全文获取类型
收费全文 | 8597篇 |
免费 | 535篇 |
国内免费 | 49篇 |
专业分类
耳鼻咽喉 | 55篇 |
儿科学 | 131篇 |
妇产科学 | 158篇 |
基础医学 | 1232篇 |
口腔科学 | 373篇 |
临床医学 | 931篇 |
内科学 | 1890篇 |
皮肤病学 | 161篇 |
神经病学 | 725篇 |
特种医学 | 305篇 |
外科学 | 1270篇 |
综合类 | 53篇 |
一般理论 | 4篇 |
预防医学 | 525篇 |
眼科学 | 161篇 |
药学 | 714篇 |
中国医学 | 19篇 |
肿瘤学 | 474篇 |
出版年
2023年 | 67篇 |
2022年 | 142篇 |
2021年 | 190篇 |
2020年 | 130篇 |
2019年 | 187篇 |
2018年 | 177篇 |
2017年 | 195篇 |
2016年 | 203篇 |
2015年 | 222篇 |
2014年 | 323篇 |
2013年 | 326篇 |
2012年 | 560篇 |
2011年 | 576篇 |
2010年 | 302篇 |
2009年 | 292篇 |
2008年 | 511篇 |
2007年 | 506篇 |
2006年 | 505篇 |
2005年 | 494篇 |
2004年 | 444篇 |
2003年 | 433篇 |
2002年 | 406篇 |
2001年 | 128篇 |
2000年 | 99篇 |
1999年 | 90篇 |
1998年 | 102篇 |
1997年 | 85篇 |
1996年 | 82篇 |
1995年 | 68篇 |
1994年 | 56篇 |
1993年 | 43篇 |
1992年 | 63篇 |
1991年 | 74篇 |
1990年 | 64篇 |
1989年 | 77篇 |
1988年 | 54篇 |
1987年 | 60篇 |
1986年 | 52篇 |
1985年 | 52篇 |
1984年 | 41篇 |
1983年 | 39篇 |
1982年 | 32篇 |
1981年 | 32篇 |
1979年 | 32篇 |
1978年 | 23篇 |
1969年 | 17篇 |
1968年 | 17篇 |
1967年 | 19篇 |
1933年 | 20篇 |
1932年 | 18篇 |
排序方式: 共有9181条查询结果,搜索用时 15 毫秒
71.
The deprivation effect (DE)--an increase in the level of free-choice consumption of alcohol after a period of forced abstinence--may reflect relapselike drinking and be relevant for modeling alcohol abuse. However, the behavioral mechanisms of the DE are unclear. In these experiments, rats had unlimited free-choice access to water and saccharin-containing solutions and underwent repeated episodes of saccharin deprivation. It was found that DE magnitude correlates positively with the deprivation phase duration, expression of the DE is highly context dependent, and the DE can be prevented by extinguishing response to the saccharin-associated stimuli. Thus, DE procedures may be useful for studying the effects of continued exposure to stimuli associated with various primary reinforcers such as drugs of abuse. 相似文献
72.
Low prevalence of abdominal aortic aneurysm in hypertensive patients. A population-based study 总被引:1,自引:0,他引:1
The prevalence of abdominal aortic aneurysms (AAA) was estimated by ultrasonography in hypertensives in the age group 50-70 years in geographically defined population. Only one case of AAA was found among 245 patients. This rather unexpected result implies a probability of less than 5% that the true prevalence of AAA is as high as 2% in hypertensives. Our population-based study indicates a lower prevalence than earlier studies based on necropsies and is an example of research cooperation between primary health care and specialized hospital care. 相似文献
73.
The expression of CD45R on mouse T cells has been studied. This antigen is expressed on the two higher molecular weight bands of CD45 (or T200) and in mouse it is currently used as a marker of B cells (B220). Here we confirm that CD45R is expressed on some mouse T cell clones. We show that a small but measurable proportion of mouse spleen and peripheral blood lymphocyte T cells gives positive immunofluorescence with B220. Also CD45R-specific antibodies increase the proliferation response to phytohemagglutinin up to 3-fold, thus confirming that CD45R molecules transduce a signal into mouse T cells. 相似文献
74.
Riedl M Czech T Slootweg J Czernin S Hainfellner JA Schima W Vierhapper H Luger A 《Endocrine pathology》1995,6(2):159-166
This report describes a case of lymphocytic hypophysitis in a 63-year-old man who presented with symptoms of a pituitary mass
lesion associated with hypothyroidism and hypogonadism. Postoperative endocrinological testing demonstrated gonadotropic,
thyrotropic, and corticotropic hypopituitarism, and the patient was commenced on replacement therapy with hydrocortisone and
levothyroxine. Histological examination of the pituitary tissue obtained by transsphenoidal surgery revealed lymphocytic hypophysitis
without evidence of a pituitary adenoma. The vast majority of patients with lymphocytic hypophysitis are women particularly
during pregnancy and the puerperium. Until recently only four men were reported in the literature. The pathogenesis of lymphocytic
hypophysitis is uncertain but autoimmune mechanisms are possibly involved. 相似文献
75.
Hänfler J Kreuzer KA Laurisch K Rayes N Neuhaus P Schmidt CA Oettle H 《Medical microbiology and immunology》2003,192(4):197-204
Even now rare human cytomegalovirus (hCMV) reactivation is still a life-threatening complication after solid organ transplantation. Although PCR techniques are regarded as the most sensitive detection methods for hCMV, their accuracy and reproducibility are limited. This is a major disadvantage with quantitative PCR assays, which are thought to provide valuable information about hCMV latency or active viral replication in transplant patients. To enhance the diagnostic safety of quantitative hCMV PCR, we developed a duplex real-time fluorescence PCR that is capable of quantifying hCMV DNA and beta-actin DNA as internal control simultaneously within one reaction. By the use of 6-carboxyfluorescein and hexa-chloro-6-carboxyfluorescein as reporter fluorophores and 4-(4'-dimethylamino-phenylazo) benzoic acid as dark quencher dye, hCMV DNA and beta-actin DNA could be quantified in parallel in a wide linear range from 10(1) to 10(7) copies, each. To test the clinical applicability of this approach, we investigated hCMV DNA kinetics in peripheral leukocytes of three hCMV antigen-positive and four antigen-negative patients after liver transplantation, as assessed by intracellular hCMV pp65 alkaline phosphate-anti-alkaline phosphate (APAAP) complex. While all APAAP-negative individuals remained PCR negative, kinetics of HCMV DNA in leukocyte DNA samples of APAAP-positive patients correlated closely with hCMV antigen tests. Here, comparison of separate and simultaneous target quantitation revealed identical results. It is of interest that, while single hCMV antigen positivity is commonly not regarded as a reliable parameter of viral reactivation, in our study a viral load greater than 10(4) copies/2x10(5) beta-actin DNA copies clearly indicated a subsequent increase in APAAP-positive leukocytes. We conclude that with the presented method the reliability of hCMV quantitation via real-time PCR can be substantially increased and may be used to monitor hCMV kinetics in vivo. 相似文献
76.
77.
B M B?cklin A Gessbo M Forsberg A Shokrai B Rozell W Engstr?m 《Journal of clinical pathology》1998,51(1):43-47
AIM: To study how polychlorinated biphenyls (PCBs) affect fetal growth and the expression of the insulin-like growth factor (IGF II) gene in the mink (Mustela vision). METHODS: Ten female mink were each exposed to 0.65 or 1.3 mg Clophen A50/day, respectively, during the reproductive season. The numbers and sizes of viable fetuses were recorded. The expression of the IGF II gene was studied by northern blotting using a mink specific IGF II cDNA probe. RESULTS: The number of viable fetuses decreased after PCB exposure in a dose dependent fashion. Expression of the IGF II gene in adult livers from PCB exposed animals was decreased, compared with control animals, in a dose dependent fashion. In contrast, IGF II expression in placentas and fetuses was unaltered. Furthermore, the maternal excretion of urinary cortisol increased in both exposed groups during the implantation period. CONCLUSIONS: Expression of the IGF II gene is downregulated by PCB exposure in the adult liver. There is also an indication that the regulation of the expression of this gene differs between adult and fetal life. 相似文献
78.
Cytoarchitectonic delineation of areas in post-mortem human brains provides the precise location of these areas. It has been
possible to study the size and location of areas between post-mortem brains with multi-subject cytoarchitectonic data. If
the structure–function relationship is assumed to be a one-to-one mapping for the purposes of inter-subject variability, then
functional areas in the cortex will also adhere to the structure, and therefore, the location and size of cytoarchitectonic
areas in the brain. Thus, it is possible to use the cytoarchitectonic data as being representative of the size and location
of functional activations. Under this assumption, we simulated activations in cytoarchitectonic areas from ten post-mortem
brains in this study. We then treated these data as we would a normal PET experiment. The purpose of this study is to demonstrate
a standard PET image analysis on a simulated ten-subject PET study using cytoarchitecture to localize the activations. By
doing so, we simulate activations with real inter-subject variability with the size and location of each area. Significant
activations were obtained for activations simulated in areas 3a and 3b. A voxel-wise conjunction between simulated data and
experimental data was made to better determine the underlying areas activated by the experimental tasks. This study presents
a novel technique for demonstrating the effect of standard image analysis on the location and size of simulated activations
as determined by cytoarchitectonic data from multiple subjects. Furthermore, this technique has been applied to better determine
the underlying areas activated in an experiment. 相似文献
79.
Anton Brøgger Trygve Urdal Finn Brasch Larsen Nils Johan Lavik 《Clinical genetics》1977,11(4):349-358
Y chromosome variation has been studied in three groups of Norwegian males: 35 boys from an adolescent psychiatric hospital; 45 men from a hospital for hard-to-manage or dangerous, psychotic men; and 26 boys from two ordinary school classes.
Y chromosomes with 1, 2, and 3 brightly fluorescing bands were found in all three groups. One boy carried a Y with no bands. The mean values of the Yf/Yq ratio were not significantly different in the three groups (Yf is the length of the distal, brightly fluorescing part of Yq). Two cases of XY/XYY mosaicism were found among the psychotic men.
The study shows that the human species is polymorphic with regard to the size of the Y chromosome, i. e. the number of fluorescent bands in the long arm. No phenotypical manifestation of this polymorphism, particuIarly as regards behaviour, was found. 相似文献
Y chromosomes with 1, 2, and 3 brightly fluorescing bands were found in all three groups. One boy carried a Y with no bands. The mean values of the Yf/Yq ratio were not significantly different in the three groups (Yf is the length of the distal, brightly fluorescing part of Yq). Two cases of XY/XYY mosaicism were found among the psychotic men.
The study shows that the human species is polymorphic with regard to the size of the Y chromosome, i. e. the number of fluorescent bands in the long arm. No phenotypical manifestation of this polymorphism, particuIarly as regards behaviour, was found. 相似文献
80.
Transformation of the cultivated mushroom Agaricus bisporus (Lange) using T-DNA from Agrobacterium tumefaciens 总被引:4,自引:0,他引:4
Agrobacterium tumefaciens is known to transfer parts of its tumor-inducing plasmid, the T-DNA, to plants, yeasts and filamentous fungi. We have used
this system to transform germinating basidiospores and vegetative mycelium of a commercial strain of the cultivated basidiomycete
Agaricus bisporus. Analysis of transformants shows that the T-DNA integrates at random sites into the host genome and that the selection marker
is stable during mitosis and meiosis. The Agrobacterium system allows the transformation of both homokaryons and heterokaryons of A. bisporus. Also, both karyotypes of an heterokaryon can be transformed simultaneously. Furthermore, this is the first report on the
transformation of vegetative mycelium of a commercial strain of A. bisporus.
Received: 6 June 2000 / Accepted: 10 October 2000 相似文献