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   30948篇
  免费   2641篇
  国内免费   866篇
耳鼻咽喉   229篇
儿科学   309篇
妇产科学   304篇
基础医学   1480篇
口腔科学   787篇
临床医学   2640篇
内科学   4021篇
皮肤病学   684篇
神经病学   984篇
特种医学   3059篇
外科学   2890篇
综合类   3499篇
现状与发展   1篇
预防医学   2941篇
眼科学   251篇
药学   5049篇
  18篇
中国医学   774篇
肿瘤学   4535篇
  2024年   42篇
  2023年   356篇
  2022年   642篇
  2021年   1174篇
  2020年   1172篇
  2019年   1306篇
  2018年   1307篇
  2017年   1085篇
  2016年   1141篇
  2015年   1177篇
  2014年   1988篇
  2013年   2545篇
  2012年   1890篇
  2011年   1934篇
  2010年   1525篇
  2009年   1560篇
  2008年   1478篇
  2007年   1467篇
  2006年   1283篇
  2005年   1133篇
  2004年   924篇
  2003年   844篇
  2002年   728篇
  2001年   588篇
  2000年   506篇
  1999年   422篇
  1998年   409篇
  1997年   408篇
  1996年   289篇
  1995年   327篇
  1994年   220篇
  1993年   226篇
  1992年   172篇
  1991年   176篇
  1990年   165篇
  1989年   154篇
  1988年   143篇
  1987年   148篇
  1986年   125篇
  1985年   207篇
  1984年   186篇
  1983年   157篇
  1982年   134篇
  1981年   127篇
  1980年   119篇
  1979年   117篇
  1978年   54篇
  1977年   39篇
  1976年   43篇
  1975年   21篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Rabbits are the experimental animals of choice in many studies including flaps, wounds, and topical trials for new pharmacological agents. Because the topical drugs and other materials used for dressing are irritating to the animal, they tend to remove dressings, bandages, drapes, insensate flaps, and also topical drugs by scratching, licking, and biting if they are within the reach of the animal. In this study, we report an easy to prepare, user-friendly, comfortable, and cheap dressing protector called a dressing shield to prevent these problems.  相似文献   
82.
阿片肽及其受体系统在缺血性脑损伤的病理生理发展过程中具有非常重要的作用。其在缺血性脑损伤中的作用尚存争议,本文综述了阿片肽及其受体系统在缺血性脑损伤中的作用及其可能机制,有助于探索阿片肽在围术期的合理应用,为缺血性脑损伤防治研究提供新方向。  相似文献   
83.
Overactive bladder (OAB) is a prevalent and costly condition that can affect any age group. Typical symptoms include urinary urgency, frequency, incontinence and nocturia. OAB occurs as a result of abnormal contractions of the bladder detrusor muscle caused by the stimulation of certain muscarinic receptors. Therefore, antimuscarinic agents have long been considered the mainstay of pharmacologic treatment for OAB. Currently, there are five such agents approved for the management of OAB in the United States: oxybutynin, tolterodine, trospium, solifenacin and darifenacin. This article summarizes the efficacy, contraindications, precautions, dosing and common side effects of these agents. All available clinical trials on trospium, solifenacin and darifenacin were reviewed to determine its place in therapy.  相似文献   
84.
The use of N, O-bisFmoc-N-(2-hydroxy-4-methoxybenzyl) amino acid derivatives in the synthesis of peptides with difficult sequences has already been described. With these amino acid derivatives the reversible protecting group 2-hydroxy-4-methoxybenzyl (Hmb) for the backbone amide bonds of peptide chains is introduced, and thus the aggregation due to hydrogen-bond interchain association is inhibited. This paper describes the synthesis and use of Fmoc-N-(2-hydroxy-4-methoxybenzyl)amino acid derivatives as an alternative means of introducing Hmb backbone protection. These new monoFmoc derivatives were obtained in higher yield than the bisFmoc derivatives. Coupling yields to the amino peptide resin were the same as those obtained with bisFmoc derivatives, under the TBTU/HOBt/DIEA conditions. We also compared different syntheses of a difficult peptide with the Fmoc approach [triple coupling, capping, use of chaotropic agents, backbone protection using monoFmoc (Hmb)Ala] and with optimized Boc chemistry. Both the backbone protection and optimized Boc chemistry approaches gave the desired product in excellent yield and purity. © Munksgaard 1997.  相似文献   
85.
The facile thiolytic cleavage of the O-2,4-dinitrophenyl (Dnp) tyrosine bond was applied to the solid-phase synthesis of the 22-amino acid residue peptide H-Asp-Ala-Val-Tyr -Thr-Gly-Leu-Asn-Thr-Arg-Asn-Gln-Glu-Thr-Tyr -Glu-Thr-Leu-Lys-His-Glu-Lys-OH, corresponding to positions 62-83 in the chain of the type 1 receptor for Fcε, domains expressed on the rat mucosal-type mast cells (line RBL-2H3). A method for the spectrophotometric determination of insoluble O-Dnp as well as of unprotected phenolic moieties of tyrosine was developed. It is based on monitoring S-Dnp-2-mercaptoethanol, produced upon O-Dnp thiolysis by 2-mercaptoethanol. © Munksgaard 1995. Dedicated to the memory of Dr. Susumu Funakoshi, a dear friend and a leader in peptide chemistry.  相似文献   
86.
Summary The objective of this study was to evaluate the effect of two non-steroid anti-inflammatory drugs, indomethacin and metamizole, on ureteral peristalsis during acute occlusion similar to the situation in renal colic. In 12 pentobarbital anesthetized sheep, both ureters were cannulated and the frequency of ureteral contractions, urine flow, mean ureteral pressure and blood pressure were recorded during 10-min control and i.v. drug administration periods. Both indomethacin (1–2 mg/kg) and metamizole (60–120 mg/kg) showed a dose dependent reduction in peristaltic frequency without reduction of the mean pressure. In addition, the pressure amplitude of the peristaltic waves was also lowered, particularly with indomethacin. Only indomethacin reduced the urine flow. Arterial blood pressure was elevated by both drugs, particularly after the first dose of indomethacin. It can be concluded that indomethacin and metamizole reduce ureteral peristaltic frequency, probably blocking the impulse transmission at the ureteropelvic junction.For the partial fulfillment of a Master's degree in Pharmacology  相似文献   
87.
氟西汀与阿米替林治疗105例抑郁障碍病人的双盲对照试验   总被引:6,自引:4,他引:2  
目的:评价国产氟西汀的抗抑郁作用及安全性。方法:采用随机、双盲对照、多中心研究,分为国产氟西汀组57例(男性22例,女性35例;年龄40±s13a),口服氟西汀20mg,qd,阿米替林57例(男性27例,女性30例;年龄40±14a),口服阿米替林75mg,bid,疗程6wk。结果:氟西汀治疗抑郁障碍的疗效与阿米替林相当,总有效率分别为85%及92%(P>0.05);氟西汀组的主要副作用有口干、便秘、恶心、心动过速等,但较之阿米替林程度轻且发生率低。结论:氟西汀的抗抑郁作用与阿米替林相当,副作用少,服用方便。  相似文献   
88.
The involvement of children in research studies is historically fraught with difficulties. Experiments on children without their consent or knowledge have been carried out in the past and thus the need for stringent ethical control is undoubtedly necessary. However this paper argues that the need to protect children from unethical research has somehow become entwined in the web of secrecy that surrounds the very nature of child abuse. In the name of 'protection' are children in danger of not having their voice heard?

In the foreword to 'Listening to Children' (Alderson, 1995) Roger Singleton writes, 'much research is carried out on and about children, but seldom with children. Children themselves are often strangely silent'. This paper draws on recent literature on the institutional abuse of young people in residential care and the lack of voice that those abused in residential care have traditionally had, suggesting that their silence is not 'strange' but perhaps contrived.

This paper does not repeat the work of Alderson (1995) and make suggestions as to how research with children may best be carried out, but seeks to address the issues in relation to research with children who are in institutions.  相似文献   
89.
辐射是影响黑色素细胞结构和功能的一个重要的环境因素。本文综述了近年来辐射对小鼠黑色素细胞的生物效应研究进展,并对今后的发展予以展望。  相似文献   
90.
Summary The ESR spectra produced in irradiated dentin have been studied over a range of incident radiation energies from 50 kVp to 25 MVp. The behavior of the dentin ESR signal strength is similar to that of enamel as a function of the energy of the incident radiation. The magnitude of the dentin ESR signals are, however, up to 10 times smaller than the signals of dental enamel for a given radiation energy. The possible contributions of radiation interaction coefficients, chemical structure, and crystallite size to the differences in ESR spectra are discussed.  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