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   12126篇
  免费   662篇
  国内免费   66篇
耳鼻咽喉   179篇
儿科学   202篇
妇产科学   105篇
基础医学   1654篇
口腔科学   255篇
临床医学   798篇
内科学   3339篇
皮肤病学   164篇
神经病学   847篇
特种医学   496篇
外科学   1872篇
综合类   63篇
一般理论   3篇
预防医学   314篇
眼科学   320篇
药学   941篇
中国医学   31篇
肿瘤学   1271篇
  2023年   120篇
  2022年   212篇
  2021年   326篇
  2020年   197篇
  2019年   268篇
  2018年   338篇
  2017年   183篇
  2016年   274篇
  2015年   268篇
  2014年   335篇
  2013年   396篇
  2012年   653篇
  2011年   745篇
  2010年   424篇
  2009年   331篇
  2008年   608篇
  2007年   621篇
  2006年   603篇
  2005年   617篇
  2004年   580篇
  2003年   549篇
  2002年   525篇
  2001年   345篇
  2000年   319篇
  1999年   283篇
  1998年   123篇
  1997年   92篇
  1996年   87篇
  1995年   74篇
  1994年   84篇
  1993年   65篇
  1992年   209篇
  1991年   167篇
  1990年   174篇
  1989年   168篇
  1988年   165篇
  1987年   158篇
  1986年   136篇
  1985年   112篇
  1984年   100篇
  1983年   74篇
  1982年   45篇
  1981年   39篇
  1979年   75篇
  1978年   54篇
  1976年   44篇
  1972年   45篇
  1971年   42篇
  1970年   42篇
  1968年   46篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
A new tetracyclic diterpenoid, scopadulciol [3], together with 6-methoxybenzoxazolinone, glutinol, and acacetin, was isolated from the 70% EtOH extract of Scoparia dulcis collected in Taiwan. Its structure was elucidated to be 6 beta-benzoyl-12-methyl-13-oxo-9(12)a,9(12)b-dihomo-18-podocarpanol on the basis of spectral data. It mildly inhibited hog gastric H+, K(+)-ATPase. Examination of the inhibitory activities of derivatives of scopadulcic acid B [2], including 3, revealed that methylation of the carboxyl group and introduction of an acetyl group or oxime at C-13 or C-18 markedly enhanced the inhibitory activity, while debenzoylation reduced the activity. Among the 30 compounds tested, compound 12, a methyl ester of scopadulcic acid B [2], showed the most potent activity.  相似文献   
993.
The morphology of the lamellae in non-isothermally crystallized linear low-density polyethylene (LLDPE), conventional high-pressure low-density polyethylene (HP-LDPE), and a high-density polyethylene (HDPE) sample was investigated by transmission electron microscopy (TEM). LLDPE exhibits clearly two different types of lamellae, i.e., thick, long, and straight lamellae like those of HDPE, and thin, short, and curved lamellae which grow among the former ones. Also LLDPE shows the broadest distribution of the values for the lamella thickness among the three types of polyethylenes mentioned. The average lamella thickness decreases in the order HDPE > LLDPE > HP-LDPE. Fractions were used to study the effects of the kind and the degree of short chain branching (SCB) and of the molecular weight in the range from 4100 to 3,1·105. SCB has a predominant influence on the lamella thickness as well as on the shape, while the molecular weight does not largely affect lamella thickness but affects the shape of the lamellae. Further it was revealed from TEM observation that the isobutyl branch decreases lamella thickness more effectively than does the ethyl branch. This is in accordance with results from small-angle X-ray and differential scanning calorimetry measurements.  相似文献   
994.
Slow reacting substance of anaphylaxis (SRS-A) has been shown to be one of the major mediators in hypersensitive reactions and to be composed of leukotriene (LT) C4, LTD4 and LTE4. In the present study, we examined the properties of SRS-A released from sensitized guinea pig lungs by antigen and SRS released from rat peritoneal exudate cells and from human leucocytes by ionophore A23187 (0.5 and 0.2 microgram/ml, respectively). By the incubation with SRS-A, SRS and LTs with arylsulfatase (type V) in pH 5.7 buffered solution at 37 degrees C for 30 min, SRS-A and LTD4 were greatly inactivated and rat SRS was slightly inactivated, but human SRS and LTC4 were not inactivated at all. The same results were obtained when aminopeptidase was used in place of arylsulfatase. Moreover, when SRS-A, LTC4 and LTD4 were incubated with 0.02 mg/ml of gamma-glutamyltranspeptidase (gamma-GTP) pH 8.0 buffered solution at 37 degrees C for 30 min, the activities of SRS-A and LTD4 were slightly decreased, but those of SRS and LTC4 were obviously potentiated. On the other hand, incubation with a large amount of gamma-GTP (0.2 mg/ml) a dose at which this enzyme preparation showed clear aminopeptidase activity, SRS-A, SRS, LTC4 and LTD4 were obviously inactivated. In addition, we found a peak of LTD4 in guinea pig SRS-A, that of LTC4 in human SRS, and that of LTC4 in rat SRS on high performance liquid chromatograms. From these results, we demonstrated that guinea pig lung SRS-A is mainly composed of LTD4, human leukocyte SRS is mainly LTC4, and rat peritoneal SRS is composed of both LTC4 and LTD4. The inactivation of LTD4 and SRS-A by arylsulfatase may be due to aminopeptidase contamination in the enzyme preparation.  相似文献   
995.
An attempt was made to develop a safe, efficacious live recombinant vaccine using low neurovirulent strains of vaccinia virus: LC16m0 (m0) or LC16m8 (m8). Recombinant vaccinia virus (RVV) was constructed by inserting the hepatitis B surface antigen (HBsAg) gene fused to a 7.5 kDa protein promoter (7.5 kDa promoter) within the vaccinia virus thymidine kinase (TK) gene using the m0 or m8 strain as vectors. These RVVs expressed significant amounts of HBsAg (1.1 microgram/2 X 10(5) cells) consisting of 24.5 and 28 kDa (glycosylated) proteins. HBsAg produced by RVV (vaccinia HBsAg) had physical properties very similar to plasma-derived HBsAg. Considering the safety of RVVs from m0 or m8 that have been constructed with HBsAg without the addition of a promoter and the high induction of anti-HBs antibody with RVV from m0 strain in rabbits, the RVVs constructed in the present study are likely to form the basis of a safe live RVV vaccine for hepatitis B virus (HBV).  相似文献   
996.
997.
A 68-year-old male presented with neurological deterioration after a lucid interval following head trauma. Computed tomographic (CT) scans on admission demonstrated a subdural hematoma in the right frontotemporal region accompanied by subarachnoid hemorrhage in the right Sylvian and interhemispheric fissures. The subdural hematoma was removed via a right frontotemporoparietal craniectomy. However, immediate postoperative CT scans revealed hemorrhage in the third and both lateral ventricles, apparently separate from the primary hemorrhages. Decompressive rupture of damaged subependymal veins is suggested as the cause of the delayed traumatic intraventricular hemorrhage.  相似文献   
998.
999.
A 37-year-old woman was admitted to the hospital with the complaint of progressive horizontal diplopia of six years' duration when viewing distant objects. On admission she had a slight left convergent strabismus. Homonymous diplopia was present beyond 50 cm and increased on distance fixation. Both eyes were fully mobile in the horizontal plane with a mild decrease in the velocity of horizontal eye movement to the left, and slight impairment of upward eye movement. The left eye did not fully adduct during convergence. The right pupil was slightly larger than the left. Prism cover test showed 6 delta esophoria at 30 cm and 14 delta esophoria at 5 m. The Hess chart showed a convergent deviation. MRI revealed a small right-side paramedian lesion of the midbrain tegmentum lying ventral to the aqueduct of Sylvius, at the level between the superior colliculi and the intercollicular area. A venous angioma with arteriovenous shunts in the right midbrain was diagnosed by angiography. We suggest that lesions that damage the divergence neurons in the tegmentum of the midbrain and also interrupt the supranuclear fibers having an inhibitory effect on the convergence neurons may produce homonymous diplopia on distant fixation combined with the esotropia.  相似文献   
1000.
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