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   8649篇
  免费   616篇
  国内免费   153篇
耳鼻咽喉   93篇
儿科学   151篇
妇产科学   185篇
基础医学   1524篇
口腔科学   79篇
临床医学   758篇
内科学   1877篇
皮肤病学   319篇
神经病学   558篇
特种医学   697篇
外科学   1075篇
综合类   26篇
现状与发展   1篇
一般理论   1篇
预防医学   350篇
眼科学   179篇
药学   771篇
中国医学   142篇
肿瘤学   632篇
  2024年   5篇
  2023年   70篇
  2022年   298篇
  2021年   395篇
  2020年   204篇
  2019年   263篇
  2018年   315篇
  2017年   247篇
  2016年   407篇
  2015年   470篇
  2014年   560篇
  2013年   649篇
  2012年   826篇
  2011年   778篇
  2010年   496篇
  2009年   382篇
  2008年   510篇
  2007年   488篇
  2006年   385篇
  2005年   372篇
  2004年   274篇
  2003年   256篇
  2002年   206篇
  2001年   118篇
  2000年   110篇
  1999年   65篇
  1998年   37篇
  1997年   30篇
  1996年   16篇
  1995年   19篇
  1994年   18篇
  1993年   11篇
  1992年   22篇
  1991年   12篇
  1990年   16篇
  1989年   15篇
  1988年   8篇
  1987年   14篇
  1986年   5篇
  1985年   4篇
  1984年   8篇
  1983年   7篇
  1982年   5篇
  1980年   3篇
  1979年   3篇
  1978年   4篇
  1977年   2篇
  1976年   2篇
  1974年   2篇
  1925年   1篇
排序方式: 共有9418条查询结果,搜索用时 7 毫秒
1.
The authors studied the cumulative probability of pregnancy for up to 4 consecutive embryo transfer (ET) cycles with ICSI performed for male factor. Transfers could be either fresh or frozen. The clinical pregnancy rate (PR) for the first 4 cycles were similar [44% (61/366); 31% (44/138); 45% (14/31); 44% (4/9)]. Delivery rates were also similar. There was a lower PR on the second retrieval vs. the first retrieval (47% vs. 29%), but this may be related to most of the second retrievals occurring in the second transfer cycle (67%, 31/55); this may be explained by women who were poor responders and required another retrieval without a frozen ET. The majority of transfers in cycle 1 were fresh, whereas cycles 2-4 used primarily frozen-thawed embryos. These data should be helpful for patients requiring IVF with ICSI in deciding to continue with more IVF cycles or consider other  相似文献   
2.
PURPOSE: This study was undertaken to clarify the importance of bleeding vascular ectasia of the colon as the etiology of massive lower gastrointestinal hemorrhage in patients 40 years of age or younger. METHODS: An otherwise healthy 21-year-old male was admitted to a tertiary medical center with massive lower gastrointestinal hemorrhage. Technetium-labeled red blood cell scan, selective visceral angiography, and colonoscopy identified the source of bleeding as vascular abnormality of the descending colon. Segmental colonic resection was performed. RESULTS: Histologic review of the specimen demonstrated a vascular ectasia. The patient recovered uneventfully and has had no further stigmata of hemorrhage. A review of the literature was undertaken to make clear the significance of vascular ectasia as the source for massive colonic hemorrhage in the young adult. CONCLUSION: This is the first report that documents histologically a vascular ectasia as the source of massive lower gastrointestinal hemorrhage in an otherwise healthy patient less than 40 years of age. Vascular ectasia is an uncommon cause of lower gastrointestinal hemorrhage in the young adult.The Chief, Bureau of Medicine and Surgery, Navy Department, Washington, DC, Clinical Investigation Program sponsored this report #84-16-1968-532, as required by HSETCINST 6000.41A. The views expressed in this article are those of the authors and do not reflect the official policy or position of the Department of the Navy, Department of Defense, or the United States Government.  相似文献   
3.
Cyclodialysis and ciliochoroidal detachment were performed in three eyes of three rabbits and in three eyes of another three rabbits, respectively. After aspiration of the aqueous humor, 0.1 ml of 10% sodium fluorescein was injected intracamerally, and the eyeball was enucleated between 30 minutes and one hour after injection and prepared for fluorescence microscopy. Sodium fluorescein concentrations in the supraciliary space were much greater in the group with cyclodialysis or ciliochoroidal detachment than in the normal control group. These results suggest that (1) in the eye with cyclodialysis, the aqueous humor may freely gain access to the supraciliary space through the cleft between the anterior chamber and the supraciliary space and then be removed rapidly and (2) in the eye with ciliochoroidal detachment, the aqueous humor may pass through the uveoscleral outflow pathway.  相似文献   
4.
AIM: We evaluated differences between men and women with lower urinary tract symptoms (LUTS) combined with nocturia. METHODS: A total of 71 age-matched female-male pairs (median 58, range 20-81 years) who had moderate to severe LUTS and nocturia of more than once per night were enrolled in this study. RESULTS: In the younger group (<50 years), the International Prostate Symptom Score (I-PSS) results of the sexes were not significantly different. However, although total I-PSS results in the elderly group (> or =50 years) were not significantly different, quality of life index scores for women were higher (P = 0.002). On frequency-volume (FV) charts, mean total daytime voided volume (DVV) was significantly higher in younger men than in younger women (P = 0.017), but the mean nocturnal polyuria index (NPi) for women was higher than that for men (P = 0.047). However, maximum DVV (P = 0.009), mean DVV (P < 0.0001), total DVV (P < 0.0001), and mean nocturnal urine volume (P = 0.009) were significantly higher in elderly men than in elderly women. However, numbers of daytime voids were not different. CONCLUSION: Elderly women with LUTS have lower functional bladder capacities than elderly men, as suggested by their smaller mean voided volumes. However, no significant differences were observed between numbers of daytime voids, which was probably due to the smaller total daytime voided volumes of elderly women. In addition, although NPi for younger women and nocturnal urine volume for elderly men was higher, no other differences were observed in terms of other night-time parameters.  相似文献   
5.
Parvalbumin 3 is an Abundant Ca2+ Buffer in Hair Cells   总被引:3,自引:0,他引:3  
Ca2+ signaling serves distinct purposes in different parts of a hair cell. The Ca2+ concentration in stereocilia regulates adaptation and, through rapid transduction-channel reclosure, underlies amplification of mechanical signals. In presynaptic active zones, Ca2+ mediates the exocytotic release of afferent neurotransmitter. At efferent synapses, Ca2+ activates the K+ channels that dominate the inhibitory postsynaptic potential. A copious supply of diffusible protein buffer isolates the three signals by restricting the spread of free Ca2+ and limiting the duration of its action. Using cDNA subtraction and a gene expression assay based on in situ hybridization, we detected abundant expression of mRNAs encoding the Ca2+ buffer parvalbumin 3 in bullfrog saccular and chicken cochlear hair cells. We cloned cDNAs encoding this protein from the corresponding inner-ear libraries and raised antisera against recombinant bullfrog parvalbumin 3. Immunohistochemical labeling indicated that parvalbumin 3 is a prominent Ca2+-binding protein in the compact, cylindrical hair cells of the bullfrog's sacculus, and occurs as well in the narrow, peanut-shaped hair cells of that organ. Using quantitative Western blot analysis, we ascertained that the concentration of parvalbumin 3 in saccular hair cells is approximately 3 mM. Parvalbumin 3 is therefore a significant mobile Ca2+ buffer, and perhaps the dominant buffer, in many types of hair cell. Moreover, parvalbumin 3 provides an early marker for developing hair cells in the frog, chicken, and zebrafish.  相似文献   
6.
We constructed a pubovaginal sling using the Gore-tex Soft Tissue Patch and 2-0 polytetrafluoroethlene (PTFE) suspension suture and placed it in 122 consecutive incontinent women with urethral hypermobility and/or intrinsic sphincter deficiency. We performed a retrospective outcome analysis using a questionnaire-based telephone survey. The mean follow-up period was 24.4 months. Stress incontinence was cured in 88% of patients (equally effective in type II and type III incontinence), de novo postoperative urinary frequency occurred in 32% of cases, and preoperative urinary frequency resolved postoperatively in 51% of patients. Significant urinary obstruction occurred in 5% of patients. Vaginal granulation tissue with exposed sling occurred in 4% of patients. There was no urethral or bladder erosion. The treatment of female stress incontinence with a PTFE sling is effective and durable with minimal complications. Furthermore, this technique addresses many of the presumed technical shortcomings of endoscopic needle suspensions.  相似文献   
7.
The proliferative activity of gastric adenomas from 18 patients (42 endoscopic procedures) was compared with follow-up results. These cases were gastric adenomas proven by follow-up with repeated endoscopic procedures for more than 2 years, or were confirmed as gastric adenocarcinoma thereafter by histopathologic examination. Among the eighteen cases, nine showed carcinoma in the subsequent biopsies (group 1) and the remaining nine did not result in carcinoma (group 2). The proliferating cell nuclear antigen (PCNA) positivity rates of the two groups were significantly different (P < 0.01). The average PCNA positivity in group 1 was 33.1%, while it was 10.0% in group 2. The risk of developing carcinoma increased as the PCNA positivity increased: 0% in the low PCNA positivity group, 41% in the mid-positivity group and 89% in the high positivity group. We concluded that growth fraction could be taken into account as one of the most important prognostic factors for gastric adenoma, and accordingly repeated endoscopic biopsies with close follow-up should be carried out especially in the high PCNA positivity group.  相似文献   
8.
We report an uncommon case of solitary, small hepatic angiosarcoma that was initially considered as a hemangioma. We present the imaging findings, with an emphasis on the initial and follow-up CT and MR findings, as well as report on the more suggestive findings of angiosarcoma than those of a hemangioma.  相似文献   
9.
To determine whether prenatal thiamine deficiency, a frequent concomitant of alcoholism, reduces the response to ethanol during adulthood in the rat as does ethanol exposure in utero (Abel et al. 1981), pregnant Sprague-Dawley rats received either control or thiamine deficient diets together with daily injections of the thiamine antagonist pyrithiamine. At 7 months of age, male offspring were exposed to precisely regulated ethanol vapor concentrations in an inhalation chamber for 24 h and blood ethanol concentrations (BECs) and ethanol-induced intoxication were determined. Prenatally thiamine deficient rats and controls were indistinguishable in terms of appearance, body and liver weights, and the ratios of liver to body weight and brain to liver weight. However, total body water was significantly greater, and BECs and behavioral impairment were decreased, in the experimental rats. These findings indicate that prenatal thiamine deprivation is associated with reduced pharmacologic effect of ethanol as a result of increases in its volume of distribution and rate of metabolism.  相似文献   
10.
Hysteroscopic treatment of septate uterus with Neodymium-YAG laser.   总被引:4,自引:0,他引:4  
OBJECTIVE: To determine the effectiveness of Neodymium-YAG (Nd-YAG) laser for hysteroscopic transection of the septate uterus to improve pregnancy outcome. DESIGN: Patients treated for recurrent pregnancy loss and/or infertility were evaluated for before versus after treatment pregnancy outcomes. SETTING: All patients were referred to a University Reproductive Endocrine and Infertility practice from 1986 through 1990. PATIENTS, PARTICIPANTS: Nineteen patients underwent hysteroscopic transection of uterine septa after exclusion of other factors that may cause recurrent fetal wastages and/or infertility. They were allowed to conceive 8 weeks after surgery after a postoperative hysterosalpingogram. Fourteen women attempted conception during a time span of 11 to 42 months; 3 patients declined to conceive, and 2 were lost to follow-up. INTERVENTIONS: Hysteroscopic transection of the uterine septum with a Nd-YAG laser was performed in all patients. The Nd-YAG laser delivered via a 600-microns bare fiber or an 800-microns sculpted fiber through operative hysteroscopy. MAIN OUTCOME MEASURES: To evaluate the success and complications of this new laser technique. RESULTS: (1) Thirteen patients conceived; 10 delivered a live infant at term; (2) 87% of the postoperative pregnancies were considered successful as compared with 11% preoperative; (3) complications included a small perforation of the uterus (no treatment needed) and development of uterine adhesions (1 case only). CONCLUSIONS: Hysteroscopic metroplasty with the Nd-YAG laser is a valuable alternative new technique for the treatment of uterine septum.  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