全文获取类型
收费全文 | 6624篇 |
免费 | 296篇 |
国内免费 | 52篇 |
专业分类
耳鼻咽喉 | 116篇 |
儿科学 | 135篇 |
妇产科学 | 80篇 |
基础医学 | 942篇 |
口腔科学 | 117篇 |
临床医学 | 414篇 |
内科学 | 1752篇 |
皮肤病学 | 128篇 |
神经病学 | 568篇 |
特种医学 | 291篇 |
外科学 | 1016篇 |
综合类 | 17篇 |
预防医学 | 174篇 |
眼科学 | 179篇 |
药学 | 356篇 |
中国医学 | 31篇 |
肿瘤学 | 656篇 |
出版年
2023年 | 40篇 |
2022年 | 66篇 |
2021年 | 120篇 |
2020年 | 58篇 |
2019年 | 89篇 |
2018年 | 100篇 |
2017年 | 99篇 |
2016年 | 102篇 |
2015年 | 152篇 |
2014年 | 193篇 |
2013年 | 274篇 |
2012年 | 342篇 |
2011年 | 365篇 |
2010年 | 215篇 |
2009年 | 197篇 |
2008年 | 323篇 |
2007年 | 412篇 |
2006年 | 438篇 |
2005年 | 390篇 |
2004年 | 431篇 |
2003年 | 407篇 |
2002年 | 446篇 |
2001年 | 95篇 |
2000年 | 79篇 |
1999年 | 128篇 |
1998年 | 98篇 |
1997年 | 98篇 |
1996年 | 88篇 |
1995年 | 84篇 |
1994年 | 80篇 |
1993年 | 81篇 |
1992年 | 92篇 |
1991年 | 87篇 |
1990年 | 66篇 |
1989年 | 49篇 |
1988年 | 49篇 |
1987年 | 49篇 |
1986年 | 52篇 |
1985年 | 39篇 |
1984年 | 35篇 |
1983年 | 29篇 |
1982年 | 31篇 |
1981年 | 38篇 |
1980年 | 24篇 |
1979年 | 20篇 |
1978年 | 22篇 |
1977年 | 24篇 |
1976年 | 23篇 |
1975年 | 26篇 |
1970年 | 20篇 |
排序方式: 共有6972条查询结果,搜索用时 31 毫秒
51.
Tetsuo Takaishi Takashi Ono Yoshifumi Yasuda 《European journal of applied physiology》1992,65(4):335-339
Summary The surface electromyogram (EMG) from active muscle and oxygen uptake (
) were studied simultaneously to examine changes of motor unit (MU) activity during exercise tests with different ramp increments. Six male subjects performed four exhausting cycle exercises with different ramp slopes of 10, 20, 30 and 40 W · min–1 on different days. The EMG signals taken from the vastus lateralis muscle were stored on a digital data recorder and converted to obtain the integrated EMG (iEMG). The
was measured, with 20-s intervals, by the mixing chamber method. A non-linear increase in iEMG against work load was observed for each exercise in all subjects. The break point of the linear relationship of iEMG was determined by the crossing point of the two regression lines (iEMGbp). Significant differences were obtained in the exercise intensities corresponding to maximal oxygen uptake (
) and the iEMGbp between 10 and 30, and 10 and 40 W · min –1 ramp exercises (P < 0.05). However, no significant differences were obtained in
and
corresponding to the iEMGbp during the four ramp exercises. With respect to the relationship between
and exercise intensity during the ramp increments, the
-exercise intensity slope showed significant differences only for the upper half (i.e. above iEMGbp). These results demonstrated that the
and
at which a nonlinear increase in iEMG was observed were not varied by the change of ramp slopes but by the exercise intensity corresponding to
and the iEMGbp was varied by the change of ramp slopes. In addition, the significant differences in the
exercise intensity slopes for the upper half of the tests would suggest that the recruitment patterns of MU and/or muscle metabolic state might be considerably altered depending upon the ramp slope increments. 相似文献
52.
Tetsuo Kodaka Ryoichi Mori Akihiko Hirayama Tsuneyoshi Sano 《Medical Electron Microscopy》2003,36(4):272-281
We investigated the fine structure and mineral components of 29 stonelike masses obtained from the mesenteries of four adult cadavers, using optical microscopy, backscattered electron imaging, scanning electron microscopy, energy-dispersive X-ray microanalysis, and X-ray diffraction. Although the overall appearance of the stonelike masses measuring about 5–20mm in diameter and 0.06–3.1g in dry weight was roughly grouped into smooth bulb- and uneven bulk-shaped types, all the calcified masses basically consisted of core and mantle regions. The smooth bulb-shaped masses had a broad mantle with many concentric rings, whereas the uneven bulk-shaped masses contained a large core. In their core regions, spherulitic and short bundle-shaped deposits composed of needle-shaped apatite crystals were mainly found among loose collagen fibers. Their mantle regions, on the other hand, showed the concentric structures of dense collagen fibers in the intra- and/or extrafibrous calcification with fine sandy grain-shaped deposits. The mineral elements were mainly Ca and P, and the major crystals were hydroxyapatite. Hexahedral whitlockite containing Mg was a minor component. The fiber-rich mantle regions showed lower calcification and lesser crystallization than the fiber-poor core region. When necrotic or some tumor adipose tissues and necrotic lymphoid tissues that might have been caused by some digestive diseases are recognized as foreign matter, their tissues occasionally will be calcified and grow into stonelike masses. These stonelike masses tend to occur more often in women than in men. 相似文献
53.
54.
Quantitative Analysis of Mycobacterial and Propionibacterial DNA in Lymph Nodes of Japanese and European Patients with Sarcoidosis 总被引:10,自引:0,他引:10
下载免费PDF全文
![点击此处可从《Journal of clinical microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yoshinobu Eishi Moritaka Suga Ikuo Ishige Daisuke Kobayashi Tetsuo Yamada Tamiko Takemura Touichiro Takizawa Morio Koike Shoji Kudoh Ulrich Costabel Josune Guzman Gianfranco Rizzato Marcello Gambacorta Ronald du Bois Andrew G. Nicholson Om P. Sharma Masayuki Ando 《Journal of clinical microbiology》2002,40(1):198-204
The cause(s) of sarcoidosis is unknown. Mycobacterium spp. are suspected in Europe and Propionibacterium spp. are suspected in Japan. The present international collaboration evaluated the possible etiological links between sarcoidosis and the suspected bacterial species. Formalin-fixed and paraffin-embedded sections of biopsy samples of lymph nodes, one from each of 108 patients with sarcoidosis and 65 patients with tuberculosis, together with 86 control samples, were collected from two institutes in Japan and three institutes in Italy, Germany, and England. Genomes of Propionibacterium acnes, Propionibacterium granulosum, Mycobacterium tuberculosis, Mycobacterium avium subsp. paratuberculosis, and Escherichia coli (as the control) were counted by quantitative real-time PCR. Either P. acnes or P. granulosum was found in all but two of the sarcoid samples. M. avium subsp. paratuberculosis was found in no sarcoid sample. M. tuberculosis was found in 0 to 9% of the sarcoid samples but in 65 to 100% of the tuberculosis samples. In sarcoid lymph nodes, the total numbers of genomes of P. acnes or P. granulosum were far more than those of M. tuberculosis. P. acnes or P. granulosum was found in 0 to 60% of the tuberculosis and control samples, but the total numbers of genomes of P. acnes or P. granulosum in such samples were less than those in sarcoid samples. Propionibacterium spp. are more likely than Mycobacteria spp. to be involved in the etiology of sarcoidosis, not only in Japanese but also in European patients with sarcoidosis. 相似文献
55.
Yasuo Kawakami Kimitaka Nakazawa Toshiro Fujimoto Daichi Nozaki Mitsumasa Miyashita Tetsuo Fukunaga 《European journal of applied physiology》1994,68(2):139-147
Series cross-section images of the upper extremity were obtained for four men by magnetic resonance imaging (MRI) and anatomical cross-sectional areas (ACSA) of elbow flexor muscles [biceps brachii (BIC), brachialis (BRA), brachioradialis (BRD)] and extensor muscles [triceps brachii (TRI)] were measured. Physiological cross-sectional area (PCSA) was calculated from the muscle volume and muscle fibre length, the former from the series ACSA and the latter from the muscle length multiplied by previously reported fibre/muscle length ratios. Elbow flexion/extension torque was measured using an isokinetic dynamometer and the force at the tendons was calculated from the torque and moment arms of muscles measured by MRI. Maximal ACSA of TRI was comparable to that of total flexors, while PCSA of TRI was greater by 1.9 times. Within flexors, BRA had the greatest contribution to torque (47%), followed by BIC (34%) and BRD (19%). Specific tension related to the estimated velocity of muscle fibres were similar for elbow flexors and extensors, suggesting that the capacity of tension development is analogous between two muscle groups. 相似文献
56.
A floating cell line (HGC-25) was established from the metastatic ascitic fluid of a human pancreatic adenocarcinoma of ductal cell origin. The cell line was characterized by the growth in suspension with a doubling time of 15.6 hr, a high cloning efficiency in soft agar and a modal chromosome number of 72. Electron microscopic examination revealed terminal bars in a small number of cells. Production of mucin and immunoglobulins and phagocytosis were not demonstrated. Heterotransplantation of the cells produced tumors, being undifferentiated carcinoma histologically. These characteristics mentioned above confirm that HGC-25 cell line is a human pancreatic cancer ceU line. 相似文献
57.
Naoya Nakamura Naoyoshi Mori Koichi Ohshima Tetsuo Kuze Yuko Hashimoto Yoshikazu Sasaki Asumi Shirakawa Michiko Sato Masafumi Abe 《Diagnostic molecular pathology》2002,11(2):83-89
We examined nucleotide sequences of Epstein-Barr virus (EBV)-positive Hodgkin/Reed-Sternberg (HRS)-like B cells in a case of diffuse large B-cell lymphoma (DLBCL) and a case of adult T-cell lymphoma (ATL) for single-cell polymerase chain reaction of the immunoglobulin heavy-chain gene variable region (VH gene). HRS-like B cells were scattered in the area irrelevant to the lymphoma infiltrates of DLBCL and in the lymphoma area of ATL. HRS-like B cells were positive for CD20 and CD30 but negative for CD15. EBV presented in HRS-like B cells in both cases but not in any lymphoma cells. VH genes of five HRS-like B cells analyzed in DLBCL were polyclonal and showed in-frame sequences with 0% to 2.8% somatic mutation frequency. In an ATL, VH genes of five HRS-like B cells analyzed were polyclonal and somatically mutated. Four cells carried in-frame rearrangements with 3.5% to 17.7% mutation frequency. One of the VH genes has a one-codon deletion. From the fifth cell, an out-of-frame rearrangement with an insertion and a deletion was obtained. Thus, we showed polyclonal EBV-positive HRS-like B cells in both DLBCL and ATL and that whereas EBV-positive, HRS-like B cells in DLBCL exhibited unmutated and mutated VH gene, those in ATL were found to have a somatically mutated VH gene with/without deletions and/or insertions. The HRS-like B cells may appear because of active EBV infection in a patient who is immunosuppressed from the primary lymphoma. 相似文献
58.
Hiroshi Kunikane Hiroshi Ishikura Jun Yamaguchi Takashi Yoshiki Tetsuo Itoh Miki Aizawa 《Pathology international》1987,37(4):615-625
The clinicopathology of 13 cases of chondroid syringoma were examined. The ages of the patients ranged from 26 to 86 years, with an average of 48 years. There were eight males and five females. Ten tumors out of the thirteen appeared on the face. Only one patient out of ten was suspected of recurrence in follow-up information. Histologically, all tumors consisted of epithelial cells, chondroid or myxoid matrix, and other strumal elements. The tumors were histologically classified into two types; twelve tumors had tubular and cystic lumina lined by two layers of epithelial cells, and only one case had small lumina lined by only a single layer. By an immunohistochemical study with a PAP method, positive stainings of keratin were observed in all cases, and S-100 protein in all but one. Ultrastructurally, the tumor cells showed features of an epithelial cell. Some ultrastructural differences were noted between two types of chondroid syringoma. Type I tumor cells had many tonofilaments in cytoplasm, but cytoplasmic filaments in type II were of the intermediate-type. 相似文献
59.
Sharma R Bhatti S Gomez M Clark RM Murray C Ashizawa T Bidichandani SI 《Human molecular genetics》2002,11(18):2175-2187
Friedreich ataxia is commonly caused by large expansions of a GAA triplet-repeat (GAA-TR) sequence in the first intron of the FRDA gene. We used small-pool PCR to analyze somatic variability among 7190 individual FRDA molecules from peripheral blood DNA of subjects carrying 12 different expanded alleles, ranging in size from 241 to 1105 triplets. Expanded alleles showed a length-dependent increase in somatic variability, with mutation loads ranging from 47% to 78%. We noted a strong contraction bias among long alleles (>500 triplets), which showed a 4-fold higher frequency of large contractions versus expansions. Some contractions were very large; of all somatic mutations scored, approximately 5% involved contractions of >50% of the original allele length, and 0.29% involved complete reversion to the normal/premutation length (< or =60 triplets). These observations contrast sharply with the strong expansion bias seen in expanded CTG triplet repeats in myotonic dystrophy. No somatic variability was detected in >6000 individual FRDA molecules analyzed from 15 normal alleles (8-25 triplets). A premutation allele with 44 uninterrupted GAA repeats was found to be unstable, ranging in size from 6 to 113 triplets, thus establishing the threshold for somatic instability between 26 and 44 GAA triplets. Analysis of an additional 7850 FRDA molecules from serially passaged lymphoblastoid cell lines carrying nine expanded alleles (132-933 triplets) showed very low mutation loads, ranging from 0% to 6.2%. Our data indicate that expanded GAA-TR alleles in Friedreich ataxia are highly mutable and have a natural tendency to contract in vivo, and that these properties depend on multiple factors, including DNA sequence, triplet-repeat length and unknown cell-type-specific factors. 相似文献