全文获取类型
收费全文 | 8845篇 |
免费 | 499篇 |
国内免费 | 6篇 |
专业分类
9350篇 |
出版年
2023年 | 79篇 |
2022年 | 124篇 |
2021年 | 256篇 |
2020年 | 155篇 |
2019年 | 170篇 |
2018年 | 237篇 |
2017年 | 220篇 |
2016年 | 279篇 |
2015年 | 355篇 |
2014年 | 413篇 |
2013年 | 575篇 |
2012年 | 598篇 |
2011年 | 575篇 |
2010年 | 351篇 |
2009年 | 279篇 |
2008年 | 407篇 |
2007年 | 357篇 |
2006年 | 344篇 |
2005年 | 343篇 |
2004年 | 282篇 |
2003年 | 236篇 |
2002年 | 239篇 |
2001年 | 203篇 |
2000年 | 180篇 |
1999年 | 165篇 |
1998年 | 61篇 |
1997年 | 58篇 |
1996年 | 65篇 |
1995年 | 53篇 |
1994年 | 59篇 |
1993年 | 38篇 |
1992年 | 118篇 |
1991年 | 117篇 |
1990年 | 88篇 |
1989年 | 98篇 |
1988年 | 89篇 |
1987年 | 90篇 |
1986年 | 87篇 |
1985年 | 94篇 |
1984年 | 82篇 |
1983年 | 52篇 |
1982年 | 48篇 |
1981年 | 43篇 |
1980年 | 48篇 |
1979年 | 78篇 |
1978年 | 58篇 |
1977年 | 49篇 |
1976年 | 42篇 |
1974年 | 39篇 |
1973年 | 44篇 |
排序方式: 共有9350条查询结果,搜索用时 15 毫秒
71.
In vitro cultures of peripheral blood lymphocytes from human and muntjac (barking deer) females who were at an advanced stage of pregnancy (32-37 weeks pregnant women and 20-24 weeks pregnant muntjacs) showed an enhanced frequency of SCEs and X-ray-induced chromosome aberrations when compared with those of nonpregnant females. Lymphocyte cultures of nonpregnant females to which sex hormones progesterone, oestrogen and human chorionic gonadotropin (HCG) were added together exogenously also showed higher frequency of SCEs. The plausible reason(s) for such high incidence of SCEs during pregnancy is discussed. 相似文献
72.
73.
Subhash C. Sharma M.D. 《International journal of biometeorology》1986,30(1):27-32
Platelet counts were estimated at sea level in 50 lowlanders. They were divided at random in two groups (A and B) of 25 each. Group A went up by train/road transport to 3658 m, while group B reached the same height after 8 days of acclimatisation enroute. Platelet counts were estimated serially in both groups at high altitude. Symptoms of high altitude exposure were also recorded. No significant change in the counts was noted in either group and none became Symptomatic. All were brought back to sea level by air and deinduction studies carried out on days 1 and 4 of return. The importance of these findings in the light of our existing knowledge is discussed. 相似文献
74.
Anaerobic digesters contain a wide variety of anaerobic cellulolytic bacteria. Many of these are sporing rods. Some isolates from a mesophilic cattle waste anaerobic digester were classified as Sporolactobacillus spp. A further group of bacteria could not be induced to sporulate. In some respects they resembled Eubacterium , but considering all the properties it is suggested that they should be classified as a species of Clostridium. 相似文献
75.
76.
77.
The deoxyhexanucleotide d(TACGTA) was synthesized by a modified phosphotriester method. The modified procedure made rapid synthesis of deoxyoligonucleotide possible in gram quantity. N-Acetoxy-2-acetylaminofluorene (AAAF) modified d(TACGTA). Thin layer chromatography and UV analysis of the acid treated AAF modified hexanucleotide showed that the covalent modification with AAF took place exclusively at C(8) of guanine in d(TACGTA). d(TACGTA) and AAF modified d(TACGTA) were purified by preparative high performance liquid chromatography (HPLC). The pure products were characterized by 1H and 31P-NMR. The circular dichroism (CD) spectrum of d(TACGTA) was consistent with DNA in the B form even in the presence of 4 M NaCl whereas the modified hexamer had nearly inverted spectrum in the absence of any added salt. Both NMR and CD analyses indicated profound alteration of conformation of d(TACGTA) upon covalent modification with AAF. The stabilization of the Z-like conformation in the modified hexamer under physiological conditions of salt and temperature suggests biological relevance. 相似文献
78.
Cytophotometric estimation of DNA values from human buccal mucosa and lymphocyte culture nuclei shows a difference related to different X chromosomal abnormalities, namely, del X, XO, XXX and XXY. The values in the buccal mucosa in all cases except XXX were similar to the normal XX and XY. In lymphocytes nuclei, however, a steady increase in the DNA content at a significant level could be related to an increase in the number of X chromosomes. The similarity in the DNA values of normal XX and XY controls may be attributed to asynchrony in the replication patterns of X and Y chromosomes. 相似文献
79.
Possible implications of reciprocity between ethylene and aflatoxin biogenesis in Aspergillus flavus and Aspergillus parasiticus. 总被引:2,自引:1,他引:1
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Aspergillus flavus and Aspergillus parasiticus produced ethylene during early growth. However, the onset of toxin biosynthesis was marked by the absence of ethylene evolution. 2-Chloroethyl phosphonic acid, an ethylene-generating compound, inhibited aflatoxin biosynthesis in vivo. The reciprocal relationship between the production of aflatoxin and ethylene by the organism may indicate the involvement of the latter in the regulation of aflatoxin biogenesis. 相似文献
80.
In vivo recombinant interleukin 2 administration enhances survival against a lethal challenge with Toxoplasma gondii 总被引:22,自引:0,他引:22
S D Sharma J M Hofflin J S Remington 《Journal of immunology (Baltimore, Md. : 1950)》1985,135(6):4160-4163
Administration of recombinant interleukin 2 (rIL 2) resulted in a significant (p less than 0.01) decrease in mortality in mice infected with a dose of Toxoplasma gondii that killed 100% of untreated mice. Mice treated with rIL 2 had a significantly (less than 0.005) lower numbers of cysts in the brains. The protection afforded by rIL 2 could not be correlated with increased antibody synthesis or be explained by increased macrophage killing in the treated mice. Mice treated with rIL 2 after Toxoplasma infection demonstrated increased natural killer (NK) cell activity compared with either Toxoplasma-infected or rIL 2-treated mice. rIL 2 failed to reverse the suppressed proliferative response of lymphocytes to concanavalin A and lipopolysaccharide in mice acutely infected with a virulent strain of T. gondii. These results reveal that rIL 2 may have a remarkably protective effect against intracellular parasites. 相似文献