全文获取类型
收费全文 | 1825篇 |
免费 | 93篇 |
国内免费 | 6篇 |
专业分类
耳鼻咽喉 | 18篇 |
儿科学 | 77篇 |
妇产科学 | 45篇 |
基础医学 | 328篇 |
口腔科学 | 8篇 |
临床医学 | 88篇 |
内科学 | 264篇 |
皮肤病学 | 25篇 |
神经病学 | 122篇 |
特种医学 | 78篇 |
外科学 | 296篇 |
综合类 | 15篇 |
预防医学 | 70篇 |
眼科学 | 5篇 |
药学 | 164篇 |
中国医学 | 8篇 |
肿瘤学 | 313篇 |
出版年
2023年 | 10篇 |
2022年 | 23篇 |
2021年 | 39篇 |
2020年 | 19篇 |
2019年 | 39篇 |
2018年 | 27篇 |
2017年 | 34篇 |
2016年 | 32篇 |
2015年 | 33篇 |
2014年 | 40篇 |
2013年 | 50篇 |
2012年 | 105篇 |
2011年 | 95篇 |
2010年 | 69篇 |
2009年 | 53篇 |
2008年 | 85篇 |
2007年 | 109篇 |
2006年 | 107篇 |
2005年 | 89篇 |
2004年 | 99篇 |
2003年 | 97篇 |
2002年 | 89篇 |
2001年 | 58篇 |
2000年 | 57篇 |
1999年 | 37篇 |
1998年 | 29篇 |
1997年 | 29篇 |
1996年 | 30篇 |
1995年 | 22篇 |
1994年 | 29篇 |
1993年 | 11篇 |
1992年 | 28篇 |
1991年 | 26篇 |
1990年 | 25篇 |
1989年 | 19篇 |
1988年 | 19篇 |
1987年 | 21篇 |
1986年 | 27篇 |
1985年 | 23篇 |
1984年 | 20篇 |
1983年 | 10篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1972年 | 5篇 |
1971年 | 4篇 |
1969年 | 4篇 |
排序方式: 共有1924条查询结果,搜索用时 12 毫秒
1.
BACKGROUND: Optimal feeding practice in the first year of life is crucial for the survival and health of infants, and has long-term consequences in later life. However, non-optimal feeding practices exist widely. The present study aims to explore various constraints to optimal feeding practices in the first year of life of infants in urban areas of Beijing, China. METHODS: A cross-sectional study was conducted in urban areas of Beijing from 4 July to 20 August, 1998. Two hundred and fifty-one mothers of infants aged 6-12 months were chosen from six child health centers in three different urban districts in Beijing. A self-administered structured questionnaire was used to collect data regarding feeding practices and potentially related factors. RESULTS: Feeding practice for most of the infants was in accordance with the national and international recommendations. However, the rate of incidence of exclusive breast-feeding at 3 months of age was lower than that recommended by the World Health Organisation (WHO) (55.8%), and the introduction of solid/semisolid food before 4 months of age was found in approximately 19.3% of the infants. Cow's milk was given to 21.2% of infants from 6 months of age as the sole source of milk or as a supplement. Maternal education level (OR = 2.44, 95% CI: 1.42-4.19, P < 0.05), employment (OR = 2.05, 95% CI: 1.13-3.74, P < 0.05) and antenatal nonexclusive breast-feeding plans (OR = 4.10, 95% CI: 2.24-7.50, P < 0.001) were found to be correlated to inappropriate feeding practices. CONCLUSIONS: The feeding practices for most of the urban infants was found to be in accordance with the Chinese government and WHO recommendations; however, non-optimal feeding practices presenting as the early cessation of breast-feeding and the introduction of solid/semisolid foods existed. Information regarding optimal feeding practices should be disseminated to mothers and medical professionals in China, to ensure optimal infant health. 相似文献
2.
Nobuyuki Oka Teruaki Kawasaki Kotaro Mizutani Hiroshi Sugiyama Ichiro Akiguchi 《Neuropathology》2007,27(6):509-515
Neuromuscular biopsy is still an essential method for diagnosing vasculitic neuropathy, although its diagnostic sensitivity is at most 60%. Our objective was to examine the expression of hypoxia‐inducible factor 1α (HIF‐1α) in peripheral nerves and to evaluate its usefulness in diagnosing vasculitic neuropathy, especially for discrimination from other axonal neuropathies. Forty‐one patients with vasculitic neuropathy consisting of 20 definite, 14 probable and seven possible diagnoses, 15 patients with metabolic neuropathy, five with motor neuron disease and six with chronic inflammatory demyelinating polyneuropathy were included. Nerve biopsy specimens were immunohistochemically examined for HIF‐1α and various cell markers. Distinct immunoreactivity (IR) was observed in nuclei of endoneurial cells in 54% (22/41) of vasculitic patients, while specimens from metabolic neuropathies showed less nuclear IR and the difference of mean density of HIF‐1α‐positive nuclei was significant. Two patients with possible vasculitis who showed HIF‐1α‐positive nuclei in endoneurium, were later confirmed to have vasculitis by skin biopsies. Most of the cells expressing HIF were demonstrated to be Schwann cells. There was a trend in the vasculitic patients with early phase nerve damage to display higher endoneurial HIF‐1α‐IR. HIF‐1α may be an immunohistochemical marker for vasculitic neuropathy, especially when the observed section contains no vasculitic lesions. 相似文献
3.
We performed a chromosome analysis of 26 pediatric brain tumors, including 20 primitive neuroectodermal tumors (PNETs), 5 astrocytomas, and I immature teratoma. Specimens were treated with collagenase, placed in overnight or short-term cultures, and harvested for chromosome analysis. Numerical and/or structural abnormalities were noted in 14 of the 20 PNETs and 4 of the 5 astrocytomas. In 13 PNETs, so-called medulloblastoma in the cerebellum, an i(17q) was the most frequent structural abnormality, accounting for 30% (4/13). Double minute chromosomes (dmin) were observed in one tumor. Near-diploidy was demonstrated in three of these PNETs, hyperdiploidy in three, and near-tetraploidy in three. We could not find any correlation of these cytogenetic findings with the prognosis. In the remaining seven PNETs other than medulloblastoma, the karyotypes of five PNETs demonstrated a variety of numerical and structural abnormalities. As to the astrocytomas, losses of chromosomes 7 and 9 with dmin were observed in two, and structural abnormalities of chromosomes 1 and 17 were also observed in two tumors. In our limited cases, however, we could not find the same chromosome abnormalities that are well known in adult astrocytomas. A congenital immature teratoma showed hyperdiploidy with increased numbers of chromosomes 3, 6, and 12. We conclude that i(17q) is an important chromosome abnormality in medulloblastomas, and that the oncogenesis of pediatric astrocytomas might be different cytogenetically from that of adult astrocytomas. 相似文献
4.
5.
Teruo Iwasaki Katsuhiro Nakagawa Motoaki Yasukawa Hiroyuki Shiono Teruaki Nagano Kunimitsu Kawahara 《The Japanese Journal of Thoracic and Cardiovascular Surgery》2006,54(1):35-39
Ectopic cervical or cervico-mediastinal thymomas are very rare and most of them are asymptomatic, except for the presence
of a cervical mass. We present the case of a 71-year-old man with an ectopic cervico-mediastinal thymoma threatening superior
vena cava syndrome. He had a slight headache and presented with venous dilatation on the chest wall. A computed tomographic
scan and magnetic resonance, imaging of the chest demonstrated a mass extending from the right neck to the hilum, that indented
the trachea and compressed and displaced the brachiocephalic veins anteriorly. Under a right hemicollar incision and median
sternotomy, the mass was resected en bloc together with the thymus. The resected specimen was an encapsulated mass measuring 11×7×4 cm. The pathological diagnosis
was type AB, non-invasive thymoma, confirmed by 3-color flow, cytometry of tumor-derived lymphocytes. Flow cytometry using
biopsy material may contribute to the preoperative diagnosis of ectopic thymoma. 相似文献
6.
Takehiko Shimoyama Katsuo Yoshiya Yasushi Yamato Teruaki Koike Keiichi Honma 《General thoracic and cardiovascular surgery》2009,57(6):310-314
Malignant peripheral nerve sheath tumors (MPNSTs; malignant schwannomas) rarely occur in the anterior mediastinum, and their
prognosis is poor. A 75-year-old man was referred to our hospital for examination of an anterior mediastinal tumor. A computed
tomography-guided percutaneous needle biopsy revealed only fibrosis. The tumor was completely excised via a median sternotomy
with partial resection of the pericardium and right upper lobe of the lung. Thereafter, the tumor was diagnosed as a storiform-pleomorphic
type of malignant fibrous histiocytoma. At 1 year after the surgery, a distant metastasis was found in the interlobular space
between the right middle and lower lobes. The tumor was completely excised via a right posterolateral thoracotomy. Reexamination
of the primary and secondary tumors revealed an MPNST. No recurrence was found up to 5 years after the second surgery without
adjuvant chemotherapy or radiation therapy. However, he died from multiple lung metastases after 6 years. 相似文献
7.
8.
Nishimura T Nishida N Itoh T Komeda T Fukuda Y Ikai I Yamaoka Y Nakao K 《Genes, chromosomes & cancer》2005,42(1):34-43
Recurrent chromosomal gain at 1q is one of the most common features of human hepatocellular carcinoma (HCC), but how the gain at 1q contributes to hepatocarcinogenesis is still unclear. To identify the target genes, precise determination of the shortest region of overlap (SRO) and of breakpoints is necessary. Similarly, the role of loss at 1p, which is also a major cytogenetic aberration in HCC, needs to be determined. Fifty HCCs were examined with the aid of 59 microsatellite markers distributed throughout both arms of chromosome 1. To detect allelic gain effectively, the cutoff value of the allelic imbalance index was set at 0.70. Alleles showing imbalance were subjected to multiplex PCR, using a retained allele as an internal control, to determine whether the imbalance was the result of chromosomal gain or loss. The SRO of the gains was defined as D1S2878-D1S2619 (1q23.-q25.3, 16.9 Mb), which involved 36 cases (72%). Gains in the number of copies of certain oncogenes within this region seemed to be critical for the pathogenesis of HCC. In contrast, the centromeric breakpoints of these gains varied, but they tended to occur mainly in the pericentromeric region (26 of 50 cases, 52%). Rearrangement of specific genes associated with the gains is unlikely. On the other hand, the SRO of deletion was defined as D1S2893-D1S450 (1p36.32-p36.22, 5.1 Mb). Four known putative tumor-suppressor genes (TP73, RIZ1, NBL1/DAN, and CDKN2C) were outside the SRO, suggesting the presence of other candidate genes with critical roles in hepatocarcinogenesis. 相似文献
9.
Characterization of htAKR, a novel gene product in the aldo-keto reductase family specifically expressed in human testis 总被引:1,自引:0,他引:1
Azuma Y Nishinaka T Ushijima S Soh J Katsuyama M Lu HP Kawata M Yabe-Nishimura C Miki T 《Molecular human reproduction》2004,10(7):527-533
In human testis, expression of a novel member of the aldo-keto reductase family was identified. Based on its testis-specific expression, we termed this protein human testis aldo-keto reductase (htAKR). In addition to four major isoforms, the existence of multiple alternatively spliced products of htAKR was detected using RT-PCR followed by nested PCR. htAKR was a homologue of mouse liver keto-reductase, AKR1E1, with close similarity in their genomic organizations. htAKR4, the longest isoform, was expressed as a non-fused native form. It exhibited a limited activity toward 9,10-phenanthrenequinone, while no activity toward the steroids or prostaglandins was demonstrated. Using the laser capture microdissection technique and RT-PCR, expression of htAKR was detected in testicular germ cells as well as in interstitial cells. The levels of htAKR mRNA in the tissues obtained from seminoma were much lower than those in normal testes. A significant decline in the htAKR expression was observed when NEC8, a cell line originated from a human testicular germ cell tumour, was exposed to phorbol 12-myristate 13-acetate or 5alpha-dihydrotestosterone. These results indicate that the expression of htAKR, down-regulated in the testicular tumour, is possibly controlled by mitogenic and hormonal signals. 相似文献
10.
Ikeda T 《Parasitology research》2004,94(5):329-331
The inhibitory effects of various ion channel blockers were examined on in vitro excystment of Paragonimus ohirai metacercariae induced by a bile salt, sodium cholate. At a concentration of 10 µM, bepridil, a non-selective Ca2+ channel blocker, completely inhibited in vitro excystment, whereas TEA, lidocaine, and R(+)-IAA-94, channel blockers against K+, Na+ and Cl– ions, respectively, benzamil, an Na+/H+ and Na+/Ca2+ ion exchanger blocker, and R(+)-DIOA, a [K+, Cl–] cotransporter inhibitor, did not. Considering the previous result that Ca2+ ionophores are also efficient inducing factors for in vitro excystment of P. ohirai metacercariae and the present result, bile salts appear to induce the excystment of P. ohirai metacercariae through evoking the Ca2+ channels of target cells within the metacercarial juveniles. 相似文献