全文获取类型
收费全文 | 6187篇 |
免费 | 1031篇 |
国内免费 | 8篇 |
专业分类
耳鼻咽喉 | 49篇 |
儿科学 | 252篇 |
妇产科学 | 141篇 |
基础医学 | 913篇 |
口腔科学 | 149篇 |
临床医学 | 882篇 |
内科学 | 1064篇 |
皮肤病学 | 60篇 |
神经病学 | 745篇 |
特种医学 | 247篇 |
外国民族医学 | 1篇 |
外科学 | 714篇 |
综合类 | 506篇 |
一般理论 | 3篇 |
预防医学 | 485篇 |
眼科学 | 120篇 |
药学 | 602篇 |
中国医学 | 2篇 |
肿瘤学 | 291篇 |
出版年
2021年 | 77篇 |
2020年 | 48篇 |
2019年 | 77篇 |
2018年 | 107篇 |
2017年 | 74篇 |
2016年 | 75篇 |
2015年 | 109篇 |
2014年 | 143篇 |
2013年 | 189篇 |
2012年 | 264篇 |
2011年 | 282篇 |
2010年 | 148篇 |
2009年 | 145篇 |
2008年 | 226篇 |
2007年 | 252篇 |
2006年 | 277篇 |
2005年 | 278篇 |
2004年 | 251篇 |
2003年 | 240篇 |
2002年 | 247篇 |
2001年 | 212篇 |
2000年 | 219篇 |
1999年 | 207篇 |
1998年 | 118篇 |
1997年 | 79篇 |
1996年 | 104篇 |
1995年 | 80篇 |
1994年 | 69篇 |
1993年 | 73篇 |
1992年 | 151篇 |
1991年 | 168篇 |
1990年 | 127篇 |
1989年 | 152篇 |
1988年 | 141篇 |
1987年 | 180篇 |
1986年 | 139篇 |
1985年 | 142篇 |
1984年 | 120篇 |
1983年 | 107篇 |
1982年 | 82篇 |
1981年 | 89篇 |
1980年 | 101篇 |
1979年 | 100篇 |
1978年 | 65篇 |
1977年 | 67篇 |
1976年 | 56篇 |
1975年 | 56篇 |
1974年 | 67篇 |
1972年 | 66篇 |
1970年 | 48篇 |
排序方式: 共有7226条查询结果,搜索用时 15 毫秒
91.
92.
Neural control of the endocrine pancreas 总被引:14,自引:0,他引:14
93.
Whereas school‐based prevention programs often target deficits in individual children's social skills in order to limit their aggression or exposure to peer victimization, there is increasing evidence that school‐wide and classroom‐level factors can also affect the success of these programs. This short‐term longitudinal study involved 432 elementary school students from 44 classrooms in 17 urban schools. We investigated whether classroom characteristics (average levels of social competence, emotional problems, and behavioral problems) and school‐wide characteristics (proportion of children on income assistance and implementation of a peer victimization prevention program—the Walk away, Ignore, Talk, and Seek help [W.I.T.S.] program) experienced in Grade 1 influences changes in children's reports of relational and physical victimization at the end of Grade 2. Findings showed that classroom levels of emotional problems predicted increases in relational victimization (beyond individual differences in emotional and behavioral problems). Classroom levels of behavioral problems predicted reports of increases in physical victimization (beyond individual differences). Classroom levels of social competence also interacted with individual levels of emotional problems such that children with higher levels of emotional problems in classes with more socially competent children reported more relational and physical victimization. Higher school levels of poverty and lack of program involvement also predicted higher levels of physical victimization, beyond individual and classroom effects. The capacity of the W.I.T.S. program to influence classroom level characteristics and the moderating effects of school poverty on victimization were also assessed. © 2003 Wiley Periodicals, Inc. J Comm Psychol 31: 397–418, 2003. 相似文献
94.
The effects of 4-hydroxyanisole on hamster cheek pouch 总被引:1,自引:0,他引:1
95.
The role of COX-2 in angiogenesis and rheumatoid arthritis 总被引:4,自引:0,他引:4
Woods JM Mogollon A Amin MA Martinez RJ Koch AE 《Experimental and molecular pathology》2003,74(3):282-290
Recent evidence suggests that cyclooxygenase (COX)-2 is a mediator of angiogenesis, and COX-2 activity is known to be upregulated in the rheumatoid arthritis (RA) synovium. We examined whether mediation of angiogenesis by COX-2 was occuring in cells of the RA synovium and in microvascular endothelial cells (ECs) that are similar to those found in the RA synovium. We demonstrate that rofecoxib, a selective COX-2 inhibitor, acts directly on human dermal microvascular ECs (HMVECs) to inhibit their chemotactic and tube forming ability. Likewise, pretreatment of HMVECs with rofecoxib significantly inhibited their ability to form tubes induced by conditioned media (CM) of activated RA synovial fibroblasts. When RA synovial fibroblasts were pretreated with rofecoxib for 16 h and then stimulated with interleukin (IL)-1beta, their CM induced significantly less HMVEC tube formation when compared with CM from vehicle-treated RA synovial fibroblasts. ELISAs performed on activated RA fibroblast CM for known proangiogenic factors demonstrated a significant reduction in bFGF, in addition to the expected decrease in PGE(2). Our studies suggest that COX-2-induced angiogenic activity is an active mechanism within diseased synovium and may provide an additional rationale for the use of COX-2 inhibitors in RA. 相似文献
96.
Purification and characterization of an extracellular protease from Pseudomonas cepacia. 总被引:7,自引:6,他引:7 下载免费PDF全文
An extracellular proteinase (PSCP) produced by Pseudomonas cepacia was purified from culture supernatants by ammonium sulfate precipitation, anion exchange chromatography on DEAE-Sephacel, and G200 gel filtration chromatography. The protease has an apparent Mr of 34,000 by electrophoresis. Substrates cleaved by the protease include gelatin, hide powder, and collagen but not human immunoglobulin G (IgG), IgM, secretory IgA, or IgA. The enzyme had the characteristics of a metalloprotease, a pH optimum of 6, and a temperature optimum of 45 degrees C. Intratracheal instillation of purified PSCP into rat lungs produced a bronchopneumonia characterized by polymorphonuclear cell infiltration and proteinaceous exudation into large airways. Rats responded immunologically to active immunization with PSCP, but this response was not protective against subsequent lung infection with P. cepacia. PSCP was shown to have antigenic similarity with Pseudomonas aeruginosa elastase by an immunoblotting technique. Sera from 10 cystic fibrosis patients, with and without a previous history of P. cepacia colonization, were shown to possess antibody reactive against PSCP. 相似文献
97.
98.
Carol M. Woods Jack L. Vevea Dianne L. Chambless Ute J. Bayen 《Clinical psychology》2002,9(4):353-366
Researchers have hypothesized that compulsive checkers suffer from impairment in explicit memory (e.g., Sher, Frost, & Otto, 1983 ), low confidence in explicit memory (e.g., McNally & Kohlbeck, 1993 ), or both. However, empirical findings have been equivocal, possibly due to variability in effect sizes produced by small samples. Combining data across studies may yield more meaningful conclusions than can be surmised from a narrative review. Following a brief review of the literature on checking and memory, we present meta-analytic results suggesting that checkers are impaired on many types of memory tasks (e.g., verbal free recall, verbal cued recall, and recall of actions) and are less confident in recognition than noncheckers. We discuss implications of these findings, suggestions for future research, and limitations of this analysis. 相似文献
99.
An ellipsoidal particle, measuring 450 x 150 nm, from honey bees comprises a nucleocapsid measuring 3000 x 40 nm, containing double-stranded DNA with a molecular weight of approximately 12 x 10(6), which is coiled within a membrane. The buoyant densities in CsCl of the whole particle, nucleocapsid, DNA and DNA with ethidium bromide are 1.28, 1.36, 1.71 and 1.61 g/ml, respectively. The particle contains about 12 proteins, with molecular weights ranging from 13,000 to 70,000, which are distributed approximately equally between the membrane and the nucleocapsid. 相似文献
100.
Fear-Potentiated Startle in Humans: Effects of Anticipatory Anxiety on the Acoustic Blink Reflex 总被引:7,自引:0,他引:7
Christian Grillon Rezvan AMELI Scott W. Woods Kathleen Merikangas Michael Davis 《Psychophysiology》1991,28(5):588-595
The effects of fear/anticipatory anxiety on the acoustic startle reflex were investigated in humans using a paradigm involving anticipation of electric shocks. The eyeblink component of the startle reflex, elicited by an abrupt auditory stimulus, was measured in 9 normal volunteers during either the anticipation of electric shocks (anticipatory anxiety) or periods in which no shocks were anticipated (safe period). The eyeblink was consistently higher in amplitude, and shorter in latency, during periods when the subjects anticipated shocks, compared to the safe periods. This effect could not be attributed solely to a reduction in habituation and was statistically significant before the subjects actually received any shock (a single 30 mA stimulation on the median nerve). These results indicate that anticipatory anxiety can be measured objectively in humans using the fear-potentiated startle reflex in a paradigm not actually requiring any shock. Because a great deal is known about the neuroanatomical and pharmacological mechanisms of fear-potentiated startle in laboratory animals, this test procedure may be especially useful in humans to investigate the neurobiological substrates of anxiety disorders and their pharmacological treatments. 相似文献