全文获取类型
收费全文 | 12071篇 |
免费 | 768篇 |
国内免费 | 31篇 |
专业分类
耳鼻咽喉 | 165篇 |
儿科学 | 418篇 |
妇产科学 | 230篇 |
基础医学 | 1587篇 |
口腔科学 | 319篇 |
临床医学 | 1184篇 |
内科学 | 2335篇 |
皮肤病学 | 179篇 |
神经病学 | 1273篇 |
特种医学 | 336篇 |
外科学 | 1667篇 |
综合类 | 68篇 |
一般理论 | 6篇 |
预防医学 | 1032篇 |
眼科学 | 202篇 |
药学 | 922篇 |
中国医学 | 22篇 |
肿瘤学 | 925篇 |
出版年
2023年 | 59篇 |
2022年 | 91篇 |
2021年 | 164篇 |
2020年 | 166篇 |
2019年 | 208篇 |
2018年 | 254篇 |
2017年 | 216篇 |
2016年 | 234篇 |
2015年 | 261篇 |
2014年 | 333篇 |
2013年 | 603篇 |
2012年 | 729篇 |
2011年 | 732篇 |
2010年 | 426篇 |
2009年 | 411篇 |
2008年 | 699篇 |
2007年 | 703篇 |
2006年 | 740篇 |
2005年 | 682篇 |
2004年 | 638篇 |
2003年 | 619篇 |
2002年 | 596篇 |
2001年 | 165篇 |
2000年 | 132篇 |
1999年 | 178篇 |
1998年 | 146篇 |
1997年 | 132篇 |
1996年 | 121篇 |
1995年 | 137篇 |
1994年 | 108篇 |
1993年 | 111篇 |
1992年 | 129篇 |
1991年 | 133篇 |
1990年 | 97篇 |
1989年 | 102篇 |
1988年 | 107篇 |
1987年 | 98篇 |
1986年 | 90篇 |
1985年 | 124篇 |
1984年 | 118篇 |
1983年 | 94篇 |
1982年 | 108篇 |
1981年 | 88篇 |
1979年 | 87篇 |
1978年 | 64篇 |
1977年 | 78篇 |
1975年 | 55篇 |
1974年 | 58篇 |
1973年 | 48篇 |
1972年 | 54篇 |
排序方式: 共有10000条查询结果,搜索用时 19 毫秒
91.
Capillary supply of the quadriceps femoris muscle of man: adaptive response to exercise 总被引:16,自引:0,他引:16
下载免费PDF全文
![点击此处可从《The Journal of physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
1. Five subjects trained for 8 weeks on a bicycle ergometer for an average of 40 min/day, four times a week at a work load requiring 80% of the maximal oxygen uptake (V(O2 max.)). V(O2 max.) determinations were performed, and muscle biopsies from the quadriceps femoris muscle (vastus lateralis) were taken before, as well as repeatedly during, the training period. The muscle biopsies were histochemically stained for fibre-types (myofibrillar ATPase) and capillaries (amylase-PAS method), and analysed biochemically for succinate dehydrogenase and cytochrome oxidase activities.2. The training programme resulted in a 16% increase in V(O2 max.), a 20% increase in capillary density, a 20% increase in mean fibre area, and an approximately 40% increase in the activities of succinate dehydrogenase and cytochrome oxidase.3. The capillary supply to type I, IIA and IIB fibres, expressed as the mean number of capillaries in contact with each fibre-type, relative to fibre-type area, increased equally.4. The present study shows that endurance training constitutes a powerful stimulus for capillary proliferation in human skeletal muscle. 相似文献
92.
Salmonella typhimurium infection in calves: protection and survival of virulent challenge bacteria after immunization with live or inactivated vaccines. 总被引:8,自引:11,他引:8
下载免费PDF全文
![点击此处可从《Infection and immunity》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Salmonella typhimurium SL1479, an auxotrophic mutant strain having a complete block in the aromatic biosynthetic pathway and therefore requiring p-aminobenzoic acid and 2,3-dihydroxybenzoate not available in mammalian tissues, was given orally in a dose of 10(10) live bacteria to 4- to 5-week-old calves. Only a mild transient fever response was seen. Strain SL1479 was unable to colonize and persist in the calves for more than 2 weeks. In a vaccination experiment, groups of six calves were (i) orally vaccinated with the live S. typhimurium SL1479 strain, (ii) subcutaneously vaccinated with a heat-inactivated S. typhimurium SVA1232 strain with aluminum hydroxide as adjuvant, or (iii) not vaccinated, to serve as controls. Calves were orally challenged with the live, calf-virulent S. typhimurium SVA44 strain: either 10(6) bacteria (equivalent to 100 25% lethal doses [LD25S]) or 10(9) bacteria (100,000 LD25S doses). The live oral vaccine gave significantly better protection than the heat-vaccinated, subcutaneously injected vaccine since (i) only control calves and calves given the killed vaccine developed profuse diarrhea, (ii) clinically, the mild fever responses seen after challenge in calves given the live vaccine were significantly lower (P less than 0.0005), (iii) autopsies performed 21 days after the challenge infection revealed normal findings in calves given the live vaccine, whereas calves given the killed vaccine showed signs of acute enteritis and chronic salmonellosis, (iv) all 12 calves given either 100 X or 100,000 X the LD25 survived the 21-day observation period; the mean survival time in nonvaccinated calves was 8.0 days; in calves given heat-inactivated vaccine and 100 X the LD25 it was 21.0 days, and in calves given 100,000 X the LD25 it was 11.5 days, (v) the fecal bacterial counts of the challenge S. typhimurium SVA44 strain were significantly lower (P less than 0.0005) in both groups given the live vaccine, and (vi) upon autopsy followed by culture, the qualitative recovery of the challenge strain from the alimentary canals and tissues of calves given the live vaccine was significantly lower (P less than 0.005). 相似文献
93.
The ultrastructure of the liver in normal, mildly ketotic and severely ketotic cows was studied using stereological methods. In the liver of severely ketotic cows there is: (1) a significant increase in the volume fraction of hepatocytes and a decrease in the volume fraction of sinusoids, and (2) an increase in the volume fraction of lipid and smooth endoplasmic reticulum and a decrease in the volume fraction of glycogen and Golgi in parenchyma. A decrease in the profile density of mitochondria per 1 mm2 field and an increase of the volume occupied by mitochondria were not significant nor was the decrease in the volume density of rough endoplasmic reticulum. The degree and duration of negative energy balance obviously affect the morphological changes of the fatty liver. However, additional work is needed to determine the significance of ultrastructural changes in liver function. 相似文献
94.
Increase in vascular permeability induced by leukotriene b4 and the role of polymorphonuclear leukocytes 总被引:15,自引:0,他引:15
Leukotriene B4 (LTB4), a metabolite of arachidonic acid, is known to be a potent chemotactic and chemokinetic substance. We have used the hamster cheek pouch microcirculation model to study the effect of LTB4 on vascular permeability and the involvement of neutrophil granulocytes in this response. Intravascular fluorescein-labeled dextran (mol wt 150,000) was used as a tracer of macromolecular permeability. Topical application of LTB4 (150 nM-5 M) to the hamster cheek pouch resulted in an immediate increase in adhering leukocytes in postcapillary venules and later larger venules. Leukocyte accumulation was reversible, but continued longer the higher the dose of LTB4 used. Subsequently, a dose-dependent increase in vascular permeability was seen at postcapillary and larger venules, with a maximum 10–20 min after application; the maximum occurred later the higher the dose of LTB4. Depletion of neutrophil granulocytes by pretreatment of the animals with antineutrophil serum obtained from immunized rabbits significantly decreased the permeability response to LTB4, whereas the response to histamine was unaffected. These results suggest that neutrophil granulocytes play a role in LTB4-mediated permeability increase. LTB4 may be of importance both for the leukocyte accumulation and for the edema formation seen in inflammatory reactions. 相似文献
95.
96.
The mass fraction of certain elements was measured in isolated granulocytes and isolated granulocyte granule fractions from patients with active inflammatory arthritides (N=6) and healthy controls (N=6). The patients had significantly increased amounts of Ca in the granulocytes, in the specific and light azurophil granules, but normal Ca amounts in the dense azurophil granules. Sr was below the detection limit in the granulocytes and granule fraction from controls, but it appeared in high concentrations in the granulocytes and all granule fractions from the patients. The patients had considerably increased granulocyte amounts of Mn but only slightly increased Mn concentrations in the specific granules. Mn was not detectable in azurophil granules from patients and controls. A prominent accumulation of Fe was seen in the granulocytes from the patients, together with an Fe accumulation in the specific granules. Fe was below the detection limit in azurophil granules from patients and controls. The patients had reduced granulocyte Zn and reduced amounts of Zn in the dense and light azurophil granules but normal Zn amounts in the specific granules. The results obtained indicate that (1) the granulocyte accumulation of Ca, Sr, and Fe observed during chronic inflammation is associated with corresponding granule accumulation of these metals; (2) the considerable Mn accumulation in granulocytes during inflammation is not localized in their granules; and (3) the granule subpopulations differ in their capacity to store certain metals. 相似文献
97.
Occurrence of neuropeptide Y (NPY)-like immunoreactivity in catecholamine neurons in the human medulla oblongata 总被引:1,自引:0,他引:1
T. Hökfelt J.M. Lundberg H. Lagercrantz K. Tatemoto V. Mutt J. Lindberg L. Terenius B.J. Everitt K. Fuxe L. Agnati M. Goldstein 《Neuroscience letters》1983,36(3):217-222
We report here the coexistence of a neuropeptide and catecholamines in neurons of the human brain. Using indirect immunofluorescence histochemistry, combined with elution and restaining experiments, neurons in the medulla oblongata of man were demonstrated to contain both a neuropeptide Y-like peptide and the catecholamine synthesizing enzyme tyrosine hydroxylase. 相似文献
98.
Tsuchida H Björnholm M Fernström M Galuska D Johansson P Wallberg-Henriksson H Zierath JR Lake S Krook A 《Pflügers Archiv : European journal of physiology》2002,445(1):25-31
The gene of the p85alpha regulatory subunit of phosphatidylinositol (PI) 3-kinase gives rise to several splice variants. We hypothesized that the expression of p85alpha splice variants may be altered in skeletal muscle from subjects with type 2 diabetes mellitus. Skeletal muscle biopsies were obtained from nine type 2 diabetic and eight healthy men, matched for age, body mass index (BMI) and physical fitness. PI 3-kinase activity in skeletal muscle following in vitro insulin stimulation was reduced in subjects with type 2 diabetes. p85alpha mRNA was elevated fourfold in type 2 diabetic as compared to healthy control subjects ( P<0.05). p85alpha mRNA abundance was positively correlated with plasma insulin concentration ( P<0.01) and serum glucose concentration ( P<0.01). Despite this, protein levels of p85alpha, p55alpha, and the novel human p50alpha were not altered in type 2 diabetic subjects. Thus, although gene expression of full-length p85alpha is increased in skeletal muscle from type 2 diabetics, this is not reflected by increased protein levels. Therefore, defects in PI 3-kinase activity are likely due to impaired activation of the enzyme rather than changes in protein expression of the isoforms of the regulatory subunit. 相似文献
99.
Sabina Rak MD PhD Anette Bjrnson MSc Lena Hkanson MSc PhD Sverre Srenson MD PhD Per Venge MD PhD 《The Journal of allergy and clinical immunology》1991,88(6):878-888
Two groups of birch pollen--allergic patients with seasonal rhinoconjunctivitis and asthma were followed during two consecutive birch-pollen seasons, one group, N = 10, during a season with high pollen load, and one group, N = 15, during a season of low pollen load. Half the patients were treated with immunotherapy (IT) for 3 and 4 years, respectively. The other half of the patients served as control group (non-IT). Bronchoalveolar lavage (BAL) was performed once before each season and once during the pollen season. Eosinophil (EOS) numbers in BAL were increased (p less than 0.01) during the season with high pollen load but not in the season with a low pollen load, and this increment was absent in the IT-treated group. Also, the EOS cationic protein levels were raised in the non-IT-treated group during the season with a high pollen load. The levels of EOS and neutrophil chemotactic activity were raised in BAL in both seasons in the non-IT-treated group compared with the IT-treated group (p less than 0.02, p less than 0.003, p less than 0.04, and p less than 0.005 in high- and low-load pollen season, respectively). Serum and BAL eosinophil chemotactic activity (ECA) were positively correlated (p less than 0.001). We conclude that there is an influx of active EOSs into the lung of pollen-allergic patients with asthma during a pollen season, which may be abrogated by IT. Furthermore, the generation of ECA appears to be an extremely sensitive marker of antigenic exposure, and the potent inhibition of the generation of ECA by IT may provide a clue as to the mechanism of this treatment. 相似文献
100.
Familial partial trisomy 5p resulting from segregation of an insertional translocation 总被引:1,自引:0,他引:1
A case of duplication of segment p13-p15 of the short arm of chromosome 5 as the result of an insertional translocation in a mentally retarded girl with congenital anomalies is reported. Some of the apparently balanced carriers of the inverted insertion showed minor congenital anomalies. 相似文献