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   1008篇
  免费   61篇
  国内免费   37篇
耳鼻咽喉   4篇
儿科学   41篇
妇产科学   7篇
基础医学   117篇
口腔科学   47篇
临床医学   134篇
内科学   188篇
皮肤病学   38篇
神经病学   67篇
特种医学   139篇
外科学   96篇
综合类   17篇
预防医学   40篇
眼科学   9篇
药学   122篇
中国医学   5篇
肿瘤学   35篇
  2023年   4篇
  2022年   13篇
  2021年   14篇
  2020年   11篇
  2019年   10篇
  2018年   20篇
  2017年   5篇
  2016年   23篇
  2015年   29篇
  2014年   47篇
  2013年   54篇
  2012年   44篇
  2011年   38篇
  2010年   49篇
  2009年   52篇
  2008年   46篇
  2007年   43篇
  2006年   36篇
  2005年   32篇
  2004年   30篇
  2003年   24篇
  2002年   33篇
  2001年   16篇
  2000年   19篇
  1999年   27篇
  1998年   36篇
  1997年   36篇
  1996年   39篇
  1995年   26篇
  1994年   34篇
  1993年   21篇
  1992年   10篇
  1991年   8篇
  1990年   10篇
  1989年   21篇
  1988年   26篇
  1987年   14篇
  1986年   14篇
  1985年   11篇
  1984年   8篇
  1983年   7篇
  1982年   13篇
  1981年   13篇
  1980年   12篇
  1979年   2篇
  1978年   4篇
  1977年   2篇
  1976年   8篇
  1975年   7篇
  1957年   1篇
排序方式: 共有1106条查询结果,搜索用时 0 毫秒
11.
Male genital tract obstructions may result from infections, previous inguinal and scrotal surgery (vasectomy) and congenital bilateral absence of the vas deferens (CBAVD). Microsurgery can sometimes be successful in treating the obstruction. In other cases and in cases of failed surgical intervention, the patient can be treated by microsurgical or percutaneous epididymal sperm aspiration (MESA, PESA) or testicular sperm extraction (TESE) and intracytoplasmic sperm injection (ICSI). We present the results of 39 ICSI procedures for obstructive azoospermia in 24 couples. The aetiology of the obstruction was failed microsurgery in 11 patients, CBAVD in nine and genital infections in four. Sperm retrieval was accomplished via MESA in four cases, PESA in 18 cases and via TESE in 11 cases. TESE was only applied when PESA failed to produce enough spermatozoa for simultaneous ICSI. In six patients, the ICSI procedure was performed with cryopreserved spermatozoa after an initial PESA procedure. Fertilization occurred in 47% of the metaphase II oocytes; embryo transfer was performed in 92% of procedures and resulted in a clinical pregnancy in 13/39 procedures. Ongoing pregnancy was achieved in 10/39 procedures. One pregnancy was terminated early after prenatal investigation showed a cytogenetic abnormality (47,XX+18, Edwards syndrome). The other nine pregnancies resulted in the live birth of 10 children, without any congenital abnormalities. Epididymal and testicular retrieved spermatozoa were successfully used for ICSI to treat obstructive azoospermia, and resulted in an ongoing pregnancy in 10 of 24 couples (41.6%) after 39 ICSI procedures, a success rate of 25.6% per treatment cycle and of 27.7% per embryo transfer.   相似文献   
12.
p53蛋白的免疫亲和层析纯化   总被引:2,自引:0,他引:2  
钟叔平  曹亮 《免疫学杂志》1997,13(2):122-124,139
建立了p53单克隆抗体pAb1801的免疫亲和层极法纯化p53蛋白,所纯化的p53蛋白经Western Blot(ECL法)检测证明:用此法从p53阳性的SW480细胞中分离到p53蛋白。银染显示pH2.0甘氨酸缓冲液比pH2.8的甘氨酸缓冲液洗脱效果好,这种方法的建立将为分离肿瘤细胞中引起p53蛋白功能失活和研究肿瘤发生机制提供一种有效途径。  相似文献   
13.
Late allograft rejection due to transplant vasculopathy continues to be a major clinical problem. Increasing the ratio of donor transplant size to recipient weight has been shown to reduce the incidence of late allograft failure. Using a murine pancreas transplant model we have tested the hypothesis that increasing the donor transplant size in a recipient can promote long-term allograft survival by promoting recovery from transplant vasculopathy. Recipients of an allograft that showed extensive vasculopathy were transplanted with a second donor transplant. The effect of the second allograft on the vasculopathy present in the first graft was measured. Transplanting a second allograft reversed all signs of ongoing rejection, including transplant vasculopathy, resulting in long-term survival of the first graft. Vasculopathy was only reversed if the first and second grafts were from the same mouse strain, suggesting an antigen-specific mechanism. However, the recovery of the first graft was not associated with antigen-specific peripheral tolerance.  相似文献   
14.
Human mini-chromosomes in mouse embryonal stem cells   总被引:3,自引:2,他引:3  
We have introduced human mini-chromosomes of 4 Mb and approximately 15 Mb in size into mouse embryonal stem cells. Although these human mini- chromosomes are stable in hamster and chicken cells, they re-arrange or segregate aberrantly in the embryonal stem cells and are rapidly lost in the absence of selection. However, one of the mini-chromosomes re- arranged, acquired mouse centromeric sequences and was then stably maintained for at least 60 population doublings in culture. This mini- chromosome, which is 4 Mb in size, is a candidate for a mouse germ line chromosome vector.   相似文献   
15.
Prenatal cytogenetic analysis of 71 fetuses conceived by intracytoplasmic sperm injection (ICSI) resulted in the detection of nine (12.7%) chromosome aberrations including two cases of 47,XXY, four cases involving a 45,X cell line and three autosomal trisomies. Molecular analysis of the parental origin of the deleted or supernumerary chromosome was performed by using polymorphic microsatellite markers. Six cases involving a sex chromosome abnormality were found to be of paternal origin while the two trisomic cases that could be analysed were of maternal origin. Two cases involved the same infertile couple who had two consecutive ICSI pregnancies terminated because of a chromosome abnormality. The replaced embryos in both cases originated from a single batch of ICSI fertilized oocytes of which part was used to initiate the first pregnancy and part was cryopreserved and used to initiate the second pregnancy.   相似文献   
16.
Contribution of cytotoxic T lymphocytes (CTL) to experimental autoimmune thyroiditis (EAT) was well defined (Speidel et al., Eur. J. Immunol. 1997, 27, 2391-2399, Ref. 7). The native porcine thyroglobulin (pTg) showed high sensitivity to endo-o-N-acetylglucosaminidase F (Endo F) and its molecular weights, corresponding to about 330 kDa as a monomer and 660 kDa as a dimer, were reduced to smaller molecular weight forms by Endo F and trifluoromethanesulfonic acid (TMSF). Deglycosylated porcine Tg (dgpTg) and native pTg were injected i.v. into CBA/J mice, without the aid of adjuvants. Both lymphocytic infiltrations of the thyroid glands and levels of Tg-specific CTL were similar to those found in conventional EAT induced by Tg and adjuvants. In contrast, proliferative responses in native pTg and dgpTg-injected mice could not be detected, and titers of antibodies to pTg and dgpTg were 20 times and 30 times lower than that of pTg and adjuvants, respectively. The EAT-inducer CTL belonged to the CD8+ cell subset and exerted their thyroiditogenic potential through release of IFN-gamma. It was concluded that dgpTg-induced EAT is mediated by type 1 cytotoxic T cells (Tcl). Also, results that EAT induction of the glycosylated pTg (gpTg) was much lower than that of dgpTg, suggested that the abberant and incomplete glycosylation of the thyroglobulin is responsible for the induction of autoimmune thyroiditis.  相似文献   
17.
The T1 and T2 values of adenocarcinoma EO 771 inoculated into the hind leg of mice are characterized and correlated with the histopathologic state of the tumor. Growth-dependent changes (indicated by a T1 of 630-910 msec and a T2 of 68-185 msec) can be separated into four characteristic phases. The increase in relaxation times in the early phases (A and B) is due to an increasing amount of viable tumor tissue relative to normal muscle tissue. In the later phases (C and D), a decline of the relaxation parameters is observed that is parallel to an increase in the fraction of necrotic tissue. By multiexponential analysis, two relaxation components (indicated by and, respectively) for T1 and T2 and the corresponding fractions alpha 1 and alpha 2 can be observed for both tumor and surrounding muscle tissue. A tissue criterion ("magnetic resonance fingerprint") is defined by a combination of these multiple parameters. This criterion allows separation of not only muscle and tumor tissue but also viable (early state) and necrotic (late state) tumor tissue.  相似文献   
18.
As a philosophical position, pragmatism can be critiqued to distinguish truth only with methods that bring about desired results, predominantly with scientific enquiry. The article hopes to dismiss this oversimplification and propose that within mental health nursing, enquiry enlightened by pragmatism can be anchored to methods helping to tackle genuine human problems. Whilst pragmatists suggest one reality exists, fluctuating experiences and shifting beliefs about the world can inhabit within; hence, pragmatists propose reality has the potential to change. Moreover, pragmatism includes being cognisant of what works to whom reality concerns, making reality context-driven, with a view to understand how actions shape experiences so what is generated has usefulness. Hence, it somewhat follows pragmatism can inform mental health nursing, after all, nursing is a discipline of action, and awareness is needed in how actions produce experiences that patients find helpful. Given the principles of recovery are preferably adopted in mental health care, the paper will explore how pragmatism can help nurses move towards that goal; specifically, with patients voicing their experiences. This is because like pragmatism, recovery subscribes to hope that reality can progress, and through meaningful experiences and beliefs, patients have expertise about personal difficulties alongside how life may flourish, despite mental illness.  相似文献   
19.
Hsiao  MH; Yu  AL; Yeargin  J; Ku  D; Haas  M 《Blood》1994,83(10):2922-2930
We have previously reported that greater than 60% of human leukemic T- cell lines possess mutations in the p53 tumor suppressor gene. To determine whether T-cell acute lymphoblastic leukemia (T-ALL) patient samples possess p53 mutations, we screened peripheral blood-and bone marrow-derived leukemia samples, taken at diagnosis and at relapse, for p53 mutations. Exons 4 through 9 and selected intron regions of the p53 gene were analyzed using polymerase chain reaction-single-strand conformation polymorphism and direct sequencing. p53 mutations were found in 0 of 15 T-ALL diagnosis samples, as compared with 10 of 36 (28%) T-ALL relapse samples. To determine whether p53 mutations play a role in the recurrence (relapse) of T-ALL, two special groups of T-ALL patients were studied: (1) a group of 8 relapse patients whose disease was refractory to chemotherapeutic treatment, and (2) a group of 6 "paired" T-ALL cell samples from patients for whom we possess both diagnosis and relapse samples. Three of 8 relapsed patients (37.5%) whose disease was refractory to the reinduction of remission by chemotherapy possessed missense mutations of the p53 gene. All 3 cases had mutations in exon 5. Among the paired samples, 3 of 6 patients harbored p53 mutations at disease recurrence, but possessed only wild- type p53 alleles at diagnosis. One case had mutation on exon 4, 1 case in exon 5, and 1 case in exon 8 with loss of heterozygosity. These data clearly indicate that recurrence of T-ALL is associated with missense mutations in p53. Our results indicate that (1) mutations of p53 do occur in T-ALL in vivo, and such mutations are associated with the relapse phase of the disease; and (2) p53 mutation is involved in the progression of T-ALL. This conclusion is supported by our observation that the introduction of T-ALL-derived mutant p53 expression constructs into T-ALL cell lines further increases their growth rate in culture, enhances cell cloning in methylcellulose, and increases tumor formation in nude mice.  相似文献   
20.
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