全文获取类型
收费全文 | 470篇 |
免费 | 32篇 |
国内免费 | 38篇 |
专业分类
耳鼻咽喉 | 4篇 |
儿科学 | 17篇 |
妇产科学 | 1篇 |
基础医学 | 44篇 |
口腔科学 | 47篇 |
临床医学 | 66篇 |
内科学 | 62篇 |
皮肤病学 | 11篇 |
神经病学 | 17篇 |
特种医学 | 95篇 |
外国民族医学 | 1篇 |
外科学 | 81篇 |
综合类 | 24篇 |
预防医学 | 14篇 |
眼科学 | 4篇 |
药学 | 24篇 |
肿瘤学 | 28篇 |
出版年
2023年 | 4篇 |
2022年 | 4篇 |
2021年 | 4篇 |
2020年 | 6篇 |
2019年 | 13篇 |
2018年 | 9篇 |
2017年 | 5篇 |
2016年 | 6篇 |
2015年 | 3篇 |
2014年 | 6篇 |
2013年 | 4篇 |
2012年 | 4篇 |
2011年 | 16篇 |
2010年 | 16篇 |
2009年 | 18篇 |
2008年 | 20篇 |
2007年 | 22篇 |
2006年 | 14篇 |
2005年 | 26篇 |
2004年 | 9篇 |
2003年 | 4篇 |
2002年 | 11篇 |
2001年 | 10篇 |
2000年 | 14篇 |
1999年 | 13篇 |
1998年 | 17篇 |
1997年 | 22篇 |
1996年 | 26篇 |
1995年 | 14篇 |
1994年 | 12篇 |
1993年 | 24篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 12篇 |
1988年 | 18篇 |
1987年 | 14篇 |
1986年 | 11篇 |
1985年 | 9篇 |
1984年 | 11篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 12篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 3篇 |
排序方式: 共有540条查询结果,搜索用时 15 毫秒
51.
Protein C, an antithrombotic protein, is reduced in hospitalized patients with intravascular coagulation 总被引:7,自引:0,他引:7
Activated protein C is a potent anticoagulant and profibrinolytic enzyme that can be derived from the vitamin-K-dependent serine protease zymogen, protein C, by the action of thrombin. Protein C antigen concentration was determined in plasmas from normals (n = 40) and from 38 patients with intravascular coagulation as evidenced by positive FDP (greater than micrograms/ml). Plasma protein C was 4 micrograms/ml in normals and was significantly depressed (less than 2 SD below the mean of normals) in 19 of the 38 patients. Of 15 patients with suspected intravascular coagulation but normal FDP, protein C was decreased in 5 individuals; 3 of these 5 patients had liver disease. Based on these results, we suggest that extensive activation of the coagulation system in vivo causes a significant consumption of protein C, presumably due to its activation by thrombin and subsequent clearance. 相似文献
52.
Identification of a novel complex between human kallikrein 2 and protease inhibitor-6 in prostate cancer tissue. 总被引:7,自引:0,他引:7
S D Mikolajczyk L S Millar K M Marker H G Rittenhouse R L Wolfert L S Marks M C Charlesworth D J Tindall 《Cancer research》1999,59(16):3927-3930
Human kallikrein (hK) 2 is an arginine-selective serine protease expressed predominantly in the prostate that has an 80% sequence identity with prostate-specific antigen. Expression of hK2 is elevated in the tumor epithelium compared to benign prostate tissue. We have purified, sequenced, and identified a novel hK2 complex in prostate tissue consisting of hK2 and a serine protease inhibitor known as protease inhibitor-6 (PI-6). This 64-kDa SDS-PAGE stable complex is elevated in the tumor and is approximately 10% of total hK2. No comparable complex of prostate-specific antigen was detected. PI-6, also known as cytoplasmic antiprotease, has been characterized as an intracellular inhibitor of trypsin and chymotrypsin-like proteases, which has high homology to plasminogen activator inhibitor 1 and 2. The physiological role of PI-6 in the prostate and its relationship to hK2 and prostate cancer are under investigation. 相似文献
53.
54.
55.
Immunohistochemical localization of membrane and alpha-granule proteins in human megakaryocytes: application to plastic-embedded bone marrow biopsy specimens 总被引:12,自引:2,他引:12
Using a new technique for antigen localization, we have demonstrated platelet proteins in megakaryocytes in plastic-embedded biopsy specimens of normal human bone marrow. In a series of 25 specimens, megakaryocytes showed labeling with antibodies to the integral membrane glycoproteins IIIa, IIb, and the IIb-IIIa complex; granule membrane protein 140; and five alpha-granule matrix proteins: thrombospondin, factor VIII-related antigen, beta-thromboglobulin, platelet factor 4, and fibrinogen. The antibodies to the membrane glycoproteins IIIa, IIb, and IIb-IIIa produced diffuse cytoplasmic staining and heavier staining on the plasma membrane, whereas the antibodies to the alpha-granule matrix proteins produced a distinct granular staining within the cytoplasm. Staining for granule membrane protein 140 was also granular in distribution. Rare mononuclear cells consistent with megakaryocyte precursors were labeled with these markers. Other enzyme histochemical and lectin-binding studies showed that the enzyme alpha-naphthyl acetate esterase, the lectin Ulex europaeus I, and the periodic-acid Schiff reaction were consistent, but not specific, markers of megakaryocytes. This immunohistochemical technique should facilitate the examination of qualitative and quantitative changes in megakaryocytes in a variety of physiologic and pathologic processes. 相似文献
56.
The magnetic resonance (MR) relaxation rates of protons were compared in the myelinated and nonmyelinated nerves of the garfish. The long, large olfactory nerve of the garfish, as an easily accessible source of nonmyelinated axons, is uniquely suited for such a comparison. The T1 and T2 measurements revealed distinct and consistent differences between nonmyelinated olfactory nerves and myelinated optic and oculomotor nerves. Comparisons between water content, lipid content, and relaxation rates indicated that the differences in MR properties represent complex differences in the distribution and physical environment of the constituent lipid and water protons. 相似文献
57.
This paper discusses interpretations and practical requirements for fulfilling informed consent on social surveys, particularly in the health field, in order to achieve a balance between two competing principles: the public good of carrying out high-quality survey research which requires unbiased representative participation; and respect for individuals’ rights to refuse to participate. 相似文献
58.
OBJECTIVE: To elucidate which components of peer norms influence the process of sexual initiation for young adolescents. Design. Prospective cohort study. Setting. Fourteen elementary and middle schools in an urban public school district. Participants. The 1389 sixth-grade students who completed the questionnaire at the beginning (time 1) and at the end (time 2) of the school year comprise the study sample. Mean age at time 1 was 11.7 years. RESULTS: Of students entering the sixth grade, 30% (n = 416) reported having already initiated sexual intercourse, 5% (n = 74) reported initiating sexual intercourse during the sixth-grade school year (initiated group), and 63% (n = 873) reported not having initiated sexual intercourse by the end of the sixth-grade school year (never group). Demographic comparisons revealed that students in the initiated group were significantly more likely than students in the never group to be older (11.9 years vs 11.6 years), male (58% vs 37%), African-American (70% vs 51%), attending a poorer school (87% vs 85%), and living in an area with a high proportion of single-parent families (45% vs 41%). Self-reports and reports of peers' participation in nonsexual risk behaviors were more common for students in the initiated group. Students in the initiated group were more likely than students in the never group to perceive: 1) a high prevalence of sexual initiation among peers; 2) social gains associated with early sexual intercourse; and 3) younger age of peers' sexual initiation. Students in the never group were more likely to believe that sexually-experienced 12-year-old boys would be negatively stigmatized compared with students in the initiated group. Three predictive models were developed to test the relationship between peer norms and the process of initiation. These models demonstrate that the strongest predictor of sexual initiation in sixth grade is having high intention to do so at the beginning of sixth grade. The strongest predictor of high intention is belief that most friends have already had sexual intercourse. Perceptions of social gain and stigma for sexually-experienced 12-year-old boys act independently of intention to decrease risk of early sexual initiation. CONCLUSION: Early sexual intercourse is not an unplanned experience for many teens. Decisions about initiation are strongly bound to social context with peers playing an important role in creating a sense of normative behavior. Specific components of peer norms impact the process of sexual initiation in both positive and negative ways. Interventions aimed at delaying the onset of sexual initiation need to focus on cohort norms as well as on an individual's perceptions and behaviors. 相似文献
59.
DF Stroncek 《Transfusion》1992,32(2):180-189
60.
Complications of angiography 总被引:14,自引:0,他引:14