全文获取类型
收费全文 | 7875篇 |
免费 | 479篇 |
国内免费 | 31篇 |
专业分类
耳鼻咽喉 | 120篇 |
儿科学 | 244篇 |
妇产科学 | 102篇 |
基础医学 | 1095篇 |
口腔科学 | 803篇 |
临床医学 | 544篇 |
内科学 | 1884篇 |
皮肤病学 | 122篇 |
神经病学 | 526篇 |
特种医学 | 227篇 |
外国民族医学 | 2篇 |
外科学 | 725篇 |
综合类 | 46篇 |
一般理论 | 3篇 |
预防医学 | 816篇 |
眼科学 | 117篇 |
药学 | 564篇 |
中国医学 | 42篇 |
肿瘤学 | 403篇 |
出版年
2023年 | 68篇 |
2022年 | 142篇 |
2021年 | 265篇 |
2020年 | 170篇 |
2019年 | 223篇 |
2018年 | 273篇 |
2017年 | 189篇 |
2016年 | 230篇 |
2015年 | 263篇 |
2014年 | 335篇 |
2013年 | 416篇 |
2012年 | 655篇 |
2011年 | 644篇 |
2010年 | 373篇 |
2009年 | 310篇 |
2008年 | 473篇 |
2007年 | 471篇 |
2006年 | 412篇 |
2005年 | 347篇 |
2004年 | 294篇 |
2003年 | 250篇 |
2002年 | 228篇 |
2001年 | 135篇 |
2000年 | 153篇 |
1999年 | 138篇 |
1998年 | 68篇 |
1997年 | 61篇 |
1996年 | 49篇 |
1995年 | 31篇 |
1994年 | 31篇 |
1993年 | 22篇 |
1992年 | 63篇 |
1991年 | 52篇 |
1990年 | 50篇 |
1989年 | 54篇 |
1988年 | 54篇 |
1987年 | 38篇 |
1986年 | 40篇 |
1985年 | 47篇 |
1984年 | 37篇 |
1983年 | 21篇 |
1982年 | 15篇 |
1981年 | 20篇 |
1980年 | 20篇 |
1979年 | 14篇 |
1978年 | 14篇 |
1977年 | 15篇 |
1976年 | 18篇 |
1975年 | 17篇 |
1968年 | 12篇 |
排序方式: 共有8385条查询结果,搜索用时 218 毫秒
31.
32.
Metabolic activation to a mutagen of 3-hydroxy-trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene, a secondary metabolite of benzo[a]pyrene 总被引:2,自引:0,他引:2
Glatt Hansruedi; Seidel Albrecht; Ribeiro Odartey; Kirkby Charles; Hirom Paul; Oesch Franz 《Carcinogenesis》1987,8(11):1621-1627
3-Hydroxy-trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (3-OH-BP-7,8-diol)wag isolated from arylsulfatase/ß-glucuronidase-treatedbile of rats to which 3-hydroxybenzo[a]pyrene (3-OH-BP) hasbeen administered. This triol was investigated for mutagenicityin Salmonella typhimurium (reversion to histidine prototrophyof strains TA 97, TA 98, TA 100 and TA 1537) and in V79 Chinesehamster cells (acquisition of resistance to 6-thioguanine).When no exogenous metabolizing system was added the triol wasinactive, while 3-OH-BP showed weak mutagenic effects with allfour bacterial strains. In the presence of NADPH-fortified postmitochondrialsupernatant fraction (S9 mix) of liver homogenate from Aroclor1254-treated rats, the mutagenicity of 3-OH-BP was potentiated,and the triol was activated to a mutagen(s). In the presenceof S9 mix, the triol was 518 times more mutagenic than3-OH-BP in strains TA 97, TA 100 and TA 1537, but both compoundsshowed similar mutagenic potencies with strain TA 98. Thesestrain differences strongly suggest that the mutagenicity of3-OH-BP in the S9 mix-mediated test was not exclusively dueto metabolites of 3-OH-BP-7, 8-diol. Trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene(BP-7,8-diol), like the triol, showed mutagenic effects onlyin the presence of S9 mix. Strain TA 1537 was reverted by thetriol but not by the diol. In the other bacterial strains thediol was more mutagenic than the triol, the difference in potencybeing largest in strain TA 100 (2.5-to 10-fold, depending onthe experimental conditions). In V79 cells, the diol was a potentmutagen, while the triol showed only very weak mutagenic effects.However the triol was more cytotoxic than the diol. High cytotoxicityof the triol was observed even in the absence of S9 mix. Theresults of the present study demonstrate that metabolites of3-OH-BP-7, 8-diol) are biologically-active derivatives of benzo[a]pyrene.Comparison of the mutagenic effectiveness in different bacterialstrains also reveals that metabolites of 3-OH-BP-7, 8-diol andof BP-7, 8-diol substantially differ in the kind of geneticalterations they evoke. 相似文献
33.
Cleide G. da Silva Ana Rúbia F. Bueno Patrícia F. Schuck Guilhian Leipnitz Csar A. J. Ribeiro Clvis M. D. Wannmacher Angela T. S. Wyse Moacir Wajner 《International journal of developmental neuroscience》2003,21(4):217-224
L-2-Hydroxyglutaric acid (LGA) is the biochemical hallmark of patients affected by the neurometabolic disorder known as L-2-hydroxyglutaric aciduria (LHGA). Although this disorder is predominantly characterized by severe neurological findings and pronounced cerebellum atrophy, the neurotoxic mechanisms of brain injury are virtually unknown. In the present study, we investigated the effect of LGA, at 0.25-5mM concentrations, on total creatine kinase (tCK) activity from cerebellum, cerebral cortex, cardiac muscle and skeletal muscle homogenates of 30-day-old Wistar rats. CK activity was measured also in the cytosolic (Cy-CK) and mitochondrial (Mi-CK) fractions from cerebellum. We verified that tCK activity was significantly inhibited by LGA in the cerebellum, but not in cerebral cortex, cardiac muscle and skeletal muscle. Furthermore, CK activity from the mitochondrial fraction was inhibited by LGA, whereas that from the cytosolic fraction of cerebellum was not affected by the acid. Kinetic studies revealed that the inhibitory effect of LGA on Mi-CK was non-competitive in relation to phosphocreatine. Finally, we verified that the inhibitory effect of LGA on tCK was fully prevented by pre-incubation of the homogenates with reduced glutathione (GSH), suggesting that this inhibition is possibly mediated by oxidation of essential thiol groups of the enzyme. Considering the importance of creatine kinase activity for energy homeostasis, our results suggest that the selective inhibition of this enzyme activity by increased levels of LGA could be possibly related to the cerebellar degeneration characteristically found in patients affected by L-2-hydroxyglutaric aciduria. 相似文献
34.
Intrasplenic hepatocellular transplantation corrects hepatic encephalopathy in portacaval-shunted rats. 总被引:7,自引:0,他引:7
J Ribeiro B Nordlinger F Ballet L Cynober C Coudray-Lucas M Baudrimont C Legendre R Delelo Y Panis 《Hepatology (Baltimore, Md.)》1992,15(1):12-18
The aim of this work was to evaluate the effect of intrasplenic hepatocellular transplantation on hepatic encephalopathy in an experimental model of chronic liver failure induced by end-to-side portacaval shunt in the rat. Inbred male Wistar Furth rats were divided into three groups: rats subjected to portacaval shunt (n = 10), rats subjected to portacaval shunt and intrasplenic hepatocellular transplantation of 10(7) hepatocytes isolated from livers of syngeneic rats (n = 10) and sham-operated rats (n = 10). Behavior tests were performed in a blind fashion at 3 wk, at 2 mo and at 3 mo after surgery. Spontaneous activity and nose-poke exploration by individual rats were studied in automated open field boxes equipped with infrared cells. Each cell beam interruption was automatically recorded on a microcomputer and transformed into a score index (counts/hour). Plasma levels of amino acids, ammonia and total biliary acids were measured. Portacaval shunt rats showed reduced spontaneous activity and nose-poke exploration scores. Intrasplenic hepatocellular transplantation significantly increased spontaneous activity after 2 mo and improved nose-poke exploration after 3 wk. At 3 mo, spontaneous activity and nose-poke exploration in portacaval shunt/intrasplenic hepatocellular transplantation rats were not significantly different from those of sham rats. Increases in plasma ammonia levels after portacaval shunt were not corrected. Amino acid imbalance and bile acid concentration in plasma were partially corrected by intrasplenic hepatocellular transplantation. These data show that intrasplenic hepatocellular transplantation can correct the neurological symptoms of hepatic encephalopathy in an experimental model of chronic liver failure and suggest that intrasplenic hepatocellular transplantation might be of therapeutic interest in chronic liver failure. 相似文献
35.
Platelets stored in CLX™ blood bags, under normal blood banking conditions, were studied for up to 7 days to determine if changes ocurred in the levels of membrane glycoproteins (GP) Ib-IX and IIb-IIIa. Radiolabeled monoclonal antibodies (MAB) were used to estimate the number of glycoprotein molecules on the surface membrane of intact platelets. GP IX and GP IIb-IIIa levels remained essentially unaltered during storage. In contrast, the content of GP Ib at day 7 decreased by 45% of the total when fresh. The aggregation response to ristocetin, which requires GP Ib, was also diminished after 7 days. Addition of protease inhibitors, leupeptin and/or aprotinin did not appear to influence the degradation of this glycoprotein. We conclude that storage at 22°C has deleterious effects on the GP Ib content of platelets. 相似文献
36.
Milton Carlos Gon?alves Salvador Accácio Lins do Valle Mariana Carvalho Mandim Ribeiro Jefferson Ricardo Pereira 《Journal of applied oral science : revista FOB》2007,15(1):9-13
A group of destructive changes occurring in jaws in patients with maxillary complete dentures and mandibular removable partial dentures (bilaterally) has been described in the literature as the combination syndrome. However, this condition is not clinically observed in all patients. The aim of this study was to establish the prevalence index on signs of combination syndrome and to verify whether these changes also occurred in patients rehabilitated with a mandibular removable partial denture (unilaterally). Sample was composed of 44 patients, completely edentulous in the maxilla. Thirty-two patients had a Kennedy Class I removable partial denture and 12 a Kennedy Class II. Three major alterations were observed in 20.5% of the studied population. Nevertheless, these changes were present only in 25% of patients with Kennedy Class I removable partial denture. Based on the findings of this study, it can be concluded that patients with Kennedy Class II removable partial denture do not have similar signs that lead to the combination syndrome’s condition. 相似文献
37.
Vertebral compression fracture as a presenting feature of acute lymphoblastic leukemia in children 总被引:2,自引:0,他引:2
Twenty-four (1.6%) of 1466 children with acute lymphoblastic leukemia (ALL) treated at St. Jude Children's Research Hospital had vertebral compression fractures at diagnosis. When compared with patients without this complication, they were more likely to have good prognostic features, including a leukocyte count of greater than 25 X 10(9)/l, a leukemic cell DNA index of greater than 1.15, and hyperdiploidy (greater than 50 chromosomes). Complete remission of ALL was induced in all patients, and symptoms of vertebral compression fractures abated following antileukemia therapy. Although the diagnosis of ALL was delayed for some patients because this unusual presenting complication was not recognized as such, their treatment outcome was as good as that for other children with "standard-risk" ALL. 相似文献
38.
Darai E; Leblanc M; Walker-Combrouze F; Bringuier AF; Madelenat P; Scoazec JY 《Human reproduction (Oxford, England)》1998,13(5):1346-1352
We evaluated the immunohistochemical expression of cadherins and CD44
variants in 20 endometriomas, 20 cystadenomas, 20 borderline ovarian
tumours as well as 20 ovarian carcinomas, and the serological and cystic
fluid concentrations of soluble E-cadherin and soluble CD44 standard
(sCD44sdt) in 20 endometriomas, 20 cystadenomas, six borderline and 11
carcinomas of the ovary. In endometriomas, immunostaining of E- and
N-cadherin was negative (20 and 30% respectively). CD44 H, v3 and v6
immunostaining were detected in 63, 10 and 40% respectively. A difference
in immunostaining for E-cadherin was found between endometriomas and
cystadenomas (P < 0.001) and for N- cadherin between endometriomas and
carcinomas (P < 0.001). A difference in CD44H immunostaining was
observed between endometriomas and cystadenomas (P < 0.035) but not with
borderline ovarian tumours and carcinomas. No difference in serum
concentrations of soluble E- cadherins and CD44 standard was found between
the four groups of tumours. Cystic fluid concentrations of E-cadherin were
lower in endometriomas than in borderline tumours and ovarian carcinomas (P
< 0.001). High concentrations of soluble CD44 standard cystic fluid were
found in endometriomas than in other ovarian cysts. Endometriomas and
borderline tumours share alterations of cadherins and CD44 isoforms which
may help in the understanding of the aggressive and invasive potentials of
endometriotic cells.
相似文献
39.
Genital asymmetry in men 总被引:1,自引:0,他引:1
This study examined genital asymmetry in a large sample of men. The
probands were 6544 non-delinquent men who were interviewed by the Kinsey
Institute for Research in Sex, Gender and Reproduction from 1938 to 1963.
The measures were four indicators of penile and scrotal asymmetry, along
with self-reported handedness, from Kinsey's interview protocol. Most men
reported some degree of lateral asymmetry in their flaccid penis and in
their testicles; less asymmetry was reported for their erect penis. The
asymmetry typically occurred in the left direction, and this pattern
occurred in both right- and nonright- handers. However, this 'leftward'
pattern was significantly less pronounced in nonright-handers. The results
are discussed in relation to previous findings of genital asymmetry in men,
the possible relationship of genital asymmetry to functional cerebral
asymmetry, and recent data suggesting genital asymmetry may predict
patterns of cognitive performance and genital/sexual organ cancers.
相似文献
40.