全文获取类型
收费全文 | 14733篇 |
免费 | 907篇 |
国内免费 | 78篇 |
专业分类
耳鼻咽喉 | 190篇 |
儿科学 | 380篇 |
妇产科学 | 255篇 |
基础医学 | 2219篇 |
口腔科学 | 1258篇 |
临床医学 | 1264篇 |
内科学 | 3257篇 |
皮肤病学 | 459篇 |
神经病学 | 917篇 |
特种医学 | 625篇 |
外国民族医学 | 1篇 |
外科学 | 1609篇 |
综合类 | 115篇 |
一般理论 | 6篇 |
预防医学 | 1358篇 |
眼科学 | 227篇 |
药学 | 999篇 |
中国医学 | 83篇 |
肿瘤学 | 496篇 |
出版年
2023年 | 112篇 |
2022年 | 288篇 |
2021年 | 460篇 |
2020年 | 320篇 |
2019年 | 435篇 |
2018年 | 497篇 |
2017年 | 355篇 |
2016年 | 397篇 |
2015年 | 420篇 |
2014年 | 570篇 |
2013年 | 749篇 |
2012年 | 988篇 |
2011年 | 1040篇 |
2010年 | 629篇 |
2009年 | 498篇 |
2008年 | 706篇 |
2007年 | 783篇 |
2006年 | 631篇 |
2005年 | 592篇 |
2004年 | 481篇 |
2003年 | 408篇 |
2002年 | 383篇 |
2001年 | 308篇 |
2000年 | 300篇 |
1999年 | 240篇 |
1998年 | 158篇 |
1997年 | 159篇 |
1996年 | 163篇 |
1995年 | 124篇 |
1994年 | 121篇 |
1993年 | 114篇 |
1992年 | 127篇 |
1991年 | 121篇 |
1990年 | 130篇 |
1989年 | 126篇 |
1988年 | 119篇 |
1987年 | 121篇 |
1986年 | 111篇 |
1985年 | 92篇 |
1984年 | 112篇 |
1983年 | 70篇 |
1982年 | 67篇 |
1981年 | 55篇 |
1980年 | 70篇 |
1979年 | 56篇 |
1978年 | 55篇 |
1977年 | 54篇 |
1976年 | 55篇 |
1965年 | 71篇 |
1960年 | 65篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
Preferential expansion of Ly-1 B and CD4 CD8 T cells in the polyclonal lymphocyte responses to murine T.cruzi infection 总被引:4,自引:0,他引:4
Minoprio P.; Bandeira A.; Pereira P.; Santos T. Mota; Coutinho A. 《International immunology》1989,1(2):176-184
Acute murine infection with T.cruzi results in polyclonal lymphocyteresponses manifested by blast transformation of a large fractionof B, CD4+, and CD8+ cells. We describe here the finding ofsignificant increases in the splenic representation of minorpopulations, Ly-1+ B cells and CD4-CD8- T cells. These lymphocytepopulations might play an important role in the host response,as shown by T.cruzi infection of hosts that had been lethallyirradiated and reconstituted with autologous bone marrow. Underthese conditions, the splenic polyclonal PFC responses are nearlyabrogated, and not restored by the transfer of syngeneic peritonealcells which, however, reconstitute T15 idiotype production inthe same hosts. Control levels of PFC responses, however, arereconstituted by transfer of syngeneic splenic T cells. Sincebone marrow-reconstituted animals contain normal numbers ofCD4+ and CD8+ T cells which are actually activated by infection,these results suggest the participation of other T cell populationsin the host response to infection, as also suggested by themarked increases in T cell receptor and messages detectedin the spleen of infected animals. The implications of thesefindings in immunopathology of Chagas' disease are discussed. 相似文献
94.
The central effect of oxytocin (OT) on the aggressive behavior of lactating rats was studied. Female rats are more aggressive than nonlactating resident females, vigorously attacking conspecific intruder male or females. This behavior is considered important for pup protection against infanticide. The present work aimed to test the effects on maternal aggressive behavior of OT infused into the central amygdaloid nucleus (CeM) or bed nucleus of stria terminalis (BNST). The surgeries for bilateral cannula implantation were performed between the 2nd and 4th postpartum day. Three days after the surgery, saline or OT was infused and 5 min later a male intruder was placed in the home-cage and the behaviors were videotaped for 10 min. The frequency of the aggressive behaviors and the duration of locomotion during the aggressive behavior test were measured. The latency to retrieve the pups was also evaluated. The results showed that OT injected into CeM (10 and 20 ng/nucleus) decreased frequency of biting and frontal attack while in the BNST (10 and 20 ng/nucleus) decreased the frequency of biting. No significant change on retrieval activity was detected. OT in CeM and BNST has an inhibitory effect on the aggressive behavior of lactating female rats. 相似文献
95.
96.
Life expectancy in British Marfan syndrome populations 总被引:2,自引:0,他引:2
JR Gray AB Bridges RR West L. McLeish AG Stuart JCS Dean MEM Porteous M. Boxer SJ Davies 《Clinical genetics》1998,54(2):124-128
A total of 206 patients with Marfan syndrome were ascertained throughout genetic clinics in Wales and Scotland during the period 1970–1990. There were 45 deaths representing 22% of the cohort. Mean age at death was 45.3 ± 16.5 years. 50% median cumulative survival in the total cohort (n = 206) was 53 years for males and 72 years for females. Multivariate analysis confirmed severity as the best independent indicator of survival. These findings and survival curves will assist in the counselling of British families and individuals with Marfan syndrome. 相似文献
97.
The GAP-related domain of tuberin, the product of the TSC2 gene, is a target for missense mutations in tuberous sclerosis 总被引:5,自引:0,他引:5
Maheshwar MM; Cheadle JP; Jones AC; Myring J; Fryer AE; Harris PC; Sampson JR 《Human molecular genetics》1997,6(11):1991-1996
Tuberous sclerosis is an autosomal dominant trait in which the
dysregulation of cellular proliferation and differentiation results in the
development of hamartomatous growths in many organs. The TSC2 gene is one
of two genes determining tuberous sclerosis. Inactivating germline
mutations of TSC2 in patients with tuberous sclerosis and somatic loss of
heterozygosity at the TSC2 locus in the associated hamartomas indicate that
TSC2 functions as a tumour suppressor gene and that loss of function is
critical to expression of the tuberous sclerosis phenotype. The TSC2
product, tuberin, has a region of homology with the GTPase activating
protein rap1GAP and stimulates the GTPase activity of rap1a and rab5a in
vitro. Here we show that the region of homology between tuberin and human
rap1GAP and the murine GAP mSpa1 is more extensive than previously reported
and spans approximately 160 amino acid residues encoded within exons 34-38
of the TSC2 gene. Single strand conformation polymorphism analysis of these
exons in 173 unrelated patients with tuberous sclerosis and direct
sequencing of variant conformers together with study of additional family
members enabled characterisation of disease associated mutations in 14
cases. Missense mutations, which occurred in exons 36, 37 and 38 were
identified in eight cases, four of whom shared the same recurrent change
P1675L. Each of the five different missense mutations identified was shown
to occur de novo in at least one sporadic case of tuberous sclerosis. The
high proportion of missense mutations detected in the region of the TSC2
gene encoding the GAP-related domain supports its key role in the
regulation of cellular growth.
相似文献
98.
99.
Transmission of human cytomegalovirus from infected uterine microvascular endothelial cells to differentiating/invasive placental cytotrophoblasts 总被引:10,自引:0,他引:10
Analysis of placentas infected with human cytomegalovirus (CMV) suggested that viral transmission could involve differentiating/invasive cytotrophoblasts in villi that attach the placenta to the uterine wall. To parse the cellular components in this process, we developed a coculture system of polarized uterine microvascular endothelial cell (UtMVEC) infection with an endothelial cell-tropic pathogenic strain of CMV. Then we evaluated the potential role of neutrophils and endothelial cells in the spread of infection to differentiating cytotrophoblasts. As shown by immunocytochemistry and analysis of viral replication, CMV preferentially infected endothelial cells via apical membranes and disrupted cell junction proteins, thereby altering paracellular permeability and cell polarity. Neutralizing antibodies to CMV glycoprotein B, an envelope component that facilitates virion penetration, blocked plaque formation in polarized UtMVEC. Neutrophils transmitted CMV infection to UtMVEC, which in turn infected cytotrophoblasts. However, neutrophils did not directly infect cytotrophoblasts. These findings implicate endothelial cells from the uterine microvasculature as a potential source for CMV infection of endovascular cytotrophoblasts of the anchoring villi. Possibly the cytokine/chemokine milieu in the pregnant uterus could attract immune cells that infect endothelial cells in hybrid fetal-maternal vessels. In turn, these cells could infect endovascular cytotrophoblasts, one possible initiation point of a cascade that results in retrograde placental CMV infection. 相似文献
100.
Permeation of human ovarian tissue with cryoprotective agents in preparation for cryopreservation 总被引:18,自引:10,他引:18
Newton H; Fisher J; Arnold JR; Pegg DE; Faddy MJ; Gosden RG 《Human reproduction (Oxford, England)》1998,13(2):376-380
The recent improvements in the treatment of cancer by chemo- and
radiotherapy have led to a significant increase in the survival rates of
patients with malignant disease, but at the expense of distressing side
effects. One major problem, especially for younger patients, is that
aggressive therapy destroys a significant proportion of the follicular
population, which can result in either temporary or permanent infertility.
Freeze-banking pieces of ovarian cortex prior to treatment is one strategy
for preserving fecundity. When the patient is in remission, fertility
could, theoretically, be restored by autografting the thawed tissue at the
orthotopic site or by growing isolated follicles to maturity in vitro.
Recent studies have found good follicular survival in frozen-thawed human
ovarian tissue but to optimize the process an effective cryopreservation
method needs to be developed. An essential part of such a technique is to
permeate the tissue with a cryoprotectant to minimize ice formation and the
extent of this equilibration is an important determinant of post-thaw
cellular survival. In the current study, we have investigated the diffusion
of four cryoprotective agents into human tissue at both 4 degrees C and 37
degrees C. We have also studied the effect of adding different
concentrations of the non penetrating cryoprotective agent, sucrose, to the
freezing media using the release of lactate dehydrogenase as a measure of
its protective effect. At 4 degrees C propylene glycol and glycerol
penetrated the tissue significantly slower than either ethylene glycol or
dimethyl sulphoxide. At the higher temperature of 37 degrees C all four
cryoprotectants penetrated at a faster rate, however concern about enhanced
toxicity prevents the use of these conditions in practice. Thus, the
results suggest that the best method of preparing tissue for freezing is
exposure for 30 min to 1.5 M solutions of ethylene glycol or dimethyl
sulphoxide at 4 degrees C; this achieved a mean tissue concentration that
was almost 80% that of the bathing solution. We also report that the
addition of low concentrations of sucrose to the freezing medium does not
have a significant protective effect against freezing injury.
相似文献