全文获取类型
收费全文 | 1015400篇 |
免费 | 71878篇 |
国内免费 | 1698篇 |
专业分类
耳鼻咽喉 | 14556篇 |
儿科学 | 26957篇 |
妇产科学 | 25279篇 |
基础医学 | 143848篇 |
口腔科学 | 31855篇 |
临床医学 | 86417篇 |
内科学 | 203616篇 |
皮肤病学 | 21875篇 |
神经病学 | 78913篇 |
特种医学 | 38589篇 |
外国民族医学 | 80篇 |
外科学 | 162204篇 |
综合类 | 18583篇 |
现状与发展 | 1篇 |
一般理论 | 263篇 |
预防医学 | 70697篇 |
眼科学 | 22833篇 |
药学 | 78533篇 |
3篇 | |
中国医学 | 2705篇 |
肿瘤学 | 61169篇 |
出版年
2021年 | 8573篇 |
2019年 | 8594篇 |
2018年 | 12277篇 |
2017年 | 9010篇 |
2016年 | 9713篇 |
2015年 | 11097篇 |
2014年 | 15148篇 |
2013年 | 21816篇 |
2012年 | 30476篇 |
2011年 | 31895篇 |
2010年 | 18477篇 |
2009年 | 17261篇 |
2008年 | 29578篇 |
2007年 | 30870篇 |
2006年 | 31220篇 |
2005年 | 30136篇 |
2004年 | 28781篇 |
2003年 | 27525篇 |
2002年 | 26699篇 |
2001年 | 56483篇 |
2000年 | 58459篇 |
1999年 | 48519篇 |
1998年 | 11234篇 |
1997年 | 9883篇 |
1996年 | 9908篇 |
1995年 | 9225篇 |
1994年 | 8524篇 |
1993年 | 7787篇 |
1992年 | 36150篇 |
1991年 | 34432篇 |
1990年 | 33215篇 |
1989年 | 32256篇 |
1988年 | 29359篇 |
1987年 | 28586篇 |
1986年 | 26591篇 |
1985年 | 25418篇 |
1984年 | 18018篇 |
1983年 | 15322篇 |
1982年 | 7923篇 |
1979年 | 15938篇 |
1978年 | 10720篇 |
1977年 | 9120篇 |
1976年 | 7948篇 |
1975年 | 8713篇 |
1974年 | 10616篇 |
1973年 | 9959篇 |
1972年 | 9447篇 |
1971年 | 8969篇 |
1970年 | 8526篇 |
1969年 | 8035篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
881.
882.
883.
C M Mond D B Walters R S Stricoff E M Prescott A T Prokopetz 《American Industrial Hygiene Association journal》1987,48(10):823-829
A human factors engineering analysis of a chemical containment laboratory was performed to develop appropriate standards for future laboratory design. In order to perform this evaluation, a state-of-the-art facility was studied in depth. Measurements and observations were made of key operating areas. In addition, technicians were observed and interviewed as they performed various tasks. Compiled data were compared to existing ergonomic standards. The occupational implications of instituting ergonomically developed laboratory design standards are as follows: increased worker health, safety and productivity, improved work quality and reduced stress. 相似文献
884.
Multidisciplinary evaluation of rat renal cell carcinoma 总被引:1,自引:0,他引:1
H F Karthaus W F Feitz A P vd Meijden J A Schalken J L Beck B T Hendriks P H Jap G P Vooijs F M Debruyne F C Ramaekers 《In vivo (Athens, Greece)》1987,1(6):335-341
The rat renal cell carcinoma system as described by deVere White and Olsson in 1980 is used widely as a model for its human counterpart. The tumor arose spontaneously in a male Wistar Lewis rat and its behaviour has been shown to be stable during multiple passages. We have compared this tumor with the human renal cell carcinoma using a multidisciplinary approach. Light microscopy and electron microscopy showed a great resemblance of this rat tumor to a human renal cell carcinoma of the clear cell type with the ultrastructural presence of desmosomes. With the use of tissue specific antibodies against intermediate filament proteins, it could be shown that their expression is comparable to human renal cell carcinoma, i.e. coexpression of vimentin and different cytokeratins in the tumor cells. The cells could also be shown to contain cytokeratin 18. An aneuploid cell population in the tumor, expressing both vimentin and keratin, could be characterized by DNA flow cytometry in double labeling experiments. Comparison of normal and malignant rat kidney tissue by Northern blot analysis revealed increased levels of vimentin mRNA. In conclusion, this tumor model seems to have several histological and biological properties in common with the human renal tumor. 相似文献
885.
The ganglioside composition of human melanoma was analyzed in five sets of tumor specimens obtained directly from surgery, from the autologous tissue culture cell lines, and from the autologous cell lines grown in athymic nude mice. Total gangliosides of these 15 melanoma specimens were isolated and purified, and the amount of each component ganglioside was analyzed by thin-layer chromatography and a thin-layer chromatography scanner. The ganglioside composition of the five surgical melanoma specimens clearly exhibited different patterns from each other. Moreover, none of the autologous cultured melanomas possessed the same ganglioside composition as their original biopsied tumors. However, when these melanoma cell lines were transplanted into nude mice, the ganglioside composition was converted back to the same ganglioside pattern as in the original surgical specimens. The results support the view that changes in the ganglioside composition of melanoma during in vitro growth are caused by the culture environment rather than by selection of melanoma cells with a particular genotype. Reestablishment of the original ganglioside patterns after passage in nude mice provides clear evidence that in vivo expression of gangliosides is a conserved and stable function specified by the human melanoma cells. 相似文献
886.
The intensity and degree of heterogeneous epithelial marker expression were evaluated immunohistochemically in 29 mucosal biopsy specimens from 7 ulcerative colitis (UC) patients with dysplasia. Biopsy specimens from UC patients with mild (n = 7) or severe (n = 6) inflammation and from histologically normal samples (n = 7) served as controls. HLA-DR showed heterogeneous epithelial expression in all lesions with high grade dysplasia and in 6 of 8 with low grade dysplasia. SC was heterogeneous stained in 17 of 21 lesions with high grade dysplasia and in all but two lesions with low grade dysplasia. In histologically normal mucosa, SC was homogeneously expressed and epithelial DR was virtually absent. In mildly inflamed UC lesions, SC exhibited patchy distribution in only one sample and DR in two, whereas both SC and DR showed a slight degree of heterogeneous expression in all lesions with severe inflammation. Moreover, the overall intensity of SC staining tended to decrease with increasing degree of inflammation, whereas the opposite was seen for DR. Decreased SC and increased DR expression thus seemed to be related to intensified inflammatory activity, whereas heterogeneous expression of these markers was significantly more related to dysplasia. 相似文献
887.
A 43-year-old alcoholic presented in coma with ketoacidosis, after three days of nausea and feeling generally unwell, which had been preceded by a prolonged three-week period of heavy alcohol consumption with poor dietary intake. The acidosis responded rapidly to intravenous dextrose. This is the first Scottish report of a case of alcoholic ketoacidosis. 相似文献
888.
An experimental model has been developed for the study of combined effects of partial body irradiation (PBI) and graft-versus-host disease (GVHD) in which irradiation is delivered to the thorax 24 hr prior to induction of GVHD in hybrid mice by the injection of parental lymphoid cells. In mice irradiated to 1000 cGy or exposed to low doses of allogeneic lymphoid cells (20 X 10(6)), survival was 100% at 250 days. In contrast, combination of the two treatments, GVHD and PBI, resulted in a mortality of 83% and a mean survival time of 29 days, indicating synergy between GVHD and PBI. From histological studies of the lung it appeared that about 40% of the deaths occurring after combined GVHD/PBR treatment might be attributable to pneumonia. The cause of death in the remaining mice receiving combined treatment is not known. Mice receiving combined PBI/lymphoid cell treatment develop a characteristic skin lesion that is not seen in nonirradiated mice and is confined to the irradiated area. The effect of preinduction PBR on the timing and severity of GVHD is similar to that which would be produced by an increase in the number of effector cells. 相似文献
889.
L C Harlan B F Polk S Cooper T P Blaszkowski J Ignatius-Smith M Stromer H Mull 《American journal of preventive medicine》1986,2(5):256-261
The effects of labeling a person as hypertensive have important implications for hypertension screening. The Hypertension Detection and Follow-up Program (HDFP) provides an opportunity to examine the effects of labeling, treatment, and study assignment on a large group of hypertensives (n = 10,070). Their answers to questions regarding perceived health and general well-being asked at baseline and again one year later were analyzed. There was no significant change in the perceived health status of persons who were unaware of their hypertension at baseline and remained untreated at one year (labeling alone). The effect of labeling plus treatment was associated with a significant decrease in perceived health. The effect of antihypertensive drug therapy on perceived health status was examined in persons who were aware of their hypertension but not on treatment at baseline, and on treatment at one year. The stepped care group (SC) had a significant improvement in their perceived health and a significant decrease in the amount of time spent worrying about their health. The referred care group (RC) had no change. Program assignment effects were studied in individuals aware of their hypertension and on treatment both at baseline and one year later. Both the SC and RC groups had a significant improvement in their perceptions of their health status. The SC group had a significant decrease in time spent worrying about their health, while the RC group showed no change. These reassuring results fail to support the suggestion that labeling persons as hypertensive is necessarily followed by negative psychological consequences.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
890.
We experienced one necropsy case of brainstem encephalitis of Iizuka type (BSE) and one necropsy case of the brain-stem syndrome (BSS) of typical neuro-Beh?et's disease, and compared them clinically and neuropathologically. Clinically both of these cases showed chronic progressive mental disturbance, pseudobulbar paresis, spastic tetraparesis, cerebrospinal fluid pleocytosis, increased protein, and brainstem atrophy observed by X-CT. Neuropathologically, irregular, boundary-indistinct demyelinating lesions and obsolete softening lesions were sporadically found, associated with perivascular lymphocytic infiltration and gliosis centering on the brainstem. In this way, both cases were similar in many points except for the presence or absence of cutaneo-muco-ocular signs specific for Beh?et's disease. Also BSE and BSS reports in the literature showed that both diseases were similar not only in clinical findings consisting of mental disturbance and brainstem signs but also in neuropathological findings with similar topographical distribution of the same histopathological changes, including the variations and diversity of these characteristics. Especially of much interest is their similarity in characteristic mental disturbance. In discriminating BSE from multiple sclerosis and other diseases with exclusive involvement of the brainstem, it is important to understand their clinical characteristics. The characteristic mental disturbance includes damage to memory and sentiment, a change in personality, and lowering in spontaneity, but calculation ability and orientation are comparatively preserved. Of course the similarity in clinical and neuropathological findings does not necessarily mean the identical etiopathogenesis. However, it is possible to consider that neuro-Beh?et's disease (syndrome) may form a wide spectrum with BSE and typical neuro-Beh?et's disease at the both ends, regarding the time and spatial diversity of the appearance of cutaneo-muco-ocular signs. 相似文献