全文获取类型
收费全文 | 1281篇 |
免费 | 69篇 |
国内免费 | 4篇 |
专业分类
儿科学 | 80篇 |
妇产科学 | 29篇 |
基础医学 | 120篇 |
口腔科学 | 35篇 |
临床医学 | 107篇 |
内科学 | 310篇 |
皮肤病学 | 22篇 |
神经病学 | 53篇 |
特种医学 | 267篇 |
外科学 | 89篇 |
综合类 | 12篇 |
预防医学 | 86篇 |
眼科学 | 11篇 |
药学 | 66篇 |
中国医学 | 2篇 |
肿瘤学 | 65篇 |
出版年
2022年 | 12篇 |
2021年 | 19篇 |
2019年 | 9篇 |
2018年 | 18篇 |
2017年 | 15篇 |
2016年 | 15篇 |
2015年 | 21篇 |
2014年 | 25篇 |
2013年 | 32篇 |
2012年 | 39篇 |
2011年 | 29篇 |
2010年 | 45篇 |
2009年 | 46篇 |
2008年 | 35篇 |
2007年 | 30篇 |
2006年 | 28篇 |
2005年 | 26篇 |
2004年 | 18篇 |
2003年 | 22篇 |
2002年 | 19篇 |
2001年 | 14篇 |
2000年 | 11篇 |
1999年 | 20篇 |
1998年 | 52篇 |
1997年 | 69篇 |
1996年 | 53篇 |
1995年 | 42篇 |
1994年 | 52篇 |
1993年 | 53篇 |
1992年 | 12篇 |
1991年 | 20篇 |
1990年 | 19篇 |
1989年 | 48篇 |
1988年 | 49篇 |
1987年 | 35篇 |
1986年 | 34篇 |
1985年 | 34篇 |
1984年 | 15篇 |
1983年 | 24篇 |
1982年 | 17篇 |
1981年 | 20篇 |
1980年 | 22篇 |
1979年 | 10篇 |
1978年 | 17篇 |
1977年 | 17篇 |
1976年 | 12篇 |
1975年 | 24篇 |
1974年 | 7篇 |
1973年 | 10篇 |
1971年 | 9篇 |
排序方式: 共有1354条查询结果,搜索用时 31 毫秒
11.
Hormonal fluctuations associated with the menstrual cycle influence
appetite control and eating behaviour. Energy intake varies during the
reproductive cycle in humans and animals, with a periovulatory nadir and a
luteal phase peak. Patterns of macronutrient selection show less
consistency but a number of studies report carbohydrate cravings in the
premenstrual phase, particularly in women with premenstrual syndrome. The
cyclical nature of food cravings are frequently, but not invariably,
associated with depression. Fluctuations in appetite, cravings and energy
intake during the menstrual cycle may occur in parallel with cyclical
rhythms in serotonin, which can be accompanied by affective symptoms. The
premenstrual phase can be considered as a time when women are especially
vulnerable to overconsumption, food craving and depression; this is often
associated with low serotonin activity.
相似文献
12.
The effect of upper motor neuron regulation on skeletal muscle development was studied in the fetal pig. A region of the spinal cord at the level of the upper cervical vertebrae was destroyed by cauterization at 45 days of gestation in four pig fetuses. Five fetuses with intact spinal cords served as controls. Innervation and enzyme activities in the longissimus muscle, the ultrastructure and quantitation of satellite cells in the sartorius muscle, and plasma composition were evaluated at 110 days of gestation. The terminal innervation ratios were similar (P greater than 0.05) for muscles from control and cauterized fetuses. Endplate morphology was also similar. Therefore, innervation of newly formed primary fibers is not controlled by upper motor neurons after 45 days of gestation. Mean values for body weight, percentage of muscle dry weight, percentage of myofibers with myonuclei and plasma levels of protein, glucose, triglycerides, lactate, and creatine phosphokinase activity were similar (P greater than 0.05) between the two groups of fetuses. All but one muscle fiber examined was of the secondary fiber type. These observations suggest that the physiological maturity of the muscle was not appreciably altered even though glucose-6-phosphate dehydrogenase activity was higher (P greater than 0.05) and total phosphorylase activity was lower (P greater than 0.05) in the spinal cauterized fetuses than in the control group. The percentage of satellite cells was lower when based on the number of myofibers observed (P greater than 0.005) or on the number of nuclei contained within the basal lamina (P greater than 0.001) in the muscle of the spinal cauterized fetuses than in the control fetuses. The cytoplasm of satellite cells from the muscles of control fetuses was rich in organelles indicative of metabolic and mitotic activity whereas a paucity of such organelles was observed in the satellite cells of cauterized fetuses. Since the percentage of myofibers that had myonuclei was similar (P greater than 0.05) for the control and cauterized fetuses, it appeared that the myonuclear population was maintained by direct incorporation of the parent satellite cell. 相似文献
13.
Telfer JF; Thomson AJ; Cameron IT; Greer IA; Norman JE 《Human reproduction (Oxford, England)》1997,12(10):2306-2312
Superoxide, an agent which attenuates the half-life of nitric oxide, is
metabolized and synthesized by superoxide dismutase (SOD) and xanthine
oxidase, respectively. Over the last few years much work has focused on the
role of nitric oxide in human parturition. The aim of this study was to
determine whether the onset of human parturition is associated with a
change in the expression of copper/zinc superoxide dismutase (Cu/Zn SOD),
manganese superoxide dismutase (Mn SOD) or xanthine oxidase within the
uterus. Samples of myometrium, placenta, decidua and fetal membranes were
obtained from women before and after the onset of labour at term.
Immunocytochemistry was used to localize Cu/Zn SOD, Mn SOD and xanthine
oxidase and measure SOD enzyme activity. Cu/Zn and Mn SOD-like
immunoreactivity was detected in syncytiotrophoblast cells, villous stromal
cells and endothelial cells of blood vessels in the placenta. In the
myometrium Cu/Zn and Mn SOD were localized to myocytes and endothelial
cells and to some vascular smooth muscle cells. In the fetal membranes we
observed staining for Cu/Zn SOD and Mn SOD in the amnion, chorion,
extravillous trophoblast and decidua. There was no difference in SOD enzyme
activity or staining intensity for SOD between different cell types before
and during labour. Xanthine oxidase immunoreactivity was identified in each
of the tissues examined and again there was no difference in immunostaining
in tissues obtained from women delivered before or after the onset of
labour. These results show that the pregnant uterus is capable of both
synthesizing and degrading superoxide and suggest that superoxide dismutase
and xanthine oxidase may play a role in the maintenance of uterine
quiescence during pregnancy, but not in the initiation of parturition.
相似文献
14.
Hydrosalpinges adversely affect markers of endometrial receptivity 总被引:22,自引:10,他引:22
Meyer WR; Castelbaum AJ; Somkuti S; Sagoskin AW; Doyle M; Harris JE; Lessey BA 《Human reproduction (Oxford, England)》1997,12(7):1393-1398
While in-vitro fertilization (IVF) was initially developed in women with
tubal factor infertility, recent clinical studies have suggested that the
presence of hydrosalpinges lowers implantation and pregnancy rates. We
postulated that these hydrosalpinges cause impaired endometrial
receptivity. A total of 103 women with hydrosalpinges were prospectively
evaluated, and compared with 55 infertile and 44 fertile controls. All
women had endometrial biopsies during the window of implantation, analysed
by conventional histological criteria, and also stained for three integrin
markers of endometrial receptivity (alpha1beta1, alpha4beta1 and alpha
vbeta3). Women with hydrosalpinges (cases) expressed significantly less of
the alpha vbeta3 integrin compared with controls. There was no difference
in expression of alpha1beta1 or alpha4beta1 among groups. A significantly
greater number of cases had out of phase histology and missing alpha vbeta3
(type I defects) and absent integrin expression despite normal histological
maturation (type II) defects, compared with controls. Of 20 women with
impaired endometrial receptivity who were also biopsied after hydrosalpinx
surgery, 70% demonstrated increased alpha vbeta3 expression. Seventy-seven
percent of type I and 57% of type II defects were corrected
postoperatively. Using markers of endometrial receptivity, this study
demonstrates that inflammatory hydrosalpinges have an adverse effect on
endometrial receptivity, which in some cases may be overcome by surgical
treatment of the hydrosalpinx.
相似文献
15.
Background
Genetic polymorphisms of the TCF7L2 gene are strongly associated with large increments in type 2 diabetes risk in different populations worldwide. In this study, we aimed to confirm the effect of the TCF7L2 polymorphism rs7903146 on diabetes risk in a Brazilian population and to assess the use of this genetic marker in improving diabetes risk prediction in the general population. 相似文献16.
JE Robb LA Rymaszewski HB Bentley PT Donnan 《Surgical and radiologic anatomy : SRA》1991,13(3):181-185
Summary This study investigated the effect of tilt and observer reliability on radiographic measurements of the position of a prosthetic acetabular cup in seven dry bone pelves using the teardrop as a landmark. Coronal or sagittal tilt of more than five degrees was easily recognisable and there was effectively no observer variation in the measurements up to this limit. In addition, 90 out of 100 randomly selected antero-posterior pelvic radiographs from an outpatient department were not significantly rotated and 93 demonstrated a clearly defined teardrop. Measurements about the teardrop on routine radiographs are therefore sufficiently accurate to allow assessment of prosthetic position.
La valeur du sourcil cotyloidien comme repère d'analyse radiologique
Résumé Cette étude, conduite sur 7 bassins secs, apprécie l'effet de l'inclinaison du bassin sur la qualité de l'analyse radiographique de la position d'une cupule prothétique de hanche en utilisant le sourcil cotyloïdien comme repère. Une inclinaison du bassin dans les plans coronal et sagittal est aisément détectable et il n'existe pas de variation d'analyse entre les différents observateurs en dessous de 5° d'inclinaison. De plus, sur 100 radiographies antéro-postérieures de bassin choisies au hasard dans les dossiers de consultation, 90 avaient été réalisées sans incidence particulièrement adaptée et l'on pouvait repérer facilement le sourcil sur 93% d'entre elles. Les mesures faites sur des radios de routine sont donc suffisamment précises pour permettre l'évaluation de la position d'une prothèse à partir du sourcil cotyloïdien.相似文献
17.
18.
19.
Mariah Farrell Heather Fairfield Samantha Costa Anastasia D'Amico Carolyne Falank Daniel J Brooks Michaela R Reagan 《Journal of bone and mineral research》2021,36(1):158-169
Obesity, a growing pandemic, is a risk factor for many cancers and causes increased bone marrow adipose tissue (BMAT). in vitro studies and obese animal models suggest that BMAT contributes to cancer progression, but there is a lack of preclinical models to directly test BMAT's role in cancer. Overactivation of peroxisome-proliferator-activated receptor-γ (PPARγ) can skew bone formation and resorption rates, resulting in increased BMAT and trabecular bone loss. Thiazolidinediones (eg, rosiglitazone) are anti-diabetic therapies that promote adipogenesis through PPARγ activation. We investigated if rosiglitazone increases BMAT in an immunocompromised model, commonly used in cancer research, and if these effects could be reversed by co-administering a bone anabolic agent (sclerostin-neutralizing antibody [Scl-Ab]), which has been shown to inhibit adipogenesis, using DXA, μCT, OsO4 μCT, and dynamic histomorphometry. Four weeks of rosiglitazone in female SCID Beige mice (cohort 1) significantly decreased trabecular bone volume (BV/TV) by about one-half, through increased osteoclast and suppressed osteoblast activity, and significantly increased BMAT. In cohort 2, mice were administered rosiglitazone ± Scl-Ab for 4 weeks, and then rosiglitazone was discontinued and Scl-Ab or vehicle were continued for 6 weeks. Scl-Ab significantly increased bone parameters (eg, BV/TV, N.Ob/B.Pm, and MS/BS) in both groups. Scl-Ab also overcame many negative effects of rosiglitazone (eg, effects on trabecular bone parameters, increased mineralization lag time [MLT], and decreased bone formation rate [BFR]). Interestingly, Scl-Ab significantly decreased rosiglitazone-induced BMAT in the femur, mostly due to a reduction in adipocyte size, but had a much weaker effect on tibial BMAT. These data suggest targeting sclerostin can prevent rosiglitazone-induced bone loss and reduce BM adiposity, in some, but not all BMAT locations. Collectively, our data demonstrate that rosiglitazone increases BMAT in SCID Beige mice, but concomitant changes in bone may confound its use to specifically determine BMAT's role in tumor models. © 2020 American Society for Bone and Mineral Research (ASBMR). 相似文献
20.
Natalie A. Winings Brian J. Daley Reagan W. Bollig R. Frank Roberts Jennifer Radtke R. Eric Heidel Jessica E. Taylor James C. McMillen 《The surgeon》2021,19(3):129-134
Backgroundand Purpose: Currently, dexmedetomidine versus propofol has primarily been studied in medical and cardiac surgery patients with outcomes indicating safe and effective sedation. The purpose of this study was to assess the efficacy of dexmedetomidine versus propofol for prolonged sedation in trauma and surgical patients.MethodsThis was a single-center prospective study conducted in the Trauma/Surgical Intensive Care Unit (ICU) at a Level I academic trauma center. It included patients 18 years of age or older requiring mechanical ventilation who were randomly assigned based on unit bed location to receive either dexmedetomidine or propofol. The primary outcome was duration of mechanical ventilation. Secondary outcomes included mortality; proportion of time in target sedation; incidence of delirium, hypotension, and bradycardia; and ICU and hospital length of stay (LOS).ResultsA total of 57 patients were included. Baseline characteristics were similar between groups. There was no significant difference in duration of mechanical ventilation (median [IQR]) between the dexmedetomidine (78.5[125] hours) and propofol (105[130] hours; p = 0.15) groups. There was no difference between groups in ICU mortality, ICU and hospital LOS, or incidence of delirium. Safety outcomes were also similar. Patients in the dexmedetomidine group spent a significantly greater percentage of time in target sedation (98[8] %) compared to propofol group (92[10] %; p = 0.02).ConclusionsOur results suggest that, similar to medical and cardiac surgery patients, dexmedetomidine and propofol are safe and effective sedation agents in critically ill trauma and surgical patients; however, dexmedetomidine achieves target sedation better than propofol for this specific population. 相似文献