全文获取类型
收费全文 | 4491篇 |
免费 | 251篇 |
国内免费 | 125篇 |
专业分类
耳鼻咽喉 | 53篇 |
儿科学 | 143篇 |
妇产科学 | 92篇 |
基础医学 | 471篇 |
口腔科学 | 80篇 |
临床医学 | 414篇 |
内科学 | 1176篇 |
皮肤病学 | 65篇 |
神经病学 | 329篇 |
特种医学 | 248篇 |
外科学 | 561篇 |
综合类 | 67篇 |
一般理论 | 3篇 |
预防医学 | 213篇 |
眼科学 | 40篇 |
药学 | 290篇 |
中国医学 | 12篇 |
肿瘤学 | 610篇 |
出版年
2023年 | 31篇 |
2022年 | 54篇 |
2021年 | 81篇 |
2020年 | 60篇 |
2019年 | 72篇 |
2018年 | 104篇 |
2017年 | 84篇 |
2016年 | 80篇 |
2015年 | 126篇 |
2014年 | 123篇 |
2013年 | 205篇 |
2012年 | 289篇 |
2011年 | 274篇 |
2010年 | 150篇 |
2009年 | 138篇 |
2008年 | 187篇 |
2007年 | 274篇 |
2006年 | 202篇 |
2005年 | 198篇 |
2004年 | 189篇 |
2003年 | 171篇 |
2002年 | 157篇 |
2001年 | 135篇 |
2000年 | 123篇 |
1999年 | 116篇 |
1998年 | 75篇 |
1997年 | 62篇 |
1996年 | 66篇 |
1995年 | 51篇 |
1994年 | 39篇 |
1993年 | 36篇 |
1992年 | 63篇 |
1991年 | 75篇 |
1990年 | 79篇 |
1989年 | 79篇 |
1988年 | 87篇 |
1987年 | 59篇 |
1986年 | 59篇 |
1985年 | 59篇 |
1984年 | 34篇 |
1983年 | 35篇 |
1982年 | 19篇 |
1981年 | 17篇 |
1980年 | 16篇 |
1979年 | 29篇 |
1978年 | 17篇 |
1977年 | 28篇 |
1976年 | 19篇 |
1975年 | 23篇 |
1958年 | 14篇 |
排序方式: 共有4867条查询结果,搜索用时 31 毫秒
61.
CONTEXT: Despite widespread efforts to increase contraceptive use to prevent both pregnancy and sexually transmitted diseases among sexually active adolescents, most prior work examining adolescent contraceptive use does not explicitly recognize that sexual decision-making inherently involves both partners in a couple. METHODS: An analytic sample of 1,593 females who first had intercourse during adolescence (prior to age 18) was drawn from the 1995 National Survey of Family Growth. Logistic regression and multinomial logistic regression techniques were used to model the effects of sexual partners' characteristics and relationship type on contraceptive use at first intercourse and contraceptive method selected at first intercourse. RESULTS: Approximately 31% of respondents used no contraceptive method at first intercourse. Roughly half (52%) of adolescents who had just met their sexual partner used no method, compared with 24% of those who were going steady. Whereas 75% of teenagers who practiced contraception at first intercourse used a condom, 17% relied on the pill. In multivariate models, net of other variables, adolescents who had just met their partner had 66% lower odds than those who were going steady of practicing contraception at first intercourse. Individual-level factors that influenced contraceptive use at first intercourse were age at first intercourse, race or ethnicity family type, parents' education, grades in school and receipt of birth control education prior to first intercourse. Differences between respondents and their partner in age and race or ethnicity mostly were not significantly related to method use at first intercourse. One exception was that adolescents who first had sex with a man six or more years older had reduced odds of practicing contraception. Type of relationship was significantly associated with method selection only among adolescents who were just friends with their first partner, who had higher odds of using "other" methods rather than the condom. Variables associated with pill use rather than condom use were age at first sex, race, family type, mother's education and school grades. CONCLUSIONS: Further efforts to understand contraceptive choice among adolescents should focus on relationship features. Research on the decision-making process surrounding contraceptive use may benefit from treating this as a partner decision and not just as a decision made by one member of the couple. Further research examining the qualities of the relationship may provide important clues for understanding adolescent contraceptive choice. 相似文献
62.
Skin tumors induced in mice by initiation-promotion (2 microg DMBA-2 microg
TPA) protocols were found to be under multigenic control. Eighty- one N2
mice from the cross (BALB/cAnPt x SENCARA/Pt)F1 x SENCARA/Pt that were
either solidly resistant (no papillomas) or highly susceptible (> or = 7
papillomas/mouse) were subjected to a 'genome scan' using 89 microsatellite
markers to check for associations with susceptible and resistant
phenotypes. A locus on Chr 5 (Skts4) was found to control the
susceptibility of SENCARA/Pt mice and the resistance of BALB/cAnPt mice to
papilloma formation. In addition, higher than expected linkage scores were
seen for the markers D9Mit271, D11Mit268 and D12Mit56. Further work is
required to establish whether genes determining papilloma formation are
located in these regions of the genome. In general, no evidence was seen
for loss of heterozygosity in microsatellite markers on Chrs 5, 9 and 11 in
17 microdissected papillomas from (BALB/c x SENCARA)F1 hybrid mice.
相似文献
63.
64.
In order to enhance the immune efficacy of DNA vaccination, experiments were conducted to investigate the regulating effects of Bacillus Calmette-Guerin (BCG)-DNA as an adjuvant on immune responses of mice against foot-and-mouth disease (FMD), Aujeszky's disease (AID) and classical swine fever (CSF). BCG-DNA was purified from BCG by ion-exchange chromatography. Three DNA vaccines (pVSG, pVgD and pVE2) against the respective infection were constructed, and BCGDNA was coimmunized to mice by muscle injection. The results showed that titres of specific immunoglobulin (Ig)G to the vaccines mounted remarkably in the sera of the adjuvant covaccinated mice (P〈0.01). Antibody isotype IgG2a and IgG1 also increased, respectively, in mice coimmunized with BCG-DNA compared with those of the control groups (P〈0.01). Cellular immune cytokine interferon-gamma and cytotoxic T lymphocytes were detected in coimmunized BCG-DNA groups (P〈0. 05). Whereas interleukin-4, humoral immune cytokine, was not significant (P〉 0. 05). These results suggest that codelivery of BCG-DNA with DNA vaccines against FMD, AjD and CSF can enhance the induction of antigen-specific, especially, cell-mediated immunity. 相似文献
65.
High gastrointestinal hemorrhage represents the more frequent (12-71.1%) and heavy complication of hepatic cirrhosis and correlates to portal hypertension; it is weighed by global mortality which sways from 30 to 50%. High gastrointestinal hemorrhage gives, therefore, a serious of diagnostic and therapeutic problems not easy to guide for at least 3 reasons: numerous causes of bleeding; hepatic failure; the marigold possible therapies. Aim of this work is to clarify some diagnostic and therapeutic features about high gastrointestinal hemorrhage in cirrhotic patient, because such eventuality often presents dramatic aspects, which endangers the patient's life. Our experience shows a casuistry referred to the period of time which goes from 1987 to 1998 and that comprehend 143 examined patients: 91 of them have been submitted to medical treatment (endoscopic sclerotherapy, glupressin e/o somatostatin); in 52 cases it has been possible to realize a surgical treatment, different from the elective therapy (33 pz) and emergency therapy. Immediate hemostatic effect obtained in both the conditions, has been satisfying with best results at a distance of three years and five years given by devascularization. As matter stands our preference of the devascularization surgical treatment, it seems appropriate to pay attention to the operation of mesocaval anastomosis which, either in our very brief experience (3 cases) or by international literature, seems to offer encouraging results. 相似文献
66.
Aman U Buzdar Nuhad K Ibrahim Deborah Francis Daniel J Booser Eva S Thomas Richard L Theriault Lajos Pusztai Marjorie C Green Banu K Arun Sharon H Giordano Massimo Cristofanilli Debra K Frye Terry L Smith Kelly K Hunt Sonja E Singletary Aysegul A Sahin Michael S Ewer Thomas A Buchholz Donald Berry Gabriel N Hortobagyi 《Journal of clinical oncology》2005,23(16):3676-3685
PURPOSE: The objective of this study was to determine whether the addition of trastuzumab to chemotherapy in the neoadjuvant setting could increase pathologic complete response (pCR) rate in patients with human epidermal growth factor receptor 2 (HER2) -positive disease. PATIENTS AND METHODS: Forty-two patients with HER2-positive disease with operable breast cancer were randomly assigned to either four cycles of paclitaxel followed by four cycles of fluorouracil, epirubicin, and cyclophosphamide or to the same chemotherapy with simultaneous weekly trastuzumab for 24 weeks. The primary objective was to demonstrate a 20% improvement in pCR (assumed 21% to 41%) with the addition of trastuzumab to chemotherapy. The planned sample size was 164 patients. RESULTS: Prognostic factors were similar in the two groups. After 34 patients had completed therapy, the trial's Data Monitoring Committee stopped the trial because of superiority of trastuzumab plus chemotherapy. pCR rates were 25% and 66.7% for chemotherapy (n = 16) and trastuzumab plus chemotherapy (n = 18), respectively (P = .02). The decision was based on the calculation that, if study continued to 164 patients, there was a 95% probability that trastuzumab plus chemotherapy would be superior. Of the 42 randomized patients, 26% in the chemotherapy arm achieved pCR compared with 65.2% in the trastuzumab plus chemotherapy arm (P = .016). The safety of this approach is not established, although no clinical congestive heart failure was observed. A more than 10% decrease in the cardiac ejection fraction was observed in five and seven patients in the chemotherapy and trastuzumab plus chemotherapy arms, respectively. CONCLUSION: Despite the small sample size, these data indicate that adding trastuzumab to chemotherapy, as used in this trial, significantly increased pCR without clinical congestive heart failure. 相似文献
67.
BACKGROUND: Surgical treatment in the patient effected by secondary hyperparathyroidism consists in subtotal parathyroidectomy or total parathyroidectomy plus autotransplantation of parathyroid tissue. METHODS: The results obtained with surgical treatment of 6 patients observed in the years 1995-1996 are analyzed. Two glands were hyperplastic in four patients, 3 in the others. Every patient was submitted to a subtotal parathyroidectomy. RESULTS: Postoperative course was marked by transient hypoparathyroidism in one case. After 18 months of follow-up, no recurrences were observed. CONCLUSIONS: It is pointed out that in case of secondary hyperparathyroidism subtotal parathyroidectomy represents the surgical treatment of choice, according with literature data. Otherwise total parathyroidectomy plus autotransplantation, characterized by a more complex surgical technique, lead to the same results. 相似文献
68.
Alonso JE Volgas DA Giordano V Stannard JP 《Clinical orthopaedics and related research》2000,(377):32-43
Traumatic dislocation of the hip is an extremely severe injury. Although previously considered an uncommon lesion, it now is seen more often as a result of motor vehicle accidents. In most cases, dislocation of the hip is associated with fractures of the acetabulum, which ultimately can result in a higher incidence of complications than the complications observed in pure simple dislocations. Early recognition and prompt closed reduction of the dislocated hip constitute the cornerstone of proper treatment of this injury. Once the dislocation is reduced, definitive treatment of the acetabular fracture can be delayed to obtain a precise diagnostic evaluation. If surgical reconstruction of the acetabular fracture is indicated, it is done best in the first 10 days after the injury. A few patients in whom nonconcentric reduction, failed closed reduction, or impaired neurologic status occurs after reduction will require early open reduction and internal fixation of the fracture. Complications can be caused by the initial injury or by the treatment. Avascular necrosis of the femoral head, degenerative osteoarthritis, and heterotopic ossification are the main complications encountered in patients with unsatisfactory final results. Despite a perfect reduction of the hip dislocation and anatomic reduction of the acetabular fracture, a significant degenerative process of the hip is expected when the patient is assessed at long-term followup. 相似文献
69.
70.
目的了解笔者所在医院2008年度临床感染病原菌的菌种分布及其耐药现状。方法用VITEK微生物自动鉴定仪鉴定菌种,纸片扩散法检测临床分离菌对各种抗菌药物的敏感性,判读标准参照当年的CLSI M100文件。结果临床分离的1900株病原菌中革兰阴性杆菌、革兰阳性球菌和真菌所占比例分别为68.42%、18.16%和12.32%。分离率最高的五种病原菌:铜绿假单胞菌、大肠埃希菌、肺炎克雷伯菌、鲍曼不动杆菌和白色假丝酵母菌,占所有分离病原菌的59.26%,排前20位的病原菌则占到近90%(89.63%)。革兰阴性杆菌仅对亚胺培南、头孢哌酮/舒巴坦、美洛培南、哌拉西林/他唑巴坦的平均耐药率低于30%,铜绿假单胞菌和鲍曼不动杆菌对亚胺培南、美洛培南的耐药率分别28.9%、32.9%和11.6%、24.7%,大肠埃希菌、肺炎克雷伯菌和奇异变形杆菌的ESBL阳性率分别是52.8%、37.2%和34.6%,金黄色葡萄球和凝固酶阴性葡萄球菌中耐甲氧西林株各占44.0%和60.0%,未检出万古霉素中介或耐药的葡萄球菌,检出万古霉素耐药的粪肠球菌和屎肠球菌各1株。念珠菌对氟康唑耐药率接近5%。结论临床感染病原菌构成变化不大,但真菌检出率逐年升高。非发酵菌耐药率最低的是头孢哌酮/舒巴坦,肠杆菌科耐药率最低的是亚胺培南,ESBL的阳性率逐年升高。加强病原菌及其耐药性检测和监测,对病原学诊断及指导合理选用抗生素具重要参考价值。 相似文献