全文获取类型
收费全文 | 46895篇 |
免费 | 3624篇 |
国内免费 | 74篇 |
专业分类
耳鼻咽喉 | 445篇 |
儿科学 | 1614篇 |
妇产科学 | 1177篇 |
基础医学 | 6263篇 |
口腔科学 | 925篇 |
临床医学 | 5808篇 |
内科学 | 8380篇 |
皮肤病学 | 634篇 |
神经病学 | 4448篇 |
特种医学 | 1223篇 |
外国民族医学 | 1篇 |
外科学 | 6167篇 |
综合类 | 862篇 |
一般理论 | 94篇 |
预防医学 | 5758篇 |
眼科学 | 853篇 |
药学 | 2624篇 |
中国医学 | 23篇 |
肿瘤学 | 3294篇 |
出版年
2023年 | 396篇 |
2022年 | 629篇 |
2021年 | 1324篇 |
2020年 | 821篇 |
2019年 | 1284篇 |
2018年 | 1413篇 |
2017年 | 1032篇 |
2016年 | 1062篇 |
2015年 | 1154篇 |
2014年 | 1633篇 |
2013年 | 2255篇 |
2012年 | 3348篇 |
2011年 | 3327篇 |
2010年 | 1820篇 |
2009年 | 1504篇 |
2008年 | 2625篇 |
2007年 | 2642篇 |
2006年 | 2599篇 |
2005年 | 2528篇 |
2004年 | 2261篇 |
2003年 | 1990篇 |
2002年 | 1789篇 |
2001年 | 665篇 |
2000年 | 662篇 |
1999年 | 638篇 |
1998年 | 468篇 |
1997年 | 313篇 |
1996年 | 294篇 |
1995年 | 255篇 |
1994年 | 250篇 |
1993年 | 239篇 |
1992年 | 502篇 |
1991年 | 424篇 |
1990年 | 402篇 |
1989年 | 378篇 |
1988年 | 374篇 |
1987年 | 332篇 |
1986年 | 349篇 |
1985年 | 355篇 |
1984年 | 283篇 |
1983年 | 285篇 |
1982年 | 223篇 |
1981年 | 247篇 |
1980年 | 200篇 |
1979年 | 288篇 |
1978年 | 227篇 |
1977年 | 182篇 |
1975年 | 170篇 |
1974年 | 204篇 |
1973年 | 214篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
We report a case of left iliofemoral vein thrombosis with extension to the inferior vena cava associated with giant right hydronephrosis secondary to ureteropelvic junction obstruction. Surgery revealed marked infrarenal vena caval compression and deviation to the left side caused by the dilated right renal pelvis, with resultant kinking of the origin of the left iliac vein. It is postulated that the reduction in blood flow caused by this compression and distortion predisposed this patient to venous thrombosis. 相似文献
6.
Three cases of voluntary posterior instability of the shoulder are presented. They have all responded well to a program of electromyographic monitored biofeedback. This method offers a means of enhancing the results of nonoperative treatment. 相似文献
7.
A new micelle system formed from methoxy (polyethylene glycol)-b-poly (5-benzyloxy-trimethylene carbonate; MePEG-b-PBTMC 5000-b-4800) was investigated as a delivery system for the hydrophobic anti-cancer agent, ellipticine. The ellipticine was loaded into the MePEG-b-PBTMC micelles with a loading efficiency of 95% using a high-pressure extrusion technique. The ellipticine-loaded micelles have a spherical morphology and an average diameter of 96 nm. The anti-cancer activity of ellipticine was confirmed to be retained following formulation in the MePEG-b-PBTMC micelles. The extent of protein adsorption to the MePEG-b-PBTMC micelles was investigated by transmission electron microscopy, dynamic light scattering and gel filtration chromatography. Overall, the amount of protein both loosely and tightly associated with the micelles was found to be minimal and insignificant. The partitioning properties of ellipticine between an aqueous medium containing protein and the MePEG-b-PBTMC micelles were examined over a range of protein concentrations. Under physiologically relevant conditions, it was found that 61% of the drug remained within the micelle fraction while 39% was in the protein-containing aqueous phase. In addition, the in vitro drug release profile of ellipticine from the micelles was fit using a modified Higuchi model and found to be accelerated in the presence of protein. These studies demonstrate that although there are no significant interactions between micelle and protein, the properties of the micelle as a delivery vehicle may be strongly influenced by protein-drug interactions. 相似文献
8.
9.
Rebecca P. Ang Robert M. Klassen Wan Har Chong Vivien S. Huan Isabella Y.F. Wong Lay See Yeo Lindsey L. Krawchuk 《Journal of adolescence》2009,32(5):1225-1237
We provide further evidence for the two-factor structure of the 9-item Academic Expectations Stress Inventory (AESI) using confirmatory factor analysis on a sample of 289 Canadian adolescents and 310 Singaporean adolescents. Examination of measurement invariance tests the assumption that the model underlying a set of scores is directly comparable across groups. This study also examined the cross-cultural validity of the AESI using multigroup confirmatory factor analysis across both the Canadian and Singaporean adolescent samples. The results suggested cross-cultural invariance of form, factor loadings, and factor variances and covariances of the AESI across both samples. Evidence of AESI's convergent and discriminant validity was also reported. Findings from t-tests revealed that Singaporean adolescents reported a significantly higher level of academic stress arising from self expectations, other expectations, and overall academic stress, compared to Canadian adolescents. Also, a larger cross-cultural effect was associated with academic stress arising from other expectations compared with academic stress arising from self expectations. 相似文献
10.
Human immunodeficiency virus infection in urban Rwanda. Demographic and behavioral correlates in a representative sample of childbearing women 总被引:9,自引:0,他引:9
S Allen C Lindan A Serufilira P Van de Perre A C Rundle F Nsengumuremyi M Carael J Schwalbe S Hulley 《JAMA》1991,266(12):1657-1663
OBJECTIVE.--To determine behavioral and demographic risk factors for human immunodeficiency virus (HIV) infection in central Africa. DESIGN.--Cross-sectional survey. SETTING.--Kigali, Rwanda. PARTICIPANTS.--A representative sample of 1458 childbearing women aged 19 to 37 years who were recruited from outpatient prenatal and pediatric clinics at the only community hospital in the city. MAIN OUTCOME MEASURE.--Antibodies to HIV assessed by enzyme immunoassay and confirmed by Western blot or indirect immunofluorescence. RESULTS.--The HIV seroprevalence was 32% overall. Infection rates were higher in women who were single, in those in steady relationships that began after 1981, and in the 33% of women reporting more than one lifetime sexual partner. Women in legal marriages or monogamous partnerships had lower rates of infection, but even low-risk women had prevalences on the order of 20%. History of venereal disease in the past 5 years, although the strongest risk factor in a multiple logistic analysis (odds ratio, 2.7; 95% confidence interval, 2.0 to 3.7), was reported by only 30% of those infected. Having a male sexual partner who drank alcohol or who had higher income were significant risk factors for HIV infection in the multivariate analysis, but use of oral contraceptives and having an uncircumcised partner were not. CONCLUSIONS.--The epidemic of the acquired immunodeficiency syndrome in Rwanda has spread beyond high-risk groups to the general population of women without known risk factors. For most of these women, a steady male partner is the source of their HIV risk and therefore a vital target for intervention efforts. 相似文献