
1982年 | 95篇 |
1981年 | 99篇 |
1980年 | 82篇 |
1979年 | 70篇 |
1978年 | 70篇 |
1977年 | 57篇 |
1976年 | 66篇 |
1975年 | 64篇 |
1972年 | 54篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
951.
BACKGROUND: Two of the most widely used mouse strains for studying the behavioral effects of ethanol are C57BL/6J (B6) and DBA/2J (D2) mice. These strains exhibit marked differences in behavioral and physiological responses to ethanol. The subjective discriminative stimulus effects of ethanol may play a role in ethanol abuse, but the discriminative stimulus profile of ethanol has not been compared in B6 and D2 mice. Examination of the discriminative stimulus effects of ethanol in B6 and D2 mouse strains may enhance our understanding of the relationship between the subjective effects of ethanol and other ethanol-induced behavioral effects. METHODS: Twelve adult male C57BL/6J mice and 12 male DBA/2J mice were trained to discriminate 1.5 g/kg ethanol from saline in daily 15 min, milk-reinforced operant sessions. After training, ethanol substitution and response-rate suppression dose response curves were determined for ethanol, midazolam, diazepam, pentobarbital, pregnanolone, 4,5,6,7-Tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP), dizocilpine, and morphine. RESULTS: D2 mice learned the ethanol discrimination significantly more quickly than did B6 mice. Ethanol, midazolam, pregnanolone, and dizocilpine fully substituted for ethanol in both strains. Pentobarbital was more potent in producing ethanol-like discriminative stimulus effects in D2 than B6 mice. Midazolam and diazepam were significantly more potent in suppressing response rates in D2 than B6 mice. Morphine failed to substitute for ethanol in either strain, but the ED50 for morphine suppression of responding was significantly lower in B6 than D2 mice. CONCLUSIONS: The initial stimulus effects of 1.5 g/kg ethanol may be more salient in D2 than B6 mice. This does not appear to result from differences in the neurotransmitter systems that mediate ethanol's discriminative stimulus effects. In both strains, gamma-aminobutyric acid-positive modulators and a noncompetitive NMDA antagonist substituted for ethanol. However, strain differences did exist in the potency of gamma-aminobutyric acid-positive modulators and morphine for suppressing operant responding. 相似文献
952.
Goldberg SN Girnan GD Lukyanov AN Ahmed M Monsky WL Gazelle GS Huertas JC Stuart KE Jacobs T Torchillin VP Halpern EF Kruskal JB 《Radiology》2002,222(3):797-804
PURPOSE: To determine whether a combination of intravenous liposomal doxorubicin and radio-frequency (RF) ablation increases tumor destruction compared with RF alone in an animal tumor model. MATERIALS AND METHODS: R3230 mammary adenocarcinoma 1.4-1.8-cm- diameter nodules were implanted subcutaneously in 132 female Fischer rats. Initially, tumors were treated with (a) conventional, monopolar RF (mean, 250 mA +/- 25 [SD] at 70 degrees C +/- 1 for 5 minutes) ablation alone, (b) RF ablation followed by intravenous administration of 1 mg of liposomal doxorubicin, (c) RF ablation followed by intravenous administration of 1 mg of empty liposomes, (d) RF ablation and direct intratumoral administration of liposomal doxorubicin, or (e) no treatment. Subsequently, the dose (0.06-2.00 mg) of liposomal doxorubicin, the timing of administration (3 days before to 3 days after RF ablation), and the time of pathologic examination (0-72 hours after treatment) were varied. RESULTS: Mean coagulation diameter for treated tumors follows: 6.7 mm +/- 0.6, RF ablation alone; 11.1 mm +/- 1.5, RF ablation and intravenous administration of empty liposomes (P <.05, compared with RF ablation alone); and 8.4 mm +/- 1.1, RF ablation with intratumoral administration of liposomal doxorubicin (P <.05, compared with RF ablation alone). Maximal increased mean coagulation diameter (13.1 mm +/- 1.5) was observed with a combination of liposomal doxorubicin and RF ablation (P <.001, for all comparisons). The increased coagulation for combination therapy developed over 48 hours after therapy. Coagulation diameter did not vary with the doxorubicin concentration range and was not dependent on the timing of administration of liposomal doxorubicin from 3 days before to 24 hours after RF ablation. CONCLUSION: Intravenous administration of liposomal doxorubicin can improve RF ablation, since it increases coagulation diameter in solid tumors compared with RF ablation alone or a combination of RF ablation with administration of empty liposomes. 相似文献
953.
Emerging patterns of diffusion-weighted MR imaging in Creutzfeldt-Jakob disease: case report and review of the literature 总被引:6,自引:0,他引:6
Mao-Draayer Y Braff SP Nagle KJ Pendlebury W Penar PL Shapiro RE 《AJNR. American journal of neuroradiology》2002,23(4):550-556
We report the use of diffusion-weighted MR imaging in the early diagnosis and monitoring of the progression of a histopathologically proved case of sporadic Creutzfeldt-Jakob disease. Ribbon-like areas of hyperintensity in the cerebral cortex on diffusion-weighted images corresponded to the localization of periodic sharp-wave complexes on the electroencephalogram. 相似文献
954.
HVI and HVII mitochondrial DNA data in Apaches and Navajos 总被引:4,自引:4,他引:0
Budowle B Allard MW Fisher CL Isenberg AR Monson KL Stewart JE Wilson MR Miller KW 《International journal of legal medicine》2002,116(4):212-215
Most mtDNA studies on Native Americans have concentrated on hypervariable region I (HVI) sequence data. Mitochondrial DNA haplotype data from hypervariable regions I and II (HVI and HVII) have been compiled from Apaches (N=180) and Navajos (N=146). The inclusion of HVII data increases the amount of information that can be obtained from low diversity population groups. Less mtDNA variation was observed in the Apaches and Navajos than in major population groups. The majority of the mtDNA sequences were observed more than once; only 17.8% (32/180) of the Apache sequences and 25.8% of the Navajo sequences were observed once. Most of the haplotypes in Apaches and Navajos fall into the A and B haplogroups. Although a limited number of haplogroups were observed, both sample populations exhibit sufficient variation for forensic mtDNA typing. Genetic diversity was 0.930 in the Apache sample and 0.963 in the Navajo sample. The random match probability was 7.48% in the Apache sample and 4.40% in the Navajo sample. The average number of nucleotide differences between individuals in a database is 9.0 in the Navajo sample and 7.7 in the Apache sample. The data demonstrate that mtDNA sequencing can be informative in forensic cases where Native American population data are used. 相似文献
955.
956.
957.
BACKGROUND: Short course neoadjuvant radiation has been shown to provide improved local control of rectal cancer in a clinical trial population even in the presence of standardized surgical techniques. However, this use of hypofractionated radiotherapy has been limited in North America owing to concerns over toxicity.METHODS: Patients considered to have locally advanced rectal carcinoma received a radiation dose of 25 Gy given in five fractions to the posterior pelvis. Definitive surgery was then performed within 2 weeks. Retrospective analysis was performed. RESULTS: Sixty-three patients, of whom 60 were assessable, were treated with preoperative short course radiotherapy at the British Columbia Cancer Agency between 1991 and 1998, and 97% proceeded to R0 resection. Local recurrence developed in 3 patients (5%). Five-year actuarial overall and relapse-free survival rates for the group were 71% and 69%, respectively. The actuarial rates of relapse-free survival by stage at 5 years were stage 1 83%, stage II 75%, stage III 62%, and stage 4 0%. Eleven patients (18%) experienced a postoperative complication.CONCLUSION: Short course preoperative radiotherapy for operable rectal cancer can be delivered to a general population and produce high pelvic control rates with acceptable toxicity. 相似文献
958.
Traynor JP Simpson K Geddes CC Deighan CJ Fox JG 《Journal of the American Society of Nephrology : JASN》2002,13(8):2125-2132
There is a trend to start dialysis earlier in patients with chronic renal failure. Studies that suggest improved survival from earlier initiation of dialysis are flawed in that they have measured survival from start of dialysis rather than from a time point before dialysis, when patients have the same renal function. This flaw is termed lead-time bias. Using the electronic patient record at the renal unit of Glasgow Royal Infirmary, all patients were identified who had received dialysis for chronic renal failure and who had sufficient data to calculate the time point at which they reached an estimated creatinine clearance (eC(Cr)) of 20 ml/min (n = 275). This date was used to time survival. The patients were divided into early and late start groups by the median eC(Cr) for all patients at initiation of dialysis, which was 8.3 ml/min. There was no significant benefit in patient survival from earlier initiation of dialysis. A Cox proportional hazards model demonstrated a significant inverse relationship between eC(Cr) at start of dialysis and survival (hazard ratio, 1.1; P = 0.02), i.e., patients who started dialysis with a lower eC(Cr) tended to survive longer. This relationship retained significance when gender, age, weight, presence of diabetes, mode of first dialysis, initial dialysis access, hemoglobin, serum albumin, blood leukocyte count, Wright/Khan index, and eC(Cr) at the start of dialysis were taken into account. This study fails to support a policy of earlier initiation of dialysis for patients with end-stage renal failure. 相似文献
959.
Recruitment of anterior dorsolateral prefrontal cortex in human reasoning: a parametric study of relational complexity 总被引:4,自引:3,他引:1
Kroger JK Sabb FW Fales CL Bookheimer SY Cohen MS Holyoak KJ 《Cerebral cortex (New York, N.Y. : 1991)》2002,12(5):477-485
Reasoning and problem solving depend on the ability to represent and integrate complex relationships among stimuli. For example, deciding whether an animal is dangerous requires integrating information about the type of animal, its size, its distance from oneself, and one's proximity to shelter. Relational complexity increases with the number of such interdependent elements that must be simultaneously considered to solve a problem. We used functional magnetic resonance imaging to identify brain regions that respond selectively in processing high levels of relational complexity. Performance on nonverbal reasoning problems in which relational complexity was varied parametrically was compared with performance on control problems in which relational complexity was held constant while difficulty was manipulated by adding distractor forms to the problems. Increasing complexity and adding distractors both led to increased activation in parietal and in dorsolateral prefrontal cortex, with high levels of relational complexity selectively activating anterior left prefrontal cortex. Our data provide evidence that brain regions specific to integrating complex relations among stimuli are distinct from those involved in coping with general task difficulty and with working-memory demands. 相似文献
960.
Polk HC Bowden TA Rikkers LF Balch CM Organ CH Murie JA Pories WJ Buechler MW Neoptolemos JP Fazio VW Schwartz SI Cameron JI Kelly KA Grosfeld JL McFadden DW Souba WW Pruitt BA Johnston KW Rutherford RB Arregui ME Scott-Conner CE Warshaw AL Sarr MG Cuschieri A Tompkins RK MacFadyen BV 《Annals of surgical oncology》2002,9(5):421-422