全文获取类型
收费全文 | 204271篇 |
免费 | 4601篇 |
国内免费 | 456篇 |
专业分类
耳鼻咽喉 | 2835篇 |
儿科学 | 7758篇 |
妇产科学 | 6008篇 |
基础医学 | 26334篇 |
口腔科学 | 6109篇 |
临床医学 | 16215篇 |
内科学 | 36815篇 |
皮肤病学 | 4628篇 |
神经病学 | 12587篇 |
特种医学 | 10882篇 |
外国民族医学 | 97篇 |
外科学 | 30758篇 |
综合类 | 1176篇 |
一般理论 | 10篇 |
预防医学 | 16935篇 |
眼科学 | 4556篇 |
药学 | 14321篇 |
2篇 | |
中国医学 | 157篇 |
肿瘤学 | 11145篇 |
出版年
2018年 | 3733篇 |
2017年 | 4097篇 |
2016年 | 3398篇 |
2015年 | 5035篇 |
2014年 | 4569篇 |
2013年 | 3896篇 |
2012年 | 10438篇 |
2011年 | 5361篇 |
2010年 | 2510篇 |
2009年 | 4159篇 |
2008年 | 2644篇 |
2007年 | 3396篇 |
2006年 | 3604篇 |
2005年 | 11650篇 |
2004年 | 13133篇 |
2003年 | 8716篇 |
2002年 | 3890篇 |
2001年 | 4429篇 |
2000年 | 1763篇 |
1999年 | 5943篇 |
1998年 | 663篇 |
1996年 | 475篇 |
1992年 | 6932篇 |
1991年 | 7177篇 |
1990年 | 7419篇 |
1989年 | 7020篇 |
1988年 | 6528篇 |
1987年 | 6291篇 |
1986年 | 6017篇 |
1985年 | 5319篇 |
1984年 | 3655篇 |
1983年 | 2969篇 |
1982年 | 1089篇 |
1981年 | 815篇 |
1980年 | 884篇 |
1979年 | 3876篇 |
1978年 | 2398篇 |
1977年 | 1813篇 |
1976年 | 1594篇 |
1975年 | 2497篇 |
1974年 | 3131篇 |
1973年 | 2761篇 |
1972年 | 2773篇 |
1971年 | 2760篇 |
1970年 | 2570篇 |
1969年 | 2479篇 |
1968年 | 2253篇 |
1967年 | 2177篇 |
1966年 | 1915篇 |
1965年 | 1135篇 |
排序方式: 共有10000条查询结果,搜索用时 21 毫秒
51.
Analyzing and shaping human attentional networks. 总被引:12,自引:0,他引:12
In this paper we outline a conception of attentional networks arising from imaging studies as connections between activated brain areas carrying out localized mental operations. We consider both the areas of functional activation (nodes) and the structural (DTI) and functional connections (DCM) between them in real time (EEG, frequency analysis) as important tools in analyzing the network. The efficiency of network function involves the time course of activation of nodes and their connectivity to other areas of the network. We outline landmarks in the development of brain networks underlying executive attention from infancy and childhood. We use individual differences in network efficiency to examine genetic alleles that are related to performance. We consider how animal studies might be used to determine the genes that influence network development. Finally we indicate how training may aid in enhancing attentional networks. Our goal is to show the wide range of methods that can be used to suggest and analyze models of network function in the study of attention. 相似文献
52.
M B?ttner J Christoffel G Rimoldi W Wuttke 《Experimental and clinical endocrinology & diabetes》2006,114(2):82-90
The lack of estrogen during menopause is associated with various symptoms including osteoporosis, cardiovascular diseases, and menopausal symptoms. For many years, conventional hormone replacement therapy has been successfully used to treat these conditions. However, in light of recent studies that draw attention to potential hazards of conventional HRT, various attempts were undertaken to search for alternatives of classical HRT. Phytoestrogens are supposed to ameliorate various discomforts associated with menopause. Resveratrol (RES) is present in red wine, grapes and peanuts and has been implicated in cardioprotection and prevention of adverse side effects observed after regular HRT. As the pituitary-thyroid axis is a target of estrogen action, we first assessed the effects of E2 administration on thyroid hormone stimulating hormone releasing hormone (TRH)-induced thyroid stimulating hormone (TSH) secretion from pituitary cell cultures in vitro. Our data reveal that E2 treatment augments the TRH-induced TSH secretion. We furthermore designed a long-term study of three months to assess the effects of subcutaneous and oral administration of 17beta-estradiol (E2), as well as the actions of RES on the pituitary-thyroid axis in ovariectomized (OVX) female rats. Our results demonstrate that serum levels of 1.0 and 8.1 microM RES lead to a significant increase in total serum triiodthyronine (T3) levels. OVX induces TSHbeta mRNA in the adenohypohysis and E2 treatment attenuates this effect. Treatment of rats with subcutaneous implants of E2 does not affect the pituitary-thyroid axis, whereas orally applied E2 benzoate (E2B) increases plasma TSH and total thyroxine (T4) in OVX rats. In all animals, we could not detect changes in thyroid morphology as assessed by hematoxylin-eosin (HE) and Perjod-Acid Schiff's (PAS) staining. 相似文献
53.
Yaprak Engin-Ustün Yusuf Ustün M Mutlu Meydanli Ay?e Kafkasli 《Gynecological endocrinology》2006,22(12):676-679
AIM: To compare the effects of 17beta-estradiol given intranasally (intranasal E2) and raloxifene on serum lipid profile and fibrinogen in hypercholesterolemic postmenopausal women. METHODS: The study population consisted of 46 women after menopause. The placebo group (n = 11) was given calcium, while the intervention groups were given intranasal E2 (Aerodiol; Servier, Chambray-les-Tours, France) (n = 16) or raloxifene (Evista; Lilly SA, Madrid, Spain) (n = 19). Blood lipids and fibrinogen were compared between groups at baseline and after 3 months of treatment. RESULTS: The group receiving intranasal E2 showed a significant decrease in triglyceride levels (p<0.05) and a marked increase in high-density lipoprotein cholesterol levels (p<0.05). No changes in lipid profile were observed in the raloxifene and placebo groups. Raloxifene caused a significant decrease in fibrinogen levels (p<0.05). CONCLUSION: Intranasal E2 exerts significant effects on lipid profile in hypercholesterolemic postmenopausal women. Raloxifene has a greater impact on fibrinogen than intranasal E2 application. 相似文献
54.
Effect of leptin on the regulation of placental hormone secretion in cultured human placental cells.
Raquel Coya Pedro Martul Jaime Algorta Ma Angeles Aniel-Quiroga Ma Angeles Busturia Rosa Se?arís 《Gynecological endocrinology》2006,22(11):620-626
Placenta is an important source of leptin during pregnancy that contributes to the high plasma leptin levels in pregnant women. Leptin and its functional receptors are synthesized in trophoblast cells that, in turn, secrete gestational hormones supporting a paracrine or autocrine role for leptin in the endocrine activity of the placenta. In the present study we examined the effect of leptin on in vitro release of gestational hormones (human chorionic gonadotropin (hCG), human placental lactogen (hPL), progesterone, estrogens and testosterone) by human term placental cells in culture. Placentas at term were obtained immediately after delivery from mothers with uncomplicated pregnancies. Progesterone, hCG, hPL, estradiol, estrone, estriol and testosterone levels were measured by different assays in culture media of cells maintained in monolayer culture after incubation for 12, 24, 48 or 72 h with leptin or placebo. Incubation with leptin did not modify hCG, hPL, progesterone, estriol and estrone secretion for any of the doses and times assayed. However, leptin led to a dose-dependent decrease in estradiol release. This effect was observed when treatment with recombinant human leptin spanned from 12 to 72 h. At this time an increase in testosterone levels was observed in leptin-treated cells versus placebo. These results indicate that leptin can be considered a gestational hormone implied in the endocrine function of the placenta, with an important role in control of the production of steroid reproductive hormones in placental cells in vitro. 相似文献
55.
Thomas R?mer 《Gynecological endocrinology》2006,22(3):140-144
Bleeding disorders encountered during administration of hormone replacement therapy (HRT) are reviewed. The incidence of bleeding disorders is dependent on the phase of HRT and the age of the patient. In the diagnosis of these bleedings transvaginal sonography and minihysteroscopy are very important methods. Endometrial thickness can be monitored exactly by transvaginal sonography. Outpatient minihysteroscopy without anesthesia results in higher compliance to HRT after the procedure. In hormonal treatment of bleeding disorders during HRT, the sonographically supported progestogen test is very useful and can reduce endometrium thickness. Operative treatments include myoma and polyp resection as well as endometrial ablation. By these methods a high rate of bleeding-free HRT can be reached. The problem of endometrial cancer during HRT is discussed on the basis of new literature and critical statements. The review shows the importance of individual diagnostic and treatment schedules for bleeding disorders during HRT. 相似文献
56.
57.
Grazyna Bednarek-Tupikowska Alicja Filus Justyna Kuliczkowska-P?aksej Krzysztof Tupikowski Anna Bohdanowicz-Pawlak Andrzej Milewicz 《Gynecological endocrinology》2006,22(4):207-212
AIM: The aim of the present study was to investigate the influence of endogenous estradiol and estrogen and estrogen-progestin therapies on concentration in pre- and postmenopausal women. MATERIALS AND METHODS: The study groups consisted of 26 women with surgical menopause (mean+/-standard deviation (SD): age 51.8+/-2.6 years, body mass index (BMI) 26.45+/-4.56 kg/m(2)), 54 with natural menopause (mean+/-SD: age 50.5+/-3.0 years, BMI 25.75+/-4.09 kg/m(2)) and 40 premenopausal controls (mean+/-SD: age 48.3+/-2.3 years, BMI 26.23+/-4.12 kg/m(2)). The group with surgical menopause received estradiol transdermally (50 microg/day) and those with natural menopause received additionally medroxyprogesterone acetate (5 mg/day) for the last 12 days of the cycle. Before and after 4 months of therapy, body weight, waist and hip circumferences and blood pressure were measured, and BMI and waist-to-hip ratio (WHR) were calculated. Serum leptin, follicle-stimulating hormone (FSH), estradiol (E(2)), testosterone, prolactin and dehydroepiandrosterone sulfate (DHEAS) were measured prior to and after treatment. RESULTS: Leptin concentrations did not differ statistically among the groups. No correlations between leptin and E(2), FSH, prolactin, testosterone and DHEAS concentrations were found in any of the groups before and after treatment. Leptin level correlated positively with body mass, BMI and hip and waist circumferences in all groups. There were no correlations between leptin and WHR in the pre- and postmenopausal groups. In the premenopausal group and in some postmenopausal groups, serum leptin level correlated with blood pressure. CONCLUSIONS: Endogenous E(2) and androgens in premenopausal women and estrogen and estrogen-progestin therapies in postmenopausal subjects do not influence serum leptin concentrations. Leptin level is related to body mass and BMI, but not to sex hormone status. The distribution of adipose tissue and the type of obesity (android or gynoid) have no influence on serum leptin concentration. The correlation between serum leptin level and blood pressure requires further investigation. 相似文献
58.
Riitta Suhonen Maritta V?lim?ki Jouko Katajisto Helena Leino-Kilpi 《Journal of Professional Nursing》2006,22(4):253-261
The purposes of this study were to examine how hospital patients' backgrounds and clinical illness are related to their perceptions of the individualized care they receive and to test the sensitivity of the Individualized Care Scale (ICS). Cross-sectional explorative survey data were obtained using questionnaires completed by 861 (response rate = 88%) predischarge hospital patients from six hospitals in Southern Finland in 2004. Self-administered questionnaires included the ICS as well as the 15D, a measure of health-related quality of life, and gathered information about the patients' backgrounds. Based on association tests, younger age, poorer state of health, and higher level of education were associated with more critical perceptions of individualized care. Using simultaneous regression analysis and presenting the results from stronger to weaker, we found age to be the strongest predictor of patients' positive perceptions of the individualized care they received. This was followed by health-related quality of life (HRQoL) as measured by the 15D, vocational education, and type of admission. The ICS was found to be a valid tool for the measurement of individualized care in hospitals. The self-reported patient data from this survey suggest that some patient characteristics are associated with the patients' perceptions about the individualized care they receive. There is now a need to consider how these characteristics can be taken into account in nursing care delivery to increase individualized care for hospital patients. The results also support use of the ICS in the measurement of individualized care in hospitals. 相似文献
59.
Micha? Panasiuk Marek Synder Maryla Drynkowska-Panasiuk Oktawiusz Bończak 《Chirurgia narzadów ruchu i ortopedia polska》2006,71(4):265-267
Serum levels of bone markers N-mid osteocalcin (OCN-Mid) and Cross-Laps in 20 patients (8 men and 12 women) with loosening of at least one element of total hip endoprosthesis confirmed during operation were compared with age and sex matched group with OA. Marker levels were measured by direct chemoluminescency using Modular E-170. Statistical analysis were done with t-Student test (alpha = 0.05). There were no significant differences in OCN-Mid, Cross-Laps levels and OCN-Mid/Cross-Laps ratio between both groups. Implant loosening is a slow process taking place on a relatively small surface in comparison to whole skeleton, so bone markers have no clinical value in diagnostics of total hip loosening. 相似文献
60.
Jorge Guardado Carlos Cotrim Otília Sim?es Sofia Almeida Mário Ialá Luís Lopes Hélder Pereira Manuel Carrageta 《Revista portuguesa de cardiologia》2006,25(4):409-415
INTRODUCTION: Transesophageal echocardiography (TEE) has become increasingly useful in the study of patients with suspected pulmonary thromboembolism. OBJECTIVE: The aim of this study was to prospectively evaluate the usefulness of TEE in the study of the distal part of the left pulmonary artery (LPA) as well as the influence of this procedure on total echocardiographic exam duration. METHODOLOGY: A prospective study in two groups of consecutive patients referred for TEE with a one- year interval between evaluation of Group A: 33 patients, 17 male, mean age 54 +/- 24 years, and Group B: 42 patients, 20 male, mean age 48 +/- 27 years (p = NS). The procedure was considered long when it took more than 3 min to evaluate the distal part of the LPA. RESULTS: In group A we were able to visualize the distal part of the LPA in 24 patients (73%) without significant prolongation of total exam duration in 16 patients (48% of group A). In one of the patients with suspected pulmonary thromboembolism thrombi were only observed in the distal part of the LPA. In group B we were able to visualize the distal part of the LPA in 36 patients (86%) without significant prolongation of total exam duration in 26 patients (61% of group B). CONCLUSIONS: 1. Visualization of the distal part of the LPA was possible in more patients, and with TEE time prolongation in less patients, in group B. These differences can be accounted for by the training of the operator in this technique. 2. The importance of visualization of this part of the LPA in guiding treatment in the subset of patients with pulmonary thromboembolism confirms the usefulness of this specific procedure. 相似文献