全文获取类型
收费全文 | 26143篇 |
免费 | 2112篇 |
国内免费 | 749篇 |
专业分类
耳鼻咽喉 | 198篇 |
儿科学 | 719篇 |
妇产科学 | 3714篇 |
基础医学 | 3091篇 |
口腔科学 | 270篇 |
临床医学 | 1943篇 |
内科学 | 1476篇 |
皮肤病学 | 257篇 |
神经病学 | 916篇 |
特种医学 | 1131篇 |
外国民族医学 | 20篇 |
外科学 | 2177篇 |
综合类 | 3807篇 |
现状与发展 | 4篇 |
预防医学 | 922篇 |
眼科学 | 158篇 |
药学 | 1325篇 |
18篇 | |
中国医学 | 627篇 |
肿瘤学 | 6231篇 |
出版年
2024年 | 72篇 |
2023年 | 390篇 |
2022年 | 800篇 |
2021年 | 1130篇 |
2020年 | 924篇 |
2019年 | 802篇 |
2018年 | 796篇 |
2017年 | 954篇 |
2016年 | 1057篇 |
2015年 | 1040篇 |
2014年 | 1696篇 |
2013年 | 1860篇 |
2012年 | 1413篇 |
2011年 | 1462篇 |
2010年 | 1194篇 |
2009年 | 1141篇 |
2008年 | 1289篇 |
2007年 | 1236篇 |
2006年 | 1235篇 |
2005年 | 1085篇 |
2004年 | 877篇 |
2003年 | 766篇 |
2002年 | 642篇 |
2001年 | 573篇 |
2000年 | 503篇 |
1999年 | 385篇 |
1998年 | 371篇 |
1997年 | 331篇 |
1996年 | 342篇 |
1995年 | 303篇 |
1994年 | 295篇 |
1993年 | 217篇 |
1992年 | 196篇 |
1991年 | 194篇 |
1990年 | 162篇 |
1989年 | 144篇 |
1988年 | 128篇 |
1987年 | 103篇 |
1986年 | 105篇 |
1985年 | 122篇 |
1984年 | 117篇 |
1983年 | 71篇 |
1982年 | 86篇 |
1981年 | 95篇 |
1980年 | 77篇 |
1979年 | 69篇 |
1978年 | 49篇 |
1977年 | 44篇 |
1976年 | 33篇 |
1975年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
S. Shibata 《Acta neuropathologica》1989,78(6):561-571
Summary Changes in capillary walls between human glial, non-glial and metastatic brain tumors were studied with conventional ultrathin section and freeze-fracture replica techniques. The following results were obtained. (1) In glial tumors, ultrathin section studies showed cell junctions of the capillaries were either short or elongate. Moreover, endothelial hyperplasia, surface infolding of endothelial cells, irregularity of the basal lamina and a large extravascular space were observed. Freeze-fracture replicas of capillary endothelium showed tight junctions as two to seven strands. In addition, pinocytotic vesicles had increased markedly and were an average of 25 per m2. Both ultrathin and freeze fracture studies showed that, in contrast to malignant gliomas, there were only slight changes in benign astrocytomas. (2) In non-glial tumors, ultrathin sections showed surface infoldings, increased vesicles, many fenestrations of endothelial cells, irregularity of basal lamina and enlarged perivascular space. Freeze-fracture replicas of vascular endothelium, showed that the average number of pinocytotic vesicles and fenestrations were 25 and 22 per m2, respectively. Moreover, the tight junction was composed of one or two strands which appeared to be a discontinuous array of particles. (3) In metastatic brain tumors, ultrathin studies showed capillary endothelia were proliferated, had marked infolding, and showed an increased number of pinocytotic vesicles and many fenestrations. Moreover, short and elongate intercellular junctions were presented but no open junction was detected. Finally the basal lamina lost its three-layered appearance and was irregular in width. Freeze-fracture replicas showed pinocytotic vesicles had increased and were 24 per m2 on average in four cases, but fenestrations and tight junctions could not be detected. The most fundamental feature of vessels in these three different kinds of tumors was whether they were fenestrated or not. Glial tumors were non-fenestrated, whereas non-glial and metastatic tumors were fenestrated. 相似文献
92.
93.
94.
Carmina E.; Gentzschein E.; Stanczyk F.Z.; Lobo R.A. 《Human reproduction (Oxford, England)》1995,10(2):299-303
Serum C19 conjugates, specifically 3-androstanediol glucuronide(3G), reflect peripheral androgen action through the actionof 5-reductase activity. The origin of 5-reduced C19 conjugateshas been controversial and it has been suggested that they arederived primarily from adrenal androgens. We examined concentrationsof 3G, 3-androstanediol sulphate (3S), androsterone glucuronide(AoG) and androsterone sulphate (AoS) in 40 hirsute hyperandrogenicwomen. These patients were divided into four groups based uponindividual, combined or normal concentrations of the adrenalandrogens dehydroepiandrosterone (DHEAS) and 11-hydroxy-androstenedione.Testosterone, unbound testosterone and androstenedione weresimilar in these groups. Serum 3G was equally high in all groupsand was correlated significantly with hirsutism, while the otherconjugates were not. Androsterone glucuronide was raised inall groups but was higher in patients with raised DHEAS. Serum3S was raised in all groups and was higher where both adrenalandrogens were raised. Serum AoS was highly correlated withDHEAS. Serum 3G was correlated with unbound testosterone andandrostenedione but not with the adrenal androgens. The glucuronideconjugates were correlated with one another as were the sulphateconjugates but glucuronides and sulphates were not correlated.These data confirm ovarian and adrenal dependency of C19 conjugates.Serum 3G appears to reflect hirsutism most accurately and isleast dependent on adrenal androgens in patients with mixedhyperandrogenism. 相似文献
95.
Classification of Breast Masses Using Selected Shape,Edge-sharpness,and Texture Features with Linear and Kernel-based Classifiers 总被引:2,自引:0,他引:2
Breast masses due to benign disease and malignant tumors related to breast cancer differ in terms of shape, edge-sharpness, and texture characteristics. In this study, we evaluate a set of 22 features including 5 shape factors, 3 edge-sharpness measures, and 14 texture features computed from 111 regions in mammograms, with 46 regions related to malignant tumors and 65 to benign masses. Feature selection is performed by a genetic algorithm based on several criteria, such as alignment of the kernel with the target function, class separability, and normalized distance. Fisher's linear discriminant analysis, the support vector machine (SVM), and our strict two-surface proximal (S2SP) classifier, as well as their corresponding kernel-based nonlinear versions, are used in the classification task with the selected features. The nonlinear classification performance of kernel Fisher's discriminant analysis, SVM, and S2SP, with the Gaussian kernel, reached 0.95 in terms of the area under the receiver operating characteristics curve. The results indicate that improvement in classification accuracy may be gained by using selected combinations of shape, edge-sharpness, and texture features. 相似文献
96.
97.
Mulders AG Laven JS Eijkemans MJ de Jong FH Themmen AP Fauser BC 《Human reproduction (Oxford, England)》2004,19(9):2036-2042
BACKGROUND: Anti-Müllerian hormone (AMH), produced by growing pre-antral and early antral ovarian follicles, has been shown to be a useful marker for ovarian ageing. Serum AMH concentrations are elevated during reproductive life in anovulatory women, especially in those patients exhibiting polycystic ovaries (PCO). The current study was designed to investigate whether the decrease in AMH serum concentrations over time is different comparing women with normogonadotrophic anovulation [World Health Organization (WHO) group 2 (including polycystic ovary syndrome (PCOS)] and normo-ovulatory controls. METHODS AND RESULTS: AMH serum levels were assessed on two occasions in 98 patients suffering from WHO 2 anovulatory infertility as well as in 41 normo-ovulatory premenopausal women. Median time interval between both visits was 2.6 years (range 0.3-9.0) for WHO 2 patients compared with 1.6 years (range 1.0-7.3) in controls. Serum AMH concentrations were significantly (P < 0.0001) elevated on both occasions in WHO 2 patients (AMH1, median = 7.5 microg/l, range 0.1-35.8; and AMH2, median = 6.7 microg/l, range 0.0-30.6) compared with controls (AMH1, median = 2.1 microg/l, range 0.1-7.4; and AMH2, median = 1.3 microg/l, range 0.0-5.0). Regression analysis, corrected for age, indicated a significant relative decrease in serum AMH concentrations over time for both groups (P < 0.001). However, the decline in serum AMH in WHO 2 patients was significantly less compared with controls (P = 0.03). CONCLUSION: The present longitudinal study shows that serum AMH concentrations decrease over time both in women presenting with WHO 2 anovulatory infertility and in normo-ovulatory controls. The decrease in WHO 2 patients is less pronounced despite distinctly elevated concentrations. This observation may suggest retarded ovarian ageing and hence a sustained reproductive life span in these patients. 相似文献
98.
IVF/ICSI outcome and serum LH concentration on day 1 of ovarian stimulation with recombinant FSH under pituitary suppression 总被引:3,自引:0,他引:3
Bjercke S Fedorcsak P Abyholm T Storeng R Ertzeid G Oldereid N Omland A Tanbo T 《Human reproduction (Oxford, England)》2005,20(9):2441-2447
BACKGROUND: Down-regulation with GnRH agonist has been suggested to result in a profound suppression of LH bioactivity, reduced estradiol synthesis, and thus impaired IVF and pregnancy outcome. The aims of this study were: (i) to assess the usefulness of serum LH measurement on stimulation day 1 as a predictor of ovarian response, conception and pregnancy outcome in patients treated with long-term down-regulation with GnRH agonist and recombinant FSH, and (ii) to define the best threshold LH value, if any, to discriminate between women with different outcomes of IVF. METHODS: Records of 2625 cycles in 1652 infertile women undergoing IVF (n = 1856) and/or ICSI (n = 769) treatment were reviewed. RESULTS: The range of LH concentrations on stimulation day 1 overlapped among non-conception cycles, conception cycles, ongoing pregnancies and early pregnancy losses. Receiver operating characteristic (ROC) analysis showed that serum LH concentrations on stimulation day 1 were unable to discriminate between conception and non-conception cycles (AUC(ROC) = 0.51; 95% CI: 0.49-0.54) or ongoing pregnancies versus early pregnancy loss groups (AUC(ROC) = 0.52; 95% CI: 0.47-0.57). Stratification for various low serum levels of LH did not reveal significant differences with respect to conception or pregnancy outcome among different LH levels on stimulation day 1. CONCLUSIONS: Serum LH concentration on stimulation day 1 cannot predict ovarian response, conception and pregnancy outcome in women receiving long-term down-regulation during assisted reproduction treatment. 相似文献
99.
The CA 125 tumour-associated antigen: a review of the literature 总被引:11,自引:1,他引:11
CA 125 is an antigenic determinant on a high-molecular-weight glycoprotein recognized by a monoclonal antibody which was raised using an ovarian cancer cell line as an immunogen. During the last 5 years the studies reviewed in this paper have provided information concerning the nature, distribution and clinical significance of CA 125. The CA 125 determinant is expressed by epithelial ovarian tumours and various other pathological and normal tissues of Müllerian origin. The function of the glycoprotein expressing CA 125 remains unclear but the distribution of the antigen suggests that it may have a physiological role. The highest serum levels of CA 125 are found in ovarian cancer patients, but elevation of serum CA 125 may also be associated with other malignancies and benign and physiological states, including pregnancy, endometriosis and menstruation. Despite limitations of sensitivity and specificity serum CA 125 estimation is of clinical value in the pre-operative diagnosis and monitoring of ovarian malignancy and may be a prognostic indicator for this disease. The role of CA 125 in screening for early-stage ovarian cancer is currently under investigation. Recent reports suggest that serum CA 125 measurement may also be of value as a prognostic indicator in endometrial cancer and as a reflection of disease status in advanced endometriosis. 相似文献
100.
Clinical stage I seminomas are effectively treated with surgery raising concerns as to when to give adjuvant radiation therapy given the risk of secondary malignancies. A recent randomized trial found tumor size and rete testis invasion to be the strongest predictors of relapse in clinical stage I seminomas. These 2 parameters may be surrogate measures of tumor volume. Intertubular seminoma (ITS) of the testis describes the presence of neoplastic germ cells within the interstitium of the testis. These cells are detected away from the main macroscopic mass. Because ITS can infiltrate in a 3-dimensional fashion, it may also represent a measure of tumor volume not usually noted in standard pathology reporting. The goal of this study was to determine the incidence of ITS in pure seminomas and its association with other prognostic parameters. One hundred twenty consecutive pure seminomas surgically removed between 1998 and 2003 were evaluated. ITS was defined as the presence of an interstitial or intertubular growth pattern of tumor cells, which was noncontiguous with the main tumor and present at least 3 high-power fields away from the tumor mass. The average tumor size was 3.4 cm. Of the entire cohort of patients, which included pathological stages T1 through T3, 11% had invasion through the tunica albuginea, 51% had rete testis invasion, 51% had lymphovascular invasion, 93% had associated intratubular germ-cell neoplasia, and 36% had ITS. ITS was significantly associated with rete testis invasion ( P = .001). Logistic regression analysis looking at ITS, tumor size, patient age, and lymphovascular invasion revealed that only ITS was associated with rete testis invasion (RR, 4.1, P < .0001). ITS is present in a significant proportion of pure seminomas and has a significant association with rete testis invasion. The presence of ITS may therefore be an important prognostic factor, not only because it alters the calculated size of the tumor but also because it has an association with rete testis invasion. 相似文献