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   23074篇
  免费   1135篇
  国内免费   109篇
耳鼻咽喉   114篇
儿科学   374篇
妇产科学   280篇
基础医学   3075篇
口腔科学   576篇
临床医学   1501篇
内科学   5607篇
皮肤病学   311篇
神经病学   1949篇
特种医学   1130篇
外科学   4367篇
综合类   95篇
预防医学   578篇
眼科学   415篇
药学   1768篇
中国医学   80篇
肿瘤学   2098篇
  2023年   103篇
  2022年   228篇
  2021年   428篇
  2020年   208篇
  2019年   304篇
  2018年   439篇
  2017年   321篇
  2016年   370篇
  2015年   384篇
  2014年   526篇
  2013年   653篇
  2012年   1012篇
  2011年   1173篇
  2010年   617篇
  2009年   554篇
  2008年   976篇
  2007年   1155篇
  2006年   1161篇
  2005年   1139篇
  2004年   1061篇
  2003年   1078篇
  2002年   1061篇
  2001年   805篇
  2000年   820篇
  1999年   783篇
  1998年   309篇
  1997年   259篇
  1996年   213篇
  1995年   176篇
  1994年   178篇
  1993年   203篇
  1992年   555篇
  1991年   489篇
  1990年   462篇
  1989年   454篇
  1988年   442篇
  1987年   376篇
  1986年   380篇
  1985年   372篇
  1984年   220篇
  1983年   180篇
  1982年   92篇
  1981年   93篇
  1979年   175篇
  1978年   132篇
  1977年   94篇
  1974年   128篇
  1973年   114篇
  1970年   85篇
  1969年   104篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
A case of a 19-year-old male with leiomyosarcoma of the prostate is reported. He visited our hospital with the chief complaint of urinary retention in December, 1983. Following overall examination, needle biopsy of the prostate gland was performed with the suspicion of sarcoma. Histology of the prostate revealed leiomyosarcoma. Two courses of combined chemotherapy were given, but the tumor continued to enlarge. The patient died in April, 1984, 5 months after the appearance of the first symptom.  相似文献   
93.
94.
We investigated the effects of mild and non-lethal ischemic insult on neuronal death following subsequent lethal ischemic stress in various brain regions, using a gerbil model of bilateral cerebral ischemia. Single 10-min ischemia consistently caused neuronal damage in the hippocampal CA1, CA2, CA3 and CA4, layer III/IV of the cerebral cortex, dorsolateral part of the caudoputamen and ventrolateral part of the thalamus. On the other hand, in double ischemia groups, 2-min ischemic insult 2 days before 10-min ischemia exhibited significant protection in the CA1 and CA3 of the hippocampus, the cerebral cortex, the caudoputamen and the thalamus. Five-min ischemic insult 2 days before 10-min ischemia also showed protective effect in the same areas as those of 2-min ischemia except for the CA1 region of the hippocampus, while 1-min ischemic insult exhibited no protective effect in any brain regions. In the immunoblot analysis, both 2- and 5-min ischemia caused increased synthesis of heat shock protein 72 (HSP 72) in the hippocampus, but 1-min ischemia did not. The present study demonstrated that the ‘ischemic tolerance’ phenomenon was widely found in the brain and also suggested that ischemic treatment severe enough to cause HSP 72 synthesis might be needed for induction of ‘ischemic tolerance’.  相似文献   
95.
To examine the effects of transient hyperprolactinemia on in vitro fertilization and embryo transfer, 61 cycles in 50 euprolactinemic ovulatory women with irreparable tubal diseases were stimulated with clomiphene (CC) alone or CC and human menopausal gonadotropin followed by human chorionic gonadotropin (hCG). Serum prolactin (PRL) increased after hCG administration with peak values of 45.4 +/- 4.2 ng/ml on the day of laparoscopic oocyte aspiration. The highest serum estradiol (E2) concentration was found on the day before PRL peak and serum progesterone (P) began to increase after hCG injection concomitant with the PRL rise. The group having 50 ng/ml or more of PRL (34 cycles) had significantly higher levels of E2 during preovulatory and early luteal phase compared to those of the group having less than 50 ng/ml of PRL (27 cycles) but there was no significant difference between the P levels in the two groups. In the higher PRL group 72 (62.1%) of 116 collected oocytes were fertilized and 6 (20.0%) conceived. In the lower PRL group 45 oocytes (58.4%) of 77 were fertilized and 3 (12.5%) became pregnant. These data suggest that elevated serum PRL concentrations may have no effect on fertilization of oocytes in vitro or embryonic development.  相似文献   
96.
The 2-deoxy-D-[1-14C]glucose ([14C]DG) method was used to examine the effects of the relatively selective sigma ligand 1,3-di-o-tolylguanidine (DTG) on cerebral metabolism in freely moving rats. Each animal received an i.p. injection of DTG (0.2, 1, or 5 mg/kg) or normal saline 20 min prior to the infusion of [14C]DG. DTG induced dose-dependent changes in local cerebral glucose utilization (LCGU) in several motor and limbic structures. Most structures showed increases in LCGU, with a maximum effect at 1 mg/kg. The most profound increases in LCGU were observed in brain regions that are rich in sigma receptors. These included cerebellar and related nuclei (interpositus, lateral and medial cerebellar n., vestibular n., olivary n.), ambiguus n., superior colliculus (superior layers), hippocampus (CA2, CA3, DG), n. basalis of Meynert interpeduncular n., and the substantia nigra pars compacta and pars reticulata. No significant decreases in glucose utilization were observed at any dose. Although the areas affected by DTG are similar to those previously reported for other sigma ligands, future studies employing a range of doses for additional selective sigma ligands must be carried out in order to confirm whether these changes in LCGU were sigma-mediated.  相似文献   
97.
Central cholinergic hypofunction causes the disruption of spatial cognition, while cholinomimetics improve this disruption in rats. Scopolamine (0.5 mg/kg, i.p.) has also been reported to disrupt radial maze performance in rats. Nebracetam (WEB 1881 FU), a new nootropic candidate, was able to correct this scopolamine-induced disruption of spatial cognition at the dose of 10 mg/kg, p.o. Furthermore, nebracetam enhanced oxotremorine-induced tremors in mice. These results indicate that nebracetam has a cholinergic enhancing effect. The scopolamine-induced disruption of spatial cognition has been previously reported to improve not only by cholinomimetics but also by brain noradrenergic drugs such as L-threo-DOPS and amantadine. Nebracetam reversed the change of brain noradrenaline contents in the frontal cortex and hippocampus in which the noradrenaline content decreased by treatment with scopolamine. Nebracetam also decreased the delta 9-tetrahydrocannabinol (6 mg/kg, i.p.)-induced disruption of spatial cognition, which was reported to be related to the lymbic noradrenergic function. These results suggest that the cognitive enhancing effect of nebracetam involves not only cholinergic mechanisms but also involves lymbic and hippocampal noradrenergic mechanisms.  相似文献   
98.
PURPOSETo describe MR and CT features of germinoma originating in the basal ganglia and thalamus and to discuss the roles of each modality for its diagnosis.METHODSMR and CT studies of six cases of germinomas, five of which were histologically proved, were retrospectively reviewed. T1-weighted, T2-weighted, and contrast-enhanced T1-weighted conventional spin-echo images, and unenhanced and contrast-enhanced CT images were evaluated.RESULTSTypically, the tumor consisted of an irregular solid area with contrast enhancement and various-size cysts. Cystic components were found in five cases and calcification in four. Intratumoral hemorrhage was noted in one. Ipsilateral cerebral hemiatrophy and brain stem hemiatrophy were noted in three cases each. MR was superior to CT in evaluating precise tumor extension, cystic components, and intratumoral hemorrhage, although in one case, extension of the tumor was better defined on CT in its early stage. Calcification was difficult to identify by MR alone. The solid components of the tumors generally showed slightly high density on CT, which seemed to be characteristic compared with nonspecific intensity pattern on MR.CONCLUSIONThe combination of CT and MR findings allows early detection and appropriate diagnosis of the mass in the basal ganglia and/or thalamus.  相似文献   
99.
Primary aqueductal stenosis is one of the main causes of congenital hydrocephalus in humans and experimental models. The congenitally hydrocephalic rat strain LEW/Jms is one such model. In this report, we describe further detailed histological features of periaqueductal structure, including the posterior commissure, subcommissural organ (SCO), and ependyma, and discuss the changes in these structures in relation to the cause of hydrocephalus. Coronal sections of the aqueduct in normal rats showed that the usual ependyma was absent in the center of the base facing the dorsal side, which was replaced by tall columnar cells. On the other hand, in hydrocephalic rats the ependyma encircled the aqueductal cavity. In midline sagittal sections, normal and hydrocephalic rats showed the SCO, although the SCO in hydrocephalic rats was shorter than in normal rats. There was also a marked difference between normal and hydrocephalic rats in the dorsoventral dimension of the rostral midbrain. In hydrocephalus, this dimension was large in comparison with normal rats. The superior collicular commissure located caudal to the posterior commissure ran along the ventral side of the midbrain in rats with hydrocephalus, and there was a cell-depleted area just dorsal to the superior collicular commissure. The same findings were observed from the 17th day of gestation until the postnatal period. Although the role of the SCO has been widely discussed from the viewpoint of secretory function, the present study indicated that this organ might be involved in the formation of the shape of the aqueduct.  相似文献   
100.
The effects of a weakly acidic polysaccharide fraction, GL-4, from the leaves of Panax ginseng C. A. Meyer on various experimental gastric ulcer models in mice and rats have been studied. Oral administration of GL-4 at doses of 50 to 200 mg/kg inhibited the formation of the gastric lesions induced by necrotizing agents such as HCl/ethanol and ethanol in a dose-dependent manner. This protective effect was observed not only upon oral but also upon subcutaneous administration of GL-4 (50-100 mg/kg). GL-4 also inhibited the formation of gastric ulcers which were induced by water immersion stress, indomethacin, or pylorus-ligation. The contents of prostaglandin E2 in the gastric juice from rats were not influenced by oral administration of GL-4. The protective action of GL-4 against HCl/ethanol-induced gastric lesions was not abolished by pretreatment with indomethacin. When GL-4 (100 mg/kg, p.o.) was administered into pylorus-ligated rats, both gastric acidity and pepsin activity in the gastric juice decreased significantly.  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