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   2575篇
  免费   166篇
  国内免费   25篇
耳鼻咽喉   18篇
儿科学   169篇
妇产科学   37篇
基础医学   307篇
口腔科学   52篇
临床医学   237篇
内科学   521篇
皮肤病学   28篇
神经病学   126篇
特种医学   499篇
外科学   232篇
综合类   40篇
一般理论   1篇
预防医学   159篇
眼科学   22篇
药学   118篇
中国医学   4篇
肿瘤学   196篇
  2022年   11篇
  2021年   23篇
  2020年   19篇
  2019年   19篇
  2018年   27篇
  2017年   25篇
  2016年   32篇
  2015年   38篇
  2014年   46篇
  2013年   90篇
  2012年   80篇
  2011年   70篇
  2010年   104篇
  2009年   89篇
  2008年   81篇
  2007年   78篇
  2006年   81篇
  2005年   60篇
  2004年   55篇
  2003年   55篇
  2002年   46篇
  2001年   44篇
  2000年   57篇
  1999年   56篇
  1998年   142篇
  1997年   123篇
  1996年   132篇
  1995年   96篇
  1994年   80篇
  1993年   87篇
  1992年   48篇
  1991年   48篇
  1990年   44篇
  1989年   85篇
  1988年   64篇
  1987年   71篇
  1986年   60篇
  1985年   56篇
  1984年   35篇
  1983年   40篇
  1982年   36篇
  1981年   21篇
  1980年   38篇
  1979年   16篇
  1978年   22篇
  1977年   22篇
  1976年   30篇
  1975年   25篇
  1972年   7篇
  1965年   6篇
排序方式: 共有2766条查询结果,搜索用时 15 毫秒
41.
Increased antiphospholipid antibody prevalence has been demonstrated by a number of recent studies in in-vitro fertilization (IVF) patients but the potential effects of antiphospholipid antibodies on the different components of the reproductive process and the consideration of whether to test IVF patients for antiphospholipid antibodies are controversial. The present study was undertaken to investigate the possible association between the presence of circulating antiphospholipid antibodies (namely the lupus anticoagulant and anticardiolipin antibodies), among a series of 21 consecutive IVF patients having a clinical spontaneous abortion after their first embryo transfer. As a control group (n=42), the nearest IVF cycle resulting in an ongoing pregnancy before and after each miscarried IVF cycle (i.e. the closest cycles in temporal relationship to the index cycle) was used. One patient (4.8%) in the study group and two women (4.8%) among controls were seropositive for antiphospholipid antibodies. These low and similar seropositivity rates found in the two groups studied lead us to conclude that antiphospholipid antibodies testing in IVF patients should be considered only in those women having repeated failures of implantation/clinical abortion after embryo transfer but not in an infertile general population reaching an IVF programme.   相似文献   
42.
The objective was to demonstrate bioequivalence between s.c. and i.m. administration of Humegon (FSH/LH ratio 1:1) and Normegon (FSH/LH ratio 3:1). In two randomized, single-centre, cross-over studies, 18 healthy volunteers on each formulation were assigned to one of the two administration sequences. Subjects were given single doses of one of the above gonadotrophins after endogenous gonadotrophin production had first been suppressed using high-dose oral contraceptive. Subsequently, rate (Cmax, tmax) and extent (AUC) of absorption of follicle stimulating hormone (FSH) and luteinizing hormone (LH) were determined for 14 days. For Cmax and AUC, analysis of variance (ANOVA) was performed on log-transformed data and for tmax ANOVA was performed on ranks. Intramuscular and s.c. injections of Humegon were bioequivalent with respect to the main pharmacokinetic parameters, being AUC and Cmax of FSH absorption. Intramuscular and s.c. injections of Normegon were bioequivalent with respect to the AUC of FSH and not bioequivalent with respect to the Cmax of FSH. For tmax of FSH as well as for most LH variables of both preparations, bioequivalence could not be proven due to the high intra- and interindividual variability and/or concentrations being close to the detection limit. Thus, the main pharmacokinetic FSH variables after i.m. and s.c. administration of Humegon and Normegon were bioequivalent.   相似文献   
43.
A pilot study was designed to examine whether the outcome of embryo transfer in women with a hydrosalpinx might be improved by surgical drainage of the hydrosalpinx at the time of oocyte collection for in- vitro fertilization treatment. A comparative, controlled but retrospective analysis of the results was performed of all women with infective tubal damage aged <40 years old, who had ovulatory cycles, a normal uterus and a partner with normal spermatozoa. A standardized treatment regimen was used. A maximum of three embryos were transferred. Hydrosalpinx was defined by prior hysterosalpingography and/or laparoscopy with transcervical dye injection. A total of 237 embryo transfer cycles in women with hydrosalpinges (tubal distension not visible in 151, visible but not drained in 30 and drained in 56) were compared with 705 embryo transfer cycles in women with tubal disease but no hydrosalpinx. Results were analysed in the first three cycles but also separately in the first cycle to check for bias. Success rates were higher in the first cycle, but did not significantly influence overall differences. Implantation rates were significantly reduced overall in the hydrosalpinx group (8.0 versus 13.2% for controls; P < 0.001), being 8.3% (P < 0.01) in the subgroup without evident tubal distension and 7.5% (not significant) in the drained hydrosalpinx group. This study shows that tubal damage with distal occlusion is associated with a marked reduction in embryo implantation, even in the absence of obvious fluid distension. Surgical drainage of distended hydrosalpinges appears to offer no benefit.   相似文献   
44.
45.
The aims of this work were to measure the accuracy of one continuous speech recognition product and dependence on the speaker's gender and status as a native or nonnative English speaker, and evaluate the product's potential for routine use in transcribing radiology reports. IBM MedSpeak/Radiology software, version 1.1 was evaluated by 6 speakers. Two were nonnative English speakers, and 3 were men. Each speaker dictated a set of 12 reports. The reports included neurologic and body imaging examinations performed with 6 different modalities. The dictated and original report texts were compared, and error rates for overall, significant, and subtle significant errors were computed. Error rate dependence on modality, native English speaker status, and gender were evaluated by performing ttests. The overall error rate was 10.3 +/- 3.3%. No difference in accuracy between men and women was found; however, significant differences were seen for overall and significant errors when comparing native and nonnative English speakers (P = .009 and P = .008, respectively). The speech recognition software is approximately 90% accurate, and while practical implementation issues (rather than accuracy) currently limit routine use of this product throughout a radiology practice, application in niche areas such as the emergency room currently is being pursued. This methodology provides a convenient way to compare the initial accuracy of different speech recognition products, and changes in accuracy over time, in a detailed and sensitive manner.  相似文献   
46.
Lesions of the articular surfaces of the knee have been managed by various techniques over the last 50 years. Surgical management has involved: excising the damaged area, refashioning the underlying bone to produce a fibrous response, and introducing allograft, autograft and synthetic materials to encourage a repair matrix. The techniques and their pitfalls are reviewed and discussed, and suggestions made as to the direction of future studies for the repair of osteochondral lesions in the painful knee.  相似文献   
47.
Immunopathophysiological mechanisms in endometriosis-associated reproductive failure were studied in appropriate populations: infertile and fertile women with and without endometriosis. The incidence of sera positive for any of the autoantibodies tested among infertile women with endometriosis (n = 25) was similar to that observed in the three control groups [unexplained infertility patients (n = 25) and fertile women with (n = 10) and without (n = 25) endometriosis]. The mean volume of peritoneal fluid was significantly elevated in women with endometriosis (both fertile and infertile) as compared with patients without endometriosis (fertile or infertile). The concentration of peritoneal fluid leukocytes and the percentage of cells positive for macrophage markers were significantly increased and the percentage of T lymphocytes significantly decreased in infertile women with endometriosis but not in patients with unexplained infertility and fertile women with endometriosis, as compared with fertile controls without endometriosis. Macrophages from infertile patients with endometriosis had higher sperm phagocytosis than did those from infertile women without endometriosis or fertile subjects with or without endometriosis. Incidences of serum and peritoneal fluid samples embryotoxic to the in-vitro development of 2-cell mouse embryos were significantly higher in infertile patients with endometriosis than in unexplained infertility patients and fertile women with or without endometriosis. It is concluded that immunological mechanisms of endometriosis-associated infertility exist but that these peritoneal immunological factors in infertile women with endometriosis are related to their subfertility rather than to the presence of ectopic endometrial implants. This is supported by the lack of immunological abnormalities observed among fertile women with endometriosis. These immunological abnormalities are lacking in patients with unexplained infertility.   相似文献   
48.
The ileoanal J pouch: radiographic evaluation   总被引:1,自引:0,他引:1  
Hillard  AE; Mann  FA; Becker  JM; Nelson  JA 《Radiology》1985,155(3):591-594
Endorectal ileoanal pull-through offers an attractive alternative to proctocolectomy and ileostomy for patients with ulcerative colitis, Gardner syndrome, and familial polyposis. To our knowledge, a careful radiographic analysis of the ileum, ileal pouch, and ileoanal anastomosis after ileoanal pull-through has not been reported. Thirty-two patients with ulcerative colitis, Gardner syndrome, and familial polyposis underwent colectomy, mucosal proctectomy, and endorectal ileoanal pull-through of a 15-cm ileal "J" pouch and loop ileostomy. Twenty-five (78%) of 32 of all the pouches radiographically demonstrated spiral folds extending from the middle of the pouch to the pectinate line. Other radiographic features included a mesenteric mass effect, pseudopolyps, and a central lucency that indicated intrapouch sutures. Radiographs provide useful information in the postoperative management of the ileal pull-through.  相似文献   
49.
beta-Carotene, canthaxanthin, and beta-carotene plus canthaxanthin were administered to "chinchilla bastard" pigmented rabbits in their rabbit diet (approximately 200 ppm carotenoid per group). The effect of the carotenoids on retinal function and morphology was tested against a control group in the course of 11 months. Electroretinography showed that in contrast to the control animals, beta-carotene-treated rabbits produced increasing peak latencies of the scotopic b-waves. In the canthaxanthin-treated rabbits, a- and b-waves showed hypernormal amplitudes at low cumulative dosages (approximately 0.5-2 g) and reduced amplitudes at higher dosages (about 5 g). The peak latencies of the scotopic a- and b-waves increased remarkably. This effect was still stronger in the carotenoid combination. Histology and electron microscopy indicated that in contrast to the control animals, canthaxanthin-treated rabbits showed a reduction in retinal thickness in some samples. In particular, they exhibited alterations in the granular layers and a marked diminuation of the photoreceptor outer segments and morphological alterations of the photoreceptor inner segments with massive deposition of electron-dense material. In all animals treated with carotenoids, lipid droplets of the retinal pigment epithelium were enlarged in size and number.  相似文献   
50.
Summary To investigate whether 5-HT1-like receptor-mediated inhibition of adenosine 3 : 5-cyclic monophosphate (cyclic AMP) accumulation occurs in nerves or smooth muscle of saphenous vein, infusions of 6-hydroxydopamine (6-OHDA) were administered to dogs with the aim of inducing sympathetic nerve damage. The effects of 6-OHDA on other 5-HT1-like receptor-mediated responses at the pre- and post-junctional level were investigated for comparison by studying 5-hydroxytryptamine (5-HT)-induced inhibition of 3H-noradrenaline release and contraction of smooth muscle respectively.Disruption of nerve function by 6-OHDA was revealed by the lack of catecholaminergic fluorescence and neurogenic contractile responses in saphenous veins from dogs treated with 6-OHDA. In addition, severe impairment of neuronal uptake mechanisms were apparent since basal efflux of 3H-noradrenaline, electrically-evoked release of 3H-noradrenaline and remaining 3H-noradrenaline content were considerably reduced. Some 3H-noradrenaline was taken up and released in 6-OHDA treated tissues which is consistent with the existence of nerve varicosities resistant to the present dosing regime of 6-OHDA, an observation substantiated by electron microscopy studies showing inconsistent lesions of nerve terminals.6-OHDA pre-treatment potentiated the smooth muscle contractile responses mediated by 5-HT1-like receptors as well as potentiating 5-HT-evoked inhibition of prostaglandin E2-stimulated cyclic AMP accumulation. It did not, however, affect 5-HT-induced inhibition of 3H-noradrenaline release. The present results suggest that inhibition of cyclic AMP accumulation by 5-HT occurs predominantly in smooth muscle. Correspondence to A. J. Kaumann at the above address  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