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   13230篇
  免费   813篇
  国内免费   285篇
耳鼻咽喉   542篇
儿科学   257篇
妇产科学   382篇
基础医学   1804篇
口腔科学   544篇
临床医学   1521篇
内科学   1186篇
皮肤病学   93篇
神经病学   1166篇
特种医学   351篇
外国民族医学   1篇
外科学   1757篇
综合类   1676篇
预防医学   1015篇
眼科学   302篇
药学   1036篇
  7篇
中国医学   312篇
肿瘤学   376篇
  2024年   17篇
  2023年   144篇
  2022年   332篇
  2021年   443篇
  2020年   400篇
  2019年   313篇
  2018年   310篇
  2017年   355篇
  2016年   387篇
  2015年   416篇
  2014年   794篇
  2013年   857篇
  2012年   741篇
  2011年   792篇
  2010年   642篇
  2009年   626篇
  2008年   570篇
  2007年   585篇
  2006年   519篇
  2005年   466篇
  2004年   412篇
  2003年   367篇
  2002年   314篇
  2001年   254篇
  2000年   234篇
  1999年   209篇
  1998年   245篇
  1997年   192篇
  1996年   195篇
  1995年   199篇
  1994年   167篇
  1993年   137篇
  1992年   123篇
  1991年   149篇
  1990年   118篇
  1989年   117篇
  1988年   132篇
  1987年   115篇
  1986年   104篇
  1985年   124篇
  1984年   116篇
  1983年   103篇
  1982年   81篇
  1981年   82篇
  1980年   82篇
  1979年   60篇
  1978年   55篇
  1977年   34篇
  1976年   29篇
  1973年   18篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
中药赤芍对球囊损伤术后血管重构的干预研究   总被引:4,自引:0,他引:4  
目的 观察中药赤芍防止球囊损伤术后血管重构作用。方法 新西兰白兔随机分为对照组、单纯高脂组、赤芍高剂量组、低剂量组。高脂喂养6周建立动脉粥样硬化模型,行颈动脉球囊损伤术,8周时取材作病理形态学检查。结果(1)与高脂组比较,赤芍高、低剂量组增生内膜面积、中层面积,内膜、中膜、外膜PCNA阳性着色均显著减少(P<0.05或P<0.01)。(2)各组内皮增生成分主要为平滑肌细胞;巨噬细胞阳性着色主要分布在外膜,与高脂组比较,赤芍高、低剂量组阳性着色较少。(3)高脂组动脉损伤侧外膜Ⅰ型胶原增多,赤芍组Ⅰ型胶原增加较少。结论 赤芍对高脂喂养兔颈动脉球囊损伤术后血管重构有显著防止作用。  相似文献   
122.
Approximately 5% of children with neural tube defects (NTDs) have a congenital heart defect and/or cleft lip and palate. The cause of isolated meningomyelocele, congenital heart defects, or cleft lip and palate has been largely thought to be multifactorial. However, chromosomal, teratogenic, and single gene causes of combinations of NTDs with congenital heart defects and/or cleft lip and palate have been reported. We report on 3 patients with meningomyelocele, congenital heart defects, and 22q11 deletions. Two of the children had the clinical diagnosis of velo-cardio-facial syndrome (VCFS); both also have bifid uvula. The third child had DiGeorge sequence (DGS). The association of NTDs with 22q11 deletions has not been reported previously. An accurate diagnosis of the 22q11 deletions is critical as this micro-deletion and its associated clinical problems is transmitted as an autosomal dominant trait due to the inheritance of the deletion-bearing chromosome. We recommend that all children with NTDs and congenital heart defects, with or without cleft palate, have cytogenetic and molecular studies performed to detect 22q11 deletions. © 1994 Wiley-Liss, Inc.  相似文献   
123.
Summary The ultrastructure of neuroglial fatty metamorphosis (GFM) has been investigated in the telencephalic white matter of 12 premature and mature infants (gestational age 22–40 weeks; survival 0–96 days). GFM was found in all cases apart from a 22-week-old fetus, and involves predominantly astrocytic cells (68.8%), then glioblasts (43.5%), but only 7.4% of oligodendrocytes. GFM, therefore, seems to be independent of the myelination process and indicates the vulnerability of the immature neuroglial population in the metabolic and circulatory disorders of the perinatal period. Since GFM is found in almost all children dying within the early postnatal period, this subtle alteration reflects a special form of minimal brain damage. The relationship between GFM, astrocytic hypertrophy and periventricular leucomalacia and their role in the telencephalic leucoencephalopathy are discussed.
Zusammenfassung Die Gliazellverfettung im unreifen Großhirn-Marklager wurde bei 12 Kindern ultrastrukturell untersucht (Gestationsalter 22–40 Wochen; Überlebenszeit 0–96 Tage). Die fettige Metamorphose der Neuroglia (Virchow) fand sich in allen Fällen, ausgenommen den 22 Wochen alten Feten, und betrifft vorwiegend junge Astrozyten (68,8%), ferner zu 43,5% unreife Vorstufen, jedoch nur zu 7.4% die (z.Z. der Geburt erst in Erscheinung tretende) Oligodendroglia. Die Fett-Metamorphose der unreifen Glia stellt einen sensiblen Indikator für metabolisch-zirkulatorische Störungen der Perinatalperiode dar und erfolgt unabhängig von dem Prozeß der Markscheidenbildung. Zusammen mit einer oft auffälligen Astroglia-Proliferation ist die intracytoplasmatische Akkumulation nicht membrangebundener Lipide Ausdruck einer temporären Differenzierungsstörung der unreifen Neuroglia. Die resultierende Reifungsdissoziation mit Unterdrückung der oligodendrozytären Zellinie führt zur retardierten Markscheidenbildung und dem Bild der telencephalen Leucoencephalopathie.
  相似文献   
124.
The role of COX-2 in angiogenesis and rheumatoid arthritis   总被引:4,自引:0,他引:4  
Recent evidence suggests that cyclooxygenase (COX)-2 is a mediator of angiogenesis, and COX-2 activity is known to be upregulated in the rheumatoid arthritis (RA) synovium. We examined whether mediation of angiogenesis by COX-2 was occuring in cells of the RA synovium and in microvascular endothelial cells (ECs) that are similar to those found in the RA synovium. We demonstrate that rofecoxib, a selective COX-2 inhibitor, acts directly on human dermal microvascular ECs (HMVECs) to inhibit their chemotactic and tube forming ability. Likewise, pretreatment of HMVECs with rofecoxib significantly inhibited their ability to form tubes induced by conditioned media (CM) of activated RA synovial fibroblasts. When RA synovial fibroblasts were pretreated with rofecoxib for 16 h and then stimulated with interleukin (IL)-1beta, their CM induced significantly less HMVEC tube formation when compared with CM from vehicle-treated RA synovial fibroblasts. ELISAs performed on activated RA fibroblast CM for known proangiogenic factors demonstrated a significant reduction in bFGF, in addition to the expected decrease in PGE(2). Our studies suggest that COX-2-induced angiogenic activity is an active mechanism within diseased synovium and may provide an additional rationale for the use of COX-2 inhibitors in RA.  相似文献   
125.
The rate of release of five amino acids (alanine, glutamine, glutamic acid, glycine, GABA) from the surface of the sensorimotor cortex has been determined in rabbits under local anesthesia immobilized with gallamine. Concomitant recording of the electroencephalogram and of blood pressure has been carried out. The scope of the research was to determine if a difference in the release of these aminoacids could be correlated with variations in cerebral electrical activity. Two open-ended silver cylinders were adapted to the cortex and filled with saline. Every 10 min, the liquid was removed and assayed using a dansylating procedure followed by thin layer chromatographic separation and fluorimetric determination of the amino acids. The EEG of non treated animals, followed for a period of 100 min, remained synchronized for the majority of the recording; the biochemical determinations indicated a slight but constant fall in the rate of release of all the amino acids. A significant increase in the release accompanied the EEG desynchronisation induced either with eserine (0.2 mg/kg), amphetamine (2 mg/kg), or with electrical stimulation of the reticular formation.  相似文献   
126.
Erdmann L  Macedo B  Uhrich KE 《Biomaterials》2000,21(24):832-2512
Degradable poly(anhydride ester) implants in which the polymer backbone breaks down into salicylic acid (SA) were investigated. In this preliminary work, local release of SA from the poly(anhydride esters), thus classified as ‘active polymers', on healthy bone and tissue was evaluated in vivo using a mouse model. Degradable polyanhydrides that break down into inactive by-products were used as control membranes because of their chemical similarity to the active polymers. Small polymer squares were inserted over the exposed palatal bone adjacent to the maxillary first molars. Active polymer membranes were placed on one side of the mouth, control polymers placed on the contra lateral side. Intraoral clinical examination showed that active polymer sites were less swollen and inflamed than control polymer sites. Histopathological examination at day 1 showed essentially no difference between control and active polymers. After 4 days, active polymer sites showed epithelial proliferation to a greater extent than the polyanhydride controls. After 20 days, active polymer sites showed greater thickness of new palatal bone and no resorptive areas, while control polymer sites showed less bone thickness as well as resorption including lacunae involving cementum and dentine. From these preliminary studies, we conclude that active polymers, namely poly(anhydride esters), stimulated new bone formation.  相似文献   
127.
128.
Although a number of studies have implicated the hippocampal formation in social recognition memory in the rat, a recent study in this laboratory has demonstrated that selective cytotoxic lesions, confined to the hippocampus proper (encompassing the four CA subfields and the dentate gyrus), are without effect on this behaviour. This finding suggests that the hippocampus proper does not subserve social recognition memory in the rat, but does not preclude the possibility that other areas of the hippocampal formation, such as the entorhinal cortex or subiculum, could support this form of learning. The present study addressed this issue by examining the effects of selective cytotoxic retrohippocampal (RHR) lesions (including both the entorhinal cortex and subiculum) on social recognition memory in the rat. RHR lesions produced a mild social recognition memory impairment, although lesioned animals still displayed a reduction in investigation time between the first and second exposure to the juvenile. This result is consistent with other studies which have implicated the retrohippocampal or parahippocampal area in olfactory recognition memory processes. It also suggests, however, that other areas, out with the retrohippocampal region, are also likely to play an important role in social recognition memory.  相似文献   
129.
Intestinal inflammation in Crohn’s disease (CD) may be complicated by the occurrence of strictures and fistulae. The pathogenesis of fistula formation is unknown. We therefore wanted to determine whether mechanical factors might contribute to the development of fistulae. Furthermore, we tried to define the path of internal fistulae through the muscular layer. For this purpose, surgical resection specimens from 42 consecutive patients with CD were prospectively studied. In gross examination the whole bowel was cut into circumferential cross sections 0.3 cm thick. Abnormal areas were histologically examined. Strictures were found in 38 patients (90.5%), and fistulae were observed in 27 (64.3%) patients. In 11 (40.7%) specimens fistulae were found within a stricture, in 15 (55.6%) at the proximal end, and in 1 (3.7%) no stricture was found. In 7 (25.9%) cases with fistulae, herniated mucosa was found within the muscularis propria or the subserosa. In 7 (25.9%) cases a blood vessel was identified near a fistula traversing the muscularis propria. From these findings we conclude that that mechanical factors may contribute to fistula formation. This is further supported by the fact that fistulae appear to traverse the muscular layer along piercing vessels. Received: 21 January 2000 / Accepted: 7 March 2000  相似文献   
130.
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