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   5981篇
  免费   372篇
  国内免费   82篇
耳鼻咽喉   45篇
儿科学   301篇
妇产科学   155篇
基础医学   799篇
口腔科学   173篇
临床医学   607篇
内科学   1148篇
皮肤病学   310篇
神经病学   510篇
特种医学   564篇
外国民族医学   3篇
外科学   667篇
综合类   69篇
一般理论   3篇
预防医学   357篇
眼科学   119篇
药学   326篇
  2篇
中国医学   1篇
肿瘤学   276篇
  2022年   37篇
  2021年   71篇
  2020年   47篇
  2019年   49篇
  2018年   83篇
  2017年   87篇
  2016年   94篇
  2015年   136篇
  2014年   134篇
  2013年   166篇
  2012年   203篇
  2011年   222篇
  2010年   180篇
  2009年   180篇
  2008年   179篇
  2007年   243篇
  2006年   183篇
  2005年   209篇
  2004年   146篇
  2003年   149篇
  2002年   171篇
  2001年   182篇
  2000年   154篇
  1999年   137篇
  1998年   174篇
  1997年   202篇
  1996年   168篇
  1995年   150篇
  1994年   150篇
  1993年   120篇
  1992年   86篇
  1991年   105篇
  1990年   111篇
  1989年   124篇
  1988年   116篇
  1987年   119篇
  1986年   125篇
  1985年   109篇
  1984年   79篇
  1983年   55篇
  1982年   48篇
  1981年   49篇
  1980年   48篇
  1979年   45篇
  1977年   47篇
  1976年   43篇
  1975年   46篇
  1972年   39篇
  1971年   28篇
  1970年   31篇
排序方式: 共有6435条查询结果,搜索用时 15 毫秒
41.
Donor inseminations (DI) have been performed for decades. Most of the publications on this topic deal only with problems of tolerance and acceptance of this treatment for sterility. We already reported on them in parts I and II. In the present third and last part, we discuss the indications for DI: male infertility, genetic disorders, and unsuccessful assisted reproduction therapy. Which conditions do affect the success of therapy? Which methods are recommended? Our treatment results verify realistically that in effect DI only produces the desired child in about 50 % of the couples. As a complementary therapy, in vitro fertilization (IVF) with donor spermatozoa offers a real chance for pregnancy even for women whose husbands are infertile and who themselves suffer from impaired fertility such as pathological conditions of the fallopian tube or when simple inseminations have not resulted in pregnancy. After receiving consent from the State Physicians’ Chamber, we treated 19 women by donor IVF in our group practice and fulfilled their desire to bear their own child.  相似文献   
42.
Experimental infection of specific-pathogen-free pigs with swine influenza virus by the intratracheal route resulted in a severe respiratory disease that closely resembled natural swine influenza in clinical course and pathologic lesions. Alveolar epithelial necrosis with sloughing of necrotic cells occurred from 24 to 96 hours after inoculation (p.i.) and was associated with alveolar edema and diffuse interstitial pneumonitis. The latter, initially of neutrophilic character, became histiocytic 48 hours p.i. Ultrastructural analysis of alveolar parenchyma disclosed viral replication in epithelial cells beginning at 5 hours p.i. and lasting to 96 hours. Budding of pleomorphic virus particles from the surface of alveolar epithelial cells and accumulation of viral proteins within the nucleus and cytoplasm of epithelial cells were seen. The extent of parenchymal lesions as quantified by stereologic morphometry within the whole lung was characterized by a marked relative and absolute volume increase of interalveolar septa and increased air-blood tissue barrier thickness. The volume increase of interalveolar septa was due to an increase of interstitial tissue volume by 85% in pigs at 96 hours p.i., compared with control pigs with similar lung volumes.  相似文献   
43.
A previous study has suggested that Fusobacterium nucleatum FN-2 contains a galactose-binding protein (lectin) on the cell surface (P. A. Murray, V. Matarese, C. I. Hoover, and J. R. Winkler, FEMS Microbiol. Lett. 40:123-127, 1987). In the present study, the molecular specificity and size of this lectin were investigated by several techniques. Whole-cell affinity chromatography with asialofetuin covalently coupled to Sepharose 6MB demonstrated that 81% of 3H-labeled F. nucleatum were specifically eluted by 0.5 M galactose. Specific binding was calcium dependent and did not occur in the presence of calcium chelators. Binding was inhibited by preincubation with galactose. Agglutination of human parotid saliva by F. nucleatum was also inhibited by galactose and its structural analogs. Inhibition by lactose was 2 times that of galactose, inhibition by p-aminophenyl galactosides was 4 times that of galactose, and inhibition by asialoglycopeptides was 100 times that of galactose. Similar inhibition results were obtained for hemagglutination of neuraminidase-treated erythrocytes. These findings suggest that the binding specificity of F. nucleatum FN-2 is more complex than simply the recognition of the monosaccharide galactose. This is consistent with the concept that lectins considered identical in terms of monosaccharide specificity can recognize fine differences in more complex structures. To identify the specific bacterial component(s) involved in galactose recognition, proteins of F. nucleatum FN-2 were separated on a 4 to 11% gradient sodium dodecyl sulfate slab gel, transferred to nitrocellulose paper to renature bacterial binding sites, and then incubated with 125I-labeled asialofetuin. Autoradiographs of the nitrocellulose revealed a band at a range of Mr 300,000 to 330,000 which was not present when the blots were preincubated with galactose. These data support the concept that F. nucleatum FN-2 possesses a lectin that recognizes galactose and galactose-containing substrates.  相似文献   
44.
Nephrotic syndrome, characterized by edema, proteinuria, hyperlipidemia and low serum albumin, is a manifestation of kidney disease involving the glomeruli. Nephrotic syndrome may be caused by primary kidney disease such as focal segmental glomerulosclerosis. Mutations in the podocin gene, NPHS2, have been shown in familial and sporadic forms of steroid-resistant nephrotic syndrome, including focal segmental glomerulosclerosis. Podocin is an integral membrane protein located at the slit diaphragm of the glomerular permeability barrier. Complete information is lacking for the population frequency of some NPHS2 variants for all racial and ethnic groups. The most frequently reported variant, R229Q, is more common among European-derived populations than African-derived populations. We calculated crude odds ratios and 95% confidence intervals of childhood nephrotic syndrome and focal segmental glomerulosclerosis associated with R229Q heterozygosity using data from five studies. The R229Q variant is not associated with focal segmental glomerulosclerosis in the US population of African descent. In contrast, the R229Q variant is associated with a trend toward increased focal segmental glomerulosclerosis risk in European-derived populations, with an estimated increased risk of 20-40%. Our insight into the association between NPHS2 variants and nephrotic disease is hampered by the limitations of the existing studies, including small numbers of affected individuals and suboptimal control groups. Nevertheless, the available data suggest that large epidemiological case-control studies to examine the association between NPHS2 variants and nephrotic syndrome are warranted.  相似文献   
45.
Tay-Sachs and Sandhoff diseases are autosomal recessive neurodegenerative diseases resulting from the inability to catabolize GM2 ganglioside by beta-hexosaminidase A (Hex A) due to mutations of the alpha subunit (Tay-Sachs disease) or beta subunit (Sandhoff disease) of Hex A. Hex B (beta beta homodimer) is also defective in Sandhoff disease. We previously developed mouse models of both diseases and showed that Hexa-/- (Tay-Sachs) mice remain asymptomatic to at least 1 year of age while Hexb-/- (Sandhoff) mice succumb to a profound neurodegenerative disease by 4-6 months of age. Here we find that neuron death in Hexb-/- mice is associated with apoptosis occurring throughout the CNS, while Hexa-/- mice were minimally involved at the same age. Studies of autopsy samples of brain and spinal cord from human Tay-Sachs and Sandhoff diseases revealed apoptosis in both instances, in keeping with the severe expression of both diseases. We suggest that neuron death is caused by unscheduled apoptosis, implicating accumulated GM2 ganglioside or a derivative in triggering of the apoptotic cascade.   相似文献   
46.
Lymphokine-mediated inhibition of Rickettsia prowazekii multiplication in L929 fibroblasts was eliminated by treatment of the lymphokine with a monoclonal antibody specific for interferon-gamma. Soluble monoclonal antibody and antibody conjugated to Sepharose beads were equally effective. Macrophage activation to limit the multiplication of Rickettsia conorii was eliminated with antibody-conjugated beads; however, neutralization of the ability to activate macrophages with soluble antibody was not complete and required more antibody than did neutralization of antiviral activity.  相似文献   
47.
We investigated whether the mismatch process between a rare stimulus and the trace of frequent stimulus, which generates the mismatch-negativity component of the event-related potential, can tolerate a small variation in the intensity of the frequent stimulus. Series of short tone pips were presented to 10 subjects while they were reading a book and ignoring the auditory stimuli. The intensity (mean 80dB) of the frequent stimulus (600 Hz) varied within a range that was different in different blocks. The probability of the infrequent stimuli which were, in different blocks, either intensity deviants (600 Hz/70dB) or frequency deviants (650 Hz/80dB) was 10%. Both deviant stimuli elicited mismatch negativity even when the intensity of the frequent stimulus varied, although the amplitude of this component decreased with the increasing variability of the frequent stimulus. These results show that the generator process of mismatch negativity tolerates some variation in the repetitive stimulus, thus indicating that this process is also activated in ecologically more valid conditions. This is crucial to the interpretation of the generator process of mismatch negativity as a biologically vital warning mechanism.  相似文献   
48.
Disseminated infection with the coelomycetous fungus Nattrassia mangiferae is a very rare disease affecting only the immunocompromised host. We report the first case of a disseminated infection with spondylodiscitis and granular skin lesions due to N. mangiferae in a renal transplant patient.  相似文献   
49.
50.
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