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   243017篇
  免费   11569篇
  国内免费   558篇
耳鼻咽喉   3186篇
儿科学   7724篇
妇产科学   4949篇
基础医学   34601篇
口腔科学   5831篇
临床医学   19486篇
内科学   53455篇
皮肤病学   6508篇
神经病学   21582篇
特种医学   7622篇
外国民族医学   104篇
外科学   30058篇
综合类   1286篇
一般理论   67篇
预防医学   21951篇
眼科学   4718篇
药学   16883篇
  4篇
中国医学   802篇
肿瘤学   14327篇
  2023年   1336篇
  2022年   1077篇
  2021年   3817篇
  2020年   2289篇
  2019年   4135篇
  2018年   7684篇
  2017年   5100篇
  2016年   5088篇
  2015年   5727篇
  2014年   6120篇
  2013年   9622篇
  2012年   16451篇
  2011年   16407篇
  2010年   8299篇
  2009年   6300篇
  2008年   14015篇
  2007年   15090篇
  2006年   13860篇
  2005年   13745篇
  2004年   12899篇
  2003年   11805篇
  2002年   11109篇
  2001年   6352篇
  2000年   6394篇
  1999年   5696篇
  1998年   1085篇
  1997年   897篇
  1996年   827篇
  1995年   744篇
  1992年   3305篇
  1991年   2966篇
  1990年   2832篇
  1989年   2594篇
  1988年   2475篇
  1987年   2271篇
  1986年   2162篇
  1985年   1939篇
  1984年   1462篇
  1983年   1233篇
  1979年   1253篇
  1978年   893篇
  1977年   839篇
  1975年   843篇
  1974年   1021篇
  1973年   1041篇
  1972年   962篇
  1971年   958篇
  1970年   891篇
  1969年   928篇
  1968年   797篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
 Three further cases of mature benign cystic teratomas of the ovary associated with virilization are added to the three previously reported in the literature. They were found in postmenopausal, obese, diabetic women aged 52, 61, and 67 years. The patients presented with hirsutism and voice changes and clitoromegaly was present in one. Testosterone and androstenedione levels were elevated but promptly regressed after removal of the tumours. Histologically, sheets of stromal luteinized cells were found peripherally at the interface between the neoplasm and ovarian tissue. Luteinization of ovarian stroma induced by an unknown factor related to diabetes mellitus is the origin of the virilization. Received: 8 January 1997 / Accepted: 28 February 1997  相似文献   
992.
We present a new marker that confers both resistance to pyrimethamine and green fluorescent protein-based fluorescence on the malarial parasite Plasmodium berghei. A single copy of the cassette integrated into the genome is sufficient to direct fluorescence in parasites throughout the life cycle, in both its mosquito and vertebrate hosts. Erythrocyte stages of the parasite that express the marker can be sorted from control parasites by flow cytometry. Pyrimethamine pressure is not necessary for maintaining the cassette in transformed parasites during their sporogonic cycle in mosquitoes, including when it is borne by a plasmid. This tool should thus prove useful in molecular studies of P. berghei, both for generating parasite variants and monitoring their behavior.  相似文献   
993.
994.
This study describes a novel type of support for GPs caring for patients dying at home: the establishment and evaluation of a telephone advisory service for GPs, run by GPs with a special interest in palliative care (GPwSIs) in the Netherlands 2000-2003. A growing number of GPs called for advice, 10% during out of hours. Prognosis of the patients was generally short (days to weeks in 70% of cases). Most advice sought by GPs concerned symptom management and on evaluation, 85% of the GPs followed the advice.  相似文献   
995.
The gene coding for Eimeria tenella protein EtMIC3 was cloned by screening a sporozoite cDNA library with two independent monoclonal antibodies raised against the oocyst stage. The deduced sequence of EtMIC3 is 988 amino acids long. The protein presents seven repeats in tandem, with four highly conserved internal repeats and three more divergent external repeats. Each repeat is characterised by a tyrosine kinase phosphorylation site, WRCY, and a reminiscent motif of the thrombospondin1 (TSP1)-type I domain, CXXXCG. The protein EtMIC3 is localised at the apex of free parasite stages. It is not detected in the early intracellular parasite stage but is synthesised in mature schizonts. Secretion of the protein is induced when sporozoites are incubated in complete medium at 41 degrees C. Strangely enough, the two independent mAb that allow cloning of EtMIC3 interfere with parasitic growth in different ways. One is able to inhibit parasite invasion whereas the other inhibits development. Expression and localisation of the protein EtMIC3 are consistent with a protein involved in the invasion process as is expected for a microneme protein.  相似文献   
996.
Summary We have characterized the ribosomal proteins from Spinacia chloroplasts using two-dimensional gel electrophoresis. The 30S and 50S subunits contain 23–25 and 36 ribosomal proteins, respectively. In contrast to prokaryotic ribosomes, chloroplast ribosomes contain at least one (and possibly two) phosphorylated ribosomal proteins. Isolated chloroplasts synthesize in the presence of (35S) labeled methionine and cysteine at least seven 30S and thirteen 50S ribosomal proteins which are assembled into (pre)ribosomes. This suggests that about one third of the chloroplast ribosomal proteins is encoded by the chloroplast DNA itself. The identity of several labeled proteins in the two-dimensional gel electrophoretic patterns which did not comigrate with stained chloroplast ribosomal proteins is discussed.Abbreviations CBB Coomassie Brilliant Blue - CHI cycloheximide - cp chloroplast - DTT dithiotreitol - EDTA ethylene diamine tetraacetate - EGTA ethylene glycol-bis (-amino ethyl ether) N,N-tetraacetic acid - kD kilodalton - LHCP light harvesting chlorophyll a/b protein - PMSF phenyl methyl sulfonyl fluoride - RuBPCase ribulose-1,5-bisphosphate carboxylase - SDS sodiumdodecylsulphate  相似文献   
997.
The authors found tardive dyskinesia (TD) in 23.5% of 200 hospitalized schizophrenic patients, most of whom had received neuroleptic treatment for at least two years. The frequency and severity of TD increased with age, and the more advanced the age at which the patient started taking neuroleptics, the more likely it was that TD would develop. Severe TD was more common in men than in women. Prolonged treatment with neuroleptics or the use of antiparkinsonism drugs increased the risk of TD.  相似文献   
998.
Spontaneous and mitomycin C(MMC)-induced sisyer chromatid exchanges were studied in 11 patients with retinoblastoma and 7 normal controls. Spontaneous rates were similar in patients and in controls. The MMC-induced rate was found to be significantly higher in bilaterally affected patients than in controls. It is suggested that this increase may be due to a DNA repair deficiency. However, it is not possible to clarify wether this abnormality is associated with the retinoblastoma gene or with another factor acting on the degree of expressivity of the disease in gene carriers.  相似文献   
999.
The energetics of middle-distance running   总被引:3,自引:0,他引:3  
Summary In order to assess the relative contribution of aerobic processes to running velocity (v), 27 male athletes were selected on the basis of their middle-distance performances over 800, 1500, 3000 or 5000 m, during the 1987 track season. To be selected for study, the average running velocity corresponding to their performances had to be superior to 90% of the best French of the season. Maximum O2 consumption and energy cost of running (C) had been measured within the 2 months preceding the track season, which, together with oxygen consumption at rest allowed us to calculate the maximalv that could be sustained under aerobic conditions: . The treadmill runningv corresponding to a blood lactate of 4 mmol·–1 (v la4), was also calculated. In the whole group, C was significantly related to height (r=–0.43;P<0.03). Neither C nor (with, in this case, the exception of the 3000 m athletes) were correlated to . On the other hand,v a max was significantly correlated to over distances longer than 800 m. These were also correlated tov la4. Howeverv la4 occurred at 87.5% SD 3.3% ofv a max, this relationship was interpreted as being an expression of the correlation betweenv a max and . Calculation ofv a max provided a useful means of analysing the performances. At the level of achievement studied, sustained over 3000 m corresponded tov a max. The shape of the relationship ofv/v a max as a function of the duration of the event raised the question of a possible change in C as a function of v during middle-distance running competitions.  相似文献   
1000.

Background

Variants in GBA are the most common genetic risk factor for Parkinson's disease (PD), and are especially prevalent in the Ashkenazi Jewish (AJ) population. However, most studies on GBA in AJ genotype only seven selected Gaucher-associated pathogenic variants rather than sequencing the whole gene, which may leave carriers of PD-associated GBA variants undiscovered.

Methods

GBA was fully sequenced using molecular inversion probes (MIPs) and Sanger sequencing in 735 AJ PD patients and 662 AJ controls, from Israel and New York. Additional AJ control data (n?=?3044) from the Inflammatory Bowel Disease Exome Portal was used.

Results

Full GBA sequencing increased the number of variants discovered by 17.4%, compared to targeted genotyping. An additional 17 PD patients were identified with GBA-associated PD. The p.E326K variant was found in 1.6% of AJ PD patients, making it the second most common PD-associated GBA variant in AJ. GBA variants were found in 18% of PD patients and 7.5% of controls (OR?=?2.7, 95%CI?=?1.9–3.8, p?<?0.0001).

Conclusion

Without full sequencing of GBA, or at minimum including p.E326K in the genotyping panel, a significant proportion of variant carriers go undiscovered and may be incorrectly assigned as non-carriers in studies or clinical trials.  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