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   3106篇
  免费   263篇
  国内免费   12篇
耳鼻咽喉   70篇
儿科学   150篇
妇产科学   33篇
基础医学   496篇
口腔科学   71篇
临床医学   371篇
内科学   668篇
皮肤病学   55篇
神经病学   246篇
特种医学   268篇
外国民族医学   2篇
外科学   317篇
综合类   75篇
预防医学   226篇
眼科学   28篇
药学   191篇
中国医学   1篇
肿瘤学   113篇
  2023年   14篇
  2022年   20篇
  2021年   45篇
  2020年   26篇
  2019年   55篇
  2018年   67篇
  2017年   47篇
  2016年   43篇
  2015年   67篇
  2014年   85篇
  2013年   126篇
  2012年   137篇
  2011年   142篇
  2010年   102篇
  2009年   116篇
  2008年   139篇
  2007年   147篇
  2006年   160篇
  2005年   137篇
  2004年   122篇
  2003年   98篇
  2002年   92篇
  2001年   82篇
  2000年   64篇
  1999年   67篇
  1998年   79篇
  1997年   81篇
  1996年   79篇
  1995年   69篇
  1994年   64篇
  1993年   57篇
  1992年   51篇
  1991年   41篇
  1990年   39篇
  1989年   54篇
  1988年   59篇
  1987年   70篇
  1986年   52篇
  1985年   45篇
  1984年   41篇
  1983年   31篇
  1982年   32篇
  1981年   20篇
  1980年   27篇
  1979年   25篇
  1978年   17篇
  1977年   20篇
  1974年   15篇
  1971年   11篇
  1968年   11篇
排序方式: 共有3381条查询结果,搜索用时 15 毫秒
31.
Permanent impairment of embryo development by hydrosalpinges   总被引:6,自引:9,他引:6  
Recent reports suggest a deleterious effect of hydrosalpinges on pregnancy outcome for in-vitro fertilization (IVF) and improvement following surgical treatment. We compared the effect of hydrosalpinx on pregnancy outcome in 286 patients having 348 IVF cycles and followed the development of untransferred embryos for 7 days to determine if hydrosalpinges affect oocyte quality or embryo development. The delivery rate per retrieval was significantly lower for patients with hydrosalpinx, but was restored by surgical treatment to that of patients without hydrosalpinx. However, the implantation rate per embryo transferred and normal blastulation of untransferred embryos, which were significantly decreased in patients with hydrosalpinx, and growth arrest and degeneration of untransferred embryos, which were significantly increased compared to patients without hydrosalpinx, were not restored by surgical treatment of hydrosalpinges. We conclude that surgical treatment of hydrosalpinges decreases early pregnancy loss and improves pregnancy outcome, possibly by diminishing reversible deleterious effects exerted on the endometrium. As we have seen in our laboratory, hydrosalpinges may have a permanent negative influence on ovarian function, follicular development and oocyte quality since implantation of transferred embryos and normal blastulation of untransferred embryos remain low, and in-vitro growth arrest and degeneration remain high despite surgical treatment of hydrosalpinges.   相似文献   
32.
A controlled trial of acyclovir for chickenpox in normal children   总被引:4,自引:0,他引:4  
BACKGROUND. Chickenpox, the primary infection caused by the varicella-zoster virus, affects more than 3 million children a year in the United States. Although usually self-limited, chickenpox can cause prolonged discomfort and is associated with infrequent but serious complications. METHODS. To evaluate the effectiveness of acyclovir for the treatment of chickenpox, we conducted a multicenter, double-blind, placebo-controlled study involving 815 healthy children 2 to 12 years old who contracted chickenpox. Treatment with acyclovir was begun within the first 24 hours of rash and was administered by the oral route in a dose of 20 mg per kilogram of body weight four times daily for five days. RESULTS. The children treated with acyclovir had fewer varicella lesions than those given placebo (mean number, 294 vs 347; P less than 0.001), and a smaller proportion of them had more than 500 lesions (21 percent, as compared with 38 percent with placebo; P less than 0.001). In over 95 percent of the recipients of acyclovir no new lesions formed after day 3, whereas new lesions were forming in 20 percent of the placebo recipients on day 6 or later. The recipients of acyclovir also had accelerated progression to the crusted and healed stages, less itching, and fewer residual lesions after 28 days. In the children treated with acyclovir the duration of fever and constitutional symptoms was limited to three to four days, whereas in 20 percent of the children given placebo illness lasted more than four days. There was no significant difference between groups in the distribution of 11 disease complications (10 bacterial skin infections and 1 case of transient cerebellar ataxia). Acyclovir was well tolerated, and there was no significant difference between groups in the titers of antibodies against varicella-zoster virus. CONCLUSIONS. Acyclovir is a safe treatment that reduces the duration and severity of chickenpox in normal children when therapy is initiated during the first 24 hours of rash. Whether treatment with acyclovir can reduce the rare, serious complications of chickenpox remains uncertain.  相似文献   
33.
A prospective study was carried out to compare the fertilizing capability and pregnancy outcome following intracytoplasmic sperm injection (ICSI) using spermatozoa obtained from ejaculates, or surgically from epididymis or seminiferous tubules. A total of 77 ICSI cycles (one per patient) was included. In all, 28 patients had severe oligoasthenoteratozoospermia, 19 patients had obstructive azoospermia and 30 patients had non-obstructive azoospermia. The main outcome measures were fertilization rate per injected metaphase II oocyte and the clinical pregnancy rate per embryo transferred back to the female recipients. In patients with severe oligoasthenoteratozoospermia, the fertilization and pregnancy rates were 79 and 25 %. In patients with obstructive azoospermia, for whom epididymal spermatozoa were used, these were 75 and 28%, and in the non-obstructive group for which testicular spermatozoa were used for injection, they were 69 and 21% respectively. These rates were not significantly different in the three groups (P = 0.85 and P = 0.14 respectively), suggesting that spermatozoa from the ejaculates and epididymal or testicular biopsies are able to fertilize equally by using ICSI. Live birth per embryo transfer was significantly reduced in patients with non-obstructive azoospermia compared to the other two groups. The high abortion rate (50%) in the group in which testicular spermatozoa were used raises doubts about the developmental competence of such embryos.   相似文献   
34.
Signaling to NF-kappaB   总被引:30,自引:0,他引:30  
Hayden MS  Ghosh S 《Genes & development》2004,18(18):2195-2224
  相似文献   
35.
36.
The bias favoring deletion over inversion in DH-JH rearrangement has been known for years, but the underlying mechanism has yet to be fully defined. It has been suggested that the ratio of deletion/inversion is determined by the combined effect of two factors: (i) the relative strengths of 5' and 3' recombination signal sequences (RSS) of a DH segment, and (ii) the efficiency with which the deletional product (one joint) forms relative to the inversional product (two joints). In this study, we analyzed for the first time the effect of factor 1 alone on the biased 3' RSS utilization in DH-JH joining by using deletional plasmids in an extrachromosomal substrate V(D)J recombination assay. It was found that the 3' RSS and associated coding end (12 bp) mediate recombination more efficiently than the 5' RSS/coding end DH-JH plasmids. These results demonstrate that the effect of the RSS/coding end alone can account, at least partially, for the predominant deletion in DH-JH recombination. The potential effect of the relative strength of RSS and associated coding end on the ordered rearrangement of DH-JH followed by VH to DH-JH was also assessed. When recombination frequencies of D-->J (3' DH to J3) were compared with frequencies of V-- >D (VHPJ14 to 3' DH or VHOX2 to 3' DH), it was found that V-->D joining was, if anything, more efficient than D-->J joining. Therefore, if all three segments were accessible, RSS/coding end effects would not contribute to the ordered rearrangement of the IgH locus.   相似文献   
37.
Amyloid in pancreatic ganglia and nerves (ganglioneuronal amyloid) was demonstrated in 4 of 8 diabetic cats with islet amyloid deposits. Eighteen nondiabetic cats (including 4 with islet amyloid) did not have detectable amyloid in pancreatic nerves or ganglia. Ganglioneuronal amyloid had staining characteristics identical to those previously reported for islet amyloid, including 1) congophilia, 2) resistance to oxidation by KMnO4, 3) immunoreactivity (PAP technique) with antiserum to a B-chain-rich insulin fraction, and 4) no reactivity with antisera to insulin, glucagon, or somatostatin. Nonneuronal cells with insulin, glucagon, and somatostatin immunoreactivity were seen in many pancreatic ganglia and nerves; and in a few instances, B cells were found near ganglioneuronal amyloid deposits. The premise that these ganglioneuronal amyloid deposits (like islet amyloid) are insulin-related is supported by their immunoreactivity with antiserum to B-chain-rich insulin and the demonstration of B cells in pancreatic ganglia and nerves.  相似文献   
38.
Immune response of adults to sequential influenza vaccination   总被引:1,自引:0,他引:1  
Annual immunization against influenza is recommended for numerous individuals, but the antibody response to sequential vaccination has not been well characterized. Levels of hemagglutination-inhibition antibody were measured in adults given either two or three doses of trivalent influenza vaccine at six-month intervals. A significant rise in the number of individuals with antibody titers of greater than or equal to 40 was seen for all three antigens only after initial vaccination. Repeated vaccination was necessary to maintain adequate antibody levels only to the A/Brazil (H1N1) antigen; it did not significantly affect the proportions of individuals with protective levels of antibody to either the A/Bangkok (H3N2) or the B/Singapore 222/79 antigens. These findings do not support the current recommendation for annual immunization when the vaccine formulation has not changed.  相似文献   
39.
Summary A cortico-cancellous flap from the anterolateral aspect of the upper third of the tibia was presented. Sixty lower limbs of fresh cadavers were dissected. The vascular bundle includes the anterior tibial artery and its recurrent collateral branches and recurrent and muscllo periostal arteries. The flap is harvested with the interosseous membrane and can be used either free or pedicled. We used this flap for two patients suffering from pseudarthrosis. Long range clinical and radiological results are good.
Le transfert osseux vascularisé tibial superieur
Résumé Les auteurs décrivent un transfert ostéo-periosté vascularisé, prélevé sur la face antéro-latérale de l'extremité supérieure du tibia. L'étude anatomique porte sur soixante membres inférieurs, conservés au froid. La vascularisation métaphysaire du transfert provient de la branche récurrente tibiale antérieure et de ses rameaux, la vascularisation diaphysaire étant issue des branches musculo-périostiées proximales. Le transfert vascularisé est prélevé avec la membrane interosseuse et peut être pediculé ou libre. L'expérience clinique porte sur deux cas de pseudarthroses multiopérées. Les résultats cliniques et radiologiques sont bons à long terme.
  相似文献   
40.
The polymorphic CAG repeat that is expanded on Huntington disease(HD) chromosomes is flanked by a CCG repeat. Here we show thatthis CCG tract, previously assumed to be invariant at sevenCCG repeats, is also polymorphic. We have identified five CCGalleles from 205 normal chromosomes, with 137 (67%) having allelesof seven repeats, five (2%) with nine repeats, 61 (30%) with10 repeats, one (0.5%) with 11 repeats and one (0.5%) with 12repeats. In contrast, analysis of 113 HD chromosomes revealedthat the majority (105 chromosomes, 93%) contained seven CCGrepeats, while the remaining eight chromosomes (7%) had allelesizes of 10 CCG repeats. Despite evidence that both CAG andCCG are polymorphic on normal chromosomes, we have found thatit is only the CAG length that has a significant impact on ageof onset. The discovery of larger sized CCG alleles, however,has significant implications for the assessment of CAG repeatlength, particularly for persons with estimated CAG size of36–42 repeats, since an overestimation of CAG length inthis range could result in erroneous information being impartedto patients.  相似文献   
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