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   241983篇
  免费   20428篇
  国内免费   14384篇
耳鼻咽喉   2177篇
儿科学   3036篇
妇产科学   4879篇
基础医学   28302篇
口腔科学   4207篇
临床医学   30848篇
内科学   39812篇
皮肤病学   2817篇
神经病学   13543篇
特种医学   8528篇
外国民族医学   96篇
外科学   26648篇
综合类   34064篇
现状与发展   48篇
一般理论   45篇
预防医学   15084篇
眼科学   6674篇
药学   24187篇
  164篇
中国医学   10920篇
肿瘤学   20716篇
  2024年   709篇
  2023年   3490篇
  2022年   8679篇
  2021年   11420篇
  2020年   8390篇
  2019年   7591篇
  2018年   7988篇
  2017年   6966篇
  2016年   6662篇
  2015年   10085篇
  2014年   12687篇
  2013年   11878篇
  2012年   17529篇
  2011年   19210篇
  2010年   11712篇
  2009年   9373篇
  2008年   12753篇
  2007年   12798篇
  2006年   12358篇
  2005年   12436篇
  2004年   8597篇
  2003年   7635篇
  2002年   6606篇
  2001年   5987篇
  2000年   6105篇
  1999年   6407篇
  1998年   3649篇
  1997年   3668篇
  1996年   2788篇
  1995年   2581篇
  1994年   2230篇
  1993年   1496篇
  1992年   2289篇
  1991年   1995篇
  1990年   1664篇
  1989年   1454篇
  1988年   1264篇
  1987年   1176篇
  1986年   941篇
  1985年   748篇
  1984年   491篇
  1983年   381篇
  1982年   225篇
  1981年   201篇
  1980年   191篇
  1979年   243篇
  1978年   141篇
  1977年   112篇
  1976年   97篇
  1974年   116篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
T lymphocytes play a fundamental role in the initiation and regulation of chronic inflammatory responses in patients with asthma. CD69 is an early marker of T‐cell activation. The levels of intercellular adhesion molecule‐1 (ICAM‐1, CD54) and L ‐selectin have been reported to increase in patients with allergic diseases and asthma. The present study was therefore undertaken to investigate the expression of CD69, CD54, and L ‐selectin by T lymphocytes of children with asthma, before and after immunotherapy. Eighteen children newly diagnosed with asthma, 11 good and nine poor responders to immunotherapy, and 16 normal subjects, were enrolled in this study. The percentages of CD69+, CD54+, and CD62L+ cells in T lymphocytes were measured by using flow cytometry. The levels of CD69, CD54, and CD62L in serum and culture supernatants were determined by using enzyme‐linked immunosorbent assay (ELISA). The expression of CD69 and CD54 on CD3+ T lymphocytes was significantly higher in children with asthma than in control patients. All the patient groups expressed (spontaneously and following stimulation with phorbol myristate acetate and ionomycin together with mite‐extract proteins) greater amounts of CD69 and CD54 than did control subjects. With long‐term immunotherapy, the percentages of CD69+ and CD54+ T lymphocytes were significantly lower in patients with a good response to immunotherapy. Our results also showed significantly lower serum L ‐selectin levels following immunotherapy. In conclusion, successful immunotherapy resulted in decreased expression and production of CD69 and CD54. These results may explain, in part, the clinical efficacy of immunotherapy.  相似文献   
82.
L-asparaginase, an effective antileukemia and antilymphoma agent, is toxic to many organ systems. We report a case of ureteral obstruction caused by L-asparaginase via the inflammatory complication of acute pancreatitis. The patient was an 11-year-old boy with acute lymphoblastic leukemia. Six days after completing a 4-week induction therapy containing 9 doses of L-asparaginase, severe left abdominal pain developed. Abdominal computed tomography showed phlegmon formation anterior to the pancreatic head and in the left posterior pararenal space. The strands of inflammatory soft tissues encased the upper third of the left ureter, causing left hydroureter and left hydronephrosis. The ureteral obstruction resolved after insertion of a double-J catheter that remained in place for 66 days. This case suggests that L-asparaginase may play a role in the pathogenesis of ureteral obstruction in children receiving chemotherapy.  相似文献   
83.
In vivo 19F NMR at 4.7 T has shown that the biphasic elimination of the vapor anesthetic isoflurane from rat brain is ca 15% slower in old (23-24 months) animals compared with young (5-6 months) animals. The fast kinetic component has a t1/2 of ca 7-9 min and the slow event, 100-115 min. Gas chromatographic measurement of arterial blood elimination displays age attenuation to the same extent, although a monophasic kinetic process (6-7 min). The slow wash-out from brain is thought to involve elimination from intracranial fatty tissue as postulated by others in rabbit brain. Longitudinal relaxation time measurements show monoexponential recovery and essentially identical values for young (1.09 + 0.11 s) and old (1.04 +/- 0.09 s) animals. For dipalmitoylphosphatidylcholine vesicles the monoexponential recovery also suggests rapidly exchanging averaged homogeneous lipid environments for the anesthetic, but the longer T1s (2.75 +/- 0.25 s) imply less restricted mobility compared with brain. Single T2 values were obtained in vivo, indicating either a single compartment or rapid exchange between multiple environments. These measurements were inconsistent, undoubtedly as a result of B1 inhomogeneity. The age-attenuated elimination kinetics for isoflurane are consistent with poorer cardiopulmonary function, whereas the T1 data suggest similar environments for the anesthetic in young and old brain tissue.  相似文献   
84.
85.
Three cases of proved peritoneal carcinomatosis were examined by magnetic resonance imaging (MRI). Air was used to distend the entire gastrointestinal tract via an antegrade method. The findings included seedings along the small intestine, transverse and sigmoid colon, stellate pattern in the mesentery, plaque-like and bulky tumor masses in the mesentery and greater omentum, and focal thickenings along the right subdiaphragmatic parietal peritoneum. Stenosis caused by tumor encasement at the duodenojejunal junction and ileocolic anastomosis were first detected by MRI and later confirmed by barium studies. Ascites was present in all cases. One case showed ascites located only along the left paracolic gutter. This report shows that MRI is also able to demonstrate peritoneal carcinomatosis by using air as a gastrointestinal contrast medium.  相似文献   
86.
Gastric cancer is unusual during pregnancy. Also, because of the physiologic changes that occur with pregnancy, it is rare to see a worsening of peptic ulcers during pregnancy. A patient with an exacerbation of peptic ulcers presented with gastric carcinoma during pregnancy.  相似文献   
87.
88.
Seventy-two patients of chronic obstructive pulmonary disease (COPD) of Qi deficiency syndrome with abnormal immune indices were treated with Yiqi Mianyi Granule (YQMYG) and the efficacy was compared with that of 30 cases treated with Zhenqi fuzheng Granule (ZQFZG) for control. Results showed that the markedly effective rate of symptomatic improvement of Qi deficiency in YQMYG group was 65.3%, the total effective rate 93.1%. 88.6% of the immune indices lower than normal were corrected and 43. 7% of them were normalized, while for indices that were higher than normal the rate were 78.2% and 52.9% respectively. These results suggested that YQMYG could improve symptom of Qi Deficiency markedly, strengthen cellular immunity and regulate immune dysfunction. Its therapeutic efficacy was obviously superior to ZQFZG (P<0.Q5).  相似文献   
89.
Abstract: In the commercially available intravenous formulation of Cyclosporin A (Sandimmun®), polyoxyethylated castor oil (Cremophor®EL) is used as a solubilizing agent. We have recently reported that the acute nephrotoxic effect of this preparation was alleviated by replacing Cremophor®EL with a soybean oil-based fat emulsion in a rat model. To further explore the potential of fat emulsions as carriers for cyclosporin A, data on the in vivo pharmacokinetics and tissue distribution are required. In this study in pigs, the pharmacokinetics of soybean oil-cyclosporin A was compared to that of Sandimmun®. The two formulations seemed bioequivalent, as there were no significant differences in the systemic clearances, volumes of distribution or elimination half-lives. Moreover, the tissue distributions of soybean oil-cyclosporin A and Sandimmun® were compared in rats. These studies also included two additional lipid-based carriers: one based on iodized ester of poppy seed oil and the other on a liposomal preparation. The tissue distributions were found to be similar regardless of the carriers used. Fat emulsion carriers seem to offer possibilities for preparing better tolerated intravenous formulations of cyclosporin A while maintaining the same characteristics concerning pharmacokinetics and tissue distribution.  相似文献   
90.
The posterior tibial flap is a type C fasciocutaneous flap from the medial calf with the posterior tibial vascular bundle as its pedicle. Most of the skin perforators, 1 to 3 in number, can be found in the middle third of the leg, with an average diameter of 0.8 mm and an average length of 22 mm. The posterior tibial artery ranges between 1.5 and 2.0 mm in diameter, although it is absent in 8 percent of limbs. Since the saphenous nerve is taken with the flap, this is an innervated flap. The flap can be transferred as a free flap or a pedicled flap. The reversed-flow pedicled flap has an average pedicle length of 8 cm. The posterior tibial flap is a reliable, large, thin, innervated flap and can be raised with the patient supine. Case reports are presented of six patients who received a free flap transfer and of one patient who received a reversed-flow pedicled flap. There were two cases of heel ulcerations, two crushed hands, one chronic ulceration and osteomyelitis of the tibia, one burn contracture of the neck, and one salvage flap for diabetic gangrene of the hand.  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