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   42790篇
  免费   2877篇
  国内免费   1156篇
耳鼻咽喉   114篇
儿科学   621篇
妇产科学   346篇
基础医学   5432篇
口腔科学   730篇
临床医学   2973篇
内科学   4943篇
皮肤病学   324篇
神经病学   3903篇
特种医学   1057篇
外国民族医学   2篇
外科学   1679篇
综合类   3474篇
现状与发展   2篇
预防医学   3908篇
眼科学   223篇
药学   11396篇
  12篇
中国医学   4162篇
肿瘤学   1522篇
  2024年   103篇
  2023年   633篇
  2022年   972篇
  2021年   1532篇
  2020年   1365篇
  2019年   1344篇
  2018年   1312篇
  2017年   1456篇
  2016年   1334篇
  2015年   1253篇
  2014年   2197篇
  2013年   3740篇
  2012年   1974篇
  2011年   2404篇
  2010年   1605篇
  2009年   1907篇
  2008年   1855篇
  2007年   1866篇
  2006年   1575篇
  2005年   1410篇
  2004年   1239篇
  2003年   1091篇
  2002年   963篇
  2001年   902篇
  2000年   698篇
  1999年   694篇
  1998年   704篇
  1997年   607篇
  1996年   597篇
  1995年   576篇
  1994年   484篇
  1993年   468篇
  1992年   473篇
  1991年   438篇
  1990年   398篇
  1989年   403篇
  1988年   356篇
  1987年   348篇
  1986年   334篇
  1985年   458篇
  1984年   407篇
  1983年   281篇
  1982年   362篇
  1981年   285篇
  1980年   285篇
  1979年   210篇
  1978年   227篇
  1977年   161篇
  1976年   196篇
  1975年   80篇
排序方式: 共有10000条查询结果,搜索用时 123 毫秒
101.
对不同来源的脂肪酶进行了系统的筛选,并根据位置专一性的差别将脂肪酶分为1,3 特异的、1,3 选择性和非选择性的3类.采用LipozymeRMIM在无溶剂系统中催化甘油、脂肪酸合成1,3 sn 甘油二酯.研究表明脂肪酸、底物醇种类、温度、水分活度对LipozymeRMIM的活力有明显的影响.  相似文献   
102.
As an ongoing effort to elucidate the mechanisms involved in the calcium-dependent fertility regulation process, the viscoelastic properties of the mucus obtained from lamb cervix and human semen, as well as their water and total protein contents after exposure to EDTA, a chelating agent, or Nonoxynol-9 (N-9), a spermicidal agent, were examined. The viscosity was measured using a Cone Plate Digital Viscometer, while the water and total protein contents were determined by the lyophilization process and the Lowry method, respectively. The significant changes in the rheological properties of mucus, such as its viscosity and the water content, upon exposure to EDTA were demonstrated. The viscosity of cervical mucus and human semen were significantly increased by EDTA treatment (as compared to the controls): lamb cervical mucus (2.9 ± 0.3 vs. 2.2 ± 0.3 cps) and human semen (5.0 ± 0.3 vs. 4.3 ± 0.3 cps), respectively. The hydration rate was decreased by EDTA treatment as compared with the control (93.6 ± 0.7 vs. 96.8 ± 0.8%). Among tested samples, the reduction in the percentage of sperm penetration through the cervical mucus was the highest in the mucus containing EDTA, which had the lowest water content (93.6 ± 0.7%), indicating that there is a positive relationship between the hydration rate of the cervical mucus and its ability to permit the penetration of spermatozoa. This result indicates that spermicidal activity exerted by high concentrations of EDTA is in part due to its effect on the rheological properties of cervical mucus or semen.  相似文献   
103.
刺山柑是一种山柑属植物,在多个国家药用。传统用作驱虫药、泥敖剂、利尿剂、通便剂、止痛剂和滋补剂。在我国新疆、西藏地区被广泛用于治疗痛风、类风湿性关节炎等。现代研究发现该植物含有挥发油、芥子油苷类、生物碱、萜类、黄酮类等多种成分,具有保肝、抗炎、抗病毒、抗氧化、免疫调节、降血糖、降血脂等多种生物活性。现对该植物化学成分和研究进展进行综述,以利于该植物的研究、开发与利用。  相似文献   
104.
Summary The chromophore-modified derivative of doxorubicin, 4-demethyl-6-0-methyl-doxorubicin, has been tested for antitumor activity in a range of experimental murine tumor systems. In contrast to the inactive 6-0-methyl derivative of daunorubicin, 4-demethyl-6-0-methyl-doxorubicin provided antitumor effects comparable to that of the parent compound. In addition, detailed DNA-interaction studies showed that the doxorubicin derivative retains the ability to bind DNA by the intercalation mechanism. However, the binding affinity was appreciably reduced following structural modification in the anthraquinone chromophore. On the basis of the proposed models of intercalation, these results could be rationalized in terms of steric influence of the bulky methoxy group. The results of this study are in agreement with the correlation already observed between DNA binding and relative antitumor activity of anthracyclines.  相似文献   
105.
1. The mechanism of action of drugs might change according to the test used. Several noradrenergic drugs were tested in order to understand their implication in the mobility tests.

2. It was found that clonidine, an Alpha 2 agonist, acted differently according to the tast used. It provoked sedation in spontaneous activity test, and anti-immobility effects in the other tests.

3. Tall suspension test is able to show the double acting of clonidine.

4. Idazoxan might act either as an alpha 2 antagonist or as partial alpha 2 agonist. TST shown the unexpected partial alpha agonist effect of the molecule.

5. Forced swimming test is more specific for predicting antidepressant activity than tail suspension test which is close to a spontaneous activity model.  相似文献   

106.
明中后期,王学盛极一时,程朱式微,以顾宪成、高攀龙为首的东林学人以东林书院为依托,起而纠王学空疏之流弊。究明儒学道脉,“提撕天下万世”,成为其讲经活动的主要目的,儒家经典成为其讲经活动的主要内容,体现了学术与政治相结合的道德救世理念。  相似文献   
107.
以国内外发表的文献为材料,简述甘草酸在抗病毒方面研究进展。对甘草酸抗肝炎病毒、疱疹属病毒、HIV病毒及SAS病毒等机制进行了综述。甘草酸抗病毒活性强,能抑制多种不相关的DNA、RNA病毒的生长,并且不影响正常细胞的活性。但由于其脂溶性和生物利用度低,及长期使用会引起一些不良反应,而限制了它的应用。总的来说,甘草酸在抗病毒方面的前景良好,有其独特优势,但其抗病毒机制复杂,很多方面有待进一步研究。  相似文献   
108.
目的探讨不同摄食控制方法对荷瘤小鼠生存期的影响。方法摄食控制组分别为每日限食2.0 g(DR)、隔1日断食限食4.0 g(IF)、隔2日断食限食6.0 g(SF)和隔1日断食不限食(IF1)4种方法,正常摄食为空白对照组(AL)。观察各组小鼠的体重变化和平均存活天数。结果DR组和IF组平均存活天数分别为19.52±5.24 d和17.96±4.49 d,比对照AL组15.75±1.83 d明显延长(P<0.001和P<0.01)。结论摄食控制恰当,可明显抑制肿瘤细胞的生长、延长荷瘤小鼠的生存期并提高生存质量。  相似文献   
109.
The methanolic fraction of P. indica root extract was found to possess significant antiulcer activity in different experimental animal models. In preventive antiulcer tests, significant protective actions in acetylsalicylic acid, serotonin and indomethacin-induced gastric lesions were observed in experimental rats. The extract also afforded significant protection to chemically-induced duodenal lesion in guineapigs. Significant enhancement of healing process in acetic acid-induced chronic gastric lesions were also observed in the extract-treated animals.  相似文献   
110.
The pressure variations at the maximal urethral closure pressure (MUCP) were continuously recorded in healthy female volunteers by means of a two-point microtip transducer catheter for one hour. Before the investigation a normal voiding was assured objectively and bladder instability was excluded. All women showed pressure variations both at the MUCP and more distally. The pressure variations, from 3 to 66 cm H2O, showed rhythmicity and three frequency ranges could be identified. Slow pressure waves with a frequency of one in eight to 19 minutes were observed. Relatively fast-pressure waves were observed (one every one to four minutes) and relatively fast-frequency pressure waves were observed (rate: one to eight per minute). The pressure variations of the urethra seem to be an aspect of normal urethral physiology possibly contributing to continence and urinary tract infection prevention.  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