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   458篇
  免费   31篇
  国内免费   26篇
耳鼻咽喉   2篇
儿科学   22篇
妇产科学   30篇
基础医学   69篇
口腔科学   18篇
临床医学   41篇
内科学   81篇
皮肤病学   3篇
神经病学   13篇
特种医学   63篇
外科学   33篇
综合类   17篇
预防医学   59篇
眼科学   2篇
药学   33篇
中国医学   1篇
肿瘤学   28篇
  2022年   8篇
  2020年   4篇
  2018年   9篇
  2015年   11篇
  2014年   4篇
  2013年   12篇
  2012年   13篇
  2011年   15篇
  2010年   7篇
  2009年   14篇
  2008年   17篇
  2007年   29篇
  2006年   22篇
  2005年   23篇
  2004年   8篇
  2003年   11篇
  2002年   18篇
  2001年   7篇
  2000年   10篇
  1999年   15篇
  1998年   21篇
  1997年   17篇
  1996年   15篇
  1995年   10篇
  1994年   13篇
  1993年   11篇
  1992年   15篇
  1991年   4篇
  1990年   10篇
  1989年   16篇
  1988年   14篇
  1987年   11篇
  1986年   4篇
  1985年   9篇
  1984年   10篇
  1983年   12篇
  1982年   12篇
  1981年   3篇
  1980年   4篇
  1979年   3篇
  1978年   3篇
  1977年   4篇
  1976年   3篇
  1975年   2篇
  1974年   4篇
  1971年   5篇
  1970年   2篇
  1968年   3篇
  1967年   4篇
  1966年   3篇
排序方式: 共有515条查询结果,搜索用时 15 毫秒
1.
2.
周向东  周维善  王钟麒   《药学学报》1997,32(6):416-419
报道新化合物A-失碳-17β-羟基-17α-乙炔基-Δ3(5),9(10)-雌甾二烯-2-酮2的合成。文中探讨了用炔钾粗品对A-失碳-Δ3(5),9(10)-雌甾二烯-2,17-二酮1和A-失碳-6β,19-环氧-Δ3-雄甾-2,17-二酮3的选择性炔化,分别得标题化合物2(44%)及A-失碳-17β-羟基-17α-乙炔基-6β,19-环氧-Δ3雄甾-2-酮4(65%),4经还原性破开环氧、去羟甲基和去醋酰氧基合成了标题化合物2。四步总收率为34%。  相似文献   
3.
Hare  WS 《Radiology》1986,160(1):189-192
Two modified helical basket extractors are described that have increased the success rate of removing ureteral calculi using fluoroscopy from 63% to 92%. Initially a rather stiff and expandable basket with a 20-cm filiform tip is used with coaxial catheters and sheath (stage 1). If this procedure is unsuccessful, a basket with two long cable ends is passed from the nephrostomy out through the urethra (stage 2). When used with coaxial bladder catheters, this technique allows dilatation of the vesicoureteric junction and retrograde catheterization and injection of fluids or gas to dislodge the stone prior to extraction. In a series of 38 patients, stones were removed in all but three (a success rate of 92%). In five cases small stones (less than 5 mm) were not retrieved but subsequent studies were normal. Ureteral stones were found in the abdominal ureter in 28 cases, in the pelvic ureter in seven cases, and in multiple sites in three cases. Stones were larger than 1 cm in 27.7% of cases. Postextraction mucosal edema with reduced ureteral patency was common but usually cleared in 2-3 days. Occasional complications were related to the nephrostomy.  相似文献   
4.
5.
Retrorenal colon: implications for percutaneous diskectomy   总被引:1,自引:0,他引:1  
Helms  CA; Munk  PL; Witt  WS; Davis  GW; Morris  J; Onik  G 《Radiology》1989,171(3):864-865
It has been recommended that computed tomography (CT) with the patient prone be performed in every patient undergoing percutaneous diskectomy; this would enable detection of a retrorenal location of the colon, which could interfere with the percutaneous procedure. In this evaluation of 346 prone CT studies, only one patient (0.29%) was found to have retrorenal or retropsoas bowel that would have been perforated at diskectomy. Because of this extremely low prevalence, the performance of prone CT in every patient undergoing percutaneous lumbar diskectomy is not believed to be necessary.  相似文献   
6.
7.
Gonadotropin-releasing hormone (GnRH) and olfactory neurons migrate together from the olfactory placode, and GnRH neurons eventually reside in the hypothalamus. Hypogonadism in male infants may be diagnosed in the first 6 months of life but cannot be diagnosed during childhood until puberty occurs. Patients with low serum testosterone and low serum gonadotropin levels have idiopathic hypogonadotropic hypogonadism (IHH). Mutations in three genes (KAL1, FGFR1, and GNRHR) comprise most of the known genetic causes of IHH. Treatment with testosterone is indicated if fertility is not desired, whereas GnRH or gonadotropin treatment induces spermatogenesis and fertility.  相似文献   
8.
9.
Previous studies have suggested that human follicular fluid contains factors that reduce the zona-binding capacity of spermatozoa. The present study provides further evidence of the existence of such factors. Using the hemizona binding assay (HZA), we have shown that the inhibitory effect of human follicular fluid on the zona-binding capacity of spermatozoa is concentration-dependent, an inhibitory effect being detected when the concentration of human follicular fluid was > or = 10%. A 1% concentration of human follicular fluid did not possess this inhibitory activity. Heating human follicular fluid at 56 degrees C for 30 min did not affect its inhibitory properties; treatment with proteinase-K abolished such inhibition. Human follicular fluid was fractionated sequentially by concanavalin-A affinity chromatography, Mono Q ion-exchange chromatography and Superose-12 gel filtration. The zona binding inhibitory activity resided in the fraction which bound to the lectin and Mono Q column and contained molecules with native molecular weights of 32 and 192 kDa. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis analysis suggested that the 192 kDa glycoprotein was a tetramer, while the 32 kDa glycoprotein remained as a single molecular species under denaturing conditions. We conclude that two glycoproteins were responsible for the zona binding inhibitory activity of human follicular fluid. The physiological role of these factors remains unclear.   相似文献   
10.
Encoded data on diagnoses and procedures are put to a broad range of uses. Coding accuracy and speed are imperative. One method that coding experts have recommended to improve coding accuracy and speed is automated encoders. The article describes the effect of automated encoders on coding accuracy and speed when used by trained coding staff. A study involving six Veterans Administration medical centers found that, overall, coding accuracy improved 19.4 percent after implementation of encoding software. The effect on coding speed, however, depended on the system set-up, with some set-ups actually reducing the number of discharges coded per day.  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