首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1242篇
  免费   78篇
  国内免费   2篇
耳鼻咽喉   13篇
儿科学   27篇
妇产科学   35篇
基础医学   174篇
口腔科学   34篇
临床医学   122篇
内科学   266篇
皮肤病学   16篇
神经病学   222篇
特种医学   22篇
外科学   165篇
综合类   2篇
一般理论   1篇
预防医学   87篇
眼科学   9篇
药学   57篇
中国医学   2篇
肿瘤学   68篇
  2023年   10篇
  2022年   8篇
  2021年   29篇
  2020年   13篇
  2019年   30篇
  2018年   34篇
  2017年   23篇
  2016年   18篇
  2015年   26篇
  2014年   35篇
  2013年   61篇
  2012年   84篇
  2011年   68篇
  2010年   38篇
  2009年   36篇
  2008年   49篇
  2007年   81篇
  2006年   76篇
  2005年   76篇
  2004年   65篇
  2003年   51篇
  2002年   58篇
  2001年   30篇
  2000年   32篇
  1999年   34篇
  1998年   17篇
  1997年   11篇
  1996年   13篇
  1995年   12篇
  1994年   6篇
  1993年   13篇
  1992年   9篇
  1991年   18篇
  1990年   18篇
  1989年   13篇
  1988年   12篇
  1987年   11篇
  1986年   7篇
  1985年   9篇
  1984年   11篇
  1983年   7篇
  1982年   7篇
  1981年   8篇
  1980年   6篇
  1979年   10篇
  1978年   7篇
  1974年   3篇
  1973年   3篇
  1964年   3篇
  1961年   3篇
排序方式: 共有1322条查询结果,搜索用时 15 毫秒
1.
The goal of this longitudinal study was to investigate the precursors of early reading development in 52 children with cerebral palsy at kindergarten level in comparison to 65 children without disabilities. Word Decoding was measured to investigate early reading skills, while Phonological Awareness, Phonological Short-term Memory (STM), Speech Perception, Speech Production and Nonverbal Reasoning were considered reading precursors. Children with cerebral palsy lag behind on all reading precursors at the beginning of the second year of kindergarten. For the children without disabilities, early reading skills in Grade 1 were best predicted by Phonological Awareness and Phonological STM while Speech Production was the most important predictor of early reading success for the children with cerebral palsy, followed by Phonological Awareness and Speech Perception. Furthermore, for children with cerebral palsy, Speech Production appears to dominate reading development, as Speech Production measured at the beginning of the second year of kindergarten was strongly predictive of all other reading precursors measured at the end of the second year of kindergarten. The results of this study reveal that children with cerebral palsy with additional speech impairments are at risk for limited literacy development. Clinical implications are discussed.  相似文献   
2.
It is demonstrated that tubular fragments derived from human testes and cultured in vitro produce a factor that stimulates the production of testosterone by human interstitial cells and by Percoll-purified Leydig cells from rat and mouse origin. The active principle in the conditioned media is a thermo-labile and trypsin-sensitive protein with an MW greater than 10,000. The factor is active in the presence as well as in the absence of maximally effective concentrations of LH and its activity is not accompanied by measurable changes in cAMP production. There are several points of analogy between this factor and a Leydig cell stimulatory protein produced by rat Sertoli cells. Molecular weight fractionation of spent media from human testicular tubules using an Amicon ultrafiltration system results in a 38- to 102-fold increase in Leydig cell stimulatory activity in a fraction corresponding to a molecular weight of 10,000 up to 30,000. These figures are comparable to those observed after molecular weight fractionation of spent media from rat Sertoli cells. Dose-response curves with partially purified preparations from human and rat origin yield parallel dose-response curves. In rat Sertoli cells as well as in human testicular tubules, the production of the active principle is stimulated by FSH and dibutyryl cAMP. Finally, maximally effective concentrations of the active principles of human and rat origin display no additive effects whereas additive effects are clearly evident with other Leydig cell stimulatory factors such as LHRHa and EGF. The hypothesis is advanced that the Leydig cell stimulatory factors from tubular origin may act as paracrine regulatory molecules responsible for the effects of FSH on Leydig cell function.  相似文献   
3.
The aim of this experiment was to design a suitable mouse model for male subfertility in which to study the effect of decreased sperm quality on embryo quality in vivo and in vitro. To achieve male subfertility, testes of adult male mice were immersed in water at either 42 degrees C (heated) or 33 degrees C (controls) during 20 min. Twenty-eight days after treatment, all heat stressed males showed a significant decrease in relative testis weight [384.7 mg in controls (286.7-460.6) versus 323 mg in stress heated groups (117.9-405.6); P < 0.001], sperm concentration [3.75 x 10(6)/ml (2.75-7.25) versus 1.00 x 10(6)/ml (0-4.00); P < 0.001] and progressive sperm motility [57.5% (48.0-79.0) versus 42.5% (14.0-66.0); P < 0.001]. Moreover, after mating to heat exposed males, not only the number of pregnant females (20/22 versus 18/30) but also the weight of their embryos [275.4 mg (78.7-339.4) versus 261.8 mg (68.1-339.0); P < 0.001] was significantly lower at 14.5 days post coitum when compared to controls. Neither the number of resorption sites nor the number of viable embryos per pregnant female was significantly different between groups. Also, the in-vitro fertilization rate of oocytes, fertilized by spermatozoa collected from heat stressed males, was significantly lower (44.9%; P < 0.0001) when compared to controls (65.1%; P < 0.0001). In conclusion, the results of this study suggest that male subfertility induced by acute scrotal heating may result in impaired sperm quality, reduced embryo weight in vivo and decreased fertilization rate in vitro.   相似文献   
4.
OBJECTIVE: To evaluate how Belgian health care providers deal with a request for emergency contraception. METHOD: In 2002-2003 we conducted 12 focus groups with pharmacists, general practitioners and school physicians. A skilled moderator accompanied by an observer conducted the focus groups using a semi-structured screenplay. RESULTS: All these health care providers agree with the free access to emergency contraception (EC), but experience considerable frustration with regard to the practical aspects and the legal framework. General practitioners (GPs) claim to spend a lot of time on requests for EC and they are concerned about the quality of the counselling provided in pharmacies. Pharmacists are creative when giving counselling in the pharmacy, but there is, nevertheless, a problem with a lack of privacy. School physicians are frustrated that there is no legal possibility to respond to a request for EC when they feel they are ideally placed to advise adolescents. CONCLUSION: The over-the-counter sale of EC offers women better access, but many barriers still interfere with optimal care. Pharmacists experience a lack of skills to communicate with adolescents and a lack of privacy to give counselling. GPs have good intentions, but are confronted with a lack of willingness on the part of the patients and also financial barriers. School physicians want more possibilities to help adolescents.  相似文献   
5.
6.
INTRODUCTION: We describe the use of emergency contraception (EC) and its association with sociodemographic, contraceptive and behavioural characteristics in a sample of family practice attendants in Belgium. METHODS: The study was part of a large Chlamydia trachomatis (CT) prevalence study in general practice. Sexually active women under 40 who consulted their general practitioner for routine gynaecological care were enrolled in the study. Participants completed a questionnaire on sociodemographic variables, urogenital symptoms, sexual history and sexual behaviour, and delivered a sample for CT testing. Logistic regression analysis was performed to identify determinants of a history of EC use in women in this sample. RESULTS: Of 815 questioned women, 23.5% had ever used EC. EC users were a heterogeneous group with respect to educational level, age and ethnicity. The use of emergency contraception was associated with the level of urbanisation, condom use, not having children yet, young age of first sexual intercourse, having had multiple partners in the past year, a history of unintended pregnancy, and current or previous STI. DISCUSSION: Information on availability and correct use of EC, and on the need for additional testing for STI, are necessary to help primary care attendees to preserve their future reproductive health.  相似文献   
7.
Neurotrophin treatment has so far failed to prolong the survival of individuals affected with amyotrophic lateral sclerosis (ALS), an incurable motoneuron degenerative disorder. Here we show that intracerebroventricular (i.c.v.) delivery of recombinant vascular endothelial growth factor (Vegf) in a SOD1(G93A) rat model of ALS delays onset of paralysis by 17 d, improves motor performance and prolongs survival by 22 d, representing the largest effects in animal models of ALS achieved by protein delivery. By protecting cervical motoneurons, i.c.v. delivery of Vegf is particularly effective in rats with the most severe form of ALS with forelimb onset. Vegf has direct neuroprotective effects on motoneurons in vivo, because neuronal expression of a transgene expressing the Vegf receptor prolongs the survival of SOD1(G93A) mice. On i.c.v. delivery, Vegf is anterogradely transported and preserves neuromuscular junctions in SOD1(G93A) rats. Our findings in preclinical rodent models of ALS may have implications for treatment of neurodegenerative disease in general.  相似文献   
8.
The SH2 domain-containing transforming Shc protein has been implicated in mitogenic signaling via several surface receptors through p21ras. Following tyrosine phosphorylation by either receptor or non-receptor tyrosine kinases, Shc may interact with the adaptor protein Grb2, which is linked to Sos1, a guanine nucleotide exchange factor for human ras. Ligation of the antigen receptor complex on B cells (BCR) is known to activate various intracellular signaling pathways, which may accumulate in mitogenic responses. With respect to the initial steps, the activation of BCR-associated non-receptor tyrosine kinases appears to be indispensible. In this report we show that Shc proteins become tyrosine phosphorylated after BCR ligation on both transformed and normal human B cells. This is accompanied by the association of Shc with Grb2 proteins and a yet unidentified 145-kDa tyrosine phosphorylated protein. Subcellular fractionation revealed that this activation-induced multimeric Shc complex rapidly translocates towards the plasma membrane. Co-ligation of the BCR with the CD19 molecule results in a marked increase of these events, whereas CD19 cross-linking alone does not induce Shc tyrosine phosphorylation or translocation. Thus, in B cells the Shc complex may represent a molecular junction between the BCR and the mitogenic p21ras cascade.  相似文献   
9.
Monoclonal antibody L26 is a highly selective marker of B cells and B-cell neoplasms in paraffin-embedded tissues, but it suffers from the drawback that the target molecule has not been identified. In this paper we provide evidence by two independent techniques that antibody L26 recognizes an intracellular epitope on the CD20 antigen (a pan B-cell marker). When this antigen was redistributed on the surface of unfixed viable B cells by incubation with monoclonal anti-CD20 followed by anti-mouse Ig, the diffuse cytoplasmic staining of L26 was abolished and replaced by coincident dotlike labeling for antibody L26 and the CD20 antigen. None of the other antibodies tested (covering 10 different B-cell-associated antigens) had this effect on the L26 staining pattern. Furthermore, COS-1 cells transfected with cDNA encoding the CD20 molecule gave positive staining with antibody L26 and with two other CD20 reagents, but not with antibodies to other pan B-cell markers (eg, CD19 and CD22).  相似文献   
10.
BACKGROUND: This trial was conducted to compare cycle control with vaginal ring a combined contraceptive vaginal ring, and a combined oral contraceptive (COC) delivering 30 mug ethinylestradiol (EE) and 150 mug levonorgestrel. METHODS: This open-label, randomized, multi-centre, Phase III study involved adult women from 11 countries. Subjects were treated with either vaginal ring or a COC for 13 cycles (12 months). RESULTS: A total of 1030 subjects (vaginal ring, n=512; COC, n=518) comprised the intention-to-treat (ITT) population. The percentage of women in the ITT population who completed the trial was 70.9% for vaginal ring and 71.2% for the COC group. The incidence of breakthrough bleeding and spotting over cycles 2-13, the primary efficacy parameter, was lower with vaginal ring (range 2.0-6.4%) than the COC (range 3.5-12.6%), and for cycles 2 and 9 the lower incidence with vaginal ring was confirmed as statistically significant (P=0.003 and P=0.002 respectively). The incidence of intended bleeding was significantly higher over all cycles with vaginal ring (58.8-72.8%) than with the COC (43.4-57.9%). CONCLUSIONS: Cycle control with vaginal ring was excellent and superior to that of a COC containing 30 mug EE.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号